Salmon migration routes discovered using historical data

The North Pacific Ocean serves as a vast, natural laboratory for understanding the complex ecology of salmon, a crucial species both ecologically and economically. Recent research from the University of Alaska Fairbanks has greatly enhanced our understanding of salmon migration behavior at sea.

This study integrates decades of international research on salmon, offering new insights into their migration patterns and temperature preferences.

Supermap for salmon migration

Since the 1950s, various countries and agencies have conducted high seas salmon surveys. However, never before have these individual studies been amalgamated into a single, comprehensive database.

This large-scale integration allows for an unprecedented overview of the marine stages of salmon life cycles.

“This is a portion of the salmon life cycle that arguably gets overlooked, at least in terms of the grand investment in salmon research,” said Curry Cunningham, an assistant professor at UAF’s College of Fisheries and Ocean Sciences.

Professor Cunningham also shared his personal connection to the subject. “As someone who always wondered where all these fish went when they left Bristol Bay, seeing that pattern come to life was so satisfying.”

Salmon hotspots and migration

The compiled data includes over 44,000 gear hauls across the North Pacific, capturing more than 14 million salmon. This ocean-based data contrasts sharply with the more commonly studied river habitats, providing a broader perspective on salmon ecology.

Through detailed mapping, the researchers have pinpointed key areas where different salmon species congregate.

Notably, the maps reveal a gathering hotspot for Chinook salmon in the Bering Sea. They also track the migration routes of maturing sockeye from the North Pacific and Gulf of Alaska towards the Alaska Peninsula, navigating through passes into the Bering Sea throughout the spring and summer months.

Temperature tolerance and migration

“It’s not as if all these salmon are going to some party in the middle of the Pacific. This gives us a broad look at where they go,” explained Joe Langan, the study’s lead author and a postdoctoral fellow at UAF during the project.

This comprehensive mapping of salmon not only clarifies migration paths but also sheds light on the varying temperature tolerances among species.

For instance, sockeye and chum salmon thrive in temperatures just a few degrees above freezing, whereas coho and steelhead avoid the coldest waters. Chinook and pink salmon occupy the middle range of these temperature extremes.

Future of salmon in a warming world

These findings hold particular significance in the current context of climate change, highlighting the critical role of temperature tolerances in shaping how different salmon species might adapt to increasingly warming waters.

As global temperatures rise, aquatic ecosystems experience significant shifts, which in turn affect the habitat ranges and migration patterns of marine species. Salmon, with their varied migration and temperature preferences, serve as a prime example of how climatic changes can drive evolutionary and migratory adaptations.

Understanding the specific temperature ranges that different salmon species can tolerate provides essential insights into predicting their responses to environmental changes.

For instance, species thriving in cooler waters may face challenges as these areas warm, potentially pushing them to seek colder, deeper, or more northern waters, altering their traditional migration routes and times.

Conversely, species with higher temperature tolerances might expand their range, encountering new competitors and predators, which could impact their survival and reproduction.

Study significance

The research involved meticulous examination of historical data, some of which dated back to the 1950s. This required the retrieval of long-forgotten reports from various sources. Additionally, it involved their standardization and integration into a coherent dataset.

Skip McKinnell, a retired expert from the Department of Fisheries and Oceans Canada and a veteran of early high seas surveys, described the process as “more of a search and rescue mission rather than convincing anyone to provide their data.”

The collective efforts of these researchers have transformed the once scattered and isolated studies into a robust resource that enhances our understanding of salmon migration and overall ecology on a global scale.

Moreover, this research documents the fascinating life cycle of these important fish. It equips scientists and policymakers with the knowledge necessary to better protect them in a rapidly changing world.

The study is published in the journal Fish and Fisheries.

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