Certain Advantages Of Simple Formulation In Fish Studies And Statistics

The growth of fish is an important factor in the useful studies of fish populations. There are several well known methods of comparing growth of fish. Only one will be discussed in this paper. This method uses the formula W; KLn where W is weight in grams, k is a constant, L is length in millimeters, and n is a power, usually near 3. This paper will espouse a variant of the formula, equating W ; KL3. Here, the variable n becomes a constant 3, eliminating the vagaries of n; and the constant k now becomes a variable K changing with length, in order to maintain mathematical validity. K varies with L in this paper although it could be made to vary with Wand to some approximate degree with age. It will be shown that the equation holds regardless of the size of the fish. The advantage of the simplified hyperbolic equation is that it reduces the imput to three variables. So one variable which usually varies with length becomes the sole means of comparing the plumpness and condition of fish. This eliminates the fuzzy mathematical judgment involved when both changes in a constant and a power are involved in comparisons. It will be shown by illustration and example that this concept readily lends itself to simple single setting computer type solutions for K, L or W; and to available tabular solutions in both English and metric systems. Thus, a method and three aids are proposed to decrease the effort and increase the reliability and usefulness in fisheries studies. The world needs protein. Water provides the environment for production of such protein, and fish are a well known and highly acceptable source. Fish may well be the healthiest basic food. There are various yardsticks for measuring fish production, such as money value, tons of fish, and varfous breakdowns by fisheries. Age-weight and weight-length studies have an important bearing on the entire production outlook. Of less importance from a nutritional point of view, but still a significant contributor to food is sport fishing. This use of fisheries resource has an increasing and far reaching stimulus to the economy of the United States. Any useful method or improved tool which is readily accessible to the fishery biologist to reduce his work and improve his effectiveness will also be useful to the fisheries analysts, managers and administration. A modified method which lends itself to such use as an effective and simple tool is the purpose of this paper. It is aimed specifically at the weight-Iength-conditon factor phase.

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