Native fish species are facing 'double trouble'

As climate change reshapes landscapes across the world, native species face growing challenges.

Rising temperatures, altered water flows, and shifting ecosystems already disrupt many habitats. At the same time, biological invasions involving non-native species that move into new areas introduce added stress.

Until now, these two threats have mostly been studied in isolation. However, recent work by researchers at Oregon State University suggests that combining these forces reveals deeper risks.

Native species may lose more than just space – they may face extinction under the pressure of both climate and invaders.

Threat to native species

The study, published in the journal Global Change Biology, begins to close the gap between climate science and invasion biology.

“Climate change and biological invasions are increasingly affecting ecosystems globally,” said Ivan Arismendi, an associate professor in Oregon State’s Department of Fisheries, Wildlife, and Conservation Sciences.

“It’s critical to understand their combined impacts so that we can anticipate and adapt management strategies that account for shifting interactions between native and non-native species.”

The team focused on freshwater fish species in the Pacific Northwest, where warming waters and shifting rivers have changed aquatic habitats. Arismendi and his colleagues, Guillermo Giannico and Arif Jan, developed ecological niche models.

These models use environmental data to predict where species might live under current and future conditions. Their goal was to understand how overlapping habitats could intensify threats to native fish.

Warming forces fish to higher ground

The researchers studied two invasive species, namely smallmouth bass and northern pike, and two native species, the redband trout and bull trout.

These fish currently occupy different regions, but warming climates are pushing them all toward higher elevations, where colder water remains. Unfortunately, this movement may force them into closer contact, with serious consequences.

“Cold water refuges in upstream areas will serve as converging zones for native and non-native fishes,” said Jan, a doctoral student at Oregon State.

“Past research has documented predatory interactions toward salmonids by smallmouth bass and northern pike, where their habitat overlaps. This means potential year-round predation and competition pressures during the early life stages of salmonids.”

The team found that future climate conditions will reduce suitable habitats for all four species. But more alarming was the increase in habitat overlap. In these shared zones, invasive species may outcompete or prey upon native ones, pushing already vulnerable populations closer toward collapse.

Native species disappear, invasives take over

This situation is not hypothetical. Similar patterns have already emerged in places like southeastern Alaska, where native salmonids have disappeared from areas invaded by northern pike.

The combination of climate-driven habitat loss and biological pressure creates a dangerous feedback loop. As conditions worsen, natives lose the space and time they need to adapt or recover.

The implications of this research reach beyond the Pacific Northwest. As temperatures rise and weather patterns shift globally, many regions will experience similar overlaps between native and non-native species.

The model developed by Oregon State researchers can help other scientists and managers assess risks elsewhere.

Planning with smarter conservation tools

“This study highlights the need for integrated management strategies that address both direct and indirect effects of interactions among species,” said Giannico, a professor of fisheries at Oregon State.

He emphasized that the framework used in this study is simple and cost-effective. It can help conservation teams prioritize areas for early detection of invasive species and focus resources where they are most needed.

Rather than reacting to individual threats, this new approach allows planners to anticipate problems before they escalate. It opens the door to broader ecological forecasting, where climate models and biological data work together. With better tools, conservation can become more proactive and efficient.

Growing challenges and an uncertain future

While the study deals with fish, its lessons apply across ecosystems. Forests, grasslands, and wetlands all face pressure from changing climates and invasive species.

As these challenges grow, species will shift, compete, and in some cases, vanish. Understanding how these forces interact gives us a chance to intervene.

The Oregon State researchers offer a glimpse of a future that is both uncertain and urgent. Their work reminds us that climate change does not act alone. It invites disruption. When non-native species follow, the result can be devastating.

But with clear science and thoughtful planning, we may still help native species survive the changes ahead.

The study is published in the journal Global Change Biology.

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