Status and habitat associations of the threatened northern abalone: importance of kelp and coralline algae

Abstract

Northern abalone (Haliotis kamtschatkana kamtschatkana) is a federally listed species of concern. The status of northern abalone and the characteristics of the habitats they associate with were determined showing that northern abalone have declined dramatically in Washington State with present day abundances <10% of those found in 1979. Northern abalone inhabited kelp beds (Nereocystis luetkeana), more than red sea urchin beds (Strongylocentrotus franciscanus) (X2 = 16, d.f. = 1, P < 0.01) or habitats with both kelp and sea urchins (X2 = 13.2, d.f. = 1, P < 0.01). Sites with Nereocystis kelp canopy had twice the percentage cover of encrusting coralline algae compared with sea urchin sites. No juvenile abalone (<75 mm) were found in any of the habitat types raising concerns about recruitment failure. Abalone co-occurred with other molluscs including limpets and scallops. Kelp holdfast microhabitats had significantly higher species richness (t = 2.2, d.f. = 6, P < 0.05), twice the effective number of species and 5x more individuals than sea urchin spine microhabitats. In laboratory choice experiments, juvenile abalone (20 mm) preferred coralline rocks to kelp holdfasts or sea urchin spine canopy. The small snail, Amphissa spp. (5–15 mm) was more abundant inside kelp holdfasts than under sea urchins or in rock cobble, suggesting this may be an important microhabitat. It is recommended that kelp beds with abundant coralline substrate be used for restoration including stocking juveniles and adult aggregations as this biogenic habitat may enhance northern abalone restoration actions. Copyright © 2011 John Wiley & Sons, Ltd.