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Invasive and Non-native Aquatic Invertebrates in the Lower Coos Watershed

    Summary:

  • Over 60 non-native aquatic invertebrate species have been identified in the project area, but for most, little information is available about their population status, distribution, or local impacts.


  • Future invasions of non-native invertebrate species are likely to occur, facilitated by international and domestic shipping, new aquaculture ventures, and climate change.


  • Significant damage has been documented in the project area caused by invasive invertebrate species (e.g. burrowing and parasitic isopods).


Figure 1: Invasive and
non-native invertebrate
study areas.

Section 1. Established Non-Native Species
with Known Impacts (Table 1)

Biofoulers (sponges, hydroids, anemones,
tube-building amphipods, bryozoans, and
sea squirts)

Blackfordia virginica
Hydroid (no common name)

This hydroid is native to the Black and Caspian
Seas, but has successfully invaded European
waters, the western Atlantic Ocean, India and
China. It was first collected in the 1970s on
the Pacific Coast in the San Francisco estuary,
(originally misidentified/correctly identified in
early 1990s)(Cohen and Carlton 1995). It was
later collected in the Coos estuary in 1997
and reported to be abundant by July 1999
(Carlton 2000). It was likely introduced on
ship hulls as a fouling organism and through
ballast water (Cohen and Carlton 1995).

Botrylloides violaceus

Orange sheath sea squirt

This sea squirt is considered native to Japan,
although difficulty in species identification
(and uncertainty of species status) has complicated
the delineation of accurate native
and introduced ranges for species in the
genus. However, it’s fairly well agreed that it
was not found north of Southern California until the 1940s and 1950s (Cohen and Carlton
1995).

In a 1988-1990 survey, Hewitt (1993)
found B. violaceus in South Slough, as well as
at sites in the middle and upper Coos estuary
(Figure 2)(Table 2). During this two year study
recruitment of B. violaceus peaked from June
to September, but extended into November
during one year. Hewitt (1993) also tracked
the transport of B. violaceus on a floating
dock from Joe Ney Slough (part of South
Slough) to Isthmus Slough in June of 1990. By
September 1990, the total percent coverage
of B. violaceus on the transplanted dock had
grown to 60%. Recruitment of B. violaceus to
areas adjacent to the dock was also observed
and by September 1990, 20% of the adjacent
encrusting communities consisted of colonies
of this sea squirt. Hewitt (1993) reports the
coverage of B. violaceus in Isthmus Slough
declined in subsequent years to 5-10%, but it
had also spread seaward from the upper bay
at a rate of 2 km/yr from 1991-1993 to Pony
Slough in the middle bay (Figure 2). A decade
later, surveys of non-native fouling communities
showed B. violaceus was present in 2003
at the Charleston Boat Basin Marina, Empire
Pier, and near Valino Island in South Slough
(Figure 3)(de Rivera et al. 2005). It was also
found the following year at the Port of Coos
Bay Citrus Dock in the upper Coos estuary (de
Rivera et al. 2005).

Table 1: Non-native aquatic invertebrates established in the project area that have documented threats to habitat/native species (salmon icon at column head) and/or the local economy (dollar sign icon). Detection date indicates the first known date of project area invasion. Project area subsystem codes (see also Figure 1): CR- Coos River; CS- Catching Slough; HI- Haynes Inlet; IS- Isthmus Slough; LB- Lower Bay; NS- North Slough; PS- Pony Slough; SS- South Slough; UB- Upper Bay* SH = Southern Hemisphere; WP = West Pacific (e.g., China, Japan); UNK = unknown; PC = Ponto-Caspian; NA = North Atlantic;EA = East Atlantic (e.g., Europe north of Spain); WA = West Atlantic.** BW = ballast water; SF = ship fouling; CO = commercial oyster culture; IP = intentional plantings;UNK = unknown.


Table 1 (continued): Non-native aquatic invertebrates established in the project area that have documented threats to habitat/native species (salmon icon at column head) and/or the local economy (dollar sign icon). Detection date indicates the first known date of project area invasion. Project area subsystem codes (see also Figure 1): CR- Coos River; CS- Catching Slough; HI- Haynes Inlet; IS- Isthmus Slough; LB- Lower Bay; NS- North Slough; PS- Pony Slough; SS- South Slough; UB- Upper Bay* SH = Southern Hemisphere; WP = West Pacific (e.g., China, Japan); UNK = unknown; PC = Ponto-Caspian; NA = North Atlantic;EA = East Atlantic (e.g., Europe north of Spain); WA = West Atlantic.** BW = ballast water; SF = ship fouling; CO = commercial oyster culture; IP = intentional plantings; UNK = unknown.


Figure 2: Locations of Hewitt’s (1993) study sites (points on map) where he investigated populations of invasive/non-native encrusting organisms. Distinct regions were delineated based on Hewitt’s study, and based on similarities of sample sites. Region delineation should not be confused with similarly named project area regions commonly used in this and other chapters.The red squares with callouts on map and adjoining table show the secondary dispersal (within the Coos estuary) of the colonial sea squirt Botrylloides violaceus. *Although originally found in South Slough (site 1 on map), it was manually moved to Isthmus Slough (site 2) and dispersal distances were calculated from that point. Data Source: Hewitt 1993.

Table 2: Invasive aquatic invertebrates recruited into the lower Coos and Isthmus Slough between 1988-1990. Data: Source Hewitt 1993

What’s happening?

This data summary provides information
about the 62 known non-native aquatic invertebrate
species that have become established
in the lower Coos watershed (project area), as
well as nine high risk aquatic non-native species
that are not currently in the project area
but predicted to arrive here in the future.

This summary is divided into five sections:
1) Established Non-Native Species With
Known Impacts –
status of non-native
species established in the project area
that have documented local impacts or
known impacts in nearby invaded areas.

2) Established Non-Native Species With
Unknown Impacts –
status of non-native
species established in the project area for
which no impacts have been studied or
documented.

3) Predicted Threats – status of non-native
species that are likely to arrive in the project
area based on geographic proximity,
available vectors, and invasion trends of
the species.

4) Threats to Human Health – describes the
human health threats posed by several
species.

5) Background on Species with Known
Impacts –
describes ecological/economic
impacts that have been documented for
the 29 Established Non-Native Species
With Known Impacts. In cases where no
information exists for local impacts, information
from nearby areas is included.

Tables summarizing the species discussed
begin each section (Tables 1, 3 and 4). In each
section (and table) the species are organized
alphabetically by scientific name within the
general groupings of: biofoulers (sponges,
hydroids, anemones, bryozoans, barnacles
and sea squirts), molluscs (snails, clams, mussels,
and oysters), crustaceans (crabs, shrimp,
isopods, and amphipods), and worms.

The individual summaries describe what’s
known about species’ introductions to the
project area and current distribution (where
available). Information included in this
summary is based on two comprehensive
published lists (Ruiz et al. 2000, Wonham and
Carlton 2005), as well as data collected from
more recent surveys. However, very little information
exists about any particular species’
spatial distribution and presence from year to
year.

Species are included in Predicted Threats
(Section 3) if they’re established in nearby estuaries
and have a high likelihood of becoming
introduced to the project area (see “Major
Vectors of Invasion” textbox below).

Each species listed in Section 1 (species established
in the project area with known impacts)
is symbolized within a yellow icon and
symbol based on the type of threat they pose.

Threats to native species and habitats are
denoted with a fish icon. Economic threats
(e.g. to industry, infrastructure, fisheries, etc.)
are denoted with a dollar sign. Species that
are predicted threats (Section 3) are similarly
symbolized, within a red icon (see example
below).

Symbol showing high environmental
and economic threat
for a species that is a predicted
threat (red).


Symbol showing high environmental
and economic threat for
an established species that has
known impacts (yellow).

Terms Used in This Chapter


Species Origin
Native: naturally occurs in an area without
human facilitation; evolutionarily connected
to an area

Non-native: plants or animals introduced
either intentionally or accidentally to locations
outside their native ranges

Invasive: non-native species that aggressively
outcompete native species, causing
significant economic loss and/or environmental
harm. Not all non-native species
are invasive.

Population Status
Established: self-maintaining populations
Not established: reported in an area, but
does not have a self-maintaining population

Unknown: insufficient spatial or temporal
information available to classify status

Predicted: established in nearby locations
and likely to be introduced to Coos estuary


Botryllus schlosseri

Golden star sea squirt

As with B. violaceus, the native range and
introduction history of this sea squirt are
ambiguous, but it is presumed to be a native
of European waters. Hewitt (1993) found colonies
of B. schlosseri in South Slough during
monthly surveys from September 1988 to
September 1990 (Figure 2)(Table 2). In June of
1990, colonies of B. schlosseri were transported
to Isthmus Slough from South Slough (at
Joe Ney Slough) on a floating dock. Although
the colonies survived their initial relocation,
by September 1990 coverage of the transplanted
dock by B. schlosseri colonies had
reduced to 5%. During a 2003-2004 survey
of fouling communities in the estuary, B.
schlosseri
was only found at one location (the
Charleston Boat Basin Marina) in 2003 (Figure
3)(de Rivera et al. 2005). It was not present at
any sites in 2004, but the Charleston Marina
was not sampled that year. B. schlosseri has
most likely spread throughout its introduced
range by ship hull fouling and with oyster
shipments from the Atlantic and Asia (Hewitt
1993).

Bugula neritina

Spiral-tufted bushy bryozoan

This species is found all over the world. Along
the Pacific Coast of North America, the native
range of B. neritina extends from Monterey
Bay to the south (Cohen and Carlton 1995). In
the 1980s it was reported in the San Francisco
estuary and continued to extend its range
north into the 1990s (Cohen and Carlton
1995).

It was first reported in the Coos estuary
by Hewitt (1993) where it was found in
South Slough (Figure 2). Throughout its range,
B. neritina is commonly found in fouling communities
and was likely dispersed to new locations
on ship hull fouling communities since
its planktonic larval stage is relatively brief.

Cliona sp.

Boring sponges

The native ranges of boring sponges in this
genus are not entirely known, but several
species are thought to naturally occur in the
western Atlantic where they grow on Atlantic
oysters. The first record of Cliona sp. from the
San Francisco estuary is from 1893, after they
were likely transported to the Pacific Coast
with oyster shipments (Cohen and Carlton
1995). Cliona sp. is listed as established in the
Coos estuary in Ruiz et al. (2000).

Cordylophora caspia

Freshwater hydroid

Found by Hewitt (1993) in the upper bay
and in the Coos River (Figure 2). The species
is thought to have been introduced on ship
hulls as a fouling organism and through the
transport of oysters to the area from both
the western Pacific and the Atlantic Ocean
(Hewitt 1993).

Didemnum vexillum

Carpet sea squirt

This species was first recorded in Oregon in
the Umpqua Triangle in 2010 and later that
year in the Charleston Boat Basin. Surveys
from 2010 to 2013 reported new colonies
in the Charleston Boat Basin in 2012-2013,
but it hasn’t been reported elsewhere in the
Coos estuary. D. vexillum grows rapidly and
reproduces by fragmentation and planktonic
larvae. It was likely introduced from fouling
communities on ship hulls, or the presence
of small colonial fragments in ballast water.
D. vexillum requires salinities greater than 25
(Daley and Scavia 2008), which suggests it will
likely be restricted to the lower portions of
the Coos estuary. It can survive temperatures
ranging from 2 to 25°C and daily fluctuations
as large as 11°C (Valentine et al. 2007). Colonies
of this D. vexillum produce acidic components
that successfully deter predators and
facilitate its ability to become established. It is
on the Oregon Invasive Species Council list of
100 worst invasive species. (OISC 2013).

Diplosoma listerianum (also reported as
Diplosoma mitsakurii)

Colonial sea squirt (no common name)

Native to Japan, this sea squirt was likely introduced
to the Coos estuary through ballast
water of shipping vessels along the Pacific
coast of the US. Hewitt (1993) reports this
species was absent from surveyed sites in
1988-1991, but it was present in the summer
of 1992 in Isthmus Slough (Figure 2)(Table
2). Identification of the species was aided by
a survey that detected sea squirt “tadpole”
larvae in ballast water from Japanese ships
entering the Coos estuary in the summer of
1992 (Carlton and Geller 1993). This species
was not found at later survey dates by Hewitt
(September and November 1992 or February
and April 1993), therefore it appears the invasion
was not successful.

Ectopleura crocea (also reported as Tubularia
crocea
)

Pink-mouthed hydroid

Native to the northwestern Atlantic Ocean,
this hydroid was likely introduced to the
Pacific on ship hulls as a fouling organism and
in shipments of Atlantic and Japanese oysters.
There are several published reports of this
species in the Coos estuary, with the earliest
from 1948 (referenced in Carlton 1979). It
was later reported in Coos Bay in 1987 on the
wooden hull of a ship leaving the estuary, but
not on the ship when it arrived from Yaquina
Bay (Carlton and Hodder 1995). It was
found in upper Coos Bay in the early 1990s
by Hewitt (1993)(Figure 2, Table 2). E. crocea
was also found, along with the non-native E.
dumortierii
, in 2004 at the Port of Coos Bay
Citrus Dock in the upper Coos estuary, but
neither species was found at 2003 survey locations
or any other locations in 2004 (Figure
3)(de Rivera et al. 2005).

Molgula manhattensis

Sea grapes

Native to the North Atlantic, this sea squirt
was first reported on the Pacific Coast of the
US in 1949 in Tomales Bay, California, and
found throughout the San Francisco estuary
in the 1950s. By 1974 it had extended north
to Coos Bay (Cohen and Carlton 1995). The
species is tolerant of low salinities so it’s
often found in upper reaches of estuaries.
In California, M. manhattensis is known to
survive periods of low salinity due to high
levels of freshwater input (Cohen and Carlton
1995). Hewitt (1993) found this species in
South Slough and in the upper Coos estuary
(Figure 2)(Table 2). It is often found attached
to oyster shells, so it’s possible it originally
spread with oyster shipments from the
Atlantic Ocean in the 1940s, as well as in ship
fouling communities (Hewitt 1993, Cohen
and Carlton 1995). It was found on the hull
of a wooden ship leaving Coos Bay in 1987
(Carlton and Hodder 1995). In 2015 and 2016,
high densities of these sea squirts were found
in the upper Coos estuary at Coalbank Slough
(B. Yednock pers. comm. 2016).

Monocorophium acherusicum (also reported
as Corophium acherusicum)

Amphipod (no common name)

Native to the North Atlantic, the first specimen
of this species from the Coos estuary
was collected in 1905 with oyster shells of the
Atlantic oyster (Crassostrea virginica). This
account, as well as a second one from 1942,
is reported by Carlton (1979; reported as
Corophium acherusicum). It’s listed as an established
species in the Coos estuary by Ruiz
et al. (2000) and Wonham and Carlton (2005)
and is known to be common in fouling communities
in the Charleston Boat Basin Marina
and the Empire Docks. The species likely
arrived to the region on fouled ship hulls and
in oyster shipments from the Atlantic Ocean.

Styela clava

Club sea squirt

This sea squirt was first reported in the Coos
estuary in 1993-94, presumably introduced
from Europe, although it’s been present in
California since the 1930s (Cohen and Carlton
1995). S. clava is not reported anywhere else
in Oregon. Likely vectors for its invasion include
Pacific oyster shipments, ballast water,
and hull fouling (Cohen and Carlton 1995;
Ruiz et al. 2000). This species is often found
attached to artificial structures (e.g. pilings,
floats, docks, boat hulls, aquaculture gear)
in relatively shallow waters ranging from
11-27°C and salinities between 22-36. Adults
cannot survive salinities less than 10.

Watersipora subtorquata (also reported as
W. edmonsonii)

Bryozoan (no common name)

The native range of this species is unknown,
and difficulty in the identification of this
species and others in the genus has led to an
uncertain introduction history. Representatives
of the genus were first seen in Southern
California in the 1960s. Specimens identified
as W. subtorquata were found in the Coos
estuary in the early 1990s, as well as in 1998
(Carlton 2000), with the most likely mode of
transport being fouling communities on ship
hulls.

Another representative of this difficult to
identify genus, W. edmonsonii(?)(uncertainty
indicated by the question mark) was reported
by Hewitt (1993). It was collected in South
Slough in 1990. Hewitt suggested it was likely
introduced from southern California through
modern mechanisms, such as ballast water or
mariculture transport. He reports the species
comprised ~5% of the encrusting community
at the Charleston Boat Basin Marina in 1990
(Figure 2). Later surveys showed its percent
coverage declined to <1% (Hewitt 1993).

Crustaceans (crabs, shrimp, amphipods,
isopods)

Ampithoe valida

Amphipod (no common name)

Native to the northwestern Atlantic Ocean,
this species was first collected in the early
1940s in the San Francisco and Tomales
estuaries. It was found in the Coos estuary in
1950, then again on the hull of a wooden ship
leaving Coos Bay in 1987 (Carlton and Hodder
1995; Carlton 1979). This species lives in eelgrass
beds, on algae, and in oyster beds in the
Atlantic Ocean, therefore it is possible it was
introduced earlier in the 1900s to San Francisco
via oyster shipments from the Atlantic and
remained undetected until the 1940s. It was
likely also transported in ballast water and by
ship fouling (Cohen and Carlton 1995).

Caprella mutica

Japanese skeleton shrimp

This species, native to the Sea of Japan, was
first collected in the 1970s in California in the
San Francisco estuary, Elkhorn Slough, and
the Humboldt estuary. It wasn’t collected
in the Coos estuary until 1983 (Cohen and
Carlton 1995). C. mutica was possibly brought
to the US Pacific Coast with shipments of
Japanese oysters (Cohen and Carlton 1995),
but it is also known to survive in ships’ ballast
water (Carlton 1985). In locations where they
become established, these skeleton shrimp
can become quite abundant.

Carcinus maenas

European green crab

This species is native to the eastern Atlantic
Ocean from Africa to Norway and Iceland,
but it has been a successful invader along the
northeastern coast of North America (in the
US and Canada), the southern hemisphere,
and the US Pacific Coast. It was first seen
on the US Pacific Coast in the San Francisco
estuary in 1989. Genetic evidence links that
introduction to populations from the Atlantic
Coast (Darling et al. 2008). Large numbers
of juvenile green crabs were later found
recruiting to Oregon estuaries in 1997/1998
(including the Coos estuary) from late-August
to early October, following a very strong El
Niño year when northward flowing currents
presumably facilitated the dispersal of larvae
north from California (Yamada and Gillespie
2008)(see Invasive and Non-native Species
Climate Change Summary). Recruitment of
juvenile green crabs in the Coos estuary was
studied from 1997 through 2006 by Yamada
and Gillespie (2008). Juvenile green crabs
were observed every year, although abundance
varied considerably; only four were
collected in 2005 compared to 65 in 1998.
Higher numbers were found to be linked to
warmer winters (Yamada and Gillespie 2008).
C. maenas appears to be restricted to lower
salinities in Oregon estuaries due to predation
pressure by native crabs (Hunt and Yamada
2003). As recently as 2017, juvenile and adult
C. maenas have been collected throughout
South Slough (B. Yednock pers. comm. 2016).

Jassa marmorata

Amphipod (no common name)

Native to the Atlantic Ocean, this species
has been collected along the Pacific Coast of
North America in Alaska, British Columbia,
and from Coos Bay south to Mexico (Cohen
and Carlton 1995). It was first collected in the
Coos estuary in 1954 (referenced in Carlton
1979). This species lives in fouling communities
often found on ship hulls and with oysters,
and was found in ballast tanks entering
the Coos estuary from Japan (having survived
a 15 day voyage)(Cohen and Carlton 1995).
Specimens were also found on the wooden
hull of a ship that arrived to Coos Bay in 1987
from Yaquina Bay (Carlton and Hodder 1995).

Limnoria tripunctata

Gribble, wood boring isopod

The native range of this small wood-boring
isopod is unknown, but the first records of
its appearance on the Pacific Coast are from
the 1870s (referenced in Cohen and Carlton
1995). It was likely introduced to the region
with the arrival of wooden-hulled ships and
quickly became established in wood pilings
and docks. L. tripunctata was found on a
wooden ship traveling from Yaquina Bay to
Coos Bay in 1987 and present throughout the
remainder of the journey to the Humboldt
and San Francisco estuaries (Carlton and
Hodder 1995).

Orthione griffenis

Bopyrid isopod parasite

This species is was first documented in 1988
on the US west coast in Willapa Bay where
it was collected with the native mud shrimp
Upogebia pugettensis (Dumbauld et al. 2011).
It was later found in the Coos estuary in 1997
and in the Yaquina estuary in 1999 (Markham
2005, Chapman et al. 2012). Larvae were
likely introduced and spread through shipping
activity via ballast water (Chapman et
al. 2012). O. griffenis is now well established
along the US west coast in mud shrimp populations
from Canada to Mexico (Chapman et
al. 2012).

Palaemon macrodactylus

Migrant prawn

Native to the western Pacific, this species first
arrived in the eastern Pacific in the 1950s in
the San Francisco estuary (Cohen and Carlton
1995). It most likely arrived in ballast water
or in the fouled sea water system of ships
traveling to the area from Asia (Cohen and
Carlton 1995). P. macrodactylus spread north
and south from the San Francisco Bay Area in
the 1970s and was first collected in the Coos
estuary in 1986 (Cohen and Carlton 1995).
Tolerant of a wide variety of environmental
conditions, this species can be found in near
fresh water (1-2) and in areas of low water
quality.

Pseudodiaptomus inopinus

Asian calanoid copepod

This Asian copepod was first reported in the
Pacific Northwest in the Columbia River in
1990 where, based on abundance, it had
already become well-established (Cordell
et al. 1992). Because this species spends
its entire life cycle in the plankton, it was
likely introduced to the Columbia River in
ballast water of shipping vessels. In a survey
of Pacific Northwest estuaries from British
Columbia to Oregon, P. inopinuswas found
in samples collected from the Coos River in
September and October of 1991 (Cordell and
Morrison 1996). Although barnacle, bivalve,
and brachyuran crab larvae dominated these
plankton samples, P. inopinus comprised
10.2% of numerical abundance in the Coos
River samples, compared to a maximum of
28.9% in the Yaquina River and minimum of
0 in the Chehalis River (Washington)(Cordell
and Morrison 1996).

Rhithropanopeus harrisii

Harris mud crab

Native to the Atlantic Ocean, this species was
first documented along the Pacific Coast in
the Oakland estuary in 1937, possibly having
arrived with shipments of Atlantic oysters. In
Oregon, it was first found in the Coos estuary
in 1950, then later found in the Netarts estuary
in 1976 and in the Yaquina and Umpqua
estuaries in 1978 (Cohen and Carlton 1995).
Its northward range expansion was presumably
facilitated by periodic El Niño-Southern
Oscillation events when northward flowing
currents are strongest (Petersen 2006)(see
Invasive and Non-native Species Climate
Change Summary). R. harrisii is often found in
low salinity waters and, in the Coos estuary,
is also largely restricted to the upper reaches
of the estuary by the presence of the native
bay shore crab (Hemigrapsus oregonensis),
a direct competitor found in the middle and
lower reaches of the estuary (Jordan 1989).

Sphaeroma quoianum

New Zealand burrowing isopod

Native to Australia (esp. Tasmania) and New
Zealand, this isopod was first reported in
the northeastern Pacific in the San Francisco
estuary in 1893. It spread throughout California
from the 1920s to the 1950s and was
first found in the Coos estuary in 1995 on
floating docks in Isthmus Slough (Cohen and
Carlton 1995). The species is highly abundant
throughout the Coos estuary where suitable
substrate exists (Figure 4)(Davidson 2006 and
2008).

Molluscs (snails, clams, mussels, oysters)

Corbicula fluminea

Asiatic clam, golden clam

Native to tropical SE Asia, this clam was originally
introduced to the US as a food source
by Chinese immigrants and more recently
may have been unintentionally introduced to
new areas with Pacific oyster and bait imports
(Foster 2015). It was first reported in Oregon
in 1948 in the Columbia River and has since
been found in the John Day, Smith, Siuslaw,
and Willamette Rivers (Foster 2015). Listed as
an established species in Coos Bay by Ruiz et
al. (2000), no additional published accounts
of the species in Coos Bay could be found.

Crassostrea gigas

Pacific oyster

Native to Japan, these oysters were intentionally
introduced for commercial oyster production
around the world and are extensively cultivated
along the US Pacific Coast, including the Coos
estuary. Oysters were transported from Japan
to Washington as early as 1875 and to Oregon
in the early 1900s (Carlton 1979). Commercial
aquaculture operations in Coos estuary
are located in South Slough, Haynes Inlet, and
the upper Coos estuary. Small numbers of live
Japanese oysters have been observed outside of
these aquaculture areas. Hewitt (1993) found C.
gigas
recruits in South Slough and at sites in the middle and upper Coos estuary. Rimler (2014)
also observed recruits of C. gigas on settlement
plates in the Coos estuary in August of
2012.

Mya arenaria

Softshell clam

The softshell clam is native to the north
Pacific (from Alaska to the Aleutian Peninsula)
and along the Atlantic Coast of the US.
Because they grow fairly large and are edible,
softshell clams were intentionally introduced
to Coos Bay and other locations along the
Pacific Coast of the US by 1880 (Carlton
1979). Although they have failed to become
established at other introduction sites in
the Pacific, they are commonly found today
throughout Coos Bay, including in the higher
reaches of the estuary (as far as 30 miles from
the ocean)(ODFW 2014). Softshell clams are
popular among recreational and commercial
clammers.

Philine auriformis

New Zealand sea slug

This sea slug is native to New Zealand, but has
colonized the US Pacific Coast. It’s become
established in the Coos estuary (Ruiz et al.
2000, Wonham and Carlton 2005) and is on
the Oregon Invasive Species Council’s 100
Worst Invaders List (OISC 2013). Its status in
Oregon, however, is considered contained.

Potamopyrgus antipodarum

New Zealand mud snail

This snail is native to New Zealand, but is a
known invader across the globe. It was first
discovered in the Coos estuary in 2006, likely
introduced by ballast water or with fishing
gear. Its small size (5-6 mm) and ability to
thrive in fresh and brackish water makes it
an easy species to spread accidentally via
recreational fishing and boating. P. antipodarum
has been found in several estuaries
and rivers along the Oregon Coast, from the
Columbia River to the Rogue River (Davidson
et al. 2008a).

Teredo navalis

Naval shipworm

The native range of this wood-boring bivalve
is not known, but it is considered to be an introduced
species to the US Pacific Coast, with
its earliest documented occurrence (1913)
in the San Francisco estuary (Carlton 1979).
The first reports of the T. navalis in the Coos
estuary are from 1988 (Fofonoff et al. 2003).
Nearly a century earlier, a report from the
United States War Department describes infestations
of T. navalis in the lower Coos estuary
(USWD 1879). However, since T. navalis is
found only in the upper portions of estuaries,
it’s more likely the species described in the
1879 report was the native shipworm, Bankia
setacea
(J. Carlton pers. comm. 2015).

Major Invasion Vectors


Hard Ballast – Beginning in the 16th century
the transport of hard ballast on ships
(e.g., river cobble) resulted in the earliest
invasions of aquatic organisms.

Ballast Water – The use of water for ships’
ballast can transport invertebrate larvae,
viable fragments of sessile organisms, and
small aquatic species between estuaries.

Ship fouling – As early as the 16th century,
fouling aquatic species have been
transported on the hulls of ships. This
remains a particularly effective vector for
introductions of aquatic invertebrates to
new areas.

Shellfish imports – Historic shipments of
Atlantic oyster (Crassostrea virginica) from
the US east coast to the west coast transported
aquatic species on oyster shells.
Similarly, historic imports of Pacific oyster
(Crassostrea gigas) from Japan transported
many Asian aquatic species to the US.
Commercial oyster shipments between
estuaries continue to move organisms.

Intentional Introductions – Intentional
seeding of non-native molluscs (e.g. Manila
clams (Vererupis philippinarum)) has
occurred along the Oregon Coast.

Tsunami Debris/Storms – Events like the
2011 Japanese tsunami and storms transport
aquatic species-carrying debris across
oceans.

Climate change – Predicted changes in
ocean conditions (e.g., temperature increases)
will expand aquatic species ranges,
facilitating the movement of non-native
species from California to Oregon.


Table 3 (continued on next page): Non-native aquatic invertebrates established in the project area that are not documented threats to habitat/native species or the local economy. Detection date indicates the first known date of project area invasion. Project area subsystem codes (see also Figure 1): CR- Coos River; CS- Catching Slough; HI- Haynes Inlet; IS- Isthmus Slough; LB- Lower Bay; NS- North Slough; PS- Pony Slough; SS- South Slough; UB- Upper Bay
* SH = Southern Hemisphere; WP = West Pacific (e.g., China, Japan); UNK = unknown; NA = North Atlantic; EA = East Atlantic (e.g., Europe north of Spain); WA = West Atlantic.
** BW = ballast water; DB = dry ballast; SF = ship fouling; CO = commercial oyster culture; UNK = unknown.


Table 3 (continued): Non-native aquatic invertebrates established in the project area that are not documented threats to habitat/native species or the local economy. Detection date indicates the first known date of project area invasion. Project area subsystem codes (see also Figure 1): CR- Coos River; CS- Catching Slough; HI- Haynes Inlet; IS- Isthmus Slough; LB- Lower Bay; NS- North Slough; PS- Pony Slough; SS- South Slough; UB- Upper Bay
* SH = Southern Hemisphere; WP = West Pacific (e.g., China, Japan); UNK = unknown; NA = North Atlantic; EA = East Atlantic (e.g., Europe north of Spain); WA = West Atlantic.
** BW = ballast water; DB = dry ballast; SF = ship fouling; CO = commercial oyster culture; UNK = unknown.

Molluscs (snails, clams, mussels, oysters)

Assiminea parasitologica

Asian marsh snail
Several populations of A. parasitologica were
first documented in the upper reaches of
the Coos estuary in 2007. This was the first
known occurrence of the species in North
America and it was assumed that it was introduced
to the area from the ballast water of
commercial ships from Asia. During a survey
of Oregon and Washington in 2008, this snail
was also found in the Umpqua and Yaquina
estuaries and was assumed to have been
accidentally transferred to these systems by
humans (e.g. recreational fishing, boating, scientific
field sampling)(Laferriere et al. 2010).

A systematic survey of Coos Bay in 2009
found A. parasitologica to be the most abundant
snail in Isthmus Slough, Coos River and
Haynes Inlet (west), and one of the two most
abundant snails in Kentuck Inlet, Haynes Inlet
(east), and South Slough (Figure 5)(Laferriere
et al. 2010). In addition to the Coos estuary,
ten other estuaries in the Pacific Northwest
were surveyed in 2009, and A. parasitologica
was found in the Coquille, Umpqua, Alsea,
and Newport systems. It was absent in Willapa,
Columbia, Nehalem, Tillamook, Lincoln
City, and Siuslaw.

Figure 5: Relative abundance and distribution of the invasive Asian marsh snail Assiminea parasitologica from 2009 surveys. Data Source: Laferriere et al. 2010


Figure 6: Relative abundance and distribution of the invasive mouse ear snail Myosotella myosotis (also known as Ovatella myosotis) from 1991 surveys. Data Source: Laferriere et al. 2010

Figure 3: Deployment locations of settlement plates where invasive aquatic invertebrates were found (2003 and 2004). Plates were deployed on pilings and on marina docks. Species recovered at each location are shown. Data Source: de Rivera et al. 2005

Section 2. Established Non-Native Species
with Unknown Threats (Table 3)

Biofoulers (sponges, hydroids, anemones,
bryozoans, and sea squirts)

Amphibalanus improvisus (also reported as
Balanus improvisus)

Bay barnacle
Native to the North Atlantic Ocean, the first
A. improvisus specimen found on the Pacific
Coast was collected in the San Francisco
estuary in 1853 and was likely introduced as
a fouling organism on ship hulls. Later, from
the 1900s to the 1960s, shipments of Atlantic
oysters to the Pacific resulted in many more
Pacific Coast introductions of this species.
It was first reported in the Coos estuary in
1978 (Cohen and Carlton 1995) and is now
commonly found in lower salinity regions of
the upper estuary. Hewitt (1993) found this
species in the middle and upper reaches of
the Coos estuary and in the Coos River (Figure
2)(Table 2). During a survey of non-native
fouling organisms,B. improvisus was found in
2003 at the Charleston Marina, Empire Pier,
and in South Slough in both the Sengstacken
and Winchester arms and near Valino Island
(Figure 3)(de Rivera et al. 2005). In 2004, it
was found again in Winchester arm of South
Slough and at the Port of Coos Bay Citrus
Dock near downtown Coos Bay (de Rivera et
al. 2005).

Barentsia benedeni

No common name
The native range of this colonial invertebrate
is not well characterized, but its first appearance
on the US Pacific Coast occurred in the
San Francisco estuary in 1929. This species
does not have a planktonic larval stage, therefore
it is unlikely to have dispersed to the area
naturally as larvae or in ballast water. It was
most likely introduced to the region on fouled
ship hulls, or as part of the fouling communities
that were inadvertently introduced with
oyster shipments from Japan (Hewitt 1993,
Cohen and Carlton 1995). It’s been collected
in the Coos estuary since 1988, where it was
found in the upper estuary and Coos River
(Figure 2)(Table 2)(Hewitt 1993).

Bowerbankia gracilis

Creeping bryozoan
This species’ presence is reported from all
over the world, but its native range is likely
limited to both hemispheres of the western
Atlantic Ocean. Identification of B. gracilis is
difficult so incorrect identification has likely
complicated accurate delineation of its
native and introduced ranges. B. gracilis has
been found in the Coos estuary since 1970
(Cohen and Carlton 1995, Hewitt 1993) and
other areas of the US Pacific Coast since the
1920s. It was likely introduced with oyster
and bait shipments or fouling communities
on ship hulls. Without a planktonic stage in its
life cycle, B. gracilis is not likely to spread by
ballast water. Hewitt (1993) found this species
throughout Coos estuary (lower, middle,
and upper bay sites), South Slough, and the
Coos River (Figure 2)(Table 2). Recruitment is
highest for this species from March through
August, with a notable peak in July (Hewitt
1993).

Conopeum seurati

Bryozoan (no common name)
This species was found in the Coos estuary
in 2003 on settlement plates deployed in
the Charleston Boat Basin Marina and at the
Empire Pier as part of a broad-scale survey of
non-native species on the US West Coast (Figure
3)(de Rivera et al. 2005). It was not found
the following year in 2004 at the Empire Pier;
the Charleston Boat Basin Marina site was not
sampled for a second year. C. seurati was not
found in any other surveyed locations in the
Coos estuary in 2003 and 2004. Its presence
at two locations in 2003 may have been an
isolated event.

Conopeum tenuissimum

Lacy crust bryozoan
Native to the Atlantic and Gulf of Mexico
Coasts of North America, this bryozoan was
first reported on the Pacific Coast in the early
1950s in the San Francisco estuary (Carlton
1979) and has been collected in the Coos
estuary since 1970 (Cohen and Carlton 1995).
Likely modes of introduction include ballast
water, fouling communities on ship hulls, and/
or shipments of Atlantic oysters to the West
Coast (Cohen and Carlton 1995). It was found
on the hull of a ship leaving Coos Bay in 1987
(Carlton and Hodder 1995) and collected at
every location surveyed by Hewitt (1993)
from 1988-1990 (Figure 2)(Table 2). Surveys
included South Slough, the lower, middle, and
upper Coos estuary, and the Coos River. Peak
recruitment for this species occurs from June
to September, but can continue later in the
year (Hewitt 1993). This species was observed
in 2003 on settlement plates at Empire Pier
during a survey of fouling communities, but
it was not present at any other locations surveyed
in 2003 or in 2004 (Figure 3)(de Rivera
et al. 2005).

Cryptosula pallasiana

Bryozoan (no common name)
Native to the North and Western Atlantic,
this species appeared throughout the western
and northern Pacific from the 1950s to
the 1970s (Cohen and Carlton 1995). It was
first reported in the Coos estuary in 1988,
where it was found in South Slough and the
Lower Coos estuary (Figure 2)(Hewitt 1993).
The planktonic life stage of this species is
short, therefore it was likely spread by ship
hulls’ fouling communities or on Atlantic and
Japanese oysters (Hewitt 1993), on which it’s
usually found in the Atlantic (Cohen and Carlton
1995). Recruitment in the Coos estuary
appears to be extended throughout the year
from around March to November, with peaks
observed in July and September (Hewitt
1993). C. pallasiana was collected in 2003
from settlement plates at the Charleston Boat
Basin Marina during a survey of non-native
species (Figure 3)(de Rivera et al. 2005). It
was not collected at any other site in the
estuary in 2003 or 2004 (however, the marina
was not sampled in 2004).

Diadumene leucolena

White Anemone
This anemone has been abundant in the
Oakland estuary (California) since the 19th
century, where it is common among fouling
communities and on oyster shells (Cohen
and Carlton 1995). It may have arrived in the Pacific from its native range along the Atlantic
Coast of the US via ballast water, as a fouling
organism, or with oyster shipments (Cohen
and Carlton 1995). Since its arrival to the
Pacific, D. leucolena has since extended its
range north and south from the Oakland and
San Francisco Bay area. It was first reported in
Coos Bay in 1967 (Carlton 1979).

Diadumene lineata (also reported as Haliplanella
lineata
and H. luciae)

Orange-striped sea anemone
First reported in the Coos estuary in 1978
(Carlton 1979) but anecdotal reports indicate
it was found earlier than this first report.
Native to Asia, it was likely introduced to Coos
Bay by ship fouling and through oyster shipments.
Found by Hewitt (1993) in upper Coos
Bay (Figure 2).

Gonothyraea clarki

Hydroid (no common name)
This fouling hydroid is native to the North
Atlantic Ocean. It was first found in the San
Francisco estuary in 1985 and was collected
from floats in Coos Bay in Isthmus Slough in
1995 (Cohen and Carlton 1995).

Halichondria bowerbanki

Deadman’s finger sponge
This sponge was first found on the Pacific
Coast in the 1950s in the San Francisco
estuary (Carlton 1979) and was later found in
Coos Bay surveys conducted from 1988-1990
(Hewitt 1993). It likely spread to the Pacific
from its native range in the Atlantic Ocean
with the importation of Atlantic oysters for
aquaculture, but may also have arrived on
ship hulls as a fouling organism (Hewitt 1993,
Cohen and Carlton 1995). Hewitt (1993) reports
the presence of H. bowerbanki in South
Slough and the upper bay (Figure 2)(Table 2).

Haliclona loosanoffi (also reported asHaliclona
sp.
)

Loosanoff’s Haliclona
Native to the Atlantic Ocean, this sponge
was introduced to the Pacific as early as the
1950s, however difficulty in distinguishing this
species from other Haliclona sponge species
makes it hard to confirm the exact introduction
date. As with H. bowerbanki, it could
have spread from the Atlantic with shipments
of Atlantic oysters and/or as a fouling species
(Hewitt 1993, Cohen and Carlton 1995).
Hewitt (1993) reports a Haliclona species
from the upper Coos estuary, which likely
refers to H. loosanoffi, as well as a possible
native Haliclona species in South Slough and
the lower Coos estuary sites (Figure 2)(Table
2).

Monocorophium insidiosum (also reported
as Corophium insidiosum)

Amphipod (no common name)
The exact date of introduction to the Coos
estuary for this species is unknown, but it
was likely transported to the Pacific Coast
from its native range in the North Atlantic
on ship hulls as a fouling organism and with
shipments of Atlantic oysters. This amphipod
is listed as an established introduced species
in the Coos estuary by Ruiz et al. (2000) and
Wonham and Carlton 2005.

Schizoporella unicornis (also reported as S.
japonica
)

Single horn bryozoan
This bryozoan is native to the western Pacific
and likely transported to the eastern Pacific
on fouled ship hulls and shipments of Japanese
oysters. It was first reported in California
in 1938, in British Columbia in 1966, and in
Oregon (Coos estuary) in 1986 (Cohen and
Carlton 1995). S. unicornis is reported in
Hewitt (1993) from South Slough, presumably
introduced with local cultivation of Japanese
oysters. Recruitment of this species to
sampling locations from 1998 to 1990 was observed
in all months, with a peak from June to
August (Table 2)(Hewitt 1993). Hewitt (1993)
also tracked the transport of this species to
Isthmus Slough from South Slough (at Joe Ney
Slough) on a floating dock that was moved
in June 1990. After 15 days the S. unicornis
colonies on the dock were still alive, but by
September 1990 they had turned white and
were presumed dead. During a survey of
non-native fouling invertebrates, S. unicornis
was collected in 2003 on fouling plates that
had been deployed at the Charleston Boat
Basin Marina, the Empire Pier, and a piling
near Valino Island in South Slough (Figure 3)
(de Rivera et al. 2005). It was not collected at
any other sites the following year, although
the marina was not sampled in 2004.

Triticella sp.

Bryozoan (no common name)
Found by Hewitt (1993) in the upper Coos estuary.
He also identified possible native species
of the same genus in South Slough and
at sites in the lower estuary (Figure 2). The
native range of this species is likely limited
to Japanese waters, and it is thought to have
been introduced by shipments of Japanese
oysters, ballast water, and/or interstate shipping
along the US Pacific Coast (Hewitt 1993).

Crustaceans (crabs, shrimp, amphipods,
isopods)
Eobrolgus spinosus

Amphipod (no common name)
This amphipod species is native to the US
Atlantic Coast, but has been found in isolated
areas on the US Pacific Coast. It’s listed as an
established introduced species in the Coos
estuary by Ruiz et al. (2000), and was found
in South Slough as recently as February 2012
(GISIN 2017).

Grandidierella japonica

Amphipod (no common name)
Native to Japan, this amphipod spread to the
US Pacific Coast in the 1960s and 1970s, likely
with oyster shipments, ship fouling communities
and/or ballast water. It was reported in
the Coos estuary (and collected since) in 1977
(Cohen and Carlton 1995). It’s become established
on the US Pacific Coast and is highly
abundant in several California estuaries.

Iais californica

Isopod (no common name)
This small isopod is often found living attached
to the ventral surface of the introduced
burrowing isopod, Sphaeroma quoianum
(see summary in Section 1). It was first
described on the US Pacific Coast in the San
Francisco estuary in 1904, where it likely arrived on a ship hull with S. quoianum (Cohen
and Carlton 1995). It has since been found
in the Coos estuary on S. quoianum living on
floating docks in Isthmus Slough (Cohen and
Carlton 1995). I. californica has also been
found living on the native isopod, Gnorimosphaeroma
oregonensis
.

Incisocalliope derzhavini (also reported as
Parapleustes derzhavini)

Amphipod (no common name)
This amphipod is thought to originate from
the west Pacific. I. derzhavini was first documented
on the US Pacific Coast in 1904 in
the San Francisco estuary. It spread to other
coastal locations in California in the 1970s,
then to Oregon in the 1980s, arriving in the
Coos estuary in 1986 (Cohen and Carlton
1995). This species was most likely introduced
on ship hull fouling communities. I. derzhavini
can be found in a wide range of salinities
(from 6 to 32) and often grows in high abundances
with hydroids, but rarely on algae
(Cohen and Carlton 1995). Chapman (1988)
found this amphipod in small numbers among
other non-native species (Ampithoe valida,
Corophium acherusicum, Neanthes succinea,
and Limnoria sp. isopods
) on wooden floats
near Citrus Dock in Coos Bay.

Melita nitida

Amphipod (no common name)
Native to the northwestern Atlantic Ocean,
this amphipod was first reported in the Pacific
in the San Francisco estuary in 1938, then
later in British Columbia and California in
the 1970s. It was first collected in Oregon in
1986-87 in Yaquina, Coos, and Alsea estuaries
(Chapman 1988). M. nitida live in salinities
ranging from 0 to 25 and are common in fouling
communities, in the intertidal zone under
rocks and debris, and on mudflats in algae
mats (Chapman 1988). Initial introductions to
the Pacific may have been the result of oyster
shipments from the Atlantic, on ship hulls
among fouling organisms, or the transport
of solid ballast or ballast water (Cohen and
Carlton 1995).

Nippoleucon hinumensis

Asian cumacean shrimp
Native to Japan, this small shrimp was introduced
via ballast water to the northeastern
Pacific Ocean (Cohen and Carlton 1995).
Since 1986, it’s been collected in large densities
in California where it’s often one of the
top three dominant species (Cohen and Carlton
1995). It was first collected in the Coos
estuary in 1979 and in other Oregon estuaries
<10 years later (Umpqua (1983) and Yaquina (1988))(Cohen and Carlton 1995).

Sinelobus stanfordi

Tanaid crustacean
This shrimp-like crustacean is currently found
nearly worldwide, but its native range is unknown.
The first record of the species found
on the US Pacific Coast is from the 1960s in
the San Francisco estuary (described in Cohen
and Carlton 1995), but it is now found along
the entire US Pacific Coast from San Diego to
Canada (Davidson et al. 2007) and is listed as
an established species in the Coos estuary in
Ruiz et al. (2000) and Wonham and Carlton
(2005).

Myosotella myosotis (also reported as
Ovatella myosotis)

Mouse ear snail/salt marsh snail
Found throughout the eastern and western
Atlantic, this snail was first identified in the
San Francisco estuary in 1871 and was likely
introduced to the bay through shipments of
Atlantic oysters (Cohen and Carlton 1995).
Because this species lacks a planktonic larval
phase, its spread would have resulted from
the movement of adults and/or eggs. The
first record of M. myosotis in Coos Bay is from
1969 (referenced in Carlton 1979) and it is
now common in high salt marshes of the bay
(Figure 6)(Berman and Carlton 1991). It is a
euryhaline species, which means it’s found
in estuarine habitats subject to a wide range
of salinities. Work by Berman and Carlton
(1991) shows the abundance and success of
M. myosotis in Coos Bay relates more to the
species’ ability to occupy a semi-terrestrial
environment than its ability to outcompete
native snails for resources.

Nuttallia obscurata

Purple varnish clam
The purple varnish clam is native to the
western Pacific, with its natural range encompassing
Russia, China, and Japan. It was
first found in the Pacific Northwest in 1991 in
Blaine, Washington, most likely introduced in
ballast water from ships entering the Port of
Vancouver. It has since expanded its range to
the north and south and was first reported in
Coos Bay in 2003 (Fofonoff et al. 2003). These
clams have relatively high survivorship in
higher temperatures and lower salinities than
other bivalves along the West Coast, which
may explain their success as invaders to the
region (Siegrist 2010).

Tenellia adspersa

Miniature aeolis
This snail is native to European and Mediterranean
waters, but has spread to the western
Atlantic and to the Pacific including the Coos
estuary (Cohen and Carlton 1995). Although
no date could be found for its introduction
to the Coos estuary, the species most likely
spread from its native range on ships in
ballast water, or possibly its eggs were spread
via attachment to ship fouling communities.
T. adspersa adults and eggs were found on
a vessel leaving Coos Bay in 1987 that were
not on the vessel when it arrived to bay from
Yaquina Bay (Carlton and Hodder 1995). T.
adspersa
is found in a wide range of salinities
and also occurs in freshwater.
Worms

Heteromastus filiformis

Bristle worm
Native to the US Atlantic Coast, but it has
been reported in the North Sea, Mediterranean,
Morocco, South Africa, Persian Gulf,
New Zealand, Japan, and the Bering and
Chukchi Seas (Cohen and Carlton 1995). H.
filiformis
was first collected in the San Francisco
estuary in 1936 (but was likely introduced
earlier and unidentified until the 1930s), at
Vancouver Island, BC in 1962, and in Coos Bay
in 1970 (Cohen and Carlton 1995). In its native
range it co-occurs with oysters, therefore
it likely was introduced with Atlantic oysters
and possibly ballast water (Cohen and Carlton
1995).

Mysta tchangsii (also reported as Eteone sp.)

Polychaete worm (no common name)
This species is native to the Yellow Sea. It is
reported as an established species in Coos
Bay in Ruiz et al. (2000), but no other published
records of its presence in Coos Bay
could be found.

Nereis succinea (also reported as Neanthes
succinea
)

Pile worm
Reported in locations across the globe, but
first collected in Oregon in Netarts Bay in
1976 (Carlton 1979). N. succinea was later
observed in Coos Bay in 1986 (Cohen and
Carlton 1995) and is listed as an established
introduced species in Coos Bay in Ruiz et al.
(2000) and Wonham and Carlton (2005).

Polydora cornuta) (also reported as P. ligni)

Polychaete worm (no common name)
Native to the North Atlantic, this worm was
introduced to the US Pacific coast with shipments
of Atlantic oysters. Although it was
most likely first introduced in the 1870s, it
was first documented on the US west coast
in 1932 in British Columbia (Carlton 1979). It
was likely transported along the Pacific Coast
following additional introductions from the
Atlantic. P. cornuta was first reported in Coos
Bay in 1950 (Carlton 1979) and was found in
Isthmus Slough in the 1970s during a dredging
study (McCauley et al. 1977).

Pseudopolydora kempi

Spinoid worm (no common name)
Native to the western Pacific, this species was
first reported in the eastern Pacific in 1951
at Nanaimo, British Columbia. It was first
reported in Oregon in 1974 at Yaquina Bay,
then at Netarts Bay in 1976 and Coos Bay,
where it was collected from Isthmus Slough,
in 1977 (Carlton 1979, McCauley et al. 1977).
P. kempi has been introduced to locations
with shipments of Pacific oysters (Crassostrea
gigas
), but may have also be transported in
ballast water or on ship hulls among fouling
organisms.

Streblospio benedicti

Polychaete worm (no common name)
This worm is native to the western Atlantic
Ocean and was likely introduced to the Pacific
Coast in the 1870s with Atlantic oyster shipments,
although it remained undetected in
the Pacific until 1932 when it was reported in
the San Francisco estuary (Carlton 1979). The
first record of the species in Coos Bay is from
1977, where it was found in Isthmus Slough
during a dredging study (McCauley et al.
1977). This species, along with the polychaete
mud worm P. cornuta, is highly tolerant of
pollution and is therefore often an indicator
of poor water quality.

Tubificoides brownae

Oligochaete worm (no common name)
This worm is native to the Atlantic Ocean
and considered a cryptogenic species (of
uncertain origin) in the south San Francisco
estuary. However, Cohen and Carlton (1995)
consider it introduced to the Pacific based on
its limited distribution along the Pacific Coast
compared to its broad continuous distribution
on the Atlantic Coast. T. brownae was first reported
in Coos Bay in 1986 (Brinkhurst 1986)
and is now listed as an established introduced
species in Coos Bay in Ruiz et al. (2000) and
Wonham and Carlton (2005). It was likely
introduced to the region by ballast water or
with shipments of commercial oysters (Cohen
and Carlton 1995).

Tubificoides diazi

Oligochaete worm (no common name)
This species has been collected along the
eastern coast of the US, in northern European
waters (Scotland and France), and Australia.
It is thought to also be introduced to the
eastern Pacific Ocean, where it was collected
in the Coos estuary and in British Columbia in
1979 (Brinkhurst 1986). It’s listed as an established
introduced species in Coos Bay in Ruiz
et al. (2000) and Wonham and Carlton (2005),
where it was likely introduced by ballast water
or with shipments of commercial oysters.

Section 3. Predicted Threats (Table 4)

Ciona savignyi

Transparent sea squirt

This sea squirt is native to Japan, but has become
introduced to several locations on the
Pacific Coast of the US. It is currently found
at over 19 locations in Puget Sound, Washington,
and at multiple locations in California.
It grows on docks, pilings, and boat hulls,
making it likely to be transported to Oregon
on ship hull fouling communities.

Megabalanus rosa

Acorn barnacle

This barnacle is native to the northwestern
Pacific Ocean, but has become established
in Australia. It is not known to occur in the
eastern Pacific Ocean, but it is listed as a key
species to watch for on tsunami debris from
Japan (Lam et al. 2013).

Caprella cristibrachium

Skeleton shrimp

Skeleton shrimp specimens were found
washed ashore at Agate Beach, Oregon, on
debris from the 2011 Japanese tsunami. It
is listed as a key species to watch for on the
Oregon Coast (Lam et al. 2013). Little else is
reported on this species as an invader elsewhere
around the world.

Eriocheir sinensis

Chinese mitten crab

Mitten crabs are known to be aggressive invaders
throughout Europe and on both coasts
of the US. However, as of 2008, Chinese mitten
crabs had not been reported in the Coos
estuary and only one adult crab was collected
in the Columbia River – the only specimen
found in Oregon. A risk assessment prepared
by Draheim (2008) declared the Coos estuary
to have a moderate risk of introduction by
this species. Since mitten crabs are catadromous
(i.e., reproduce in brackish waters and
spend the majority of their lives in freshwater),
their distributions are restricted by salinity.
The findings of the risk assessment suggest
the Coos estuary is the only estuary in Oregon
with the appropriate combination of salinity
(~25) and flushing time to allow proper egg
and larval development (Anger 1991, Hanson
and Sytsma 2008), and therefore the only
estuary of concern in Oregon for a mitten
crab invasion. The highest risk pathway for introduction
to the Coos estuary was identified
as ballast water since Coos Bay is an active
international and domestic shipping port and
planktonic mitten crab larvae can survive in
ballast water for extended periods of time.
Mitten crabs are a known host for the Oriental
lung fluke. There is already a large population
of non-native snails (A. parasitologica)
that can carry and transmit the parasite,
making both species a potential vector for a
parasite with high risk to human health (see
Section 4: Threats to Human Health below).

Hemigrapsus sanguineus

Asian/Japanese shore crab

Native to the western Pacific Ocean, this crab
is a known invader to Europe and the East
Coast of the US where it has caused significant
ecological impacts. It is a likely potential
invader to the Oregon Coast on tsunami
debris from Japan (Lam et al. 2013).

Asterias amurensis

Northern Pacific seastar

This seastar is native to the western Pacific
Ocean in Japan, North China, Korea, Russia,
as well as the North Pacific. It’s a known
invader to Australia, Tasmania, and Victoria,
where populations as large as 12 million
were reported within two years of its arrival.
A. amurensis eats a wide range of mussels
and clams, causing significant ecological and
economic damage to introduced areas and
earning it a place on the 100 World’s Worst
Invader List (ISSG 2015). It is listed as a key
species to watch for on tsunami debris arriving
to the Oregon Coast from Japan (Lam et
al. 2013).

Mytilus galloprovincialis

Mediterranean mussel

This cosmopolitan mussel is found throughout
the western Pacific Ocean, Mediterranean
Sea, northern Europe, eastern North America,
Australia, New Zealand, Tasmania, Africa, and
California (Cohen and Carlton 1995). Although
adults of this species have not been reported
in the Coos estuary, genetic research from the
1990s identified large numbers of viable M.
galloprovincialis
larvae in ballast water being
discharged into the Coos estuary from Japanese
ships (Geller et al. 1994). Detection of
M. galloprovincialis will likely be complicated
by its similar appearance to the native mussel
M. trossulus.

Potamocorbula amurensis (also reported as
Corbula amurensis)

Asian clam

This clam is native to the western Pacific
Ocean from southern China to Siberia, Japan
and Korea. It first arrived in the San Francisco
Bay area in 1986 and was presumed to have
been transported by ballast water of shipping
vessels (Cohen and Carlton 1995). After
its arrival, populations of P. amurensis grew
quickly throughout the San Francisco estuary
and major ecological changes were observed;
P. amurensis was found to outcompete other
species and completely changed the diversity
of benthic communities wherever it became
introduced (Cohen and Carlton 1995).

Venerupis philippinarum

Japanese littleneck clam, Manila clam

Native to the western Pacific, this clam was inadvertently
introduced to multiple locations on
the Pacific Coast of North America in the 1920s
and 1930s with shipments of Japanese oysters
from Asia. Manila clams have since spread via
larval transport and with the movement of
oysters between locations in Washington, Oregon,
and California. From 1943 to 1966, there
were several reports of the clam along the US
Pacific Coast from Puget Sound to multiple
locations in northern California. Most efforts in
the 1950s and 1960s to intentionally introduce
the clam to additional locations in Canada and
Oregon failed. However, introductions to the
Netarts estuary in the 1970s were successful
and populations of Manila clams remain
established there (Carlton 1979, Wonham and
Carlton 2005). In many of the locations where
Manila clams have become established, they
have become the “numerically dominant clam”,
with numbers reaching as high as 2,000/m2 in
the San Francisco estuary (Cohen and Carlton
1995). V. philippinarum is typically found in
higher regions of the intertidal zone, which has
been thought to limit competition with native
clams, but recent evidence shows introductions
of V. philippinarum in British Columbia
have caused declines in native species (Bendell
2014).

Table 4: Predicted invasive aquatic species threats.
* WP = Western Pacific (e.g., Japan); NP = North Pacific (e.g., Alaska); EA = Eastern Atlantic (e.g., Europe); SH = Southern Hemisphere.
** BW = Ballast water; SF = ship fouling; CO = commercial oyster culture; IP = intentional plantings.

Section 4. Threats to Human Health

Only a few species listed in this data summary
are considered potential threats to human
health. The purple varnish clam, Nuttallia
obscurata
, is often most abundant at freshwater
seeps in estuaries. During periods of
high freshwater runoff, these clams could
sequester harmful chemicals, bacteria, and viruses
that can be found in stormwater runoff
(WDFW 2015), possibly affecting the health of
humans when they consume purple varnish
clams.

Invasive species can also harbor pathogens
or parasites that affect humans. The salt
marsh snail, Assiminea parasitologica, and
the Chinese mitten crab, Eriocheir sinensis,
are both known hosts of the parasitic Oriental
lung fluke, Paragonimus westermani, which is
known to produce symptoms similar to that
of tuberculosis in humans (Draheim 2008;
CDC 2013). However, humans may become
infected only by consuming raw or inadequately
cooked crabs and snails.

Section 5. Background on Species with
Known Impacts

Biofoulers (sponges, hydroids, anemones,
tube-building amphipods, bryozoans, and
sea squirts)

Blackfordia virginica

Hydroid (no common name)
Large blooms of B. virginica can significantly
impact plankton community structure
through predation (Marques et al. 2015), but
no local impacts have been reported for this
species.

Botrylloides violaceus

Orange sheath sea squirt
This sea squirt is known to displace and
out-compete other fouling organisms. For
example, a study in California found B. violaceus
achieved 100% coverage of the surveyed
fouling community at two different locations
(Lambert and Lambert 2003). Another study
in California found this sea squirt showed
increased growth and survival at warmer than
ambient water temperatures compared to
native species, which suggests its potential
to persist during climate change (Sorte et al.
2010). In Nova Scotia, B. violaceus and other
sea squirts have also been found to foul native
eelgrass plants, causing increased mortality
and decreasing the productivity of eelgrass
beds (Wong and Vercaemer 2012).

Botryllus schlosseri

Golden star sea squirt
Local impacts of this species have not been
documented, but in Bodega Bay, California,
it was reported to be one of the eight most
abundant fouling species during two separate survey periods (1969-1971 and 2005-2009)
(Sorte and Stachowicz 2011). While several
studies in other parts of the species’ introduced
range also report that B. schlosseri can
become the dominant species of a fouling
community, the extent of its impact appears
to be variable. For example, one study of fouling
communities in Monterey Bay, California,
found B. schlosseri grew quickly and initially
out-competed other organisms for space, but
did not have lasting effects on community
structure (Sams and Keough 2012). In Nova
Scotia, B. schlosseri and other sea squirts
have also been found to foul native eelgrass
plants, causing increased mortality and
decreasing the productivity of eelgrass beds
(Wong and Vercaemer 2012).

Bugula neritina

Spiral-tufted bushy bryozoan
No local impacts are reported for this species,
but studies in California report it as a dominant
species in fouling communities, with
the ability to out-compete and out-perform
native species (Sorte and Stachowicz 2011).
Additionally, B. neritina (along with some
other non-native species) showed increased
growth rates and survival compared to native
species when challenged by warmer temperatures,
suggesting ecological impacts of this
species may intensify with climate change
(Sorte et al. 2010). In other parts of its range,
B. neritina is also known to dominate fouling
communities and can cause severe fouling of
fishing gear (Hodson et al. 1997). It also has
a high tolerance to copper-based anti-fouling
paint, which makes it difficult to prevent its
establishment and transport on ship hulls
(Piola and Johnston 2006).

Cliona sp.

Boring Sponge
These sponges bore cavities in the calcium
carbonate shells of shellfish that weaken the
shell and make the organisms more susceptible
to predation. While some species
of boring sponges are native to the Coos
estuary, one or more additional non-native
species have been introduced, including the
Atlantic boring sponge. One study in North
Carolina found Atlantic boring sponges can
significantly reduce growth rates and overall
health condition of eastern oysters (Carroll et
al. 2015).

Cordylophora caspia

Freshwater hydroid
No local impacts have been documented for
this species, but as with other invasive fouling
species, these hydroids have the potential to
achieve high densities and out crowd native
fouling organisms or cause economic impacts.
For example, dense overgrowth of C. caspia
colonies has been reported to clog intake
pipes of power plants, causing the plants to
be shut down for cleaning (Folino-Rorem and
Indelicato 2005). Although largely ignored
by native fish, C. caspia was found to be the
main prey item of non-native Shimofuri gobis
in a recently invaded California marsh (Matern
and Brown 2005). This suggests C. caspia
may have helped facilitate the invasion of
another non-native species.

Didemnum vexillum

Carpet sea squirt
The temperature and salinity conditions of
the lower Coos estuary are ideal for growth
and reproduction of D. vexillum (McCarthy et al. 2007, Valentine et al. 2007, Daley and
Scavia 2008). Colonies of this sea squirt also
produce acidic components that deter predators,
allowing colonies to grow unchecked.
There are no documented effects of D.
vexillum
in the Pacific Northwest, but several
studies from the eastern US have found D.
vexillum
can out-compete, overgrow, smother,
prevent recruitment of, and kill native
organisms, and cause significant declines in
biodiversity (Bullard et al. 2007, Mercer et
al. 2009, Morris et al. 2009). Due to the high
potential for impacts, it is listed on the Oregon
Invasive Species Council list of 100 Worst
Invasive Species (OISC 2013).

Diplosoma listeranium

Colonial sea squirt
No local impacts have been documented, but
this species in known to overcrowd native
fouling communities and negatively impact
aquaculture operations in other parts of its
introduced range (Fitridge et al. 2012). In Bodega
Bay, California, D. listeranium increased
from relatively low abundance in a 1969-1971
survey period to high abundance in a 2005-
2009 survey (Sorte and Stachowicz 2011).
The ability to thrive in warmer temperatures
compared to native fouling species favors the
survival and potential range expansion of D.
listeranium
during climate change (Sorte et al.
2010).

Ectopleura crocea

Pink-mouthed hydroidMolgula manhattensis

Sea grapes
No local impacts have been documented for
this species, but high densities of M. manhattensis
have been observed covering nearly
100% of the spatial area of settlement plates
in the Coos estuary (B. Yednock, pers. comm.
2016).

Monocorophium acherusicum (also reported
as Corophium acherusicum)

Tube-dwelling amphipod (no common name)
No local impacts have been documented
for this species, but one study in California
suggests high densities of filter-feeding crustaceans,
including M. acherusicum, can cause
significant declines in plankton biomass (Nichols
and Thompson 1985).

Styela clava

Club sea squirt
As with other non-native sea squirts, S. clava
can successfully out-compete native species
and significantly decrease species diversity
in fouling communities. It’s often found in
fouling communities of locally cultivated
oysters (Japanese oysters, Crassostrea gigas),
although detailed information on the distribution
and abundance of S. clava is not reported
for Coos Bay. A study in Southern California
found S. clava at every location that was surveyed,
with spatial coverage as high as 100%
across large portions of fouling substrate
(Lambert and Lambert 2003). In addition to
ecological effects, S. clava commonly fouls
aquaculture gear and, together with other non-native fouling species, has been reported
to reduce mussel harvests by as much as 50%
in Canada (Locke 2009; Arsenault et al. 2009).

Watersipora subtorquata

Bryozoan (no common name)
No local impacts have been reported for this
species, but studies in California show its abundance
has increased in Bodega Bay from low
to high numbers from 1971 to 2005 (Sorte and
Stachowicz 2011) and, given its ability to live
in warmer temperatures compared to native
fouling species,W. subtorquata will likely survive
and expand its range with climate change
(Sorte et al. 2010). W. subtorquata is resistant
to antifouling paints, making it difficult to deter
from boat hulls and a viable vector for transporting
other more sensitive non-native species
that grow on top of it (Floerl et al. 2004). Other
studies show this species can out compete
other fouling organisms for space and have persistent
effects on the presence and abundance
of other species in biofouling communities
(Sams and Keough 2012).

Crustaceans (Crabs, shrimp, amphipods, isopods)

Amphithoe valida

Amphipod (no common name)
No local impacts have been reported, but this
species has the potential to significantly impact
the production of eelgrass beds. In San Francisco
Bay, these amphipods were found to preferentially
feed on seeds of Zostera marina and,
based on grazing rates and densities observed
in eelgrass beds, could effectively remove all
of the seeds in an eelgrass bed within weeks
(Reynolds et al. 2012; Lewis and Boyer 2014).

Caprella mutica

Japanese skeleton shrimp
No local impacts have been documented for
this species; however in other areas of its
introduced range, this skeleton shrimp can
become very abundant and live in extremely
high densities. C. mutica were found to
completely displace native skeleton shrimp
in Scotland, even when initial densities of the
non-native species were quite low (Shucksmith
et al. 2009). Despite the potential for
negative effects on native species, C. mutica
invasions have yielded ecological benefits. For
example, in Bodega Bay, California, C. mutica
was found to prey on newly settled juveniles
of the invasive sea squirt Ciona intestinalis
(Rius et al. 2014). Despite its presence in
estuaries in California and Washington, C.
intestinalis
has not been found in the Coos
estuary; therefore it’s possible C. mutica may
help prevent or minimize the effects of a
future local invasion.

Carcinus maenas

European green crab
This species has successfully and aggressively
invaded every continent except Antarctica,
earning it a place on the World Conservation
Union’s (IUCN) 100 Worst Invasive Species list.
While studies have yet to measure the local
impacts of green crabs on native species in
the project area, one laboratory-based experiment
conducted with green crabs that were
collected from the Oregon Coast found them
to be more efficient predators of native Olympia
oysters (Ostrea lurida) than native Dungeness
crabs (Yamada et al. 2010). This is of particular
concern for projects aimed at restoring
and conserving native oyster populations in Coos Bay where green crab abundance and
densities are increasing in areas with suitable
oyster habitat. Also of concern are the many
documented negative impacts of green crabs
in other areas of the West Coast. In California,
green crabs have been found to significantly
alter the size, abundance and behavior of native
shore crabs (de Rivera et al. 2011), as well
as significantly modify benthic communities
(Grosholz et al. 2000), reduce food availability
for shorebirds (Estelle and Grosholz 2012),
and deplete Olympia oyster populations (Kimbro
et al. 2009). Green crabs have also been
found to directly out-compete commercially
and recreationally important Dungeness crabs
of similar size for food and valuable shelter
(McDonald et al. 2001). Intense predation
pressure of green crabs on a native clam has
also been documented in New Zealand and
threatens the success and viability of this fishery
(Walton et al. 2002). Foraging activity by
green crabs is also suggested to be destructive
to eelgrass beds (Davis et al. 1998), which
could impact the function of this important
habitat for other species, including commercially
important fish and invertebrates.

Jassa marmorata

Amphipod (no common name)
No recent or local impacts have been reported
for this species. Literature from California
in the 1950s indicates this amphipod can
grow in dense colonies that inhibit the recruitment
of native fouling organisms (Barnard
1958, cited by Fofonoff et al. 2003).

Limnoria tripunctata

Isopod (no common name)
No local impacts have been reported, but this
wood boring isopod has been reported to
cause extensive damage to wooden piling and
structures in San Francisco, British Columbia,
and elsewhere in its introduced range (Cohen
and Carlton 1995; Quayle 1992).

Orthione griffenis

Parasitic isopod (no common name)
This bopyrid isopod parasite is responsible for
drastic declines in populations of the native
mudshrimp, Upogebia pugettensis, along the
western coast of the United States (Dumbauld
et al. 2011). While the parasite doesn’t directly
kill mudshrimp, it causes significant blood
loss, resulting in the castration of its host, resulting
in a reduced overall reproductive rate
of a population to below sustainable levels.

Palaemon macrodactylus

Migrant prawn
No local impacts have been reported for this
species, but these shrimp are known to compete
with native shrimp for food resources in
San Francisco Bay (Sitts and Knight 1979).

Pseudodiaptomus inopinus

Asian calanoid isopod
No quantifiable impacts of this species have
been documented, but it’s become the dominant
copepod of many estuaries in Washington,
British Columbia, and Oregon – although
it was not especially abundant in the
Coos – and has the potential to significantly
impact primary production by overgrazing
phytoplankton (Cordell and Morrison 1996;
Grosholz 2002).

Rhithropanopeus harrisii

Harris mud crab
In the Coos estuary, these crabs are restricted to low salinity regions of the estuary due to
competition and direct predation pressure
by native Hemigrapsus oregonensis (Jordan
1989). No local impacts have been reported,
but Harris mud crabs are successful invaders
in several places across the globe and have
led to trophic cascades in intertidal communities
(Jormalainen et al. 2016).

Sphaeroma quoianum

New Zealand burrowing isopod
These burrowing isopods are found throughout
the Coos estuary and South Slough
(Davidson 2008). They create vast networks
of cylindrical burrows (2-10 mm in diameter)
in marsh banks, earthen dikes, wood, friable
rock, hard rock, concrete, and Styrofoam that
can support thousands of individuals per 0.25
m3 (Davidson 2006; Davidson et al. 2008b).
Their burrowing activity is known to weaken
shoreline substrates and has increased salt
marsh bank erosion at sites in California by as
much as 240% (Talley et al. 2001). Extensive
damage to docks and marine structures by S.
quoianum
has also been reported (see references
in Davidson 2008). In Coos Bay, 100,000
S. quoianum is estimated to remove as much
as 6 ft3 of marsh bank, 4 ft3 of Styrofoam, 3 ft3
of sandstone, or nearly 1 ft3 of wood in a two
month period (Davidson and de Rivera 2012).
Molluscs (snails, clams, mussels, oysters)

Molluscs (snails, clams, mussels, oysters)

Corbicula fluminea

Asiatic clam, golden clam
No local impacts have been reported for the
Asiatic clam, but large populations in San
Francisco Bay have been linked to significant
sediment and hydrologic changes in the Sacramento-
San Joaquin River Delta (including
extensive impacts to irrigation systems) and
declines in phytoplankton biomass (Cohen
and Carlton 1995; Lopez et al. 2006).

Crassostrea gigas

Japanese oysters
Japanese oysters occur at high densities in
aquaculture operations, but are also known
to escape these operations and establish feral
populations. No impacts have been reported
specifically for the Coos estuary, but negative
impacts of Japanese oysters are well-documented
in other locations. For example, in
Willapa Bay, Washington, Japanese oysters
were found to reduce the density and growth
of native eelgrass (Zostera marina) through
direct competition for space (Wagner et al.
2012). They are also know to significantly
alter intertidal habitats – specifically by converting
soft-bottom habitats to hard-bottom
shell reefs, which can promote the settlement
of native oysters, but reduces their survival
since native oysters have higher survival rates
in subtidal locations (Ruesink et al. 2005). The
movement of Japanese oysters among locations
for aquaculture has been a well-documented
vector by which other non-native
species and parasites have spread, causing
further impacts to native communities and
habitats.

Mya arenaria

Softshell clam
This is a popular species for recreational clamming
in Oregon estuaries, including the Coos.
No negative impacts have been recorded
locally, but large populations of these clams
have replaced native clams in San Francisco Bay (Cohen and Carlton 1995). A positive
impact has been documented in Washington,
where high densities of juvenile Dungeness
crabs were found in large deposits of M.
arenaria
shells in Grays Harbor compared to
adjacent mudflat areas (Palacios et al. 2000).
In California, M. arenaria is an important prey
item for native water birds, fish and crabs
(Cloern et al. 2007).

Philine auriformis

New Zealand sea slug
As a specialist predator of small bivalves, this
sea slug has the potential to impact native
clams. No local impacts have been documented,
but declines in bivalve populations in California
have been associated with invasions of
P. auriformis (Cadien and Ranasinghe 2001).

Potamopygrus antipodarum

New Zealand mud snail
There are no reports of abundances or direct
impacts to the native community by Potamopygrus
antipodarum
for the project area.
However, in other parts of their introduced
range in the western United States these
snails have been found at densities as high
as 300,000/m2 and have caused significant
trophic level effects, reduced growth rates of
native invertebrates due to competition for
food resources, and in some cases have even
been associated with declines in other invertebrate
species (Hall et al. 2003; Kerans et al.
2005; Hall et al. 2006; ).

Teredo navalis

Naval shipworm
Local impacts of these bivalves have not been
quantitatively studied, but they have been found boring into wood structures and pilings
around the Coos estuary. In California, they
have been responsible for billions of dollars in
damage to maritime infrastructure throughout
San Francisco Bay (Carlton 1979; Cohen
and Carlton 1995).


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