Jean-Claude Brêthes - Academia.edu (original) (raw)

Papers by Jean-Claude Brêthes

Marine Biology, Jun 1, 2004

Changes in yolk total proteins and lipid components and embryonic growth rates during lobster (Ho... more Changes in yolk total proteins and lipid components and embryonic growth rates during lobster (Homarus americanus) egg development under a simulated seasonal temperature cycle

Marine Ecology Progress Series, Aug 18, 2010

Biodiversity can play an important role in the stability and resilience of ecosystems when these ... more Biodiversity can play an important role in the stability and resilience of ecosystems when these are faced with environmental change or anthropogenic impacts. Historically, the northwest Gulf of St. Lawrence had high fish egg and larval productivity. To assess changes in the ichthyoplankton community of this region, data from sampling surveys that were carried out in spring from 1985 to 1987 were compared with data from spring 2005 to 2007. Significant differences in ichthyoplankton abundances between the 2 decades and sampling times (May versus June) were revealed by multivariate analyses (nMDS, ANOSIM, PERMANOVA, and SIMPER) and univariate (ANOVA) analyses. Total ichthyoplankton abundance was lower in the 2000s than during the mid-1980s. Although larval sandlance Ammodytes spp. abundances did not change significantly, other taxa, such as Stichaeidae larvae and H4B eggs (gadids and merlucciid hakes, rocklings, butterfish Peprilus triancanthus, windowpane Scophthalmus aquosus and Gulf Stream flounder Citharichthys arctifrons), became more abundant; the abundance of CHW eggs (cod Gadus morhua, haddock Melanogrammus aeglefinus, witch flounder Glyptocephalus cynoglossus), and redfish Sebastes spp. larvae generally declined by more than an order of magnitude. Greenland halibut Reinhardtius hippoglossoides larvae also appeared in the 2000s assemblages. This dominance shift in the ichthyoplankton community reflects the demise of large fish predators and the response of the non-commercial species. Our study provides much-needed new information concerning current biodiversity and productivity of the fish community in the Gulf of St. Lawrence and insights into changes influenced by groundfish collapse and environmental fluctuations.

Canadian Journal of Fisheries and Aquatic Sciences, May 1, 2002

A spatially explicit model is proposed to assess the impact on fishing mortality of modifying eff... more A spatially explicit model is proposed to assess the impact on fishing mortality of modifying effort patterns for an American lobster (Homarus americanus) fishery. A two-box (offshore and inshore grounds) model is developed for the 1995 lobster fishery season in the Magdalen Islands (Quebec). It considers lobster migration and fisher's temporal and spatial effort dynamics to estimate within-season catchability patterns and exchange rates between the two spatial units. Different management scenarios are simulated: reducing nominal fishing effort and changing its temporal (season's length) and spatial (area closures) allocations. Catchability showed a strong temporal trend, being highest during the first 3 weeks and declining regularly afterwards. The model indicated a continuous migration toward the inshore during the fishing season and that a significant amount of biomass remained offshore. As a result, reducing fishing effort at the beginning of the season would have the greatest impact on exploitation rate. Allowing less effort in the offshore area would also reduce the exploitation rate significantly. Restricting effort to the inshore area, as it was 25 years ago, reduced substantially the exploitation rate. This model represents the first attempt to analyze in-season fishery dynamics and should be useful to further assess the impact of management measures.

144th Annual Meeting of the American Fisheries Society, Aug 18, 2014

Le Naturaliste Canadien, Jun 2, 2016

Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Cet article est diffusé et préservé par Érudit. Érudit est un consortium interuniversitaire sans but lucratif composé de l'

Journal of Northwest Atlantic Fishery Science, Dec 1, 1986

Size distributions of the exploited snow crab (Chionoecetes opilio) population in the southwester... more Size distributions of the exploited snow crab (Chionoecetes opilio) population in the southwestern Gulf of St. Lawrence were obtained from commercial landings in New Brunswick ports during 1977-82. The unexploited part of the stock was sampled during research vessel surveys in 1980 and 1981. The size distributions were analyzed by factorial analysis of correspondence. The trend in mean size was negative from 1977 to 1981 and positive thereafter. The analysis identified two periods of recruitment to the standing stock within each year: the first at the beginning of summer and the second in late summer and autumn. Growth of the previouslyrecruited crabs occurred between these two periods. Analysis of research vessel data indicated that many prerecruits inhabited areas outside the usual fishing grounds. The hypothesis is proposed of recruitment by platoons, with a part being due possibly to migration of crabs from shallow unexploited areas to deeper water where the commercial fishery occurs.

Canadian Journal of Fisheries and Aquatic Sciences, Jul 1, 1991

A total of 7760 Chionoecetes opilio males were marked and released on the bottom at the entrance ... more A total of 7760 Chionoecetes opilio males were marked and released on the bottom at the entrance to Chaleur Bay and near the Îles-de-la-Madeleine in the southwestern Gulf of St. Lawrence in 1986 and 1987. Of this number, 976 individuals, all morphometrically mature, were recovered between 1987 and 1989. The average distance covered was 9.6 km for Chaleur Bay (maximum 47.0 km) and 13.7 km for the Îles-de-la-Madeleine (maximum 89.5 km). Size had no significant effect on distance covered or direction of movement. Individuals released at higher or intermediate bottom depths followed the slope downward. In the Chaleur Bay sector, the crabs at greater depth showed a tendency to move up the slope. Near the Îles-de-la-Madeleine, most of the individuals released at greater depth stayed on the valley floor, but there was also a tendency to move upward. It appears that there are two types of travel, a general downward movement, disturbed by seasonal shifts which are undoubtedly related to reproduction. Large movements suggest the possible existence of contacts between local substocks.

Ocean & Coastal Management, Apr 1, 1998

Most of the world groundfish fisheries are fully exploited or overexploited. Numerous constraints... more Most of the world groundfish fisheries are fully exploited or overexploited. Numerous constraints to conservation exist and are described from the Canadian Atlantic situation. Both harvesting and processing capacity increased significantly in the recent past and remain latent during the current fishing closures. Local economies are dependent on fishing influence, inducing a pressure on the management system. Fluctuations in the natural environment influence the regenerating capacity of populations. Several scientific knowledge gaps are appearing: overestimation of stocks, inability to assess and predict the effects of the environment. The institutional system is complex with conflicting views and numerous interactions which jeopardise coherent actions. The system is changing, and we cannot predict the actual effect of fishing closures. Changes must be made to develop a conservation strategy for the long time. A systemic approach must be developed to better understand the functioning of the system and to implement efficient acceptable conservation measures. Building a conservation capacity appears necessary.

Canadian Journal of Fisheries and Aquatic Sciences, Mar 1, 1981

We describe a technique, derived from the von Bertalanffy growth curve and from the mortality equ... more We describe a technique, derived from the von Bertalanffy growth curve and from the mortality equation, which allows the estimation of potential catches from an unexploited stock of mollusca on the basis of the population&amp;amp;amp;amp;#39;s length composition data. Comparison with results obtained from age composition data shows that both methods give similar values for mortality rates and yields. That technique could be very useful when it is difficult or impossible to obtain systematic age readings.Key words: Mya arenaria, growth, mortality, yield

Canadian Journal of Fisheries and Aquatic Sciences, 1997

Abstract: We evaluated if time of onset, intensity, and duration of the spawning period were modi... more Abstract: We evaluated if time of onset, intensity, and duration of the spawning period were modified in mummichog (Fundulus heteroclitus) exposed to bleached kraft pulp mill effluents (BKME). Gonadosomatic index (GSI), percentage of mature fish, fecundity, and egg size were ...

Canadian Journal of Zoology, Feb 1, 1991

The stomach contents of snow crabs (Chionoecetes opilio) of carapace width >0.6 cm and &am... more The stomach contents of snow crabs (Chionoecetes opilio) of carapace width >0.6 cm and <7.3 cm were examined in 650 specimens collected at the entrance of the Chaleur Bay, in the southwestern region of the Gulf of St. Lawrence. Individuals were collected with a beam trawl at depths of 70–120 m, on gravelly–muddy and muddy substrates, during the summers of 1986 and 1987. A repletion iridex (RI) was estimated and the daily feeding rhythm of early benthic stages (carapace width <3.0 cm) was determined while considering four classes of RI on 246 crabs. A significant difference between day and night in RI was observed, indicating nocturnal feeding activity in early benthic stages of snow crab, as is the case in the older stages. The mineral content of stomachs, as determined by burning, increases proportionally with the size of the crab. Diet is dominated by crustacea (85% of stomachs), followed by polychaeta (83%) and mollusca (19%). A correspondence analysis conducted on preys and variables (depth, substratum, and size of crab) showed common feeding preferences for crabs of the same size in spite of environmental disparity.

Journal of Northwest Atlantic Fishery Science, 1992

Samples of American sand lance (Ammodytes americanus) were collected in June-September 1983 off t... more Samples of American sand lance (Ammodytes americanus) were collected in June-September 1983 off the north shore of the Gulf of St. Lawrence, at depths varying from 1 to 40 m. Length-frequency modes identified by modal analysis corresponded closely with mean lengths of fish based on otolith annuli counts, supporting the hypothesis that the number of annuli corresponds to the age of the fish. The otolith length was linearly correlated with the fish length. An opaque annulus was deposited over a short period, primarily August. The study indicated that 75-100% of the annual growth was achieved during the June-September period. Maximum life span was estimated to be 12 years. The parameters of the von Bertalanffy growth equation were: K = 0.24 year", Lao = 188.2 mm, to =-1.14 year. The growth of the American sand lance in the study area was slower than for the same species and for A. dubius in more southern areas. The length-weight relationship indicated that the growth in weight was isometric and identical for both sexes. Length-weight relationship, gonadosomatic index and the observation of maturity stages suggested that reproduction takes place shortly after September. All the fishes were matured at 20 months of age. Males mature at a smaller size «85 mm) than the females (90 mm).

Journal of Fish Biology, Sep 1, 2008

Morphological variations of the serranid fish Cephalopholis taeniops were studied in relation to ... more Morphological variations of the serranid fish Cephalopholis taeniops were studied in relation to habitat fragmentation in the Cape Verde Archipelago. While a significant allometric effect existed (11·5% of total body‐shape variation), differences in morphology associated with sex and ontogeny were not significant. MANOVA followed by CVA showed that each island presented a particular allometric pattern. Average body shape for all islands was well discriminated with CVA models. Pair‐wise comparisons of the ontogeny of morphological change between islands revealed that northern islands (Santo Antão, São Vicente and Santa Luzia) along with Boavista Island showed a similar direction in shape ontogeny, while all other paired comparisons indicated different ontogenetic patterns. When comparing directions of inter‐population shape changes, individuals from Fogo Island, the southernmost locality, departed far from the orthogonal relation, suggesting that they were undergoing independent body‐shape trajectories. Physical isolation by geographic distance and depth was positively correlated with morphological divergence among populations from different islands. This finding supports the hypothesis that habitat fragmentation in the Cape Verde Archipelago can be interpreted in terms of marine population structure.

Journal of Fish Biology, Jul 1, 2012

Homing behaviour and group cohesion in Atlantic cod Gadus morhua from the northern Gulf of St Law... more Homing behaviour and group cohesion in Atlantic cod Gadus morhua from the northern Gulf of St Lawrence were studied based on tagging-recapture data from two periods, the 1980s and a recent period from 1996 to 2008. Two or more tags from a single tagging experiment were frequently recovered together in subsequent years. The null hypothesis was tested that the frequency of matching tag recoveries occurred by chance only through random mixing of tagged G. morhua before their recapture by the commercial fishery. The alternative hypothesis was that non-random, positive association (group cohesion) existed among tagged individuals that persisted through time and during migrations. Results show that the G. morhua population exhibits a homing behaviour, with temporal stability across seasons and years: 50% of recaptured fish in the recent period were caught <34 km from their mark site, even 3 years after release. In the 1980s, G. morhua were located at <10 km from their release site 1 year after tagging during summer and at <16 km during spring and autumn combined. Despite the increasing distance between the mark and recapture sites over time, the difference was not significant. In addition, occurrences of two or more tagged fish from the same release event that were caught together indicated a non-random association among individual fish for periods of one to several years and through migrations over several hundred kilometres. Hence G. morhua showed group cohesion in addition to site fidelity. These two interacting behaviours may be fundamental for the rebuilding and conservation of depleted fish stocks.

Journal of Crustacean Biology, May 1, 2003

Journal of Experimental Marine Biology and Ecology, Jun 1, 2009

We compared predation rates and behaviours of sea stars (Asterias vulgaris and Leptasterias polar... more We compared predation rates and behaviours of sea stars (Asterias vulgaris and Leptasterias polaris) and crabs (Cancer irroratus and Hyas araneus) preying on juvenile sea scallops (Placopecten magellanicus, 25-35 mm shell height) in laboratory. These predatory species co-occur with sea scallops on the sea bed of the Gulf of St. Lawrence, Canada, and limit scallop survival in seeding operations. We also

Marine Ecology, Sep 1, 2007

The concept of geographic structure in marine ecosystems is fundamental for understanding populat... more The concept of geographic structure in marine ecosystems is fundamental for understanding population dynamics, for fisheries management, and for the implementation of conservation measures. The geographic structure of populations generally results from spatial distribution patterns that are related to historic or current barriers between local communities, such as geographic distance, environmental patchiness and environmental gradients that tend to keep populations from mixing freely (Bailey 1997). The geographic structure is often naturally fragmented, with a large habitat area subdivided into habitat patches. This has a major impact on population dynamics, community structure and ecosystem diversity. Habitat fragmentation tends to reduce the area of habitat patches and decreases the long-term survival probability of populations and communities. In such habitats, population sizes decrease and have a higher probability of going extinct because of environmental or demographic stochasticity and an increasing vulnerability to external influences (Saunders et al. 1991). Several authors refer to empirical knowledge about the evolutionary and adaptive mechanisms underlying the response of populations and

Journal of Crustacean Biology, Nov 1, 1987

ABSTRACT Observations with regard to the spatial distribution of juvenile Chionoecetes opilio, wi... more ABSTRACT Observations with regard to the spatial distribution of juvenile Chionoecetes opilio, with a carapace width (CW) &amp;lt;30 mm, were made in populations located off the north shore of the Gulf of St. Lawrence during the summer of 1982. Sampling was conducted using ...

The journal of cetacean research and management, Jan 24, 2023

Stranding records have long been used to monitor marine mammal mortalities and to help identify t... more Stranding records have long been used to monitor marine mammal mortalities and to help identify threats to populations. In coastal areas, marine mammals face numerous anthropogenic threats such as marine traffic and commercial fishing. The objective of this study was to investigate marine mammal stranding records from the St. Lawrence Estuary (SLE) and the northwestern Gulf of St. Lawrence (NWGSL), Quebec, Canada from 1994 to 2008 for evidence of anthropogenic trauma caused by entanglement in fishing gear, ship collisions and gunshots. Of 1,590 marine mammal stranding records, 12% (n = 192) had evidence of anthropogenic trauma, most incidents being reported during summer when activities such as marine traffic, most commercial fishing and recreational boating, occurred and a greater number of species were present in the area. These incidents were classified into five categories (Incidental catch, Ship collision, Severe injury, Gunshot, Other). There were 1,245 mortalities and observations on carcasses suggested that anthropogenic trauma led to the death of 11% (141/1,245) of marine mammals: 14% (87/627) of cetaceans and 9% (54/618) of seals. Mortality of seals due to anthropogenic trauma was low, involving mainly Gunshot for grey (26% or 8/31) and harbour seals (26% or 8/31). Over the study period, marine mammal incidents with evidence of anthropogenic trauma increased significantly, driven by an increase in Incidental catch for two mysticete species, the common minke whale, 42% (39/92) and humpback whale, 13% (12/92) and Other for harbour porpoise 67% (16/24). Ship collision was the most common anthropogenic trauma for fin whales (22% or 8/36) and SLE beluga 5 (22% or 8/36). Severe injury was reported for 22% (2/9) of small cetaceans and 78% (7/9) of seals. Evidence from some harbour porpoise stranding records (categorised as Other) suggests illegal hunting, incidental catch, predation or scavenging by grey seals in a marine protected area. The observed increase in Incidental catch of common minke and humpback whales may be due to: (1) a shift in distribution of these two species into the SLE and NWGSL, possibly related to changes in the ecosystem; (2) changes in fishery practices; and (3) an increase in detection of marine mammal strandings. Anthropogenic trauma affecting marine mammals was documented including some species at risk, such as the harbour porpoise, the St. Lawrence Estuary beluga population, blue and North Atlantic right whales, in the St. Lawrence ecosystem including in a marine protected area. This study demonstrates the usefulness of stranding records in helping to monitor human-caused mortality in marine mammal populations.

Marine Ecology Progress Series, May 28, 2018

Decapod shrimps typically occupy lower trophic levels, often as omnivores, and many have high pop... more Decapod shrimps typically occupy lower trophic levels, often as omnivores, and many have high population turnover rates, which makes shrimp populations susceptible to changes in predator abundance and environmental change. The increased biomass of northern shrimp Pandalus borealis in many parts of the NW Atlantic has been associated with the collapse of predatory fish populations and changes in water temperature. In this study, we show that biomass of many shrimp species in the Gulf of St. Lawrence (Canada) increased between 4-and 100-fold between the late 1980s and mid-2000s. Multivariate analyses based on trawl survey data during a period of relative stability (2004−2015) that followed the increase revealed species assemblages that were strongly spatially structured and which were associated with depth and bottom water temperatures. Univariate analyses of the associations between individual species' densities and depth and temperature revealed that approximately half of the species had narrow temperature associations, suggesting that these species may be susceptible to projected warming of the ecosystem. Furthermore, all species in the northern Gulf of St. Lawrence will be affected by recent and ongoing increases in predator biomass. In contrast, predator biomasses continue to decrease in the southern Gulf of St. Lawrence.