Research Document - 2006/005

Status of witch flounder in NAFO divisions 4RST, February 2006

By Swain, D.P., and R.B. Morin

Landings of witch flounder in NAFO Divisions 4RST are mostly by seiners directing for witch flounder between May and October in St. George’s Bay, Newfoundland (4Rd) and off the west coast of Cape Breton Island (4Tf and 4Tg). Landings declined in the 1990s, reaching historical lows between 1994 and 1997. The low landings in 1994-1997 reflected a sharp decline in effort in 4R during this period. Effort increased after 1997 and landings increased to the TAC (800-1000 t) in 1998-2000. Landings in 2005 were 928 t, near the TAC of 1000 t.

The research vessel (RV) survey biomass index for commercial sizes (30+ cm) over the entire 4RST area decreased to low values in the mid 1990s. This decline was mostly confined to the 4R, 4S and western 4T areas. The biomass index in eastern 4T has been at a relatively high level since the mid 1990s. Over the entire 4RST area, relative biomass increased sharply from a low level in 1998 to an intermediate level in 1999 and 2000, but has decreased since then. The index in 2005 was 80% of the 1987-2005 average. The abundance of large fish over 45 cm in length appears to be very low compared to the abundance in the 1970s and early 1980s. In contrast to the RV survey, catch rates in the July sentinel survey of the northern Gulf provide no indication of an increase in biomass since the mid 1990s.

Although a strong yearclass appeared in the survey catches in the mid to late 1990s, growth rate has been slow for this yearclass, and its eventual recruitment to commercial sizes has not resulted in the anticipated increase in biomass at these sizes. Little trend in fishing mortality is evident over the 1987 – 2005 period. Biomass changes over this period do not appear to be attributable to effects of fishing alone. Nonetheless, it appears that biomass has again started to decline following its partial recovery in the late 1990s, and landings near 1000 t may not be sustainable at this stock’s current low level of productivity.

Complete document (PDF, 2 351 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.