Denis Chabot

Fisheries and Oceans Canada | DFO · Maurice Lamontagne Institute (MLI)

Species with a wide distribution can experience regionally a wide range of environmental conditions, to which they can acclimatize or adapt. Consequently, the geographic origin of an organism can influence its responses to environmental changes, and therefore its sensitivity to combined global change drivers. This study aimed at determining the phy...

Impacts of global ocean changes on species have historically been investigated at the whole-organism level. However, acquiring an in-depth understanding of the organisms' cellular metabolic responses is paramount to better define their sensitivity to environmental challenges. This is particularly relevant for species that experience highly differen...

Genetic variation underlies the populations’ potential to adapt to and persist in a changing environment, while phenotypic plasticity can play a key role in buffering the negative impacts of such change at the individual level. We investigated the role of genetic variation in the thermal response of the northern shrimp Pandalus borealis, an ectothe...

In the northern Gulf of St. Lawrence (nGSL), redfish (Sebastes mentella and S. fasciatus combined) are at record levels of abundance following the strong recruitment of three consecutive cohorts in 2011-2013 and have become by far the most abundant demersal fish in the region. Understanding redfish trophic relationships is essential for the effecti...

Redfish ( Sebastes mentella and S. fasciatus ) are back at spectacular record high levels in the Gulf of St. Lawrence (GSL) and the effects of this massive resurgence on other components of the food web remain largely unknown. To better understand the trophic implications of the surging redfish biomass within the GSL ecosystem, 3,690 stomachs conta...

In order to obtain a fishery-independent index covering a significant portion of the Gulf of St. Lawrence (GSL, NAFO Divisions 4RST) capelin (Mallotus spp.) stock area, the stomach contents of Atlantic cod (Gadus morhua) and Greenland halibut (Reinhardtius hippoglossoides) collected during the summer nGSL multispecies survey were examined. Using a...

Climate change is already affecting the forest sector, especially through extreme events such as wildfire. These effects are expected to continue and intensify, requiring greater efforts to implement adaptation measures. While no single road map exists to guide adaptation implementation, regional risk assessments in Canada have highlighted the need...

Our analysis shows good intentions in the selection of valid and precise oxygen uptake (ṀO2) measurements by retaining only slopes of declining dissolved oxygen level in a respirometer that have very high values of the coefficient of determination, r², are not always successful at excluding nonlinear slopes. Much worse, by potentially removing line...

Coastal nursery areas are subjected to a wide range of natural and anthropogenic stressors, including global warming, which indirectly influence trophic food webs. A global rarefaction of n-3 polyunsaturated fatty acids (PUFA) in trophic networks is in progress. The aim of this study was to assess the effect of a reduction in the dietary availabili...

This document summarizes the stomach sampling effort carried out during the August ecosystemic surveys conducted from 2015 to 2017 by the Quebec Region in the lower estuary and northern gulf of St. Lawrence. Descriptive analyses of summer diets are provided for 10 demersal fishes (11 species): black dogfish (Centroscyllium fabricii), thorny skate (...

Nutritional and organoleptic qualities (taste, smell, texture, appearance) are key characteristics of seafood when it comes to defining consumer choices. These qualities, which are determined by the biochemical properties of the seafood, can be altered by environmental conditions, such as those imposed by ongoing global ocean change. However, these...

• Breathing water is hard work, making the physiological performance and behavioural Repertoire of marine organisms heavily dependent on their capacity to extract oxygen from the ambient sea water. • There is no such thing as an oxygen threshold above which everything is fine and below which survival is at risk and conservation measures should be i...

The accumulation of CO2 in the atmosphere and resulting ocean acidification represent a threat to marine ecosystems. While acid–base regulatory capacity is well developed in marine fish, allowing compensation of extra-cellular pH during short-term hypercapnia, the possible energetic costs of such regulation during long-term exposure remain to be es...

This chapter shows that cod physiology is profoundly influenced by temperature, and a cod living at 0 °C is in many ways a different animal than a cod living at 12 °C. Cod populations also occur along inshore‐offshore gradients that generate an even more complicated array of environmental factors that this species must deal with. The chapter review...

Global climate changes have led to a depletion in omega-3 polyunsaturated fatty acids (n-3 PUFA) in marine phytoplankton that—with food web transfers—could negatively impact fish performance. The aim of this study was to assess the effect of a reduction in the dietary availability of n-3 PUFA on growth performance, organ allometry, and fatty acid c...

Two dominant krill species Meganyctiphanes norvegica (Sars, 1857) and Thysanoessa raschii (Sars, 1864) coexist in the subarctic waters of lower St. Lawrence Estuary, Canada. Both species perform diel vertical migrations representing often large displacements of ~100–150 m through several temperature regimes. We studied the impact of temperature, a...

Like many marine species around the globe, several stocks of Atlantic cod (Gadus morhua) live in increasingly hypoxic waters. In the Gulf of Saint Lawrence (GSL) in Canada, the deep channels traversing the semi-enclosed sea exhibit year-round hypoxia, identified as one of the limiting factor for the recovery of GSL cod in its northern part. While m...

Hypoxia is a decrease in dissolved oxygen that causes physiological disturbances in marine fishes and invertebrates, including reduced mobility, growth rate and reproductive success, altered phenology and increased vulnerability to diseases. Under pressure from global changes such as warming or eutrophication, ocean and coastal ecosystems worldwide...

In order to define the relative vulnerability of northern shrimp (Pandalus borealis) populations to the ongoing global warming, we compared the thermal performance curves for survival and growth in the first three pelagic larval stages from three populations of the Northwest Atlantic. Egg carrying females were obtained from different regions charac...

Standard metabolic rate, SMR, or the totality of energy-consuming, manipulative and storage chemical reactions undertaken by fish to maintain life is the topic of this article. The factors that account for SMR and measurement theory are considered. Despite decades of effort, there is no universal method for measuring SMR, and various methods and ge...

The state of the art of research on the environmental physiology of marine fishes is reviewed from the perspective of how it can contribute to conservation of knowledge for conservation of marine fishes is the limited knowledge base; international collaboration is needed to study the environmental physiology of a wider range of species. Multifactor...

We have learned much about the impacts of warming on the productivity and distribution of marine organisms, but less about the impact of warming combined with other environmental stressors, including oxygen depletion. Also, the combined impact of multiple environmental stressors requires evaluation at the scales most relevant to resource managers....

For many years, operational frameworks to guide ecosystem-based science in support of integrated marine management have been sought to address causes of marine ecosystem degradation resulting from human activities such as fisheries, industrial development, aquaculture, etc. In 2007, the Canadian Department of Fisheries and Oceans developed several...

The pace-of-life syndrome (POLS) hypothesis1 specifies that closely related species experiencing different ecological conditions should differ in a suite of metabolic traits that have coevolved with the life-history particularities . The notion of POLS finds its roots in the classic concept of r and K-selection. It also extends into the more recent...

A mechanistic, prey surface-dependent model was expanded to describe the course and rate of gastric evacuation in predatory fishes feeding on crustacean prey with robust exoskeletons. This was accomplished by adding a layer of higher resistance to the digestive processes outside the inner softer parts of a prey cylinder abstraction and splitting up...

This review and data analysis outline how fish biologists should most reliably estimate the minimal amount of oxygen needed by a fish to support its aerobic metabolic rate (termed standard metabolic rate; SMR). By reviewing key literature, it explains the theory, terminology and challenges underlying SMR measurements in fishes, which are almost alw...

The problem of understanding the effect of the environment on fish activities and performance, in any generalized way, remains intractable. Solving this issue is, however, a key to addressing contemporary environmental concerns. As suggested 20 years ago by W. H. Neill, the authors returned to the drawing board, using as a background the conceptual...

Specific dynamic action (SDA) is the postprandial increase in oxygen uptake. Whereas it is easy to measure in fishes that remain calm and motionless during the entire digestion period, spontaneous locomotor activity is a frequent problem that leads to overestimation of SDA amplitude and magnitude (area under the curve, bound by the standard metabol...

Society is moving towards a no-analogue climate that will fundamentally affect ocean ecosystems and the socio-economic activities that depend on them. Warming has led to displacements of various populations, calling for an adaptation of fisheries management plans and Species at Risk recovery strategies. Dissolved oxygen (DO) has declined, but its i...

An important proportion of the deep channels that characterize the Gulf of St. Lawrence (GSL) bathe in hypoxic waters. Since the 1930s, an important reduction in dissolved oxygen (DO) levels was observed in the Lower St. Lawrence Estuary (LSLE) and attributed in part to changes in deep water flowing in from the Atlantic and in part to local forcing...

In Canada, interest in a potential new krill source focusses on the evaluation of biochemical composition of northern and arctic krill for nutraceutical, cosmetic and pharmaceutical industries. Our prime objective is to examine the ecological resilience of the krill stocks in the St. Lawrence system prior to human exploitation. Krill stocks must co...

Recent models project a general warming trend for the surface, cold intermediate and deep layers that characterize the Estuary and Gulf of St. Lawrence (EGSL) in summer. Further, waters will be more acidic and the deep layer will be even more hypoxic than today. These changes will influence the physiology of fish and crustaceans, including commerci...

Prinet, A. ; Pillet, M. ; Chabot, D. ; Tremblay, R. & Audet, C.

This study examined the effects of prey exoskeleton characteristics on gastric evacuation patterns in Atlantic cod Gadus morhua. Three distinct stages were highlighted in the gastric evacuation of crustacean prey characterized by a robust exoskeleton. The experiments confirmed that the three shrimp species, Pandalus borealis, Pandalus montagui and...

Greenland halibut, especially juveniles, are frequently found in severely hypoxic areas (18–25% saturation) of the St. Lawrence Estuary. We investigated the tolerance of this species to hypoxia and evaluated the consequences of low oxygen levels on metabolic capacity. At 5°C, juveniles had a higher critical oxygen threshold than adults (15 vs 11% s...

Dans la couche d'eau profonde de l'estuaire et du Golfe du Saint-Laurent, les niveaux d'oxygène dissous sont très faibles tout au long de l'année. L'hypoxie est un phénomène connu pour avoir de nombreux impacts sur les espèces aquatiques. La crevette nordique Pandalus borealis est abondamment présente dans cette couche d'eau profonde, notamment dan...

This study shows that a sharp ecosystem transition in dominant communities during the early 1990s, from finfish to crustaceans, was common to the 2 northernmost Northwest Atlantic ecosystems, the Newfoundland−Labrador shelf (NL) and the northern Gulf of St. Lawrence (nGSL). Fishery and survey data show that populations of Atlantic cod Gadus morhua,...

Standard metabolic rate (SMR) or the totality of energy-consuming, manipulative, and storage chemical reactions undertaken by fish to maintain life is the topic of this article. The factors that account for SMR and measurement theory are considered. Despite decades of effort, there is no universal method for measuring SMR, and various methods and g...

Using a sample of 150 female and 141 male foetal Northwest Atlantic harp seals (Phoca groenlandica) collected between October and February of 1980-1995, we determined that the allometric relationship between total body mass and standard length did not differ between sexes and did not differ from the relationship calculated for foetal harp seals fro...

Growth of Pandalus borealis post-larval stages was measured in relation to size and temperature. Growth characteristics, including intermolt period (IP), molt increment (MI) in size and mass, and tissue allocation in juvenile, male, and female shrimp, were evaluated at 2, 5, and 8°C, the temperature range where this species is generally found in th...

In the deeper water layer of the estuary and Gulf of Saint-Lawrence, oxygen levels are very low all year long. It is well known that hypoxia has a wide range of effects on animal species. Northern shrimp are abundant in the deeper layer of the Laurentian channel where oxygen levels are often below 30% air saturation. In order to understand the dist...

In an attempt to minimize observer bias, numerical taxonomy methods were used to describe and classify humpback whale sounds. The spectrograms (N = 1255) were digitized into a 16 × 21 binary matrix. The rows were 16 frequencies selected on a logarithmic scale (0.12–8 kHz). The columns were 21 time samples taken every 0.1 s. Each point of the matrix...

Seasonal changes in energy intake of northwest Atlantic harp seals were modelled and implemented as a Microsoft Excel™ spreadsheet. Energy intake of adults during the fourth quarter is almost double estimated intake during the second quarter, with intermediate values during the first and third quarters. Reproduction increases female annual energy r...

In order to have a global view of ecosystem changes associated with the collapse of groundfish species in the Gulf of St. Lawrence during the early 1990s, Ecopath mass-balance models were constructed incorporating uncertainty in the input data. These models covered two ecosystems (northern and southern Gulf of St. Lawrence; NAFO divisions 4RS and 4...

Mass-balance models were used to reconstruct trophic flows through the whole northern Gulf of St. Lawrence ecosystem (NAFO divisions 4RS) for the 2003–2005 period. The whole-system model of the northern Gulf of St. Lawrence is divided into 31 functional groups or compartments from phytoplankton and detritus to marine mammals and seabirds, including...

Hypoxia is known to provoke a wide range of effects on aquatic animals. Here we use laboratory and field data on Atlantic cod, Gadus morhua, to illustrate that many of these responses can be explained within the metabolic scope (MS) framework, i.e. taking into account the directive and limiting effects of dissolved oxygen (DO) on the ability of ani...

Themisto libellula was virtually absent from the St. Lawrence marine system (SLMS) before 1990. Since then, it has become an abundant, full-time resident of this system. Hyperiid amphipods of the genus Themisto are principally carnivorous and represent an essential link in the trophic pathway from secondary production to higher trophic levels. Samp...

Atlantic cod Gadus morhua stomach contents (n = 30 973, including 28 377 non-empty stomachs) and morphometric measurements on live snow crab Chionoecetes opilio and cod were examined to assess the predator-prey relationship between these 2 species. The most common snow crab instars found in cod stomachs were III and V (-∼6 to 8 and ∼12 to 16 mm car...

Abundance of many Atlantic cod (Gadus morhua) and groundfish stocks in the Northwest Atlantic declined to low levels in the early 1990s, resulting in cessation of directed fishing for these stocks, thus ending one of the largest and longest running commercial groundfish fisheries in the world. The stocks of the northern (nGSL) and southern Gulf of...

This is an English version of Chabot et al. 2007

The impact of temperature on oxygen consumption (MO2) of Pandalus borealis was measured in the laboratory for juvenile, male and female shrimp at 2, 5 and 8 °C, the temperature range where P. borealis is generally found in the Northwest Atlantic. Measurements of MO2 were taken every 60 min over 7–10 days on 0.22 to 13.80 g shrimp. These long-term m...

Mass-balance models have been constructed using inverse methodology for the northern Gulf of St. Lawrence for the mid-1980s, the mid-1990s, and the early 2000s to describe ecosystem structure, trophic group interactions, and the effects of fishing and predation on the ecosystem for each time period. Our analyses indicate that the ecosystem structur...

Mass-balance models, using inverse methodology, were applied to the southern Gulf of St. Lawrence for the mid-1980s and the mid-1990s to describe ecosystem structure, trophic group interactions, and the effects of fishing and predation on the ecosystem for periods preceding and following the collapse of groundfish stocks in this area. These models...

Les concentrations d’oxygène ont baissé de moitié depuis les années 1930 dans l’estuaire maritime du Saint-Laurent, à 300 m de profondeur. Un accroissement de la proportion d’eau chaude et pauvre en oxygène du Gulf Stream, au détriment de la proportion d’eau froide et bien oxygénée du courant du Labrador, expliquerait entre la moitié et les deux ti...

An Atlantic Halibut (Hippoglossus hippoglossus) (41.4 cm fork length) with the same pigmentation on the blind side as on the ocular side (ambicoloration) was captured in the lower St. Lawrence estuary, Canada, on 24 June 2004. This specimen represents the most extreme case of ambicoloration published for this species to date. As in other cases of e...