Author: Bradley J Cavallo

American shad are the Chinook salmon of herring. Like Chinook salmon, adult American shad spend several years in the ocean before returning to rivers for spawning — they’re anadromous. Also, like salmon, anglers love shad because they’re fun to catch and good to eat. Well, okay, shad are not as good to eat as ocean caught salmon, but they are delicious when prepared well.  American shad are native to the east coast of North American. They were introduced to the Sacramento River after repeated releases of shad fry — transported via the then newly completed transcontinental railroad — between 1871 and 1880. Shad quickly became abundant in the Sacramento River […]
California is at the southern boundary of the distributions of cold-water dependent fish species like salmon and steelhead. In many California rivers, flows and water temperatures challenge the performance and survival of salmonids even in years with average levels of precipitation. Drought and warmer summer air temperatures associated with climate change further exacerbate those stresses.  At and above the Sierra Nevada foothills, Central Valley rivers are heavily regulated.  The dams there provide a variety of benefits for humans — water supply, flood control, hydropower, and recreation — but have some predictable and well-understood adverse impacts on salmonid populations. Dams block upstream passage of adult salmonids, preventing those anadromous fishes from reaching […]
In the 1981 blockbuster film “Raiders of the Lost Ark”, the nefarious French archaeologist Belloq holds up a cheap pocket watch and explains to Indiana Jones “It’s worthless. Ten dollars from a vendor in the street.  But I take it, I bury it in the sand for a thousand years, it becomes priceless…” Here in the Delta, fisheries monitoring data are treated a lot like Belloq’s watch. An ancient, sandy watch isn’t valued for keeping precise time. Just the same, long-term fisheries monitoring data aren’t necessarily valued because they provide information effective for monitoring and managing Delta fishes. Consider one of the simplest fisheries monitoring tools; the seine, a length of net […]
Increasing Central Valley salmon populations in a highly regulated river system is a complex undertaking. Restoring habitats and ecosystem processes, augmenting fish passage, screening diversions, hatchery reform, and improved harvest management are integral components of successful conservation efforts. But restoring a semblance of a natural flow regime — sometimes termed “functional flows” — is often the focus of efforts to improve the status of salmon in Pacific Coast rivers. While it might seem straightforward to reestablish a natural hydrograph in efforts to encourage the ecological and biophysical processes to sustain salmon life stages — well, it’s not. Between obligations related to dam operations (flood control, water storage) and environmental requirements […]
Policy makers and scientists often attribute the poor progress being made toward resolving fish conservation and water allocation issues — despite billions of dollars of invested over the past half century — to the physical and ecological complexities of the Sacramento-San Joaquin Delta. The challenge of meeting the goals established in California’s Delta Reform Act, ensuring statewide water-supply reliability and restoring a vibrant and healthy Delta ecosystem, has been referred to as a “wicked” problem, one that may be not fully resolvable. It is doubtless the case that a century-and-a-half of human impacts have altered the system in many ways that are, as a practical matter, irreversible. But a recent article in […]
Off the coast of California and southern Oregon, Chinook salmon are subjected to a uniquely intense commercial and recreational fishery. The fishery relies upon the availability of abundant, hatchery-produced Central Valley fall-run Chinook. However, as currently managed, the fishery provides minimal protection for natural-origin (wild) fall-run Chinook and for winter-run and spring-run Chinook that are listed under the federal Endangered Species Act (ESA), especially fish maturing at age-4 or older. Variation in age-at-maturity is essential for the viability of all runs of Chinook salmon because it buffers populations from short-term environmental changes in freshwater habitats and from catastrophic events. The age-structure of Central Valley Chinook salmon populations is severely truncated. […]
Spring-run Chinook salmon have long played second fiddle to winter-run Chinook salmon when it comes to conservation planning for the Central Valley salmonids protected under the California and federal Endangered Species Acts. But earlier this year, the California Department of Fish and Wildlife issued an Incidental Take Permit (ITP) that promises increased attention for spring-run Chinook. The ITP calls for the aggressive development of a spring-run Juvenile Production Estimate (JPE). The purpose of the JPE is to better track the abundance of juvenile spring-run Chinook and, ostensibly, to provide a basis for setting the number of juvenile spring-run Chinook that the State Water Project is allowed to entrain at the […]
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