Time of Death: Modeling Time-varying Natural Mortality in Fish Populations

Phil Ganz
University of Alaska Fairbanks, Estados Unidos

Esta charla será en inglés. Se están realizando las gestiones para contar con traducción simultánea, pero aquello dependerá de la cantidad de inscritos interesados en tal servicio.

Assessing and predicting the abundance of fish populations often involves applying highly non-linear models while making necessary simplifying assumptions about the given population. Natural mortality (M) is a notoriously difficult parameter to estimate within these models, but it is also one of the most important to obtain an accurate assessment. Due to the paucity of data to inform estimates of natural mortality, the simplifying assumption commonly made is that it remains constant over age and time. Furthermore, this parameter is often fixed rather than being estimated within these models. There has always been, especially in recent years, an interest in whether these are simplifying assumptions we can live with, or whether methods exist that will result in robust estimates of natural mortality that accurately capture the change that one would expect over age and time. In this talk, we present an overview of how natural mortality typically fits into the statistical catch-at-age models used in fisheries stock assessment, and what methods have been proposed to reach time-varying estimates of this key parameter. Finally, we present preliminary results of a simulation analysis of estimating time-varying natural mortality in the commercially important Gulf of Alaska sablefish (Anoplopoma fimbria).

Descargar presentación


Phil Ganz es actualmente estudiante de Magister en el Juneau Center de la University of Alaska Fairbanks. Previamente, trabajó como observador científico en el Pacífico Norte, recopilando datos abordo de embarcaciones pesqueras comerciales en el Golfo de Alaska y en el Mar de Bering. Agotado de sólo contar peces buscó cómo poder utilizar los datos obtenidos en la gestión sustentable de pesquerías.  Por esa razón su actual área de estudio es la evaluación pesquera. Su tema de tesis es la Estimabilidad de la mortalidad natural variante en el tiempo en especies demersales.