Featured Scientist

  • October 9, 2020

Moccasin Creek Hatchery Manager Justin Kroeze

Fish Hatchery Manager, Justin Kroeze and his two daughters at the hatchery near the river with people fishing
Kroeze and his daughters during a fish planting outing

Nestled in the foothills of Tuolumne County, about an hour west of Yosemite, Moccasin Creek Hatchery raises several species of trout to stock in lakes and streams in half a dozen counties. CDFW Fish Hatchery Manager Justin Kroeze is responsible for overseeing Moccasin Creek Hatchery’s operations and supervising the facility’s nine employees.

Kroeze was introduced to the hatchery business at a young age by his stepfather Jim Groh, a longtime CDFW employee who retired as a senior hatchery supervisor. Groh worked at the San Joaquin Hatchery, Kern River Hatchery and Moccasin Hatchery. And his dad, Fred Groh, worked at the Kern River Hatchery, San Joaquin Hatchery, Mokelumne River Hatchery and Feather River Hatchery.

Kroeze started volunteering at hatcheries in 2003, and two years later he landed his first job with CDFW as a fish and wildlife technician at Moccasin Creek Hatchery.

Moccasin Creek Hatchery has recently faced challenges as a wildfire in late August almost forced the evacuation of staff and their families who live in state housing on hatchery property. Moccasin is also currently raising fish to help stock waters in the eastern Sierra following a bacterial outbreak in July that affected 3.2 million fish at three CDFW hatchery facilities.

What was it like getting the evacuation order due to the fire in August? 

The fire started about a mile-and-a-half from the hatchery. Seven families live in state housing at the hatchery, including my wife and two kids. We all got an evacuation order due to limited firefighting resources, so we all packed up our belongings and were ready to evacuate. My youngest was very upset. But we did not end up having to leave. We’ve experienced fires nearby before, and the wind tends to travel up the canyon which is away from us. We were pretty sure we were safe, but we packed up and got ready to go just in case.

One of the most challenging aspects of the evacuation order was that my wife and family needed me, but simultaneously I was coordinating with the other employees that live on the property to make sure their families and animals had a place to go. 

Moccasin is currently helping fill the gaps for several hatcheries in the eastern Sierra that lost fish due to a bacterial outbreak. Has helping those hatcheries been a rewarding experience? 

It has definitely been a rewarding experience. The state hatchery system has to work together to provide the best opportunities to anglers. When Moccasin was hit with a flood in 2018, the Fish Springs Hatchery gave us fish to help us restart. Now we have the opportunity to provide fish for their restart. It all comes around. Running a single hatchery is a big enough challenge as it is. If we don’t help each other it would be even more difficult.

What memories do you have growing up around hatcheries?

I have fond memories of going on fish plants 30 years ago with some of the crew members that used to work at Moccasin Creek Hatchery. I grew up living at Moccasin Hatchery in the state hatchery housing. My dad was a fish hatchery manager at the time and my mom was the office technician. I’m now raising my daughters in one of the hatchery houses I lived in as a kid.

Where does Moccasin Creek Hatchery typically stock fish? How is this year different?

Moccasin stocks Tuolumne, Mariposa, Merced, Stanislaus, Alpine, Calaveras, Alameda, Contra Costa, Mono, Inyo, Fresno, Madera and Sierra counties. Roughly 50 percent of the fish we stock go into our local county of Tuolumne.

This year we’ll be doing our normal catchable rainbow trout plants, but we won’t be doing golden trout air plants due to COVID-19.

Fish hatcheries play an important role in CDFW’s efforts to stock fish throughout the state, but how they work is a mystery to much of the general public. What would you say are the biggest misconceptions about hatcheries?

I think there’s a misconception that trout hatcheries are funded from tax revenue. Our trout hatcheries typically do not receive money from the general fund. We’re funded directly from fishing license sales. When people buy a fishing license, a percentage of that license fee is actually contributing to growing fish and putting fish in the water so people have the opportunity to catch them.
We also get people stopping by the hatchery wanting to buy fish directly from us. We don’t do that. We stock public waters and give people the opportunity to catch fish.

What’s the key to raising healthy fish?

The key to raising healthy fish at our facility is having clean, cold water and low densities, meaning we make sure the fish aren’t too crowded. Genetics is also a huge component. Maintaining diverse genetics within our state’s brood programs results in healthier fish. If you’re starting a brood program from wild fish, it’s critical to have what we call a good spawning matrix. CDFW geneticists look at the genetics of each individual fish and cross the two fish that are going to create the most diverse genetics.

What’s the biggest challenge to raising healthy fish?

In the past, it was getting quality fish feed, but in recent years our feed manufacturers have gotten really good at putting out a high-quality product. The newer feeds are very palatable, easily digested and packed with ample vitamins, fats and proteins which aid in the fishes’ growth. Because the feed that’s manufactured these days is a lot more efficient than what we used to have, we’re producing healthier fish with less feed than we used to.

Staying ahead of fish diseases within the hatchery can be challenging. It takes close daily observation of each group of fish and working with our state’s Fish Health Lab when we notice any abnormal behavior from the fish or signs of disease.

What skills do you need to work at a hatchery?

You can take classes on fish culture, but for the most part our employees learn right here at the hatchery. Since we can teach fish culture, we like to hire employees who have a diverse skillset, including mechanical abilities. A lot of our employees have carpentry, electrical and welding skills. There’s a lot of science to raising fish, especially in the last 10 years with the new advances in fish culture techniques. But a science degree is not a requirement for working at the hatchery, especially for our entry level classifications.

Do fish have different personalities?

Yes, they definitely do. There’s a big difference in personality between the domesticated rainbow stock that we have here vs. trying to raise non-domesticated strains of trout. The domestic rainbow trout swim right up to you because they’re used to being hand fed. Brown trout swim away from you, which makes them less efficient because they’re swimming away from a food source. So domestic fish are easier to raise and grow because they’re more efficient eaters. Non-domesticated strains of trout can get used to you after a certain amount of hand feeding.

For several years our hatchery raised Lahontan cutthroat trout, which is a genetically distinct native species. They were escape artists. If one fish found an opening in a tank cover, then a bunch of them would find it. I haven’t seen that behavior from other types of fish.

What would you like the public to know about hatcheries?

First, it takes time to grow fish. The eggs we’re hatching right now won’t be stocked as fish until nearly two years from now. Second, our goal is to produce as many fish as possible and to give the fishing community the greatest opportunity to catch them. Sometimes due to budget constraints and other environmental factors there’s only so much we can do, but we want anglers to know we’re committed to providing as many angling opportunities as we can.

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