Research Document 2018/060

Assessment update of White Hake (Urophycis tenuis, Mitchill 1815) in NAFO Division 3P

By Simpson, M.R., Miri, C.M., Mello, L.G.S., Colbourne, E., and H. Rockwood

Abstract

White Hakes in NAFO Subdivision 3Ps and Divisions 3NO constitute one biological stock that inhabits the southern Grand Bank and St. Pierre Bank of Newfoundland and Labrador. White Hake is subject to ongoing mortality in directed and bycatch fisheries conducted by Canada and other countries. Annual NAFO-reported landings from Subdiv. 3Ps for Canada averaged 603 tons in 1994-2002, increased to an average of 1,364 t in 2003-07 (following recruitment of a large Div. 3NOPs 1999 year-class to the fishery), then decreased to a  306 t average since 2009. The DFO-NL spring research survey abundance index for Subdiv. 3Ps White Hake ranged from 4.0 million (in 2008) to 15.1 million (in 2002) over 1996-2016, and averaged 7.6 million. In this period, biomass estimates ranged from 2,582 t (in 2009) to 10,294 t (in 2000), averaging 5,737 t. In 2017, the abundance index was 7.1 million, and the biomass index was 4,848 t. Although large episodic recruitment of Div. 3NOPs White Hake was observed in 2000, annual recruitment has remained at much lower levels since 2001. Since 2010, the relative fishing mortality index for Subdiv. 3Ps has remained below its 1996-2016 average. White Hake biomass and abundance indices for Subdiv. 3Ps increased over the past two years, and recent Canadian landings (averaging less than 400 t in this Subdivision since 2009) did not seem to negatively impact the Div. 3P portion of the stock.

Ecosystem signals observed in Subdiv. 3Ps in recent years indicated that structural changes are occurring, and overall ecosystem productivity may be low. Although the direct impacts of these changes on White Hake life stages (i.e., pelagic eggs and larvae, bottom-dwelling juveniles and adults) are unknown, they imply that at least some aspects of White Hake productivity may be affected.

Investigations of Limit Reference Points for this species were previously conducted using several models on the Div. 3NOPs White Hake stock. During its June 2015 Meeting (and reiterated in June 2017), NAFO Scientific Council concluded that none of these assessment models were capable of adequately capturing the episodic nature of White Hake recruitment in Div. 3NOPs and, therefore, proposed limit reference points were rejected. It was thus inappropriate to establish them for Subdiv. 3Ps (or for any subcomponent of this stock).

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