A method for estimating the instantaneous mortality rate (Z) is presented which was developed from a truncated equation for average length. The model has zero bias at equilibrium, but has no explicit solution for Z so that its solution requires a numerical method.

The ringnet fishery off Davao, southern Philippines, is briefly described. The major species (36%) in the catch is Decapterus kurroides (Pisces, Carangidae), whose growth parameters and mortality rates (natural and fishing) are estimated, based on length-frequency data collected in 1985-1986 and...

The ringnet fishery off Davao, southern Philippines, is briefly described. The major species (36%) in the catch is Decapterus kurroides (Pisces, Carangidae), whose growth parameters and mortality rates (natural and fishing) are estimated, based on length-frequency data collected in 1985-1986 and...

An attempt to fit the von Bertalanffy growth equation to three species of deep sea snappers using the ELEFAN method was unsuccessful, mainly because the fish are slow-growing, long lived species. Problems were also encountered in estimating asymptotic length and Z/K using a Wetherall plot....

Length-frequency data on Saurida elongata and S. undosquamis (Synodontidae) from bottom trawl survey conducted in 1984 in the Southern Gulf of Thailand were analyzed using the Compleat ELEFAN software. The seasonal pattern of recruitment suggests two uneven pulses per year, one stronger than the...

Based on simulated catch data, this contribution shows that standard length-converted catch curves cannot be used for accurately estimating total mortality when growth oscillates seasonally. Some implications for length-based stock assessment methodology are discussed, and the need for the...