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WALSH, G., Y. LAVERGNE, 1991. Sédimentation et dispersion des déblais de dragage en mer et effets sur la moule bleue (Mytilus edulis) en élevage dans la baie des Chaleurs. Pages 55-73 in Atelier de planification sur les mollusques et la pollution marine, les 12-13 septembre 1990, Percé. Ministère de l'agriculture, des pêcheries et de l'alimentation, Québec .
BERGERON, P., M. FRÉCHETTE, L. PAGÉ, Y. LAVERGNE, G. WALSH, 1990. Sédimentation et dispersion des déblais de dragage en mer et effets sur la moule bleue (Mytilus edulis) en élevage dans la baie des Chaleurs. Rapp. tech. can. sci. halieut. aquat., 1746, 59 p .
Dredging operations conducted along the wharf in Carleton and Saint-Godefroi yielded respectively a total of 1,903 and 3,660 m3 of deposits. This material was dumped offshore approximately 2,5 nautical miles from the coast and its dispersal was monitored with an echosounder and a transmissometer along compass courses radiating from the dumping site. Water transparency was analyzed along with data collected on grain-size frequency distribution, current speed and direction in order to estimate dispersal rates and sediment motions. A maximal reduction of 47,2 % of initial water transparency was recorded within 50 m of the dumping site. The coarse-grained fraction of the sediments sinked within one to three minutes close to the dumping site. Sediment dispersal was generally unidirectional and the size of the plume estimated with sounder echoes was below 20 m in diameter. Reduction of water transparency droped to 5-15 % of pre-dredging values 0,75 nautical mile from the source indicating that near complete dispersal and deposition of particulates were achieved within approximately 1 mile in the direction of prevailing currents. Results do not indicate any immediatly or long term effects (3 months) of the presence of dredged sediments on filtration rates, growth and mortality of transplanted cultured mussels. High sinking rate and limited dispersal of dredged material along with the net water movement during dumping activities however suggest that mussels may not have experienced high loads of suspended material during the study.
Shrimpo (Pandalus borealis) landings in the Gulf of St. Lawrence almost reached 12 000 tons in 1987 which is an increase of 25 % relative to 1986. All area catches increased in variable proportions and quotas were caught in the North-Anticosti and Estuary areas. The status of the northern Gulf of St. Lawrence shrimp populations seems to be good. Commercial fleet catch rates have been stable whithin years. Spring biomass estimates obtained from an experimental survey done in 1987 have not shown a decrease in the abundance of populations. Demographic structures obtained in the abundance of populations. Demographic structures obtained from commercial sampling have not shown strong changes in these population dynamics. However, in Sept-Iles, sex inversion happened at a smaller size in 1987 than in 1982. Given that catches have continued to increase for all areas, that catch rates have been stable and, that spring biomass has been relatively high, recommanded TAC's in 1987 should still be appropriate for the 1988 fishing season.
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