Comprehensive passage (COMPASS) model: a model of downstream migration and survival of juvenile salmonids through a hydropower system

Abstract

Migratory fish populations are impacted worldwide by river impoundments. Efforts to restore populations will benefit from a clear understanding of survival and migration process over a wide-range of river conditions. We developed a model that estimates travel time and survival of migrating juvenile salmonids (Oncorhynchus spp.) through the impounded Snake and Columbia rivers in the northwestern United States. The model allows users to examine the effects of river management scenarios, such as manipulations of river flow and spill, on salmonid survival. It has four major components: dam passage and survival, reservoir survival, fish travel time, and hydrological processes. The probability that fish pass through specific routes at a dam and route-specific survival probabilities were based on hydroacoustic, radio telemetry, PIT tag, and acoustic tag data. We related reservoir mortality rate (per day and per km) to river flow, water temperature, and percentage of fish passing through spillways and then fit the relationships to PIT-tag survival data. We related fish migration rate to water velocity, percentage of fish passing through spillways, and date in the season. We applied the model to two threatened ''Evolutionarily Significant Units'' (as defined under the US Endangered Species Act): Snake River spring/ summer Chinook salmon (O. tshawytscha Walbaum) and Snake River steelhead (O. mykiss Walbaum). A sensitivity analysis demonstrated that for both species survival through the hydropower system was responsive to water temperature, river flow, and spill proportion. The two species, however, exhibited different patterns in their response. Such information is crucial for managers to effectively restore migratory fish populations in regulated rivers.

Contrasting life-cycle impacts of stream flow on two Chinook salmon populations

“…This was likely due to several factors: (1) year class strength was set before smolting in the Lemhi River, (2) migration flow levels, while clearly reduced from historical levels, were nevertheless at peak stages during migration, and (3) smolt-adult return rate is more predictable by ocean conditions than freshwater variation. Other researchers have detected flow-dependent survival relationships for migrating salmonids in the Columbia River Basin (Muir et al, 2001;Connor et al, 2003;Smith et al, 2003;Zabel et al, 2008) and elsewhere (Kocik & Taylor, 1987;McCormick et al, 1998), although relatively few efforts have put the effects of migration flows in the context of the life cycle.…”

Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns

“…Juvenile salmonines passing through lakes and reservoirs (Jepsen et al 1998;Olsson and Greenberg 2004) and larger rivers (Collis et al 2001;Rieman et al 1991) during their smolt migration can incur relatively high levels of mortality owing to predation by fish and birds. Additionally, juvenile salmonines often incur direct mortality during dam passage (Sandford et al 2012;Zabel et al 2008), and dams may influence the timing and speed of adult migration. Consistently higher rates of mortality during juvenile or adult migration, such as those caused by anthropogenic barriers and impediments, may therefore select against anadromy (Fig.…”

Declining patterns of Pacific Northwest steelhead trout (Oncorhynchus mykiss) adult abundance and smolt survival in the ocean

“…Freshwater migration mortality of salmonids can be substantial (Romer et al 2013), especially when the fish must migrate through multiple dams (Sandford et al 2012;Zabel et al 2008), and can thus influence abundance and SAR values. To avoid these potentially confounding factors, we focused on Pacific Northwest steelhead from coastal areas (O. mykiss irideus) with relatively short freshwater migrations to the ocean.…”