So. Cal. Steelhead: Endangered Fish Tells a Story
The lifecycle of the Southern California steelhead demonstrates how the ocean and land environments are connected—what we do on land affects the ocean and marine life. With an increasingly urbanized coast, the steelhead struggles to survive in the Southern California area.
Southern California is home to one of the world’s busiest, most densely populated urbanized coasts. Human infrastructure stretches from the ocean shore to the mountains, and migrating wildlife must find a way to negotiate travel along pathways that are now intersected by freeways, dams, concrete river channels, housing developments, and other manmade barriers. In addition, many wildlife habitats have been degraded by pollution and other factors. As people find ways to coexist with nature, humans have begun modifying infrastructure to accommodate the ecology and migratory behavior of wild animals.
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The lifecycle of the Southern California steelhead demonstrates how the ocean and land environments are connected—what we do on land affects the ocean and marine life.
With an increasingly urbanized coast, the steelhead struggles to survive in the Southern California area.
Southern California is home to one of the world’s busiest, most densely populated urbanized coasts. Human infrastructure stretches from the ocean shore to the mountains, and migrating wildlife must find a way to negotiate travel along pathways that are now intersected by freeways, dams, concrete river channels, housing developments, and other manmade barriers.
In addition, many wildlife habitats have been degraded by pollution and other factors. As people find ways to coexist with nature, humans have begun modifying infrastructure to accommodate the ecology and migratory behavior of wild animals.
Southern California Steelhead
Several dozen rainbow trout are on view in the Aquarium’s exhibit. Southern California Steelhead are born in fresh water as rainbow trout. Some trout change into Steelhead, and migrate to the ocean as adults.
One such example involves the Southern California steelhead, a fish that faces extinction without our help.
The Southern California steelhead (Oncorhynchus mykiss) is a member of the salmon family. Steelhead are anadromous, meaning that they are born in freshwater, migrate to the sea where they spend most of their lives growing and maturing, and then return to freshwater rivers and streams to spawn, or reproduce.
Other anadromous fish species include salmon, smelt, striped bass, and sturgeon. Steelhead are the only anadromous fish species in the salmon family that currently reproduces in Southern California rivers and streams.
Population In Peril
They historically travelled up and down the Los Angeles and San Gabriel Rivers to spawn and return to the ocean, with a total population of about 40,000 fish around the turn of the twentieth century.
In fact, at that time, the San Gabriel River was known as one of the best steelhead fishing rivers in the state with anglers landing hundreds of fish a day. However, many factors have impacted steelhead habitats and made it more difficult for them to reproduce.
Experts believe the population has declined to fewer than 500 adult steelhead.
When newly hatched rainbow trout emerge from their gravel nest in a freshwater river or stream, they begin to feed and grow.
Juveniles primarily eat aquatic and terrestrial insects. Adults feed on fish eggs, small minnows, and freshwater invertebrates. Some rainbow trout may remain in their birth stream for their entire lives.
But environmental factors trigger others to take on an anadromous lifestyle and migrate downstream to the ocean. These factors appear to include the volume of water flowing in the stream and availability of food.
In years with increased rainfall, more water flows through rivers and streams, transporting more food for the fish in the stream. With greater food availability, more rainbow trout are likely to take on the anadromous form of the species.
The exhibit represents the species’ habitats, from freshwater streams to the ocean.
Southern California Steelhead Story Exhibit
In coming months Aquarium staff members hope to use the exhibit to investigate the environmental factors that trigger the change from rainbow trout to steelhead and better understand why some rainbow trout make the change and others do not.
For those juvenile trout that begin to migrate downstream as part of their journey to the ocean, physiological changes begin to occur that will allow them to live in saltwater.
This process is called smoltification, and juvenile trout undergoing these changes are called smolts.
The gills and internal organs, particularly the kidneys, change so the fish will be able to excrete the excess salt that is normally ingested while feeding and growing in saltwater. The smolts lose the brilliant coloring typical of rainbow trout in streams, becoming silvery or “steely.” The tail and fin margins darken, the body becomes slender, and the head is somewhat enlarged.
In the ocean, steelhead feed on smaller fish like herring, anchovies, and sardines, as well as squid, shrimp, and krill.
The Southern California Steelhead goes through several physical changes during its lifecycle, allowing it to live in both fresh- and salt water.
Southern California steelhead may spend up to seven years in freshwater before undergoing smoltification and three years in the ocean to mature before returning to freshwater to reproduce.
Steelhead usually return to the stream where they were born to spawn, but they have the ability to spawn in neighboring streams, improving their odds of survival in years when some streams are not flowing or become otherwise unavailable to the fish.
Steelhead can travel hundreds of miles upstream to reach the headwaters in a watershed.
They have also been known to spawn up to three times, while salmon die after spawning once. They can also skip a spawning season entirely. These factors improve their resilience to environmental changes.
It is estimated that steelhead can live up to eleven years. They can reach up to 55 pounds in weight and 45 inches in length, although the average size is much smaller.
Rainbow Trout vs. Steelhead
Steelhead are found in coastal streams along the West Coast of North America from Southern California to Alaska and the Aleutian Islands.
Southern California steelhead, ranging from the Santa Maria River north of Santa Barbara to the U.S.-Mexico border, are listed as endangered under the U.S. Endangered Species Act. The National Marine Fisheries Service (NMFS) listed the Southern California population of steelhead as endangered in 1997.
Impact Of Development
As Southern California became more populated and industrialized over the course of the twentieth century, it became necessary to control rivers to reduce flooding and also for domestic, agricultural, and commercial purposes.
In 1938 heavy rainfall caused massive flooding in Los Angeles, leading the Army Corps of Engineers to channel the Los Angeles River in a concrete basin. From 1921 to 1957 seven major dams were installed along the Los Angeles and San Gabriel Rivers, mostly for flood control.
These projects made it more difficult for steelhead to reach their spawning grounds at the headwaters of these rivers and modified the water flow that is necessary for migration. In addition, urban development along rivers and the coast has reduced and degraded steelhead habitats.
Many other factors attributed to human activity, such as industry, agriculture, recreation, and development, have contributed to the decline of steelhead in Southern California.
These include increases in stream temperature, degradation of water quality, removal of vegetation, increased amounts of sediment in steelhead spawning and rearing areas, loss of estuaries and wetlands, introduction of non-native species, and habitat fragmentation.
Projected impacts of future climate change also pose challenges to steelhead in Southern California. However, NMFS identifies barriers like dams and alteration of water flow by diversion or withdrawal as the two principal threats.
In 2012 NMFS published the Southern California Steelhead Recovery Plan.
The goal of the plan is to ensure the long-term persistence of self-sustaining wild steelhead populations. The recovery plan identifies priority recovery actions in each of five biogeographic population groups within Southern California.
Conservation efforts by NMFS include protecting existing steelhead populations, supporting research on the species, captive rearing in hatcheries, removal and modification of dams that obstruct steelhead migration, restoration of degraded habitat, acquisition of key habitat, and actions to improve water quality and streamflow.
As required in the Endangered Species Act, other federal agencies must consult with NMFS before taking any action that could affect endangered steelhead, such as building a freeway that crosses a steelhead stream.
The agencies work together to ensure the project is fish-friendly, says Anthony Spina, chief of NMFS’ Southern California Coastal Office. NMFS works with the public, private landowners, and other stakeholders to implement the actions in the recovery plan.
For example, NMFS has been working with Southern California water agencies and local governments to improve steelhead passage conditions at existing dams and floodcontrol structures and access to historical spawning and rearing habitats, Spina reports.
Southern California steelhead were once abundant in the region’s streams and rivers.
In addition, organizations that grew out of sportfishing and fly fishing in the region have formed coalitions and partnerships with state and federal agencies to conserve steelhead.
These include California Trout and Trout Unlimited, as well as several other groups, many of which provided support for the Aquarium’s steelhead exhibit.
These groups have not only advocated for policies protecting steelhead and testified before state and federal commissions on the consequences of prospective laws, but also have assisted in such efforts as moving fish from low-flowing streams or isolated pools to waters where they have a better chance of survival and reproduction. Also, Friends of the Los Angeles River (FOLAR) recently began regular monitoring excursions to look for steelhead.
What You Can Do
The Southern California steelhead has survived variable conditions and man-made alterations to its habitats.
Humans can help speed steelhead recovery by becoming stewards of their local watersheds. Learn about watershed issues and what can be done to keep watersheds healthy and free of trash and pollution. Participate in river and beach clean-up events. Avoid over-watering your home garden and eliminate the use of toxic pesticides or fertilizers that get washed into storm drains as a result.
What You Can Do (Cont.)
Learn about water conservation and avoid wasting water at home and at work.
Get involved at the local level—talk with your local water agency and government representatives about modifying dams and water diversions to improve conditions for steelhead.
The more people who become educated about reducing harmful impacts on the environment, especially near their homes, the greater the momentum will be to make the kinds of infrastructure and societal changes that will make it possible for endangered animals like Southern California steelhead to thrive.
Historian John G. “Tom” Tomlinson, Jr., in collaboration with the Aquarium of the Pacific, has written a book documenting the local history of the Southern California steelhead, including historic photos, postcards, fishery data, newspaper clippings, and rainfall statistics.
Against the Currents: The Unlikely Story of the Southern California Steelhead gathers historical information about this fish species and describes its resilience in the face of the region's changing watersheds, rainfall levels, and man-made infrastructure. The book is available for purchase online at shop.aquariumofpacific.org.