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LAROCQUE, R., J-D. DUTIL, S. PROULX, M. THORNE, P.-M. SCALLON-CHOUINARD, M.-H. GENDRON, J. PLOURDE, T. SCHMITT, 2010. Contribution à la description de l'habitat des loups de mer (Anarhichas spp.) près de la péninsule gaspésienne par vidéo remorquée et relevés acoustiques multifaisceaux. Rapp. tech. can. sci. halieut. aquat., 2902, 51 p .
This report presents the results of several initiatives that examine the potential habitat of wolffish (Anarhichas spp.) in the Gulf of St. Lawrence and in particular near the Gaspé peninsula. The habitat features were examined at different spatial scales: by towed video, multibeam acoustic surveys and an examination of historical catch data. High-resolution bathymetry and backscatter coupled with information extracted from video allowed for a detailed description of environments known to be used by wolfish. Features believed to be favourable to wolfish were identified on both survey sites, including shelters and glacial scours. The resulting information is presented within the attached multimedia DVD-ROM. The complimentary nature of these methods and the management implications for a species at risk are discussed.
DUTIL, J.-D., C. DION, L. GAMACHE, R. LAROCQUE, J.- F. OUELLET, 2010. Ration and temperature effects on the condition of male adolescent molter and skip molter snow crab. J. Shellfish Res., 29(4): 1025-1033 .
This study examined the effects of ration and temperature on the molt of male adolescent snow crab Chionoecetes opilio (O. Fabricius, 1788). In one experiment, crabs were exposed to 1 of 4 treatments, 2 levels of ration and 2 levels of temperature. In a second experiment, all crabs were fed and a 4-level factor was addressed in which temperature was held constant as in experiment 1 (2 levels) or switched from one level to the other. Food consumption declined significantly and at a similar rate over time at both temperatures, several weeks before molt took place. Larger crabs molted to morphometric maturity in a greater proportion with no influence of ration or temperature. Smaller crabs also molted earlier than larger crabs. Temperature had a marked effect on the timing of molt, with crabs kept at a higher temperature molting 1 mo earlier and crabs exposed to shifted temperatures, molting midway between the two other groups. Body density decreased markedly at ecdysis, but was also influenced by ration and temperature particularly in nonmolters; the effect of ration on body density in nonmolters was highly significant. Ration also had a major effect on the size of muscle and digestive gland and their moisture content. Unfed nonmolters were in poor condition, particularly at a higher temperature, whereas molted crabs had large digestive glands associated with high moisture contents, irrespective of treatment. Timing of the migration of snow crabs to shallow and potentially warmer waters in the spring in the Gulf of St. Lawrence might be determined in part by molt requirements. Cold temperatures provide an energetic advantage during the premolt period, when food consumption decreases, but high temperatures result in an earlier molt and a fast recovery during the early postmolt eriod.©2010 Journal of Shelfish Research.
Laboratory experiments were conducted to assess shelter use and behaviour of juvenile Spotted Wolfish, Anarhichas minor, using time-lapse video. Information about the behaviour of Spotted Wolffish and its habitat utilization is sparse due to the great depth at which this species lives. Four experiments were conducted using one or two fish per tank, with and without a shelter. The positions and movements of fish in the tanks and interactions between fish were monitored over 24-h periods. In experiments in which no shelter was available, Spotted Wolffsih spent very little time exploring the water column. They did not show fidelity to a particular area on the bottom of the tank and exhibited few signs of aggressiveness to each other. When a shelter was made available, fish spent most of their time in the shelter or close to the shelter. The presence of a single shelter did not enhance aggressive behaviours in fish kept in pairs. When day and night observations were compared, no clear diel pattern emerged. The Canadian recovery plan for Spotted Wolffish calls for research aimed at describing their use of demersal habitats. The present study suggests that shelter availability might be an important feature of the habitat requirements of juvenile Spotted Wolffish.©2010 Springer
LAVOIE, D., N. PINET, M. DUCHESNE, A. BOLDUC, R. LAROCQUE, 2010. Methane-derived authigenic carbonates from active hydrocarbon seeps of the St. Lawrence Estuary, Canada. Mar. Pet. Geol., 27: 1262-1272 .
Nearly 2000 pockmarks with diameters ranging from a few tens of meters up to 700 m are present on the seafloor of the St. Lawrence Estuary in eastern Canada. Coring of some pockmarks resulted in the recovery of various-sized and shaped carbonate concretions in a predominantly silty mud matrix. Petrographic and geochemical data on four authigenic carbonate concretions are reported as well as data from shell material in the unconsolidated sediment. Video observations and echo-sounder images indicate that the sampled pockmarks are actively gas venting. The video images show significant lookalike microbial mats in areas where gas is venting. The carbonate concretions are primarily made up of carbonate cements with varying percentage of shell fragments, micrite particles and fine-grained clastics. Orthorhombic crystal morphology and diagenetic fabrics including isopachous layers and botryoids characterize the aragonite cement. Oxygen isotopes ratios for the cement crusts do not record any thermal anomaly at the site of precipitation with δ18OVPDB ratios (+3 ‰) in equilibrium with cold (5 °C) deep marine waters, whereas significant negative δ13CVPDB ratios (–9.9 to –33.5 ‰) for cement and shell material within concretions indicate that the carbonates largely derive from the microbial oxidation of methane. The δ13CVPDB ratios of aragonite shells (–2.7 to –5.6 ‰) taken from unconsolidated sediments at some distance from the concretions/vents show variable dilution of HCO3 with negative δ13CVPDB ratios derived from microbial oxidation of methane with isotopically normal (0 ‰) marine bicarbonate. These results are in agreement with other lines of evidence suggesting that pockmarks formed through the recent and still active release of gas from a reservoir within the Paleozoic sedimentary succession.©2010 Elsevier Ltd.
The extent of spatial (depth and locality) and temporal (season and year) variabilities in condition and relative muscle size (a direct proxy of growth) were examined in male and female adult and non-adult snow crabs Chionoecetes opilio. Condition, determined from the relative size of the digestive gland and moisture content of the muscle and digestive gland, and muscle size, determined as the ratio of merus muscle mass over merus volume, separated as diVerent processes in a principal component analysis. Snow crabs showed a wide range of condition and muscle size values. Overall, the condition was better in non-adult than in adult crabs, with adult females being in worst condition, and muscle size was larger in males than in females. Condition variability was greater for seasonal compared to annual samples, probably reXecting annual molt cycles. In contrast, the muscle size variability was greater for annual compared to seasonal samples, possibly as a result of changing crab abundance and competition intensity during recruitment pulses. Condition and muscle size increased through summer in males and immature females, although to diVerent extents depending on instar, but did not change in adult females. Both condition and muscle size were highly variable at the investigated spatial scales. Condition and muscle size had a signiWcant eVect on gonad size, once the eVect of crab size was removed, suggesting a direct link between these two parameters and reproductive capability.©2009 Springer
BOLDUC, A., R. LAROCQUE, M.J. DUCHESNE, 2008. Des évents actifs dans l'estuaire du Saint-Laurent, Québec. Commission géologique du Canada, Recherches en cours 2008-21, 11 p .
Numerous vents are present on the seafloor of the lower St. Lawrence Estuary. Some are grouped in clusters, while others are aligned along underlying bedrock structures. The morphology of some vents suggests that they formed recently and are potentiallly active. In order to test the hypothesis that the vents of the St. Lawrence are actively releasing gas, a scientific cruise was organized to video record two targets that were identified as good candidates. The images show the presence of abundant marine organisms near the vents, including bacterial mats, some showing signs of calcificationl Gas bubbles were also observed, indicating present-day activity of these vents©2008 Sa Majesté la Reine du chef du Canada
DUTIL, J.-D., C. JABOUIN, R. LAROCQUE, G. DESROSIERS, P.U. BLIER, 2008. Atlantic cod (Gadus morhua) from cold and warm environments differ in their maximum growth capacity at low temperatures. Can. J. Fish. Aquat. Sci., 65: 2579-2591 .
Maximum growth rate of Atlantic cod (Gadus morhua) was determined at a range of temperatures representative of cod benthic habitats (1-13 °C) using wild animals obtained from a cold environment (southern Gulf of St. Lawrence stock, SG) and a mild environment (Bay of Fundy stock, BF). SG cod performed well over a broader range of temperatures than BF cod. Growth in mass was greater for SG than BF cod at any temperature below 7 °C. SG cod consumed twice as much food as BF cod at 1 and 3 °C. At 1 °C, growth in mass was positive for SG cod but negative for BF cod, whereas growth in length did not differ from 0 for both SG and BF cod. Liver size represented a larger proportion of body mass in SG cod at both low and high temperatures, and citrate synthase activity in the intestine exhibited a strong inverse relationship to temperature. The maximum growth capacity of SG cod was comparable with that of cod of similar size in various other stocks in the Atlantic. These observations are not consistent with the view that intensive size-selective fishing practices have resulted in a significant loss of innate growth capacity in SG cod.©2008 NRC Canada
Atlantic wolffish (Anarhichas lupus) and spotted wolffish (A. minor) are respectively listed as a species of special concern and as a threatened species under the Species at Risk Act (SARA) in Canada. The objectives of this work were to gather information on a near-shore wolffish population in the St. Lawrence estuary in eastern Quebec, to evaluate methods related to wolffish studies, and to assess the feasibility of wolffish release and in situ monitoring. The local A. lupus distribution was found to be vertically limited by temperature, with wolffish avoiding the surface layer affected by the Gaspé Current. The numbers of fish on the deeper reefs was relatively constant over the two years of the study, with many specimens spending long periods in the same shelters. Winter survival following a fish-release experiment was confirmed by scuba observations. Migration may explain the apparent low success rate of the release effort. Fish pairings and egg masses were observed, and this led to an evaluation of the role of coastal reefs in the life history of Anarhichas spp. A non-intrusive method for measuring fish was used by scuba divers and is described. The use of a high-resolution multibeam sonar survey as a tool for scuba divers and habitat-related work is also discussed.
DUTIL, J.-D., E.-L. SYLVESTRE, L. GAMACHE, R. LAROCQUE, H. GUDERLEY, 2007. Burst and coast use, swimming performance and metabolism of Atlantic cod Gadus morhua in sub-lethal hypoxic conditions. J. Fish Biol., 71(2): 363-375 .
Prolonged swimming capacity (critical swimming speed, Ucrit, protocol) and metabolism were measured for 14 Atlantic cod Gadus morhua exposed to seven oxygen levels within the non-lethal range normally encountered in the Gulf of St Lawrence (35 to 100 % saturation). Burst-and-coast swimming was triggered earlier (at lower speeds) in hypoxia, and burst-and-coast movements were more frequent in hypoxia than in normoxia at low speeds. Furthermore, the metabolic scope beyond the metabolic rate at which Atlantic cod resorted to burst-and-coast movements decreased gradually as ambient oxygen concentration dropped. Overall, fewer burst-and-coast movements were observed in hypoxia while the distance swum in burst-and-coast mode remained c. 1 % of the total distance swam in all tests. Oxygen availability had no effect on the rate of increase in metabolic rate with increasing velocity <50 cm s-1, but limited swimming performances and metabolic rate at higher speeds. The prevailing low oxygen tensions on the bottom in the deep channels may impair the swimming capacity of Atlantic cod in the estuary and northern Gulf of St Lawrence. ©2007 Crown in Right of Canada
LAROCQUE, R., 2005. Menaçants, mais menacés : les loups atlantiques. En Profondeur, 5(1): 18-19 .
LEMIEUX, H., J.-D. DUTIL, H. GUDERLEY, R. LAROCQUE, 2004. Growth, starvation and enzyme activity in white muscle of Atlantic cod: at what point do muscle metabolic capacities change?. Mar. Fresh. Behav. Physiol., 37(4): 287-294 .
Muscle protein decreases only during prolonged starvation of Atlantic cod (Gadus morhua, Gadidae), but in the absence of protein renewal, muscle metabolic capacities may decrease before marked loss of muscle protein. This study aimed at elucidating the threshold at which decreases in growth and condition reduce muscle metabolic capacities, as well as identifying the indicators that best explain changes in metabolic capacities. To generate a wide spectrum of individual growth rates, condition factors and proximate compositions, cod showing different initial condition were fed or starved for different periods of time. The relationships between muscle proteins and metabolic enzyme activities (LDH and CCO) on one hand, and growth rate, condition factor, hepato- and gonadosomatic index and muscle and liver water and energy contents, on the other hand, were examined through linear regression models. Multiple linear regressions explained a large proportion of the observed variability in proteins and enzyme activities. Changes in LDH and CCO activities were not driven by changes in growth rate. Muscle water was the only significant correlate for both enzymes. Enzyme activities decreased as soon as muscle water began to rise. Increases in water content from 79 to 92 % resulted in a 10-fold decrease in LDH and CCO activities.©2004 Taylor & Francis Ltd
LAROCQUE, R., 2004. Diving the great Saguenay Fjord. Diver Magazine, 29(8): 24-25 .
LAROCQUE, R., 2000. Moules zébrées et plongeurs : de l'eau claire mais à quel prix?. En profondeur, 6(1): 7 .
LAROCQUE, R., 2000. A SCUBA technique for collecting live Sebastes spp. Specimens. Can. Tech. Rep. Fish. Aquat. Sci., 2309: 13 p .
Redfish species (Sebastes sp.) are typically found in deep water and are highly vulnerable to decompression damage when brought to the surface. When limited numbers of live specimens are required for experimental work, collection by SCUBA divers in the relatively shallow waters of the St. Lawrence Estuary was shown to be an efficient method that reduced the potential for damage to the fish. Custom made diver-carried cages contributed to limiting the fish's stress. in situ decompression was the preferred method for preventing internal damage due to the increased volume of the gas-bladder. Fish densities had to be relatively high for the divers to achieve a reasonable level of success during the 20 to 30 minutes of available bottom time on each dive. Four series of dives were done over a 25 month period. A total of 249 fish were collected, averaging seven to eight fish per dive. Methods to reduce mortality due to decompression and transport are discussed.
BLASCO, D., M. LEVASSEUR, R. GÉLINAS, R. LAROCQUE, A.D. CEMBELLA, B. HUPPERTZ, E. BONNEAU, 1998. Monitorage du phytoplancton toxique et des toxines de type IPM dans les mollusques du Saint-Laurent : 1989 à 1994. Rapp. stat. can. hydrogr. sci. océan., 151, 117 p .
The Department of Fisheries and Oceans has conducted monitoring programs for paralytic shellfish poisoning (PSP) and harmful algae in the St. Lawrence since 1984 and 1989, respectively. Harmful algae are sampled weekly at 11 coastal stations from April to November while shellfish are collected at approximately 85 stations from March to November. The most important harmful algae enumerated are Alexandrium tamarense (= Gonyaulax tamarensis), A. ostenfeldii, Dinophysis acuminata, D. norvegica, and Phalacroma rotundatum. The main shellfish species collected are blue mussels (Mytilus edulis) and soft-shelled clams (Mya arenaria). This report presents a synthesis of the data collected between 1984 and 1994 during these monitoring programs. Shellfish generally become toxic)<80 µg STX eq/100 g meat) as soon as the abundance of Alexandrium spp. (A. tamarense + A. ostenfeldii) reaches 1 000 cells L-1. As previously observed in other regions, mussels are generally 5 times more toxic than soft-shelled clams at the same location. Maximum Alexandrium spp. concentrations and PSP toxins in mussels and soft-shelled clams were measured in the upper North Shore, lower St. Lawrence-north Gaspésie, and southeast Gaspésie regions. Very low concentrations of Alexandrium spp. were measured in the lower North Shore and Magdalen Islands regions, where shellfish toxicity has always been below the critical limit of 80 µg STX ea/100 g meat. Alexandrium spp. was also found in low numbers in the southwest Gaspésie region, although mussel toxicité reached values higher than 80 µg STX eq/100 g meat on a few occasions between 1989 adn 1994. The mid-North Shore region is characterized by a gradual east-west increase in Alexandrium spp. abundance and shellfish toxicity. Shellfish collected in the western part of this region often exibit toxicity values higher than 80 µg STX eq/100 g meat. No statistically significant interannual variations in Alexandrium spp. abundance was observed between 1989 and 1994 at our sampling stations. However, we did observed significant interannual variations in mussel toxicity between 1984 and 1994, with minimum and maximum toxicity being recorded in 1987-88 and 1991, respectively.
TAY, K.L., K.G. DOE, A.J. MACDONALD, S.J. WADE, J.D.A. VAUGHAN, A.L. HUYBERS, G.D. WOHLGESCHAFFEN, K. LEE, R. LAROCQUE, 1995. Environmental assessment of a dredged material dump site using multitrophic level sediment bioassays and a bioaccumulation test. Pages 50-51 in G.F. Westlake, J.L Parrott & A.J. Niimi (ed.). Proceedings of the 21st Annual Aquatic Toxicity Workshop : October 3-5, 1994, Sarnia, Ontario. Dept. of Fisheries and Oceans (Can. Tech. Rep. Fish. Aquat. Sci., 2050) .
LEE, K., R. LAROCQUE, K.L. TAY, 1995. Development of environmental impact assessment tests based on the exoenzyme activity of indigenous bacteria. Pages 173-175 in G.F. Westlake, J.L. Parrott & A.J. Niimi (ed.). Proceedings of the 21st Annual Aquatic Toxicity Workshop : October 3-5, 1994, Sarnia, Ontario. Dept. of Fisheries and Oceans (Can. Tech. Rep. Fish. Aquat. Sci., 2050) .
TAY, K.L., K.G. DOE, A.J. MACDONALD, S.J. WADE, J.D.A. VAUGHAN, A.L. HUYBERS'D, K. LEE, R. LAROCQUE, 1994. Application of sediment bioassays for the environmental assessment of ocean dump sites. Pages 48-49 in Proceedings of the Twentieth Annual Aquatic Toxicity Workshop, October 17-21, 1993, Quebec City, Quebec. Dept. of Fisheries and Oceans (Can. Tech. Rep. Fish. Aquat. Sci., 1989) .
CEMBELLA, A.D., S.E. SHUMWAY, R. LAROCQUE, 1994. Sequestering and putative biotransformation of paralytic shellfish toxins by the sea scallop Placopecten magellanicus : seasonal and spatial scales in natural populations. J. Exp. Mar. Biol. Ecol., 180: 1-22 .
LEE, K., R. LAROCQUE, 1993. Development of environmental impact assessment tests based on the exoenzyme activity of indigenous bacteria. Pages 252 in Proceedings of the 20th Annual Aquatic Toxicology Conference, Québec, Québec .
LAROCQUE, R., A.D. CEMBELLA, 1991. Résultats du premier programme de suivi des populations de phytoplancton toxique dans l'estuaire et le golfe du Saint-Laurent (Région du Québec). Rapp. tech. can. sci. halieut. aquat., 1796, 42 p .
This report presents the results from the first toxic phytoplankton monitoring program in the Quebec region. Its main objective is to answer basic questions about the distribution of toxic species in the St. Lawrence estuary and northwestern Gulf of St. Lawrence. In 1989, 10 stations were sampled for toxic phytoplankton. Most of these stations were sampled weekly between June and November. The data collected in 1989 show that for most stations only one annual bloom of Alexandrium spp. occurred, predominantly during June and July. At certain stations where the sampling started in early June, the link between the PSP toxicity in shellfish and the toxic blooms was clearly established. The station in the Magdalen Islands warranted special attention, since relatively low but constant numbers of Alexandrium spp. cells were encountered during the summer. The sampling program also demonstrated the wide geographical distribution of potential DSP-producing species, as Dinophysis spp. were found at all stations. Particularly high concentrations were noted in the Baie de Gaspé and Baie des Chaleurs. In view of the 1989 results in the Quebec region, some modifications to the program were proposed for the following years.
DESBIENS, M., F. COULOMBE, J. GAUDREAULT, A.D. CEMBELLA, R. LAROCQUE, 1990. PSP toxicity of wild and cultured blue mussels induced by Alexandrium excavatum in Gaspé Bay (Canada) : implications for aquaculture. Pages 459-462 in E. Graneli, B. Sundström, L. Edler & D.M. Anderson (ed.). Toxic marine phytoplankton. Elsevier Science, New York .
LAROCQUE, R., J.A. GAGNÉ, 1990. Algues microscopiques et intoxication des mollusques. L'Euskarien, 12(2): 45-48 .
LAROCQUE, R., A.D. CEMBELLA, 1990. Ecological parameters associated with the seasonal occurrence of Alexandrium spp. and consequent shellfish toxicity in the Lower St. Lawrence Estuary (Eastern Canada). Pages 368-373 in E. Graneli, B. Sundström, L. Edler & D.M. Anderson (ed.). Toxic marine phytoplankton. Elsevier Science, New York .
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