Research Document - 2000/021
The Atlantic mackerel (Scomber scombus L.) of NAFO Subareas 3-4.
By Grégoire, F. (Éditeur / Editor)
Abstract
This document has been written to present the most recent data on the Atlantic mackerel (Scomber scombrus L.), including the fishery for this species, the assessment of its abundance, and certain research projects concerning it. A highly migratory, warm-water species, the Atlantic mackerel is the target of a commercial fishery that takes place along the coast of New England in winter and extends to the mackerel's spawning and feeding grounds which, in Canadian waters, are located chiefly in the Gulf of St. Lawrence. It is also in this location, and more specifically in the southern part of the Gulf, that an abundance survey has been conducted by means of egg sampling.
The commercial mackerel fishery is essentially an inshore fishery, and its importance can be measured by the very large number of fishermen who participate in it. The main types of gear used by fishermen in the Maritime provinces and Quebec are gillnets, lines, traps, purse seines, and weirs. Foreign vessels engage in an offshore fishery on the Scotian Shelf, but the importance of this fishery has greatly diminished since the 1977 introduction of a 200 nautical mile economic exclusion zone. Chapters 1 to 3 of the present document update the data on and describe the mackerel catches made over the past several years by Canadian and foreign fishermen in Canadian and U.S. waters.
Chapter 4 of this document presents the main criteria for identifying the mackerel eggs sampled in the abundance surveys in the southern Gulf. Chapter 5 provides a detailed assessment of the mackerel's abundance based on the egg samples from the 1998 survey. Chapter 6 proposes a method for calculating the variance and the confidence intervals for these abundance estimates.
Over the past few years, various research projects have been carried out to improve mackerel abundance estimates. One of these methods, presented in Chapter 7, consists in using kriging to determine the average densities of eggs per unit area. Another project, described in Chapter 8, presents the results of the Daily Fecundity Reduction Method (DFRM). This method can be used to calculate spawning biomass not from annual egg production figures, which is the traditional approach, but rather from daily production figures. Some research projects have also been carried out in co-operation with the industry, and Chapter 9 presents the preliminary results of an exploratory survey in which mackerel eggs were sampled from a fishing vessel in St. Margaret's Bay in Nova Scotia. Chapter 10 presents updated Canadian catch at age figures for Atlantic mackerel for the period 1990 to 1998. Lastly, Chapter 11 presents the main results for the 1999 Atlantic mackerel fishing season.
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