Assessments of salmon louse impacts on wild salmon populations typically involve quantitative modelling of impacts and sensitivity analysis of potential effects of uncertain model assumptions. A Bayesian network approach allows such quantitative results to be combined with more subjective expert assessments of the belief in these assumptions. Using this approach, we quantified probability distributions for effects of salmon lice on mortality of out-migrating juvenile wild salmon in Norway. These distributions captured uncertainty quantified in the stochastic part of the model and uncertainty associated with 2 model assumptions: the timing of migration and the tolerance of juvenile salmon to salmon lice. Results showed that while the calculated impact was sensitive to the assumptions made about timing and tolerance, the probability distribution was only marginally wider when the uncertainty about timing and tolerance was included. The results support assessments of the uncertainty of salmon louse-induced mortality of wild salmon, an environmental impact indicator used in region-level biomass regulation of Norwegian aquaculture. The findings also have broader implications: when multiple model assumptions are uncertain but equally likely to deviate in opposite directions, their combined effect on overall uncertainty may be smaller than thought a priori , emphasising the importance of quantifying joint uncertainty in complex models.
Pancreas disease (PD) caused by salmonid alphavirus (SAV) is a serious challenge in Atlantic salmon farming. PD outbreaks in salmon farms may spread the virus to the surrounding environment and potentially cause infections in wild salmon. Screening for SAV has revealed very low infection rates in wild salmonids irrespective of fish farming intensity or the frequency of PD outbreaks. However, monitoring of infection and disease in wild fish is difficult and has limitations. Therefore, to investigate any potential population-regulatory effects of the SAV transmission from aquaculture to wild populations, we conducted extensive Atlantic salmon Salmo salar smolt release experiments in 2 rivers in western Norway where PD is endemic in commercial farms. Released fish either received a commercially available PD vaccine or were unvaccinated controls. Returning adults were registered in both rivers in the subsequent years. Date of capture, body length, weight and sex of a subset of returning salmon were recorded. Our results show no significant differences in marine survival, fish growth or return age between the fish originating from the vaccinated and control groups in either river or release year even though numerous PD outbreaks were reported in farms along the migration routes during the study period. These data support results from SAV surveillance conducted earlier, suggesting that wild Atlantic salmon smolts are at low risk of SAV infection from fish farms. Therefore, we conclude that PD outbreaks in salmon farming are unlikely to lead to SAV infection-derived reduced marine growth or increased mortality in migrating wild salmon post-smolts with significance at the population level.
Global production of animal protein from aquaculture systems is increasing in importance; however, increasing intensification of aquaculture farming systems has exposed farmed fish and shellfish to multiple stressors, including environmental variability, nutritional imbalance, and pathogens, which can disrupt the normal physiological homeostasis of animals, suppress their immune response, and lead to reduced productivity. Therefore, the industry is increasingly interested in developing sustainable alternatives to conventional chemotherapy drugs. Therapeutic plant-based products, which can include medicinal herbs, phytogenic feed additives, and botanical extracts, represent a promising ecological alternative to conventional chemotherapy agents. This review provides a comprehensive analysis of the literature regarding the use of herbs for managing stress in aquaculture with an emphasis on their immunomodulatory, antioxidant, growth-promoting, and disease-mitigating properties. In particular, the roles of these botanicals in regulating the physiological processes associated with environment, nutrition, and health of aquatic animals are emphasized. Specific bioactive phytochemicals including flavonoids, alkaloids, terpenoids, and phenolic compounds are examined for their ability to modulate redox-mediated stress pathways, cytokine networks, and metabolic efficiency under conditions of high-intensity aquaculture production. A number of representative botanicals ( Curcuma longa, Zingiber officinale, Allium sativum , and Camellia sinensis ) have demonstrated significant potential in improving the immune response of fish, their feed conversion efficiency, and their resistance to pathogens. Overall, this review demonstrates that phyto-therapeutics offer biodegradable and low-residue options for reducing dependence on antibiotics, while at the same time promoting sustainable food production. We also discuss some of the challenges that need to be addressed before phytotherapy can be translated into practical application in climate-resilient aquaculture systems.
The rapid expansion of the invasive Atlantic blue crab Callinectes sapidus in the northern Adriatic Sea has caused severe ecological and economic disruptions, particularly within the Manila clam Ruditapes philippinarum aquaculture sector in the Po Delta lagoons. In response, fishers and aquaculture cooperatives have spontaneously implemented spatial control measures, including perimeter fencing, predator-exclusion netting, and selective trapping, to mitigate predation and safeguard clam farming areas. This study documents these interventions and analyzes trends in blue crab and clam landings between 2022 and 2024 to provide a more comprehensive picture of recent dynamics. Although clam production remains far below pre-invasion levels, spatial containment and daily trapping have facilitated a partial recovery of clam farming activities. These farmer-led initiatives represent a compelling example of spatial control, whereby invasive crab densities are suppressed below damage thresholds in key productive areas. In addition, efforts to commercialize the blue crab, particularly through new export markets, have helped offset economic losses. These findings provide valuable insights into adaptive, community-driven strategies for managing aquatic invaders. Considering the substantial national government investment to subsidize fishers and support blue crab disposal, the present study demonstrates how bottom-up initiatives can complement, and even anticipate, formal management frameworks.
