Original Paper

Marine Biology

, Volume 156, Issue 11, pp 2247-2254

First online:

Biodiversity and rockfish recruitment in sponge gardens and bioherms of southern British Columbia, Canada

  • Jeffrey Burton MarliaveAffiliated withVancouver Aquarium Email author 
  • , Kim W. ConwayAffiliated withGeological Survey of Canada
  • , Donna M. GibbsAffiliated withVancouver AquariumPacific Marine Life Surveys
  • , Andy LambAffiliated withPacific Marine Life Surveys
  • , Charles GibbsAffiliated withPacific Marine Life Surveys

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Abstract

In the Strait of Georgia and Howe Sound, British Columbia, colonies of individual cloud sponges, growing on rock (known as sponge gardens) receive resource subsidies from the high biodiversity of epifauna on adjacent rock habitats. Bioherms are reefs of glass sponges living on layers of dead sponges. In the same area as the sponge gardens, newly discovered bioherms in Howe Sound, BC (49.34.67 N, 123.16.26 W) at depths of 28- to 35-m are constructed exclusively by Aphrocallistes vastus, the cloud sponge. The sponge gardens had much higher taxon richness than the bioherms. The sponge garden had 106 species from 10 phyla, whereas the bioherm had only 15 species from 5 phyla. For recruiting juvenile rockfish (quillback, Sebastes maliger), the food subsidy of sponge gardens appears to be missing on bioherms of cloud sponge, where biodiversity is relatively low. While adult and subadult rockfishes (S. maliger, S. ruberrimus, S. proriger, and S. elongatus) were present on bioherms, no evidence for nursery recruitment of inshore rockfishes to bioherms was observed, whereas the sponge gardens supported high densities of newly recruited S. maliger, perhaps owing to the combination of both refuge and feeding opportunities. These results indicate that sponge gardens form a habitat for early stages of inshore S. maliger, whereas A. vastus bioherms are associated only with older juvenile and adult rockfishes.