Body size and temperature effects on standard metabolic rate for determining metabolic scope for activity of the polychaete Hediste (Nereis) diversicolor

Considering the ecological importance and potential value of Hediste diversicolor, a better understanding of its metabolic rate and potential growth rates is required. The aims of this study are: (i) to describe key biometric relationships; (ii) to test the effects of temperature and body size on standard metabolic rate (as measure by oxygen consumption) to determine critical parameters, namely Arrhenius temperature (TA), allometric coefficient (b) and reaction rate; and (iii) to determine the metabolic scope for activity (MSA) of H. diversicolor for further comparison with published specific growth rates. Individuals were collected in a Mediterranean lagoon (France). After 10 days of acclimatization, 7 days at a fixed temperature and 24 h of fasting, resting oxygen consumption rates (VO2) were individually measured in the dark at four different temperatures (11, 17, 22 and 27 °C) in worms weighing from 4 to 94 mgDW (n = 27 per temperature). Results showed that DW and L3 were the most accurate measurements of weight and length, respectively, among all the metrics tested. Conversion of WW (mg), DW (mg) and L3 (mm) were quantified with the following equations: DW = 0.15 × WW, L3 = 0.025 × TL(mm) + 1.44 and DW = 0.8 × L33.68. Using an equation based on temperature and allometric effects, the allometric coefficient (b) was estimated at 0.8 for DW and at 2.83 for L3. The reaction rate (VO2) equaled to 12.33 µmol gDW−1 h−1 and 0.05 µmol mm L3−1 h−1 at the reference temperature (20 °C, 293.15 K). Arrhenius temperature (TA) was 5,707 and 5,664 K (for DW and L3, respectively). Metabolic scope for activity ranged from 120.1 to 627.6 J gDW−1 d−1. Predicted maximum growth rate increased with temperature, with expected values of 7–10% in the range of 15–20 °C. MSA was then used to evaluate specific growth rates (SGR) in several experiments. This paper may be used as a reference and could have interesting applications in the fields of aquaculture, ecology and biogeochemical processes

Attraction and repulsion of mobile wild organisms to finfish and shellfish aquaculture: a review

Knowledge of aquaculture–environment interactions is essential for the development of a sustainable aquaculture industry and efficient marine spatial planning. The effects of fish and shellfish farming on sessile wild populations, particularly infauna, have been studied intensively. Mobile fauna, including crustaceans, fish, birds and marine mammals, also interact with aquaculture operations, but the interactions are more complex and these animals may be attracted to (attraction) or show an aversion to (repulsion) farm operations with various degrees of effects. This review outlines the main mechanisms and effects of attraction and repulsion of wild animals to/from marine finfish cage and bivalve aquaculture, with a focus on effects on fisheries-related species. Effects considered in this review include those related to the provision of physical structure (farm infrastructure acting as fish aggregating devices (FADs) or artificial reefs (ARs), the provision of food (e.g. farmed animals, waste feed and faeces, fouling organisms associated with farm structures) and some farm activities (e.g. boating, cleaning). The reviews show that the distribution of mobile organisms associated with farming structures varies over various spatial (vertical and horizontal) and temporal scales (season, feeding time, day/night period). Attraction/repulsion mechanisms have a variety of direct and indirect effects on wild organisms at the level of individuals and populations and may have implication for the management of fisheries species and the ecosystem in the context of marine spatial planning. This review revealed considerable uncertainties regarding the long-term and ecosystem-wide consequences of these interactions. The use of modelling may help better understand consequences, but long-term studies are necessary to better elucidate effects

Influence de la mytiliculture (Mytilus edulis L.) sur les caractéristiques physico-chimiques du sédiment et sur les communautés macrobenthiques

RÉSUMÉ : La biodéposition des bivalves, en augmentant les taux de sédimentation, peut modifier les caractéristiques physico-chimiques du sédiment et affecter les communautés benthiques sous les sites mytilicoles. Les objectifs de cette thèse étaient: (1) de caractériser la production, la sédimentation et la dispersion des biodépâts de moules (Mytilus edulis, L.), (2) d'évaluer les effets de ces biodépâts sur l'environnement benthique, (3) d'évaluer l'efficacité de différents indices utilisés pour détecter les effets de la mytiliculture et (4) de déterminer quelle densité de moules induit des changements dans une communauté benthique et dans les flux biogéochimiques. Les différentes études ont été menées aux Îlesde- la-Madeleine (Québec) pendant les étés 2003 et 2004. Des observations in situ et des analyses expérimentales ont permis de tester différentes hypothèses. Les variations spatiales à petite (10 m - sous et entre filières), moyenne (100 m - sites) et grande échelle (1 km, culture et site référence) ont été prises en compte, ainsi que les variations liées aux différences de taux de biodéposition par les cohortes de bivalves présentes dans la culture (0+ et 1+). L'étude sur la dynamique de biodéposition (Chapitre 2) a montré que le taux de production de biodépâts de moules 1+ était 1,6 fois plus élevé que celui des moules 0+. La vitesse de sédimentation des fèces variait selon la taille des moules. Compte tenu de la vitesse de sédimentation, de la hauteur des filières et de la vitesse moyenne du courant pendant l'été, la dispersion initiale des biodépâts a été estimée entre 0 et 7,4 m dans la zone des moules 1+ et entre 7 et 24,4 m dans la zone des moules 0+. Des mesures in situ ont montré que les taux de sédimentation étaient plus élevés sur les sites mytilicoles que sur les sites références, supportant l'hypothèse que la mytiliculture augmente les taux de sédimentation. Les taux étaient deux fois plus élevés directement sous les filières de moules 1+ qu'entre les filières, 10 m plus loin. L'évaluation des taux de sédimentation le long de transects autour de la zone de mytiliculture a confirmé la faible dispersion initiale des biodépâts dans la lagune de Grande-Entrée. Les caractéristiques physico-chimiques et biologiques du benthos ont été évaluées (Chapitre 3) aux mêmes échelles spatiales que celles utilisées pour évaluer les taux de sédimentation. Parmi les mesures chimiques, le potentiel redox diminuait et la concentration en sulphide augmentait avec la profondeur du sédiment mais aucune différence significative n'a été observée entre les zones (0+, 1 + et référence) et les positions (sous et entre). Par contre, des différences significatives de structure de communautés macrobenthiques ont été observées entre les zones et les positions (1 + sous et 1 + entre). La communauté était dominée par des espèces opportunistes (Capitella capitata) et présentait une faible diversité et une faible biomasse. La comparaison à des données historiques indique que la lagune est un environnement naturellement enrichi. La culture de moules n'a donc, probablement, qu'un effet très localisé sous les filières de moules. Différents indices ont été évalués pour détecter l'effet de la mytiliculture sur l'environnement (Chapitre 4). Les caractéristiques du sédiment (taille de particules, image du profil sédimentaire-SPI, pourcentage de matière organique) et des communautés benthiques (abondance, diversité, biomasse, masse individuelle, groupe trophique, structure de communauté, indice biotique) ont été déterminées dans deux sites mytilicoles: Grande- Entrée (GE) et à Havre-aux-Maisons (HAM) aux Îles-de-Ia-Madeleine. Les stations d' échantillonnage étaient positionnées directement sous la filière la plus externe, à 3, 6, 9, 15, 30 m et sur un site contrôle (300-500 m) le long d'un transect partant des deux sites mytilicoles, dans la direction du courant dominant. L'étude a montré que le choix a priori des stations d'échantillonnage et des indices avait une grande influence sur l' interprétation. L'analyse de la structure de communautés et l'analyse du profil sédimentaire ont permis la détection des effets à la fois proches et éloignés de la mytiliculture, contrairement aux autres indices. Une expérience a été menée in situ pour déterminer quelle quantité de biodéposition pouvait modifier la structure d'une communauté benthique de sable et les flux biogéochimiques (Chapitre 5). Ces derniers (consommation d'oxygène, flux d'ammonium et de phosphate), à l'exception des flux de silicates, n'étaient pas corrélés à la densité de moules. L'abondance totale et le nombre d'espèces ont diminué en fonction de l'augmentation de la densité de moules, tandis que l'abondance et la biomasse de l'espèce opportuniste Capitella sp. ont augmenté dans les benthocosmes soumis à la plus forte densité de moules (764 moules m-2 ). À cette densité, l'environnement est passé d'un état «peu perturbé» à un état «modérément perturbé». Les résultats de cette thèse contribuent à déterminer la capacité d'assimilation de l'environnement benthique pour la mytiliculture. ABSTRACT : Bivalve biodeposition may increase natural sedimentation rates, which could induce changes in the physico-chernical characteristics of the sediment and affect the benthic communities under culture sites. The objectives of the thesis were: (1) to characterise the production, sedimentation and dispersion of mussel (Mytilus edulis L.) biodeposits, (2) to evaluate the effects of biodeposits on the benthic environment, (3) to evaluate the efficiency of different indices to detect mus sel farm influences and (4) to deterrnine which mus sel density induce changes in the benthic community structure and biogeochernical fluxes. The different studies were done during the summer 2003 and 2004 in the Magdalen Islands, Quebec. Observational and experimental approaches were combined to test the different hypotheses. The small (l0 m - un der vs. between mus sel lines), intermediate (100 m - sites) and large (l km, culture vs. reference sites) spatial scale variations were considered, as weIl as the effects of different mussel cohorts (juveniles 0+ and commercial size 1 +). The first study (Chapter 2) has shown that the biodeposit production rates of 1 + mus sel was 1.6 times higher than these of 0+ mussels. The settling velocity of faeces varied in function of mus sel size. Based on the settling velocity of fecal pellet, the height of the mussel lines and the average CUITent velocity, the initial biodeposit dispersion was estimated between 0 and 7.4 m in the 1 + mussel zone and between 7 and 24.4 m in the 0+ mus sel zone. Measurements of sedimentation rates in situ have shown that sedimentation rates was greater at mussel site than at reference site, supporting the hypothesis that mussel culture increase the sedimentation rates. Sedimentation rates were twice greater directly under the 1 + mus sel lines than between the lines, only 10 m distant. The evaluation of sedimentation patterns along transects leading away from the mus sel farm confirmed the low initial biodeposit dispersion in Great-Entry lagoon. The chemical and biological characteristics of the sediment were then evaluated (Chapter 3) using the same spatial sampling design as outlined above. With regards to chemical parameters, redox potentials decreased and sulphide concentrations increased with sediment depth but did not differ among zones or positions. In contrast, a c1ear difference in macrofaunal community structure was observed between zones (0+, 1+ and reference) and position (l +under and 1 +between). The benthic community at 1 +under positions was dorninated by an opportunistic species (Capitella capitata) and had the lowest diversity and biomass. The mus sel farm contributed, therefore, to local organic enrichment. However, the farm effect was restricted to directly under the mussellines as a comparison with historical data indicated that this area of the lagoon is a naturally enriched environment. A further study (Chapter 4) compared different indicators for their ability to detect the influence of bivalve farrning on the environment. Both sediment [partic1e size, sediment profile imaging (SPI), % OM] and benthic community characteristics (abundance, diversity, biomass, individu al body mass, trophic group, corn munit y structure, and biotic index) were evaluated at two mus sel farms: Great-Entry- GE and Havre-aux-Maisons - HAM, in the Magdalen Islands (Quebec). Sampling stations were positioned directly beneath the outside-most mus sel lines (Om) and at distances of 3, 6, 9, 15, 30 m and at a control site (300-500 m) along a transect from the two mussel farms in the main water current direction. Results show very site-specifie effects at the two farms studied. The study showed that the a priori choice of the sampling station and indicators may have a great influence on the interpretation. Community structure and SPI appears to detect small and broader scale influence than other indices. A manipulative ex periment (Chapter 5) was finally carried out in situ to deterrnine the level of mussel biodeposition that modifies sandy benthic community structure and biogeochemical fluxes. Because of high intra-treatment variability, oxygen consumption, ammonium and phosphate fluxes did not vary significantly between treatments. Only silicate was positively correlated to mussel density. A decrease of macrofaunal total abundance and number of species in relation to increased mussel density was observed. An important increase in abundance and biomass of opportunistic species (Capitella sp.) was observed at a mussel density of 764 mussels m-2 . At this density, a shift from slightly to moderately disturbed benthic environment occurred. Results from this thesis contribute to deterrnine the assimilative capacity of the benthic environment for mussel aquaculture

Farm‐scale models in fish aquaculture – An overview of methods and applications

Models are important tools to address sustainability challenges associated with developing aquaculture at farm, regional and global scales. Farm-scale models (FSMs), which are integrated mathematical models developed to simulate farm operations, can quantify energy, mass or economic input flows and predict a variety of outputs such as fish biomass, waste and by-products. The variety of farming systems, equations available to build the models, and objectives of applications and intended users has resulted in the publication of wide range of FSMs. We performed a narrative review of 36 fish FSMs published from 1985–2021 to address several questions: Can the main characteristics of these models be defined? How do the farming system studied and the objectives of the study influence model development? What are the main modelling techniques available to simulate the main processes of a fish farm, and what are their advantages and disadvantages? How can FSMs help address sustainability challenges of aquaculture? This review discusses advances, limitations and future lines of research related to FSMs to help select existing models, or develop new ones, that are suitable for their intended use and users. The article is structured according to the main steps of the modelling process: (i) definition of scope and objectives; (ii) process formulation and model selection at individual, cohort and farm levels; (iii) implementation and evaluation; and (iv) applications (e.g. precision fish farming, IMTA modelling, supporting spatial management, life cycle assessment). At each step, recommendations are provided and research needs are stated

Blue mussel (Mytilus edulis) bouchot culture in Mont-St Michel Bay: potential mitigation effects on climate change and eutrophication

International audienceBivalve production is an important aquaculture activity worldwide, but few environmental assessments have focused on it. In particular, bivalves' ability to extract nutrients from the environment by intensely filtering water and producing a shell must be considered in the environmental assessment. LCA of blue mussel bouchot culture (grown out on wood pilings) in Mont Saint-Michel Bay (France) was performed to identify its impact hotspots. The chemical composition of mussel flesh and shell was analyzed to accurately identify potential positive effects on eutrophication and climate change. The fate of mussel shells after consumption was also considered. Its potential as a carbon-sink is influenced by assumptions made about the carbon sequestration in wooden bouchots and in the mussel shell. The fate of the shells which depends on management of discarded mussels and household waste plays also an important role. Its carbon-sink potential barely compensates the climate change impact induced by the use of fuel used for on-site transportation. The export of N and P in mussel flesh slightly decreases potential eutrophication. Environmental impacts of blue mussel culture are determined by the location of production and mussel yields, which are influenced by marine currents and the distance to on-shore technical base. Bouchot mussel culture has low environmental impacts compared to livestock systems, but the overall environmental performances depend on farming practices and the amount of fuel used. Changes to the surrounding ecosystem induced by high mussel density must be considered in future LCA studies

Effect of dietary water content on European sea bass (Dicentrarchus labrax) growth and disease resistance

The effect of dietary water content on Dicentrarchus labrax growth parameters and resistance to Vibrio anguillarum infection was investigated using commercial pellets with identical energy contents and different moisture levels. The first experiment hypothesis was that moisturizing pelleted ration can have an impact on Dicentrarchus labrax growth performance by the osmoregulation energy cost reduction. In a second time, the experiment explores the effect of water addition in pellets on the fish resistance to a disease. A specific device was built to uniformly moisturize dry pellets to different moisture levels, i.e. 8%, 20%, 40% and 60%. After an acclimation period and a 54-day rearing period, the control fish had grown from 72.7 +/- 17.9 g to 133.3 +/- 29.4 g. No significant differences were recorded for fish growth parameters. After the growth period, the tagged fish were mixed and challenged by bath exposure to live Vibrio anguillarum in triplicate. After 7 days, mortality was significantly lower in the group of fish fed with pellets containing 60% water. Adding water to Dicentrarchus labrax feed did not affect fish growth parameters but increase its resistance to a Vibrio anguillarum infection. The moisturizing process could be used to add specific compounds (such as probiotics or vitamins) to pellets just before fish feeding and could have a positive effect on fish rearing