Relative Abundance and Diet of Spiny Softshells (Apalone spinifera) in a Lake Erie Population

Abstract

Populations of the Spiny Softshell (Apalone spinifera) in the Great Lakes are of conservation concern despite being secure elsewhere in their North American range. We examined the relative abundance of Spiny Softshells among the turtle fauna at Presque Isle, a peninsula on the Pennsylvania shoreline of Lake Erie. We also compared male and female diets to determine the presence of invasive Zebra and Quagga Mussels (Dreissena spp.). The Spiny Softshell was the fifth most common of six turtle species captured (2% of captures). in the peninsula’s largest bay there was a significant increase in capture rate and proportion of Spiny Softshell captures in late summer (5% of five species of turtles) compared to early summer (3% of all turtles). Recapture was considerably lower for Spiny Softshells (5%) than for four other turtle species suggesting that either its relative abundance is higher than trapping data indicate or that they are a mobile species with less habitat fidelity than other residents. Prey from fecal samples were quantified using an index of Relative importance (iRi). Males (n = 26) ate primarily unidentified insects (iRi = 59), followed by algal stalks (iRi = 35) and caddisfly larvae (iRi = 4). Females (n = 5) ate primarily algal stalks (iRi = 54), followed by crayfish (iRi = 22) and fish (iRi = 19). only two turtles, one male and one female, passed
Zebra and Quagga Mussels in fecal samples, thus Spiny Softshells do not appear to make significant use of these invasive molluscs.