Compensation and recovery of feeding guilds in a northwest Atlantic shelf fish community

Abstract

Disturbance of marine ecosystems from fishing has resulted in significant shifts in the composition of fish communities. Such changes can result in shifts in dominance of functional (trophic) guilds within communities and the role that guilds play in ecosystem functioning. In partic- ular, studies in coral reef and kelp forest fish communities have demonstrated a low level of func- tional redundancy, yet few studies have examined fish communities from temperate large marine ecosystems. We compared the abundance and composition of feeding guilds (i.e. planktivores, ben- thivores, amphipod-shrimp feeders, crabivores, echinoderm feeders, shrimp-fish feeders, and pisci- vores) on the continental shelf of the northeast US across 4 decades (i.e. 1970s to the present), exam- ining changes in guild structure to determine if: (1) there have been significant changes in the abundance of functional guilds within the fish community, (2) there have been significant changes within guilds, and (3) there are commonalities in responses with studies from other habitats. We found that 5 of the 7 guilds exhibited remarkable stability in abundance over time despite extreme levels of exploitation and shifts in the abundance of individual species. We suggest there are compen- satory mechanisms within those guilds that resulted in, or are an outcome of, their functional role within the shelf fish community. Comparing our results with studies in more spatially discrete habi- tats such as coral reefs or kelp forests suggests that erosion of functionally redundancies may be related to the resolution involved, be it spatial extent of observations, movement patterns of fishes, taxonomic precision of functional role, or variations in the diversity of species interactions within these ecosystems. Regardless, to prevent any potential for erosion of functional roles, we recommend that guild structure be considered as a unit for monitoring and resource management.