Abstract
BackgroundThe rainbow trout (Oncorhynchus mykiss) is one of the most important aquaculture species in the world, and Norway is one of the largest producers. The present study was initiated in response to a request from the Norwegian police authority to identify the farm of origin for 35 escaped rainbow trout captured in a fjord. Eleven samples, each consisting of approximately 47 fish, were collected from the three farms operating in the fjord where the escapees were captured. In order to gain a better general understanding of the genetic structure of rainbow trout strains used in Norwegian aquaculture, seven samples (47 fish per sample) were collected from six farms located outside the region where the escapees were captured. All samples, including the escapees, were genotyped with 12 microsatellite loci.ResultsAll samples displayed considerable genetic variability at all loci (mean number of alleles per locus per sample ranged from 5.4–8.6). Variable degrees of genetic differentiation were observed among the samples, with pair-wise FST values ranging from 0–0.127. Self-assignment tests conducted among the samples collected from farms outside the fjord where the escapees were observed gave an overall correct assignment of 82.5%, demonstrating potential for genetic identification of escapees. In the "real life" assignment of the 35 captured escapees, all were excluded from two of the samples included as controls in the analysis, and 26 were excluded from the third control sample. In contrast, only 1 of the escapees was excluded from the 11 pooled samples collected on the 3 farms operating in the fjord.ConclusionConsiderable genetic variation exists within and among rainbow trout strains farmed in Norway. Together with modern statistical methods, this will provide commercial operators with a tool to monitor breeding and fish movements, and management authorities with the ability to identify the source of escapees. The data generated in this study were used by the Norwegian police to initiate an investigation of the company operating the three farms in the fjord where escapees were observed.
Highlights
The rainbow trout (Oncorhynchus mykiss) is one of the most important aquaculture species in the world, and Norway is one of the largest producers
Whilst the overall correct self-assignment reported here (83%) among the 7 samples collected outside the location where escapees were captured, is slightly less than reported for 12 European rainbow trout strains (92%) [15], it is greater than observed by Glover et al [18] in a study of cage-reared Atlantic salmon
Data from this study demonstrated variable but significant genetic differentiation among samples of fish reported to originate from these strains, with clear opportunities for genetic assignment
Summary
The rainbow trout (Oncorhynchus mykiss) is one of the most important aquaculture species in the world, and Norway is one of the largest producers. In order to gain a better general understanding of the genetic structure of rainbow trout strains used in Norwegian aquaculture, seven samples (47 fish per sample) were collected from six farms located outside the region where the escapees were captured. The rainbow trout (Oncorhynchus mykiss) is one of the most important cultured fish in the world, and is reared in over 65 countries [1]. For a number of fish species reared in culture, even major strains are often poorly or only sporadically characterised at the molecular genetic level, and, the use of genetic markers for breeding assistance is not widespread. Only one major study of European rainbow trout strains has been published [15]
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