Research Document - 2010/004

Assessment of the Status, Threats and Recovery Potential of Cusk (Brosme brosme)

By L.E. Harris and A.R Hanke

Abstract

In May 2003, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed cusk (Brosme brosme) as threatened. Cusk are currently under consideration for addition to Schedule 1 of the Species at Risk Act (SARA). The recovery potential assessment (RPA) will inform the listing decision, socio-economic analyses, and consultations with the public. Should this species be legally listed as threatened or endangered, the RPA will also inform the recovery strategy.

Cusk abundance has declined since the 1970s; however, there are insufficient data to determine the degree of decline. There is conflicting evidence as to whether cusk abundance has continued to decline since the late 1990s. There has been no reduction in the range of cusk in Canadian waters. Cusk do not seem to have disappeared from any areas where they have been caught historically.

A reasonable strategy for recovery would be to achieve an increasing trend in abundance, as measured by an appropriate index. A reasonable spatial target would be to avoid any human-induced reduction in range and distribution. Fishing is the only known major source of human-induced mortality for cusk. Canadian cusk landings from the North Atlantic Fisheries Organization (NAFO) divisions 4VWX and subarea 5 have ranged from 790 metric tonnes (t) to 1490t between 1999 and 2006. The majority of these landings are from the groundfish longline fishery in 4X and 5Z. Minimum cusk mortalities in lobster fisheries were estimated to be 226t in Lobster Fishing Area (LFA) 34 in 2005/2006 and 22t in LFA 41 in 2005/2006, and 169t in LFA 34 in 2006/2007.

Adult cusk prefer structured, hard bottom habitat and a depth range of 400m to 600m. The preferred habitat of juvenile cusk is not known. Habitat does not appear to be, nor is likely to become, a limiting factor to cusk survival and recovery. There are no known threats that have reduced cusk habitat quantity or quality.

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