Research Document - 2015/076
Review of White Hake (Urophycis tenuis) in the Northern Gulf of St. Lawrence in Support of a Recovery Potential Assessment
By Claude Nozères, Johanne Gauthier, Hugo Bourdages, and Yvan Lambert
Abstract
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed White Hake in Canadian waters, and based on a combination of genetic, behavioural (spawning locations and seasons), and meristic information suggested the existence of two populations (designatable units (DUs)). The definition of geographic boundaries between these two populations is complicated because of spatial overlap in their distribution. One population named the Southern Gulf of St. Lawrence (DU1) encompasses all of NAFO Div. 4T and the northern portion of Subdivision 4Vn. The second population identified as Atlantic and northern Gulf of St. Lawrence (DU2) includes the Scotian Shelf (NAFO Div. 4VWX), waters off southern and eastern Newfoundland, northern Gulf of St. Lawrence (NAFO Div. 4RS) as well as waters greater than 200 m in NAFO Div. 4T. The areas of overlap are: along the southern edge of the Laurentian Channel in NAFO Div. 4T at depths greater than 200 m and within NAFO Subdiv. 4Vn.
The Atlantic and northern Gulf of St. Lawrence population was designated as threatened in November of 2013. The reason provided by COSEWIC for this designation is:
- Adults in this population are estimated to have declined by approximately 70% over the past three generations. Most of this decline occurred before the mid-1990s. The population has remained fairly stable since then, and there has been little overall trend in area of occupancy. Restrictions on fisheries since the mid to late 1990s over most of their range may be responsible for stabilizing their numbers.
Following on the COSEWIC assessment, Fisheries and Oceans Canada (DFO) Science Branch was asked to undertake a Recovery Potential Assessment (RPA) for the White Hake populations assessed as threatened or endangered. This Research Document supports the RPA for the Atlantic and northern Gulf of St. Lawrence DU (ANGSL). It describes the current state of knowledge of White Hake in the northern Gulf of St. Lawrence (nGSL) portion of the ANGSL DU in terms of its biology, ecology, abundance, distribution and trends, habitat requirements and threats. Main sources of data were DFO and industry surveys, commercial landings, at-sea observer data, and stomach content databases. White Hake in the nGSL is not considered as a separate stock. There is no established directed fishery and it is not assessed under a regional peer review process. Limited information is available on White Hake in the nGSL. The species is broadly distributed in water depths between 175 and 350 meters, with concentrations along the slope of the channels of the nGSL. An index of abundance, based on data from the DFO RV summer survey, was developed for this RPA. This index, estimated for the 1985-2014 period, indicates that the abundance of White Hake in the nGSL declined rapidly from the mid 80s to early 90s, and has since remained at low levels. The information contained in this document may be used to support the development of recovery plans and decision-making with regard to the issue of permits, agreements and related conditions under the SARA.
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