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Hatcheries face climate change consequence

Concerns around climate change are increasingly being felt in the aquaculture industry, ranging from how these changes affect natural fish reproduction to hatcheries’ ability to rear species effectively.

July 12, 2019  By Tom Walker

Concerns around climate change are increasingly being felt in the aquaculture industry

Todd Pearsons, senior fisheries scientist with the Grant Public Utilities District in central Washington state in the U.S., spoke about strategies to mitigate the impacts of climate change on trout and salmon hatcheries in his presentation at the 69th Northwest Fish Culture Concepts last December.

“Most of us have read papers and heard a lot of talk about the predicted climate change effects on salmonids,” says Pearson. “We know that stream flows will change dramatically in terms of when they come off and the amount of water running. When you combine this with warmer drier weather, water temperatures will be higher and water levels will be lower.”

These factors will challenge the ability of fish to rear naturally in some areas they have historically, Pearson adds, and they will also challenge hatchery operators in the same locations.

Water woes
The first concern is simply water availability. “It is becoming more challenging to keep our intakes in the water during higher spring flows,” says Pearson. “And then we can have water levels drop later in the year, so an intake can go dry.”

Pearson adds, they may need stronger intakes to be able to deal with higher flows and more debris coming down. Having a back-up source using a portable intake will also be important.

“Having flexible water rights and multiple sources so you can access sufficient ground and surface water in the future is going to be really critical,” he says.

Making the best use of the water that you have will become a higher priority, Pearson notes.

“When I poll this room I find that maybe 20 percent of hatchery operators are currently using some form of recirculation,” he says. “One-pass water is going to be a luxury of the past. We need to be focusing more on water recirculation for water conservation.”

“The ability to imprint fish on water that is not adjacent to your hatchery is an area of research we need to focus on, because we may not have the acclimation sites we do right now,” Pearson adds.

Temperature control will become increasingly important. “We need to provide the capability for plenty of cold water,” says Pearson. “This might mean that we are going to need to recirculate more of our water so that we can keep it cold by running it through chillers.”

Insulation of vessels and piping, and providing more shading and cover, will also be necessary. “We may need to do more over-winter acclimation at remote sites, if our core sites are warming up,” Pearson adds

Fish collection
The effects of climate change may also lead to increasing challenges in gaining access to broodstock.

“If we have a lot of stream drying in the future, we are not going to be able to collect target broodstock in areas that we have collected them in the past,” Pearson notes.

“We might need to collect fish at downstream locations where there is more water, and tissue identification approaches will be needed to identify and segregate the genetic lines that we need.”

Another factor to consider is that phosphorus discharge may become a bigger issue in the future if there are lower volumes in receiving water. “That means we are going to have less dilution of the amount of phosphorus that we are discharging into the system,” Pearson explains.

“Being able to produce things like low discharge feeds and having more efficient ways to get the feed to the fish so that we have less phosphorus being discharged into the environment will be needed.”

In some cases, hatcheries may even need to produce smaller size fish, so there is less discharge into the environment, he adds.

Change is inevitable
All of these factors will now be part of the process when selecting a site for a new hatchery Pearson notes.

“It is likely in the future that successful hatchery locations are going to be limited to mainstem areas or spring fed locations where we know we have good access to water,” he says.

Historical numbers on previous drought and flood intervals may no longer be useful in selecting new locations, Pearson says. Taking a more predictive approach will be key.

“We are probably not going to be able to tinker our way out of this,” Pearson says. “We are going to have to have changes in policy and different ways to operate our hatcheries in order to make some of these kinds of things work, and we are going to have to change the way we implement policy.”

The good news, Pearson says, is that hatchery operators have more than a century of experience in adjusting hatchery conditions for the benefit of fish.

“We should just expect this and plan to do the hard work and the science up front,” says Pearson. “We need to be proactive in developing these strategies, so that when we actually need this stuff, need it to be on the ground, we are ready.”

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