Research Document - 2007/016

Assessment of the NAFO Division 4T southern Gulf of St. Lawrence herring stocks in 2006

By LeBlanc, C.H., G.A. Poirier, C. MacDougall, C. Bourque and J. Roy

Abstract

Assessments of the spring and fall spawning herring from the southern Gulf of St. Lawrence are required on an annual basis and form a part of the information base used to establish the total allowable catch (TAC).

A population analysis was attempted on the 2006 4T herring spring spawner component using sequential population analysis. The analysis included the age-disaggregated gillnet catch rate (CPUE) and acoustic survey indices, plus the telephone survey abundance opinion as an aggregated biomass index. The model fit was unreliable and was rejected as a true indicator of current biomass levels. The 2006 landings of the spring spawner component in both the spring and the fall fisheries were 2,148t against the spring spawner TAC of 9,000t. Mean inshore gillnet catch rate in 2006 was the lowest in the series that starts in 1990. The 2006 acoustic survey index of abundance remains near the lowest in the series that starts in 1994. The 2006 abundance index of spring herring calculated from the opinions of harvesters contacted in the telephone survey was the lowest in the time series that starts in 1987. To describe stock status, emphasis was put on the continued decline in the abundance indices and the inability to catch the TAC in recent years. The model estimate of age 4-10 biomass (35,500t), which is considered an overestimate, is well below the Upper Stock Reference (USR) of 54,000t. Consistent with the precautionary approach, harvesting strategies that promote rebuilding should be adopted. Catch levels in 2007 should be less than in 2006.

The 2006 assessment of 4T herring fall spawner component was based on a sequential population analysis calibrated on both the age-disaggregated gillnet catch rate (CPUE) index and the telephone survey abundance opinion as an aggregated biomass index. The model outputs were accepted as current indicators of stock status. Reported 2006 landings of the fall spawner component in both the spring and the fall fisheries were 52,214t against the fall spawner TAC of 68,800t. Mean inshore gillnet catch rates in 2006 were the highest in the time series that starts in 1978. The 2006 abundance index of fall herring calculated from the opinions of harvesters contacted in the telephone survey was the highest in the time series that starts in 1987. Recruitment estimates from the model analysis indicate that the 1995, 1998 and 2000 year-classes are above average. The 2007 beginning-of-year Age 4+ spawning biomass is estimated to be about 316,100t, well above the Upper Stock Reference of 172,000t, and remains amongst the highest since 1978. The fully recruited (Age 5+) exploitation rate in 2006 was below the F0.1 target. The catch at F0.1 for 2007 is 75,500t.

Complete document (PDF, 1934 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.