By Alyssa Obester, Rob Lusardi, Sarah Yarnell, Ryan Peek, and Nick Santos

Fish need water. While minimum flows and other emergency-response approaches might save some fishes during crises, such “bucket-based” approaches are insufficient in the long-term. For example, biologists in the Owens Valley saved the Owens pupfish from extinction by translocating individuals via buckets; however, the underlying cause of this dire circumstance—low dissolved oxygen related to insufficient flow and limited understanding of habitat needs—remains a persistent challenge.  Understanding the needs of species forms a better basis for sustaining native fish. But developing this knowledge takes time and resources.

Despite decades of research, we have an insufficient understanding of flow needs for many native freshwater species in California. How much water is needed during summer to support resident native species, such as sculpin or pikeminnow? Or, how large must spring flows be to trigger Sacramento splittail spawning? Most knowledge of suitable flows is limited to salmonids or species listed under the US Endangered Species Act (for example, see Michel et al. 2021).

In terrestrial systems, the umbrella species approach is widely used to address management challenges where habitat needs of species are unknown, too costly or resource-intensive to assess. This approach seeks to protect habitat and life history needs of one or a few species (the “umbrellas”), expecting these efforts will confer protection to other species in the same area. For example, the Northern Spotted Owl has been used as an umbrella species, as it resides in old-growth forests, which also provides habitat to numerous co-occurring species.

What makes a suitable umbrella species?

Previous conservation efforts have selected umbrella species due to their legal listing under state or federal endangered species acts. Others have used a set of criteria, including spatial requirements, the role a species plays in the ecosystem or community it lives, and vulnerability of a species to decline or extirpation. Some conservation efforts rely on expert opinion. In most cases though, the umbrella species concept has been applied only in terrestrial systems and species have not always been selected using quantitative and defensible criteria.

In a recent study, we established an approach for selecting suites of freshwater umbrella fish species across California. We used information such as species ranges, life history traits, and climate change vulnerability scores to identify suites of umbrella fish species. In addition to these criteria, we used expert knowledge of nine ichthyologists from California to help develop our method and validate datasets and results.

How did we do this and what questions did we ask?

First, we used species range data from the PISCES database to divide the four regions of California (north coast, south coast, Great Basin, desert) into similar assemblages of species that were of a scale appropriate for management efforts (Figure 1).

Next, we used species life history (e.g., age at maturity, reproductive strategy), habitat preference, and physiological trait data from the FishTraits database to group species with similar traits within each assemblage. Then, within each group, we scored each species using information on species’ vulnerability to climate change and data availability (i.e., how well studied is each species) using information from Moyle 2011 and Moyle 2013. These scores helped us identify suites of umbrella species (example provided in Table 1) representative of species within each assemblage. This approach allowed us to identify 49 umbrella species for California (from 118 species).

Table 1. Suites of umbrella species for the Central Valley and Great Basin regions.

Suites of umbrella species identified in the study could be used to address two common challenges related to streamflow management in California. First, agencies like the California Department of Fish and Wildlife or the State Water Board could use flow needs from a suite of umbrella species to guide selection of important seasonal flow components (e.g., fall pulse flow, dry season baseflow) for flow management, rather than focus on streamflow requirements for a single species or a minimum flow threshold. Second, in areas with high species diversity, where streamflow requirements of individual species are unknown or too costly to identify, managing flows for suites of umbrella species is more likely to supply flows adequate to support the full assemblage of species present. In short, managing for the needs of suites of species using an umbrella approach reduces the time and resources needed to identify streamflow needs for all the species.

The current drought underscores the need to rapidly identify flows that protect fish and other aquatic species. Although specific instream flow needs of many species are unknown, managing for a subset of species (the umbrellas identified by our approach) could speed the process by focusing attention on the flow needs of a few species that confer protection to others.

Alyssa Obester is a senior environmental scientist in the California Department of Fish and Wildlife’s Instream Flow Program, Rob Lusardi is an ecologist and senior researcher at the UC Davis Center for Watershed Sciences and Assistant Adjunct Professor in Wildlife, Fish, & Conservation Biology, Sarah Yarnell is a hydrologist and senior researcher at the UC Davis Center for Watershed Sciences, Ryan Peek is an ecologist and senior researcher at the UC Davis Center for Watershed Sciences, Nick Santos is a Research Software Engineer at the Center for Information Technology Research in the Interest of Society (CITRIS) at the University of California, Merced.

Further Reading

Imbler, Sabrina. (2021). “Saved by a Bucket, but Can the Owens Pupfish Survive?” New York Times, 16 August 2021. https://www.nytimes.com/2021/08/16/science/owens-pupfish-pister.html

Michel, C. J., Notch, J. J., Cordoleani, F., Ammann, A. J., and Danner, E. M. (2021). Nonlinear survival of imperiled fish informs managed flows in a highly modified river. Ecosphere 12( 5):e03498. 10.1002/ecs2.3498

Moyle,  P.B.,  Katz,  J.V.E.  &  Quiñones,  R.M.  (2011).  Rapid  decline  of California’s  native  inland  fishes:  A  status  assessment.  Biological Conservation, 144(10), 2414–2423. https://doi.org/10.1016/j.biocon.2011.06.002

Moyle, P.B., Kiernan, J.D., Crain, P.K. & Quiñones, R.M. (2013). Climate change vulnerability of native and alien freshwater fishes of California: A systematic assessment approach. PLoS ONE, 8(5), 1–12. https://doi.org/10.1371/journal.pone.0063883

Obester, A.N., Lusardi, R.A., Santos, N.R., Peek, R.A. & Yarnell, S.M. (2021). The use of umbrella fish species to provide a more comprehensive approach for freshwater conservation management. Aquatic Conservation: Marine and Freshwater Ecosystems, 1– 17. https://doi.org/10.1002/aqc.3746

Pister, E. P. (1993). Species in a bucket. Natural History, 102, 14-14. http://www.nanfa.org/ac/species-in-a-bucket.pdf