Plasticity in growth of farmed and wild Atlantic salmon: is the increased growth rate of farmed salmon caused by evolutionary adaptations to the commercial diet?

Abstract

BackgroundDomestication of Atlantic salmon for commercial aquaculture has resulted in farmed salmon displaying substantially higher growth rates than wild salmon under farming conditions. In contrast, growth differences between farmed and wild salmon are much smaller when compared in the wild. The mechanisms underlying this contrast between environments remain largely unknown. It is possible that farmed salmon have adapted to the high-energy pellets developed specifically for aquaculture, contributing to inflated growth differences when fed on this diet. We studied growth and survival of 15 families of farmed, wild and F1 hybrid salmon fed three contrasting diets under hatchery conditions; a commercial salmon pellet diet, a commercial carp pellet diet, and a mixed natural diet consisting of preserved invertebrates commonly found in Norwegian rivers.ResultsFor all groups, despite equal numbers of calories presented by all diets, overall growth reductions as high 68 and 83%, relative to the salmon diet was observed in the carp and natural diet treatments, respectively. Farmed salmon outgrew hybrid (intermediate) and wild salmon in all treatments. The relative growth difference between wild and farmed fish was highest in the carp diet (1: 2.1), intermediate in the salmon diet (1:1.9) and lowest in the natural diet (1:1.6). However, this trend was non-significant, and all groups displayed similar growth reaction norms and plasticity towards differing diets across the treatments.ConclusionsNo indication of genetic-based adaptation to the form or nutritional content of commercial salmon diets was detected in the farmed salmon. Therefore, we conclude that diet alone, at least in the absence of other environmental stressors, is not the primary cause for the large contrast in growth differences between farmed and wild salmon in the hatchery and wild. Additionally, we conclude that genetically-increased appetite is likely to be the primary reason why farmed salmon display higher growth rates than wild salmon when fed ad lib rations under hatchery conditions. Our results contribute towards an understanding of the potential genetic changes that have occurred in farmed salmon in response to domestication, and the potential mechanisms underpinning genetic and ecological interactions between farmed escapees and wild salmonids.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0841-7) contains supplementary material, which is available to authorized users.

Stable Core Gut Microbiota across the Freshwater-to-Saltwater Transition for Farmed Atlantic Salmon

“…The difference in the ratio of Firmicutes to Proteobacteria between wild and farmed salmon resembled that with high-and low-fat diets, where a high-fat diet increased the ratio of Firmicutes to Proteobacteria (16). Thus, the differences in gut microbiota between wild and farmed salmon could partly reflect the high fat and energy content in the farmed salmon feed compared to that of the natural diet (17).…”

Rapid growth causes abnormal vaterite formation in farmed fish otoliths

“…Salmon eggs (wild-caught broodstock, commercial strain A, and their F1 hybrids) were reared together in ∼6°C/complete darkness, and hatched in January 2014 (see Harvey et al, 2016, for experiment details). In March, 2700 fry were transferred to six freshwater tanks (450 fry per tank, n=2 tanks per diet treatment).…”

Sex determining gene transposition as an evolutionary platform for chromosome turnover

“…Over the past decade, we have studied an experimental population of domesticated and wild Atlantic salmon and their crosses at the aquaculture facility owned by the Institute of Marine Research located in Matre, western Norway (Solberg et al 2013;Solberg et al 2014;Ayllon et al 2015;Harvey et al 2016;Glover et al 2018;Harvey et al 2018). The reader is directed to these publications for full details regarding the standard rearing conditions experienced in this fish farm.…”

“…Total DNA from all offspring and parents was purified using the Qiagen DNeasy Blood & Tissue Kit (Qiagen, Hilden, Germany) according to the manufacturer´s recommendations Microsatellite DNA parentage testing was used to unambiguously identify the pedigree of all individuals used in this study using the exclusion based method implemented in FAP (Taggart 2007). The laboratory conducting these analyses has extensive experience in DNA parentage testing (Solberg et al 2013;Solberg et al 2014;Harvey et al 2016;Glover et al 2018;Harvey et al 2018), and the full details regarding the markers used and their amplification conditions are available in these previous studies. In addition to microsatellites, a set of 116 genome-wide distributed SNPs were genotyped in all offspring and parents for the purpose of linkage mapping (see below).…”