Featured Scientist

Jennifer Hemmert, Biologist


Survey to assess native rainbow trout at Marion Creek (left to right: Russell Barabe, Tawny Hoemke, Kerwin Russell (Riverside-Corona Resource Conservation District), Paul Nutting, Jennifer in water)


Loading native rainbows rescued from West Fork San Gabriel Creek (Jennifer in truck, Yoselin Caliz, Lauren Hall)


Adult native rainbow trout from Marion Creek


Offspring rainbow trout from Marion Creek

Jennifer Hemmert has taken an interesting route before landing with the Department of Fish and Wildlife as a wild trout biologist and experiencing a career highlight of saving a species of fire-threatened fish three different times. Born in Ohio and a graduate of Ohio State (yes, she is a huge fan of Ohio State football), she has worked in medical research and at a marine park in Hawaii called Dolphin Discovery.  Later she worked for the environmental non-profit group Sierra Nevada Alliance as an AmeriCorps member, UC Davis and the state Department of Water Resources. With CDFW since 2012, Jennifer’s trout biology work is done in Riverside and San Bernardino counties.

When did you first know science was a possibility for your career?

Believe it or not, it goes back to grade school. I had an incredible science teacher in the fourth grade, and I knew that biology was my passion. It was his encouragement because he said any student can follow their passion, and if that passion is in math, science, or engineering, one could really shape the future. And so, it goes back to my grade school teacher, Mr. Seas. As a kid, I thought I was going to be either a marine biologist or a veterinarian; I always knew I wanted to work with animals. Also, my focus on fisheries is integrated with my childhood of spending time up on a small lake on the border of Ohio and Indiana. We would spend our summers there fishing, boating and swimming.

What’s a typical day for a wild trout biologist in California?

I work under the Heritage and Wild Trout Program and our mission is to protect the habitats and fish populations within our designated areas throughout the state. We also create recreational opportunities for anglers related to trout fishing. The work is weather-dependent, and in the winter months I am working on reports. There is a seven to eight month window that starts in the spring for field work and we go out in crews of four to six people to do fisheries and habitat assessments on streams in San Bernardino and Riverside counties. We have backpacks that use electric shock, to stun the fish in the streams, and crew members net the fish and place them into buckets. Then we take weight and length measurements on those fish before returning them to the waterway. We are checking on not just the size but also the health and condition of the fish. Through a larger survey, we block the stream with nets and we use the collected electrofishing data to arrive at population estimates.

People might think of those areas as being in the desert. How prevalent are trout and streams in those counties?

As we head south in the state, the quantity of water decreases due to the arid nature. But in the higher elevation streams, there once was historical connectivity for fish to the ocean before humans changed the landscape for the conveyance of water. There were native populations of trout in waters before humans began creating dams and concreting waterways. Some of those populations still exist here in the State and Southern California. The department also creates recreational opportunities by raising trout in two large hatcheries nearby and placing them into waters for anglers. We have two streams designated as wild trout streams. There is Bear Creek, a tributary out of Big Bear Lake, which connects with the Santa Ana River. The second wild trout stream is Deep Creek, which is in the San Bernardino National Mountains and meets up with the Mojave River.

What's the biggest challenge for fish being able to do well, grow and thrive in your region?

A lot of it has to with quantity and quality of water. For fish to thrive, they need cold water and enough water. In times of drought, they can survive extreme and severe habitat changes caused by climate change, but sometimes they need a little help from our staff. Fish are resilient to adapt. They often are challenged by habitat problems that are related to forest fires in fire affected areas.

Since you brought that up, can you talk about an amazing achievement following the Holy Fire in 2018?

The Holy Fire was located in Riverside and Orange counties. Although I’m a fish biologist, I watch forest fires intently and weather forecasts – things not necessarily related to fish, or the biology and species themselves.  There had not been a fire in that area for 30 or 40 years, and a lot of vegetation had grown in and was extremely dry. Since the practice of keeping record of where fires burn, there is no information available that Coldwater Canyon had ever had a forest fire. We knew this was an area that would burn very hot and very fast. This fire moved from ridgeline to ridgeline throughout the stream corridor. We work closely with the Forest Service, which studies the amount of sediment that will move through a watershed during a large rain event. It was determined there would be up to hundreds of thousands of cubic yards that would move within most of the surrounding canyons burned by the fire in both Riverside and Orange counties.  We needed to move fish from that corridor into our hatchery system.

Which stream did you need to move fish from?

The fish were moved from Coldwater Creek in the Cleveland National Forest, where there was a native trout population.  Pre-drought, the population was estimated between 1,000-1,500 trout, and post drought about half of that number survived after four years of these dry conditions. The population estimate was between 400 and 500 fish post-fire, so it was determined we would remove half of the fish from the stream, taking everything we could safely electroshock, and move them into the Mojave River Hatchery.

Did that area have the displacement of debris they were anticipating?

Yes, there was a very large rain event that moved a lot of material into the waterway, as the canyon hillsides had no living vegetation to stabilize now exposed soils. That stream had a chocolate milk appearance after the heavy rain and these fish would have struggled to survive because they would be overwhelmed by the debris. Fish suffocate due insufficient oxygen passing across their gills and the floating sand particles in the water disorientate the fish.

These fish were moved more than once and that’s pretty unusual isn’t it?

Yes, it is unusual. A lot of times fish are taken to a nearby watershed that is not burned. In this case, due to the severity of this fire the nearby habitat was not suitable, so we moved them to the hatchery. Those fish stayed there for about six months before we had a few mechanical issues and had to do an emergency evacuation into Marion Creek in Riverside County, near the town of Idyllwild. We were monitoring the fish in Marion Creek, and were ecstatic to see that they had enough gravel for spawning and were able to naturally reproduce. But it was another dry year and we knew the stream water was significantly decreasing, so in early November we moved them back into Coldwater Creek. The habitat had improved and was suitable again for the fish to be moved back to their home.

How are they doing back at Coldwater Creek?

The habitat is repaired. We have aquatic invertebrates, and we have a lot of willows and vegetation that provide shade, so water temperatures are cold. This year we are looking forward to seeing if we have reproduction and we will assess what the population numbers look like. I want to add that this was done by an entire team of biologists and others from Fish and Wildlife, the Forest Service from both the Cleveland and San Bernardino National Forests, and Riverside Corona Resource Conservation District.

Changing gears a bit, if you weren’t a fisheries biologist what would you have done for a career?

I have always wanted to be a scuba instructor. In my personal life, I scuba dive off the coast of California, Mexico and Hawaii. I always thought I might live and work on an island, where I can have my toes in the sand, watch the sunrise and sunset, and swim with sea life. I have traveled to Honduras twice to scuba dive, plus have done dives in freshwater lakes since I was certified. Alternatively, I also wanted to be a boat captain on possibly a sailboat/dive vessel. After I retire, who knows what and where my next work adventure will take me, but I am sure it will involve water.

What’s the thrill that comes with scuba diving?

A lot of scuba divers like to see the big apex predators that are in the water. But for me, it is all the little fish and little invertebrates, and to be quite honest, seahorses are my favorite. I mean turtles are awesome to see as well as stingrays and sharks, but for me, it is all the little fish. I like seahorses the most.

What’s the attraction to sea horses?

As a child I would always draw seahorses, it was kind of an obsession. I would doodle them all over my notebooks. I am fascinated with how they sway with the currents. They attach themselves with their tails to grasses and their mate and just wave with the currents. They can be camouflaged, colorful and beautiful and are just intriguing to me. Fun facts are that they eat constantly, are horrible swimmers, and mate for life. While these points make seahorses more fascinating as a species, one more critical fact to remember is that ecosystems for all marine life need to be healthy and protected. Pressing threats, such as increasing ocean temperatures and trash as our global marine debris accelerates, continue to be growing problems.

CDFW Photos

While conducting beach seine surveys for surf zone fish at Año Nuevo State Marine Reserve, Chenchen Shen and researchers from Moss Landing Marine Laboratories found a juvenile salmon shark washed up on the beach.

Marine Protected Areas Management Project staff from Eureka, San Carlos, and Los Alamitos come together for a meeting at USC’s Wrigley Marine Science Center on Catalina Island (from left to right: Sara Worden, Amanda Van Diggelen, Steve Wertz, Mike Prall, Chenchen Shen, Becky Ota).


Chenchen Shen on a research fishing trip with CCFRP at Point Lobos State Marine Reserve.


Ocean Salmon Project and Groundfish Management Project staff return from a successful fishing trip along the San Francisco coast (from left to right back row: Melodie Palmer-Zwahlen, Traci Larinto, Melanie Parker, Joanna Grebel, Caroline McKnight, Melissa Mandrup, Alex Letvin, Barry Miller, John Budrick; from left to right front row: Chenchen Shen, Jennifer Simon, Andrew Klein, Vanessa Gusman, Marci Yaremko, Brett Kormos).


Chenchen Shen and Marine Protected Areas Management Project co-worker Sara Worden representing CDFW and conducting public outreach at an event celebrating the 50th anniversary of Fitzgerald Marine Reserve, a San Mateo County Park located within the Montara State Marine Reserve and Pillar Point State Marine Conservation Area.

Scattered along the coast of California lies a network of 124 protected marine and estuarine waters. These Marine Protected Areas (MPAs) encompass around 16 percent of California’s state waters from Oregon to the US/Mexico border. MPAs have different classifications, such as State Marine Reserve or State Marine Conservation Area, but they all have the same goal: to protect and conserve marine life and habitat in accordance with the Marine Life Protection Act. CDFW is the lead management agency overseeing the MPA network pursuant to the Marine Managed Areas Improvement Act.

The MPA Statewide Management Project is run by a small team of dedicated staff within the Marine Region. One of these staff is Chenchen Shen, an environmental scientist working out of San Carlos in the San Francisco Bay Area. Chenchen’s focus is on MPAs from the Sonoma Coast down to San Luis Obispo. She joined the Department in 2017 and worked for the Ocean Salmon Project for two years before joining MPA Management. CDFW is a member of a larger collaborative MPA Management Program.

Chenchen grew up in the Bay Area and completed her undergrad at Princeton University before earning her PhD at Oregon State University.

What piqued your interest in biology and marine ecosystems?

Both of my parents work in medical science and my interest in biology stemmed from their influence. I was originally leaning towards the medical field, but as I went through the coursework from cells to ecosystems in high school biology, I found myself more interested in biological systems that are outside the human body and affect how the environment works. That led me to pursue an undergraduate degree in ecology, followed by a PhD specializing in rocky intertidal marine systems.

A lot of people grow up wanting to become a marine biologist, drawn to the big things like sharks and whales and coral reefs. I was like that too, but in college I got an internship at the Bermuda Institute of Ocean Sciences that provided me with a different perspective. During that internship I measured the nutrients in sea water and investigated how phytoplankton would grow in different nutrient environments. That really helped me gain an appreciation for the small, unseen things in the ocean and understand it from the bottom up.

How did you get started with CDFW?

I like doing research, but I always wanted to do something more applied and focused in conservation and management after grad school. That’s how I ended up at CDFW, where science plays a central role in dealing with on the ground issues balancing resource use with conservation.

What exactly is the MPA Management Program?

In 2012, California created the nation’s first statewide ecologically connected network of MPAs. The network is globally recognized for its highly collaborative, transparent and iterative planning process guided by the advice of scientists, stakeholders, resource managers and interested members of the public from 2004 to 2012. It is one of the largest ecologically connected MPA networks in the world. After the network was established, the MPA Management Program was created to address four main management tasks: research and monitoring, outreach and education, enforcement and compliance, and policy and permitting. CDFW works with many partners to implement this program, including the Ocean Protection Council, state and federal agencies, tribes, the MPA Collaborative Network, an array of academic researchers and many others.

The MPA Network is adaptively managed, and the program is set to be reviewed and evaluated by the Fish and Game Commission every 10 years. We’re approaching our first decadal management review in 2022, so we’re currently getting ready to compile information from each of the program’s four focal areas and assess what we’ve learned. Although we have some regional reports from baseline studies that were conducted in the past, next year will be the first time we get reports back from statewide long-term monitoring projects. Early results from baseline studies include some positive trends, such as greater numbers of black rockfish, lingcod and cabezon in kelp forests located in MPAs compared to similar locations outside MPAs along the central coast. It will be exciting to compare the new data with the baseline data and provide an update on how our MPAs have been doing. It will be a very big milestone for our project, CDFW and the State of California.

What is a typical work day like for you?

My work is incredibly varied. I coordinate with many different partners on all sorts of MPA management issues and support their work. I receive research updates and proposals that require review and feedback. I do outreach, such as writing and reviewing two blog series that are published on the CDFW Marine Management website. I am also working on utilizing the California Recreational Fisheries Survey data to help get a sense of how MPAs have affected fishing and how historical fishing levels affect MPA efficacy.

Since the pandemic, I have been working from home. People might assume that I do a lot of field work, but MPA monitoring is contracted to outside researchers and not conducted within the department. With our handful of staff, we don’t have the capacity to deploy multiple full-blown research programs on a statewide scale. We maintain relationships with the MPA monitoring groups so if they need help in a specific area where we have staff available, we go out and help with those efforts, during a normal year. Instead of specializing in particular species or habitats, our team gets to sample a bit of everything.

What is your favorite part about working with the MPAs?

California is a global leader when it comes to MPAs, because of our ecologically connected network. I like working on something that’s so pioneering, where there is a lot to learn. I also really love the diversity of the topic area, covering many different habitats and species as well as looking into the relationship between people and MPAs. And I find that working with many internal and external partners on MPA management is very rewarding because it creates a feeling of being part of a greater whole.

But working with so many different people must be challenging in its own way…

Yes, I’d have to say the hardest part of my job is managing such a big network with limited capacity and reliance on many partners. It’s challenging to keep up with everything that is going on, so there are always missed opportunities when it comes to meetings, outreach events, collaborations and publications. It is a big arena, and while we know we can’t do everything, we also don’t want to get lost as the managing agency for the network.

What are the challenges facing the MPA network?

One existential issue is the fact that we’re really invested in these MPAs but they can’t solve everything. Climate change and its associated problems, like marine diseases and invasive species, are threatening marine ecosystems everywhere and MPAs do not create an invisible forcefield against these stressors. While we realize there are limitations to what MPAs can do, we have gathered a working group of scientists that has been researching how MPAs may contribute to climate resilience, what we still don’t know, and how to get closer to some answers. A report of their findings and recommendations will be available next year.

Another challenge is getting the word out to the public about MPAs. Unlike with state parks where there are clear boundaries on land, MPAs don’t have a marked boundary around them to distinguish them from the surrounding waters. It’s hard to gain an appreciation for, or even recognize, something you can’t see. More communication about MPAs and the science behind them is essential to the success of the MPA Network.

Speaking of public awareness and involvement, how can the program attract more people from diverse backgrounds and how do you feel about diversity within the program overall?

As an Asian American, I feel that diversity is lacking within our field. However, the field is becoming more aware of this lack of diversity, especially with the current social justice movement.

I think many people in the field were introduced to nature and the outdoors by their family, but my family and friends growing up were pretty “indoorsy”, and I think that is fairly typical of many non-white and immigrant communities. I approached my career path from more of an academic angle and my appreciation for nature grew from there. Outdoor education for kids, especially for underrepresented groups, may help inspire a more diverse generation of environmental stewards.

We have to ask: What is your favorite intertidal species?

I always get really excited when I find an octopus, which doesn’t happen very often, so it’s a special treat. They’re so mysterious and smart. They can change color and texture to blend in with their surroundings or to communicate, and they’re crazy escapists. The intertidal often looks uninteresting at the surface, but the more you learn about it, the more you discover it is full of clues, hiding spots, competing forces and change.

CDFW photos

Brian Olson holds up a Trinity Lake smallmouth bass. Brian grew up in Weaverville, Trinity County.


Brian, his wife, Ami, and their daughter, Juniper. Ami Olson also works for CDFW as the coordinator of the Regional Conservation Investment Strategies Program (RCIS), which encourages regional conservation planning in restoring, enhancing and reconnecting wildlife habitat.


CDFW’s Comprehensive Wetland Habitat Program team assess habitat at Little Dry Creek, part of CDFW’s Upper Butte Basin Wildlife Area. From left, Environmental Scientist Kelsey Navarre, Environmental Scientist Jeff Kohl, and Brian Olson. Not pictured is retired annuitant Bill Cook, the former manager of the Los Banos Wildlife Area.


Brian Olson shows off the results of a successful turkey hunt.

CDFW Photos

Brian Olson is the CDFW’s Comprehensive Wetland Habitat Program coordinator. He leads a four-person team tasked with preserving, restoring and enhancing California’s wetlands – on both public and private land – for the benefit of wildlife. Born in Redding and raised in Weaverville, Brian holds a bachelor’s degree in wildlife, fisheries and conservation biology from UC Davis and a master’s degree in avian sciences, also from UC Davis. He joined CDFW in his current role in 2015. He is based in West Sacramento.

Why do we need to manage wetlands in the first place?

We have a lot fewer than what we’ve had in the past and still have a lot of wildlife that depend upon them. Over the past 150 years, we’ve lost about 95 percent of our wetlands in the Central Valley. Thus the relatively few remaining wetlands that we have are important, and we need to manage them in a way that maximizes their value for waterfowl and other wetland-dependent species.

How do you go about improving wetlands for CDFW?

Our primary role – and the reason for the creation of our program – is to serve as a mechanism for CDFW to accomplish the wetland protection, restoration, enhancement and management objectives of the Central Valley Joint Venture, which is a coalition of state, federal and private entities that helps guide conservation actions for this region. Our program is designed to work with both private and public wetland managers. After this fall, we’ll have about 85,000 acres of private lands under management agreements where we compensate landowners in one form or another to manage their lands in accordance with plans we put together with them. And then we also work with another 150,000 acres of public lands. That includes all of our major wetland wildlife areas throughout the state. I look at us as being consultants of sorts, helping wetland managers with management plans and annual work plans, helping them with wetland projects, and helping them with funding and just wetland and upland management issues in general. 

Our ability to help folks manage wetlands relies heavily on a network of partnerships that have been developed over decades, many of which pre-date my time here at the department. Whether that’s CDFW wildlife area managers, private landowners, other government agencies such as the U.S. Fish and Wildlife Service, nonprofits like Ducks Unlimited and California Waterfowl and others like the California Rice Commission, Audubon, UC Davis, resource conservation districts and mosquito and vector control districts. We couldn’t do any of the things we do without the help of our many partners.

Why would a private property owner want to partner with CDFW on wetland management?

First, they are getting a free wetland consultant for their property. Better yet, they are getting a wetland consultant that pays them to do things on their property that enhances its value for wildlife. Our California Waterfowl Habitat Program (aka the Presley Program) and the California Winter Rice Habitat Incentive Program both offer landowners an annual incentive payment to manage their land in accordance with cooperatively developed management plans.

How much money are we talking about here?

The amount we pay landowners depends on the type of habitat they provide. On a per-acre basis it ranges between $15 and $60 per acre. We had $10 million available for our last round of funding for the Presley Program. That money came from Proposition 68, a voter-approved bond measure.

What are some of the biggest challenges you are facing these days?

For our public areas, it is largely funding and capacity for ongoing management. We’ve got a lot of land to manage with limited resources. For private land, it’s also largely funding. We had about double the properties apply for this last Presley solicitation than what we had funding for, so there is a significant opportunity to expand. Recruitment of wetland managers is also challenging. There doesn’t seem to be as many folks interested in doing this type of work – or at least their applications aren’t making their way to us when positions become available.

Waterfowl season is well underway. What can hunters expect, habitat-wise, when they head out to hunt the different public areas?

In the Sacramento and San Joaquin valleys, things are looking pretty good. Initially, it wasn’t looking like we were going to have the water we needed to manage wetlands optimally in these basins, but it ended up being OK, with reservoir inflow being just barely high enough in the spring for us to receive an adequate water supply. Due to this, both our seasonal and semi-permanent wetlands in these areas look pretty good this year. The public wetlands up in northeastern California don’t have the water storage that we have to work with in the Central Valley and are much more reliant on natural hydrology. These areas didn’t get as much water as we would have liked and are not looking as good this year.

Regardless of location, it was a tough year to do wetland management. As someone who hunts the wildlife areas myself, I want to mention how much I appreciate all the additional effort staff from our wildlife areas and the U.S. Fish and Wildlife Service put in this year to make sure we could access these wildlife areas and the national wildlife refuges. They put in safeguards and physical distancing measures, and came up with a COVID-19 plan that complied with state guidance so that public areas would remain open and folks could come out and enjoy the resource and these beautiful places.

California’s population of wild mallards has declined. Is there anything you can do from a wetland management perspective to help mallards specifically?

The focus of wetland management in California tends to be on seasonal wetlands in the fall and winter – and for good reason. We’ve got the highest concentration of wintering waterfowl anywhere in the world. But for certain species such as mallards, gadwall and cinnamon teal, we’ve got to be thinking about life cycle needs outside of wintering habitat. Close to 70 percent of the harvested mallards in this state are born and raised in California, so if we want more mallards, then we need to focus on growing them in California. One of the things that we can do to help is to provide semi-permanent or reverse-cycle wetlands where water is out there at a different time than these seasonal wetlands. It’s important to have that water out on the landscape from late March, early April through July. Getting this habitat on the ground has become more of a priority for the Central Valley Joint Venture and, as a result, it was a big part of this last Presley solicitation. Private properties that were willing to provide it received extra points in the scoring process, and we offered a higher incentive payment to private landowners to provide that type of habitat. 

And why is wetland habitat from March through July so important?

For ducks, it’s primarily for duckling survival. Statewide, we are pretty limited on brood-rearing habitat. It’s particularly important, especially early on in the brood-rearing period for waterfowl, to have productive wetlands out there. It’s critical for brood survival and super-critical for other wetland-dependent species like tricolored blackbirds. I’d argue the biggest benefit of having this type of wetland on the landscape is for other wetland-dependent species. These spring and summer flooded wetlands are some of the most species-diverse wetlands we have and are absolutely critical to many threatened species like giant garter snakes and tricolored blackbirds.

What first brought you to CDFW and what keeps you here?

I love managing habitat. It’s what I think about all the time, regardless of whether I’m working or not. Prior to CDFW, I was managing a fairly large private duck club with a few thousand acres of property in the Sacramento Valley. It was awesome, but I didn’t have the connection to our public lands that I wanted. I think what brought me to the department was my daughter being born. She’s 5 now and I wanted to preserve as much of this resource and opportunity for her as I could.

Hunting license sales are up in California this season and we have a lot of new hunters out there who might want to give duck hunting a try. What is it you love about duck hunting that you could share with them?

I started duck hunting when I was 7, but what really got me got me addicted to ducks and duck hunting was my first trip to the Sacramento Valley. When you get several million birds in one place, it’s a pretty awesome spectacle. It’s not really a describable feeling; you have to get out there and experience it. Even if folks don’t want to hunt but just want to go sit in the marsh, it’s pretty special. 

Away from work, where are we likely to find you?

In a normal year, probably hiking, hunting, or fishing with friends and family. The specific activity really depends on the time of year. If it’s spring, I’m probably turkey hunting or fishing. If it’s summer, I’m probably fishing, camping, or backpacking. In fall, I’m usually deer or elk hunting, and in winter, I’m likely duck hunting, though I don’t hunt nearly as much as I used to. One of the great things about living in California is that there are a ton of outdoor activities to do year-round.