How is a family of sedentary marine fishes shaped by its habitats, prey, and predators?

Publication type: Thesis (Master of Science)
Publisher: The University of British Columbia
Date:  2017
Author:  Clayton G. Manning

Overall, this thesis expands on our ecological understanding of a group of biologically diverse marine fishes by investigating how they are shaped by their habitats, prey, and predators. In my first data chapter, I used the seahorse Hippocampus whitei as a case study for investigating the ecological correlates of syngnathid abundance and distributions. Expanding on research that had looked at how either their habitats, prey, or predators affected their populations, I considered all three components in a single holistic approach.

I investigated these correlations at two scales: among different seagrass beds (200-6000 m apart), and within a single seagrass bed (<100 m in size). I found that habitat, prey, and predator variables all correlated with seahorse density or height distributions to varying extents, depending on the scale of the study. Total predators was negatively associated with seahorse density across seagrass beds, the only ecological variable that was correlated with seahorses across beds. Within seagrass beds, seahorse locations correlated with greater depth, denser seagrass, more prey types, and fewer predators.

In my second data chapter, I reviewed the diets and feeding behaviour of syngnathids, bringing together, summarizing, and providing new insights on a large amount of fragmented information on the topic. I answered three central questions. 1. How do syngnathids eat? 2. How does feeding and diet vary across a morphogically diverse family of fishes? 3. How does feeding and diet vary across a family of fishes that lives in a three-dimensional space? I answered question 1 by summarizing a number of different studies on the morphologies and kinematics of syngnathid feeding events. I answered questions 2 and 3 using a meta-analysis on syngnathid diets found the literature.

Overall, I found there to be a large amount of variation in syngnathid diets that I hypothesize is caused by large differences in prey availability. Of the explained variation, I found their diets were most strongly correlated with their relative snout lengths and gape sizes. These feeding morphologies also had high phylogenetic signal, suggesting that dietary differences across genera were largely explained by how they differed with respect to these morphologies.