• Kelp beds as fish and invertebrate habitat in southeastern Alaska

      Calvert, Elizabeth L.; Stekoll, Michael; Shirley, Thomas; Hillgruber, Nicola (2005-08)
      Throughout the temperate marine regime, the shallow subtidal is dominated by rocky reefs and algal assemblages. The ecological significance of high-latitude, cold-water kelp systems is poorly understood particularly for Alaska. Two large-scale experiments conducted near Juneau, Alaska were designed to study fish and invertebrate assemblages in regard to (1) canopy forming Nereocystis luetkeana (1500 m² manipulations) and (2) sub-canopy forming Laminaria bongardiana (600 m²). Fish and invertebrates were quantified using Standard Monitoring Units for the Recruitment of Fish (SMURFs), light traps, and visual surveys. The canopy kelp experiment revealed significantly greater abundance (X=0.57 fish/SMURF; X=0.28 fish/SMURF) and biomass (X=0.95 g/SMURF; X =0.23 g/SMURF) of benthic fishes at Nereocystis sites versus sites without canopy kelp. In contrast, a direct negative effect of Nereocystis was observed for schooling fish; significantly more fish were observed at sites without canopy kelp as compared to Nereocystis sites (X=27.3 fish/15 m³; X=4.2 fish/15 m³). Fish assemblages were independent of L. bongardiana, yet invertebrates were twice as abundant at sub-canopy sites. Nereocystis has direct and indirect effects on fish distributions through behavioral and habitat modifications. Overall, canopy kelps with associated sub-canopy kelps promote more abundant and rich fish assemblages in southeastern Alaska, while invertebrate assemblages are greater in sub-canopy areas.