Distribution and seasonality of mackerel (Scomber scombrus L. ) in the Cantabrian sea and Galician waters (ICES division VIIIc and sub-division IXa North)

Abstract

The present poster describes the seasonality and distribution areas of mackerel (Scomber scombrus, L.) in the Cantabrian Sea and Galician waters (Division VIIIc and Sub-Division IXa North) based on commercial catches, and bottom trawl and egg surveys. The catch distribution indicates that most of the catches occur in the eastern part of Division VIIIc with a peak in the months of March and April made up of adult fish (>2 years), and in June these fishes disappear from the area. In the central and western area (VIIIc C and VIIIc W) catches also occur in the first and second quarter of the year with a peak in April, though at a lower level than in the east, made up mainly of adult fish and with a small quantity of juveniles (ages 1 and 2). In the third and fourth quarters of the year the catch decreases and is made up of fish born that year (age 0), mainly in the central part of Division VIIIc, and of juveniles (ages 1 and 2). In Subdivision IXa North catches show a progressive increase from July to September composed of juveniles, mainly age 0. Spawning occurs in spring and the abundance of eggs peaks in April (Sola et al., 1990, 1994) over the continental shelf and outside, with greater egg abundance to the south of 44° 30'N in the central and western area of Division VIIIc (Lago de Lanzos et al., 1993). The spawning season (mainly March and April) coincides with the peak of commercial catches in the area. Western stock mackcrel also spawn in spring and the spawning area extends from the north coast of Spain in the Bay of Biscay towards the Porcupine Bank to the west of Ireland (Lockwood, 1988) and spawning commences in Biscay in February or early March (Dawson,1986). The mean distribution of juveniles in Autumn (age 0) from bottom trawl surveys indicates two main centres of distribution, a large one Sub-Division IXa North (IXa N) and a lesser one in the central area of Division VIllc (Vlllc Cl. The distribution of ages 1 and 2 in Autumn is mainly in Sub-Division IXa North (IXa N). In view of the results obtained it could be concluded that mackerel adults (>2 years) come to the north of the Iberian peninsula to spawn in March and April, reaching the area by the eastern part of the Bay of Biscay. The adult fish disappear drastically from the whole area in June. In the third and fourth quarters fish born in the same year (age 0) stay in the area and juveniles (ages 1 and 2) seem to remain in the central part of Division VIIIc and in Galician waters (Subdivision IXa North).