Depth Distributions of Various Stages of Witch Flounder (Glyptocephalus cynoglossus) off Nova Scotia and in the Gulf of St. Lawrence

Abstract

Larvae, juveniles, and adults of witch flounder off Nova Scotia and in the Gulf of St. Lawrence were found to occupy largely discrete niches. The only larvae found (up to 3.8 cm long and presumed to be under 1 year old) were taken at depths of from 0 to 20 fath (0 to 36 m). Fish newly metamorphosed and up to 30 cm long (5 years old) were caught mainly at 100–160 fath (180–288 m). Adults were taken in summer at 20–150 fath (36–270 m) and in winter at 50–240 fath (90–432 m), suggesting that seasonal movements may take place. The centres of abundance of adults were delineated, but not of larvae or juveniles.It is inferred that the deepwater distribution of young witch flounder prevents direct food competition with young of the more abundant species, cod and American plaice, on the continental shelf areas. Barring unforseen exploitation of the deepwater nursery grounds, witch flounder possess a natural conservation mechanism because of the niche separation between juveniles and adults.