CONTAINMENT SPECIAL
INTRODUCTION
THERE
ARE MANY QUESTION MARKS OVER THE FATE OF ESCAPED FARM
SALMON
with wild stocks. Their be- haviour depends to a large extent on their size at escape – large salmon escaping from offshore cages may survive to adulthood but lack a hom- ing instinct, making them susceptible to predators. Fish that escape into freshwater streams as parr, on the other hand, have very low survival rate but, if they reach adult- hood, would be more likely to return to the river where they were released.
The other alleged nega- tive impact, which applies to all the farmed species, is physical disturbance of wild populations – escaped farmed species will compete for food with wild fish. It is argued that they could also disturb spawn- ing beds of wild fish, such as
salmon redds, or physically displace smaller fish such as wild salmon parr. Another alleged impact is the potential for disease transfer to wild fish, although disease transfer from either wild-to-farmed or farmed-to-wild could take place in the absence of an escape.
Many solutions have been proposed to mitigate the impacts of fish escapes, but only some of these are likely to be applied. Farmers could use only local strains of fish, for example, although this is unlikely to be economically feasible. Attempts should be made to recapture escaped fish, but salmon tend to dis- perse rapidly, making recap- ture difficult. Strengthening the status of wild stocks could
make them more resilient to the impacts of escapees. A great deal of research has been carried out on optimis- ing the procedures for produc- ing sterile or single-sex fish – all-female salmon would have less impact, should they escape, for example. This approach is now widely accepted for trout in angling waters, although uptake by salmon farmers has been slow because it was initially difficult to achieve consistent quality. However, recent research at the University of Stirling indi- cates that many of the issues have now been overcome. Ultimately, however, by far the best mitigating measure is to prevent escapes in the first place. This requires a co-ordinated approach to the
FISH ESCAPE STATISTICS – NUMBER OF RECORDED FISH ESCAPES AND NUMBER OF INCIDENTS IN BRACKETS
issue, across all aspects of the fish farming cycle. And, as explained throughout this spe- cial edition of Fish Farmer, this is something which is now ap- parent in the Scottish aquacul- ture industry. Fish farmers are showing a completely different attitude towards escapes – as is reflected by better reporting, investment in new equipment, the development of better working practices, the transfer of best practice through train- ing and the development of new equipment standards for Scottish aquaculture. As fish farmers we all know we are to some extent at the mercy of the elements, but it appears that the industry’s proactive approach is starting to pay dividends that can only enhance its reputation as a forward-looking, environmen- tally responsible neighbour.
SOURCE: MARINE SCOTLAND
www.fishfarmer-magazine.com
LEFT: THE NUMBER OF FISH ESCAPES IN SCOTLAND BY SPECIES, 2007-2010
7
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100