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 particular, studies in coral reef and kelp forest fish communities have demonstrated a low level of functional 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, benthivores, amphipod -shrimp feeders, crabivores, echinoderm feeders, shrimp-fish feeders, and piscivores) on the continental shelf of the northeast US across 4 decades (i.e. 1970s to the present), examining 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 compensatory 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 habitats 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.

Using an aggregate production simulation model with ecological interactions to explore effects of fishing and climate on a fish community

“…Finally, small pelagics were least affected by harvest (h < 0.2), due to a combination of having the highest growth rate among the 3 groups, and because of the predatory release as groundfish and elasmobranch biomass declined. These results are similar to those seen in previous studies which showed compensatory dynamics in the NEUS LME (Fogarty & Murawski 1998, Auster & Link 2009.…”

“…It is also important to be careful in choosing the component species of each aggregate group, as a group with widely varying growth rates or other characteristics can create issues of interpretation in the results. While we maintain that it is likely the group as a whole would react with relative stability, the individual species within that group might not do so (see Auster & Link 2009). Other implications from our One of the strengths of our approach is that models like AGG-PROD can elucidate the effects of the triad of drivers on biological reference points (BRPs).…”

“…ASP models can incorporate stochasticity, trophic interactions, and environmental and climate forcing relatively simply and easily (Clark et al 2003, Rose 2004, Jacobson et al 2005, Keyl & Wolff 2008. ASP models capitalize on the stability of aggregate groupings that, although dynamic, are nevertheless less variable than those commonly observed for their component species , Auster & Link 2009). Finally, ASPs produce outputs that are widely used in fisheries management and do not require additional familiarization for managers.…”

Assessing the effects of a trawling ban on diet and trophic level of hake, <i>Merluccius merluccius</i>, in the southern Tyrrhenian Sea

“…In the Mediterranean, feeding guilds were successfully used to investigate the trophic patterns of different ecosystems (Cartes et al 2002), and used in the continental shelf of the NW Atlantic to assess functional changes in the food web structure (Auster and Link 2009). Generally, the interpretation of data grouped in categories has the main objective of reducing complexity and identifying general patterns.…”

“…Grouping species on the base of ecological categories is a procedure widely used for a better understanding of functional processes in natural systems (Root 1967, Hajisamae 2003, Koslow 1997, Cartes et al 2002, Auster and Link 2009). In the Mediterranean, feeding guilds were successfully used to investigate the trophic patterns of different ecosystems (Cartes et al 2002), and used in the continental shelf of the NW Atlantic to assess functional changes in the food web structure (Auster and Link 2009).…”