AUKE BAY LABORATORY (ABL) (cont.)

Seasonal Availability of Nearshore Prey to Steller Sea Lions
at Two Haulouts in Southeast Alaska

Steller sea lion (SSL) abundance is decreasing in central and western Alaska but is increasing in southeastern Alaska. Hypotheses for the decline in the western part of the SSL range include decreased food availability and lower diet diversity.

In 2001, we initiated a seasonal study at two SSL haulouts in southeastern Alaska to 1) identify prey available in nearshore waters (< 100 m deep), and 2) serve as a comparison to similar studies in areas where SSL are in decline. Study areas were Benjamin Island, a seasonal haulout used by up to 800 SSL, and Brothers Islands, a year-round haulout used by nearly 1,300 SSL. At each haulout, available prey species were inventoried by beach seine, jig, and with a  remote operated vehicle (ROV) in summer and winter.

Regardless of sampling method, total catch of all species was greater in summer than in winter at both haulouts and greater at Brothers Islands than at Benjamin Island. At Brothers Islands, total seine catch in July 2001 and 2002 was nearly 85,000 fish of 37 species compared to 7,200 fish of 37 species at Benjamin Island. Total seine catch in March 2002 was less than 350 fish at each haulout (≤ 25 species).

Seine catches were dominated by juvenile pollock and sand lance in summer and armorhead sculpin, tubesnout, and rock sole in winter. Jig catches ranged from eight fish per rod hour in summer to two fish per rod hour in winter. Fish captured by jig were larger (> 190 mm mean fork length) than fish captured by seine (< 100 mm mean fork length). Jig catches were dominated by armorhead sculpin, Pacific cod, dusky rockfish, pollock, and yellowfin sole. Sixteen of the species we captured have been identified in SSL scat at either the Brothers Islands or the Benjamin Island haulouts.

We hypothesize that the less available prey in winter force SSL to travel farther and longer from haulouts to forage.

By John Thedinga.

Annual Auke Creek Cooperative Research and Planning Meeting

The annual Auke Creek interagency meeting was held on 14 February 2003 and attended by representatives of the National Marine Fisheries Service (NMFS), the ADF&G, and the University of Alaska-Fairbanks (UAF). Summaries and operational plans were presented on projects for 2003 at the Auke Creek weir. There are currently 21 projects scheduled at Auke Creek for the 2003 season.

The NMFS will continue the long-term data collections on all species, emphasizing data on marine survival and freshwater production of pink, coho, and sockeye salmon. The ADF&G will continue with their long-term research programs on Dolly Varden char, cutthroat trout, and coho salmon. The UA will not have any incubation projects or graduate students at Auke Creek in 2003, but may begin an outbreeding depression study on pink salmon in 2004.

Two UAF graduate students presented summaries of their thesis research conducted at Auke Creek last year. Leon Shaul’s report (ADF&G) on the Southeast Alaska coho index stocks showed marine survival decreasing in all areas except at Auke Creek, which is one of the ADF&G index coho stocks. Rick Focht of the Macaulay Hatchery, Douglas Island Pink and Chum Corporation, presented a summary of the 2002 return of chinook released in Auke Bay near Auke Creek and discussed plans for the release of chinook juveniles in Auke Bay in 2003.

By Jerry Taylor.

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AFSC Quarterly
Research Reports
Jan-Feb-Mar 2003