Meeting Abstract
Gobies living in oceanic island streams vary dramatically in their patterns of exposure to aquatic predators, both through stages of ontogeny and across species. Following an oceanic larval phase, juveniles of all species arrive in lower stream reaches rich in piscivore predators. On the Island of Hawai’i, some species (Sicyopterus stimpsoni, Awaous stamineus) climb waterfalls to escape the reach of non-climbing predators, but others (Stenogobius hawaiiensis) live their entire lives in predator infested waters. In other island systems, such as La Réunion in the Indian Ocean, climbing gobies (Sicyopterus lagocephalus, Cotylopus acutipinnis) and their potential predators, especially freshwater eels, are present from estuaries to upper reaches. We sought to test how escape performance changed between juveniles and adults of species that did (S. stimpsoni) or did not (S. lagocephalus and C. acutipinnis) escape the predator range, and how escapes varied across adults of species with different degrees of predator exposure. We collected 493 escape response trials among five species using an observation tank and water pulse stimulus, and found differences in escape response both through ontogeny and across species. Juveniles respond more frequently than adults across all species. However, adults from Hawaiian species show higher response frequencies than those from La Réunion, especially when attacks are from caudal and lateral directions. These results show a complex association between exposure to predation selection and escape performance.
