Fish-habitat associations and the importance of deep-sea corals in Olympic Coast National Marine Sanctuary

Katie Renee Wrubel

Declining populations and sizes of commercial groundfish have prompted fishery managers to identify important habitats for recovery of fish stocks. Habitats that are important for fish for spawning, breeding, feeding, or growth to maturity, are classified as essential fish habitat (EFH) and designated with some level of protection. However, an EFH Conservation Area was designated with little information on fish distributions and habitat requirements in deep-sea ecosystems off of Washington State. Consequently, in 2006 and 2008 remotely operated vehicle surveys were conducted to identify fish-habitat associations as well as to determine the importance of deep-sea corals as fish habitat. Five major habitat and associated species assemblages were identified from canonical correspondence analysis: (1) boulder habitats dominated by rockfish (Sebastes spp.) as well as globular sponges and small Swifta beringi corals; (2) rock ridge habitats in which structure-forming deep-sea corals and redbanded rockfish (Sebastes babcocki) were associated; (3) coarse soft sediments consisted of Swifta spp. corals and flatfish; (4) mud habitats dominated by flatfish, eelpouts (Zoarcide), and poachers (Agonidae); and (5) habitat generalists occurring over several diverse habitat types. Of the ten deep-sea coral species analyzed, none were found to be selected for by fish as important habitat identified from selectivity indices. Despite low selectivity, corals were still frequently used by v fish, in which Primnoa pacifica and Lophelia pertusa had high fish use (~70%) when available. Low-relief habitats with corals had higher fish abundance than similar habitats without corals; however fish abundance was significantly higher on boulder habitats without corals than with corals present. By parsing out the importance of corals as fish habitat over similar physical substrates we found that structure is important in rockfish habitat use. Thus, deep-sea corals are likely important components of EFH over lower complexity or mixed substrates, but may not be as important in high-relief complex boulder habitats. This study provides baseline data for current conditions and future comparisons to determine the efficacy of the EFH Conservation Area in rebuilding fish stocks in deep-sea ecosystems.

Fish-habitat associations and the importance of deep-sea corals in Olympic Coast National Marine Sanctuary

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