Nervous fish don't taste good! The first seminar on "aquatic life and happiness": let the fish die well and the food tastes better

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"if you are good to it, you are good to us!" The first domestic seminar on "Aquatic Animal Welfare and friendly farming" was held at National Taiwan University yesterday (23). Industry officials and NGO organizations were invited to discuss how to implement aquatic animal welfare, the current situation and development of the industry. The participants included multiple identities such as aquaculture end, road operators and consumers, and paid attention to how aquatic animal welfare affected food quality.

Huang Zhiyi, the moderator of the meeting and an associate professor in the Department of Aquaculture at Ocean University, said that when discussing the welfare of aquatic animals, it is not only based on emotional factors and humanitarian demands, but also can be seen from scholars' research and experimental data. if fish are overly urgent during the culture and slaughtering stage, they will constantly struggle, produce more lactic acid, and the pH value will also drop, which will not be conducive to transportation, storage and preservation, and will also worsen the quality of fish meat. The community should discuss together how to develop the aquaculture industry which is healthier and in line with animal welfare, so that peace of mind and quality of fish can be provided.

How does Huang Zhijun (Photography / Lin Meijun), an associate professor in the Department of Aquaculture at Ocean University, know that fish are under pressure? More mucus, retreating, tail clamping

Wu Shumei, a professor in the Department of Aquatic Bioscience at Chiayi University, said that when fish are nervous, from the appearance, the mucus in the epidermis or Gill will become more, the body color will begin to change, and there will also be withdrawal and tail clamping. "the increase of mucus is to prevent external substances from entering the body, but a lot of mucus is not good for you and will make the Gill filaments stick together, so fish will not do this for no reason. This is what it has to do in the face of environmental changes, using behavior to protect itself. "

In addition, when the fish is nervous, in order to respond to external conditions, the endocrine will change, and the blood sugar will increase and accelerate the energy metabolism, so that it will have more strength; but then the immunity will decline, and then the growth will be inhibited and the fecundity will decline. "when the fish is in an emergency, there will be a lot of responses to physical regulation, but this must also pay a price, and its energy will be consumed."

When fish are pressed, the endocrine changes, blood sugar increases, energy metabolism accelerates, immunity decreases, and growth is suppressed. (from Wu Shumei's briefing)

When the fish is nervous, it can be seen from the appearance that the mucus in the epidermis or Gill will become more, the body color will change, and there will be retreating and tail-clamping behavior. (from Wu Shumei's briefing) Wu Shumei: to understand the needs of fish, find out the suitable operation suggestions.

Wu Shu-mei says that in the experiment, the various reactions of fish can be accurately known through the equipment, "but in the market and in the farm, do people have any consciousness that 'fish are nervous'? Can you tell? " Therefore, she pointed out that people should care about fish, know the environment that fish need, and cooperate with it, so as not to change the living environment of fish as much as possible.

For example, the use of rapid cooling (instant temperature change) of "ice paralysis" may not be a good way to calm down. She also added that the physiological characteristics and environmental needs of different fish species are different, and researchers and operators need to understand the needs of various fish species before they can put forward suggestions for suitable breeding operations.

Aquatic animal welfare has a close impact on food quality.

In the part of terrestrial animals, many studies have pointed out that the way animals are treated is closely related to food quality, and Xiao Xinyi, an associate professor in the Department of Food Science at Ocean University, has further explained the relationship between aquatic animal welfare and aquatic food quality.

Fish will enter the period of rigor after death (Note 1), that is, the muscle loses its stretchability or elasticity. Xiao Xinyi pointed out that "rigor" is an important criterion. In a crowded environment, the rigidity of fish after death is faster, and the pH value decreases faster than that in an uncrowded environment, so the less the fish struggles before death, the better. As soon as it is caught, it is best to slaughter and enter the cold chain. After all, making fish more urgent is less conducive to transportation, storage and preservation. "many consumers will have the myth that 'fish are not fresh when frozen and should be chosen to move when buying fish.' in fact, fish die more slowly, which will lead to the formation of lactic acid and the decline of pH value." it makes it faster to enter rigidity, and all these have to be communicated again. "

The changes of pH (pH), ATP (adenosine triphosphate) and CrP (phosphocreatine) in the body of fish after death. (from Xiao Xinyi's briefing)

In addition, in terms of culture methods and slaughtering methods, she suggested that suitable and clean feed should be selected to keep the water quality clean, so as to avoid fish disease and eliminate the problem of declining production or poor quality of fish meat. The culture density should not be too high, and she suggested that natural extracts (such as "one root" extract) could be used to enhance the anti-urgency ability of fish, hoping to take into account various considerations such as production demand, environmental resources and animal welfare.

Mechanical percussion is a better way of slaughtering, but it depends on the training ability of the executor.

Hsiao Hsin-Yi explains that the use of "asphyxiation,"CO2 anesthesia," and "electric shock" during slaughtering will make fish struggle constantly, producing more lactic acid and pH. "this will make the texture of fish softer, and it will easily break up when handling fish fillets, thus affecting the quality, which consumers generally don't like."

Therefore, in terms of consumers' requirements for the quality of fish, "mechanical percussion" is the best way to slaughter, which can not only make the fish stiff later after death, but also make the fish have a higher water content. However, only manual execution depends on the executor's ability, training, and physical and mental state, and the use of automation may limit fish of different sizes, making it more difficult to apply to general small fish.

Xiao Xinyi stressed that aquatic animal welfare must start with breeding, because better breeding and slaughtering benefits can help maintain the quality of aquatic products, and increasing aquatic animal welfare will increase costs, but according to a survey of Norwegian consumers, most consumers are still willing to pay more for these products that take into account animal welfare and better quality.