Red Méthot1, Martin Castonguay, Yvan Lambert
1Present address: Alliance Environnement, 337 Boul. La Salle, Baie-Comeau, Quebec, Canada G4Z 2Z1
Pêches et Océans Canada, Institut Maurice-Lamontagne, C.P. 1000, Mont-Joli, Quebec, Canada G5H 3Z4
Institut des Sciences de la Mer de Rimouski, Université du Québec à Rimouski,
310 Allée des Ursulines,
Rimouski, Quebec, Canada G5L 3A1
Steven E. Campana
Fisheries and Oceans Canada, Bedford Institute of Oceanography, P.O. Box 1006,
Dartmouth, Nova Scotia, Canada B2Y 4A2
Publication (Upload) date: 14 Oct 2005
Méthot, R., M. Castonguay, Y. Lambert, C. Audet, and S. E. Campana. 2005. Spatio-temporal distribution of spawning and stock mixing of Atlantic cod from the northern Gulf of St. Lawrence and southern Newfoundland stocks on Burgeo Bank as revealed by maturity and trace elements of otoliths. J. Northw. Atl. Fish. Sci., 36: 31–42. doi:10.2960/J.v36.m564.
Atlantic cod (Gadus morhua) from the northern Gulf of St. Lawrence stock (NAFO Subdivisions 3Pn and Divisions 4RS) overwinter in deep waters east of Cabot Strait. During winter and spring, cod from this stock mix with fish from the southern Newfoundland cod stock (NAFO Subdiv. 3Ps), especially on Burgeo Bank. However, the degree and exact period of mixing are not known. The reproductive activity of female cod in the northern Gulf and on Burgeo Bank was examined to identify spawning areas, timing of reproduction, and stock mixing. From April to July 2001, spawning was studied visually (n = 2 129 adult females) and histologically (n = 450 adult females) by following monthly changes in the frequency distributions of maturity stages of female cod. Spawning was more advanced in the northern Gulf than in the other areas in April. Few spawning females were caught during the study on Burgeo Bank, indicating that this region was not a major spawning area in spring 2001. The relative frequencies of fish in spawning condition in April and May were different between Burgeo Bank (Subdiv. 3Ps) and the Gulf (Subdiv. 3Pn and Div. 4R). Trace element analyses of otoliths of maturing females collected on Burgeo Bank in late April were used to determine their stock origin. Otoliths of spawning females from the northern Gulf and Burgeo Bank were used as reference groups. The trace element results indicated that a substantial fraction (41–52%) of the maturing female cod sampled on Burgeo Bank in late April 2001 originated from the northern Gulf of St. Lawrence stock.
Key words: Burgeo Bank, distribution, Gadus morhua, Gulf of St. Lawrence, otoliths, sexual maturity, spawning stock, stock mixing, southern Newfoundland.