Fishing removes key nutrients from marine ecosystems

Industrial fishing has been a huge food source for decades. It pulls enormous amounts of marine organisms – and their stored nutrients – out of the water every year. Scientists say these activities are tied to the loss of important nutrients that help keep aquatic systems alive.

This observation gained traction when experts found that modern fishing habits remove a significant share of these valuable elements from coastal and open-water habitats.

This research was led by Adrian Gonzalez Ortiz, who carried out this work while completing his master’s degree at Utah State University.

Gonzalez Ortiz teamed up with collaborators from the Sea Around Us initiative and other institutions to analyze the chemicals stored in the bodies of commonly fished species.

Fishing shifts ocean nutrient balance

Fisheries focus on certain species based on demand and convenience. A targeted approach can shift the balance of nutrients like carbon, nitrogen, and phosphorus, which are vital for marine food webs.

The researchers looked at landings across hundreds of locations worldwide. They uncovered patterns of nutrient removal that coincide with shifts in fish population structures in those regions.

Fish loss weakens nutrient circulation

Estimates suggest more than 400 million tons of carbon alone were taken out through industrial catches over a span of many years. Even trace losses matter because fish play a part in passing these elements around the oceans.

“Fish and other marine organisms contain specific nutrients in their bodies,” said Gonzalez Ortiz. Capturing species that hold a lot of these elements may lower the supply that keeps ecosystems resilient.

Mid-sized fish hold more nutrients

Medium-sized fish – often called mesopredators – have been singled out in the data. They act as hunters and prey, forming a key link for energy and nutrient movement across food webs.

“They store higher proportions of carbon, nitrogen and phosphorus, compared to other trophic groups,” said Dr. Trisha B. Atwood, associate professor at Utah State University.

These fish supply nutrient-rich prey to top-level predators, so removing them weakens both ecosystem function and future fishing prospects.

Impacts on different regions

The study tracked major changes in coastal zones and the open sea. Some coastal waters, such as parts of Southeast Asia, recorded striking extraction rates of nutrients over the past few decades.

In other areas, catches dipped after an initial boom, leading to fewer nutrients being taken out of those spots. This pattern sometimes pushed fishing fleets to head for new territories, where harvesting rose and nutrient removal climbed as well.

Fish removal changes ocean productivity

Nutrient extraction is not just about the fish that people eat. By removing organisms with crucial roles in cycling phosphorus and nitrogen, fisheries can change local productivity in ways that might be overlooked.

“This not only negatively impacts the ecosystem but also fisheries,” said Dr. Atwood. Fish often bring vital substances to shallower waters, and taking them out removes those chemical supplies.

Looking at possible solutions

Experts are studying how fisheries management might adapt to curb nutrient losses. Reducing overfishing and giving depleted stocks time to bounce back could help shore up the element flow in some regions.

Stricter catch limits or seasonal bans might lessen the strain on the most affected species. A balanced approach could keep vital trophic levels healthy and ensure that fishing can continue to support global demand.

Cascading effects in the ocean

Some officials believe that new guidelines could protect fish populations and ocean nutrients. Others say that improved data collection on the basic chemistry of these creatures might spark better policies.

Changes in the nutrient makeup of the ocean can ripple through entire systems. That may impact everything from coral reefs to large migratory predators that need nutrient-packed meals.

Research can guide better fish policies

Researchers are calling for more local studies that look at the fish in their habitats. That includes examining the full dietary range of predators and how smaller fish pass crucial chemicals around.

Most management rules focus on tonnage alone. Adding information about nutrient composition could paint a clearer picture and keep fisheries more sustainable over the long term.

Measuring success in fisheries

Many governments are revisiting how they measure success in fisheries. Some are exploring integrated methods that consider not only the biomass of fish but also the distribution of chemical elements needed to keep the waters productive.

The research team hopes that updated approaches will spur better evaluations of ocean health. “Such a decrease in catches resulted in fisheries expanding to other ocean areas,” said Dr. Maria ‘Deng’ Palomares, manager of the Sea Around Us.

Nutrients and long-term ocean health

Overlooking the chemical side of fishing could lead to unrecognized risks for marine environments. Solutions will likely require precise data, careful planning, and perhaps more restraint in how we exploit aquatic resources.

Stakeholders from the fishing industry and environmental groups acknowledge that balancing needs of people and nature is tricky. This evidence hints that a closer look at key nutrients may give leaders a sharper tool for preserving fish populations.

The study is published in the journal Communications Earth & Environment.

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