Gastric Lavage Shows Promise as a Non-Lethal Diet Extraction Method for Darters (Etheostomatinae)

There are many levels of the aquatic food web that are not well understood due to a lack of knowledge of trophic interactions (i.e., diet data). This data gap is especially prevalent with small fishes such as darters (Etheostomatinae), since collection of diet data is fatally invasive. This poses a problem as many darters are species of conservation concern. Alternative methods need to be explored for future diet studies on darters. Our study explored small-scale gastric lavage on darters as an alternative method of collecting diet data for these species. A total of four species were used to test gastric-lavage methodology: Banded Darter ( Etheostoma zonale ; BND), Fantail Darter ( E. flabellare ; FTD), Greenside Darter ( E. blennioides ; GSD), and Redfin Darter ( E. whipplei ; RFD). We employed gastric lavage methods on darters and assessed its efficiency and mortality. Lavage efficiency was determined by comparing lavaged diet items to diet items retained in the gut (including entire digestive tract), and we assessed short-term mortality in the field during a monitoring period following the gastric lavage of each fish. In total we captured and performed lavage on 128 individuals (GSD = 34, RFD = 50, FTD = 24, and BND = 19) of which a subset was used for validation. Short-term mortality rates were relatively low for all species except for Banded Darter (GSD = 3.0%, RFD = 8.0%, FTD = 12.5%, BND = 30%). The data outlined in this study provided the foundation for gastric lavage to be applied in future studies on darter diets, which can further our knowledge of the ecology for this highly diverse and important species group.