Investigating spatial variation and temperature effects on maturity of female winter flounder (Pseudopleuronectes americanus) using generalized additive models

Abstract

Generalized additive models were used to investigate fine-scale spatial variation in female maturity across the three United States' winter flounder (Pseudopleuronectes americanus) stocks. The effect of temperature on maturity was also investigated. Maturity models explicitly incorporating spatial structure performed better than "traditional" methods incorporating spatial effects by aggregating data according to predefined stock boundaries. Models including temperature explained more of the variability in maturity than those based only on fish size or age but did not improve fit over models incorporating spatial structure. Based on the size-and age-at-maturity estimates from the spatially explicit models, distinct subareas were objectively identified using a spatially constrained clustering algorithm. The results suggested greater variation in size-and age-at-maturity within than between existing stock areas. The approach outlined here provides a method for identifying areas with different vital rates without the need to presume subjective boundaries. Résumé :Des modèles additifs généralisés ont été utilisés pour examiner les variations spatiales fines de la maturité des femelles dans les trois stocks de plie rouge (Pseudopleuronectes americanus) des États-Unis. L'effet de la température sur la maturité a également été examiné. Les modèles de maturité qui intègrent explicitement la structure spatiale donnent de meilleurs résultats que les méthodes « traditionnelles » qui intègrent les effets spatiaux en groupant les données selon des limites de stock prédéfinies. Les modèles intégrant la température expliquent une plus grande part de la variabilité de la maturité que ceux qui ne reposent que sur la taille ou l'âge des poissons, bien qu'ils n'améliorent pas le calage sur les observations par rapport aux modèles intégrant la structure spatiale. À la lumière des estimations de la taille et de l'âge à la maturité obtenues des modèles spatialement explicites, différentes sous-régions ont été délimitées objectivement à l'aide d'un algorithme de groupement intégrant des contraintes spatiales. Les résultats semblent indiquer de plus grandes variations de la taille et de l'âge à la maturité à l'intérieur des régions des stocks existants qu'entre ces différentes régions. L'approche décrite constitue une méthode permettant de cerner des régions présentant différents taux vitaux sans nécessiter la définition préalable de limites subjectives. [Traduit par la Rédaction]

Interannual and Spatial Variability in Maturity of Walleye Pollock Gadus chalcogrammus and Implications for Spawning Stock Biomass Estimates in the Gulf of Alaska

“…We discovered prominent temporal and spatial patterns in maturity of walleye pollock in Shelikof Strait that may impact both our understanding of the biology and management of the species. There have been only a few attempts to evaluate latitudinal gradients in maturity in gadids [ 34 – 37 ] or other species [ 2 , 38 – 40 ], examples of intra-stock spatial variability are rather limited [ 19 , 39 , 41 ]. For instance, both L 50 and length at age of pollock tend to decrease with increasing latitude [ 19 ], consistent with observations of higher growth rates in the southern Bering Sea [ 42 , 43 ].…”

The Reproductive Biology of Female Atlantic Herring in U.S. Waters: Validating Classification Schemes for Assessing the Importance of Spring and Skipped Spawning

“…Given spatial variation in size and age at maturity in fishes, even within a stock (Winton et al. ), obtaining samples from a wide geographic range and in proportion to population densities is recommended. As shown here for Atlantic Herring, perceived variation in maturity can arise due to differential distributions of immature and mature individuals (e.g., as is caused by spawning migrations).…”

“…Other studies have demonstrated the importance of representative sampling of populations for sex and maturity, especially when there is spatial heterogeneity of the population components (e.g., in species with separate juvenile and adult habitats, Gillanders et al 2003;Adams 2017; differential habitat use by sex, Langan et al 2019; or when spawning occurs at specific sites, Lowerre-Barbieri et al 2016). Given spatial variation in size and age at maturity in fishes, even within a stock (Winton et al 2014), obtaining samples from a wide geographic range and in proportion to population densities is recommended. As shown here for Atlantic Herring, perceived variation in maturity can arise due to differential distributions of immature and mature individuals (e.g., as is caused by spawning migrations).…”

A statistical model for monitoring shell disease in inshore lobster fisheries: A case study in Long Island Sound

“…Variable removal was conducted one at a time and the reduced model was refit to the data. Candidate univariate and bivariate terms were kept in the model if they contributed to a lower AIC [ 55 ]. The stepwise model selection procedure was repeated until an optimal model was identified according to the above criteria at each stage (i.e.…”