Nomura’s jellyfish, scientifically known as Nemopilema nomurai, are among the largest jellyfish species. These colossal creatures can reach up to 2 meters (6 feet 7 inches) in diameter and weigh over 200 kilograms (440 pounds). Primarily residing in the waters between China and Japan, particularly the Yellow Sea and East China Sea, their populations have shown a marked increase in bloom frequency since the early 2000s. While jellyfish blooms have historically occurred, their recent surge in intensity and regularity presents significant challenges to marine ecosystems and human activities.
Impact on Fisheries
Nomura’s jellyfish proliferation has profoundly disrupted fishing industries, leading to substantial economic setbacks. Their immense size and sheer numbers can overwhelm fishing gear, often clogging and damaging nets. Instances have been recorded where the weight of jellyfish caught in nets was so extreme that it caused fishing trawlers to capsize, as seen with the Diasan Shinsho-maru in 2009 off Chiba. Fishermen must frequently clear nets of these gelatinous masses, increasing labor and reducing the time available for catching target species.
Beyond physical damage, Nomura’s jellyfish diminish fish catch quality and quantity. When entangled with fish in nets, their stinging tentacles contaminate the catch with venom, reducing market value by up to 70% or rendering it inedible. This contamination, combined with lower catch rates, results in massive financial losses. For example, in 2005, the Sea of Japan experienced an estimated 30 billion yen in damages to its fisheries due to these blooms. The Korean fishery industry has also observed decreases in catches and product value, with annual direct damages estimated between $68.2 million and $204.6 million depending on fishing gear.
Threat to Coastal Infrastructure
Large aggregations of Nomura’s jellyfish also threaten coastal industrial facilities that rely on seawater. Power plants, including nuclear facilities, and desalination plants are particularly vulnerable. These facilities draw in vast amounts of seawater for cooling systems or water purification, and jellyfish blooms can clog their intake pipes and screens. This obstruction reduces water flow, leading to decreased operational efficiency or even complete shutdowns.
Such incidents have been reported in regions like China, Israel, and Oman, where desalination plants and power stations faced disruptions due to clogged intake systems. Manual removal of jellyfish from these systems is often a challenging and hazardous task. Financial implications extend beyond immediate operational costs, including equipment repair, waste disposal, and lost production during shutdowns.
Ecological Disruption
The massive presence of Nomura’s jellyfish profoundly alters marine ecosystems, shifting the delicate balance of oceanic life. These jellyfish are voracious feeders, primarily consuming zooplankton throughout their life cycle. Their immense appetite means they compete directly with many fish species, especially juveniles, for this food source. This competition reduces zooplankton availability, impacting fish population survival and growth.
Nomura’s jellyfish also prey on fish eggs and larvae, adding pressure to stocks already challenged by overfishing. By consuming these early life stages, jellyfish impede fish population replenishment, contributing to their decline and preventing recovery. This dynamic can lead to a “jellyfish spiral,” where a decline in fish predators and competitors allows jellyfish populations to expand, further suppressing fish populations and altering the marine food web structure.
Managing Jellyfish Blooms
Addressing Nomura’s jellyfish blooms involves mitigation strategies and ongoing research. Physical removal methods are often employed, with fishermen or specialized vessels collecting jellyfish directly to prevent interference with fishing or infrastructure. Some regions have implemented jellyfish buyback programs, offering incentives for local fishers to remove the jellyfish.
Technological advancements include early warning systems that monitor oceanographic conditions like temperature, salinity, and jellyfish larvae presence to predict blooms. These systems provide advance notice, allowing industries to implement preventative measures and minimize impacts. Researchers also investigate potential uses for Nomura’s jellyfish, transforming a problem into a resource. This includes processing them for consumption in some Asian cuisines, where they are used in dishes or even ice cream. Studies also explore their use in agriculture as fertilizer or for extracting compounds with potential medical applications, such as collagen or joint disease treatments.