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).
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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Auke Bay Lab