Trout stocking the science

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1 Trout stocking the science Godfrey Williams Environment & Business Manager (Fisheries) September 2014

6 Background! 2003 National Trout & Grayling strategy! Native trout waters & Wild fishery protection zones! Extensive R&D on effects of stocking with farm bred fish and on triploid trout! 2007 Review, consultation and workshop.

7 Background! Environment Agency Board decision 2008! From 2015 (January), consent only to stock sterile (triploid) brown trout the likely option to support angling! Alternative of using trout from locally sourced brood stock most likely for restoration/conservation! Exception is stocking totally or mostly enclosed waters with no significant brown trout breeding! New rules phased in with ambition to halve stocking of fertile (diploid) trout by 2013

8 Background! Subsequent developments! Salmon & Trout Association recommendation: farmed salmon to be triploid only! Continuing support for Wild Trout Trust to give advice and support on habitat and fisheries management! Further research on specific supporting issues via PhD at Stirling University more later..! Since 2007, 75% reduction in stocking fertile farm trout

9 26 colours representing 26 mtdna gene variants (81 populations not all shown) 12 variants found only in one population each Based on data in McKeown et al J Fish Biol, in press

10 Wild Farms

11 Living North Sea sea trout genetics from Dorte Bekkevold, DTU Aqua 60 river samples analysed

12 Sampling site vs. inferred population group at a very preliminary glance! 9 overall population clusters identified But this does not mean that we cannot distinguish among rivers within clusters!

13 Self assignment of samples ( how good are markers at assigning origin?) an example for 200 SNP markers in north east UK rivers 1 fish (can be either Tyne migrant or low assignment power this will be determined in detailed analysis ) Proportion of fish assigning to each river Spey Deveron Tweed Tyne Wear Tees 1 fish (can be either Tees migrant or low assignment power this will be determined in detailed analysis ) > Even with 4% of the markers at hand, we are able to distinguish among rivers at high statistical po

14 Conclusions from Ferguson review! Founding effects and domestication can result in genetic changes in farm-reared brown trout in a relatively few generations, and in some circumstances even within a single generation. Available data suggest that farm trout become progressively less fit for natural conditions.! Interbreeding between farm-reared brown trout and wild fish can reduce the fitness of wild populations resulting in reduced recruitment, failure of the population to be self-sustaining and possible extinction in vulnerable populations.! Interbreeding between farm-reared brown trout and wild fish has been demonstrated to reduce inter-population genetic variability, which on the basis of accepted population genetics and evolutionary theory is likely to reduce the ability of individual populations, and the species overall, to respond to new environmental challenges.

15 Recommendations! As there is no situation in which such stocking is biologically safe, all supplemental stocking of wild self-sustaining populations involving fertile farm reared and non-native brown trout in England and Wales should be prohibited.! The only forms of stocking permitted should be supportive breeding (first generation offspring of native broodstock) or stocking with sterile triploid fish.! All stocking programmes, irrespective of the type of stocking, should have clearly defined and quantifiable objectives with monitoring procedures to measure success. Prior to any stocking, a risk analysis should be undertaken and potential risks routinely monitored after stocking has taken place.

16 Further work and consultation! Commissioned Game and Wildlife Conservation Trust to carry out research into triploid behaviour and angling.! Undertook extensive consultation before recommending change in stocking rules! Adopted an implementation date of 1 st January 2015 with voluntary interim targets for reduction in diploid stocking

17 GWCT research! no evidence that triploid trout interfered with spawning wild fish, while there was evidence that farm-strain diploids did;! triploids survived at least as long as farmed diploids post-stocking, though neither strain performed well, particularly in harsher, upland rivers;! triploids remained for longer at the site of release than did farmed diploids;! triploids performed as well as, if not better than farmed diploids in a blind angler study (anglers scored the fishing and eating characteristics of differently tagged stocked fish, but were not aware of which fish were which).

18 Surface feeding! GWCT research found no difference between diploid and triploid in rising to dry fly! Other angling club experience Wiltshire Avon, Tillingbourne no problems with dry fly

19 Further research commissioned! In 2010, 3 year PhD research programme funded at University of Stirling! Aquaculture Group had extensive experience of fish farming and triploids! Four main areas:! Triploid production! Triploid identification! Feeding behaviour! Stress response

20 Stirling research- results! Triploid production! Improved methods! Better quality of fry! Improved yields! Triploid identification! 3 potential methods blood cells, tracers or genetics.! Blood cell measurement rapid and low cost

21 Stirling research - results! Feeding behaviour! No difference in surface feeding between diploids and triploids! Diploids were more aggressive! Stress (simulates fish being rod-caught)! No difference in recovery after exercise between diploids and triploids

23 Current situation to 2014! National picture -75% fewer fertile farm trout stocked.! Interim targets of 30% reduction in fertile farm strain trout by 2010 and 50% by 2013 were both met.! Combination of fewer fish stocked and move to use of triploids.

24 Trout stocked into rivers Diploid Triploid Grand Total

25 Supportive breeding! If bottlenecks can be identified, supportive breeding can be used to assist in stock recovery! Essential to carry out the procedures properly! Potential for more damage to wild stocks! Broodstock numbers! Hatchery protocols! Limited time in hatchery before release

26 To conclude...! The Environment Agency will stop giving consent to stock fertile farmed brown trout into rivers and most lakes in England and Wales from 2015 (January)! There are no plans to review this position, developed on the basis of extensive evidence! Support is available to angling clubs to assist in better management of fisheries from Environment Agency & partners! We will continue to work with the trout farming industry! The work at Stirling should result in improved quality of triploids supplied by trout farms.

The UK Experience with use of Triploids for Restocking

The UK Experience with use of Triploids for Restocking Management of Brown Trout (Salmo trutta) Stocking in England and Wales Dr Brian Shields Senior Fisheries Scientist GENIMPACT 19 th to 21 st April