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GENDRON, L., P. GAUTHIER, G. SAVARD, 2007. Expériences préliminaires de culture de lalgue brune Laminaria longicruris en laboratoire et en mer au large de Paspébiac (Québec) en 2006. Rapp. tech. can. sci. halieut. aquat., 2731, 53 p .
PELLETIER, L., P. GAUTHIER, 2002. Inventaire de l'oursin vert (Strongylocentrotus droebachiensis) au Bas-Saint-Laurent à l'aide d'une caméra vidéo sous-marine. Rapp. tech. can. sci. halieut. aquat., 2394, 30 p .
This report presents results from an underwater video inventory of the distribution, abundance and size structure of the green sea urchins (Strongylocentrotus droebachiensis) in the Lower St. Lawrence during the summer of 2000. A total of 28 video transects of depths varying between 0 and 10 m were conducted between Cacouna and Rimouski. The sizes and densities of green sea urchins were measured from 795 pictures of 0.25 m2 quadrats extracted from the video tapes. Green sea urchins were present everywhere in the study area and on all types of substrates including sandy bottoms, which dominate the zone. The distribution of the sea urchins was heterogeneous: depending on transects, average densities varied between 0.1 and 44.4 urchins/m2. Important variations in densities were also observed between quadrats of a same transect. The highest concentrations of sea urchins were found close to the extremity of Île Verte (44 and 32 urchins/m2) and near Trois-Pistoles (39 urchins/m2). The density of sea urchins of commercial size (≥ 50 mm) was generally low (< 5 urchins/m2), and the highest concentrations were measured at or close to actual or prospective aquaculture sites. The underwater video camera proves to be an adequate tool for the study of green sea urchins in the Lower St. Lawrence, allowing the survey of a large zone in an economic and safe manner.
PELLETIER, L., P. GAUTHIER, M. NADEAU, 2001. L'oursin vert (Strongylocentrotus droebachiensis) des Îles-de-la-Madeleine : description des agrégations et potentiel d'exploitation. Rapp. tech. can. sci. halieut. aquat., 2362, 28 p .
This report presents a first description of the green sea urchin aggregations in Île-de-la-Madeleine and the evaluation of their potential for exploitation, based on a diving survey conducted in September 1999. Eight sites previously visited by fishermen and characterized by hard bottoms were examined. Three main sites were sampled near the Les Demoiselles hills, Gros Cap and Shag island. Sea urchin densities varied from 0 to 83.3 urchins/m2 without an apparent relationship to macroalgae abundance or depth, but possibly related to the bottom type. Test diameter varied from 6 to 66 mm and only 9ppt of the sea urchins had reached the legal size of 50 mm. The relationship between weight and test diameter were compared with those described by other Canadian studies. Indices of density are given for each site as well as a first estimate of the total fishable biomass (5123 t) for all eight sites. In September 1999, the gonads of the sea urchins were poorly developed and their weights were less than 10ppt of the total weight of the animal. The sex ratio was estimated at 1.0 males : 1.1 females. Ages of the sea urchins were determined with the method based on the counts of the growth lines on the rotules of Aristotle's lantern. The results obtained by this method indicate that the age of the sea urchins at 50 mm varied between 4 and 20 years (average 9 years). The life span is estimated at 19-20 years. This index of longevity is incorporated into the calculation of the potential for exploitation estimated at 235 t for the visited areas.
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