Nearshore fish assemblages in the vicinity of two Steller sea lion haul-outs in southeastern Alaska

Nearshore fish assemblages in the vicinity of two Steller sea lion haul-outs in southeastern Alaska

J.F. Thedinga, S.W. Johnson, and D.J. Csepp

Nearshore fish assemblages in the vicinity of two Steller sea lion haul-outs in southeastern AlaskaThis is part of Sea Lions of the World
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Description

To better understand Steller sea lion foraging ecology, information is needed on the species composition, abundance, and seasonality of prey species, especially in nearshore waters adjacent to rookeries and haul-outs. From 2001 to 2004, we examined nearshore fish assemblages in summer and winter in the vicinity of two Steller sea lion haul-outs, Benjamin Island and The Brothers Islands, in southeastern Alaska. Fish were captured in nearshore waters (<115 m deep, <350 m from shore) by beach seining and hand-jigging; we also observed fish assemblages with a remotely operated vehicle (ROV). Total catch by seining and jigging for all sampling periods was 201,331 fish and 559 fish; 58 species were identified in summer and 44 species in winter. Seine catches were dominated by young-of-the-year walleye pollock, Pacific herring, and Pacific sand lance in summer, and salmon fry, armorhead sculpin, and rock sole in winter. Jig catches were dominated by armorhead sculpin, Pacific cod, and two rockfish species in summer and winter. Twenty-seven species were observed with the ROV; seven of these species were not captured by seining or jigging. Catch and number of fish species were greater in summer than in winter and greater at The Brothers Islands than at Benjamin Island. Most fish captured by seining were too small (median fork length [FL] <81 mm) to be consumed by Steller sea lions, whereas most fish captured by jigging or observed with the ROV were large enough (median FL >248 mm) to be consumed by Steller sea lions. Inclusive of all sampling methods, 34 of the species inventoried have been identified in Steller sea lion scat collected at either haul-out. Although the extent of Steller sea lion foraging in nearshore waters surrounding Benjamin Island and The Brothers Islands is unclear, a diverse fish assemblage is present at both locations and may be an important prey field for Steller sea lions.

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