Distribution and ecological aspects of leptocephali collected 1979–1994 in North- and Central Atlantic. I. Congridae

Abstract

This is the first report on the leptocephalus catches made during the last 15 years in North-and Central Atlantic during the course of 19 cruises of five different ships from Germany and one from Poland. This report comprises identification, geographical occurrence and abundance and in some cases depth preference, migratory routes and spawning area of Congridae in the North Atlantic. The largest part of this collection consists of 876Conger conger larvae. The likelihood that this species spawns in the Mediterranean is again confirmed. Decreasing density as well as increasing size from Gibraltar west-and north westward showed migration to be occurring in that direction. Age was determined by counting “daily rings” on the otoliths of up to 120-mm long larvae. It is suggested to be more than 300 days and is calculated to be 1 1/4 years for the largest larvae (TL=140–160 mm). Some 126 specimens of three otherConger species, i.e.C. oceanicus, C. triporiceps, C. esculentus, were identified in the collection. The major part originated from the western North Atlantic. The most numerous larvae, belonging to another genus of Congridae, wereAriosoma balearicum (n=265). They showed, also in consideration of other studies, quite a wide range in number of myomeres. Their systematic status is therefore uncertain, as is also the status of those known from the NW Indian Ocean and the NW Pacific. One larva, probably ofAriosoma selenops, of un-usually large size (TL=467 mm) and captured in the Iberian Basin is described and compared with specimens known from the literature. Two larvae of unknown identity were captured off NW Africa; they resembledA. balearicum but had too high a number of myomeres. The identity of most of theGnathophis larvae caught in the East Atlantic is uncertain. Leptocephali ofParaconger notialis in the East Atlantic, up to the area north of New Guinea, exhibited a higher number of myomeres than those known from the West Atlantic. Larvae ofXenomystax congroides (n-29), belonging to a population with a relatively high number of myomeres, were captured in the Sargasso Sea.