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Chary, K., Callier, M. D., Covès, D., Aubin, J., Simon, J., & Fiandrino, A. (2021). Scenarios of fish waste deposition at the sub-lagoon scale: a modelling approach for aquaculture zoning and site selection. ICES Journal of Marine Science, (fsaa238).
Résumé: Spatial planning, including zoning and site-selection steps, is necessary to determine locations that minimize environmental impacts of aquaculture and respect ecosystem carrying capacities. This study aimed to analyse potential benthic waste deposition in a broad range of fish farming situations to facilitate zoning. To this end, we simulated waste dispersion for 54 aquaculture scenarios combining three red drum (Sciaenops ocellatus) farm types (Small, Medium, and Large) based on real farm characteristics and 36 sites with contrasting hydrodynamics in Mayotte’s North-East Lagoon. Key forcing variables and parameters of the particle-dispersion model for farms (layout and solid waste fluxes), species (feed- and faeces-settling velocities) and sites (depth and barotropic currents) were obtained. From the outputs of the 54 simulations, relationships between hydrodynamic regimes and deposition rates, area of influence and distance of influence of the farm were analysed. Critical limits of current intensity that reduced deposition rate below selected deposition thresholds were identified. For instance, to prevent deposition rates greater than 12 kg solids m−2 year−1, the mean current intensity should exceed 10.2 and 6.8 cm s−1 for Medium and Large farms, respectively. The study confirmed that production level is not the main factor that influences deposition rates; instead, management of the entire farm (cage position, distance between cages) must be considered to predict impacts more accurately and guide site selection.
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Chassot, E., Antoine, S., Guillotreau, P., Lucas, J., Assan, C., Marguerite, M., et al. (2021). Fuel consumption and air emissions in one of the world’s largest commercial fisheries. Environmental Pollution, , 116454.
Résumé: The little information available on fuel consumption and emissions by high seas tuna fisheries indicates that the global tuna fleet may have consumed about 2.5 Mt of fuel in 2009, resulting in the production of about 9 Mt of CO2-equivalent greenhouse gases (GHGs), i.e., about 4.5-5% of the global fishing fleet emissions. We developed a model of annual fuel consumption for the large-scale purse seiners operating in the western Indian Ocean as a function of fishing effort, strategy, and vessel characteristics based on an original and unique data set of more than 4,300 bunkering operations that spanned the period 2013-2019. We used the model to estimate the total fuel consumption and associated GHG and SO2 emissions of the Indian Ocean purse seine fishery between 1981 and 2019. Our results showed that the energetic performance of this fishery was characterized by strong interannual variability over the last four decades. This resulted from a combination of variations in tuna abundance but also changes in catchability and fishing strategy. In recent years, the increased targeting of schools associated with fish aggregating devices in response to market incentives combined with the IOTC management measure implemented to rebuild the stock of yellowfin tuna has strongly modified the productivity and spatio-temporal patterns of purse seine fishing. This had effects on fuel consumption and air pollutant emissions. Over the period 2015 to 2019, the purse seine fishery, including its support vessel component, annually consumed about 160,000 t of fuel and emitted 590,000 t of CO2-eq GHG. Furthermore, our results showed that air pollutant emissions can be significantly reduced when limits in fuel composition are imposed. In 2015, SO2 air pollution exceeded 1,500 t, but successive implementation of sulphur limits in the Indian Ocean purse seine fishery in 2016 and 2018 have almost eliminated this pollution. Our findings highlight the need for a routine monitoring of fuel consumption with standardized methods to better assess the determinants of fuel consumption in fisheries and the air pollutants they emit in the atmosphere.
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de Oliveira, J., Chadili, E., Turies, C., Brion, F., Cousin, X., & Hinfray, N. (2021). A comparison of behavioral and reproductive parameters between wild-type, transgenic and mutant zebrafish: Could they all be considered the same “zebrafish” for reglementary assays on endocrine disruption? Comp. Biochem. Physiol. C-Toxicol. Pharmacol., 239, 108879.
Résumé: Transgenic zebrafish models are efficiently used to study the effects of endocrine disrupting chemicals (EDC); thereby informing on their mechanisms of action. However, given the reported differences between zebrafish strains at the genetical, physiological and behavioral levels; care should be taken before using these transgenic models for EDC testing. In the present study, we undertook a set of experiments in different transgenic and/or mutant zebrafish strains of interest for EDC testing: casper, cyp19a1a-eGFP, cyp19a1a-eGFP-casper, cyp11c1-eGFP, cypncl-eGFP-casper. Some behavioral traits, and some biochemical and reproductive physiological endpoints commonly used in EDC testing were assessed and compared to those obtained in WT AB zebrafish to ensure that transgene insertion and/or mutations do not negatively modify basal reproductive physiology or behavior of the fish. Behavioral traits considered as anxiety and sociality have been monitored. Sociality was evaluated by monitoring the time spent near congeners in a shuttle box while anxiety was evaluated using the Novel tank diving test. No critical difference was observed between strains for either sociality or anxiety level. Concerning reproduction, no significant difference in the number of eggs laid per female, in the viability of eggs or in the female circulating VTG concentrations was noted between the 5 transgenic/mutants and the WT AB zebrafish studied. In summary, the transgene insertion and the mutations had no influence on the endpoints measured in basal conditions. These results were a prerequisite to the use of these transgenic/mutant models for EDC testing. Next step will be to determine the sensitivity of these biological models to chemical exposure to accurately validate their use in existing fish assays for EDC testing.
Mots-Clés: adult zebrafish; Behavior; Casper; danio-rerio; exposure; fish; genetic-variation; levonorgestrel; mutations; pigmentation; Reproduction; responses; sex-ratio; Transgenic; Zebrafish
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Douhard, M., & Geffroy, B. (2021). Males can adjust offspring sex ratio in an adaptive fashion through different mechanisms. BioEssays, , 2000264.
Résumé: Sex allocation research has primarily focused on offspring sex-ratio adjustment by mothers. Yet, fathers also benefit from producing more of the sex with greater fitness returns. Here, we review the state-of-the art in the study of male-driven sex allocation and, counter to the current paradigm, we propose that males can adaptively influence offspring sex ratio through a wide variety of mechanisms. This includes differential production and motility of X- versus Y-bearing sperms in mammals, variation in seminal fluid composition in haplo-diploid invertebrates, and epigenetic mechanisms in some fish and lizards exhibiting environmental sex determination. Conflicts of interest between mothers and fathers over offspring sex ratios can emerge, although many more studies are needed in this area. While many studies of sex allocation have focused on adaptive explanations with little attention to mechanisms, and vice versa, the integration of these two topics is essential for understanding male-driven sex allocation.
Mots-Clés: fathers; seminal fluid; sex allocation; sex ratio; sexual conflict; spermatozoa
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Goikoetxea, A., Sadoul, B., Blondeau-Bidet, E., Aerts, J., Blanc, M. - O., Parrinello, H., et al. (2021). Genetic pathways underpinning hormonal stress responses in fish exposed to short- and long-term warm ocean temperatures. Ecological Indicators, 120, 106937.
Résumé: Changes in ocean water temperature associated with global climate change are bound to enormously affect fish populations, with potential major economic consequences in the aquaculture and fisheries industries. A link between temperature fluctuations and changes in fish stress response is well established. In this study, we aimed to assess the effects of a short- (4 days) or a long-term (4 months) exposure to warm temperature in the stress physiology of European sea bass (Dicentrarchus labrax) larvae and juveniles. First, cortisol (i.e. the main stress hormone in fishes) analysis was used to confirm that a steady and short-term elevation of temperature acts as a physiological stressful event in these fish, and cortisol release is indeed above a metabolic increase linked to temperature. Moreover, our results verified that measurement of cortisol released into the water can be reliably employed as a non-invasive indicator of acute thermal stress in experimental conditions. Secondly, the different effects on the genetic cascade underlying the stress response between long-term low or high thermal treatments were evaluated at two larval development stages via candidate-gene and whole-transcriptome approaches. Interestingly, opposite expression for some key stress genes (nr3c1, nr3c2 and hsd11b2) were observed between developmental stages, highlighting the distinct adaptive mechanisms controlling the primary and secondary responses to a stressor. Surprising expression patterns for some understudied genes involved in the stress axis were also revealed, including crhr1, mc2r, mc5r, trh or trhr, which should be further explored. Finally, evaluation of cortisol content in scales was successfully used as a biomarker of chronic thermal stress, with 10x more cortisol in fish kept at 21 °C vs 16 °C after 4 months, supporting the gene expression results observed. The use of such a method as a proxy of long-term stress, unprecedented in the literature, holds a vast array of applications in further research, in particular, in the investigation of the impact of global warming on wild fish populations.
Mots-Clés: Commercial fish; Cortisol; Glucocorticoid receptors; Scales; Transcriptomics
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