Estimation of abundance of fish populations by capture-recapture experiments |
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Authors: | S Z Rafail |
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Institution: | 1. Institute of Oceanography and Fisheries, Kayed Bey, Alexandria, Egypt (UAR)
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Abstract: | A natural fish population is assumed to be subjected to a number of fishing experiments, during which the captured fish are released after tagging all untagged fish. Assuming that, in thek th sampling survey, the tagged and untagged fish are subjected toP tk andP uk fishing rates, andS tk andS uk survival rates, respectively, the population size can be estimated from an estimate ofP uk $$\begin{gathered} i.e., 1 - P_{uk} = \hfill \\ P_{tk \cdot } \frac{{S_t (k + 1)}}{{S_u (k + 1)}}\frac{\begin{gathered} Number of fish captured for the first time in \hfill \\ the (k + 1)^{th} survey plus fish belonging to this \hfill \\ group captured later \hfill \\ \end{gathered} }{\begin{gathered} Number of fish captured for the first time in \hfill \\ the k^{th} and captured again in the (k + 1)^{th} \hfill \\ \exp eriment plus fish belonging to this group \hfill \\ which are captured later \hfill \\ \end{gathered} } \hfill \\ \end{gathered}$$ All terms of the right hand side of the above equation are provided by capture-recapture experiments, except the survival rate of untagged fish which may be obtained by other information. This estimate of fishing rate of untagged fish is free from type (A) errors. |
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