Diversity–production relationships of fish communities in freshwater stream ecosystems

Abstract

Aim: Ecological relationships between species richness and biomass production are increasingly thought to be pervasive across the globe. Yet, diversity–production relationships have not been explored extensively for freshwater fish communities even though fisheries production provides key services to humans. Our aim was to evaluate the diversity–production relationship of fish communities inhabiting freshwater streams across the Appalachian Mountain range and examine how diversity–production relationships varied across streams possessing different thermal signatures. Location: Our study area included 25 freshwater stream ecosystems spanning from Vermont to North Carolina in the United States. Twenty sites were located in Maryland south to Tennessee and North Carolina, while five additional higher latitude sites were sampled in Massachusetts and Vermont. Methods: We sampled the 25 study streams from June to September 2012 and collected fish population information to calculate biomass, species richness, the Shannon diversity index and annual production for each fish community. Linear mixed effects models were used to analyse the relationship between diversity indices and total community production. We also compared diversity and production relationships across other taxa. Results: Across all streams, community fish production, biomass and P/B ratios ranged from 0.15–6.79 g m−2 y−1, 0.61–0.73 g m−2 and 0.21–1.07 y−1, respectively. Species richness had a significant positive effect (p =.012) on community fish production, while accounting for the thermal signature of the streams as a random effect and other habitat covariates. The Shannon diversity index did not have a significant effect (p =.101) on community production. Main conclusions: The diversity–production relationship observed for stream fish communities was similar to other studies but demonstrated one of the highest slopes. Our results demonstrate that effects of biodiversity resonate to influence the production of fishes; thus, management of fisheries is more closely coupled to biodiversity than previously thought.