A Catch-at-Length Analysis that Incorporates a Stochastic Model of Growth

Abstract

A length-structured population model, which incorporates von Bertalanffy growth, is used to describe changes in population abundance over time. The model is incorporated into a catch-at-length algorithm that uses a nonlinear least squares approach to estimate relative abundance, fishing mortality, selectivity, and the von Bertalanffy growth parameters L∞ and k. The algorithm is applied to a simulated data set for Pacific cod (Gadus macrocephalus) and to catch data on Pseudotolithus typus and Decapterus russellii. The parameter estimates of Pacific cod obtained from this algorithm were comparable with the values that were originally used to simulate the data. Although the catch data of P. typus did not exhibit the full range of sizes present in the population due to differential vulnerability of the population to the fishery, the estimates of L∞ and k reflect the growth over the entire size range of the population. Other population estimates for P. typus were in agreement with observed biological information. The estimated growth parameters L∞ and k of D. russellii showed some discrepancy with the information available on mature individuals present in this fishery but appeared to adequately represent year 1 growth. The estimated population and exploitation parameters fit the observed catch-at-length. Estimates made with the catch-at-length approach can be improved by using auxiliary information that may be available on abundance, fishing effort, recruitment, and growth.

Incorporating uncertainty into the estimation of biological reference points for a spiny lobster(Panulirus penicillatus)fishery

“…This approach considers the covariance of three parameters in the VBGF (Sullivan et al 1990;Chen & Hunter 2003) in simulating uncertainty of sizeat-age data. The same approach was also applied to simulating parameters (o^ and ß : ) of the W-CL relationship.…”

Modelling of population dynamics of red king crab using Bayesian approach

“…Плотность вероятности величины прироста выражали через гамма-распределение, форма которого, в зависимости от значений параметров, охватывает все возможное многообразие изменений в распределении прироста (Sullivan et al, 1990):…”

“…Пополнение (R) моделируемой популяции камчатского краба американские исследователи описали с помощью двух параметров: 1) количество молодых крабов, пополняющих популяцию в году t, R t и 2) параметр U l , определяющий стохастическое изменение процесса пополнения (Sullivan et al, 1990;Zheng et al, 1995). Пополнение каждой размерной группы R l, t выражалось через уравнение:…”

Tamaños de muestra para estimar la estructura de tallas de las capturas de langostino colorado en la zona centro-norte de Chile: una aproximación a través de remuestreo

“…Para esto, generalmente se utiliza alguna de las siguientes alternativas de modelamiento: (1) modelo edad estructurado (ASA, Age Structrure Analysis, Megrey, 1989), el cual incorpora la dinámica en edades de la población y utiliza (entre otros) datos de composición anual de edades de la captura, (2) modelo edad estructurado, con datos de captura en tallas (A-SCALA, Age Structured Statistical Catch-at-Length, Maunder & Watters, 2003) y (3) modelo basado completamente en tallas (CASA, Catch at Size Análisis; Sullivan et al, 1990;Sullivan, 1992). Las tres aproximaciones utilizan datos de muestreos de tamaños de las capturas comerciales, los cuales son complementados con muestras y análisis de estructuras duras para el caso de los modelos basados completamente en edades (ASA).…”