UBC Theses and Dissertations

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UBC Theses and Dissertations

Early life history interactions of White Sturgeon (Acipenser transmontanus) with substrates and predaceous invertebrates Fisher, Jennifer


White Sturgeon (Acipenser transmontanus) are from an ancient lineage and many of their populations are listed as endangered. Recruitment failure, a general term for a low or a lack of survival to sexual maturity, is the primary contributor to this endangerment. In the Nechako River of British Columbia, White Sturgeon embryos and yolk sac larvae are not surviving past their first month of life, despite successful spawning events taking place every year. Changes in benthic sediment composition because of flow regulation appear the likely cause of this lack of early life history success. However, it remains uncertain precisely in what way which these events have impacted these early life stages, and what the most important factors are for survival in the first month of life of White Sturgeon. Few studies have examined yolk sac larvae (YSL), and even fewer have studied embryos. No studies have thus far examined the interaction between predaceous stonefly nymphs and early life stage White Sturgeon, despite them being found in the same environments. I investigated how different substrate sizes act in conjunction with invertebrate predators to influence the early life history success of White Sturgeon embryos and larvae. I also tested how sand-coating impacts embryos. I discuss three experiments, each addressing different aspects of these interactions. I found no evidence that predatory stonefly nymphs consume White Sturgeon embryos, nor that their presence and sand coating are good predictors of embryo survival to hatch. However, I did find that there was a significant effect of invertebrate presence on hatch timing, shifting hatch timing slightly later. I found that the condition factor of YSL reared over sand was significantly lower than that of YSL reared over coarse gravel. However, substrate size did not influence the vulnerability of YSL to predation by predatory stonefly nymphs. I also found that substrate size had a significant impact on time to emergence for larvae, but that invertebrate presence did not. Overall, I found that predatory stonefly nymphs did not appear to prey White Sturgeon embryos, that they lowered survivorship of larvae, and that coarser substrate led to increased condition factor.

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