Meeting Abstract

3.3  Sunday, Jan. 4  Predator-induced Selection on Body Shape in Waterfall-climbing Gobiid Fish from Hawai'i BLOB, R.W.**; KAWANO, S.M.; MAIE, T.; CEDIEL, R.A.; PTACEK, M.B.; BRIDGES, W.C.; SCHOENFUSS, H.L.; Clemson Univ.; Clemson Univ.; Clemson Univ.; St. Cloud State Univ.; Clemson Univ.; Clemson Univ.; St. Cloud State Univ. rblob@clemson.edu

Amphidromous gobiid fishes of the Hawaiian Islands face two major functional demands as their juveniles return to freshwater after months of oceanic development: (1) avoiding predators in lower stream reaches, and (2) climbing tall waterfalls to reach adult habitats using ventral suckers. Different body shapes should be best suited to meet each of these demands, with a deep, taller body improving predator avoidance and a lower profile body improving climbing success. Adult fish from islands where different selection pressures predominate show such differences: Sicyopterus stimpsoni from Kauai have deeper bodies, correlated with the longer, predator-filled estuaries that must be traversed before reaching adult habitats, whereas S. stimpsoni from the Big Island have bodies lower in height, which should reduce drag in the waterfalls that must be scaled shortly after juveniles enter streams. Our previous selection experiments showed that morphological selection induced by waterfall climbing likely contributes to the shape differences seen between goby subpopulations from different Hawaiian Islands. Here, we evaluate the potential selective pressures of predation on Hawaiian gobies by exposing groups of juvenile S. stimpsoni to the native predatory fish Eleotris sandwicensis and comparing the body shapes of survivors to those of control groups. Predation imposed differing and often opposing patterns of selection on body shape than waterfall climbing. For example, predation survivors had lower fineness ratios than control fish, indicating greater body depth for a given length (as predicted). Thus, shape differences between goby subpopulations may also be strongly influenced by predators. NSF IOS-0817794, IOS-0817911.