Research Document - 1999/054
An Assessment of the NAFO Division 4T Atlantic Herring Stock 1998.
By R.R. Claytor and C. LeBlanc
Abstract
The F0.1 spring spawner fishing level for 1999 is 18,500t. This estimate is above the 13,000t projected for 1999 from the 1998 assessment. Reported 1998 landings of spring spawners were 15,653t compared to a TAC of 16,500t. Inshore catch rates calculated form the New Brunswick market co-ordinator program in Escuminac and southeast NB indicated a slight decrease in the overall abundance from 1997 to 1998. However, there was an increase in abundance of ages 4, 5, and 7. These catch rates are at the higher levels of the time series. The 1991 year-class is dominant in the population at this time; the incoming 1994 year-class is slightly above average, and age 4+ spring spawner biomass is above average at 86,000t in 1998. The age 4+ fishing mortality has been very close to the target exploitation rate of 24% in recent years. Abundance of herring that spawn during the spring in Chaleur Bay has declined during the last five years and continued to be low in 1998.
The best estimate of the F0.1 fall spawner fishing level for 1999 is 60,500t. This level takes into account the tendency to over-estimate age 4 fall spawners. The 1993 year-class, which was estimated last year to be the highest since 1978, was estimated in this assessment to be above average and the fourth highest in the time series. The most recent year-class (1994, 4 year-olds) is now estimated to be the highest in the time series and is 38% of the 400,000t estimated age 4+ biomass in 1998. Without correcting for the tendency to over-estimate four year-olds, the 4+ biomass was the highest in the time series and the F0.1 fishing level for 1999 would be 67,500t. Other indicators of fall spawner biomass do not support the estimate that 1998 4+ biomass is the highest in the time series. The acoustic and bottom trawl survey indices are at moderate levels and opinions of abundance expressed during the phone survey of the inshore fleet generally indicated declines in abundance from 1997 to 1998. Inshore catch rates were similar in 1997and 1998, and while not the highest in the time series, were above average. Reported 1998 landings of fall spawners were 43,023t compared to the fall spawner TAC of 54,248t. A major change in the fall fishery in 1998 was the lowest recorded catch (<100t) in the 4T overwintering fishery in 4Vn. Participants in the fishery reported that these low catches were the result of herring being inaccessible to the gear, rather than a problem with abundance. The age 4+ fishing mortalities have been below the target exploitation rate for each year since 1981, except for 1990 and 1995.
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