Ontogenetic diet shifts are an important component of the early life history of many fishes. Successfully shifting diets affects not only individuals but also populations and communities. We experimentally quantified prey selection and feeding behavior of age‐0 yellow perch Perca flavescens to determine the sizes at which diet shifts occur and identify potential mechanisms driving these shifts. Yellow perch were provided three prey types (zooplankton, benthic invertebrates, and fish) at high‐ and low‐density combinations. Small yellow perch (20 mm total length [TL]) positively selected zooplankton, but intermediate‐sized fish (40 and 60 mm TL) shifted to benthic invertebrates. At 80 mm TL, yellow perch positively selected benthic invertebrate and fish prey, indicating the onset of piscivory. Relative densities of prey items did not influence prey selection patterns. Diet shifts from zooplankton to benthic invertebrates to fish prey were supported by an increased energetic gain and decreased foraging costs for each prey type as age‐0 yellow perch size increased. Quantifying prey selection and foraging behavior under various prey densities can be used to better understand mechanisms governing ontogenetic diet shifts in fishes.
Effective management of endangered or threatened wildlife requires an understanding of how foraging habitats are used by those populations. Molecular diet analysis of fecal samples offers a cost-effective and non-invasive method to investigate how diets of wild populations vary with respect to spatial and temporal factors. For the federally endangered Indiana bat (Myotis sodalis), documenting its preferred food sources can provide critical information to promote effective conservation of this federally endangered species. Using cytochrome oxidase I amplicon sequence data from Indiana bat guano samples collected at two roosting areas in Cypress Creek National Wildlife Refuge, we found that dipteran taxa (i.e., flies) associated with riparian habitats were the most frequently detected taxon and represented the majority of the sequence diversity among the arthropods sampled. A select few arthropods from other taxa—especially spiders—are also likely important to Indiana bat diets in this refuge. A supervised learning analysis of diet components suggest only a small fraction of the frequently detected taxa are important contributors to spatial and temporal variation. Overall, these data depict the Indiana bat as a generalist consumer whose diet includes some prey items associated with particular seasonal or spatial components, along with other taxa repeatedly consumed throughout the entire foraging season. These molecular diet analyses suggest that protecting foraging resources specifically associated with the riparian habitat of Cypress Creek National Wildlife Refuge is essential to promote effective Indiana bat conservation.
The success of trap-and-transfer operations is influenced by the ability to quickly collect target fish and transport them to a recipient body of water. We compared catch rates of two gear types (modified fyke nets and cloverleaf traps with and without light attractants) to determine the most effective capture method for harvesting small yellow perch Perca flavescens (age Ͻ 2) and reducing stress to transferred fish. Fyke nets captured more small yellow perch than cloverleaf traps; however, cloverleaf traps reduced the bycatch of black bullheads Ameiurus melas and large yellow perch (age Ͼ 2) and required less effort to set and retrieve. Unlike fyke nets, cloverleaf traps can also be placed in offshore locations, thereby increasing the number of fishable areas. Light attractants (incandescent lights and cyalume glowsticks) increased the catch rates of yellow perch in cloverleaf traps set at night. Incandescent lights increased catch rates in fyke nets, but cyalume glowsticks were not effective. Cloverleaf traps and light attractants help to improve the success of yellow perch collection methods by increasing daily catch, reducing the effort associated with sorting out bycatch, and reducing stress to transferred fish.
Spawning substrate primarily functions in determining hatching success of yellow perch (PercaJlavescens). In systems lacking adequate, natural spawning substrates, the addition of introduced structures may enhance yellow perch survival. We quantified the effects of introduced conifer tree reef location, age, and type on yellow perch egg deposition to determine which factors influence yellow perch use. Yellow perch preferred to spawn on trees in inshore locations compared to trees in offshore locations. Spawning occurred on both short needle (spruce Picea sp./fir Abies sp.) and long needle (pine Pinus sp.) conifer trees in both wetlands; however, more egg masses were found on the short-needle spruce trees. Newly introduced and trees from the previous year received similar use in inshore locations. Tree reefs were effective for the two years of this study; however, reef longevity beyond two years should be examined.
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