Page 0063

Appendix 1

RSPCA welfare standards for farmed Atlantic salmon 56 September 2015

* indicates an amendment

5. The 'feed-back loop'

In a pre-slaughter crowd, if fish are frightened or panicked into swimming fast, several things happen:

 they use up oxygen in the water faster. This in turn will cause further panic as the fish try to find

better quality water

 the fish injure themselves on the enclosure net and on each other, leading to further panic (and

increased downgrading from scale loss, injury and bruising)

 the more the fish swim fast, the more muscle glycogen they use up. This will mean that the

carcasses will be prone to gaping and could have paler flesh.

In a pre-slaughter crowd, once fish start to panic and swim vigorously the situation can easily get out of

hand and result in mortality and downgrading. Crowding must be done gently and carefully so that fish do

not panic, or years of care rearing top quality fish can be undone in a few minutes.

6. Signs to watch out for

In a carefully crowded enclosure, the fish will look calm. Fish will be swimming leisurely. Obviously they will

be encountering other fish frequently but they will avoid them with a flick of the tail. Fish will slide along the

net and turn casually when they reach an obstruction. No fish will be burrowing into the enclosure net trying

to escape. Only the odd dorsal fin of fish will be breaking the surface.

When fish are stressed in a pre-slaughter crowd, fish will be swimming fast and could be trying to burrow

into the bottom, sides or corners of the net trying to escape. If parts of the back of any fish, in addition to the

dorsal fin, are exposed when they swim close to the surface or over each other, then they are almost

certainly crowded too much. Fish scales seen suspended in the water column downstream from crowded

fish are a clear sign that the crowd is too dense and fish are damaging themselves. Snout damage in the

form of sore or bleeding snouts seen on fish after slaughter is also a clear sign that fish have been

burrowing into the net. If any of the signs of stressed fish are seen, the fish need to be given more room

quickly. Dissolved oxygen in the water must be monitored during the crowd but monitoring oxygen is not a

substitute for observing the fish for signs of stress.

See RSPCA welfare standards - HP 2.18 and HP 2.19

7. Maintaining a good crowd

It is important to realise that fish will be stressed even in a well-crowded enclosure. Therefore, it is

important that the maximum crowd duration is not too long. Generally, two hours should be regarded

as a maximum crowd duration.

See RSPCA welfare standards -HP 2.13 and HP 2.14

There is a fine line between a crowd that is too dense, causing excessive activity in the fish, and a crowd

that is not dense enough to maintain an adequate flow of fish to the killing table. The best way to achieve

an adequate but not excessive density of fish is to reduce the volume available gradually as fish are

removed. As a guide, in a good crowd the net will be reduced at approximately 15-minute intervals, and at

more frequent intervals when there are few fish remaining.

When pulling the enclosure nets or sweep net to crowd the fish, try to avoid areas where the net is

shallow just below the surface, or folds causing pockets in the net. These will cause fish to panic if they

become trapped.

To manage the crowd carefully, it should be the responsibility of one person to ensure the fish are carefully

crowded and this person should have no other responsibilities or tasks to perform to distract him/her.

Index

  1. Page 0001
  2. Page 0002
  3. Page 0003
  4. Page 0004
  5. Page 0005
  6. Page 0006
  7. Page 0007
  8. Page 0008
  9. Page 0009
  10. Page 0010
  11. Page 0011
  12. Page 0012
  13. Page 0013
  14. Page 0014
  15. Page 0015
  16. Page 0016
  17. Page 0017
  18. Page 0018
  19. Page 0019
  20. Page 0020
  21. Page 0021
  22. Page 0022
  23. Page 0023
  24. Page 0024
  25. Page 0025
  26. Page 0026
  27. Page 0027
  28. Page 0028
  29. Page 0029
  30. Page 0030
  31. Page 0031
  32. Page 0032
  33. Page 0033
  34. Page 0034
  35. Page 0035
  36. Page 0036
  37. Page 0037
  38. Page 0038
  39. Page 0039
  40. Page 0040
  41. Page 0041
  42. Page 0042
  43. Page 0043
  44. Page 0044
  45. Page 0045
  46. Page 0046
  47. Page 0047
  48. Page 0048
  49. Page 0049
  50. Page 0050
  51. Page 0051
  52. Page 0052
  53. Page 0053
  54. Page 0054
  55. Page 0055
  56. Page 0056
  57. Page 0057
  58. Page 0058
  59. Page 0059
  60. Page 0060
  61. Page 0061
  62. Page 0062
  63. Page 0063
  64. Page 0064
  65. Page 0065
  66. Page 0066
  67. Page 0067
  68. Page 0068
  69. Page 0069
  70. Page 0070
  71. Page 0071
  72. Page 0072
  73. Page 0073
  74. Page 0074
  75. Page 0075
  76. Page 0076
  77. Page 0077
  78. Page 0078
  79. Page 0079
  80. Page 0080