Coho salmon, also known as silver salmon, are a fish species found in the Pacific Ocean. They’re native to the western coast of North America and are especially abundant in California.
Also known by their scientific name Oncorhynchus kisutch, coho salmon belong to the salmon family. They’re among the five Pacific salmon species. The other species in the family include:
Today, we discover the largest coho salmon ever caught in California. We also learn about the fish’s physical attributes, adaptations, and life cycle.
The Largest Coho Salmon Ever Caught In California
According to the California Department of Fish and Wildlife, the largest coho salmon ever caught in the state weighed 22 pounds. Milton Hain, a freshwater angler from Fairfax, caught the 38.5-inch fish using a lure at Paper Mill Creek in Marin County, CA, on January 3, 1959.
A more recent catch was a 29.5-inch long coho salmon weighing 8 pounds and 15 ounces. Its girth was 16.25 inches. Michael Ritter, a freshwater angler, caught the fish at the Oroville Diversion Pool in Butte County by a lure on July 2, 2015.
Although long and massive, Ritter’s catch failed to dislodge Hain’s as the largest ever caught in the state. From the state’s records, Ritter’s catch ranks second, although no other coho salmon entries exist.
The Largest Coho Salmon Ever Caught In The World
The largest coho salmon ever caught worldwide weighed 35 pounds and 4 ounces.
The fish was caught on October 26, 1985, in the Tyee Pool, Campbell River, British Columbia, Canada.
More recently, Tom Olivio from Montana caught a 34-pound coho salmon on September 19, 2012, on upstate New York’s Salmon River. The catch was 42.75 inches long with a 24-inch girth.
Coho salmon are a beautiful species with distinct physical characteristics, making them stand out.
Size And Weight
Coho salmon can grow 24-30 inches long and weigh 8-14 pounds. But don’t be surprised if you encounter much larger cohos.
Coho salmon have a distinctive color that keeps changing as they mature.
Juvenile cohos have a bright silver color with dark spots and a greenish-blue back. As they grow older and begin migrating to spawning grounds, their color changes to red and green with dark spots.
Coho salmon have a unique body shape—a large head and a long, streamlined body to help them swim efficiently. This allows the fish to navigate through turbulent currents to reach their spawning grounds.
Coho salmon’s reproduction process is complex yet fascinating.
Let’s delve into the details.
Coho salmon’s life cycle begins with laying eggs in freshwater rivers. The eggs hatch into alevins, which remain buried in the gravel for weeks feeding on the yolk sac attached to their body.
After depleting the yolk sac, the alevins transform into fry and begin swimming and feeding on small aquatic insects.
As the fry grow, they transform into smolts. At this stage, they move to the ocean to feed and mature.
After several years in the ocean, mature coho salmon return to their rearing ground to spawn. During the adult stage, coho salmon display their brilliant red and green breeding colors, making them a spectacular sight to behold.
Coho salmon embark on long migrations to spawning grounds, often traveling hundreds of miles up freshwater streams to reach their nesting sites.
The spawning behavior is a fascinating process, where males and females engage in an elaborate courtship dance before the female lays her eggs in a carefully selected nest.
After laying the eggs, the male fertilizes them, and the female covers them with gravel to protect them from predators.
The eggs then hatch into alevins, starting the cycle anew.
Note: Coho salmon only reproduce once in their lifetime, making their life cycle even more remarkable.
Environmental Factors Affecting Reproduction
The coho salmon reproduction process is influenced by various environmental factors, including:
- Water temperature
- Water quality
- Food availability
- Human interference
For instance, water temperature plays a vital role in egg development and survival, with optimal temperatures ranging from 44-50 degrees Fahrenheit.
On the other hand, water quality affects the young coho salmon’s survival and growth. High pollutant levels and poor water clarity can hurt their survival rates.
Coho salmon face various challenges in their life cycle, including natural and human-induced ones.
Natural challenges, such as disease and predators, can impact their reproduction and survival. In contrast, human-induced challenges, such as habitat destruction and overfishing, can devastate their populations.
Overfishing and habitat destruction are the biggest threats to coho salmon populations. Development, the construction of dams, and pollution cause significant harm to their breeding grounds. These activities can:
- Cause habitat loss
- Increase water temperatures
- Reduce the availability of food
These make it more difficult for the fish to reproduce and thrive.
Adaptations to Their Environment
Coho salmon are well-adapted to their environment and have various unique features enabling them to survive in their challenging habitat. Let’s examine their physical, behavioral, and ecological adaptations to their harsh environment.
Coho salmon’s physical adaptations include a streamlined body, scales and skin pigmentation, and gills and fins.
- A streamlined body shape. Cohos have a sleek, streamlined body shape to help them swim efficiently in freshwater and saltwater habitats and conserve energy while swimming long distances, especially during migration.
- Scales and skin pigmentation. Coho salmon’s scales are a barrier against opportunistic parasites and diseases. They also help to regulate the fish’s body temperature. Similarly, the fish’s skin pigmentation helps blend with the surroundings, concealing it from predators.
- Gills and fins. Cohos’ gills can extract oxygen from both freshwater and saltwater, allowing them to survive in various habitats. Their fins help them keep balance and maintain control during swimming. With these, they can swim against strong currents and navigate through their challenging habitats deftly.
In addition to physical adaptations, coho salmon have various behavioral adaptations that help them survive in their habitats.
- Migration instincts. The cohos’ strong migratory instincts drive them to return to their birthplace to spawn. In addition, water temperature changes, salinity, and other environmental factors trigger the instinct to allow them to complete their life cycle.
- Avoidance of predators. To avoid predators, the cohos swim in schools and change behavior when predators come calling. Moreover, the fish can make sudden turns and swim quickly to evade predators.
- Spawning behaviors. Coho salmon have specific behaviors related to spawning. For instance, they dig nests in riverbeds and defend their territory. These behaviors are essential for ensuring the survival of their offspring and have been adapted over time to maximize their chances of success.
Coho salmon feed on various prey, including plankton, squid, and small fish. They switch between different food sources depending on their habitat and food availability.
Threats To Their Populations
The future of coho salmon is at risk due to its numerous threats. They include:
- Habitat destruction and degradation
- Overfishing and harvesting
- Water pollution and contamination
- Parasites and diseases
Let’s take a closer look at each of the threats.
Habitat Destruction And Degradation
Habitat destruction and degradation are among the biggest threats to coho salmon populations. Deforestation and logging have led to the loss of the fish’s critical habitat that provides essential spawning and rearing grounds.
Urbanization and infrastructure development have reduced the fish’s suitable habitat, significantly declining their populations.
Climate change has also had a significant impact, with altered water flows and rising temperatures affecting the quality of the habitat available to the fish.
Overfishing And Harvesting
Overfishing and harvesting are other significant threats to the coho salmon populations. Sport and commercial fishing have reduced coho salmon numbers in the ocean. Consequently, many coho salmon populations are on the verge of extinction.
Conservation and management efforts have been initiated to address this issue. They include:
- Regulations on fishing seasons
- Catch limits
- Size restrictions
Water Pollution And Contamination
Another threat to the coho salmon populations is water pollution and contamination. Water pollution sources include:
- Agricultural runoff
- Industrial waste
The pollutants can either harm the fish directly or have indirect effects by reducing the quality of their habitat. Numerous mitigation efforts have been initiated to counter the impacts of water pollution. They include:
- Treatment plants
- Regulations on pollutant discharge into waterways
Parasites And Diseases
Coho salmon populations are also at risk from various parasites and diseases, including viruses and lice.
Management and prevention strategies have been put in place to prevent the spread of diseases and parasites. They include:
- Fish farming regulations
- Research and monitoring programs
Migration And Habitats
Coho salmon are known for their ability to thrive in various habitats and incredible migration patterns.
Let’s explore these two aspects of the coho salmon’s life.
As mentioned earlier, coho salmon have impressive migration patterns. First, they move from the ocean back to their home river in the spawning stage. The ocean migration can take a few months to several years, covering thousands of miles.
After reaching their home river, the cohos make the final lap journey upriver to spawning grounds.
The coho salmon are highly adaptable and can flourish in various habitats — from freshwater rivers to the open sea.
But they prefer clear, cold waters and are sensitive to water quality and temperature alterations.
As opportunistic feeders, coho salmon prey on various animal species. The most common ones include:
As they get to maturity, their predation skills improve significantly. They begin eating larger crustaceans and fish. This shift allows them to grow bigger and develop into stronger and more powerful predators.
Feeding Habits In The Different Stages Of Life
- Egg stage. The eggs aren’t yet capable of feeding.
- Alevin stage. Alevins feed on their yolk sac until it’s depleted, then eat small invertebrates.
- Fry stage. As fry, they eat zooplankton and small invertebrates.
- Smolt stage. As smolts, they eat squid and small fish.
- Adult stage. As adults, they primarily feed on squid and fish but may also eat crustaceans and other prey available.
As opportunistic feeders, coho salmon eat various prey as available. But they prefer crustaceans, squid, and small fish.
Influence Of Environmental Factors On Feeding Habits
- Water flow rate, salinity, and temperature can affect prey availability for coho salmon.
- Food availability and water quality changes can change coho salmon feeding habits.
Coho salmon are amazing creatures with unique physical attributes, behaviors, and adaptations. So it’s no wonder that they thrive in challenging habitats.
Unfortunately, this beautiful fish species is endangered due to the destruction and degradation of their habitat, overfishing, and the construction of dams on waterways. This calls for concerted efforts to protect them and enable them to thrive for years to come.
Where Is Marin County, California Located On A Map?
Marin County is in the northwestern part of the San Fransisco Bay Area and is located across the Golden Gate Bridge from the city of San Fransisco. It is between Napa and Sonoma and San Fransisco. Located in the state of California, which is located in the Western United States along the Pacific Coast. It is bordered by the Pacific Ocean to the west, Oregon to the north, Arizona and Nevada to the east, and the Mexican state of Baja California to the south.
The photo featured at the top of this post is © Keith Publicover/Shutterstock.com
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