TY - JOUR
TI - Using continuation-ratio logits to analyze the variation of the age composition of fish catches
LA - eng
AU - Kvist, Trine
AU - Gislason, Henrik
AU - Thyregod, Poul
JF - Journal of Applied Statistics
VL - 27
IS - 3
SP - 303
EP - 319
PY - 2000
SN - 13600532, 02664763
AB - Major sources of information for the estimation of the size of the fish stocks and the rate of their exploitation are samples from which the age composition of catches may be determined However, the age composition in the catches often varies as a result of several factors. Stratification of the sampling is desirable, because it leads to better estimates of the age composition, and the corresponding variances and covariances. The analysis is impeded by the fact that the response is ordered categorical. This paper introduces an easily applicable method to analyze such data. The method combines continuation- ratio logits and the theory for generalized linear mixed models. Continuation-ratio logits are designed far ordered multinomial response and have the feature that the associated log-likelihood splits into separate terms for each category levels, Thus, generalized linear mixed models can be applied separately to each level of the logits. The method is illustrated by the analysis of age-composition data collected from the Danish sandeel fishery in the North Sea in 1993. The significance of possible sources of variation is evaluated, and formulae for estimating the proportions of each age group and their variance-covariance matrix are derived
ER -