Biological characteristics of northern shrimp (Pandalus borealis Kroyer) in areas off Labrador

Parsons, D. G.(Donald Gordon) (1982) Biological characteristics of northern shrimp (Pandalus borealis Kroyer) in areas off Labrador. Masters thesis, Memorial University of Newfoundland.

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Abstract

Northern shrimp (Pandalus borealis) occurring in the Hopedale, Cartwright and Hawke channels off the Labrador coast were examined. Based on results from research surveys from 1979-81, distribution was concentrated in water between 2 and 4°C in depths greater than 300m. Changes in distribution and abundance were also observed between years. Density and abundance appeared to have decreased in the Hopedale and Hawke Channels during this period, while in the Cartwright Channel only changes in density distribution were noted. Variations in catch rate over a 24 hour period were related to vertical migration of shrimp and the effects of tidal currents on shrimp distribution and performance of sampling gear were discussed. Biological characteristics such as sex and maturity, weight-length relationships, fecundity and food and feeding were examined. Generally, shrimp in these areas appeared to be obligatory protandric hermaphrodites. Sex change occurred over a range of sizes which may vary with changing environmental parameters or fishing mortality directed at the larger female shrimp. Weight-length relationships were similar to those reported for conspecifics in other areas of the northern hemisphere. Fecundity of shrimp off Labrador appeared to be less than that reported in warmer regions but greater than that observed in colder water populations. Food and feeding patterns were similar to those demonstrated for other northern shrimp stocks. Statistical and descriptive comparisons of the above characteristics indicated differences between channels which, in some cases, may represent different stock characteristics. Infection of shrimp eggs by a tentatively identified dinoflagellate represents potential for egg mortality and spawning failure. Necrosis of striated muscle of shrimp was associated with infections by a microsporidian, possibly of the genus Thelohania.

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