BIOTIC RELATIONSHIPS OF ILLEX-COINDETII AND TODAROPSIS-EBLANAE (CEPHALOPODA, OMMASTREPHIDAE) IN THE NORTHEAST ATLANTIC - EVIDENCE FROM PARASITES

Parasites were collected from 1,200 short-finned squid (Illex coindeti i, Tedaropsis eblanae) caught as by-catch in a multispecies trawling f ishery in the northwest Spanish Atlantic waters in 1992-1993. Parasite s found included six species of helminths, three tetraphyllidean cesto des (Phyllobothrium sp.,Pelichnibothrium speciosum, Dinobothrium sp.), two trypanorhynchidean cestodes (Nybelinia yamagutii, Nybelinia lingt ralis), and one ascaridoid nematode (Anisakis simplex B). Two of these parasites (Phyllobothrium sp., A. simplex B), which could be recognis ed as component species, were used in analyses of host-parasite relati onships. Levels of infection varied significantly with host size or st age of maturation for both squid species. Regional variation in infect ion level seems attributable to geographical variation in availability of prey, discreteness and movements of host populations and to size o r age-related changes in the prey selection of their host. Parasite ev idences suggest that both ommastrephid squids are sympatric species sh aring similar econiches, and serve as diet for large top predators (se lachians and marine mammals) of Northeast Atlantic. Parasites may also be useful as an indirect indicator of the migratory habits of the squ id.