fish disease



In their usual habitat fishes have a natural stock level that is stabilized by new cohorts replacing dying older or diseased fish and by common immigration and emigration. Unfortunately, in today's heavily stocked fisheries new cohorts are rarely seen, unless stocked, thus no replacement is there for dying fish. With more conscious fisheries managers and some may say more obedient, but I would prefer environmentally aware, angles, only a minute percentage of fish now die due too angling induced injuries. So why do we hear of so many huge fish kills across the country? Disease is the biggest problem, inherent in many of the countries well-known and highly stocked angling venues. This disease problem is rarely foreseen and purely accidental.

A short time ago I read two letters in a recent Anglers Mail. These letters were on the subject of the latest high profile fish loss on a reservoir in the midlands. The fisheries manager, whom I know well, was branded incompetent and the fishery was classed as both finished as a force and a waste of time from the outset. This aforementioned fishery is now fishing better than ever and is as popular as anytime in its current life as a match water. I find it irritating that some anglers will not sit back and reflect on the problems and potential ways to solve them. Surely holding 200lbs+ of fish in a keepnet throughout a hot summers day is detrimental to the health of some of the fish involved - so why do some anglers not see this? For example, if a fish is caught five times in one week and held in a keepnet on each occasion will it be in the best of health? This question hardly requires a lot of thought to come to a reasonable conclusion.

This page is dedicated to outlining the causes of disease in fish, with respect to coarse fisheries, the ways they can be detected and the treatments, both curative and preventative, available to fisheries managers. Also current legislation will be discussed.

With respect to the previous discussion, stress, a commonly used term by both scientists and fish farmers, is the initial accelerator for most diseases. Stress is very difficult to quantify. To a fish farmer stress can be induced by grading, harvesting and disease treatments. More aimed at fisheries managers the inducement of stress can be associated with water chemistry, pollution, metabolic rate (chemical causes); handling, transporting, stocking, treating, (procedural causes); temperature, light, sound, low dissolved oxygen (physical causes); population density, confinement, diet, fright (biological causes). As this list shows there are many areas of concern, but the majority only induce acute stress that is quickly overcome. In most cases it is only when fish have been susceptible to chronic stress that long term problems are seen. Most of the above stress inducers are obvious although it is important that anglers are aware that there is a large amount of inducers even when on the bank of a fishery.


Disease Types - Parasitological Bacterial Viral Fungal Nutritional
Treating & Treatments Importing fish & legislation

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