Distribution and abundance of european hake merluccius merluccius (l.), eggs and larvae in the north east atlantic waters in 1995 and 1998 in relation to hydrographic conditions

Abstract

Plankton samples from surveys in 1995 and 1998 were analysed in order to study the spatial distribution of hake (Merluccius merluccius) eggs and larvae. The cruises covered an extensive area from the south of the Bay of Biscay to the north-west of Ireland. This spatial distribution has been interpreted in relation to the direction and intensity of the dominant winds. An important decrease of eggs (69%) and larvae (27%) was observed from 1995 to 1998. Hake showed continuous spawning from February to July in the area. The centroids of hake egg distribution indicated a northward displacement of the peak of spawning as the season progresses. Spawning of hake was located close to the 200 m depth isobath in the southern area (Bay of Biscay) and it spread over the shelf in the area of the Celtic Sea. Eggs were most abundant at 20 m depth temperatures between 12 and 12.5degreesC. The centroids of hake larvae distribution also showed a northward displacement although not as strong as that of hake eggs. The spatial distribution of hake larvae by size ranges showed important differences between years: in 1995 it suggested inshore transport of larvae, from the spawning areas (close to the 200 m depth isobath) to nursery areas (closer to the coast) while in 1998 it suggested offshore transport. This transport does not correspond with the general wind regimes during those years. Therefore it is concluded that the transport of the hake larvae to nursery areas must be controlled by different hydrographic mechanisms such as geostrophic currents in the Bay of Biscay and tidal currents in the northern areas.