Degree of aquatic ecosystem fragmentation predicts population characteristics of gray snapper (Lutjanus griseus) in Caribbean tidal creeks

Abstract

Ecosystem fragmentation is one of the most damaging anthropogenic impacts to aquatic and terrestrial ecosystems worldwide. In this study, we analyzed population-level characteristics of a resilient top predator, the gray snapper (Lutjanus griseus), across a gradient of fragmentation in Bahamian tidal creeks. Analysis of hydrologic connectivity (the inverse of fragmentation) and site-specific population parameters revealed that varying degrees of connectivity translated into predictable characteristics in fish populations. Less-fragmented systems produced fast-growing snapper with high condition factors, whereas more fragmented tidal creeks yielded slow-growing snapper with low condition factors. Underlying reasons for growth rate differences likely originated from structural and functional shifts in tidal creek ecosystems following fragmentation. Such ecosystem-level shifts were reflected by low per-individual volumes of consumed prey, as well as increased parasite infestations. Results indicated that aquatic ecosystem fragmentation may affect long-term fitness and viability of resilient species capable of persisting in fragmented habitats. Our results from estuarine tidal creeks compare well with studies on fragmentation of freshwater streams by dams and suggest that population-level consequences following ecosystem fragmentation may be generalizable between seemingly disparate aquatic environments.