Wyoming Wildlife - June 2022

A pound of cure

Eggs are externally disinfected with iodine to minimize the possibility of infection by bacteria, fungi or parasites.

Wyoming Game and Fish Department hatcheries keep fish healthy from eggs to stocking.

Chris Martin/WGFD
6/1/2022 1:18:17 PM

In 1736, Benjamin Franklin advised fire-threatened Philadelphians that, “An ounce of prevention is worth a pound of cure.” The Founding Father was making the point that preventing fires was easier and cheaper than fighting them. This timeless advice also can be applied to keeping diseases and unwanted organisms out of fish hatcheries. 

The introduction of an infectious disease or invasive species could be devastating to a fish hatchery and immensely expensive for the Wyoming Game and Fish Department. Last year the department raised and stocked more than 6.5 million fish in 368 waters across the state. The majority of fish — cold-water varieties of trout — come from the department’s 10 hatcheries and rearing stations. To protect its investment, Game and Fish has strict biosecurity protocols in place at its hatcheries.

“Biosecurities are a list of measures and tight protocols that we enact to prevent spread of diseases or invasive species in a hatchery,” said Lars Alsager, superintendent of Game and Fish’s Dan Speas Fish Hatchery outside Casper. “A healthy hatchery starts with a plan and then sticking to it.”

 An important component of a hatchery’s biosecurity plan involves reducing stress in the fish. 

“Anything you do to a fish provides a level of stress,” Alsager said. “The more you can reduce the amount of stress, the healthier those fish are going to be.” 

One stressor by itself — such as high density, warm water, diet or a dip in oxygen levels — doesn’t make fish sick right away. But compounding stressors end up being the tipping point. “We work to prevent that from happening,” Alsager said. 

Identifying stressors requires attention to detail, knowing where a threat might arise and having a plan to stop the threat in its tracks. 

“We treat the hatcheries like an island,” said Guy Campbell, fish culture supervisor for Game and Fish. “How do you protect your island? If something comes up, how are you going to keep it from spreading? You think about this every day and you practice it every day.”

It starts with water

Fish do best in a healthy environment, and a hatchery is only as healthy as its water source. Water can become contaminated by fish waste, diseased fish and outside influences like grass, predators, water contamination, organic build-up and more. It's important that a water supply is tested regularly. Several Game and Fish hatcheries have highly-meticulous systems that use filtration and UV treatments to reduce threats found in the water. 

Goose Egg Spring supplies water to Speas Hatchery and was covered in 2009 to fully protect the water source. 

“It would grow watercress, moss and algae, and you could find frogs, fish and salamanders in it,” Alsager said. “Protecting the hatchery begins with its water source, and there’s no doubt we would have had a problem if we had not covered it.”

Ground water sources often are saturated with nitrogen, and too much can harm or kill fish. One way Wyoming’s hatcheries combat this problem is through using vacuum degassers. 

“Water is pumped into these degassers and is broken down into small droplets, which increases the surface area. This allows for nitrogen to be pulled off the water,” Alsager said. 

This process also removes oxygen, so low-head oxygenators are used to re-oxygenate the water to the level fish need. The process allows them to reuse the water. 

Thousands of fish in a hatchery produce a lot of waste, but dual drain circulars, drum filters and other equipment effectively remove the waste from the system. After the final use, water is plumbed into a settling pond or tank, which aids in the removal of suspended solids before the water is discharged back into the natural environment.  Even this discharge of waste water is done with the threat of diseases and invasive species in mind. 

“We want to prevent any animal from getting into the effluent ponds and making their way into a hatchery,” Campbell said. “We typically elevate the effluent discharge pipes 10 inches to a foot off the ground to ensure there is no water-to-water contact with outside water sources.”

Of course, what comes out of a fish is dependent on what goes into it. To ensure optimal health, Game and Fish gives high-quality food to its fish. That food is often in baked pellets of various sizes. Alsager said medicated feed can be used to treat infections when certain diseases are detected in fish. 

Any time fish are moved — from hatchery to hatchery or stocked for anglers to catch — there can be a risk of introducing or spreading diseases and invasive species. Equipment used in fish transfers, such as trucks, nets, buckets and even employees’ boots could become infected. 

“When we stock fish, if any equipment comes in contact with water or mud, it gets properly disinfected,” Alsager said.  “If our truck comes in contact with water, we disinfect the truck — even the tires —  to prevent spreading diseases,” Alsager said. 

Preventing the threats

After two years of the COVID-19 pandemic most of us are familiar with the ease and rate at which a disease can spread in a population. Fish have their own diseases to contend with and fish in hatcheries are not immune to them. This is why Game and Fish requires each of its hatcheries to have an annual fish health certification. 

Certification is obtained by passing a veterinary inspection from the department’s Fish Health Laboratory. Each year, lab personnel collect fish from each hatchery for pathogen testing. A pathogen is an organism that causes disease and can include viruses, bacteria and parasites. Chapter 10 of the Wyoming Game and Fish Regulations requires annual testing for three bacteria, three viral pathogens and one parasitic pathogen at each hatchery. Pathogens vary in their significance, survivability, ease of spread and how they are controlled.

“Viruses can shut a hatchery down and change the landscape, so they are given high priority,” said Carl Smith, program manager for the department’s Fish Health Laboratory. 

Fortunately, the most common pathogen found in Wyoming is a bacteria, not a virus. Bacterial coldwater disease occurs naturally in the water sources for many hatcheries. Transmission can occur through the water column and through the eggs of infected adult salmonids. 

“This is the number one disease we combat at Speas,” Alsager said. “If we see fish mortality, we send fish to the lab for testing. They culture the bacteria, diagnose and prescribe medicated feed for treatment.”

Some pathogens can persist despite a hatchery’s best effort. A microscopic parasite called Myxobolus cerebrali causes whirling disease in fish and was discovered at Ten Sleep Hatchery during routine testing in 2008. The parasite infects young trout by burrowing into the cartilage in the skull. This affects the nervous system and equilibrium, causing an infected fish to swim in circles.

As a result Ten Sleep Hatchery was completely remodeled in 2011. New concrete vaults were built around the hatchery’s three springs to contain the water and exclude surface water. Large drum filters equipped with ultraviolet lights were installed to rid the water of pathogens, and other equipment was installed to condition the water for optimal fish health. 

Whirling disease also was found in the incoming water at Story Hatchery in 2005, which resulted in the hatchery ceasing its fish stocking program. Whirling disease is not transmitted from parents to offspring so Story Hatchery can still serve as a broodstock facility to provide fish eggs to the rest of the state. As an extra precaution, eggs are treated with iodine before shipping. 
When Wyoming trades trout to other states for warm-water fish such as catfish, there is potential for the spread of pathogens and aquatic invasive species. Therefore, any hatcheries Wyoming trades with must be certified both as disease and aquatic invasive species free. To provide an additional layer of protection fish managers perform a screening process on these fish to make sure no unwanted organisms are included in the shipment. 

Trading Wyoming’s hatchery-raised trout for warm-water species such as walleye gives anglers a diversity of species to pursue. But bringing fish into Wyoming from other states comes with the risk of introducing unwanted species. Fisheries biologists sort through the fish and remove anything that doesn’t belong. This involves gently moving the entire load of fish across a white board one bucket at a time. The white background makes it easy to spot unwanted organisms. These fingerling walleye came from Garrison Dam National Fish Hatchery in North Dakota a few years ago. (Photo by Robin Kepple/WGFD)

“Before fish are stocked, we hand sort and run the fish across a white plastic board. We remove any plant fragments, tadpoles, snails or non-target fish,” Campbell said. 

It’s a time consuming but vital process to ensure the state’s waters remain free of invasive species.

Predators such as raccoons, kingfishers and herons also pose a threat to fish in a hatchery. 

“Ideally, we would have all of our fish in buildings to protect them from predators,” Campbell said.

“But completely enclosed buildings are expensive. Currently, only a few of our facilities are set up this way, while several have three-sided buildings and others utilize bird netting over top of outside rearing units.” 

Humans are the final level of disease and aquatic invasive species prevention at a hatchery. Anyone who enters a hatchery building must follow the facility’s biosecurity procedures, including using disinfectant foot baths and hand-sanitizer stations at the doors. 

“They may have just been fishing before coming to the hatchery, or possibly wading in a river that might be positive with some type of pathogen that we don’t want introduced to the hatchery,” Alsager said. “So we ask them to use boot wash and hand sanitizer stations before entering.” Education is also important, and signs installed around a hatchery alert visitors of the risks of pathogens and invasive species.

The mere presence of people is stressful for fish reared in a hatchery tank because they have nowhere to hide from excited onlookers. Campbell said some hatcheries need to limit access to a certain area of the facility to give sensitive or sick fish protection from this stressor.  

Preventing diseases and invasive species from entering a fish hatchery is a round-the-clock job, and Wyoming’s hatchery managers hold a constant vigil to protect their charges. “We’re always alert to what’s going on,” Alsager said. “We are planners and strategists, and we try to stay ahead of the next ‘what-if.’ But if something does happen, we have a plan on how to move forward.”

— Robin Kepple is the Wyoming Game and Fish Department’s education and information specialist for the Laramie Region and is a regular contributor to Wyoming Wildlife.


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