Biologists have long recognized environmental disturbances impact both the growth of renewable resources and the efficiency of harvest effort. However, models of renewable resource management under uncertainty have commonly assumed economic and biological uncertainties to be uncorrelated. We present examples of valuable fish species that experience correlated variation in biological growth and catchability, in response to a common environmental disturbance. Building correlation into a model of renewable resource management under uncertainty, we find correlation to alter the optimal response by managers to cost disturbances, and impact the value of retaining intra-period flexibility over harvest targets. Examining the performance of three harvest control mechanisms—harvest quotas, effort quotas, and taxes—reveals that positive correlation between costs and growth favors harvest quotas over effort quotas, and effort quotas over taxes (and vice versa). The model is then applied numerically to the Pacific bigeye tuna fishery, which experiences positively correlated shocks driven by the El Niño Southern Oscillation. Correlation qualitatively changes the optimal response to a cost shock, and harvest quotas are found to be strongly favored over both effort quotas and taxes.
Aquaculture, Seafood, and Food Security
Ocean acidification is a global, long-term problem whose ultimate solution requires carbon dioxide reduction at a scope and scale that will take decades to accomplish successfully. Until that is achieved, feasible and locally relevant adaptation and mitigation measures are needed. To help to prioritize societal responses to ocean acidification, we present a spatially explicit, multidisciplinary vulnerability analysis of coastal human communities in the United States. We focus our analysis on shelled mollusc harvests, which are likely to be harmed by ocean acidification. Our results highlight US regions most vulnerable to ocean acidification (and why), important knowledge and information gaps, and opportunities to adapt through local actions. The research illustrates the benefits of integrating natural and social sciences to identify actions and other opportunities while policy, stakeholders and scientists are still in relatively early stages of developing research plans and responses to ocean acidification.
The concept of co-location of marine areas receives an increased significance in the light of sustainable development in the already heavily used offshore marine realm. Within this study, different spatial co-location scenarios for the coupling of offshore aquacultures and wind farms are evaluated in order to support efficient and sustainable marine spatial management strategies. A Geographic Information System (GIS) and multi-criteria evaluation (MCE) techniques were combined to index suitable co-sites in the German exclusive economic zone of the North Sea. The MCE was based on criteria such as temperature, salinity or oxygen. In total, 13 possible aquaculture candidates (seaweed, bivalves, fish and crustaceans) were selected for the scenario configuration. The GIS modelling framework proved to be powerful in defining potential co-location sites. The aquaculture candidate oarweed (Laminaria digitata) revealed the highest suitability scores at 10–20 m depth from April to June, followed by haddock (Melanogrammus aeglefinus) at 20–30 m depth and dulse (Palmaria palmata) and Sea belt (Saccharina latissima) at 0–10 m depth between April and June. In summary, results showed several wind farms were de facto suitable sites for aquaculture since they exhibited high suitability scores for Integrated Multi-Trophic Aquaculture (IMTA) systems combining fish species, bivalves and seaweeds. The present results illustrate how synergies may be realised between competing needs of both offshore wind energy and offshore IMTA in the German EEZ of the North Sea. This might offer guidance to stakeholders and assist decision-makers in determining the most suitable sites for pilot projects using IMTA techniques.
Juvenile fish of >20 different species use offshore floating sea cages as settlement habitats in the Mediterranean Sea. In the present work, surveys were conducted to identify differences between species composition and abundance of new settlers among farms and control rocky-shore environments and to test for variation in their diets. Along with this, otolith growth and morphology analyses were also applied to better understand the consequences for the ecology and growth performance of several fish species that use coastal farms as recruitment habitats in the southwestern Mediterranean Sea. Results showed that fish farms are acting as a new habitat for the settlement of juvenile fish and that detected abundance could be compared with that found at natural habitats such as shallow rocky environments. However, a consistent pattern for all the studied species was a significant variation in otolith-shape descriptors, principally identified through the Aspect Ratio index, which was lower for the farm-associated species Atherina boyeri, Oblada melanura, and Sarpa salpa. Otolith modifications were effectively detected by elliptic Fourier descriptors since multivariate analysis correctly identified farm or control origin at 78.8, 85.1, and 86.1% for A. boyeri, O. melanura, and S. salpa individuals, respectively. According to these results, fish farms may offer new settlement habitat for several fish species on open coastal areas and provide resources equivalent to rocky habitats, but at the same time causing some effect on fish growth as a potential consequence of the availability of particulate organic matter derived from feed pellets.
Coastal fisheries and sea cage aquaculture coexist along the coastal zone, and it has been suggested that wild fish feed on excess feed around farms. If this occurs, the condition of wild fish can increase and their lipid profile can become modified. However, the influence of fishfarming on coastal fisheries has not been described in detail. Four targeted species of different trophic gilds, Sardinella aurita, Caranx rhonchus, Mullus barbatus, and Pomatomus saltatrix were studied and the lipid profiles of individuals captured by coastal fisheries and around fish farms were compared. Results show that fish captured at farms showed increased levels of total lipids and/or the terrestrial fatty acids contained in feed pellets. Individuals with increased terrestrial fatty acid proportions were detected in the catch of small-scale artisanal fisheries but not among trawled fish. Consequently, this study demonstrates the influence of fishfarming on coastal fisheries through the exportation of excess feed in the shape of wild fish biomass.
Norwegian aquaculture has grown from its pioneering days in the 1970s to be a major industry. It is primarily based on culturing Atlantic salmon and rainbow trout and has the potential to influence the surrounding environment and wild populations. To evaluate these potential hazards, the Institute of Marine Research initiated a risk assessment of Norwegian salmon farming in 2011. This assessment has been repeated annually since. Here, we describe the background, methods and limitations of the risk assessment for the following hazards: genetic introgression of farmed salmon in wild populations, regulatory effects of salmon lice and viral diseases on wild salmonid populations, local and regional impact of nutrients and organic load. The main findings are as follows: (i) 21 of the 34 wild salmon populations investigated indicated moderate-to-high risk for genetic introgression from farmed escaped salmon. (ii) of 109 stations investigated along the Norwegian coast for salmon lice infection, 27 indicated moderate-to-high likelihood of mortality for salmon smolts while 67 stations indicated moderate-to-high mortality of wild sea trout. (iii) Viral disease outbreaks (pancreas disease, infectious pancreatic necrosis, heart and skeletal muscle inflammation, and cardiomyopathy syndrome) in Norwegian salmon farming suggest extensive release of viruses in many areas. However, screening of wild salmonids revealed low to very low prevalence of the causal viruses. (iv) From ∼500 yearly investigations of local organic loading under fish farms, only 2% of them displayed unacceptable conditions in 2013. The risk of eutrophication and organic load beyond the production area of the farm is considered low. Despite several limitations, especially limited monitoring data, this work represents one of the world’s first risk assessment of aquaculture. This has provided the Norwegian government with the basis upon which to take decisions for further development of the Norwegian aquaculture industry.
The salmon louse (Lepeoptheirus salmonis) is a challenge in the farming of Atlantic salmon (Salmo salar). To treat an infestation, different insecticides are used like the orally administered chitin synthetase inhibitor teflubenzuron. The concentrations and distribution of teflubenzuron were measured in water, organic particles, marine sediment and biota caught in the vicinity of a fish farm following a standard medication. Low concentrations were found in water samples whereas the organic waste from the farm, collected by sediment traps had concentrations higher than the medicated feed. Most of the organic waste was distributed to the bottom close to the farm but organic particles containing teflubenzuron were collected 1100 m from the farm. The sediment under the farm consisted of 5 to 10% organic material and therefore the concentration of teflubenzuron was much lower than in the organic waste. Teflubenzuron was persistent in the sediment with a stipulated halflife of 170 days. Sediment consuming polychaetes had high but decreasing concentrations of teflubenzuron throughout the experimental period, reflecting the decrease of teflubenzuron in the sediment. During medication most wild fauna contained teflubenzuron residues and where polychaetes and saith had highest concentrations. Eight months later only polychaetes and some crustaceans contained drug residues. What dosages that induce mortality in various crustaceans following short or long-term exposure is not known but the results indicate that the concentrations in defined individuals of king crab, shrimp, squat lobster and Norway lobster were high enough shortly after medication to induce mortality if moulting was imminent. Considering food safety, saith and the brown meat of crustaceans contained at first sampling concentrations of teflubenzuron higher than the MRL-value set for Atlantic salmon. The concentrations were, however, moderate and the amount of saith fillet or brown meat of crustaceans to be consumed in order to exceed ADI is relatively large.
The tropical spiny lobster, Panulirus ornatus, is farmed in floating sea cages situated in shallow coastal waters in many parts of the Asia-Pacific region. Despite the rapid expansion of this aquaculture activity, very little is known about its environmental impacts. This study combines computer modelling with previous laboratory measures to provide information on benthic carbon deposition and the production of dissolved inorganic nitrogen (DIN) from hypothetical sea cage aquaculture of spiny lobsters. Modelling scenarios were run with two different lobster aquaculture stocking densities (3 and 5 kg m−3) and various feed conversion ratios (FCRs) using natural seafood or artificial lobster diet (FCR 1.28–28). Simulations from the model showed that cumulative benthic carbon deposition varied from 0.1 to over 0.8 kg C m−2 year−1, while the mean DIN levels around sea cages ranged from 5.6 up to 25 µg N l−1 and the maximum DIN levels ranged from 10.8 to 165 µg N l−1. The results showed that feeding lobsters with seafood resulted in a markedly higher benthic carbon loading and release of DIN when compared with artificial lobster feed. Therefore, the elimination of the use of trash fish would greatly reduce the environmental impacts of spiny lobster aquaculture. Overall, the effects from spiny lobster aquaculture were spatially localized with the highest concentrations of carbon deposition and DIN directly beneath the sea cages. Therefore, it seems unlikely that spiny lobster aquaculture in sea cages will cause adverse environmental effects unless the lobsters are heavily stocked and supplied with poor quality feed.
Sea lice are copepod ectoparasites with vast reproductive potential and affect a wide variety of fish species. The number of parasites causing morbidity is proportional to fish size. Natural low host density restricts massive parasite dispersal. However, expanded salmon farming has shifted the conditions in favor of the parasite. Salmon farms are often situated near wild salmonid migrating routes, with smolts being particularly vulnerable to sea lice infestation. In order to protect both farmed and wild salmonids passing or residing in the proximity of the farms, several measures are taken. Medicinal treatment of farmed fish has been the most predictable and efficacious, leading to extensive use of the available compounds. This has resulted in drug-resistant parasites occurring on farmed and possibly wild salmonids.
This report covers 21 coastal states of interest as identified by The Nature Conservancy: Alabama, California, Connecticut, Delaware, Florida, Georgia, Louisiana, Maine, Maryland, Massachusetts, Mississippi, New Hampshire, New Jersey, New York, North Carolina, Oregon, Rhode Island, South Carolina, Texas, Virginia, and Washington. The team did not review the policies of Alaska, Hawaii, Pennsylvania, and the Great Lakes states.