The Pacific Lamprey Entosphenus tridentatus, an anadromous fish native to the northern Pacific Ocean and bordering freshwater habitats, has recently experienced steep declines in abundance and range contractions along the West Coast of North America. During the early 1990s, Native American tribes recognized the declining numbers of lamprey and championed their importance. In 2012, 26 entities signed a conservation agreement to coordinate and implement restoration and research for Pacific Lamprey. Regional plans have identified numerous threats, monitoring needs, and strategies to conserve and restore Pacific Lamprey during their freshwater life stages. Prime among these are needs to improve lamprey passage, restore freshwater habitats, educate stakeholders, and implement lamprey‐specific research and management protocols. Key unknowns include range‐wide trends in status, population dynamics, population delineation, limiting factors, and marine influences. We synthesize these key unknowns, with a focus on the freshwater life stages of lamprey in the Columbia River basin.

Hickory shad Alosa mediocris were sampled for two consecutive years in coastal North Carolina at various points of their ascent in salt water, brackish water, and freshwater to examine reproductive development and related variables during the spawning migration. Fish averaged 3 years of age; however, the proportion of repeat spawners and the proportion of individuals in older age‐classes were greater for females than for males, and females were larger than males of the same age. Nearly all fish had identifiable food items in their stomachs early in migration. Feeding decreased significantly as fish entered freshwater, and energy reserves became depleted with movements upstream. Reproductive development was positively correlated with inland movements, as indicated by increases in the gonadosomatic index and oocyte size and based on histological examination. Separate oocyte size‐classes were observed within the same individuals, and postovulatory follicles were also present; these observations indicate that hickory shad are batch spawners with indeterminate fecundity and group‐synchronous development of oocytes. Postspawn females with yolked oocytes were captured while feeding in the estuary after the reproductive season. Migratory timing was similar in both years, and a strong positive correlation between water temperature and fish movements was evident. Results indicate that reproductive development in migrating hickory shad is significantly related to size, age, energy reserves, geographic location, and time of year. This information contributes to a better understanding of the relatively unstudied hickory shad and serves as a basis for further research on alosine fishes in the eastern United States.

The returns of Pacific Lamprey Entosphenus tridentatus to the Columbia River over the past decade have declined significantly compared with the peak returns of the 1950s and 1960s, with no quantifiable mechanisms identified. To determine if the abundance of documented host species in the marine environment is related to adult returns of Pacific Lamprey, we examined stock assessment data, commercial fishery statistics, and counts of adult fish at Bonneville Dam between 1997 and 2010. Significant positive correlations were observed between lamprey returns and abundance indices of Pacific Hake Merluccius productus, Walleye Pollock Theragra chalcogramma, Pacific Cod Gadus macrocephalus, Chinook Salmon Oncorhynchus tshawytscha, and Pacific Herring Clupea pallasii throughout the U.S. Pacific Northwest. Commercial landings of these species in Washington and Oregon were also significantly and strongly correlated to lamprey returns, with the exception of Walleye Pollock. Several of these fisheries have demonstrated significant reductions in mean landings since the 1950s and 1960s, and adult lamprey returns have declined proportionally. We further examined large‐scale and regional indices of oceanic productivity as a potential underlying mechanism. Multiple regression techniques indicated that host abundance was the principal factor in predicting lamprey returns, though inclusion of oceanic conditions increased the precision of the model. These results represent the first established relationship to recent trends of Pacific Lamprey returns to the Columbia River and indicate that spawning escapement is primarily a function of conditions experienced during the predatory phase of the life cycle. We hypothesize that Pacific Lamprey abundance in the Columbia River is cyclical in nature, but limited by availability of several host species over a potentially vast geographic range. Biologists and resource managers should reassess the relatively overlooked marine ecology of Pacific Lamprey.

Trapping facilities are regularly used to achieve a variety of fishery research and management goals. Though care of sampled organisms is a central tenet of most agencies, the effects of trapping on fish behavior are seldom quantified. We used passive integrated transponder technology to calculate passage delay and blockage of adult Sockeye Salmon at a facility where all spring‐migrating fishes were trapped for research between 2008 and 2010. Median passage delay ranged from 0.4 to 8.7 days, and 8% to 38% of the return (2,387 to 21,090 adults) was precluded from reaching upriver spawning habitat. A protocol limiting trapping to less than 24 h per week was implemented in 2011 and median delay decreased to 6 min, with the result being that nearly all fish were able to ascend to spawning grounds for two consecutive years. The annual variation in delay was unrelated to run size or river flow, indicating that research activities requiring intensive trapping operations had inadvertently blocked tens of thousands of adult salmon from reaching spawning tributaries. We use this case study to advocate the adoption of a precautionary approach where trapping of adult migratory fishes is proposed but the effects are unknown.

We assessed the effects of rearing conditions in four hatchery programs from the upper Columbia River basin on the survival and demographics of yearling summer Chinook Salmon Oncorhynchus tshawytscha over four release years. Juveniles from each hatchery program were initially reared at Eastbank Hatchery near Wenatchee, Washington, (which uses groundwater for fish rearing) and experienced similar rearing temperatures until their first autumn in culture. Fish that were to be used for two of the programs were subsequently transferred to surface water acclimation sites, where they were reared until release the following spring (surface water winter rearing). Fish to be used for the other two programs were overwintered at the Eastbank Hatchery and then transferred to their acclimation and release sites 1 to 2 months before spring release (groundwater winter rearing). Fish from the two rearing strategies experienced contrasting temperature profiles, which in turn affected winter growth, age at maturation, and smolt-to-adult survival (SAS). Overall, the two release groups that were overwintered in colder surface water experienced reduced winter growth, reduced minijack rate, and smaller size at release, but achieved a two-to threefold higher SAS than did the two release groups overwintered in warmer groundwater at Eastbank Hatchery. In addition, based on migration data compiled from fish tagged with PIT tags, smaller juveniles tended to mature at older age-classes than did larger smolts. We concluded that rearing yearling hatchery summer Chinook Salmon under more natural thermal regimes (surface water) may result in the return of larger, older adults that have a higher survival rate than would fish reared under constant or less natural thermal regimes (ground water). These results highlight the importance of the hatchery-rearing environment in shaping the survival and life history of summer Chinook Salmon juveniles released into the Columbia River basin.