Invasive and Non-native Species in the
Lower Coos Watershed

Jenni Schmitt, Bree Yednock, Erik Larsen, Craig Cornu, Colleen Burch Johnson
-South Slough NERR

Vegetation: The lower Coos watershed
supports many invasive plants such as
European beachgrass which has significantly
altered the Lower Bay subsystem.

Aquatic Invertebrates: Over 60 non-native
aquatic invertebrates species occur in the
Coos estuary; additional invasions are likely.
Despite the potential for significant ecological
and economic effects, little is known about
the status of most of these species.

Terrestrial Invertebrates: No invasive
terrestrial invertebrate populations are
currently established in the project area,
though local forests are at risk of invasion.

Vertebrates: Evidence indicates the local
presence of large populations of invasive
nutria, and small declining populations of
non-native American shad and striped bass.

Subsystems: 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

Subsystems: 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

This section includes the following
data summaries: Vegetation,
Aquatic Invertebrates, Terrestrial
Invertebrates, and Vertebrates—

which describe invasive and other
non-native species in the Coos estuary
and lower Coos watershed.

Non-Native and Invasive Vegetation: This
data summary provides profiles of 58 invasive
or non-native plant species that are either already
established in, or are imminent threats
to the project area. The narrative is separated
into three sections – invasive or non-native
plants that are: 1) Predicted threats – invasive
vegetation not yet found in the project
area but will be in the future; 2) Partially contained
threats – invasive vegetation currently
found only in isolated populations within the
project area; and 3) Established threats – invasive
vegetation found across much or all of
the project area.

Local distribution of each species is discussed
where information is available. Sources include
invasive species response plans, which
often include targeted monitoring efforts
(e.g., Howard et al. 2007; ODF 2014a and
2014b) and statewide species profiling efforts
(ODA 2014). Information from scientific
publications (e.g., Posey 1988 and Hacker et
al. 2012) and Online spatial databases (e.g.,
USDA 2015a) were also referenced. The vast
majority of early non-native vegetation species
detections have come from local biologists
noticing unusual plants (e.g. information
personally communicated by A. Brickner
2015). A Background section summarizes the information
available describing the local or
regional environmental and economic effects
of each non-native or invasive vegetation

Non-Native and Invasive Aquatic
This data summary includes
information for 62 species of non-native
aquatic invertebrates and algae that have
become established in the lower Coos watershed
(project area), as well as 12 high
risk aquatic non-native species not currently
locally established but considered imminent
threats. Information sources are mainly
comprehensive invasion histories compiled
for several US West Coast locations, including
Coos Bay (Carlton 1979, Cohen and Carlton
1995, Wonham and Carlton 2005). Species
distribution information within the Coos estuary
comes from fouling community surveys
(Hewitt 1993, de Rivera et al. 2005) and species-
specific studies (e.g. Berman and Carlton
1991, Jordan 1989). A Background section summarizes what little
information is available describing the local or
regional environmental, economic and public
health effects associated with non-native or
invasive aquatic invertebrates.

Non-Native and Invasive Terrestrial
Information about invasive
terrestrial vertebrates comes primarily from
Online publications by the United States Department
of Agriculture (2003a, 2003b, 2006,
2008, n.d.a, n.d.b), Oregon State University
(2011), Purdue University (Sadof 2009), and
United States Forest Service (n.d.). Estimates
of the extent of damage caused by invasive
insects come from peer-reviewed scientific
literature (Kovacs et al. 2010; Nowak et al.
2001). These sources are supplemented by
personal communication with invasive species
specialists working in Oregon (e.g., Williams
pers. comm. 2015).

Non-Native and Invasive Vertebrates: This
data summary summarizes available information
for American shad, striped bass and
nutria – three ecologically or economically
significant species. For each species, we describe
what’s known about their current status
and distribution, any available population
trends, and information on their effects on
native species. Other issues associated with
each species is also discussed (e.g., bacterial
infections of American shad, unprecedented
levels of hermaphroditism in striped bass) .

Pathogens: While numerous invasive pathogens
(e.g., fungi or viruses) exist, they were
not covered in this chapter due to time
constraints. Several serious plant pathogens
of concern to the project area have been covered
in the “Terrestrial Vegetation in the Lower
Coos Watershed” within the Vegetation
Chapter. These include the Port Orford cedar
root rot pathogen (Phytophthora lateralis),
and the fungus that causes Swiss needle cast
disease (Phaeocryptopus gaeumannii).

Data Gaps and Limitations

Non-Native and Invasive Vegetation: A
general lack of comprehensive spatial information
on non-native and invasive vegetation
species impose limitations on our data
summary. There are two main reasons for the
limitations: 1) Few comprehensive surveys or
monitoring programs exist that identify locations
of non-native and invasive plants in the
project area; and 2) Many spatial data that
do exist come from anecdotal, often chance
observations, which can introduce skewed
impressions of species distributions.

Even though other spatial data exist, to simplify
this data summary only maps with the
most comprehensive monitoring information
(e.g. gorse and purple loosestrife) or those
with location information of early invaders
(e.g., Spanish heath and old man’s beard)
were included.

Non-Native and Invasive Aquatic
Only a few systematic surveys
of invasive aquatic invertebrate species have
been undertaken in the project area (e.g.
Laferriere et al. 2010, Davidson 2006 and
2008), therefore there are large data gaps in
our understanding of their distribution in the
Coos estuary. Likewise, knowledge of environmental
and economic effects of many aquatic
species is lacking.

Non-Native and Invasive Terrestrial
The available information
about the threat of non-native and invasive
insect introductions to the project area is
based on projections from academic and government
agency scientists, and local experts.
However, since recent technological advances
have resulted in the accelerated movement
of goods and people across the globe, the
spread of invasive insects has become increasingly
difficult to monitor and predict
(Hulme 2009). While these expert opinions
represent the best available information, it’s
possible that unforeseen events (e.g., previously
unaccounted for vectors of transport)
could lead to the introduction of non-native
and invasive species not currently anticipated
by the experts. In some cases, species
that pose the highest risks have appeared
intermittently in Oregon (e.g., gypsy moths).
Early detection rapid response programs
have eliminated these threats before they
have become established locally. However, if
isolated populations have gone undetected,
it’s possible that additional, yet to be discovered
threats may currently exist within or in
proximity to the project area.

Non-Native and Invasive Vertebrates: Striped
bass and American shad data come from
long-term Oregon Department of Fish and
Wildlife (ODFW) monitoring efforts whose
priorities shifted over time (ODFW 2009
and 2013). ODFW initially sampled (starting
in 1965) all fishes in the Coos system, but
shifted its focus to American shad and striped
bass beginning in the late 1970’s. As American
shad and striped bass populations declined,
ODFW’s long-term monitoring focus shifted
in 2006 to Chinook salmon. American shad
and striped bass (along with other fishes) are
still identified and counted during Chinook
sampling. But American shad and striped
bass population and distribution data should
only be considered comprehensive between
the late 1970’s and 2006.

There are additional limitations to the American
shad and striped bass data in the sampling
methods used. Seining methods have
remained standard over the years, but fish
identification varies by staff abilities. In addition,
the seining effort was not identical in all
years (some sites were missed— especially
after the sampling focus shifted to Chinook)
and during some years sampling was skipped
altogether. Finally, seining methods may have
inadvertently introduced bias into the sampling
since seining is not effective at capturing
all fish (e.g., larger more mobile fish species).
Finally, descriptions of the health of American
shad and striped bass rely on older information
from the primary literature (e.g., Carlton
1989), and some theses (e.g., Anderson

Nutria data are limited as no standard protocols
have been adopted to assess nutria distribution
or abundance in Oregon. Sheffers and
Sytsma (2007) used district ODFW wildlife
biologists’ best estimates to create a relative
nutria density distribution map for Oregon
(Figure 2 in the data summary). Although
these scientists have an intimate knowledge
of the watersheds in which they work, they were not always able to estimate relative
nutria densities, leaving a large number of
sub-watersheds unrepresented. Since these
were judgment calls based on best professional
knowledge, conclusions based on this
map should be used with caution.

Comprehensive nutria density and distribution
data are lacking for the project area
and for Oregon in general, despite anecdotal
evidence suggesting the local presence of
relatively large sustaining populations and
structural damage to local marsh habitats and
human infrastructure.


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