State of sexual maturity of Atlantic salmon (Salmo salar L.) caught at sea, in commercial fisheries off Newfoundland

Mullins, Conrad (1995) State of sexual maturity of Atlantic salmon (Salmo salar L.) caught at sea, in commercial fisheries off Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The state of maturity of male and female Atlantic salmon harvested at sea during 1990 and 1991 at three sites in Newfoundland was investigated. Salmon landed at St. Barbe Bay, Conche and Twillingate were sampled throughout the commercial fishing season (June - August). The methods used to determine the state of maturity in male and female salmon were histological examination of gonadal development and radioimmunoassay of plasma steroid hormone levels. The gonad stage development, gonadosomatic index (GSI), hepatosomatic index (HSI), condition factor (CF), testosterone (T), 11-ketotestosterone (11-KT), vitellogenin (Vg) and 17β-estradiol (E2) levels measured in commercially caught salmon were compared with those of cage-reared and wild salmon of known background to verify the maturity classifications. Stages of gonad development, the levels of T, E2, 11-KT, Vg, and GSI, HSI and CF measured in male and female salmon of known state of maturity were used to develop discriminant functions for predicting the state of maturity in commercially caught salmon. Salmon sampled in St. Barbe Bay in the Gulf of St. Lawrence were 100% spawners-of-the-year, whereas, samples from Conche and Twillingate on the northeast coast of Newfoundland consisted of salmon that would not have returned to their native rivers to spawn. Differences in biological characteristics of salmon from the commercial fishery locations tend to support the maritime origin of the non-maturing component of commercial landings in Newfoundland. Male and female Atlantic salmon that are not spawners-of-the-year can be recognized by discriminant analysis techniques on the basis of the stage of gonad development, plasma hormone levels, and GSI.

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