Eroding the population spatial structure of harvested marine fishes: Theory, consequences, and evidence

Background/Question/Methods

Populations are heterogeneously distributed over space, giving rise to population spatial structure. Commercial fisheries often act in ways that erode the spatial structures of harvested populations. However, management practices do not act to monitor and preserve population spatial structure. Our objective is to synthesize the interacting factors that influence the formation, maintenance and erosion of spatial structure in marine fish populations, and to examine the consequences of such erosion at population and community levels. We highlight three levels of population aggregation that are common in fisheries management scenarios, namely, sympatric, meta- and panmictic populations. Case studies are presented for each level of aggregation. We summarize the factors that link spatial and temporal dynamics in marine populations, and highlight the management and conservation implications of such linkages.

Results/Conclusions

Shifts in spatial structure can have important impacts on marine populations. Changing the spatial structure, for example via localized depletion, alters the demographic and life history trait variations within populations and subjects individuals to both novel environmental conditions and intensified interspecific interactions. Changing spatial structure also affects the resilience and recovery potential of populations following anthropogenic and environmental perturbations. In keeping with general patterns observed in other animal populations, large variations in marine fish population abundance is typically accompanied by equally dramatic changes in spatial structure. Thus, the erosion of the spatial structure is a prelude to further changes in population abundance. We conclude that it is important to conserve the spatial structure of marine fish populations. Further study of fish spatial dynamics will help us to: 1) understand the underlying mechanisms that can lead to rapid alterations in population abundance and shifting community interactions, 2) provide indicators of stock health, and 3) characterize the consequences of changing spatial patterns on population susceptibility to exploitation and environmental variability.