Philip T. Sandstrom

Estimating Survival and Migration Route Probabilities of Juvenile Chinook Salmon in the Sacramento–San Joaquin River Delta

Abstract Juvenile Chinook salmon Oncorhynchus tshawytscha emigrating from natal tributaries of the Sacramento River must negotiate the Sacramento–San Joaquin River Delta, a complex network of natural and man-made channels linking the Sacramento River with San Francisco Bay. Natural processes and water management actions affect the fractions of the population using the different migration routes through the delta and survival within those routes. However, estimating these demographic parameters is difficult using traditional mark–recapture techniques, which depend on the physical recapture of fish (e.g., coded wire tags). Thus, our goals were to (1) develop a mark–recapture model to explicitly estimate the survival and migration route probabilities for each of four migration routes through the delta, (2) link these route-specific probabilities to population-level survival, and (3) apply this model to the first available acoustic telemetry data of smolt migration through the delta. The point estimate of sur...

Diel movements of out-migrating Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) smolts in the Sacramento/San Joaquin watershed

We used ultrasonic telemetry to describe the movement patterns of late-fall run Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) smolts during their entire emigration down California’s Sacramento River, through the San Francisco Bay Estuary and into the Pacific Ocean. Yearling hatchery smolts were tagged via intracoelomic surgical implantation with coded ultrasonic tags. They were then released at four upriver locations in the Sacramento River during the winters of 2007 through 2010. Late-fall run Chinook salmon smolts exhibited a nocturnal pattern of migration after release in the upper river. This is likely because individuals remain within a confined area during the day, while they become active at night and migrate downstream. The ratio between night and day detections of Chinook salmon smolts decreased with distance traveled downriver. There was a significant preference for nocturnal migration in every reach of the river except the Estuary. In contrast, steelhead smolts, which reside upriver longer following release, exhibited a less pronounced diel pattern during their entire migration. In the middle river, Delta, and Estuary, steelhead exhibited a significant preference for daytime travel. In the ocean Chinook salmon preferred to travel at night, yet steelhead were detected on the monitors equally during the night and day. These data show that closely related Oncorhynchus species, with the same ontogenetic pattern of out-migrating as yearlings, vary in migration tactic.

Migration route selection of juvenile Chinook salmon at the Delta Cross Channel, and the role of water velocity and individual movement patterns

We examined movement tracks of ultrasonic-tagged juvenile Chinook salmon (Oncorhynchus tshawyscha) smolts at the juncture of two migratory pathways. This migratory juncture occurs where the Delta Cross Channel splits from the Sacramento River in California’s Sacramento–San Joaquin Delta. Smolt tracks were analyzed to compare the importance of river flow and individual parameters in migratory route selection. The two routes differ significantly in smolt survival probabilities (Perry et al. N Am J Fish Manag 30:142–156, 2010), thus a clearer understanding of the variables contributing to route selection will be valuable for management of this declining species. A comparison of the two migratory groups showed that fish remaining within the Sacramento River: 1) Encountered the migratory juncture when river water velocities were much higher than those in the Delta Cross Channel (p < 0.0001), 2) showed more direct swimming paths (p = 0.03) and 3) migrated at higher speeds (p = 0.04). Logistic regression models showed that the ratio of mean water velocity between the two routes was a much stronger predictor of ultimate route selection than any other variable tested. However, parameters for both the lateral position of smolts within the river and smolt size added predictive power to the final model. Our results suggest that river flow remains the most important variable for predicting smolt migration route, but note that knowledge of individual smolt attributes and movement patterns can increase our predictive ability.

Effect of Tides, River Flow, and Gate Operations on Entrainment of Juvenile Salmon into the Interior Sacramento–San Joaquin River Delta

AbstractJuvenile Chinook Salmon Oncorhynchus tshawytscha emigrating from natal tributaries of the Sacramento River, California, must negotiate the Sacramento–San Joaquin River Delta (hereafter, the Delta), a complex network of natural and man-made channels linking the Sacramento River with San Francisco Bay. Fish that enter the interior and southern Delta—the region to the south of the Sacramento River where water pumping stations are located—survive at a lower rate than fish that use alternative migration routes. Consequently, total survival decreases as the fraction of the population entering the interior Delta increases, thus spurring management actions to reduce the proportion of fish that are entrained into the interior Delta. To better inform management actions, we modeled entrainment probability as a function of hydrodynamic variables. We fitted alternative entrainment models to telemetry data that identified when tagged fish in the Sacramento River entered two river channels leading to the interio...

An introduction to the use of electronic tagging to provide insights into salmon migration and survival

The west coast of North America serves as home for five species of semelparous salmon and the iteroparous steelhead and cutthroat trout, all in the genus Oncorhynchus. Currently, only Chinook salmon (O. tshawytscha) and steelhead trout (O. mykiss) reside in the rivers and streams of California’s Central Valley. By contrast, the coastal streams of California contain coho salmon (O. kisutch), Chinook salmon and, to a much lesser extent, cutthroat trout (O. clarki). The rivers and streams of the Central Valley are unique because they host four Chinook salmon runs identified by the season when most adults return to freshwater to spawn. These seasons include winter, spring, fall, and late-fall (Fry 1961; Stone 1874). Of the four runs, the fall run is the most abundant, largely due to supplementation by hatchery production (Fisher 1994). Fall-run juvenile Chinook salmon emigrate to the ocean soon after hatching. Some of their springrun and winter-run counterparts engage in similar conduct, thereby exhibiting what is known as ocean-type behavior. Late-fall and some spring-run juveniles use a different strategy, remaining in freshwater for a few weeks to several months before outmigrating to the ocean at a larger size. This pattern is described as stream-type behavior. The ocean-type juveniles spend relatively little time in streams and enter the ocean at a small size [80 mm fork length (FL)]. The stream-type juveniles enter the ocean at 120–180 mm FL. These larger stream-type smolts are also called yearlings. Central Valley steelhead are currently recognized only as winter run, although in the past there may have been a summer run as wIell (Needham et al. 1941). Juvenile steelhead vary in freshwater residency and age at ocean entry. While many enter the ocean as smaller sub-yearlings, others enter as larger yearlings or when even older. Populations of coho salmon migrate upstream and spawn in coastal streams and larger rivers outside of the Central Valley, especially in the area north of the Golden Gate, the estuarine exit for Central Valley salmonids. Today salmon populations are only a fraction of their historical abundance, primarily because of the loss of spawning habitat that has resulted from dam construction. Sacramento River winter-run Chinook salmon are classified as endangered under the U.S. Endangered Species Act (ESA) of 1973, with Central Valley steelhead and spring-run Chinook salmon listed Environ Biol Fish (2013) 96:131–133 DOI 10.1007/s10641-012-0099-x