Mid-Columbia Sturgeon Incubation and Rearing Study

Author: M.J. Parsley, E. Kofoot, T.J. Blubaugh

The CLBMON-27 monitoring program was initiated in 2009 and was carried out over three years ending in 2012. The primary objectives of this study were to investigate aspects of the relationship between thermal regime and early life history survival and recruitment. This laboratory study should fill biological information gaps that currently hinder conservation planning for white sturgeon in the Columbia River. While it is being conducted under the auspices of the Columbia River Water Use Plan and funded by BC Hydro, the work is relevant to other populations where the thermal regimes have been altered by hydropower development and power generation. The fundamental management questions to be addressed through this study are: 1) What is the relative success (as displayed by developmental condition, growth and survival) of early life stage white sturgeon reared in the laboratory under different temperature regimes, and what is the magnitude of the effect attributable to temperature? 2) Assuming that the early life stage success of white sturgeon is influenced by the thermal regime, what life stage is most affected (or constitutes a bottleneck)? For example, is it the hatching date, pre-winter growth, over-winter metabolic rates, or a combination of factors?

This laboratory study addresses two management questions posed in the introduction that arose following changes to the thermal regime of the Columbia River and evidence of poor reproductive success in white sturgeon populations. Laboratory empirical data on overall growth and survival equating to the first rearing season showed that highest mortality occurs during the transition to exogenous feeding. Although fish reared in the warm thermal regime had higher mortality at the initiation of exogenous feeding, fish reared in the cool thermal regime exhibited higher chronic mortality throughout the rearing period, suggesting a reduced capacity for survival under prolonged rearing in cool water. Larger size at entry into a winter period has also been associated with greater survival in some fish species (Toneys and Coble 1979; Miranda and Hubbard 1994). In this laboratory study, fish reared under the cool thermal regime with a shortened first year growth period were quite small, with a mean TL of 44 mm (range 28-62 mm). In contrast, fish reared under the warm thermal regime and longer first-year growth period were substantially larger with a mean TL of 147 mm (range 72-208 mm). For comparison, age-0 fish captured during fall bottom trawling from the Columbia River downstream from Bonneville Dam were at least 176 mm TL (McCabe and Tracy 1994). In addition to growth and survival metrics, survival capacity was assessed via starvation experiments. Fish reared in the cool thermal regime survived longer in the absence of food, suggesting that they may be more able to survive a prolonged period of dispersal to productive foraging areas. The lipid assessments that are underway will provide an additional assessment of fish condition.

This laboratory study addresses two management questions posed in the introduction that arose following changes to the thermal regime of the Columbia River and evidence of poor reproductive success in white sturgeon populations. Laboratory empirical data on overall growth and survival equating to the first rearing season showed that highest mortality occurs during the transition to exogenous feeding. Although fish reared in the warm thermal regime had higher mortality at the initiation of exogenous feeding, fish reared in the cool thermal regime exhibited higher chronic mortality throughout the rearing period, suggesting a reduced capacity for survival under prolonged rearing in cool water. Larger size at entry into a winter period has also been associated with greater survival in some fish species (Toneys and Coble 1979; Miranda and Hubbard 1994). In this laboratory study, fish reared under the cool thermal regime with a shortened first year growth period were quite small, with a mean TL of 44 mm (range 28-62 mm). In contrast, fish reared under the warm thermal regime and longer first-year growth period were substantially larger with a mean TL of 147 mm (range 72-208 mm). For comparison, age-0 fish captured during fall bottom trawling from the Columbia River downstream from Bonneville Dam were at least 176 mm TL (McCabe and Tracy 1994). In addition to growth and survival metrics, survival capacity was assessed via starvation experiments. Fish reared in the cool thermal regime survived longer in the absence of food, suggesting that they may be more able to survive a prolonged period of dispersal to productive foraging areas. The lipid assessments that are underway will provide an additional assessment of fish condition.