Thesis Title: Investigating fine-scale movement patterns and comparative swimming performance of the newly identified and threatened Rocky Mountain Sculpin (Cottus sp.) across its Canadian distribution
Author: Marie Veillard
Abstract
Cumulative anthropogenic impacts to the riverscape, including hydrologic alteration, have contributed to an escalated number of freshwater fish species at risk in North America. Species dispersal is an important mechanism underlying many ecological processes. Understanding the scale at which species carry out their life history can inform both conservation actions and recovery potential. Our study used the recently-identified Rocky Mountain Sculpin (Cottus sp.), a species federally listed as threatened, to investigate the (1) fine-scale movement potential and (2) comparative swimming ability of adults throughout their restricted Canadian distribution. Rocky Mountain Sculpin are a small-bodied, cryptic benthic species that utilizes interstitial spaces for shelter. To assess the fine-scale movement potential of Rocky Mountain Sculpin, I conducted a mark-recapture study on Lee Creek, Alberta using Passive Integrated Transponder (PIT) and Visible Implant Elastomer (VIE) tags. I assessed the abiotic and biotic factors influencing movement using Boosted Regression Tree models. In this study I found that 89% of sculpins moved less than 30 meters, while a few individuals moved up to 240 meters. Biotic factors indicated sculpins moved from high to low abundances of fish due to intra- and inter- specific competition from congeners and benthic competitors. The most important abiotic factor contributing to movement was abundance of cobble substrate at destination transects. Interestingly, there was a strong interaction between biotic and abiotic components indicating the importance of focusing restoration efforts on both biotic and abiotic factors. To address the second objective, comparative fish swimming performance and recovery potential was assessed in a laboratory on individuals sourced from drastically different hydrologic regimes in Alberta and British Columbia, including the flow augmented, North Milk River. Permutational ANOVAs were used to compare swimming performance between rivers using two aspects of swimming ability: (1) slip velocity, the point at which fish slipped and transitioned into swimming and 2) failure velocity, the point at which fish could no longer hold position against the flow without resting. While we expected swimming ability to be correlated with natal hydrologic regimes, our study found there were no differences in failure or slip velocity between rivers. However, resting oxygen uptake prior to swim tests was significantly higher for fish from the augmented, North Milk River, indicating there may be a physiological response to flow augmentation. Over repeated exercise, fish failure velocity decreased from 7.45 ± 3.10 body lengths per second (BL s-1) in the first test to 6.18 ± 2.56 BL s-1 by the third test suggesting the use of anaerobic metabolism to power swimming performance of this small-bodied species. Linear mixed-effects models developed using body characteristics showed caudal morphology to influence both failure and slip velocities, while body height was negatively correlated to slip velocity, demonstrating morphological selection for benthic living. Taken together, these studies suggest that while large-scale flow augmentation may come at an energetic cost to sculpins, fine-scale developments may be equally as detrimental to this dispersal-limited species. Conservation for this species may then require both fine-scale and regional management.