Going Green? Seasonal changes in resource use and catch rates of small-bodied fishes coincide with timing of a cyanobacterial bloom
Stable isotope analysis of δ15N and δ13C values allow us to interpret the effects of interspecific competition and environmental factors on fishes’ resource use. Saratoga Lake in Wyoming is one of the few locations brook stickleback Culaea inconstans (an invasive species), Iowa darter Etheostoma exile (a species of greatest conservation need), and fathead minnows Pimphales promelas are present. We used stable isotope signatures to investigate the trophic patterns of these species as well as catch rates over time. We sampled Saratoga Lake six times from June through September 2021. Fifteen individuals per species were harvested at each sampling event for stable isotope analysis and the remaining fish were identified, measured, and enumerated. Trends in δ13C data suggest that brook stickleback and fathead minnow exploited pelagic resources while Iowa darter primarily used littoral resources early in the season. However, brook stickleback and fathead minnow switched to use more littoral resources later in the season, coinciding with the timing of a cyanobacterial bloom. Iowa darter catch rate steadily declined over the season while fathead minnow and brook stickleback catch rates did not show directional trends. These results imply that changing habitat conditions and resource availability may potentially increase interspecific competition later in the season, with implications for fish species of greatest conservation need. Furthermore, our findings open the door to further investigation of the effects of cyanobacterial blooms on small-bodied fishes.
PublisherUniversity of Wyoming. Libraries
- Zoology and Physiology - ZOO