Welcome to our blog series, Research Highlights! On the second Monday of each month, we debut newly published fisheries research by our women of fisheries colleagues. If you have research you would like to highlight and share with our readers, submit a nomination form!

This Month’s Research Highlight:
King, K.B.S., M.T. Bremigan, D. Infante, and K.S. Cheruvelil. 2021. Surface water connectivity affects lake and stream fish species richness and composition. Canadian Journal of Fisheries and Aquatic Sciences 78:433–443.

Fisheries research often focuses on a single species or group of species (like sportfishes) and often within the context of a single system or suite of similar systems. These studies yield valuable information for decision makers, but some issues require us to take a broader, bigger picture approach. Issues like climate change, pollution, and land use changes, among others. An example of using a large-scale, multi-system approach is the subject of this month’s Research Highlight. Dr. Katelyn King is a Postdoctoral Researcher at the University of Michigan School for Environment and Sustainability and lead author of a recent study on the effect of connectivity on biodiversity in freshwaters and why this novel approach is critical to protecting these ecosystems for the future.

Declining biodiversity, or loss of species, is a global concern across all ecosystem types. A recent assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) which is based on a review of approximately 15,000 studies, estimates approximately 25% of species, nearly 1 million worldwide, are currently threatened and facing extinction. According to the 2020 report,

“The rate of global change in nature during the past 50 years is unprecedented in human history. The direct drivers of change in nature with the largest global impact have been (starting with those with most impact): changes in land and sea use; direct exploitation of organisms; climate change; pollution; and invasion of alien species.”

Dr. King and her colleagues are interested in studying factors that affect biodiversity among freshwater systems in order to better understand and protect them. As mentioned above, their recent work focuses on something referred to as connectivity. Connectivity here can be defined as the measure of a fish’s access to different freshwater habitats or systems. The more connected one system is to other systems, the greater opportunity fishes have to move between those systems. As these researchers determined, the more connected systems are, the higher their biodiversity or the greater number of species found. That makes sense given that some species move readily between systems, move during certain life stages, or move as a result of shifts in environmental conditions. The challenge is that the way fisheries scientists study fishes in these systems varies. The way we collect fishes in a lake versus a stream, for example, can vary by the gear we use, time of year we sample, and even the data we record. How can you standardize fisheries data across these systems when the sampling design and data collected vary so much? That was one of the biggest challenges these researchers had to overcome with their study.

Another challenge scientists often deal with is how to translate complicated data or results into an easy to understand product. How can we display information in such a way that could easily be interpreted by scientists and the public alike? For me, Figure 5 in this paper provides a good example on how to do this. In this diagram, we can see that most species can be found in both lake and river habitats but there is a group of species uniquely found in one or the other. A lot of data informed this figure, and the researchers dig much deeper in the paper, but this provides a good take home message: many fish species in this region can be found in both lakes and streams.

From this study, we know connectivity matters for species richness, but Dr. King doesn’t plan to stop there. She will be continuing her work to include other measures of connectivity, land use metrics, and presence of dams and other water control structures in future analyses. This work can have important implications for future efforts to protect these systems in light of a changing world. As Dr. King notes, “In the face of a changing climate, surface water connections will become even more important in maintaining fish biodiversity. For example, as species ranges shift, it will be important to understand how far they will be able to travel within a lake and stream network and whether cold-water species will be able to travel to ‘refuge’ lakes or streams without barriers.”

Using integrated approaches like the one employed by Dr. King and her colleagues is vital to answering some of the biggest questions we face today. Freshwater ecosystems are not isolated and independent from each other, but rather connected and part of a larger landscape containing pathways for fish movement. Through continued research into connectivity and its effect on biodiversity and sharing that information through easy to understand visuals, Dr. King is bridging the disconnect in science.  

The full manuscript can be found and downloaded here:
https://doi.org/10.1139/cjfas-2020-0090

IPBES Global Assessment Report on Biodiversity and Ecosystem Services:
https://doi.org/10.5281/zenodo.3831674