Atlantic Fisheries Research Document 1996/119

Euphausiids the on eastern continental shelf

By D. Sameoto; N. Cochrane

Abstract

Three species of euphausiids are commonly found on the continental shelf of the Maritime Region, Thysanoessa rashii, T. inermis and Meganyctiphanes norvegica. M. norvegica is the largest of the three species reaching a maximum length between 3 and 4 cm and is the target species for commercial exploitation. M. norvegica lives up to three years, but the majority of the animals will not live past two years of age. They mature at age one year with breeding occurring in late June and early July after which time many of the adults die. All species of euphausiids have diurnal migration and are found in the top 50 m during the night and in deeper water during the day. M. norvegica prefers water depths greater that 200 m during the day and as a result they are concentrated in the basins of the Scotian Shelf. This allows an accurate estimate to be made of their population size. The population size and biomass are estimated with the use of multifrequency acoustics and special sampling gear. In Emerald Basin, on the Scotian Shelf, the population biomass of M. norvegica for the period 1984 to 1996 has shown large year to year fluctuations. The estimated average biomass standing stock of M. norvegica in Emerald and La Have Basins for June during the above period is over 52,000 mt, and for the entire Scotian Shelf and slope is over 123,000 mt.

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