EFFECT OF A SHELF SLOPE FRONT ON THE SPATIAL-DISTRIBUTION OF MESOPELAGIC FISH LARVAE IN THE WESTERN MEDITERRANEAN

The results of a study on the spatio-temporal distribution of mesopelagic fish larvae off Catalan coast (northwestern Mediterranean) in relation to the hydrographic features in the region are presented. Large concentrations of larvae were detected over the edge of the continental shelf and occasionally close inshore. Shelf structure, locally narrow and punctuated with submarine canyons, and a density front situated over the slope are responsible for the special characteristics of the region and for the presence of mesopelagic fish larvae in waters shallower than normally expected in view of the typically oceanic habitat of the adults. The density front contributes to the formation of larval concentrations, attributable both to passive transport of larvae and to the active mechanism of spawning by adults in the most productive areas. Certain species, like Cyclothone braueri and Maurolicus muelleri, exhibit marked seasonality in their spawning season, whereas others, like Myctophum punctatum and Benthosema glaciale, do not present well-defined spawning periods. © 1990.