Wrasse (Labridae) are used widely as cleaner fish to control sea lice infestation in commercial farming of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) in Norway. As a ...result, there is an intense fishery for wrasse along the Norwegian coast. Little is known of the population ecology of wrasse and, therefore, an evaluation of their distribution, demographics, and habitat preferences was required as a baseline from which to assess the impact of the fishery. We analysed experimental catch data from a 3-year survey carried out in 1997-1999 (before the fishery began) during and after the wrasse spawning season in a Norwegian fjord. Corkwing wrasse (Symphodus melops) was always the most abundant species, ranging from 52 to 68% of the catches. Goldsinny (Ctenolabrus rupestris) and rock cook (Centrolabrus exoletus) were the second most abundant species (up to 30%). Ballan (Labrus bergylta) and cuckoo (Labrus mixtus) wrasse represented <2% of the catches. Rock cook was relatively more abundant at more exposed stations, while corkwing wrasse was characteristic of more sheltered stations. Goldsinny and ballan wrasse both occupied mainly intermediate stations in the more protected areas. Smaller fish were found at the most protected areas, while larger fish were found at the more exposed stations. Sex ratio in goldsinny and rock cook varied significantly from year to year. In corkwing, the sex ratio remained the same each year, and females were always in larger proportion (61-66%). Spawning occurred mainly in June for goldsinny, rock cook, and corkwing wrasse. The fact that species composition and/or size distributions vary considerably over very small distances must be considered in monitoring programmes. Erroneous conclusions about shifts in species composition can easily be made simply because sampling gear are set in slightly different areas.
The movement patterns of three commercially important wrasse (Labridae) species inside a small marine protected area (~ 0.15 km2) on the west coast of Norway were analysed over a period of 21 months. ...The mean distance between capture and recapture locations varied between 10 and 187 m, and was species and season specific. The extent of movement was not related to body size or sex. These results imply that a network of small strategically located marine protected areas can be used as management tools to protect wrasses from size‐ and sex‐selective fishing mortality.
High-voltage direct current (HVDC) subsea cables are used to transport power between locations and from/to nearshore and offshore facilities. HVDC cables produce magnetic fields (B-fields) that could ...impact marine fish. Atlantic haddock (
) is a demersal fish that is at risk of exposure to anthropogenic B-fields. Their larvae drift over the continental shelf, and use the Earth's magnetic field for orientation during dispersal. Therefore, anthropogenic magnetic fields from HVDC cables could alter their behavior. We tested the behavior of 92 haddock larvae using a setup designed to simulate the scenario of larvae drifting past a B-field in the intensity range of that produced by a DC subsea cable. We exposed the larvae to a B-field intensity ranging from 50 to 150 µT in a raceway tank. Exposure to the B-field did not affect the spatial distribution of haddock larvae in the raceway. Larvae were categorized by differences in their exploratory behavior in the raceway. The majority (78%) of larvae were nonexploratory, and exposure to the artificial B-field reduced their median swimming speed by 60% and decreased their median acceleration by 38%. There was no effect on swimming of the smaller proportion (22%) of exploratory larvae. These observations support the conclusion that the swimming performance of nonexploratory haddock larvae would be reduced following exposure to B-field from HVDC cables. The selective impact on nonexploratory individuals, and the lack of impact on exploratory individuals, could have population-scale implications for haddock in the wild.
Disease and parasitism cause major welfare, environmental and economic concerns for global aquaculture. In this review, we examine the status and potential of technologies that exploit genetic ...variation in host resistance to tackle this problem. We argue that there is an urgent need to improve understanding of the genetic mechanisms involved, leading to the development of tools that can be applied to boost host resistance and reduce the disease burden. We draw on two pressing global disease problems as case studies—sea lice infestations in salmonids and white spot syndrome in shrimp. We review how the latest genetic technologies can be capitalised upon to determine the mechanisms underlying inter‐ and intra‐species variation in pathogen/parasite resistance, and how the derived knowledge could be applied to boost disease resistance using selective breeding, gene editing and/or with targeted feed treatments and vaccines. Gene editing brings novel opportunities, but also implementation and dissemination challenges, and necessitates new protocols to integrate the technology into aquaculture breeding programmes. There is also an ongoing need to minimise risks of disease agents evolving to overcome genetic improvements to host resistance, and insights from epidemiological and evolutionary models of pathogen infestation in wild and cultured host populations are explored. Ethical issues around the different approaches for achieving genetic resistance are discussed. Application of genetic technologies and approaches has potential to improve fundamental knowledge of mechanisms affecting genetic resistance and provide effective pathways for implementation that could lead to more resistant aquaculture stocks, transforming global aquaculture.
Several species of wrasse (Labridae) are used as cleaner fish to remove salmon lice from farmed Atlantic salmon. We estimated the fishery and use of wrasse in Hardangerfjord. The estimated numbers of ...labrids used on salmon and rainbow trout farms varied between 86,000 and 251,000 from 2002-2006, but increased to as much as 1.1 million in 2009 and 2010. A total of 93,500 kg (around 1.54 million) labrids were reported landed during 2000-2010. Corkwing wrasse (Symphodus melops) was by far the most important wrasse species: 52% by weight and 56% by number. Ballan wrasse (Labrus bergylta) made up 34% by weight but only 14% by number (due to its larger size). The relative proportion of species between the different sampling locations in the fjord was significantly different, as was the condition factor of some species. Goldsinny wrasse (Ctenolabrus rupestris) had the slowest growth of the labrids in this study, and did not reach the minimum commercial catch size (11 cm) before they were 4-5 years old. Very few goldsinny caught were over that size. Corkwing reach commercial size in 1-2 years. The results of this study indicate that wrasse should be protected during the spawning season. Species such as goldsinny grow so slowly that they will most likely be collected several times in heavily fished areas but discarded because they are smaller than the minimum allowable size. This could be avoided through the use of modified traps with escape routes for undersized fish. This study represents a first step towards establishing a knowledge-based management plan for the wrasse fishery.
The themed set of articles that follows this introduction contains a selection of the papers that were presented at the 36th Annual Larval Fish Conference (ALFC), convened in Osøyro, Norway, 2–6 July ...2012. The conference was organized around four theme sessions, three of which are represented with articles in this collection: “Assessing the relative contribution of different sources of mortality in the early life stages of fishes”; “The contribution of mechanistic,
behavioural, and physiological studies on fish larvae to ecosystem models”; “Effects of oil and natural gas surveys, extraction activity and spills on fish early life stages”. Looking back at the main themes of earlier conferences about the early life history of fish reveals that they were not very different from those of ALFC2012. Clearly, we still have a lot of work to do on these and other topics related to the biology and ecology of fish early life stages.
Abstract
The Subarctic copepod, Calanus finmarchicus, is an ecologically critical foundation species throughout the North Atlantic Ocean. Any change in the abundance and distribution of C. ...finmarchicus would have profound effects on North Atlantic pelagic ecosystems and the services that they support, particularly on the coastal shelves located at the southern margins of the species' range. We tested the hypothesis that the physiological rates and processes of C. finmarchicus, determining its vital rates, are unaffected by increases in CO2 concentration predicted to occur in the surface waters of the ocean during the next 100 years. We reared C. finmarchicus from eggs to adults at a control (580 µatm, the ambient concentration at the laboratory's seawater intake) and at predicted mid-range (1200 µatm) and high (1900 µatm) pCO2. There was no significant effect of pCO2 on development times, lipid accumulation, feeding rate, or metabolic rate. Small but significant treatment effects were found in body length and mass (in terms of dry, carbon and nitrogen mass), notably a somewhat larger body size at the mid-pCO2 treatment; that is, a putatively beneficial effect. Based on these results, and a review of other studies of Calanus, we conclude that the present parameterizations of vital rates in models of C. finmarchicus population dynamics, used to generate scenarios of abundance and distribution of this species under future conditions, do not require an “ocean acidification effect” adjustment. A review of research on planktonic copepods indicates that, with only a few exceptions, impacts of increased CO2 are small at the levels predicted to occur during the next century.
FISH PAIN DEBATE Arlinghaus, Robert; Cooke, Steven J.; Browman, Howard I. ...
Issues in science and technology,
09/2020, Letnik:
37, Številka:
1
Journal Article
Recenzirano
In "The Great Fish Pain Debate" (Issues, Summer 2010), Troy Vettese, Becca Franks, and Jennifer Jacquet rightly state that in Germany the assumption that fish feel pain resulted in court cases and ...fishing-related legislation from the 1980s onward. The initial focus was on fishing competitions, which were ruled as unjustifiable because their primary motive was competition and not food. The Bad Oeynhausen case of 2001 on catch-and-release was the last in a long string of cases that dealt with keep nets, put-and-take fishing, and live baitfish. However, the case did not have the importance Vettese et al. attribute to it. Importantly, public surveys published in 2014 show that the majority of the German public has no ethical problem with catch-and-release. In contradiction to what the article's authors imply, catch-and-release continues to be allowed if there is a good reason for it, and competitive fishing events continue to exist whenever an acceptable goal is served, such as to improve water quality by harvesting overabundant cyprinids (a family of freshwater fish that includes carp). The authors suggest that animal rights activists brought about significant changes in German fishing laws to account for fish welfare. However, the key transformative figure was Hermann Drossé, a public attorney and leading figure in the West German umbrella recreational fishing organization. That is, the most significant changes in relation to fish welfare in fishing legislation and practice were brought about by angler associations, not by animal rights activists.Vettese et al. imply I have conflicts of interest. As is natural for a transdisciplinary scientist at the interface of science and society, I maintain productive relationships with many people and organizations that are involved in angling, conservation, and fisheries management. Some of these people or organizations have provided inkind support for distributing surveys or were key information sources, and as such are acknowledged in my papers. These relationships do not affect my position as an honest knowledge broker. Implying I am bought by advocacy groups is absurd.
European eels (Anguilla anguilla) migrate between the southwestern Sargasso Sea and the European and Mediterranean coasts. In a recent paper in Current Biology, Naisbett-Jones et al.1 claim to ...“provide the first evidence that they eels derive positional information from the Earth’s magnetic field” and that this information guides their migration. The evidence reported by Naisbett-Jones et al.1 in support of this conclusion was derived from eels collected in the Severn River (UK), approximately 50 km upstream of the estuary (i.e. not “in the Severn Estuary” as stated by the authors). Eels collected this far into rivers are benthic and fully adapted to freshwater; that is, they are late-stage glass eels (∼ 2 years old), not the pelagic leptocephalus (larval) life stage that actually undertakes the trans-Atlantic migration. The entire interpretive framework for the Naisbett-Jones et al.1 study rests on the assumption that the behaviour of these late-stage freshwater glass eels, and their responses to magnetic fields, can be used as a proxy for the responses of eel leptocephali. The authors present no evidence in support of this key assumption.
Durif et al. take issue with a recent Current Biology study on eel migration.
Small‐scale fisheries (SSFs) tend to target shallow waters, but the depth distributions of coastal fish can vary depending on species, size, and sex. This creates a scope for a form of fishing ...selectivity that has received limited attention but can have considerable implications for monitoring and management of these fisheries. We conducted a case study on the Norwegian wrasse fishery, a developing SSF in which multiple species are caught in shallow waters (mean depth = 4.5 m) to be used as cleaner fish in aquaculture. Several of these wrasses have life histories and behaviors that are sensitive to selective fishing mortality, such as sexual size dimorphism, paternal care, and sex change. An experimental fishery was undertaken over three sampling periods in 2018. Data on catch, length, and sex of wrasses across a depth gradient (0–18 m) were collected and analyzed. We found that depth distributions were species specific and the vertical overlap with the fishery was high for Corkwing Wrasse Symphodus melops and Ballan Wrasse Labrus bergylta, which were most abundant at depths less than 5 m. Three other wrasse species had invariant or increasing abundance with depth and were therefore less likely to be negatively impacted by this fishery. Body size was positively correlated with depth for these wrasses, and sex ratio became more male biased for the Corkwing Wrasse, the only species that could be visually sexed. This study demonstrates that depth can have strong effects on fishing selectivity at multiple scales and that such knowledge is necessary to develop management strategies that balance fishing mortality sustainably across species, sizes, and sexes. We recommend that management priorities be directed toward the Ballan and Corkwing wrasses—the species having the highest vertical overlap with the fishery. Furthermore, CPUE was strongly affected by seasonality and positively correlated with increasing wave exposure for one of the species. This underscores the general importance of standardizing catch data for several environmental covariates when monitoring species that are affected by SSFs.
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