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Middle Columbia River Aquatic Nonindigenous Species Survey - MCRANS

Contact Information

Robyn Draheim
draheim@pdx.edu
Portland State University
Center for Lakes and Reservoirs
PO Box 751
Portland OR 97207-0751
Ph:503-725-4994
Fax: 503-725-3834

Middle Columbia River Aquatic Nuisance Species Survey - Final Report. 2007(.pdf)

Overview

Establishment of aquatic non-indigenous species (ANS) beyond their native range can have significant ecological and economic impacts (Pimental 2000). Successful establishment of ANS populations are based on introduction rates, suitable habitat, and interspecific competition. Human activities have increased introduction rates, altered habitats, and affected native species populations.

The Columbia River Basin is no exception with significant habitat changes from impoundment and land use changes; increased ANS introductions through shipping, nursery trade, and fishery enhancements; and native species population changes through exploitation and competition with and predation by prior ANS introductions. As a result, established populations of non-indigenous fish (smallmouth bass, Micropterus dolomieue; walleye, Stizostedion vitreum), aquatic plants (eurasian watermilfoil, Myriophyllum spicatum), and mollusks (Asian clam, Corbicula fluminea; New Zealand mud snail, Potamopyrgus antipodarum), have been documented throughout the system. By conservative measures, 82 ANS have invaded the tidally influenced section of the lower Columbia River since the mid 1800's (Sytsma et al. 2004, P.Heimowitz pers. com.) while fewer non-indigenous fish species have been documented in the unimpounded Hanford reach of the middle Columbia River (Li et at. 1987). Other portions of the Columbia River system have not been surveyed as thoroughly although habitat changes and human caused vectors are just as prevalent.

The objective of the Middle Columbia Aquatic Non-indigenous Species Survey (MCRANS) was to provide a comprehensive survey and analysis of all ANS present in the middle portion of the river system, an area delineated by Bonneville Dam (RKM 235) to Priest Rapids Dam (RKM 639) along the Columbia River and from the mouth of the Snake River to the pool formed by the lower Granite Dam (RKM 224) for a total of 628 river kilometers. Basic information on species presence is necessary for ecosystem management. A comprehensive list of nonnative species distribution is the first step to understanding invasions, assessing impacts, and developing effective management actions in the middle Columbia River.

The MCRANS project includes a review of available literature, a comprehensive field collection of targeted taxa conducted in summer 2006, and a final report containing the analyses of both efforts. This study was designed to build on the Lower Columbia River Aquatic Non-indigenous Species Survey (Sytsma et al. 2004), which began in 2001. Like LCRANS, MCRANS was undertaken to provide comprehensive information about the ANS present in the Columbia River. The results of this mid-basin investigation will serve as a baseline for evaluating the rate of species introductions to the river and the efficacy of management action, and contribute important new information to ongoing regional ANS studies. In addition, the data may be useful for determining where the middle Columbia River and lower Snake River systems are vulnerable to invasion and for evaluating effects of introductions on important ecological processes.

The literature review and field sampling found that 50 ANS were introduced to the
middle Columbia River since the 1880s. Most of these ANS were fish (54%), aquatic plants
(14%), and crustacea (12%). The remaining 24% were mollusks, bryozoans, hydrozoans,
annelids, one amphibian, and one aquatic mammal. We believe that 50 is a conservative
assessment of the number of ANS in the system because of temporal and spatial limitation on our
field sampling, inadequate taxonomic resolution in prior studies, and the abundance of
unresolved and cryptogenic taxa.

Intentional stocking for fisheries and wildlife enhancement was the most common vector
for species introduction. Ballast water and intentional release by individuals were also import
vectors for introduction. Interestingly, recreational boating was associated with only a small
number of ANS in the middle Columbia River. North America, East of the Rocky Mountains
was the most common source area of ANS in the river, primarily because of the high number of
fish introduced to the Columbia from that region. Europe was the second most common source
region, particularly for plants.

We found only anecdotal evidence for barge transport of ANS in the river; there was no
clear association between abundance of ANS and proximity to port facilities. Most barges do not
utilize ballast water when operating in the river, and fouling organisms are much less abundant in
freshwater than in marine systems, which reduces the importance of hull fouling as a vector for
transport of ANS in the river.

We found no clear relationship between proximity to boat launches and abundance of
ANS, nor did we find a difference in the number of ANS in samples from the free-flowing
Hanford Reach and the reservoirs sites. Lack of spatial evidence of vector effects and habitat
alteration on the abundance or ANS may be expected in systems with relatively high current
velocities and mixing, even in impounded areas. Low sampling intensity may also have limited
the capability of our study to reveal site differences. Despite the lack of association between
perceived vector strength (e.g., proximity to ports and boat launches) and ANS abundance,
focused sampling of these areas for early detection of new introductions, particularly for sessile
organisms, is a reasonable strategy.

Additional surveys of the river are recommended. The upper reaches of the Columbia
have not been the subject of a synoptic survey for ANS to establish a baseline for evaluating the
rate of ANS introduction. The lower Columbia was surveyed previously to establish a baseline
and periodic follow-up surveys are recommended. Repeated surveys of the lower, middle, and
upper Columbia River on a six-year cycle would allow complete coverage of the most important
water resource in the Pacific Northwest and permit estimation of ANS invasion rate, which
should decrease if current management strategies are effective.

Research is needed to better manage ANS in the Columbia and Snake Rivers. Study of
the importance of multiple stressors, e.g., pollution, water withdrawals, impoundment, and global
climate on the biological communities in the system and the facilitation of ANS invasion would
aid in management of salmon stocks as well as ANS in the river. Impacts of ANS, including
those that are already well-established in the system, are poorly understood. The role of hull
fouling in transport of organisms, particularly on slow-moving barges, between the Columbia
and other estuaries and between upper and lower reaches of the Columbia also requires
additional study to effectively manage this potentially important vector for ANS. Similarly, other
vectors such as trade in ornamental and aquarium species and intentional stocking activities
require more stringent control to prevent introduction of ANS to the Columbia River.