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Auke Bay Laboratory (ABL)

Understanding the Contribution of Fishing Activity to Riverine Pollution

In an effort to better understand the contribution of fishing activity to riverine pollution, scientists from the Habitat Investigations Program have been working in conjunction with local groups in Kenai, Alaska, to assess the relative contribution of urban development and boating activity to the levels of hydrocarbons and persistent organic pollutants in the Kenai River.  The local non- profit Kenai Watershed Forum gathers the samples, and scientists provide analyses and interpretation of the data. Funding is provided by the National Marine Fisheries Service (NMFS) Office of Restoration.

The Kenai River has proven to be an excellent laboratory in which to characterize and separate various sources of pollution. The 50-mile long river is one of the world's most productive anadromous salmonid rivers and a popular destination for sport fishers. The river flows through two towns in the lower reach and is subjected to a variety of human perturbations ranging from habitat loss to pollution input over the first ten miles of the river. Upstream, the Kenai watershed has a number of areas with little or no human activity. If pollution is detected in those regions, the source is likely to be remote, not local. The Kenai watershed is the largest producer of salmon to commercial fisheries in the Cook Inlet region and is heavily utilized by subsistence fisheries and sport fisheries. The heavy seasonal use by recreational boaters and fishers may affect water quality, non-point source runoff from the communities may add substantially to the pollution load of the river, and pollutants transported atmospherically from remote areas may be present directly in the watershed or indirectly by contaminants released from tissues of fish returning to spawn in the river. The project targets sampling for three sectors: urban runoff, boat traffic, and transport of persistent organic compounds via aerial transport or via fish returning from the ocean. Combinations of types of analyses, seasonal measurements, and spatial sampling will attempt to assess the relative significance of these different factors.

The Kenai Watershed Forum has taken an active role in documenting pollution inputs to the river. Working in conjunction with Federal, state, and local government agencies, the forum is in the third year of gathering water samples from throughout the Kenai River drainage and analyzing for metals and mono-aromatic hydrocarbons in the river. The NMFS is partnering with volunteer labor to gather samples and help interpret patterns of contamination. Forum staff are trained scientists and are well aware of the care needed to properly gather water samples for trace analysis.

Once the sources of pollution to the watershed are identified and the magnitude of each source quantified, it will be possible to identify restoration activities to mitigate the effects of pollution. If much of the pollution level present in salmon available to sport and subsistence users is derived from atmospheric rather than from local sources of contamination, this will have wide-ranging implications for fisheries management in Alaska. If however, the levels of these compounds are low, local restoration can concentrate on boat traffic and urban runoff.

Seasonal Increases in Polycyclic Aromatic Hydrocarbons in a Small Alaskan Lake

Passive sampling devices were deployed in Auke Lake, a small oligotrophic lake in Southeast Alaska, to determine seasonal input of aromatic hydrocarbons. Auke Lake, which provides rearing and spawning habitat for seven salmonid species, receives hydrocarbon input from seasonal recreational use of personal watercraft with two-cycle engines and from year-round urban use such as highway runoff and fuel oil spills. Sampling devices were deployed in the lake for 21-day periods throughout the year. Auke Lake, like many recreational lakes, had seasonal increases in petroleum hydrocarbon input, primarily in the surface waters. Relative input of polycyclic hydrocarbons increased in the summer with peaks occurring during times of highest recreational personal watercraft use.

By Adam Moles.

Spring Emigrant Salmonid Counts at Auke Creek Weir

A total of 121 consecutive days of weir operations and fish counting, sampling and marking concluded at the end of June 2002 at Auke Creek, Alaska, marking the twenty-third consecutive year of total downstream counts of all emigrant salmonids. The weir is installed annually on 1 March and operated in the downstream mode through June. For the year 2002, pink and sockeye salmon counts were above average, whereas coho salmon, Dolly Varden char and cutthroat trout counts were below average. More than 150,000 pink salmon fry emigrated this year, about 44,000 above average. The 2002 migration is the largest pink salmon fry migration since 1993 and the eighth largest since migrations were first recorded at the weir in 1972. The 2002 sockeye salmon smolt count of 17,594 was 700 fish above the 1980-2002 average. Yearling smolts accounted for 36% of the migration, and averaged 3.5 g and 75 mm, smaller than the average size observed over the last two decades. Two-year old smolts were 14 g and 119 mm, the smallest age-2 smolts in the last 8 years. The coho salmon smolt emigration of only 3,434 fish was the lowest count on record. The long-term average of coho salmon smolt emigration from 1980 to 2002 is 6,303. Auke Lake coho salmon smolt production has been decreasing since 1980. During the emigration it was noted that nearly 50% of the smolts were heavily parasitized by the round worm Phylonema sp. Some smolts were badly disfigured by a swollen abdomen and could not swim well. This may reduce their early ocean survival. A total of 210 cutthroat trout were counted during the downstream migration, below the average 261. The cutthroat trout emigrations have been in a decreasing trend since 1994. The Dolly Varden char count this year, 4,858, was the lowest since 1986 and less than the long-term average, 6,361. Dolly Varden char emigrations have steadily decreased since 1995.

Several studies at Auke Creek are under a cooperative agreement between NMFS, Alaska Department of Fish and Game (ADF&G), and the University of Alaska- Fairbanks (UAF) School of Fisheries and Ocean Sciences. The cooperative wild coho salmon smolt tagging project at Auke Creek involving the commercial and sport fish divisions of the ADF&G is one of four sites in northern southeast Alaska where wild smolts are tagged annually. The 2002 cooperative cutthroat trout projects, tagging and recovery of downstream migrants, and population estimates in Auke Lake, were successfully concluded for the spring season. Dion Oxman, a University of Alaska-Fairbanks graduate student, successfully completed the second year of his project on pink salmon as part of continuing, cooperative studies with UAF on pink salmon genetics.

By Jerry Taylor.


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