ALBERT

Description: Antibiotics have been commonly used as antimicrobial agents in the process of aquaculture worldwide. However, very few studies are available on the endocrine disruption-related health risks brought about by antibiotic residues from human consumption of aquatic products. Nuclear hormone receptors (NHRs) could mediate many endocrine-disrupting activities. Therefore, in the present study, a reverse docking method was used to predict the direct binding interactions between 16 NHR conformations and 15 common antibiotics in aquaculture, thereby determining their potential endocrine-disrupting risks. To reach a compromise between the extremely scarce experimental data and an urgent need for distinguishing antibiotics of high concern with potential food-borne endocrine-disrupting risks in aquaculture, a risk-ranking system was then developed based on a comprehensive risk score for each category of antibiotics, which was the sum of the products of endocrine-disrupting potential coefficients and annual usages of antibiotics in aquaculture. The results indicated that 15% of 224 docking simulations showed a relatively high probability of binding. Sulfonamides seemed to possess the greatest endocrine-disrupting potential. The antagonistic conformation of the androgen receptor was the most susceptible NHR conformation. The rank orders of the endocrine-disrupting risk of different categories of antibiotics varied greatly from country to country, which were significantly affected by the annual usage. These findings pose questions regarding public health and safety associated with human consumption of antibiotic-containing aquatic products. In addition, we provide an approach to rank antibiotics for a specific country or region, with respect to their potential endocrine-disrupting activity, that can be used to inform regulation and prioritize experimental verification.

Description: Salmon lice Lepeophtheirus salmonis from aquaculture can cause negative impacts on sea trout Salmo trutta and other wild salmonids. Long-term records from 5 Irish rivers were used to explore relationships between annual sea trout runs and estimated total number of lice on nearby salmon farms. It was hypothesised that local environmental conditions may result in system-specific differences in realised louse pressure on sea trout. Louse count was thus tested as an absolute number and as a relative pressure, i.e. standardised by farm. When the standardised total number of mobile lice on a given salmon farm in April was above baseline level (50th percentile of observed annual values on that farm), there was a high probability of a below-average sea trout run in the local river. Absolute louse counts did not show an important effect on runs. This finding suggests that salmon farm louse production in spring can have a strong system-specific regulating effect on wild sea trout populations. Total number of lice on a farm was most strongly driven by changes in individual infestation rate, with a lesser effect of stocking density. Thresholds for number of mobile lice per farmed salmon required to maintain total louse count below the baseline varied with stocking density and among systems: greater density required lower infestation rate. Regulations relying on a generic louse threshold to trigger treatment are not sufficient to protect sea trout populations—stocking density and site characteristics must be considered to evaluate system-specific infestation pressure and impacts on wild salmonids.

Description: Salmon lice Lepeophtheirus salmonis pose a major threat to the sustainable development of salmonid farming. To investigate effects of farm-origin salmon lice on wild salmonids, salmon lice dynamics are typically simulated using models that depend on experimentally determined rates of development, reproduction, mortality and infestation. Several recent studies provide new estimates of how these demographic rates depend on temperature and salinity. Here, we review and synthesize these studies and test if updating a salmon lice infestation model based on the new insights improves predictions of salmon lice infestations on salmon post-smolts in experimental cages in the sea. This model predicts spatiotemporal variation in infestation pressure based on weekly monitoring data of salmon lice and sea temperature in all salmonid fish farms in Norway, here supplemented by temperature and salinity data from a regional ocean model. Using data from 2012-2017 to select model formulation, we found the largest improvement in explanatory power by incorporating a salinity-dependent infestation rate. Updating functions for temperature-dependent egg production and infestation rates led to smaller improvements. Moreover, results suggest additional effects of temperature and a possible temperature-salinity interaction effect, not captured by the modelled processes. Out-of-sample predictions for experimental cage data from 2018-2020 confirmed that the uncertainty was realistically quantified, but also showed that associations of salmon lice infestations with salinity and temperature had changed. These results provide a field evaluation of experimental data and point to a knowledge gap regarding the combined effects of temperature and salinity on salmon lice infestations.

Description: Freshwater pond polyculture faces many challenges in Europe. Appropriate tools must be developed to better understand and manage trophic interactions in pond ecosystems. The objective of our study was to understand the trophic interactions and make inference on the fish diet in common carp polyculture through a combination of experiments and trophic web modeling. We conducted an experiment in small fishponds of common carp polyculture reared with roach and perch and used Ecopath with Ecosim software to characterize the food web. Two replicates of 3 treatments were performed: a semi-extensive pond with low fish density and no formulated feed, an intensive pond with twice the fish density and formulated feed and an intensive pond coupled with a planted lagoon. Ten trophic groups were defined to describe the food web. The modeling procedure enabled us to estimate the diets of each trophic group. The fish diet in fed and non-fed treatments differed greatly since the carp fed mainly on formulated feed when available. The roach exhibited trophic plasticity by adapting their diet to the available resources. The benthic macroinvertebrates and zooplankton were preyed upon intensively; they became the limiting factors for fish production and depended on phytoplankton availability. Detritus and phytoplankton were the main sources of nutrients in all treatments but were not used efficiently. These results provide several insights for improving polyculture. In particular, they promote better management of zooplankton and macroinvertebrates as food sources for target species and a better balance in fish assemblages for more efficient use of resources.

Description: Sea cucumber aquaculture is increasing in extent and importance throughout the Indo-Pacific region, supplying a luxury seafood market in Asia. In this context, the grow-out of hatchery-bred juveniles in community-farmed pens is proving to be a viable model, providing increased income security and alternative livelihood options to resource-limited communities. Here, we report a study of the impacts of such sea cucumber farming on the growth of seagrass (a favourable habitat for the animals) at a village-scale aquaculture site in southwest Madagascar. Using experiments, we found that the presence of the hatchery-bred sea cucumber Holothuria scabra (sandfish), at stocking densities of 300 g m-2 (similar to the density used in the farmed pens, but relatively high for natural populations), resulted in a large (~30%), statistically significant increase in the leaf extension rate of the locally dominant seagrass species Thalassia hemprichii. However, the other dominant seagrass species, Cymodocea serrulata, did not significantly change its leaf extension rate in the presence of H. scabra. Since seagrass is a globally important coastal habitat, supporting high biodiversity, carbon sequestration, shoreline stability and nursery grounds for commercial and small-scale fisheries, the positive effect of H. scabra farming on the growth rate of at least one dominant seagrass species implies potential important ecological co-benefits. These co-benefits of H. scabra farming are likely to be relevant across the tropical Indo-Pacific coastlines, where this species is cultured.

Description: Multi-tiered oyster aquaculture cages may provide habitat for fish assemblages similar to natural structured seafloor. Methods were developed to assess fish assemblages associated with aquaculture gear and boulder habitat using underwater video census combined with environmental DNA (eDNA) metabarcoding. Action cameras were mounted on 3 aquaculture cages at a commercial eastern oyster Crassostrea virginica farm (‘cage’) and among 3 boulders on a natural rock reef (‘boulder’) from June to August 2017 in Long Island Sound, USA. Interval and continuous video recording strategies were tested. During interval recording, cameras collected 8 min video segments hourly from 07:00 to 19:00 h on cages only. Continuous video was also collected for 2-3 h on oyster cages and boulders. Data loggers recorded light intensity and current speed. Seawater was collected for eDNA metabarcoding on the reef and farm. MaxN measurements of fish abundance were calculated in video, and 7 fish species were observed. Black sea bass Centropristis striata, cunner Tautogolabrus adspersus, scup Stenotomus chrysops, and tautog Tautoga onitis were the most abundant species observed in both oyster cage and boulder videos. In continuous video, black sea bass, scup, and tautog were observed more frequently and at higher abundance on the cage farm, while cunner were observed more frequently and at higher abundance on boulders within the rock reef. eDNA metabarcoding detected 42 fish species at the farm and reef. Six species were detected using both methods. Applied in tandem, video recording and eDNA provided a comprehensive approach for describing fish assemblages in difficult to sample structured oyster aquaculture and boulder habitats.

Description: Shellfish growers routinely observe fish and invertebrates interacting with their aquaculture gear. To quantitatively assess these interactions, underwater action cameras (GoPro®) were used to document fish and invertebrate activity in and around floating oyster bags, cages, and a natural marsh habitat on an oyster farm in the Little Egg Harbor region of Barnegat Bay, New Jersey, USA, in 2018. A free and open-source event-logging software was used to analyze video files. A total of 21 species from 4 phyla were identified across all days and sites. Nekton were quantified from continuously recorded video using the MaxN abundance metric, defined as the maximum number of individuals of a given species present within each 1 min segment of video. Species of both ecological and economic importance in the local ecosystem used the 3 intertidal habitats. Abundance and community composition observed around oyster cages differed from that around floating oyster bags and marsh edge; the latter 2 habitats were not significantly different. Juvenile fish were frequently observed, suggesting that the oyster farm may provide similar natural history functions as other natural marsh habitat.