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59 results for “fish farming”

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dryad32/100

Data from: Density-dependent changes in neophobia and stress-coping styles in the world's oldest farmed fish

Farmed fish are typically reared at densities much higher than those observed in the wild, but to what extent crowding results in abnormal behaviours that can impact welfare and stress coping styles is subject to debate. Neophobia (i.e. fear of the 'new') is thought to be adaptive under natural conditions by limiting risks, but it is potentially maladapted in captivity, where there are no predators or novel foods. We reared juvenile Nile tilapia (Oreochromis niloticus) for six weeks at either high (50g/L) or low density (14g/L), assessed the extent of skin and eye darkening (two proxies of chronic stress), and exposed them to a novel object in an open-test arena, with and without cover, to assess the effects of density on neophobia and stress coping styles. Fish reared at high density were darker, more neophobic, less aggressive, less mobile and less likely to take risks than those reared at low density, and these effects were exacerbated when no cover was available. Thus, the reactive coping style shown by fish at high density was very different from the proactive coping style shown by fish at low density. Our findings provide novel insights into the plasticity of fish behaviour and the effects of aquaculture intensification on one of the world's oldest farmed and most invasive fish, and highlight the importance of considering context. Crowding could have a positive effect on the welfare of tilapia by reducing aggressive behaviour, but it can also make fish chronically stressed and more fearful, which could make them less invasive.

opencc-zeroDec 2017View details →

dryad32/100

Data from: Cleaner fish escape salmon farms and hybridize with local wrasse populations

The genetic impact of farmed fish escaping aquaculture is a highly debated issue. However, non-target species, such as cleaner fish used to remove sea lice from farmed fish, are rarely considered. Here we report that wild corkwing wrasse (Symphodus melops), which are transported long distances to be used as cleaner fish in salmon farms, escape and hybridize with local populations. Recently, increasing numbers of corkwing wrasse have been reported in Flatanger in Norway, north of its described distribution range, an area heavily relying on import of cleaner fish from Skagerrak. Using genetic markers identified with 2bRAD sequencing, we show that, although the Flatanger population largely is a result of a northwards range expansion, there is also evidence of considerable gene flow from southern populations in Skagerrak and Kattegat. Out of 40 corkwing wrasses sampled in Flatanger, we discovered two individuals with clear southern genotypes, one first generation hybrid, and twelve potential second-generation hybrids. In summary, we provide evidence that corkwing wrasse escape from fish farms and hybridize with local populations at the leading edge of an ongoing range expansion. Although the magnitude and significance of escapees warrants further investigation, these results should be taken in consideration in the use of translocated cleaner fish.

opencc-zeroDec 2017View details →

dryad32/100

Data from: Environmental monitoring through protist NGS metabarcoding: assessing the impact of fish farming on benthic foraminifera communities

The measurement of species diversity represents a powerful tool for assessing the impacts of human activities on marine ecosystems. Traditionally, the impact of fish farming on the coastal environment is evaluated by monitoring the dynamics of macrobenthic infaunal populations. However, taxonomic sorting and morphology-based identification of the macrobenthos demands highly trained specialists and is extremely time-consuming and costly, what makes it unsuitable for large-scale biomonitoring efforts involving numerous samples. Here, we propose to alleviate this laborious task by developing protist metabarcoding tools based on next-generation sequencing (NGS) of environmental DNA and RNA extracted from sediment samples. In this study, we analysed the response of benthic foraminiferal communities to the variation of environmental gradients associated with salmon farms in Scotland. We investigated the foraminiferal diversity based on ribosomal minibarcode sequences generated by the Illumina NGS technology. We compared the molecular data with morphospecies counts and with environmental gradients, including distance to cages and Redox used as a proxy for sediment oxygenation. Our study revealed high variations between foraminiferal communities collected in the vicinity of fish farms and at distant locations. We found evidence for alpha diversity loss in strongly impacted sites, especially visible in the RNA data. We also detected some candidate bioindicator foraminiferal species. Based on this proof-of-concept study, we conclude that NGS metabarcoding using foraminifera and other protists has considerable potential to become a new tool for surveying the impact of aquaculture and other industrial activities in the marine environment.

opencc-zeroDec 2013View details →

dryad32/100

Data from: Winning the invasion roulette: escapes from fish farms increase admixture and facilitate establishment of non-native rainbow trout

Aquaculture is a major source of invasive aquatic species, despite the fact that cultured organisms often have low genetic diversity and tend to be maladapted to survive in the wild. Yet, to what extent aquaculture escapees become established by means of high propagule pressure and multiple origins is not clear. We analysed the genetic diversity of 15 established populations and 4 farmed stocks of non-native rainbow trout in Chile, a species first introduced for recreational fishing around 1900, but which has in recent decades escaped in large numbers from fish farms and become widespread. Aquaculture propagule pressure was a good predictor of the incidence of farm escapees, which represented 16% of all free-ranging rainbow trout and were present in 80% of the study rivers. Hybrids between farm escapes and established trout were present in all rivers at frequencies ranging between 7 and 69%, and population admixture was positively correlated with genetic diversity. We suggest that non-native salmonids introduced into the Southern Hemisphere could benefit from admixture because local adaptations may not have yet developed and there may be initially little fitness loss resulting from outbreeding depression.

opencc-zeroDec 2010View details →

zenodo32/100

FIGURE 3 in A new species of Ophryotrocha (Annelida: Dorvilleidae) associated with fish farming at Macquarie Harbour, Tasmania, Australia

FIGURE 3. Ophryotrocha shieldsi, sp. nov. A, anterior end, dorsal view. B, same, ventral view; C, posterior end, dorsal view; D, median parapodium, anterior view; E, simple chaeta; F, heterogomph falciger; G, mandibles, dorsal view; H, Pmaxillae, dorsal view; I, K-maxillae, dorsal view; Abbreviations: al, acicular lobe; cls, carrier-like structure; dc, dorsal cirrus; F, forceps; vc, ventral cirrus; vcl, ventral chaetal lobe; numerals refer to anterior denticles.

opennotspecifiedDec 2010View details →

zenodo32/100

FIGURE 2 in A new species of Ophryotrocha (Annelida: Dorvilleidae) associated with fish farming at Macquarie Harbour, Tasmania, Australia

FIGURE 2. Ophryotrocha shieldsi, sp. nov. SEM images. A, complete specimen, dorsal view; B, anterior end, dorsal view; C, same, ventral view; D, median parapodia, anteroventral view; E, distal part of parapodium showing chaetae, anterior view; F, posterior body region, showing paired rosette glands, dorsal view; G, enlarged rosette gland; H, Pmaxillae, ventral view.

opennotspecifiedDec 2010View details →

zenodo32/100

FIGURE 1 in A new species of Ophryotrocha (Annelida: Dorvilleidae) associated with fish farming at Macquarie Harbour, Tasmania, Australia

FIGURE 1. Maps of Tasmania (inset) and Macquarie Harbour. Squares and star denote locations of sea cages, with star marking type locality of Ophryotrocha shieldsi, sp. nov.

opennotspecifiedDec 2010View details →

dryad32/100

Data from: Rich resource environment of fish farms facilitates phenotypic variation and virulence in an opportunistic fish pathogen

Phenotypic variation is suggested to facilitate the persistence of environmentally growing pathogens under environmental change. Here we hypothesized that the intensive farming environment induces higher phenotypic variation in microbial pathogens than natural environment, because of high stochasticity for growth and stronger survival selection compared to the natural environment. We tested the hypothesis with an opportunistic fish pathogen Flavobacterium columnare isolated either from fish farms or from natural waters. We measured growth parameters of two morphotypes from all isolates in different resource concentrations and two temperatures relevant for the occurrence of disease epidemics at farms and tested their virulence using a zebrafish (Danio rerio) infection model. According to our hypothesis, isolates originating from the fish farms had higher phenotypic variation in growth between the morphotypes than the isolates from natural waters. The difference was more pronounced in higher resource concentrations and the higher temperature, suggesting that phenotypic variation is driven by the exploitation of increased outside-host resources at farms. Phenotypic variation of virulence was not observed based on isolate origin but only based on morphotype. However, when in contact with the larger fish, the less virulent morphotype of some of the isolates also had high virulence. As the less virulent morphotype also had higher growth rate in outside-host resources, the results suggest that both morphotypes can contribute to F. columnare epidemics at fish farms, especially with current prospects of warming temperatures. Our results suggest that higher phenotypic variation per se does not lead to higher virulence, but that environmental conditions at fish farms could select isolates with high phenotypic variation in bacterial population and hence affect evolution in F. columnare at fish farms. Our results highlight the multifaceted effects of human-induced environmental alterations in shaping epidemiology and evolution in microbial pathogens.

opencc-zeroFeb 2022View details →

ClinicalTrials.gov32/100

Farmed Fish Human Intervention Study

ClinicalTrials.gov study NCT01916434. IPD Sharing: Not stated. Countries: 1. Publications: 1.

restrictedIPD-UNDECIDEDFeb 2026View details →

dryad32/100