Ecology Of Anchovy Juveniles In The Bay Of Biscay 4 Months After Peak Spawning: Do They Form Part Of The Plankton?

No abstracts are to be cited without prior reference to the author.

In September 1998 and 1999 two multidisciplinary cruises in the Bay of Biscay took place within the frame of the International JUVESU project (FAIR CT97-3374) in order to understand the spatial distribution of anchovy early juveniles and its relation with the environment. The surveys, although not covering the entire spatial distribution of these juveniles, served to outline major features of their ecology. In both years small anchovy juveniles were encountered in wide offshore areas beyond the continental shelf of the mid south of the Bay of Biscay. In 1999 part of the mid north of the Bay was also explored resulting that juveniles started about 50 miles far from shore. All day around juvenile anchovy occupy the stratified less dense surficial waters. During day time they form schools of variable sizes which spread in surface layers during night time. In all the areas covered in the 1998 survey, small juvenile (mode of 5 cm.) were caught mixed with drifting schools of jellyfish. In 1999 the presence of jellyfish was far less intense than in 1998, but the mixing was still observable in some northern areas. In both years the surface waters effectively occupied by those juveniles had a relative low salinity level, denoting that those waters originated from shelf coastal areas close to river plumes, which are the most important spawning areas for anchovy in Spring. These observations suggest that early recruitment of anchovy occurs in drifting lens of low salty surface waters departing westwards from the coastal spawning areas due to wind advection in summer time in the Bay. By the time the surveys took place, four months after peak spawning, juvenile seem to be still imbibed in those masses of water, without a clear indication of independent motion from them.