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The Statisticaal Analysis of Creel‐Census Data
Author(s) -
Mottley Charles M.
Publication year - 1949
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1946)76[290:tsaocd]2.0.co;2
Subject(s) - salvelinus , salmo , fishing , statistics , catch per unit effort , fishery , trout , population , rainbow trout , fish <actinopterygii> , mathematics , census , biology , demography , sociology
An analysis of the yield of brook trout (Salvelinus fontinalis) and rainbow trout (Salmo gairdnerii) per unit of fishing effort at Furnace Brook, Vermont, shows how modern statistical methods can be utilized to determine the significance of changes in the relative abundance of animal populations. The data cover the 5 years from 1936 to 1940 and the analysis of covariance employed shows that there was a significant decrease in the catch per unit of effort in 1939 which was attributed to the effects of severe floods caused by the hurricane in September of the previous year. This method of analysis, although useful for supplying a measure of relative abundance, fails to provide an estimate of the actual stock on hand. A method of estimating the total population based on the proportion of fish maturing and the number of mature fish counted in the spawning run is presented. A new method for estimating the size of animal populations from data on catch and effort has recently been developed by DeLury. When certain assumptions are made, the following relations hold:log C(t) = log (kN(O))—kE(t),where C(t) is the catch per unit of effort for a given time interval (t), E(t) is the total effort expended during the time interval (O, t), N(O) is the number of individuals at t=O, and, k is a constant describing the rate at which the catch per unit of effort decreases as the effort accumulates. The writer has developed a similar method, which would be much easier for biologists to use, based on the following equation:C(t) = kN(O) − kK(t),where K(t) is the total catch accumulated during the time interval (O, t), and k is a constant describing the rate at which the catch per unit of effort decreases as the catch accumulates. Data from the rainbow trout fishery at Paul Lake, British Columbia, obtained in 1932, show that both methods of estimation yield approximately the same result. The second method is suggested as an aid for fishery managers who wish to determine the size of their fish stocks. It requires that records be obtained concerning the catch and the fishing effort throughout the fishing season and that the proportion of the different age groups in the catch be determined. If sampling is used, then representative sampling methods are required. An example is given to show how the method may be used by fishery managers.