ALLOPATRIC SPECIATION OF THE TEUTHID FAUNA ON THE SHELF AND SLOPE OF NORTHWEST AFRICA

Abstract

Habitats and life cycle strategies of nektonic squid of genera Alloteuthis, Loligo, Illex, Todarodes, Todaropsis, and Sthenoteuthis, occurring off the Northwest African coast are described. The teuthofauna of the region consists of a mixture of boreal and tropical species, each associated with its specific water mass. Both boreal and tropical squid inhabit the ecotone zone, the main features of their life styles are common to that of the central part of their species ranges. Boreal species inhabit cold waters of either Sahara or Canary Currents, or inshore upwelling waters. They have the winter peak of the spawning. Species, which ranges extend into tropics, inhabit waters of tropical origin and tends to stay off the upwelling activities. As their southern counterparts, these species have a spring-summer peak in their spawning. In squid assemblage, fecundity increased about ten-folds at each step from the inner shelf to the shelf break and slope, and then to the open ocean. Egg size decreased in the same direction. The possible reason is an increase in mortality at early stages that forces species to produce more eggs at cost of egg size and offspring quality.