Effects of persistent organic pollutants on fish behaviour

Les PCB (polychlorobiphényles) sont des molécules connues pour leur longue demi-vie et leur forte liposolubilité qui conduisent à une bioaccumulation et une bioamplification dans les réseaux trophiques, menant à un potentiel risque pour les prédateurs de haut niveau tel que l’Homme. De plus, il a été démontré que leur affinité avec les composés lipidiques conduisaient à une transmission de la femelle à l’œuf chez les poissons. Dans ce contexte, et comme d’autres travaux ont déjà montré des effets des PCB sur la physiologie et le comportement d’animaux contaminés de différentes façons, nous avons observé les effets de ces molécules chez deux espèces, la sole commune et le poisson zèbre. La contamination a été réalisée via l’alimentation avec deux mélanges de PCB et deux concentrations qui correspondent à des situations environnementales, en termes de dose ou de choix et de proportion des congénères retenus. La dose la plus haute est équivalente à celle mesurée dans de la chair de molusques en baie de Seine et la dose intermédiaire à celle mesurée en estuaire de Loire. Les soles contaminées ont montré une diminution du niveau d’activité locomoteur après 30 jours (j) de contamination et une altération des capacités cryptiques après 60 j de contamination. Les poissons zèbre contaminés ont montré une augmentation de l’activité locomotrice après 250 j de contamination. La génération issue de cette génération de poisson zèbre contaminée a elle aussi montré une augmentation de l’activité locomotrice au stade larvaire et adulte. Chez les adultes, cela s’est traduit par une diminution de l’utilisation de la zone de fond des bacs et une augmentation du nombre de transition de zones, ce qui s’explique par une perte d’inhibition comportementale. Dans les deux cas, les phénotypes comportementaux observés chez les groupes PCB sont associés à une altération de la locomotion dans le sens d’une baisse d’activité pour une espèce placide comme la sole et dans le sens de l’augmentation pour une espèce mobile comme le poisson zèbre.Because of their long biological half-life and high liposolubility, PCBs (polychlorinated biphenyls) are bioaccumulated and biomagnified through food chains over a wide range of trophic levels, leading to a potential risk for high trophic level predators including humans. Further, due to their binding with lipids, a demonstrated maternal transfer to eggs exists in fish. In this context, and since field analyses and experimental exposures have established links between PCBs exposure and alterations in physiology and behaviour of contaminated animals, we have examined the effects in both common sole and zebrafish species exposed through diets to two PCBs mixtures at two doses mimicking known environmental contamination levels and congener composition. The highest dose was equivalent to that found in molluscs flesh in the Seine Estuary and the intermediate dose was equivalent to that found in the Loire estuary. Contaminated soles showed a decreased locomotor activity level after 30 days (d) of contamination and altered cryptic abilities after 60 d of contamination. Contaminated zebrafish showed an increased locomotor activity level after 250 d of contamination. The offspring obtained from this contaminated generation of zebrafish showed an increase in swimming activity in larvae which was maintained in adults. In adults, this was associated with a decrease in tank bottom section occupancy and with an increase in the number of zone transition which may be due to a loosening of homebase behaviour and/or a loss of behavioural inhibition. In both cases, behavioural phenotypes observed in PCBs groups can be related to a disruption in locomotion activity towards decreased levels for a placid species like common sole and increased levels for a mobile species like zebrafish

Effets des polluants organiques persistants sur le comportement des poissons

Because of their long biological half-life and high liposolubility, PCBs (polychlorinated biphenyls) are bioaccumulated and biomagnified through food chains over a wide range of trophic levels, leading to a potential risk for high trophic level predators including humans. Further, due to their binding with lipids, a demonstrated maternal transfer to eggs exists in fish. In this context, and since field analyses and experimental exposures have established links between PCBs exposure and alterations in physiology and behaviour of contaminated animals, we have examined the effects in both common sole and zebrafish species exposed through diets to two PCBs mixtures at two doses mimicking known environmental contamination levels and congener composition. The highest dose was equivalent to that found in molluscs flesh in the Seine Estuary and the intermediate dose was equivalent to that found in the Loire estuary. Contaminated soles showed a decreased locomotor activity level after 30 days (d) of contamination and altered cryptic abilities after 60 d of contamination. Contaminated zebrafish showed an increased locomotor activity level after 250 d of contamination. The offspring obtained from this contaminated generation of zebrafish showed an increase in swimming activity in larvae which was maintained in adults. In adults, this was associated with a decrease in tank bottom section occupancy and with an increase in the number of zone transition which may be due to a loosening of homebase behaviour and/or a loss of behavioural inhibition. In both cases, behavioural phenotypes observed in PCBs groups can be related to a disruption in locomotion activity towards decreased levels for a placid species like common sole and increased levels for a mobile species like zebrafish.Les PCB (polychlorobiphényles) sont des molécules connues pour leur longue demi-vie et leur forte liposolubilité qui conduisent à une bioaccumulation et une bioamplification dans les réseaux trophiques, menant à un potentiel risque pour les prédateurs de haut niveau tel que l’Homme. De plus, il a été démontré que leur affinité avec les composés lipidiques conduisaient à une transmission de la femelle à l’œuf chez les poissons. Dans ce contexte, et comme d’autres travaux ont déjà montré des effets des PCB sur la physiologie et le comportement d’animaux contaminés de différentes façons, nous avons observé les effets de ces molécules chez deux espèces, la sole commune et le poisson zèbre. La contamination a été réalisée via l’alimentation avec deux mélanges de PCB et deux concentrations qui correspondent à des situations environnementales, en termes de dose ou de choix et de proportion des congénères retenus. La dose la plus haute est équivalente à celle mesurée dans de la chair de molusques en baie de Seine et la dose intermédiaire à celle mesurée en estuaire de Loire. Les soles contaminées ont montré une diminution du niveau d’activité locomoteur après 30 jours (j) de contamination et une altération des capacités cryptiques après 60 j de contamination. Les poissons zèbre contaminés ont montré une augmentation de l’activité locomotrice après 250 j de contamination. La génération issue de cette génération de poisson zèbre contaminée a elle aussi montré une augmentation de l’activité locomotrice au stade larvaire et adulte. Chez les adultes, cela s’est traduit par une diminution de l’utilisation de la zone de fond des bacs et une augmentation du nombre de transition de zones, ce qui s’explique par une perte d’inhibition comportementale. Dans les deux cas, les phénotypes comportementaux observés chez les groupes PCB sont associés à une altération de la locomotion dans le sens d’une baisse d’activité pour une espèce placide comme la sole et dans le sens de l’augmentation pour une espèce mobile comme le poisson zèbre

Self-feeding behavior changes induced by a first and a second generation of domestication or selection for growth in the European sea bass,

Among the strategies that can be used to improve fish welfare in a rearing environment, domestication and/or selective breeding was proposed to minimize fish responsiveness to husbandry practices. To verify this hypothesis on a recently domesticated species, the sea bass Dicentrarchus labrax, two experiments were realized, each using two populations differing according to their level of domestication or selection. For the first experiment, we used one population produced from wild parents (Wild; initial body mass: 106  ±  3 g), and one population from parents selected for growth for one generation (Selected 1; initial body mass: 129  ±  4 g). For the second experiment, we used one population produced from parents domesticated for two generations (Domesticated; initial body mass: 72  ±  3 g), and one produced from parents selected for growth for two generations (Selected 2; initial body mass: 89  ±  4 g). The first experiment was carried out over 112 days with 240 fish (60 fish per tank, 120 fish per population), and the second one over 84 days with 200 fish (50 fish per tank, 100 fish per population). Two variables, self-feeding behavior and growth performance, were measured over the time of the experiments. After a control period, the fish were submitted twice, at three-week intervals, to an acute stress treatment consisting of draining the tank and leaving the fish out of water for one minute. Both self-feeding behavior and growth performance were altered by the acute stress treatment. During the first post-stress period, the Domesticated and Selected (1 and 2) groups showed more pronounced post-stress exposure responses than the Wild fish: they modified their feeding rhythm, their feed intake, and their growth rate. During the second post-stress period, feeding rhythm was still affected (being more diurnal with a well defined peak), but the feed intake and growth rate results showed that the Domesticated and Wild groups seemed less affected than the Selected (1 and 2) populations, which continued to express a high post-stress response. According to these results, it can be concluded that: (1) an application of two acute stress treatments, at three-week intervals, modified fish feeding behavior and growth performance; (2) the domestication process seemed to improve fish adaptation abilities to this kind of stress; and (3) the process of selection for growth led to a final, better growth, but did not seem to improve fish acute stress tolerance

Effect of size grading on sea bass (

This study aims to test the influence of size grading on self-feeding behaviour, social structure (measured by the percentage of triggering acts per individual), growth performances, and blood physiological variables of individually passive integrated transponder (PIT)-tagged sea bass juveniles, using a computerized on-demand feeding system coupled with a PIT tag monitoring device. Three consecutive periods of 27 days each were compared: a first period (P1) before grading (6 tanks of 100 fish; 40.2  ±  8.9 g) followed by a second period (P2) after grading. The protocol applied aimed to create two groups of fish of similar mean weight but with either a low or a high coefficient of variation of weight (CVw) corresponding to an imposed difference in social disruption (Tlow: CVw ~ 10%, 3 tanks of 60 fish each with social disruption; Thigh:CVw ~20%, 3 tanks of 60 fish each, without social disruption). Tlow and Thigh groups were studied over P2, and an additional 27-day period under identical conditions (P3). The grading protocol used and/or time modified the social structure when comparing P1 and P2. Thereafter, during P2 and P3, no difference could be observed in growth performances, feed demand, or physiological variables between Tlow and Thighgroups. Feeding rhythms and social structures were similar in both groups. In conclusion, such grading practice only transiently modifies feed demand behaviour and social structure built around the self-feeder, without further improvement in individual growth performances in sea bass

Impact of a plant-based diet on behavioural and physiological traits in sea bass (Dicentrarchus labrax)

Replacing aquaculture feeds based on fisheries-derived resources with plant-based diets could be a relevant strategy to improve the sustainability of aquaculture. Recent studies on sea bass have shown that the total and early replacement of marine products by plant products would have a moderate effect on fish growth and body lipid content. Whether a plant-based diet impacts behavioural and physiological traits possibly linked to fish welfare, is not known, however. Here, we studied the effect of a totally plant-based diet introduced at an early stage of sea bass development on self-feeding behaviour, learning ability in a T-maze and stress biomarkers. We first compared learning processes in self-feeding conditions, between naive fish fed a plant-based diet (PBF) and fish fed a classic marine diet (MF). Then, we tested fish individually in a T-maze to compare the two feed groups for swimming activity, exploration and the ability to learn to discriminate between two two-dimensional objects associated with a reward. Blood physiological variables, including stress indicators (cortisol and glucose concentrations), were also determined. We did not find any indications of differences in self-feeding behaviour between PBF and MF in the first 30 days. A second experiment showed similar swimming activities in both fish categories. The “no-choice” percentage was high in both fish categories (~60%), but all the fish moved preferentially toward the reward. Their first turns indicated an ability to discriminate between two two-dimensional objects to complete a simple task. However, the high percentage of “no-choice” responses in both fish categories could have rendered the results non significant. The T-maze test procedure induced the production of high concentrations of cortisol, indicating acute stress in fish of both groups during testing. Plasma cortisol concentration was higher in MF than PBF, suggesting that the plant-based diet may affect the short-term release of cortisol. This study provides the first insight into the impact of a plant-based diet on sea bass behavioural traits, and confirms the effect of this diet on cortisol release in response to stress. Overall, in this first experiment, we did not find any major impact of a plant-based diet on sea bass behavioural traits, which is an interesting point for the development potential of such a sustainable aquaculture strategy

Long term effects of an early exposure to PAHs on Zebrafish behavioural responses

International audiencePolycyclic aromatic hydrocarbons (PAH) emission in the environment is constantly increasing with human activity. The goal of this study was to assess long term consequences of fish early exposure to PAH on behaviour. Eggs were collected from AB zebrafish strain and were placed at 4 hours post fertilization (hpf) until 96 hpf in a 3 cm diameter Petri dish containing 3 g reference sediment either plain (control) or spiked with a mixture of Benzo[a]pyrene, Pyrene and Phenanthrene at environmental concentrations based on values measured in the Seine Estuary (France), a highly polluted site. Thereafter, larvae were transferred in clean water and raised until adulthood. Behavioural tests such as locomotion during 24-hrs, sudden dark change challenge and T-maze exploration were performed at adults’ stage (F0) and sudden dark change on larvae produced by F0 adults. In adults, during night or dark period, contaminated fish were significantly less active than control fish. A similar observation was made for contaminated F0 in T-maze safe area. Contaminated F1 larvae were more active when light was on than control and less active when the light was off. This study indicates that contamination of zebrafish using environmentally relevant concentration during the very first stage of development with a PAH mixture of 3 molecules induced late behavioural effects measured at the adult stage. Further, effect was transmitted to the next generation and behavioural responses of F1 larvae were different to that of F1 control larvae. Consequences on fish abilities (e.g. predator escape, food search, courtship) will be discussed

Long term effects of an early exposure to PAHs on Zebrafish behavioural responses

International audiencePolycyclic aromatic hydrocarbons (PAH) emission in the environment is constantly increasing with human activity. The goal of this study was to assess long term consequences of fish early exposure to PAH on behaviour. Eggs were collected from AB zebrafish strain and were placed at 4 hours post fertilization (hpf) until 96 hpf in a 3 cm diameter Petri dish containing 3 g reference sediment either plain (control) or spiked with a mixture of Benzo[a]pyrene, Pyrene and Phenanthrene at environmental concentrations based on values measured in the Seine Estuary (France), a highly polluted site. Thereafter, larvae were transferred in clean water and raised until adulthood. Behavioural tests such as locomotion during 24-hrs, sudden dark change challenge and T-maze exploration were performed at adults’ stage (F0) and sudden dark change on larvae produced by F0 adults. In adults, during night or dark period, contaminated fish were significantly less active than control fish. A similar observation was made for contaminated F0 in T-maze safe area. Contaminated F1 larvae were more active when light was on than control and less active when the light was off. This study indicates that contamination of zebrafish using environmentally relevant concentration during the very first stage of development with a PAH mixture of 3 molecules induced late behavioural effects measured at the adult stage. Further, effect was transmitted to the next generation and behavioural responses of F1 larvae were different to that of F1 control larvae. Consequences on fish abilities (e.g. predator escape, food search, courtship) will be discussed

Long term effects of an early exposure to PAHs on zebrafish behavioural responses

International audienc

Laboratoire d'écophysiologie des poissons : Ifremer La Rochelle

National audienc