While aquaculture is increasing worldwide, there are concerns on the east coast of Canada about the influence of finfish aquaculture sites on crustacean distribution patterns. This study evaluated the abundance and movement of American lobsters Homarus americanus and rock crabs Cancer irroratus in the vicinity of 2 salmonid aquaculture leases in Liverpool Bay and Port Mouton, Nova Scotia. The study was done over a full 3 yr production cycle in Liverpool Bay. In Port Mouton, the study was done over 4 mo in 2019, 4 yr after salmonid production had ceased. Each year, around 50 lobsters and 50 crabs were tagged with acoustic transmitters and released at an existing fish farm or at 1 of 2 reference sites. Tagged lobsters travelled throughout Liverpool Bay and showed little affinity to the farm, as most lobsters caught and released adjacent to or below the farm did not stay in the area over time, and their home ranges did not exhibit much overlap with the farm. Very similar patterns were observed for lobsters released in the reference areas and in Port Mouton sites. In contrast, rock crabs moved more slowly than lobsters and seemed to be associated with the farm in Liverpool Bay, as their home ranges had a high overlap with the farm for crabs tagged directly under it. Overall, both rock crab and lobster associated with the Liverpool Bay aquaculture site, although the degree of association varied by species with rock crabs being much more attracted to the area under the farm.

Gargan et al. (2016; Aquacult Environ Interact 8:675-689) used a time series of 15 life history descriptors to demonstrate that the population dynamics of a wild sea trout population could change markedly over a short time period. O’Farrell (2025; Aquacult Environ Interact 17:21-26) subsequently noted certain errors in the data used in Gargan et al. (2016) and presented a new analysis, inferring that the overall findings of Gargan et al. (2016) might be compromised. Here, we provide comprehensive responses to each of the data issues raised by O’Farrell (2025) and include a brief additional analysis. We conclude that the results and interpretation of Gargan et al. (2016) remain supported.

Fish in the South American genus Arapaima Müller, 1843 (hereafter referred to as arapaimas) have attracted interest for commercial aquaculture development thanks to their rapid growth rate and high market value. However, management agencies in the United States have expressed concerns about importing and culturing arapaimas due to records of non-native establishment in certain other countries where arapaimas were released or escaped from captivity. We used the Freshwater Fish Injurious Species Risk Assessment Model (FISRAM) to estimate the probability that arapaimas would be injurious (able to cause harm) to native ecosystems, humans, or the economy of the contiguous United States. Risk assessment model inputs were elicited from arapaima experts around the world. Model results were sensitive to the estimation of climate suitability for arapaimas within the contiguous United States, with predicted probability of injuriousness ranging from 0.784 down to 0.321 with different climate suitability inputs. Expert assessors predicted that competition and predation on native species would be the most likely mechanism of impact and expressed a high degree of uncertainty about potential for impacts from pathogens and parasites. We concluded that due to the cold sensitivity of these tropically adapted fish, establishment within the contiguous United States would be highly restricted geographically, limiting potential impacts if introduced outside climatically suitable areas. Existing regulations already mitigate risk of escape from aquaculture in areas where establishment is plausible, but further research into arapaima parasites and pathogens would help reduce uncertainties and suggest opportunities to enhance biosecurity measures if needed.

The global aquaculture industry has grown substantially, with consequences for coastal ecology and biogeochemistry. Oyster aquaculture can alter the availability of resources for microbes that live in sediments as oysters move large quantities of organic material to the sediments via filter-feeding, possibly leading to changes in the structure and function of sediment microbial communities. Further, oysters can initiate changes in sediment elemental concentrations, several of which are important mediators of microbial metabolism. Here, we use a chronosequence approach to investigate the impacts of oyster farming on sediment microbial communities over 7 yr of aquaculture activity in a temperate coastal system. We detected shifts in bacterial composition (16S rRNA gene amplicon sequencing), changes in gene expression (meta-transcriptomics), and variations in sediment elemental concentrations (sediment geochemistry) across different durations of oyster farming. Our results indicate that both the structure and function of bacterial communities vary between control (no oysters) and farm sites, with an overall increase in diversity and a shift towards anoxic tolerance in farm sites. However, little to no variation was observed in either structure or function with respect to farming duration, suggesting these sediment microbial communities are resilient to change. We also did not find any significant impact of farming on heavy metal accumulation in the sediments. The minimal influence of long-term oyster farming on sediment bacterial function and biogeochemical processes observed here provides important insights for establishing best practices for sustainable farming in these areas.

Whilst aquaculture continues its global expansion, containment of fish in sea cages remains a persistent environmental challenge. Within Atlantic salmon Salmo salar farming, widespread escapes over several decades have left a legacy of ecological and genetic impacts on wild populations. Quantifying the characteristics of escapees, and how they vary in time and space, is important to understand how environmental impacts will vary and how mitigation strategies need to be tuned. Using a fish trap located in the River Etne on the west coast of Norway, we created an ecological and genetic profile for 616 escapees entering the river. The most important findings of the present study were (1) the annual number of escapees entering the trap declined in the period 2014-2018; (2) more than half of the escapees entering the river were mature; (3) the vast majority of escapees entering the river were categorised as recent escapees; (4) nearly all (96%) of the early escapees were mature upon entry to the river, while just over half (55%) of the recent escapees were mature; and (5) the escapees originated from multiple sources every year. We conclude that without the fish trap, this population would have been at risk of exposure to further spawning and introgression of domesticated salmon. Furthermore, the current findings of maturation status and escape history highlight the fact that mitigation efforts to reduce escape of smolts, post-smolts and larger fish all need continued attention from the management authorities and aquaculture industry.

We analyzed growth performance and waste emissions of cage aquaculture responding to biophysical conditions that vary along the coastline of Norway. The analysis is based on a published mass balance model predicting waste emissions and open quality-assured data from the Norwegian Directorate of Fisheries between 2016 and 2020. Results showed significant regional variation in feed conversion rate, with a steady increase from the Northern to Southern region (p < 0.001) and a co-occurring reduction in waste emission. The retention rate of feed carbon (C), nitrogen (N) and phosphorus (P) in tissues of farmed Atlantic salmon Salmo salar Linnaeus, 1758 varied from 39 to 43% of consumed nutrients across regions. The estimated defecation rate of C, N and P was 18% of consumption, whereas excretion or respiration varied from 39 to 43% across regions. This variability, along with farming methods and location characteristics, could potentially impact regional differences in benthic ecosystems. The regional differences in feed and environmental cost could potentially attract salmon farming to shift towards the Northern region, and this trend might become strengthened as water temperatures rise due to climate change. Additionally, salmon growth and feed intake rate interacted significantly with temperature (p < 0.001) and showed regular seasonal variation. The regulation of maximum allowed biomass restricts salmon farmers from increasing biomass beyond their maximum allowed level at any time. Nevertheless, the same biomass may cause higher waste in the summer. Therefore, we suggest an awareness of the seasonal increase in waste emissions and consideration of implementing environmental assessment for surface waters, which might be beneficial for decreasing the risk of reduced water quality.

Aquaculture industries have the capacity to produce positive ecosystem service benefits, such as the provision of habitat to wild animals. Oyster cultivation is the oldest and largest aquaculture industry in south-eastern Australia. Oyster spat are grown to marketable size in rack-and-rail (‘racks’) or longline-and-basket (‘baskets’) configurations, which add structure to estuarine waters. This study assessed: (1) how the fish communities associated with oyster farms vary with production method; (2) how communities of fish utilise oyster infrastructure, as compared to adjacent natural habitats; and (3) whether oyster infrastructure can serve as de facto oyster reefs by supporting similar fish communities. Remote underwater video surveys, conducted during summer and winter of 2 study years, revealed that fish observations and species richness were generally greater for rack than basket cultivation. Both types of oyster farms supported at least as many species of fish as adjacent natural habitats, including oyster reef, seagrass, mangrove and bare sediment. Fish communities were, in general, most similar between racks and baskets and most dissimilar between racks and bare sediments. Oyster farms supported species of fish otherwise limited to habitats with wild oysters, and unique harvested fish species were observed more frequently at racks. Fish use of oyster-growing infrastructure for foraging and shelter mirrored use of natural biogenic habitats. Overall, this study suggests that the oyster aquaculture infrastructure can support fish communities with species composition similar to those of natural biogenic habitats, although this service is dependent on farming method. Ecosystem services provided by aquaculture should be considered in estuarine habitat enhancement, conservation and restoration.

Cold-water corals (CWCs) have come under increasing pressure from human activities over the last decades. Of particular concern in Norway is the potential impact of open net pen aquaculture on CWC reefs formed by Lophelia pertusa, a threatened and declining habitat. We conducted a 1 yr in situ transplantation experiment and corresponding field measurements of 2 reefs located close to fish farms to elucidate the impacts of particulate organic waste released from the farms on coral colonies. Our study provided new evidence of negative impacts of organic effluents on L. pertusa ecophysiology. After 1 yr, both naturally occurring and transplanted corals, at distances ranging from 250 m to 1 km downstream of what would be regarded as an average-sized Norwegian fish farm, exhibited depressed metabolic rates compared to corals outside the main depositional footprint of the farms. The metabolic depression impeded energy acquisition, reducing growth and energy reserves by up to 70 and 50%, respectively. No clear threshold for significant biological impact could be detected along a distance gradient. Instead, a gradual decrease in metabolic rates, growth and lipid reserves occurred with increasing modelled sedimentation rate of organic waste from the farm. The strong statistical correlation between oxygen consumption, growth, energy stores and sedimentation rates implies that predictions of the short-term impact of aquaculture effluents on L. pertusa ecophysiology and CWC reef development may be achievable in the future. This would significantly improve the ability of management to make informed decisions on the licensing of new farms near CWC reefs.