RAFTS STOCKING POLICY

Transcription

1 RAFTS STOCKING POLICY Why do we need a policy? Salmon biology & ecology relevant to stocking Stocking process & outcomes Types of stocking The RAFTS policy Alan Kettle-White RAFTS Conference 20 th March 2014

2 Why do RAFTS need a (new) policy? 12.7 million Salmon stocked in Scotland in 2010 First and sometimes the only option used Treatment of symptoms rather than causes Revolution in understanding of salmon biology Case studies / research observations

3 Relevant Facts Salmon stocks are highly structured into multiple populations Salmon are adapted to a number of habitats distributed in space over time Adaptation shaped through selection by their environments Diversity within & between populations underpins health & wealth of fisheries

4 Relevant Facts; Salmon and trout Females carry lots of eggs Choose dissimilar mates Females spawn with multiple mates Spawn at different redd sites => genetic variation within a population Density dependant survival in freshwater Natural selection is key to population fitness Genetic variation required for adaptation in a changing environment Ultimately self-sustaining wild animals

5 Stocking appeal..adding Value Brood stock capture & holding (x 10 s) What kind? How many? Proportion of wild stock? When and where to capture / Keeping them alive Egg Fertilisation / incubation (x 100,000s) Which fish mates with which other fish? Juvenile rearing (=100,000s) Adding value; Avoid natural selection Enhancement...increase production over wild Stocking out (=10,000s) What life-stage, where & when, exposure to wild Monitoring (=?) returning adult stage / rod catch / next generation

6 Brood-stock Capture & holding Brood-stock would have bred in the wild No net gain in number of total eggs Capture sites Logistical challenges; where possible Capture of non-target fish More than one population Close relatives Farm origin fish Accidental loss of brood-fish Handling damage / equipment failure Losses not reported

7 In the hatchery Crosses between populations (out-breeding) Crosses between close relatives (in-breeding) Matching natural variation (multiple crosses) Matching water chemistry & thermal conditions Developmental rate and wild food availability

8 Juvenile rearing Tanks & cages are simple environments No starvation, floods, predators Raised levels of aggression Fast growth Behavioural & morphological differences Domestic (unnatural) selection Exacerbated by time spent in hatchery Results in comparatively poorer survival

9 Post-release consequences Competition with wild-spawned juveniles for space and food (WANE Act) Larger and more aggressive stocked fish can displace wild fish Utilise resources, but fewer make it to smolt or return from the sea. Overall negative contribution Overall contribution vary with balance of wild / hatchery returns & size of population Where hatchery contribution is small then no gain to the fishery (large east coast river) Where hatchery contribution is significant then there is impact on the wild population (small west coast river) Hatchery fish can breed with wild fish on-going legacy

10 Types of stocking tools SHORT TERM RESPONSES Re-introduction & restoration programmes Acute decline, collapse or complete loss of stock Requires removal of pressures Specialist skills LONG TERM RESPONSES Mitigation; Loss of freshwater habitat Fishery enhancement; Desire to catch more fish Year-on-year commitment & use of resources No clear evidence that it benefits Scottish fisheries

11 Realities of hatcheries Effectiveness of stocking is impaired by selection by the natural environment that maintain fitness in the species Display different genetic, physical and behavioural characteristics compared to wild fish Lower life-time performance which is heritable Undermine ability to adapt to changes in the environment

12 RAFTS POLICY ON STOCKING There is a large body of scientific evidence that enhancement stocking is ineffective and harmful There is a presumption against stocking undertaken to enhance salmon fisheries Alternative strategies; stock conservation & habitat restoration provide more cost effective and sustainable solutions Many of the principles in this policy may refer equally to sea trout

13 RAFTS POLICY PAPERS Policy; Scotland-2014.pdf Technical paper; content/uploads/2014/03/rafts-stocking-policy- Technical-paper-2014.pdf

14 ICES & NASCO Guidelines Maximise the number of healthy wild salmon that go to sea from home rivers The goal is to protect genetic diversity of salmon and sea trout to maximise their potential to adapt to the changing environment The absolute priority should be to preserve the productive capacity of the resource