Summary
The accelerated growth of finfish aquaculture has resulted in a series of developments detrimental to the environment and human health. The latter is illustrated by the widespread and unrestricted use of prophylactic antibiotics in this industry, especially in developing countries, to forestall bacterial infections resulting from sanitary shortcomings in fish rearing. The use of a wide variety of antibiotics in large amounts, including non-biodegradable antibiotics useful in human medicine, ensures that they remain in the aquatic environment, exerting their selective pressure for long periods of time. This process has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase of antibiotic resistance in fish pathogens, in the transfer of these resistance determinants to bacteria of land animals and to human pathogens, and in alterations of the bacterial flora both in sediments and in the water column. The use of large amounts of antibiotics that have to be mixed with fish food also creates problems for industrial health and increases the opportunities for the presence of residual antibiotics in fish meat and fish products. Thus, it appears that global efforts are needed to promote more judicious use of prophylactic antibiotics in aquaculture as accumulating evidence indicates that unrestricted use is detrimental to fish, terrestrial animals, and human health and the environment.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1462-2920.2006.01054.x

Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment

We examined the status of diadromous (migratory between saltwater and freshwater) fishes within the North Atlantic basin, a region of pronounced declines in fisheries for many obligate marine species. Data on these 24 diadromous (22 anadromous, 2 catadromous) species are sparse, except for a few high-value forms. For 35 time series, relative abundances had dropped to less than 98% of historic levels in 13, and to less than 90% in an additional 11. Most reached their lowest levels near the end of the observation period. Many populations persist at sharply reduced levels, but all species had suffered population extirpations, and many species are now classified as threatened or endangered. Habitat loss (especially damming), overfishing, pollution, and, increasingly, climate change, nonnative species, and aquaculture contributed to declines in this group. For those diadromous fishes for which data exist, we show that populations have declined dramatically from original baselines. We also discuss the consequen...

https://www.jstor.org/stable/10.1525/bio.2009.59.11.7

Dramatic Declines in North Atlantic Diadromous Fishes

http://digital.csic.es/bitstream/10261/44729/1/Taranger%20et%20al_%2c%20GCE.pdf

Control of puberty in farmed fish

Ecological risk assessment for the effects of fishing

Here we critically review the scale and extent of adaptive genetic variation in Atlantic salmon (Salmo salar L.), an important model system in evolutionary and conservation biology that provides fundamental insights into population persistence, adaptive response and the effects of anthropogenic change. We consider the process of adaptation as the end product of natural selection, one that can best be viewed as the degree of matching between phenotype and environment. We recognise three potential sources of adaptive variation: heritable variation in phenotypic traits related to fitness, variation at the molecular level in genes influenced by selection, and variation in the way genes interact with the environment to produce phenotypes of varying plasticity. Of all phenotypic traits examined, variation in body size (or in correlated characters such as growth rates, age of seaward migration or age at sexual maturity) generally shows the highest heritability, as well as a strong effect on fitness. Thus, body size in Atlantic salmon tends to be positively correlated with freshwater and marine survival, as well as with fecundity, egg size, reproductive success, and offspring survival. By contrast, the fitness implications of variation in behavioural traits such as aggression, sheltering behaviour, or timing of migration are largely unknown. The adaptive significance of molecular variation in salmonids is also scant and largely circumstantial, despite extensive molecular screening on these species. Adaptive variation can result in local adaptations (LA) when, among other necessary conditions, populations live in patchy environments, exchange few or no migrants, and are subjected to differential selective pressures. Evidence for LA in Atlantic salmon is indirect and comes mostly from ecological correlates in fitness-related traits, the failure of many translocations, the poor performance of domesticated stocks, results of a few common-garden experiments (where different populations were raised in a common environment in an attempt to dissociate heritable from environmentally induced phenotypic variation), and the pattern of inherited resistance to some parasites and diseases. Genotype x environment interactions occurr for many fitness traits, suggesting that LA might be important. However, the scale and extent of adaptive variation remains poorly understood and probably varies, depending on habitat heterogeneity, environmental stability and the relative roles of selection and drift. As maladaptation often results from phenotype-environment mismatch, we argue that acting as if populations are not locally adapted carries a much greater risk of mismanagement than acting under the assumption for local adaptations when there are none. As such, an evolutionary approach to salmon conservation is required, aimed at maintaining the conditions necessary for natural selection to operate most efficiently and unhindered. This may require minimising alterations to native genotypes and habitats to which populations have likely become adapted, but also allowing for population size to reach or extend beyond carrying capacity to encourage competition and other sources of natural mortality.

A critical review of adaptive genetic variation in Atlantic salmon: implications for conservation

The farming of salmon and other marine finfish in open net pens continues to increase along the world's coastlines as the aquaculture industry expands to meet human demand. Farm fish are known to escape from pens in all salmon aquaculture areas. Their escape into the wild can result in interbreeding and competition with wild salmon and can facilitate the spread of pathogens, thereby placing more pressure on already dwindling wild populations. Here we assess the ecological, genetic, and socioeconomic impacts of farm salmon escapes, using a risk-assessment framework. We show that risks of damage to wild salmon populations, ecosystems, and society are large when salmon are farmed in their native range, when large numbers of salmon are farmed relative to the size of wild populations, and when exotic pathogens are introduced. We then evaluate the policy and management options for reducing risks and discuss the implications for farming other types of marine finfish.

https://www.jstor.org/stable/10.1641/0006-3568%282005%29055%5B0427%3AFSATRO%5D2.0.CO%3B2

Fugitive Salmon: Assessing the Risks of Escaped Fish from Net-Pen Aquaculture

From the docks of declining coastal villages to the desks of corporate and government offices, salmon farming has been hailed as a new hope for the world's ailing offshore fishing industry and a way to reduce pressure on severely depleted fish stocks. However, the aquaculture industry has grown so quickly that, in many areas-including the Pacific Northwest-it has outstripped the wherewithal to address its adverse ecological impacts. Will fish farms, in the end, do more harm than good? Or can they deliver on their sustainable promise?

Salmon Aquaculture in the Pacific Northwest A Global Industry with Local Impacts

Ocean-zoning arguments often center on the biology of ocean species, the geography of fishing-use patterns, and the need for preventing use conflicts. Here we expand this discussion to the social and legal aspects of ocean zoning, focusing on comprehensive planning, segregation of activities into use-priority areas, and the allocation of user rights within each zone. The inclusion of all of these features within an ocean-zoning regime can be a catalyst for a variety of ancillary benefits, including opportunities for user groups to form informal or formal long-lived institutions and a reassessment of the focus and scope of the regulatory institutions involved in ocean management. Along with the ability of users to negotiate and trade within and between zones, both features will lead to improved conflict resolution, efficiency of use, and ecosystem stability - critical components for the production of ecosystem services and maintenance of biological and human economic benefits.

Comprehensive Planning, Dominant-Use Zones, and User Rights: A New Era in Ocean Governance

Over a third of the nation's fish stocks currently are overfished. These stocks historically supported some of America's most important fisheries: cod, salmon, rockfish, tuna, and red snapper, to list only a few. This study, initiated and supported by the Pew Charitable Trusts, looks in detail at the mandates, constitution, rules, and procedures of the regional fish councils to determine whether the counsils can effectively manage the nation's fisheries. The report discussed four key problems that plague the councils and suggests ways to implement changes.

Josh Eagle

Papers

Fugitive Salmon: Assessing the Risks of Escaped Fish from Net-Pen Aquaculture

Salmon Aquaculture in the Pacific Northwest A Global Industry with Local Impacts

Comprehensive Planning, Dominant-Use Zones, and User Rights: A New Era in Ocean Governance

Taking stock of the regional fishery management councils

Answering Lord Perry's question: dissecting regulatory overfishing