The Effect of Submersed Aquatic Vegetation on Invertebrates Important in Diets of Juvenile Largemouth Bass, Micropterus salmoides

University Of California, Davis ,Matthew J Young,Andrew J Bibian,Andew Sih,California Department Of Water Resources ,J Louise Conrad,Rice University

doi:10.15447/sfews.2018v16iss2art5

University Of California, Davis , Matthew J Young + Show 5 more

Open Access

https://doi.org/10.15447/sfews.2018v16iss2art5

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Abstract

A suite of submersed aquatic vegetation (SAV) species, and especially Brazilian Waterweed (Egeria densa), has proliferated rapidly in California’s Sacramento–San Joaquin Delta. This expansion is concurrent with population declines in native fish species and increases in many non-native fish species, including Largemouth Bass Micropterus salmoides. In this study, we investigated the effect of SAV species composition and E. densa specifically on macroinvertebrate communities and juvenile Largemouth Bass diets. Invertebrate communities differed across sites in the Delta, driven primarily by changes in abundance of the amphipod Hyalella sp., oligochaetes, ostracods, and insect larvae of the family Chironomidae. Juvenile Largemouth Bass consistently consumed SAV-associated invertebrates, and preferentially consumed larger taxa, when available. Gut fullness of juvenile Largemouth Bass was lowest in sites dominated by E. densa, although there was no clear mechanism for this difference. However, SAV species composition had little effect on abundance of Hyalella sp., chironomid larvae, or damselfly naiads, prey items commonly consumed by juvenile Largemouth Bass. Our results suggest that E. densa does not provide a qualitative increase in macroinvertebrate food for fishes compared to other SAV species.

Highlights

We collected fish during the day by boat electrofishing (Smith–Root 18-foot Extra Heavy Duty [EHD] vessel equipped with a 5.0-GeneratorPowered Pulsator [GPP] generator) at a constant 7±1 amps along 300-meter transects consistent with the methodology used by Conrad et al (2016)
Because mono-specific submersed aquatic vegetation (SAV) samples were impossible to identify from the surface, we identified dominant vegetation type— two categories: either E. densa or Other; defined as whether E. densa or a different SAV species had the highest biomass in each sample—in the PERMANOVA analysis
We modeled the abundance of each invertebrate taxon as a function of the presence of individual SAV species using a varying intercept generalized linear mixed model (GLMM), which allows for the incorporation of nested groups related to consistent clusters of data (Zuur et al 2007)

Summary

Methods

Sample Collection and ProcessingWe collected field samples in August 2010 from nine sites (Figure 1). Using existing data (Conrad et al 2016), we selected sites prioritized in order of anticipated juvenile Largemouth Bass presence, by a range of moderate-to-high SAV densities, and by variable SAV species composition at the site level (Table 1). We collected fish during the day by boat electrofishing (Smith–Root 18-foot Extra Heavy Duty [EHD] vessel equipped with a 5.0-GeneratorPowered Pulsator [GPP] generator) at a constant 7±1 amps along 300-meter transects consistent with the methodology used by Conrad et al (2016). These electrofishing transects were adjacent, but not overlapping, our invertebrate and SAV sampling locations.

Results

Discussion

Conclusion