The effect of struggling
It has long been known that an animal undergoing vigorous exercise has a much more active metabolism than when placid. Consider the effort that is made to ensure that cattle are slaughtered when in a calm state. When animal dies in a hyper state of metabolic activity, there are many more active enzymes and other biological components that adversely affect the subsequent spoilage rate of the slaughtered animal.
The effect of struggling is probably most profound in a fish that is caught by hook and line or gillnet and allowed to thrash in the water for some period of time. The effect is even greater when a fish has been feeding prior to being caught. During the struggling period, the digestive enzyme activity is greatly accelerated in the stomach. Since digestive enzymes in the stomach and viscera do not attack normal healthy live tissue, this effect is found after the fish is landed and stored, usually in ice, either on the vessel or subsequently during transporting or in the processing plant. The dead tissue is the walls of the stomach, intestines, or other organ is now subject to attack by the enzymes. These active materials, such as pepsin, digest all parts of the viscera, eventually perforating the walls and attacking the edible flesh. This effect known as “soft belly”: in the fishing industry, greatly reduces the shelf life of the fish and reduces the yield due to the soft flesh that must be removed during butchering and cleaning.
It should also be pointed out that the cause of more rapid deterioration in “soft belly” fish is not always due to the biochemical reaction of enzymes alone. When the viscera is perforated by poor handling method, bacteria are allowed to get into the body cavity and cause further spoilage due to bacterial action.
If a fish is pulled from water soon after being hook, the effect of struggling is almost eliminated, especially if it is killed when landed and not allowed to thrash on the deck or shore. For this reason, the effect of struggling is much more noticeable in long-lined fish allowed to thrash and die in the water than with troll-caught fish that are landed immediately after being hooked.
The effect of struggling
