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GJW Direct 2020

Sharks, rays, and climate change: Impacts on habitat, prey distribution, and health

by NOAA Fisheries 19 Jul 19:50 UTC
The oceanic whitetip shark's scientific name—Carcharhinus longimanus—comes from its long, rounded pectoral fin (Longimanus translates to “long hands”) © Andy Mann

Climate change has significant impacts on marine ecosystems, including warmer ocean temperatures, ocean acidification, and increased severity and frequency of storms.

These shifting conditions can have critical effects on the health and distribution of marine species. As these climatic events intensify, predatory species like sharks and rays are shifting their geographic distributions based on prey and habitat availability. Their complex and variable life histories mean that climate change will impact individual species differently, making it important to understand species-specific vulnerabilities and needs.

In 2023, NOAA Fisheries celebrates the 50th anniversary of the Endangered Species Act, which has put many species on the path to recovery. Since it was enacted, no listed marine or anadromous species have gone extinct. However, climate change will continue to make the recovery of endangered species more challenging. Through climate-focused science and management, we aim to better understand the potential impacts of climate change on endangered species to foster their recovery into the future.

Oceanic whitetip shark

In parts of their range, oceanic whitetip sharks already face pressure from commercial fishing through bycatch and illegal fin sales. Warming oceans could further threaten their populations by altering the distribution and quantity of their prey and limiting the availability of their preferred habitat.

Oceanic whitetip sharks prey primarily on large, pelagic fish and squid that are also affected by climate-induced ecosystem changes. Many prey species rely on nutrients spread by offshore circulation and upwelling. These ocean processes are regulated by changes in temperature. As the ocean warms, prey species will need to migrate to follow the nutrient cycles. If prey is insufficient, oceanic whitetip sharks will need to move with their prey to survive.

While this species prefers warmer surface waters, they are cold-blooded animals and will dive deep to regulate their body temperature if they become too warm at the surface. Their movements between deep and shallow waters cycle nutrients throughout the water column, enhancing ocean productivity. Increasing ocean temperatures are likely to affect their movement patterns and may also affect their ability to maintain sufficient body temperatures. Behavioral changes in top predators like these sharks could have cascading impacts on populations of other species and on the function and health of the ocean.

In 2018, due to significant population declines caused by bycatch and illegal fin sales, NOAA Fisheries listed the oceanic whitetip shark as threatened. Recovery of oceanic whitetip sharks is challenging. They are long-lived, late maturing, and have low to moderate reproductive rates. Protection from further decline is critical to their long-term survival. With the help of our partners, NOAA Fisheries is implementing an interim recovery program. These efforts aim to slow population decline and include research into best methods for the safe release of individuals accidentally captured during commercial fishing operations. The interim recovery program also involves gathering species-specific habitat and life history data that will guide the implementation of effective protective measures both domestically and internationally.

Scalloped hammerhead

Scalloped hammerhead sharks rely on shallow, coastal areas such as bays and mangroves for essential breeding habitat. As adults, scalloped hammerheads occupy both coastal and offshore ocean waters. Adult females move inshore to give birth to live young (pups), who then remain inshore during their early life stages. Their dependence on coastal habitats makes scalloped hammerhead sharks particularly vulnerable to climate change impacts.

Pups and juveniles in inshore nurseries are the most vulnerable to natural and human-caused threats. Intense storms and flooding can increase freshwater runoff and sedimentation. These environmental changes impact water temperature, alter nutrient cycles, and decrease productivity in coastal nursery areas, affecting young sharks at a sensitive life stage. Scalloped hammerheads also face added pressure from international commercial fishing, mainly for the shark fin trade. Recovery from these multiple threats is challenged by the sharks' slow growth rates and late age at maturity.

In 2014, NOAA Fisheries listed four distinct population segments of the scalloped hammerhead:

  • Endangered: Eastern Pacific
  • Endangered: Eastern Atlantic
  • Threatened: Central and Southwest Atlantic
  • Threatened: Indo-West Pacific

The Northwest Atlantic and Gulf of Mexico DPS and the Central Pacific DPS are not currently listed under the Endangered Species Act, but are managed under the Magnuson-Stevens Act.

Giant Manta Ray

The giant manta ray relies on large quantities of microscopic animals called zooplankton for food. As ocean temperatures increase, offshore circulation and upwelling patterns will shift, impacting the spread of nutrients that support zooplankton populations. Resulting changes in zooplankton availability could affect the behavior and health of giant manta ray populations. For example, shifts in seasonal migration patterns to feeding grounds and nursery areas could have profound impacts on the species' survival.

Additionally, some giant manta rays use reefs as cleaning stations where small fish remove parasites and dead or diseased skin from their bodies. As sensitive reef habitats degrade due to climate-driven changes, the abundance of cleaning stations and cleaner fish may be reduced. The loss of cleaning opportunities can hinder the giant manta ray's ability to reduce parasitic loads and dead tissue, leading to increased disease and reduced survival.

Giant manta rays are targeted by artisanal fisheries for meat and for their valuable gill rakers. They are also frequently caught as bycatch by commercial and artisanal fisheries. In addition, giant manta rays are particularly susceptible to microplastic ingestion, as well as vessel strikes and entanglement in marine debris, mooring lines, and fishing lines. This species has reduced ability to recover from these pressures because they give birth infrequently to low numbers of young.

As a result in 2018, NOAA Fisheries listed the species as threatened across its range. NOAA Fisheries has developed a recovery outline for the giant manta ray that provides a preliminary strategy for conservation of the giant manta ray. Through a combination of research, coordination with our partners, and outreach and education, NOAA Fisheries aims to reduce immediate threats to giant manta rays and their habitats.

Responding to climate change

Shifting environmental conditions result in ever-increasing challenges for marine species. NOAA Fisheries is committed to our mission to conserve protected species in the face of the many threats posed by climate change. With our partners, we have taken a series of steps to advance climate-focused science and management including:

  • Climate vulnerability assessments for marine species to understand which species are most vulnerable and why
  • Scenario planning to address uncertainties, predict impacts, and prioritize mitigation and recovery actions
  • Climate-smart conservation training to educate staff on how to implement climate adaptation tools in their work
  • Launching the Advanced Sampling and Technology for Extinction Risk Reduction and Recovery (ASTER3) program to prevent extinction and promote recovery of protected species through transformational technological advances
  • Developing the Climate, Ecosystem, and Fisheries Initiative (CEFI) to build ocean models and provide climate-relevant information that supports decision makers as they prepare for and respond to changing conditions.

These initiatives strengthen our understanding of the impacts of climate change on protected species and their habitats. We'll use this world-class science and data in our climate-informed actions to enhance species' adaptations and resilience to changing conditions in the next fifty-plus years under the Endangered Species Act.

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