Data from: Using survival models to estimate invertebrate prey identification times in a generalist stream fish

Estimates of predator feeding rates are important for understanding trophic dynamics. One common method for quantifying feeding rates in fishes combine mass-based diet data with gastric evacuation times to estimate prey mass consumed per predator. An alternative approach is to estimate rates of prey individuals consumed using prey identification times − the time period over which prey remain identifiable in a predator's stomach. One challenge with the analysis of prey identification times, however, is that the response variable is likely to be censored because the 'true' prey identification time cannot be observed directly. Here, we applied survival analysis that can incorporate censored data to estimate the effects of predator body size, water temperature, and prey characteristics (type, count and body size) on identification times in reticulate sculpin (Cottus perplexus). We focused on seven types of prey that are common in this generalist predator's diet: mayflies (Ephemeroptera), caddisflies (Trichoptera), stoneflies (Plecoptera), flies (Diptera), beetles (Coleoptera), worms (Annelida), and sculpin eggs. An information-theoretic model comparison approach indicated that an accelerated failure-time Weibull model with all five covariates provided the best relative fit to the full dataset. Prey type had a strong effect on prey identification times, with annelid worms having the shortest times (< 1 hr) and caddisflies having the longest times (> 15 hrs). Water temperature decreased prey identification times (7.5% per 1°C increase), whereas prey count (i.e. meal size) increased prey identification times (15.5% per additional prey item). Sculpin body size had a weak negative effect on prey identification times (0.04% per 1 mm increase). Body sizes of some taxa, including mayflies, caddisflies, and stoneflies, increased prey identification times, leading to an interaction between prey type and prey size. Our study highlights the utility of survival analysis to quantify variation in prey identification times in the diets of generalist predators.