Skip to main content


Title: Triploid Trout in Native Trout Waters: Phase 1 - Literature Review and Recommendations for Phase 2
Author: G Pawson M
Author: Agency : Bristol Environment
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1478, Representation ID: 517, Object ID: 2630
This report presents the results of four tasks: a review of the triploiding process and biology of all-female triploid brown trout; a review of commercial triploiding practices; an assessment of the feasibility of large-scale production of triploid brown trout in England and Wales, and design of future investigations comparing fishery performance and impacts of stocked diploid and triploid brown trout on wild brown trout stocks (Phase 2 of the Environment Agency project). The outcome of this project will inform a review scheduled to take place in 2006 to assess whether further restrictions on the stocking of farm-bred diploid trout (exclusive of those bred from local wild brood stock) and their substitution by triploid brown trout are justified. The literature review covered the scientific and technical advances and effectiveness of the processes used to produce sterile triploid trout and the biological characteristics of triploid brown trout, and was combined with information obtained from interviews with other researchers, farmers currently producing triploid trout (both brown and rainbow) in the UK and others who have experience of the performance of triploids in fisheries. We conclude that there is no evidence that the release of all-female triploid brown trout would adversely affect the genetic integrity of natural stocks of brown trout. Though diploids appear to be more aggressive than triploid trout and compete better in farm conditions, stocked triploids (especially if they are larger than wild fish) will, nevertheless, compete with wild trout for limited food and habitat resources. From the anglers' point-of-view, the behaviour of triploid brown trout may be similar to ”normal” stock fish, though they will show better condition in winter and spring and their flesh quality is likely to be less variable seasonally. It is possible that they may show poorer performance at elevated temperatures. A review of commercial practices, to assess the technical feasibility of producing triploid brown (and rainbow) trout in England and Wales, was based on interviews with trout farmers. We conclude that there is considerable potential for increased triploid brown trout production by both current brown and rainbow trout producers in England and Wales, though this may be constrained by a lack of technical knowledge (which is not freely available). Dissemination of the method for triploid production would facilitate uptake of the technology, and more research is required to identify the water temperature and quality parameters required for triploid production. The final part of this report outlines the design of a programme of investigations to compare biological and fishery performance of diploid and all-female triploid brown trout stocked in rivers, and a means to evaluate objectively the risks of stocking with triploids. The field programme is based on population sampling in a range of fisheries and river types, where all-female triploid brown trout and diploid brown trout are stocked alongside wild trout, using marked or tagged batches of stocked fish, anglers' catch records and electro-fishing.
Publisher: Environment Agency
Subject Keywords: FisheriesFishery managementTroutRiversSalmon fisheriesAngling
Taxonomic Keywords: Salmo truttaOncorhynchus mykiss
Extent: 71
Total file downloads: 295

Download PDF    Display PDF in separate tab