Understanding species life-history and ecology for improved conservation and recovery of the threatened Silver Shiner, Notropis photogenis

Conservation and recovery strategies are typically developed with the best available information. However, for many imperilled small-bodied freshwater fish species there is often a lack of basic information available on species life-history and ecology, which limits the ability to assess threats and develop comprehensive conservation actions. One species with a paucity of information pertaining to its life-history and ecology is Silver Shiner, Notropis photogenis, a small-bodied freshwater fish species listed as Threatened under Canada’s Species at Risk Act. The goal of this thesis was to provide an in-depth examination of several life-history traits and ecological parameters of Silver Shiner, to better inform conservation and recovery efforts for the species. To achieve this goal, Silver Shiner were collected from Sixteen Mile Creek, Oakville, Ontario, Canada during 2017-2019 and studies were conducted on the growth, survival, fecundity, spawning phenology, thermal occupancy, and diet of the species. Chapter 2 determined that the probable maximum age of Silver Shiner is four years of age. Moreover, the species experienced altered growth and increased adult mortality when occupying urban (0.71 ± 0.05, average mortality ± standard error) compared to non-urban (0.61 ± 0.06) reaches of Sixteen Mile Creek. In chapter 3, logistic regression models were developed that predict spawning phenology in relation to a cumulative thermal cue and indicated a 50% probability that the population initiated and ceased spawning when cumulative growing degrees > 5oC reached 68 °C•days and 368 °C•days, respectively. These models can be used to understand the impact of alterations in the thermal regime on spawn timing. In chapter 4, the first fecundity estimates for Silver Shiner in Canada were provided, ranging from 311-2768 eggs, and previously undocumented parasite infections were observed and quantified during the reproductive period. Chapter 5 developed a species-specific otolith thermometry equation that facilitates future examinations into the thermal occupancy of the species. In Chapter 6, the diet of Silver Shiner was quantified. The species was found to exhibit a generalist diet and consume a wide range of aquatic and terrestrial prey. Based on stomach contents Silver Shiner consumed more terrestrial prey in fall (41.53 ± 32.35 %, average ± standard deviation) compared to summer (20.45 ± 20.45) and exploited more terrestrial prey at reaches with intact riparian vegetation. \nOverall, the project highlighted urbanization as an important threat, with knowledge of the extent and type of urbanization effects as necessary for better ecological understanding of Silver Shiner. The project also provided an assessment of the potential implications of alterations in the thermal regime on the reproductive dynamics of Silver Shiner. Moreover, results most notably point to the importance of intact riparian habitat for the species. Together, the thesis chapters provide valuable information on the life-history and ecology of Silver Shiner that will facilitate the development of more comprehensive, well-informed conservation and recovery action for the species in Canada.

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