Fish - Ocean Central
Fish
Fish are vital to ocean health and resilience, playing essential roles in promoting biodiversity, balancing marine ecosystems, and supporting coastal habitats.
They contribute to carbon sequestration and cycling in both open ocean and coastal ecosystems, enhancing marine productivity. In turn, this productivity sustains global fisheries and supports the livelihoods of millions of people worldwide.
Fish by the Numbers
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62 Million Jobs
As of 2022, fisheries and aquaculture employed around 62 million people worldwide in various roles.
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5 out of 8 Tuna Species at Risk
Due to overfishing, five of the eight tuna species are globally threatened or near threatened. Blue and white marlins are vulnerable, while striped marlins are near threatened, emphasizing the need for sustainable fishing practices.
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16% of Total Carbon Flux
Fish contribute to an estimated 16.1% of carbon movement from the euphotic zone — the ocean’s sunlit layer — to deeper waters. This role in carbon cycling underscores their importance in climate regulation.
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Herbivorous Fish
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Migratory Fish
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Predatory Fish
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Forage Fish
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Deep-Sea Fish
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Cleaner Fish
Key Benefits of Fish
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Nutrient Cycling
Marine fish contribute to the cycling of nutrients within marine ecosystems. As fish consume food throughout their lives, they ingest essential elements like nitrogen, phosphorus, and iron. Some of these elements are retained in the fish body to build new biomass, which acts as a stored reservoir of nutrients, while the rest is excreted or egested, providing a recycling flux to water. These recycled nutrients support the growth of benthic organisms and phytoplankton, which forms the base of the marine food chain and is essential for the productivity of marine ecosystems.
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Contribution to Marine Carbon Flux and Sequestration
Fish play a vital role in the ocean’s carbon cycle by moving carbon through the water, helping the ocean capture and store carbon. Their deep-sea migrations and natural processes such as biomass production contribute to carbon sequestration, which helps regulate global climate patterns and mitigate the effects of climate change.
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Habitat Creation
Certain fish species, including reef-building fish such as parrotfish and damselfish, actively contribute to the creation and maintenance of marine habitats. They help shape and modify coral reefs, seagrass beds, and other ecosystems by their feeding activities, which can increase habitat complexity and biodiversity. Indeed, parrotfish are natural bioeroders that play a crucial role in maintaining the delicate balance of coral reefs. By grazing on macroalgae, they help control algae populations, preventing them from overwhelming the reef and competing with corals for space and resources. As they feed, parrotfish also create new surfaces on the reef, allowing baby corals to attach and grow. This process helps sustain healthy coral ecosystems, promoting coral regeneration and overall reef resilience.
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Coral Health
Many marine fish species are closely connected to coral reefs and play essential roles in maintaining the health of these ecosystems. Some fish, like herbivores, graze on algae that can otherwise overgrow and smother corals, helping to keep algae populations in check. Other fish species contribute to the dispersal of coral larvae, facilitating the growth and regeneration of coral reef systems. Together, these actions support the resilience and stability of coral reefs, ensuring their continued survival and ecological balance.
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Trophic Linkages
Fish link various components of the marine food web. Their movement and feeding behaviors connect primary producers such as phytoplankton with top predators including sharks, creating a dynamic and interconnected ecosystem.
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Predator-Prey Dynamics
As both predator and prey, fish regulate species populations within marine ecosystems, ensuring a balanced food web and preventing the overgrowth of certain species.
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Economic and Social Value
Fish are vital to global economies, serving as a key source of food and providing essential protein for billions of people. They support large-scale commercial fishing industries, generating employment and income, particularly in coastal regions. Fisheries and aquaculture play a significant role in creating jobs and supporting livelihoods in many coastal communities. Moreover, for many coastal and island communities, fish hold cultural and traditional importance, being embedded in local diets, festivals, and heritage. Fisheries and fish-related activities also serve as social bonds, connecting generations and preserving traditional knowledge.
Threats to Fish
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Habitat Destruction and Natural System Modification
Residential and commercial developments can severely impact marine habitats. Activities such as altered water flow, increased nutrient and sediment runoff, and pesticide use degrade marine environments. These disruptions harm marine ecosystems, leading to habitat destruction, pollution, and loss of biodiversity.
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Pollution
Pollution poses a significant threat to marine fish populations globally, impacting their health, habitats, and the overall balance of marine ecosystems. Pollution can enter a habitat in a variety of ways. Major pollution sources include oil spills, ship strikes and noise pollution, agricultural runoff and industrial discharge, and plastic pollution.
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Climate Change and Severe Weather
Climate change and severe weather driven by habitat shifts and alterations, storms and flooding, and temperature extremes also scored highly as a threat to marine fish populations. Climate change is likely to affect fish populations in several negative ways by reducing productivity or causing direct mortality. Known negative impacts include loss of habitat, decreased marine productivity, shifts in location of prey items and shifts in range and migration routes due to changes in ocean currents and sea surface temperature.
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Human Activities
The fast-growing practice of deep-sea mining and deep-sea trawling poses significant threats to important sea creatures, including fish. Deep-sea mining may offer a way to meet the world’s growing demand for certain metals, especially those used in electric vehicles and renewable energy components. However, evidence indicates that mining the deep ocean for these minerals has harmful ecological impacts and the potential to greatly disrupt many deep-sea habitats. A 2023 report published in Current Biology highlights these concerns, emphasizing that while deep-sea mining could provide necessary resources, it poses significant risks to marine ecosystems.
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Fishing and Harvesting of Aquatic Resources
Fishing, both intentional and unintentional, pose the greatest threat to marine fish populations. Bycatch, the unintended capture of non-target species, is particularly common in long-line, trawl, and gillnet fishing practices. For example, South African pelagic longline fisheries catch about 70,000 sharks annually. Overfishing of key species, both prey and predators, further destabilizes marine ecosystems, highlighting the urgent need for sustainable fishing practices.
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Invasive Species
Overall, the introduction of invasive alien species poses a serious threat to biodiversity and the stability of aquatic ecosystems. For instance, invasive alien fish species have significant ecological impacts, including the displacement and extinction of native species, alteration of trophic interactions, and disruption of ecosystem functioning. They can also introduce new pathogens and threaten the genetic diversity of native species through hybridization.
Taking Action to Protect and Restore Fish
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Area-based Conservation Approaches
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The establishment of marine protected areas, seasonal fisheries closures, and restrictions on shipping activities protect fish and other marine life from human activities.
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Habitat Protection and Restoration
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Undertaking restoration projects to revive damaged ecosystems is critically important, as is safeguarding essential habitats crucial for the reproduction and growth of fish such as mangroves, coral reefs, and seagrass beds. Moreover, state marine fisheries agencies should coordinate with other organizations to ensure that habitat restoration plans are developed and that funding is actively sought for their implementation and monitoring.
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Implement Sustainable Fishing Practices
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Science-based catch limits, selective fishing gear to reduce bycatch, and ecosystem-based management are key to sustainable fisheries. These practices help restore fish populations, protect biodiversity, and ensure that marine ecosystems remain healthy for future generations.
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Enforce Fishery Control Regulation
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Enhancing legal frameworks by implementing stricter penalties and fostering international agreements is crucial to discourage illegal, unreported, and unregulated (IUU) fishing. Additionally, promoting transparency by encouraging vessel registration and reporting increases accountability within the fishing industry. Together, these measures can significantly reduce IUU fishing and contribute to the sustainable management of global fish populations.
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Improve Water Quality
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Reducing land-based pollution through better agricultural practices, sewage treatment, and managing stormwater runoff can help maintain water quality, which is vital for fish populations.
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Raise Awareness and Education
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Raising public awareness about the importance of fish to people and marine ecosystems can encourage sustainable seafood choices. Engaging local communities — especially fishers and coastal residents — promotes responsible practices and fosters a collective effort to preserve marine resources for future generations.
Credits
- Carlos Duarte
- Vanesa Chalastani
- Letizia Valluzzi