Starting next month, millions of young California salmon could be migrating to the ocean in tanker trucks instead of swimming downstream in the Sacramento River.
On Monday, state and federal wildlife officials announced a plan to move hatchery-raised salmon by truck in the event the state’s ongoing drought makes the Sacramento River and its tributaries inhospitable for the fish. They fear the rivers could become too shallow and warm to sustain salmon trying to migrate to sea on their own.
Shrunken habitat could deplete food supply for the young fish, and make them easier prey for predators. It also would make the water warmer, which can be lethal to salmon.
“The conditions may be so poor as to produce unacceptable levels of mortality for the out-migrating juveniles,” said Bob Clarke, fisheries program supervisor at the U.S. Fish and Wildlife Service.
Clarke’s agency operates Coleman National Fish Hatchery on Battle Creek, a tributary of the Sacramento River near Red Bluff. It is the largest salmon hatchery in the state, producing about 12 million fall-run Chinook salmon. The hatchery was built to atone for habitat losses caused by construction of Shasta Dam.
Coleman hatchery salmon are usually released into Battle Creek in April and May. Fishery experts prefer to release young fish into rivers so they imprint on the location as “home” and are better able to migrate back from the ocean for spawning three to four years later.
Fall-run Chinook salmon from the Sacramento River and its tributaries compose the bulk of the wild-caught salmon available in California markets and restaurants, and also feed a lucrative sport-fishing industry. In total, these fish represent a multibillion-dollar slice of the state’s economy each year.
California is experiencing one of its driest winters on record. Despite the recent storms, the Sierra snowpack that the state relies on to replenish its reservoirs remains depleted. Without an unusually wet March – and the long-term forecast calls for predominantly dry weather – officials fear rivers may be so diminished in April and May that young salmon will not survive their migration to the ocean.
They are also concerned that water diversions from the Sacramento-San Joaquin Delta during a low-water year could slaughter many of these young salmon, which measure about 6 inches long. Water pumped out of the Delta by state and federal agencies serves 25 million people from Napa to San Diego.
The trucking plan, devised by the state and federal fisheries agencies, includes a series of triggers, based on river and water supply conditions, that would launch a massive operation to haul the salmon in tanker trucks on a nearly three-hour drive from Red Bluff to San Pablo Bay near Vallejo. There, the salmon would be released into floating net pens to acclimate to new salinity and temperature conditions, then set free to swim for the ocean.
The California Department of Fish and Wildlife is adopting similar plans for its hatcheries on the Feather, American and Mokelumne rivers. Each produces several million young salmon every year.
Historically, the state hatcheries have trucked a significant share of their salmon, even in normal water years, to protect them from pollution, predators and water diversions. More recently, the state began shifting some salmon to in-river releases following evidence that trucked fish are more prone to “stray” into the wrong river when they return to spawn as adults. This harms the unique genetic traits of each river’s salmon species.
The department is in the midst of a multiyear study to evaluate the effectiveness of trucking versus in-river releases on salmon survival and migration. It also includes use of a barge to transport hatchery salmon. Aboard the barge, salmon are protected from predators and water diversions but experience the gradual changes in water temperature and chemistry that occur with a self-powered migration.
With trucking, by comparison, the salmon experience a kind of shock when suddenly released into the bay, which can make them more vulnerable to predators.
This year’s salmon trucking plan is similar to one carried out in the drought of 1991-92. Officials view it as a one-time program to protect salmon during severe drought, not a change in hatchery policy. They’re prepared to scrap the plan if the coming weeks bring significant rain.
“We don’t want to truck them down if conditions aren’t going to be as bad as we think they’re going to be,” Clarke said.
Officials developed the plan in consultation with the fishing industry, which has been pressing for the trucking plan for weeks.
“What this means is we’ll likely have a much better salmon fishing season in 2016, when these fish reach adulthood, than we would have otherwise gotten,” said John McManus, executive director of the Golden Gate Salmon Association.
Read more here: http://www.sacbee.com
Widely consumed North Sea species, including haddock, whiting, herring, and others, have shrunk in size by as much as 29 percent over nearly 40 years, as water temperatures have increased between one and two degrees Celsius, researchers from the University of Aberdeen in Aberdeen, Scotland, revealed in a study published in the April issue of Global Change Biology.
Intense fishing pressure or low food supply may also contribute to smaller fish, but lead author Dr. Alan Baudron says concurrent size declines in different schools of fish points to climate change as a smoking gun.
“What is interesting is this was detected across a range of fish species eating different diets, living at different depths, and experiencing different levels of fishing mortality,” said Baudron.
The “synchronicity suggests that the one common factor they all experienced—increasing water temperatures—could have been at least partly responsible for the observed reductions in length.”
Baudron and his team analyzed age and length data—collected by the International Councils for the Exploration of the Sea—from commercial fish caught between 1970 and 2008.
Not all species experienced a decline in size. Cod sizes were not affected, and female sole only shrank by 1 percent. Exactly why is unclear.
“Disentangling the effects of these factors can be extremely difficult,” Baudron said.
So just how could a subtle change in temperature over several decades impact the size of a vast variety of species?
Baudron says the reason is that most fish grow more rapidly during their early life when temperatures are cooler. As oceans warm, young fish, known as juveniles, become mature at a smaller length, they don’t grow as large as they would have in colder water.
David Conover, professor of Marine Science in the School of Marine and Atmospheric Sciences agrees higher temperatures are the most likely the cause.
“It’s well known from theory and experiments that animals in warmer environments do generally tend to grow to lower maximum sizes, so the data match model predictions,” he says. But that data only shows correlation, not causation.
“Other factors like fishery-induced evolution could also be contributing.”
Indeed, warmer water does not be the sole culprit. A study published in 2012 in Nature Climate Change also found that climate change has contributed to less oxygen in the oceans. The result? Fish with smaller body sizes.
“We were surprised to see such a large decrease in fish size,” said the study’s lead author, William Cheung, of the University of British Columbia, in a statement. Marine fish are generally known to respond to climate change through changing distribution and seasonality. But the unexpectedly big effect that climate change could have on body size suggests that we may be missing a big piece of the puzzle of understanding climate change effects in the ocean.
This Saturday – March 15th, from 10:00am until noon.
Bring in your vise and tying tools, and tie along with us. Learn tips, tricks, and the special techniques for tying amazing flies that will help you catch more fish.
You will tie alongside Urban Angler shop employees, local guides, and well known tyers in the fly fishing industry.
These clinics will cover a range of regional and seasonal fly patterns. From local specialty patterns to unique flies for exotic species.
Space is limited, so arrive early and have fun. Tie one on!