Date of Award
December 2019
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biological Sciences
Committee Member
Richard W Blob
Committee Member
Richard W Blob
Committee Member
Heiko L Schoenfuss
Committee Member
Kara E Powder
Committee Member
Michael W Sears
Committee Member
Michael J Childress
Abstract
Animals engage in migrations for diverse reasons and over a variety of time periods. Moving between habitats introduces novel challenges that migrating organisms must overcome in order to reach their intended destination. Such challenges include attaining resources required for survival while also avoiding becoming a resource for other organisms. Another challenge is that environmental structure can act as a barrier between habitats. Amphidromous goby fishes provide an advantageous system in which to study several aspects of migration-related performance. As adults, these fishes live and lay eggs in freshwater streams. Upon hatching, larvae are swept downstream to the ocean. At the end of a marine development and dispersal period, young fish are attracted towards stream mouths by large plumes of freshwater that are output by frequent flash floods on the islands where these fish are found. Following a flood, fish migrate upstream to adult habitats in large migration pulses that occur over a period of several days. Along their journey, migrating gobies must evade piscivorous predators as they migrate upstream. Some species of amphidromous goby also can climb waterfalls, which allows them to escape predation by predators that are unable to climb. Thus, measurements of predator evasion and waterfall climbing allow migration-related performance among groups of these fishes to be compared and quantified. In this project, I apply an integrative perspective to examine how aspects of organismal morphology, behavior, and performance interact with variation in natural environments. First, I tested how escape response changes through ontogeny and varies across different predator regimes using fishes from the islands of Hawai’i and La Réunion. I expected fish that were exposed to higher selection pressures would respond more frequently, have higher escape performance, and have morphologies that aid in thrust production. While differences between groups in performance and morphology generally matched our prediction, I found that fish from populations exposed to higher risks of predation responded less frequently than fish in habitats with lower predation pressure. These results suggest that these fish may use a combination of predator-avoidance strategies that do not solely rely on kinematic predator evasion. To further explore how the environment could influence migration-related performance, I compared escape and climbing performance among juvenile Sicyopterus stimpsoni from the islands of Kaua’i and Hawai’i in the Hawaiian archipelago. These islands differ in stream steepness with Kaua’i having long stretches before waterfalls and Hawai’i having waterfalls close to stream mouths. Fish on Kaua’i are exposed to predators for a longer period and have previously been shown to have morphologies that may aid in thrust production, whereas fish from Hawai’i have body shapes that could help reduce drag during waterfall climbing. To test if these differences in morphology match differences in performance, I compared escape and climbing performance among these two island populations. Fish from Hawai’i had superior climbing performance in some of our performance measures, but Hawai’i fish also showed better escape performance. Again, this suggests that fish exposed to predators for longer periods may use a combination of predator avoidance strategies. Finally, I tested to see if morphology, performance, or behavior change predictably over the course of a migration pulse. I found limited support that migration-related performance changes between early-arriving and late-arriving migrants. However, I did find that more fish attempted to climb within the first five days following a flood. This link between migration timing and behavior could aid in conservation efforts by informing management officials of the most critical time periods of migration for these fish. Additionally, incorporating the effects of migration timing with migration behavior could lead to a better understanding of evolutionary strategies that allow for such a diverse group of morphologies and behaviors in the upstream populations of these fishes. Together these studies highlight the importance of incorporating environmentally relevant data into studies of performance and morphology.
Recommended Citation
Diamond, Kelly Marie, "Functional Morphology and Environmental Impacts on Migration-Relevant Performance Measures in Amphidromous Goby Fishes" (2019). All Dissertations. 2492.
https://tigerprints.clemson.edu/all_dissertations/2492