Estimating Fish Species Richness across Multiple Watersheds

Michael Paller

doi:10.3390/d10020042

Abstract

Assessing fish species richness at the scale of an entire watershed or multiple watersheds is important when designing conservation areas and maintaining aquatic biodiversity. Estimating biodiversity at this scale requires considering the effects of habitat heterogeneity within and across drainages on the species-area relationship (SAR). I examined the SAR using unusually complete data to assess fish species richness in minimally disturbed watersheds on large public lands in the Sand Hills ecoregion, southeastern United States of America (USA). My objectives were to compare (1) true richness with estimates produced by different species richness estimators and sampling designs and (2) species richness among reservations. Accurate estimates were obtained for five contiguous watersheds (780 km2 total) by using Chao 2 or first-order jackknife estimators, coupled with (1) a stratified design that apportioned sampling effort over 25 sample sites based on major spatial correlates of assemblage composition, including stream size and drainage basin identity and (2) sufficient sampling effort to collect enough individuals to include rare species. The greatest species richness was in streams within a large land holding characterized by greater instream habitat diversity, less disturbed land coverage, more forested land, and closer proximity to source pools than other reservations. Species richness in these streams was within the range observed in high diversity Neotropical and Indomalayan realms.

Highlights

Diversity at the species level is often expressed as species richness—the number of different species in a community, ecosystem, or region
The results suggest that the efficiency of species richness estimation can be maximized by using a sampling design that accounts for key spatial factors that influence species richness, as was originally hypothesized
The species richness of stream fish at this scale is strongly influenced by differences in species composition that are associated with stream reaches of different size, differences in species composition among basins can be significant

Summary

Introduction

Diversity at the species level is often expressed as species richness—the number of different species in a community, ecosystem, or region. Other aspects of species-level biodiversity, such as composition and evenness, are important, number of species is of special interest because of its relevance to conservation biology. This crisis affects most taxonomic groups, and it is especially severe for freshwater fishes that inhabit lotic ecosystems. Many of these fishes are imperiled because of habitat degradation and fragmentation, flow modifications, translocation of species, over-exploitation, and pollution [1,2]. North America enjoys the greatest level of temperate freshwater biodiversity in the world, but about 700 species (nearly 40%) of freshwater or diadromous fish in North America are imperiled [3]

Methods

Results

Discussion

Conclusion