Stressed Fish Don't Taste Good: The First Aquatic Animal Welfare Symposium Makes Fish Taste Better When They Die Well
"Being good to them is being good to us!" The first domestic "Aquatic Animal Welfare and Friendly Farming" symposium was held yesterday (the 23rd) at National Taiwan University, inviting industry, government, academia and NGO organizations to discuss how to implement aquatic animal welfare, the current state of the industry and its development. Participants included a diverse range of identities from the farming sector, channel operators and consumers, all paying attention together to how aquatic animal welfare affects food quality.
Huang Chih-yang, associate professor in the Department of Aquaculture at National Taiwan Ocean University and moderator of the conference, said that when discussing aquatic animal welfare, it is not only out of emotional factors and humanitarian appeals; from scholars' research and experimental data it can further be seen that if fish are subjected to excessive stress during the farming and slaughter stages, they will constantly struggle, produce more lactic acid, and their pH value will also drop. None of these are favorable for transport, storage and preservation, and they will also make the fish meat quality worse. Society should discuss together how to move toward a healthier aquatic industry that conforms to animal welfare, so as to supply fish catches that are safe and of good quality.
How do you know a fish is stressed? More mucus, withdrawal, clamped tail
Wu Shu-mei, professor in the Department of Aquatic Biosciences at National Chiayi University, said that when fish are nervous, from their appearance the mucus on the skin or gills will increase, body color will begin to change, and there will also be withdrawal and tail-clamping behavior. "The increase in mucus is to prevent external substances from entering the body, but too much mucus is also not good for itself and will make the gill filaments stick together, so fish do not do this for no reason. This is something it has no choice but to do when facing environmental changes, using behavior to protect itself."
In addition, when fish are nervous, in order to respond to external conditions, their endocrine system will change, blood sugar will also rise, and energy metabolism will accelerate, so that they will have more strength; but afterward immunity will decline, followed by inhibited growth and reduced reproductive capacity. "When fish are coping with stress, many reactions of bodily function regulation will appear, but this also necessarily comes at a cost; their energy will be consumed."
Wu Shu-mei: Empathize with fish needs, find suitable operational recommendations
Wu Shu-mei said that in experiments, instruments can precisely reveal the various reaction changes of fish, "but in the market and on farms, are people aware that 'the fish is nervous'? Can they distinguish it?" Therefore she pointed out that people should empathize with fish, know the environment fish need, and cooperate with it, trying as much as possible not to let the fish's living environment undergo too much change.
For example, "ice-chilling paralysis," which uses rapid temperature reduction (instantly changing temperature), may not be a good calming method. She also added in explanation that different fish species have different physiological traits and environmental needs, and researchers and industry operators need to first understand the needs of various fish species before they can propose suitable rearing and operational recommendations.
Aquatic animal welfare closely affects food quality
In the case of terrestrial animals, many studies currently point out that the way animals are treated is greatly related to food quality, and Hsiao Hsin-yi, associate professor in the Department of Food Science at National Taiwan Ocean University, further explained the relationship between aquatic animal welfare and aquatic food quality.
After fish die they enter rigor mortis (Note 1), that is, the muscles lose extensibility or elasticity. Hsiao Hsin-yi pointed out that "rigor" is an important criterion for judgment. In crowded environments, fish enter rigor faster after death, and the pH value drops more rapidly than in non-crowded environments. Therefore, the less fish struggle before death the better; ideally they should be slaughtered immediately upon capture and enter the cold chain. After all, the more stress fish produce, the more unfavorable it is for transport, storage and preservation. "Many consumers have the myth that 'frozen fish is less fresh, and when buying fish you should choose one that is moving.' In fact, fish that die more slowly will produce lactic acid and have a drop in pH, causing them to enter rigor faster. All of this needs more communication."
In addition, regarding farming methods and slaughter methods, she suggested choosing suitable and clean feed and keeping water quality clean, which can better avoid fish becoming ill and eliminate problems of reduced fish meat yield or poor quality. Farming density should also not be too high. She suggested using natural extracts (such as "yitiao gen" extract) to enhance fish's ability to resist stress, hoping to balance multiple considerations such as production needs, environmental resources and animal welfare.
"Mechanical percussion method" is a better slaughter method, but relies on the operator's training ability
Hsiao Hsin-yi explained that using the "suffocation method," "CO2 anesthesia method" or "electric shock method" during slaughter will all cause fish to constantly struggle and produce more lactic acid and a drop in pH. "This will make the fish meat texture softer, and when processing fillets they easily break apart, affecting quality. Consumers generally do not like this."
Therefore, from the perspective of consumers' requirements for fish meat quality, the "mechanical percussion method" is the best slaughter method, as it allows fish to enter rigor later after death and also allows the fish meat to have a higher water content. The only issue is that when performed manually, it relies on the operator's ability, training and physical and mental state, while adopting automation may be limited by differences in fish size, making it harder to apply to ordinary small fish.
Hsiao Hsin-yi emphasized that aquatic animal welfare must begin from the farming stage, because better welfare in farming and slaughter helps maintain aquatic product quality. Although increasing aquatic animal welfare will raise costs, according to a study surveying Norwegian consumers, most consumers are still willing to pay a bit more for these products that also take animal welfare into account and are of better quality.
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