Ontogenetic spatial constraints of sub‐arctic marine fish species

Abstract

AbstractMarine species may respond and adapt to climate change through shifting spatial distributions, but options may be limited by the occupancy of essential habitats which are anchored in space. Limited knowledge of when spatial constraints are most likely to occur in marine fish life cycles has impeded the development of realistic distribution forecasts. In this study, we develop and implement analytical techniques to identify spatial constraints, defined by both the consistency through which a particular geographic area is used year after year, and by the extent of such area with respect to the entire population range. This approach is applied to simulated data and to ten case‐studies including six groundfish species from three subarctic marine systems. Our analyses illustrate that the early phase of the species’ life cycle is more spatially constrained than older life stages. We detected significant species‐specific variability in both the degree to which species are anchored in space throughout their life cycle, and the ontogenetic changes in the geographic association. There is an indication that this variability can be explained by the species life history strategy, highlighting the need to extend similar analyses to other species and regions. The presence of ontogenetic spatial constraints, particularly during early life stages, indicates restrictions exist to changes in spatial distribution and questions the assertion that global warming will uniformly result in an increase in abundance and harvest at higher latitudes and decreases at lower latitudes. Our study develops ecological and analytical insights that are critical for accurate projections of species distributions under different climate change scenarios.