Summary White Sturgeon, Acipenser transmontanus (WS), are distributed throughout three major river basins on the West Coast of North America: the Sacramento‐San Joaquin, Columbia, and Fraser River drainages. Considered the largest North American freshwater fish, some WS use estuarine habitat and make limited marine movements between river basins. Some populations are listed by the United States or Canada as threatened or endangered (upper Columbia River above Grand Coulee Dam; Kootenai River; lower, middle and, upper Fraser River and Nechako River), while others do not warrant federal listing at this time (Sacramento‐San Joaquin Rivers; Columbia River below Grand Coulee Dam; Snake River). Threats that impact WS throughout the species’ range include fishing effects and habitat alteration and degradation. Several populations suffer from recruitment limitations or collapse due to high early life mortality associated with these threats. Efforts to preserve WS populations include annual monitoring, harvest restrictions, habitat restoration, and conservation aquaculture. This paper provides a review of current knowledge on WS life history, ecology, physiology, behavior, and genetics and presents the status of WS in each drainage. Ongoing management and conservation efforts and additional research needs are identified to address present and future risks to the species.

Forty-eight adult striped bass Morone saxatilis (3.2-19.1 kg) were captured by electrofishing in the tailrace of Richard B. Russell Dam and in the upper reaches of two major tributaries; they were implanted with temperature-sensitive radio transmitters and tracked approximately bimonthly for 20 months. As J. Strom Thurmond Reservoir downstream from the dam became thermally stratified in May, fish vacated the tributaries. From June to October, all striped bass were found within the reservoir's historical Savannah River channel. By August, most of the instrumented fish were found in the upper section of the reservoir, where optimal habitat was available throughout the summer owing to cool, artificially oxygenated hypolimnetic discharges from Richard B. Russell Dam. In mid-October the reservoir destratified, and fish dispersed from their up-reservoir summering areas and redistributed themselves throughout the reservoir. During early winter, the striped bass returned to tributary habitat or down-reservoir areas and generally used these locations throughout the winter. The fish exhibited a high degree of site fidelity to their summering areas, source tributaries (after fall dispersal and throughout the winter), and spring spawning areas. Mean movement rates were highest in the spring and fall, corresponding to the migration from tributaries in May and the return migration after fall dispersal. Mean movement rates were lowest in summer and winter, corresponding to the periods of high fidelity to summering and wintering areas. The average monthly temperatures and dissolved oxygen concentrations in areas used by striped bass were 19.0-20.4ЊC and 4.86-6.44 mg/L during May-October, which corresponded to average monthly habitat suitability index values of 0.76-0.98. Striped bass avoided temperatures above 25.1ЊC and dissolved oxygen concentrations less than 2.3 mg/L.

River regulation alters the thermal regime of many freshwater ecosystems, and impoundments are known to negatively impact the recruitment of fluvial Burbot Lota lota populations. Some conservation programs in North America and Eurasia have begun to incorporate stocking of hatchery Burbot to mitigate extirpation risks. Anthropogenic modification of river temperatures and population structure has unknown implications for Burbot reproduction. This study evaluated the effects of elevated water temperatures and different maternal ages on spawning and embryo development of hatchery Burbot. Juveniles stocked downstream of a hydroelectric dam were found to naturally mature in a warmer postdam regime. The river‐adapted hatchery adults volitionally spawned in a broodstock facility at 2, 4, and 6°C. The spawning period spanned 18 d at 2°C but was shortened to 6−7 d at 4°C and 6°C. Survival of embryos to the eyed stage was 86.7, 47.9, and 0.1% at incubation temperatures of 2, 4, and 6°C, respectively. Embryo deformity increased dramatically between 4°C and 6°C. Young (age‐3) and old (age‐7 and older) females spawned 4−12 d later than 5‐ and 6‐year‐old females. Age‐3 females spawned smaller eggs, but no relationship was found between maternal age and embryo vital rates. It was concluded that juvenile stocking supplemented the abundance of reproductive adults in the highly altered ecosystem of the lower Kootenai River. Spawning temperatures above 4°C potentially underlie Burbot recruitment bottlenecks in systems affected by impoundments, climate warming, or other barriers to coldwater spawning habitat. Contraction of the spawning period by warmer temperatures, a truncated population age structure, or both could synchronize spawning to coincide with suboptimal conditions for normal embryo development.

The salinity and temperature tolerances of black sea bass Centropristis striata juveniles (46 ± 10.3 mm total length [mean ± SD]) were estimated to assist in decisions concerning location of culture facilities and types of production systems. At 21°C, all exposed fish survived for 7 d in salt concentrations of 10, 20, or 35 g/L. All fish exposed to salt concentrations of 5 g/L died within 3 d. Temperature extremes were estimated after acclimation of fish to 24–25°C. Half of the juveniles exposed to a gradual increase (+0.65°C/d) or decrease (–0.51°C/d) in temperature (at a nominal salt concentration of 20 g/L) were dead when the water temperature reached 33.3°C and 3.7°C, respectively. Results of this study indicate that this species requires saline water at or above a salt concentration of 10 g/L and that it may not be practical to keep black sea bass over winter or over summer in shore‐based outdoor facilities located in temperate climates.

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