Fish community dynamics in a coastal no-take marine protected area compared to a harvested area before and after protection from fishing

An ecosystem's ability to maintain key functions during environmental change is largely determined by its biodiversity. We compared fish species composition, richness, diversity, catch per unit effort (CPUE), and fish size between a 1.5 km(2) no-take marine protected area (MPA) and a nearby fished area on the southern Norwegian coast annually for one decade (2011-2021), including before-protection status. In total, >26 thousand fish representing 31 species were sampled using a beach seine. No significant effect of protection was detected on either species richness, diversity, or evenness. For selected species of small-bodied intermediate predators, there was a significant decline in mean body size in the MPA area compared to the fished area, indicative of a response to protection involving trophic interactions. No significant effect of the MPA was detected on either CPUE or body size of Atlantic cod (Gadus morhua), a top predator mainly captured at the juvenile stage by our sampling. The limited responses seen in this study may be linked to the small size of the MPA compared to the dispersal and movement capabilities of species such as the cod.

Automated summary

The biodiversity of an ecosystem is crucial for maintaining its key functions during environmental change. This study compared fish species composition, richness, diversity, catch per unit effort (CPUE), and fish size between a 1.5 km(2) no-take marine protected area (MPA) and a nearby fished area on the southern Norwegian coast over a decade. The study found no significant effect of protection on species richness, diversity, or evenness. However, there was a significant decline in the mean body size of selected species in the MPA, indicating a response to protection involving trophic interactions. The MPA had no significant effect on the CPUE or body size of Atlantic cod, suggesting that the small size of the MPA may limit its effectiveness.