Why Care About Native Freshwater Fish?

Even with a strong El Niño year, there are no assurances the drought is over. Clearly we need a better plan for future droughts and that plan needs to include provisions for native freshwater fish. But why include native fish?

There are many reasons. Many feel that native fish have a right not to be driven to extinction for economic purposes. Indeed, enough people feel this way that this is Federal and state law. In addition, many native fish support human needs, such as providing food, recreational opportunities, future medicinal alternatives, economic well-being or purely aesthetic value. For species like salmon and trout, the benefits to humans are straightforward. But what of the many less charismatic species which naturally occur in the state? Do they matter? Is there any reason to keep them around, or can they be replaced with introduced species which more readily support human economic objectives?

Our recent studies on sculpin have introduced ideas which shed light on the discussion. Sculpin are small (10 inch max) bottom dwelling freshwater fish and one of the most abundant native fish groups in California. Most Californians are unaware of these fish. Between their small size, overall abundance and general unwillingness to take a hook, sculpin have largely been ignored. But this oversight helps make them special. Because they have been ignored, their history reflects the natural history of California’s waterways. By studying native fish like sculpin, we can learn which freshwater systems were historically connected/isolated and how long ago this occurred.

So how do we get this information? Fortunately it is stored in their DNA. An organism’s DNA contains the unique blueprint or code for that specific individual.

However the overall code for a species (group of inter-mating individuals) is largely the same, with only slight variations between individuals. Those variations directly reflect where the species is found and chance, both of which allow or prevent the code from being passed to future generations.

By matching specific variations to specific regions, we can trace how and when species were introduced to our systems and which show signs of historical connectivity. For example, some sculpin found in the Pit River (extreme northeastern CA) actually originated from the Snake River system in Idaho (over 400 miles away). The same data support geologic findings that the Pit River actually once flowed in the opposite direction of its current path today (~three million years ago).Variations inherent in the DNA structure of sculpin are also correlated with different ecological conditions. There is a reason for different sculpin in different areas. Each is adapted to local ecological conditions and part of a specific freshwater system. We rely on these systems to maintain, clean and filter our water and they work efficiently, with little expense. Thus the ecological and environmental “system” is the important idea here, composed of multiple species who have evolved to work together to produce these results. Sculpin are one of those participants, along with specific bacteria, aquatic vegetation, aquatic insects, and other native freshwater fish species. If we start removing parts of the system, eventually the native system will collapse. A freshwater ecosystem can be thought of as a game of Jenga. Sure, you can remove parts and the tower stays standing. But eventually, if you remove too many, the tower falls. And if you lose pieces and try and replace them with an alternative (let’s say Legos), is the tower nearly as sturdy?

Native freshwater fish and their supporting ecosystems are important. I am not saying we should stop everything to protect these fish, only that we consider their importance in water management plans as we go forward. After all, they are in decline, due to ascending human prosperity.

If we could glean this much knowledge from just one species group (sculpin), imagine what other information lies in the DNA of the dozens of other native species in the state. And with all of the changes we are making, such as dams, aqueducts, and reservoirs, California’s native fishes are increasingly vulnerable. Their decline not only risks losing a wealth of information on California’s rich past, but also indicates the well-being of some of our important freshwater ecosystems may not be stable.

Reproduced with permission from the UC Davis Center for Watershed Sciences California WaterBlog: californiawaterblog.com