The welfare implications of fin clipping in fish.

I was recently asked by a member of the Animal Ethics Committee on whether I considered fin clipping a painful procedure in fish. There’s no simple yes/no answer and as veterinarians/scientists, we need to qualify our answers with logical reasoning.

The short answer is that YES, it is a PAINFUL procedure, but the pain is only TRANSIENT.

The tail fin in carp has been documented to contain A-δ and C-type axons (these transmit nociceptive [pain] signals in [higher] vertebrates).This said, it would be difficult to discriminate between the pain from clipping procedure and the handling stress.

Provided that the biopsy is not substantial (no more than 50% of the fin should be resected), the pain would only be transient, and there should be no bleeding. And provided that the procedure is conducted aseptically, and the water quality, nutrition and immunity of fish are optimal, the fin should heal quickly and will regrow. Topical anaesthetic like lidocaine may be beneficial.

One thing that needs consideration is how it would affect the swimming ability of the fish after fin-clipping. In more sedentary fish, it should not be an issue. But if it were the zebrafish that swims at speeds continuously, they rely heavily on the caudal and pectoral fins for swimming. So I would argue that these fins should be avoided for clipping. On another note, the fins that show fastest regeneration times in salmon are the anal fin and the pectoral fins. Conversely, the adipose fin (in species that have them) and pelvic fins show slowest regeneration times in salmon.

So if fin-clips are for collecting genetic material from individual fish for the purpose of genotyping, I’d suggest sampling the anal fin. However, if fin clipping is used for marking/identifying individuals, the pelvic fins might be more suitable because it means fewer repeats are needed for longer studies.

Yours sincerely,

Doctor Richmond Loh

DipProjMgt, BSc, BVMS, MPhil (Pathology), MANZCVS (Aquatics & Pathobiology), CertAqV, CMAVA, NATA Signatory.
THE FISH VET, Perth, Western Australia, AUSTRALIA.
Mobile Aquatic Veterinary Medical & Diagnostic Services.
Ph: +61 (0)421 822 383

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