Research Document - 2004/029

Assessment of the NAFO Division 4T southern Gulf of St. Lawrence herring stocks in 2003

By LeBlanc, C.H., Poirier, G.A., Chouinard, G.A., MacDougall, C., Bourque, C

Abstract

A population analysis was conducted on the 2003 4T herring spring spawner component using sequential population analysis. The analysis included the gillnet catch rates abundance index and the acoustic survey index, using intrinsic weighting. The estimated F_0.1 catch for the spring spawner component in 2004 was 17,000t. A catch of 13,500t corresponds to a 20% chance of exceeding F_0.1. Reported 2003 landings of the spring spawner component were 8,450t against a TAC of 11,000t. Mean inshore gillnet catch rates in 2003 were slightly higher than 2002 but remain at a low level compared to the early 1990s. Most year-classes produced after 1991 are estimated to be below average. The 1997 year-class appears to be above average. The 1999 year-class (age 4 in 2003) was estimated for the first time in this assessment and appears above average. Age 4+ spawning biomass has declined since 1995 and is estimated to be 65,000t at the beginning of 2004. The exploitation rate of fully recruited ages 6 to 8 was below the target in 2003.

The 2003 assessment of 4T herring fall spawner component was based on a sequential population analysis using an abundance index based on gillnet catch rates. After adjusting for the tendency to overestimate population numbers, the estimated catch at F_0.1 for 2004 is 77,500t. A catch of 67,000t corresponds to a 20% chance of exceeding F_0.1. Reported 2003 landings of the fall spawner component were 58,821t against the fall spawner TAC of 62,000t. There was no fishery in the 4Vn (Area 17) overwintering area. Mean inshore catch rates in 2003 were slightly less than 2002, but remain at a high level in the time series starting in 1978. The 1995, 1996 and 1998 year-classes are estimated to be well above average. Estimates of population biomass and abundance are currently high; however, retrospective patterns indicated a tendency to overestimate the size of the biomass in the current year. The age 7+ exploitation rate in 2003 is estimated to be below the target.

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