RATIO ESTIMATION OF MORTALITY USING CATCH CURVES

A ratio estimator for calculation of mortality from catch curves is de veloped in which the individual net hauls are treated as samples, as t hey should be, and precision depends on the number of net hauls and th e average number of fish caught per net haul; this permits calculation of the sample sizes necessary to obtain desired levels of precision i n terms of the number of net hauls and mean number of fish per net hau l. The ratio estimator is compared with the Chapman-Robson maximum lik elihood estimator and the least-squares estimator.