Incorporating Spatial Structure in Stock Assessment: Movement Modeling in Marine Fish Population Dynamics

Abstract

Investigations into population structure have been at the forefront of fisheries research for decades, yet it is generally ignored in stock assessment models. As the complex nature of marine population structure has been uncovered, models have attempted to accurately portray it through the development of spatially explicit assessments that allow for movement between subpopulations. Although current tag-integrated movement models are highly complex, many arose from the relatively simple models of Beverton and Holt (1957). This article traces the historical development of these models and compares their features. Originally estimation of movement utilized only tag-recapture models, but now tag-integrated assessment models incorporate several sources of fishery, survey, and tag-recapture information to inform movement estimates. As spatial management measures become more widely used, it is increasingly important that assessment models include the spatial complexities of population structure and patterns of fishery removals, in order for more reliable monitoring of population rebuilding to take place. A generalized metapopulation model is proposed for use in fisheries stock assessment, which allows for adult movement among spatially discrete sub-populations. The input requirements for the model include region-specific catch-at-age, a tag-recapture dataset, and auxiliary information, such as a fishery-independent abundance index.

Crossing the line: migratory and homing behaviors of Atlantic bluefin tuna

“…The productivity and dynamics of marine fish populations are inherently influenced by patterns of movement during the life of an individual (Goethel et al 2011). Species often require and use multiple habitats, ecosystems, or seas to complete their life cycle, and an improved understanding of movement and population connectivity is needed to effectively manage and rebuild harvested stocks.…”

A Lagrangian approach to model movement of migratory species

“…The Lagrangian movement model described in this paper is an alternative to traditional Eulerian approaches commonly used to model the distribution of adult iteroparous fish (Goethel et al 2011;Sippel et al 2015). The Lagrangian approach shown here allows for the explicit consideration of migration hypotheses, such as the cyclic migration between spawning and feeding grounds, and exploration of potential impacts of covariates in shaping migration variability within a population.…”

“…Migration models are diverse in the fisheries literature (Goethel et al 2011) and can be grouped based on two numerical methods used to implement them: Eulerian and Lagrangian models. These terms are originally applied to fluid dynamics but have been used to describe migration modeling for aquatic resources (Kerr and Goethel 2014;Walters and Martell 2004).…”

Introduction to “Space Oddity: Recent Advances Incorporating Spatial Processes in the Fishery Stock Assessment and Management Interface”

“…The importance of incorporating spatial structure into population dynamics models and resultant management decisions for many aquatic species has been widely recognized for more than half a century (e.g., see the spatial models proposed by Beverton and Holt 1957); however, there has historically been a lack of empirical data to adequately support these types of analyses (Goethel et al 2011). Particularly over the last two decades, the expanding field of spatial ecology has demonstrated the importance of spatial population structure for its role in regulating population productivity, which has led to a growing awareness of the need to incorporate spatial processes into the stock assessment-management interface (i.e., the interaction between scientific advice and resulting management actions; see figure 1 in Berger et al 2017).…”