Science Response 2018/032

Glass sponge aggregations in Howe Sound: locations, reef status, and ecological significance assessment

Context

The protection of benthic communities and features falls within the mandate of the Department of Fisheries and Oceans (DFO) at the national level under the Oceans Act, Fisheries Act,and under ratified international agreements. The plan to meet conservation targets includes advancing Other Effective Area-Based Conservation Measures (OEABCM), such as fishing closures, to protect sensitive sponge and coral aggregations.

Glass sponge reefs are unique habitats found along the Pacific coast of Canada and the United States with historic, ecological, and economic value. They link benthic and pelagic environments by playing important roles in filtration and carbon and nitrogen processing, and acting as silica sinks (Chu et al. 2011, Tréguer and De La Rocha 2013, Kahn et al. 2015). They also form habitat for diverse communities of invertebrates and fish, including those of economic importance (Cook et al. 2008, Chu and Leys 2010, Dunham et al. 2015, 2018).

Over the past 15 years, nine glass sponge reef complexes were discovered and mapped in the Strait of Georgia and Howe Sound using remote sensing (Conway et al. 2004, 2005, and 2007) and subsequently ground-truthed by DFO Science using standardized visual survey methods in 2012-2013. In 2014, DFO requested that fishers using bottom-contact gear voluntarily avoid these areas while DFO consulted on formal protection measures. After reviewing important input from the consultation process with First Nations, commercial and recreational fishers, and conservation organizations, formal bottom-contact fishing closures were established, effective June 12, 2015. Since April 1, 2016, the closures also apply to First Nations Food, Social, and Ceremonial fisheries. In 2017, DFO Science provided peer reviewed and approved quantitative assessment methods, outputs, and monitoring advice for these sponge reef complexes (DFO 2017, Dunham et al. 2018).

Recently, 13 additional areas thought to be glass sponge reefs were discovered by the Marine Life Sanctuaries Society (MLSS) and volunteer divers in Howe Sound, using drop camera and dive surveys (Clayton and Dennison 2017). In 2016, the MLSS shared their findings with DFO Science and Fisheries Management (Glen Dennison Triumf, Vancouver, BC, pers. comm., McAuley 2017), and a collaborative project between the MLSS, DFO Science, and Natural Resources Canada (NRCan) was initiated to map and characterize these glass sponge areas.

In September 2017, DFO Fisheries Management issued a letter to stakeholders asking for voluntarily avoidance of fishing in the 13 areas thought to be sponge reefs (DFO Fishery Notice FN1150, Appendix 1) and requested DFO Science Branch provide advice on the characteristics and the biological significance of the sponge reefs listed in the notice. This advice will be used during stakeholder consultation meetings planned for 2018.

The advice provided in this Science Response utilizes peer-reviewed and accepted methods of assessing current sponge reef status as previously described (DFO 2017, Dunham et al. 2018).

The specific objectives of this Science Response are to:

  1. Map the geological extent of the known reefs in Howe Sound using available multibeam bathymetry and backscatter data.
  2. Map and characterize the modern ecological extent (reef-building glass sponge cover) using available visual survey data.
  3. Characterize associated megafaunal communities.
  4. Characterize ecological function of the glass sponge reefs using best available knowledge on the reefs in Howe Sound and elsewhere along the coast of British Columbia.
  5. Provide advice on the potential benefits of protection.

The advice arising from this Science Response will be used to inform decisions regarding management and future monitoring of the sponge reefs in Howe Sound, as well as to respond to stakeholder requests for scientific information. It is expected to aid DFO Fisheries Management in implementing conservation-based fisheries closures as part of advancing OEABCM, as well as aid Canada's Marine Conservation Target commitment to protect 10% of Canada's coast by 2020.

This Science Response Report results from the Science Response Process of December 2017 on newly discovered Howe Sound glass sponge complexes: locations, status, and ecological significance assessment.

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