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Fin erosion on rainbow trout on commercial trout farms in the United Kingdom
  1. S. St-Hilaire, DVM, MSc, PhD1,
  2. T. Ellis, BSc, MSc, PhD1,
  3. A. Cooke, BSc1,
  4. B. P. North, BSc, MSc, PhD2,
  5. J. F. Turnbull, BVM&S, MSc, PhD, ILTM, MRCVS2,
  6. T. Knowles, BSc, MSc, PhD, CStat, CBiol, MIBiol, ILTM3 and
  7. S. Kestin, BSc, PhD3
  1. 1 CEFAS Weymouth Laboratory, Barrack Road, The Nothe, Weymouth DT4 8UB
  2. 2 Institute of Aquaculture, University of Stirling, Stirling FK9 4LA
  3. 3 Division of Food Animal Science, Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU
  1. Dr St-Hilaire's present address is Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA


Fish weighing less than 30 g and more than 100 g were sampled from 38 rearing units on 10 commercial farms growing rainbow trout for the table market. A fin index was calculated for each of the eight rayed fins on 949 trout by dividing their length by the standard length of the fish. There was a large range in the indices of all eight fins. The fin indices of the small and large fish were compared, controlling for farm effect. With the exception of the dorsal fin, all the indices were larger for the small fish than for the large fish, but the magnitude of the difference was greater for some fins than others. In comparison with the fins of wild fish, the pectoral and dorsal fins appeared to be most eroded and the damage to these fins was evident even in the small fish. The erosion of the caudal, anal and ventral (or pelvic) fins was more prominent in the larger fish. Variations in the fin indices of the caudal, anal and ventral fins suggested that there was little variation between rearing units on the same farm, but that there was significant variation between individual fish in the same rearing units, and between fish on different farms.

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