Using Frequency Distributions of Catch per Unit Effort to Measure Fish-Stock Abundance
- 1 September 1983
- journal article
- research article
- Published by Oxford University Press (OUP) in Transactions of the American Fisheries Society
- Vol. 112 (5) , 608-617
- https://doi.org/10.1577/1548-8659(1983)112<608:ufdocp>2.0.co;2
Abstract
Mean catch per unit effort often is used as an index of fish abundance, N. This index is often biased. Frequency distributions of catch per unit effort (C/f) and independent estimates of N from a headboat sport fishery for yellowtail snappers Ocyurus chrysurus off Islamorada, Florida, indicated that mean C/f underestimated changes in N. Frequency distributions of C/f were skewed and fit the negative binomial distribution. Some descriptors of the distributions (median, variance, negative binomial parameter k, and frequency of zero C/f) were systematically related to N. These relationships were used to derive an index of N less biased than mean C/f. The new index, square root of relative frequency of zero C/f, could be applicable to any recreational, scientific, or commercial fishing activity for which C/f distributions are available, skewed, and have fairly high frequencies of zero C/f. Skewness could be due to spatial dispersion of the fish population or to a gradient of skill among fishing units. Received September 28, 1982 Accepted June 3, 1983Keywords
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