Biology of the conger eel Conger oceanicus in the Mid-Atlantic Bight - I. Distribution, age, growth and reproduction

Conger oceanicus sampled in 1980 to 1983 from the tilefish longline fishery in Mid-Atlantic and southern New England regions of the USA were supplemented with inshore samples caught by small-meshed trawl. The total lengths (TL) of conger eels caught by longline were larger (48 to 123 cm TL) than eels taken by trawl (18 to 67 cm TL). Because males were smaller than all but the smallest females seen in the fishery (<50 cm TL), the absence of males from the offshore longline catch was attributed to gear selection. Conger eel catch rates in the longline fishery were highest in winter. Otoliths were used to age conger eels and to determine back-calculated length at age. Validation of annulus formation was difficult because a multiple banding pattern occurred and otolith shape was variable. The otolith data indicated that size at a given age was highly variable. Gross morphologies of the gonads were similar to those described for Anguilla spp. Ovaries had "frills" on the distal surface and gonia >20 μm in diameter in histological sections. Males were distinguished by the presence of gonia in well-defined crypts. Female ovaries were characterized by having either oocytes in a previtellogenic condition, or oocytes undergoing vitellogenesis together with adipose cells. In females >85 cm TL, the most mature individuals (those having a high gonosomatic index and mean maximum oocyte diameter) occurred during the late spring and early summer. The absence of ripe or spent female conger eels in Mid-Atlantic and southern New England regions suggests that they leave the region to spawn, probably in the Sargasso Sea.