Featured Scientist

Moccasin Creek Hatchery Manager Justin Kroeze


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.

CDFW Photos

Setting a trap on the West Fork San Luis Rey River.


Collecting sample for tissue analysis, San Diego River.


Creating spawning beds for rainbow trout, Sweetwater River.

Russell Barabe is a coldwater fisheries biologist based out of CDFW’s South Coast Region office in San Diego. Though he grew up San Jose, where his mom was a nurse and his dad was a facilities maintenance supervisor, Russell’s family frequently went camping and trout fishing in Shasta County. Russell was an Environmental Studies student at San Jose State University when a summer internship with the Student Conservation Association introduced him to researching fire effects at different national parks. He was hooked on the idea of working in the great outdoors as much as possible. A Master’s degree in fisheries biology at Mississippi State University put him on the path to becoming a CDFW biologist, where he’s been employed since 2009. His first duties included enforcing lake and streambed alteration regulations.

You’re a west coast guy – what was it like completing your education at Mississippi State?

It was really cool working in the Southeast and seeing fisheries from a whole different perspective. Down there, largemouth bass are native; same with bluegill, greenfish, sunfish, and catfish. I actually studied the recovery of catfish in the coastal rivers after Hurricane Katrina. We were tagging catfish and doing mark-recapture, and then we did a full-on age analysis of flathead catfish in the Pascagoula River, which is one of the largest, last remaining undammed watersheds in the lower 48.

As a fisheries biologist based in San Diego, what does your job entail?

My primary areas are San Diego and Orange County, and I was recently assigned to the Sespe Watershed, which is all the way up in Ventura County. I do a lot of monitoring of coldwater fish populations. That includes rainbow trout, both native and non-native. I also monitor other native species like Arroyo Chub. If something goes sideways, then we come to the rescue.

What’s an example of something going sideways?

Another fish population I monitor down here is the Unarmored Threespine Stickleback. Last year we had a really large storm event come through and this population of fish is right out on the edge of the Anza Borrego Desert. This storm came through and dumped a whole bunch of rain in a short period of time and ended up washing a lot of sediment into the stream. By doing that, it made the whole stream really shallow. Later in July and August, the water started percolating into the sand and there was no habitat for the fish. Because we were going to lose these fish if we didn’t do something, we got approval to do a rescue. We went out there and grabbed as many of the fish as we could and took them to another area where we can get them to water. Fully grown, that fish might be two inches long.  

San Diego is known for its ocean fishing opportunities. Do you find that people are surprised to hear there’s a coldwater fisheries biologist in the San Diego area? Can you describe the rivers and streams where you work?

San Diego is unique. I’ll talk with my colleagues up north who do work for the Heritage Wild Trout program as well. They have rivers that are 50 to 100 miles long and they sample little sections and then extrapolate the numbers out to get an idea of what’s going on. In my case, I have a section up in the mountains that still holds native trout but it’s only four miles long. I’ll decide to go camp out there for three days and snorkel everything, because I can. It’s also very difficult work because there are no trails, you're basically hiking in a stream with a full backpack and you often fall down. You’re fighting through brush and poison oak, and of course there are ticks, ants and rattlesnakes.

A snorkel survey is pretty much as it sounds, right? Face down, on your stomach, in a cold river, trying to count fish?

Correct. We just put on the mask and we have a wetsuit and we put our face in the water. With a flashlight we look under every rock to count them and try and put them into size classes. We try and do that every year so that we can track the population and say, okay, in 2017 we saw 400 and then in 2018, we only saw 30.

How do you guarantee you’re not counting the same fish over and over?

First, we always snorkel in an upstream direction. Second, if the stream is wide, we use enough snorkelers to cover the whole width. Down here, two is usually enough. Third, you only count a fish once it swims past you downstream. This way if a fish swims circles around you, you do not count it each time. If you get to the head of a pool and the fish have not swam past you, you then count those fish. This technique can be difficult if a lot of fish are present, but in Southern California, this is rarely a problem. If using more than one snorkeler, communication is important to discuss if the fish that swam between us was counted by me or the other person.

Don’t fish tend to go the other direction when you make yourself very present like that?

The surprising thing is that most fish will tolerate you when you’re snorkeling. They'll look at you a little warily but as long as you don’t try to reach out and touch them they’ll swim near you. But if you get too close, they take off and go hide under a rock.

Is there a particular project you are proud of, because you know that your work made a difference?

I would refer to some work I did on the only population of native rainbow trout left in San Diego County. There had been a report there were non-native bullhead (catfish) found in that part of the stream system. Everyone was worried about the bullhead competing with the trout, so we went out there to get genetic samples for a project to try and look at the heterozygous study of that population. (Low heterozygosity means a lack of genetic diversity. High heterozygosity means high genetic diversity.)

We were camping for the night and I said, “Why don’t we bring out a couple of traps that we have, and we’ll bait them with cat food, and we’ll throw them out just for the heck of it and maybe we’ll catch a bullhead or two.” I thought it might make a small difference. We threw out the traps and ended up catching over 30 bullhead. I thought, this is interesting, this works! When I got back to the office, I dove into the literature to see if I could find anything about anyone doing anything like that. I found a couple of projects, but no references to someone using this specific trap or using a similar technique. So we designed a study where we would use a lot of nets and cat food, and go out on trips of three days. We’d set the traps overnight because bullhead are nocturnal. On the first day, we’d set the traps in the evening. The next day, we’d walk down the stream and set our next set of traps, and camp for the night. The last day, we’d pull out the traps and then hike out. That first year we did that, we ended up removing 1,300 bullhead.

The next year, I figured we’d need to go back and do it again because the chances we’d removed everything were pretty slim. But when we went back, we trapped the entire stream and we didn’t catch a single bullhead. We went back the year after that, and we still didn’t catch anything. Removal of this invasive species is likely to benefit the native rainbow trout through a reduction in competition and possible predation.

I submitted a publication based on that bullhead work and is currently in press. It’s supposed to come out sometime this year in the North American Journal of Fisheries Management. 

In a 40-hour week, how many hours are spent in those river settings vs. sitting at a desk and writing up reports?

I’m usually getting out three days a week. Because traffic can be so bad down here, travel times to a lot of these places is really tough. To get to that population of native trout I mentioned, it’s a two-hour drive. And then there’s another a two-hour hike to get to where the fish are. So it’s an eight-hour day just to get to and from where the fish are. I’ll do 12- to 16-hour days on a regular basis. It’s easy to fall behind on your emails and reports!

How would your job change if you had unlimited time and an unlimited budget?

Well, I’d love to have a helicopter to make it easier for my back country trips. Just drop me off and pick me up, that would be a great start! Every year this job gets harder. I’m 47 and I have a tech who’s 20 years younger than me. I can usually keep up with him … he might hike a little faster than me, but I’m not far behind!  

CDFW Photos