Assessing the ecosystem impact of scallop bottom culture through a community analysis and trophic modelling approach

The Peruvian bay scallop Argopecten purpuratus is a key resource of the Peruvian diving fishery that has long been harvested along the Peruvian and Chilean coastline. In the last decade, Sechura Bay (North Peru) has developed into a hotspot for its cultivation, which represents an important socio-economic activity for the region. Scallops are cultivated on the bottom and may potentially function as ecosystem engineers in the system by providing settling substrate to other organisms in an otherwise soft-bottom habitat. Community analysis (permutational multivariate analysis of variance, similarity percentage analysis and abundance-biomass comparison) was combined with trophic modelling (Ecopath with Ecosim) to compare the current system state with pre-culture conditions, to evaluate the impact of scallop culture on both the benthic community and overall ecosystem functioning. The results suggest the following effects due to the massive culture: (1) a significant change in benthic community composition; (2) an increase in the predator biomass, paralleled by a decrease in the biomass of their competitors; (3) a change in species diversity and maturity; (4) a system increase in size (in terms of biomass and total flows); and (5) a decrease in energy cycling, indicative of the direct impact of scallop culture on the system’s flow structure and functioning. The results suggest that a further expansion of scallop culture may cause the benthic species composition to further shift towards a hard-bottom-associated community, essentially altering the system’s structure and functioning. These results are expected to aid the process of suggesting limits to culture and the ecological carrying capacity of the bay’s system.