FOR CENTURIES, people have built their lives around rivers and oceans. These

waters nourish our communities, fuel our economies and connect us to each other. Migratory fish provide one of these connections.

Moving between rivers and oceans, like salmon, or traversing

ocean paths, like tuna, migratory fish link regions across the planet and play an important role in the long-term health of freshwater and marine ecosystems. They also support commercial and recreational fishing industries, serve as an important source of animal

protein for people worldwide, and hold cultural significance for many tribes and nations.

These fish are especially vulnerable because their survival depends on a range of interconnected habitats, ranging from rivers to floodplains, coastal marshes, and open oceans. Engineered infrastructure, overfish-ing and other activities threaten populations of migratory species across the globe.

Guided by more than 60 years of hands-on, science-driven conservation, The Nature Conservancy works with local communities, fishers, industry leaders, policymakers, scientists, and other organizations globally to develop solutions that protect rivers and oceans while also providing social and economic benefits.

The value of fish migrationFor fish such as salmon, river herring, sturgeon, tuna, eel and some catfish, migration is key to survival. These species travel throughout their life cycle to feed and reproduce, and their journeys vary in length and frequency. Some migratory fish famously travel thousands of kilometers to spawn, while others move only a few hundred meters during annual migration between river channels and seasonal floodplain habitats. A number of these fish move exclusively in fresh water, others only in salt water, and still others move between both.

Salmon, for instance, migrate from rivers as juveniles to feed and grow to maturity in the rich productivity of ocean waters. They may stay at sea for several years before returning to spawn in the same

stream where they were born. Eels do the opposite, migrating from the ocean into fresh water where they spend most of their life before returning to the ocean to reproduce.

Migratory fish support food webs in lakes, rivers, estuaries and oceans, and their movement enables the transfer of nutrients across habitats. For example, salmon bring a flush of nutrients from the ocean that helps fertilize riverside trees and enables them to grow significantly larger.

Exposure to a variety of habitats also makes migratory fish excellent indicators of broad ecosystem health—underscoring their intrinsic value to people and nature.

Globally, fish provide almost three billion people with nearly 20 per-cent of their animal protein intake.1

When you consider rivers such as the Mekong—which supports the world’s largest inland fisheries—our dependence on migratory species is clear. Approximately 70 percent of its 2 million metric ton annual catch consists of migratory fish, providing the primary source of animal protein for tens of millions of people.2 Likewise, long-distance migratory fish like tuna are part of

Solutions that Support Migratory Fish

Fish provide almost 3 billion people with

nearly 20 percent of their animal protein intake.

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See our latest thinking on these and other issues at nature.org/global

Salmon, river herring and other migratory fish travel across rivers and oceans to complete their life cycle. While we depend on these fish for our food and livelihoods, many human activities impact them along their journey. Working with governments, industries and local organizations, The Nature Conservancy aims to find solutions that ensure people and nature thrive together.

Going the Distance for Migratory Fish

CHALLENGETo meet global demands for low-carbon energy, hydropower capacity is expected to double in the next three decades. Dams, however, prevent fish from swimming up and downstream.

SOLUTIONPlanning approaches, such as Hydropower by Design, identify ways to balance energy production with free-flowing rivers. On Maine’s Penobscot River, dam removals and fish passage improvements have helped species such as river herring surge from about 1,000 fish to 900,000, while maintaining energy levels.

CHALLENGELevees, floodwalls and other infrastructure reduce flooding. However, these structures block fish migration between rivers and floodplains. Infrastructure has disconnected about 90 percent of floodplains in rivers such as those in the lower Missouri and Sacramento river basins, leading to habitat loss for migratory fish, including salmon.

SOLUTIONReconnecting rivers and floodplains using a Floodplains by Design approach reduces flood risk and improves fish habitat. Projects in Washington’s Skagit Delta have restored marsh habitat for salmon and will return $9-20 million in economic benefits.

CHALLENGEFish provide a major source of animal protein for 2.9 billion people. But overfishing and bycatch have led to declines of many migratory species. Overharvesting of eels has caused European stocks to drop to 1 percent of their historic population, and also put a $12 million fishery in Maine at risk.

SOLUTIONDesigning fishing gear to reduce bycatch and working with fishers to set sound harvest rules can restore fisheries to sustainable levels. Innovative approaches to reduce bycatch of river herring in the U.S. northeast Atlantic allow fishers to avoid area closures and protect roughly $28 million in annual landing values of targeted fish.

CHALLENGEOur global population in low-lying coastal zones alone could reach 879 million by 2030. By developing coasts, riverbanks and floodplains, we shrink habitat that many migratory fish need to breed and grow.

SOLUTIONCoastal Resilience mapping tools help decision-makers integrate social, ecological and economic factors into coastal planning. Restoring hundreds of kilometers of estuary and river habitat is helping migratory fish such as the endangered Atlantic sturgeon. Juveniles have been observed for the first time in decades in the Chesapeake Bay.

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one of the world’s most lucrative fisheries, valued at US$10 billion annually.3

Migratory species hold cultural significance as well. For the Passamaquoddy, a tribe of North American Indians in Maine, fish such as the river herring are deeply embedded in their history, customs and beliefs. Fish migration is also cause for celebration in some Pacific Northwest tribes, with annual salmon harvests an important way to pass on traditional values to younger generations.

Challenges in rivers and at seaAlong their journey, migratory fish face serious threats. Three major challenges include physical barriers, overfishing and habitat loss.

Physical BarriersDams, levees, floodwalls and other infrastructure provide us with a variety of benefits from low-carbon energy to flood control. However, they also impact pathways critical to migratory fish. These structures restrict migration upstream and downstream in rivers, between rivers and oceans, and laterally be-tween rivers and floodplains. Dams can also alter natural patterns of river flow that are necessary for fish spawning and migration.

Hydropower dams present the most significant infrastructure challenge. In fact, recent research shows that completion of hydropower dams currently under construction and those planned will affect 300,000 kilometers of rivers globally through fragmentation or changes to river flow patterns.4

Consider this: in three of the world’s great river basins—the Amazon, the Congo and the Mekong—approximately 450 hydropower dams are planned or under construction.5 And all three of these basins support large harvests of migratory fish. Estimates on the Lower Mekong River alone show that dams could cost the region

up to US$274 billion in degraded resources, lost ecological services and other impacts.6

OverfishingIn 2012, world capture fisheries production accounted for 80 million metric tons of fish from marine waters and 11 million metric tons from inland waters—reaching fishery export values of nearly US$130 billion.7

But we know this catch isn’t sustainable. Many fish populations, including those of migratory species, have consistently declined over the past decades. European, American and Japanese eel populations are now threatened with extinction and the Pacific Bluefin tuna is down to only 5 percent of its historic population.8

Overharvesting of targeted fish is just one part of the picture. Incidental bycatch of non-target species during regular fishing operations also presents a signifi-cant threat to migratory fish. River herring are caught as bycatch in regular sea herring operations, and in longline tuna fisheries bycatch impacts non-targeted tuna species and a number of other marine life including sharks, sea turtles and seabirds.

Habitat LossDevelopment along rivers and coasts makes our lives easier in many ways, offering access to important resources. However, extensive alteration of river floodplains and coastal zones for housing, industrial, port and other infrastructure has degraded natural habitats critical to wildlife, includ-ing migratory fish. The Delaware River and its estuary, for instance, were once home to the largest population of Atlantic sturgeon on the East Coast. However, development of the sturgeon’s coastal habitat has left less than one percent of its historic spawning population in existence.9

Challenges on the Delaware are not unique. Urbanization,

coastal development and other land uses put pressure on our waterways globally, with runoff from agriculture, industrial and residential sources contributing to widespread pollution. Coupled with rising sea levels and other impacts of climate change, the breeding and nursery areas for migratory fish continue to shrink.

Better paths to successWorking with diverse stakeholders and partners, The Nature Conservancy has developed solutions that protect migratory fish while supporting communities, economies and ecosystems. We are applying these strategies around the world.

Hydropower by Design Identifying realistic and balanced development pathways is key to keeping more rivers intact and providing clean energy sources to people around the world. Our

“Hydropower by Design” approach allows us to protect or restore ecosystems by working with partners to re-operate existing dams, remove or avoid other dams, and better plan for dams that will occur in the future. We provide data, modeling tools and case studies to help decision-makers identify scenarios that allow for energy production while maintaining river connectivity. If applied to a significant portion of dams currently planned or under construction, this approach could potentially avoid impacts from dams on 100,000 kilometers of rivers globally.4

The benefits of this type of system-scale approach have been demonstrated in places such as Maine’s Penobscot River. As part of the Penobscot River Restoration Trust, the Conservancy and partners—including the Penobscot Indian Nation, government agen-cies, and other environmental

Migratory fish can benefit from solutions that balance nature with human development.

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organizations—implemented the Penobscot River Restoration Project. As part of the effort, two dams have been removed and a third features a new, nature-like fish bypass. This will increase migratory fish habitat by 1,500 kilometers10 and, already, species such as the river herring are showing dramatic increases.

Meanwhile, through equipment and op-erational changes at the dams that remain, the basin will generate the same, or more, electricity as it did before dam removal.

Floodplains by Design

The lands flanking a river, known as floodplains, provide important spawning and rearing habitat for migratory fish. However, floodplains are also attractive places for development and agriculture, and so, in many rivers, the majority of floodplains have become discon-nected by levees. Our “Floodplains by Design” strategy builds on promising examples that show that reconnecting floodplains can provide multiple benefits. These include storing and conveying floodwaters, reducing risk to cities and farms, and providing important habitat for fish, birds and other wildlife.

The value of this approach is evident in places like Fisher Slough, located in the Skagit Delta—the heart of Western Washington’s agricultural community. There,

the Conservancy worked with the National Oceanic and Atmospheric Administration (NOAA) and local diking and drainage entities to replace antiquated infrastructure. In addition to restoring marsh habitat for salmon, the project also helped lower flood risk for neighboring farms and homes.

Sustainable Fisheries ManagementRestoring fisheries to sustainable levels takes strategic partnerships and innovative science and technol-ogy. Partnering with fishers and in-dustry, we are creating business models and testing fishing gear that demonstrates economically viable and sustainable fishing practices. Likewise,we have developed tools to assess, monitor and manage data-limited fisheries (which represent 95 percent of the world’s fisheries11), many of which include migratory species. On-the-water demonstration projects also help shape regional, national and local policies that move fisheries from unregulated open access towards rights-based management, benefit-ing local fishers.

By piloting new technologies and methods, the Conservancy is working with partners including the Massachusetts Division of Marine Fisheries to help species such as the river herring. Studies indicate that a high number of these migratory fish are caught off the U.S. northeast Atlantic during targeted fishing for Atlantic herring and mackerel. A new

bycatch information system is helping fishers reduce accidental catch of river herring, effectively avoiding area closures that would impact economic returns of the targeted fisheries.

Coastal ResilienceDrawing from results of field-based studies and data around the world, the Conservancy and partners are mapping the benefits that coastal systems offer. Online

“Coastal Resilience” and “Mapping Ocean Wealth” tools empower decision-makers to determine where to restore or conserve critical habitat and increase the resilience of marine habitats and coastal communities.

These tools and the science underpinning them also advance the Conservancy’s work to restore and protect hundreds of kilometers of estuary and river habitat for migratory fish. On the Delaware River, the Conservancy and col-laborators such as Delaware State University have identified and made management recommendations for habitat conditions that support the endangered Atlantic sturgeon in each stage of its life cycle.

Join us in applying these solutions, innovating new approaches and realizing the scale possible through collaboration. Together, we can protect migratory fish, meet the global needs of our communities and economies, and safeguard the ecosystems critical to people and nature. nature.org/global

Endnotes1. FAO. 2014. The State of World Fisheries and Aquaculture. Web.2. Milton Osborne. 2009. “The Mekong: River Under Threat.” Lowy Institute for International Policy. Web.3. FAO. “Push to enhance management and conservation in tuna fisheries at high seas.” Web.4. TNC. 2015. The Power of Rivers. http://www.nature.org/media/freshwater/power-of-rivers-report.pdf5. K.O. Winemiller et al. 2016. Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong. Science. 08 Jan 2016; Vol. 351,

Issue 6269, pp. 128-129.6. Zaffos, Joshua. 20 Feb 2014. “Life on Mekong Faces Threats As Major Dams Begin to Rise.” Yale Environment 360. Web.7. FAO. 2014. The State of World Fisheries and Aquaculture.8. McCurry, Justin. “Overfishing fears cast aside as sushi boss pays $118,000 for single bluefin tuna.” The Guardian. 5 Jan 2016. Web.9. Breece, M.W. et al. 2013. Shifting distributions of adult Atlantic sturgeon post-industrialization and future impacts in the Delaware River:

a maximum entropy approach. PLOS One. 8:11 pp. 1-12 e-1832110. Penobscot River Restoration Trust. Project Overview. Web.11. Costello et al. 2012. Status and solutions for the world’s unassessed fisheries. Science. 2012 Oct 26;

338(6106):517-20.

Work on the Penobscot River will increase

migratory fish habitat by 1,500 kilometers.

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