Shaken, rattled and rolled: The effects of hatchery-rearing techniques on endogenous cortisol production, stress-related gene expression, growth and survival in larval Lake Sturgeon, Acipenser fulvescens

Abstract

Sturgeon, one of the most endangered families of vertebrates, are of high conservation concern with population restoration efforts worldwide. Sturgeon species are often raised in conservation hatcheries to supplement wild populations with little understanding of effects of hatchery-related stressors on early development. Lake Sturgeon hatcheries deviate from natural conditions by coating adhesive embryos in clay to prevent clumping, embryos are then added to tumbling jars, colloquially referred to as McDonald Jars; a cone or cylinder-shaped container with constant flow, causing the embryos to roll and move throughout the water column. In the wild, Lake Sturgeon embryos adhere to substrate in fast-flowing rivers, where orientation is maintained throughout embryogenesis. In this study, we examined the effects of hatchery early-rearing environment, i.e. the use of tumbling jars, on gene expression, endogenous cortisol production, growth, and survival in larval Lake Sturgeon. We compared pre- and post-hatch tumbled larvae to non-tumbled larvae that were allowed to adhere to substrate throughout embryogenesis. We hypothesized that deviating from natural rearing conditions, with the use of tumbling jars, would result in changes to cortisol production, growth and mortality in post-hatch, tumbled larvae. Endogenous cortisol production was delayed one week for fish in the tumbled treatment (two-factor ANOVA; P < .05) when compared to non-tumbled fish. Tumbled fish were also smaller throughout development, with lasting effects on growth 62 days after hatching (P < .05). The tumbled fish had 23% mortality post-hatch compared to 6% in the non-tumbled group (Cox Proportional-Hazards Model; P < .0001). There were differences in gene expression in early development at specific time points, between the two treatment groups, in StAR and hsp70 (P < .05). The observed developmental effects on endogenous cortisol production and growth in the tumbled embryos could be counterproductive to the goal of producing a hatchery-reared fish that can survive in the wild. As conservation hatcheries aim to release individuals that will supplement and reproduce with wild populations, changes to developmental timing, growth and survival should be avoided. The findings of this study suggest that tumbling jars may not be appropriate in conservation hatcheries for Lake Sturgeon as they may have long-term negative consequences on individual fitness.