Progress towards better welfare at slaughter for wild fish and other marine creatures

Papers and posters etc from these two excellent symposia, held in Portsmouth, UK in July 2011 by the Universities Federation for Animal Welfare and the Humane Slaughter association, included:

Presentation: Electrical stunning of captured fish.
See p18 of HSA Speaker Abstracts

This presentation at the HSA conference describes a study on board Norwegian vessels to establish the time taken for cod and haddock to lose consciousness; to test the viability of carrying out humane slaughter at sea and its effect on fishery operations. The research is being prepared for publication.

During an experimental trawl carried out over a 3-4 hour period (rather shorter than the usual commercial trawl), cod and haddock were landed on board. To test the length of consciousness out of water, the team took five fish shortly after landing and another five every half hour until processing was near completion two hours later. These fish were tested for brain and heart function by EEG and ECG respectively and for behavioural signs of awareness.

After two hours of storage out of water, the cod appeared motionless. However, the EEG test showed that all still showed signs of consciousness. This suggests that the welfare benefits of early stunning and humane slaughter are considerable.

The fish were stunned using a dry-stunning system which had been installed on the boat. This is preferred to a wet-stunning system since a higher current is required in salt water, resulting in tissue damage1. EEG recordings were used to show that a voltage of 52 Vrms at a frequency of 100 Hz for 1 s produces sufficient current to stun cod or haddock. They are then cut and bled to kill them before consciousness returns.

The fish are fed into the dry chamber from a water tank. Recently, equipment has been devised to ensure that fish enter the stunning chamber in not more than one layer of animals. The issue of a sound dosing system2 needs further investigation.

The fishermen responded favourably to the system. Stunned fish are easier to handle, reducing the time taken to gut and rinse them.

The same team is also conducting research in the Netherlands with Dutch fishermen who wish to improve welfare. Early research using EEG measurements on the flatfish turbot and sole suggests that these species can be stunned with a voltage of 100 Vrms. Studies on dab have also started and work on plaice is planned.

1The other alternative method commonly used for farmed marine fish is percussive stunning.

2i.e. to prevent the fish being exposed to pre-shocks. Dosing systems for electrical stunning after dewatering have been developed for farmed species like eel, A. catfish, a hybrid of A. catfish and Vundu catfish and Atlantic salmon.

Poster presentation: Improving welfare in commercial fishing – constraints and opportunities.
See p34 of UFAW Poster Abstracts

This poster presentation, at the UFAW symposium, outlines some examples of fisheries using more humane methods of capture and employing, or experimenting with, humane slaughter methods. Semi-automated percussive stunners for wild fish are currently under development and preliminary results suggest these can provide a marked improvement in quality. It concludes that wild salmon may be one good place to start in developing humane models of fishing since:

  • Some salmon fishers are already using humane slaughter methods
  • These fish are often handed individually and “carefully”
  • It is a high value species
  • Consumers often look to wild salmon as a higher welfare alternative to farmed salmon

and that a premium market in better welfare may help bring better practice across the whole industry. Information in this poster is reproduced at: developing-humane-models-of-fishing

Other presentations on the welfare of fish in commercial fishing

See p26 of HSA Poster Abstracts
See p63 of UFAW Poster Abstracts

Poster presentation “Humane capture & slaughter of commercially-caught wild fish – An emerging issue” argues that the welfare of fish in commercial fishing is a major animal welfare issue on account of the severity and duration of suffering caused and the large numbers of animals involved.

This welfare issue is also included in the survey of veterinary surgeons presented in the poster “Prioritising issues in animal welfare: findings from an online survey of veterinary surgeons”.

Presentation: “Do crustaceans experience pain?”

See p9 of HSA Speaker Abstracts

When Professor Elwood was asked this question by Rick Stein he decided to investigate. Vast numbers of these animals are eaten, a fact which he illustrates as follows: if you ate beef every day you might consume 25 individual cattle over a lifetime whereas the same number of individual prawns could be consumed in just a single prawn cocktail.

In his experiments crabs and hermit crabs demonstrated avoidance learning when subjected to electric shocks. Hermit crabs subjected to electric shocks in their shells were more likely to leave their shell if it was a preferred type of shell, indicating some motivational trade-off. Given new shells, shocked hermit crabs investigated the new shell more quickly and entered it more quickly, i.e. were more motivated to find and accept a new shell, and this change lasted 24 hours. In experiments with glass prawns, when acetic acid or sodium hydroxide was applied to the animals’ antenna prolonged rubbing was observed. This behaviour was inhibited when local anaesthetic was applied. These experiments suggest that responses to noxious stimuli by decapod crustaceans are more than reflexes and that a feeling of pain may be involved.

Poster presentation: “Humane slaughter of crustaceans”

See p8 of HSA Poster Abstracts

This poster describes the ethical and humane killing of crabs, lobsters, langoustine and other decapods crustacean by electro-stunning. The problem with crustaceans is how to stun an animal that has an exoskeleton and doesn’t have a central nervous system. The solution is to stun the animal partially immersed in salt water, to create good contact between the belly and the base electrode, while the stun electrode makes contact with the back of the shellfish. A 110AC voltage is applied and a typical stun current of 4-8 A flows through the animal which is rendered unconscious in less than half a second until prolonged application of the current kills it. A current duration of 5s kills lobsters and langoustines while 10s is needed to kill crabs.

Two (“Crustastun”) machines are commercially available for doing this – a countertop stunner for restaurants and retailers and a batch stunner for shellfish processors. Electro-stunning of crustaceans also brings improved eating quality benefits and can prolong shelf-life.

Presentations on the welfare of farmed fish

See p4 and p8 of HSA Speaker Abstracts
See pages 5, 6, 16, 20, 23, 30 and 31 of HSA Poster Abstracts
See p64 of UFAW Poster Abstracts

A wide range of presentations relating to the welfare of farmed fish was also presented.

Presentation of the “2011 Humane Slaughter Association Award”

This award was presented to joint winners for their work in the development of humane slaughter technology for farmed fish:

  • Jeff Lines of Silsoe Livestock Systems for his research into electrical methods for humane stunning and killing
  • John Ace-Hopkins of Ace Aquatec Limited for taking up this research in the development of commercial humane stunning and killing equipment.

James Kirkwood, HSA Chief Executive and Scientific Director, said
“Before ten years ago there was no way to humanely kill farmed fish en masse – they died slowly through suffocation when harvested from the water. This welfare benefit affects millions of fish. The development of this technology is a huge step forward and the HSA was very pleased to make these awards to Jeff Lines and John Ace-Hopkins.”

Ace Aquatec produces commercial stunning equipment for trout, salmon, seabass, seabream, cod, halibut and turbot.