Deep-Water Corals in Atlantic-Canada: A Review of DFO Research (2001–2003)
Gordon, Donald C. Jr.
Kenchington, Ellen L.R.
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Deep-water corals occur in Atlantic Canada at water depths in the general range of 200-1500 m. Prior to 2000, most knowledge of deep-water corals was anecdotal and based primarily on fishing bycatch information. During 2001-2003, in collaboration with university colleagues, the Department of Fisheries and Oceans (DFO) at the Bedford Institute of Oceanography investigated the distribution, abundance, habitat and biology of deep-water corals and their associated fauna under funding provided in part by the Environmental Studies Research Fund. Data were gathered from DFO groundfish surveys, the Fisheries Observer Program, interviews with fishers and dedicated research cruises with specialized imaging and sampling equipment. Nineteen coral taxa were collected or observed alive in their natural habitat; 6 Alcyonacea (soft corals), 7 Gorgonacea (horny corals), 5 Scleractinia (stony corals), and 1 Antipatharia (black corals). The results confirmed earlier observations that the Northeast Channel, the Gully and the Stone Fence are prime coral habitats. The first documented Lophelia reef complex in Atlantic Canada was found near the Stone Fence in the mouth of the Laurentian Channel. The distribution of deep-water corals is patchy and influenced by several environmental factors including substrate, temperature, salinity and currents. The average height of Primnoa and Paragorgia colonies was 30 and 57 cm. At their estimated growth rates of 1.7 and 1 cm /year, respectively, the largest Primnoa colony observed was about 61 years old while the largest Paragorgia colony was about 180 years old. Deep-water corals host a rich associated fauna, and 114 taxa have been identified to date on Paragorgia and Primnoa in Atlantic Canada. Numerous species of fish have also been observed associated with deep-water corals, the most abundant being redfish. Damage from fishing gear was found to be most extensive at the Lophelia reef complex at the Stone Fence. A lower level of fishing damage was observed in the Northeast Channel while few indications of damage were observed in the Gully. The results of this program have been used by DFO to create coral conservation areas at the Northeast Channel (424 km2) and Stone Fence (15 km2) that are closed to bottom-fishing activities. Substantial knowledge gaps still exist, in particular quantitative information of deep-water corals at depths below 500 m, and these are being addressed by continuing collaborative research by DFO and universities.