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GENDRON, L., P. GAGNON, 2001. Impact of various fishery management measures on egg production per recruit in American lobster(Homarus americanus). Can. Tech. Rep. Fish. Aquat. Sci., 2369, 31 p .
A detailed model of the life cycle of lobster populations from the Magdalen Islands and Gaspe, taking into account uncertainty in the input parameters arising from the difficulty in assessing their value or from their natural variability, was developed and used to assess the impact of new fishery regulations on the egg production per recruit (EPR). THe new regulations included additional limits on the legal sizes (minimum, maximum), reduction of the exploitation rate and increased protection of females by v-notching. Results of the calculations were used to develop the management plans put forward in the Quebec region since 1997, to double the EPR compared to the 1996 level. We also present a risk analysis concerning lobster fishing management, based on the probability of not reaching a given level of EPR.
GENDRON, L., P. GAGNON, 2001. Impact de différentes mesures de gestion de la pêche au homard (Homarus americanus) sur la production d'oeufs par recrue. Rapp. tech. can. sci. halieut. aquat., 2369, 31 p .
A detailed model of the life cycle of the lobster from the Magdalen Islands and Gaspe populations, taking into account uncertainty in the input parameters arising from the difficulty in assessing their value or from their natural variability, was developed and used to assess the impact of new fishery regulations on the egg production per recruit (EPR). THe new regulations include additional limits on the legal sizes (minimum, maximum), reduction of the exploitation rate and increased protection of females by v-notching. Results of the calculations were used to develop the management plans put forward in the Quebec region since 1997, to double the EPR compared to the 1996 level. We also present a risk analysis concerning lobster fishing management, based on the probability of not reaching a given level of EPR.
CASTONGUAY, M., C. ROLLET, A. FRÉCHET, P. GAGNON, D. GILBERT, J.-C. BRÊTHES, 1999. Distribution changes of Atlantic cod (Gadus morhua L.) in the northern Gulf of St. Lawrence in relation to an oceanic cooling. ICES J. Mar. Sci., 56: 333-344 .
PROVENCHER, L., M. GIGUÈRE, P. GAGNON, 1997. Caractérisation du substrat entre les isobathes de 10 et 50 mètres autour des Îles-de-la-Madeleine par balayage hydroacoustique et échantillonnages sédimentologiques : évaluation du système de traitement des échos USP RoxAnn. Rapp. tech. can. sci. halieut. aquat., 2156, 49 p .
Acoustic measurements collected in 1991 and 1992, using the RoxAnn seabed discrimination system USP, have provided a description of the seabed around the Magdalen Islands between the 10 and 50 meter isobaths. Sediments sampled at 163 stations scattered on the acoustic path allowed the validation of the RoxAnn technology. Five types of seabed have been classified and mapped : very fine sand, fine sand, gravel, and rock. Empirical classification of seabed type from the RoxAnn system has been compared to that obtained using discriminant analysis of hydroacoustic data. Although the RoxAnn classification is satisfactory, discriminant analysis was more useful in defining the different types of seabed. Proper empirical calibration of the system is necessary to achieve reliable results. Recommendations on how this may be conducted are presented.
FRÉCHETTE, M., P. BERGERON, P. GAGNON, 1996. On the use of self-thinning relationships in stocking experiments. Aquaculture, 145: 91-112 .
MORIN, B., B. BERNIER, R. ARTHUR, G. CHOUINARD, A. FRÉCHET, P. GAGNON, 1996. L'évaluation et la biologie du flétan du Groenland (Reinhardtius hippoglossoides) du golfe du Saint-Laurent (4RST) en 1995 ; Assessment and biology of Greenland halibut (Reinhardtius hippoglossoides) in the Gulf of St. Lawrence (4RST) in 1995. MPO, Pêches de l'Atlantique, Document de recherche ; DFO, Atlantic Fisheries, Research document, 96/53, 59 p .
The main concentrations of Greenland halibut in the Gulf of St. Lawrence during the summer are found on the west side of Anticosti Island and to a lesser extent north of this Island and in the Esquiman Channel near the west coast of Newfoundland. Gillnet is the main fishing gear used in this fishery since the mid 1970's. Preliminary landings of 1995 reached 2300 t. The total allowable catch (TAC) was fixed to 4000 t since 1993. In 1996, it was reduced to 2000 t. Abundance indices increase slightly since 1990. Also, the abundance of commercial sizes (over 40 cm) Greenland halibut has increased since 1994 because of the presence of good year-classes. However, large size (over 50 cm) fish were still not numerous in the population in 1995 and the number of juveniles in 1995 was still lower than the average of 1990-1995. The length at which 50 % of the females reach maturity was estimated at 49 cm in 1995. The weight of fish according to length (or condition) increased slightly in 1995 for fish over 40 cm. In winter, the Greenland halibut concentrated in the Cabot Strait area are probably coming from the Gulf of St. Lawrence.
COUILLARD, C., P.V. HODSON, P. GAGNON, J.J. DODSON, 1995. Lesions and parasites in white suckers, Catostomus commersoni, in bleached-kraft pulp mill-contaminated and reference rivers. Environ. Toxicol. Chem., 14: 1051-1060 .
These stocking experiments allowed the development of a new type of holding cage for snow crab. The survival rate was 95 % after nine weeks and decreased more rapidly thereafter, probably due to the effect of prolonged starvation. The optimal crab stocking density was not determined, but no problem was encountered at the density of 37 kg/m2 used.
MORIN, B., D. POWER, P. GAGNON, 1994. Distribution of redfish (Sebastes spp.) in the Gulf of St. Lawrence and in the Laurentian Channel based on RV surveys and commercial fishery catch. MPO, Pêches de l'Atlantique, Document de recherche, 94/91, 52 p .
[Abstract only available in French]
L'analyse des relevés de poissons de fond dans les divisions 3Ps3Pn4RST de 1978 à 1993 a montré que le sébaste était concentré dans la région du détroit de Cabot en janvier et février. Cette observation semble s'être amplifiée depuis 1990 et les concentrations de sébaste débordent dans la sous-division 3Ps. La distribution des taux de capture de la pêche commerciale d'hiver supporte les données des relevés. En mai, les activités de pêche se déplacent vers le nord dans le golfe du Saint-Laurent, ainsi que vers le sud dans le chenal Laurentien, à la limite de 4Vn et 4Vs jusqu'au mois d'octobre. Les données de taux de capture analysées suggèrent que la migration du sébaste dans la région de Détroit de Cabot (4RT, 3Pn et 4Vn) a débuté aussi tôt que novembre au cours des trois dernières années ce qui ne concorde pas avec les unités de gestion présentement en place (i.e. 3Pn et 4Vn sont considérés comme du sébaste du chenal Laurentien ou Unité 2). La distribution du sébaste par groupe de longueur lors des relevés de poissons de fond a montré un déplacement vers le sud dans le détroit de Cabot à mesure que la taille des poissons augmente. La distribution et la migration des deux principales espèces de sébaste (Sebastes mentella and S. fasciatus) dans le golfe du Saint-Laurent semblent différentes et d'autres analyses sont requises afin de décrire l'impact sur la pêche.
HURTUBISE, S., P. GAGNON, 1993. Survey trawl research at Maurice Lamontagne Institute. Pages 37-39 in S.J. Walsh, P.A. Koeller & W.D. McKone (ed.). Proceedings of the International Workshop on Survey Trawl Mensuration, Northwest Atlantic Fisheries Centre ...1991. Department of fisheries and oceans (Can. Tech. Rep. Fish. Aquat. Sci., 1911) .
FRÉCHET, A., P. GAGNON, 1993. Changes in distribution and failure of the winter fixed gear cod (Gadus morhua) fishery off Southwestern Newfoundland. NAFO Sci. Counc. Stud., 18: 71-77 .
GRÉGOIRE, F., P. GAGNON, 1993. Analyse préliminaire des mesures de L1 sur des otolithes de maquereau bleu (Scomber scombrus L.) du golfe du Saint-Laurent. MPO, Document de recherche sur les pêches dans l'Atlantique, 93/62, 17 p .
We have observed in the Gulf of St. Lawrence mackerel some variations in the mean size of the otoliths at age one (L1) among the most recent year-classes. No difference was observed for year-classes prior to 1977, when the stock biomass was much lower. The strong year-classes of 1982, 1987 and 1988 were signalled by sudden decreases of the mean value of L1. We have also shown that fish with inferior or superior first-year growth relative to their group, as reflected by the L1 measurement, tend to maintain their position afterwards.
GAGNON, P., 1992. The analysis of comparative trawl selectivity experiments. CAFSAC Res. Doc., 92/120, 15 p .
CASTONGUAY, M., P. SIMARD, P. GAGNON, 1991. Usefulness of Fourier analysis of otolith shape for Atlantic mackerel (Scomber scombrus) stock discrimination. Can. J. Fish. Aquat. Sci., 48: 296-302 .
FRÉCHET, A., P. GAGNON, 1991. Changes in distribution of the 3Pn, 4RS cod stock and the failure of the winter fixed gear fisheries off southwestern Newfoundland. NAFO SCR Doc., 91/110, 13 p .
The spatial distribution of different sized cod in the 3Pn4RS management unit was investigated to identify possible closed areas to reduce the catch of small cod in the commercial fishery. Data from summer and winter groundfish surveys were used. The distribution of three size groups were analyzed : 0 to 29 cm - a size group rarely caught in the commercial fishery; 30 to 41cm - a size group below the market size and which is caught and discarded; and 42+cm - the market size group. The three size groups had similar distributions in summer, being abundant in coastal waters off northwestern Newfoundland and the north shore of the Gulf. Area closures at this time would have a major impact on the cod fishery. In winter, more spatial segregation was evident with the largest fish showing a more extensive migration into 3Pn than the other two size groups. Areas other than 3Pn acount for approximately 40 % of the winter fishery. The apparent differences in distribution migration and the patterns should be confirmed by analysis of commercial sampling and observer data.
GAGNON, P., 1991. The effects of set to strata allocation adjustments. CAFSAC Res. Doc., 91/62, 8 p .
The effect of different set to strata allocation adjustment strategies on the precision and accuracy of estimates is studied by simulation. The population models used are the cod biomass in NAFO division 3Pn-4RS and the cod abundance in 2J. The Poisson, log-normal and negative-binomial distributions are used to model the population variability within each stratum. The results show that the optimal adjustment of sampling fractions gives significant increase in the precision of estimated quantities. They also show that the strategies that involve adjusting the allocation of sets based on the results of the current survey introduce a bias in the estimates of the same order of magnitude as their standard errors.
GAGNON, P., 1991. Optimisation des campagnes d'échantillonnage : les programmes REGROUPE ET PARTS. Rapp. tech. can. sci. halieut. aquat., 1818, 20 p .
A review of the statistical theory pertaining to trawl survey sampling plans is presented. Two tools for the optimization of survey design are described. The REGROUPE program finds optimal sampling fractions for groups of homogeneous regions. The PARTS program calculates the optimum number of sets to be allocated to each region within user-specified constraints. It also allows the monitoring of the statistical evolution of the survey.
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