East China Sea

The East China Sea is a marginal sea of the western Pacific Ocean, bounded to the west by the Chinese mainland, to the north by the Korea Strait and Yellow Sea, to the east by the Ryukyu Island chain of Japan, and to the south by the island of Taiwan and the Taiwan Strait. Covering approximately 1,249,000 km², it is one of the largest marginal seas in the world and, measured by the value of cargo transiting its waters, one of the most commercially vital bodies of water on earth. The ports lining its shores — above all the Port of Shanghai — handle a volume of trade that dwarfs any comparable maritime zone, reflecting the extraordinary concentration of industrial and manufacturing capacity along China's eastern seaboard, the Korean Peninsula's southern coast, and the island of Taiwan.

The East China Sea connects two of the world's most economically dynamic regions: the Yangtze River Delta, home to over 100 million people and a GDP exceeding that of many major countries, and the industrial corridors of Japan and South Korea. The sea provides the only maritime exit for the enormous volume of goods produced in China's interior provinces and transported down the Yangtze and its tributaries to the coast. Shanghai alone handles approximately 47 million twenty-foot equivalent units (TEU) of container cargo each year — more than any other port on earth. Ningbo-Zhoushan, immediately to the south, is the world's largest port by total cargo tonnage.

Geopolitically, the East China Sea is the most contested maritime region in the Indo-Pacific. The Senkaku/Diaoyu Islands territorial dispute between Japan and China, overlapping exclusive economic zone (EEZ) claims, disputed oil and gas development in the Chunxiao/Shirakaba gas field area, and the Taiwan Strait question — which involves the sovereignty claims of the People's Republic of China, Taiwan, and the strategic interests of the United States — make this a zone of persistent political tension whose maritime dimensions are inseparable from global security calculations. For the maritime professional, a working knowledge of the East China Sea's geography, oceanography, key ports, and navigational hazards is indispensable for safe and efficient passage planning through one of the world's most complex operational environments.

1. Geography & Physical Characteristics

The East China Sea is bounded by a roughly rectangular outline. To the northwest, it transitions into the Yellow Sea (Huang Hai) along the line connecting the mouth of the Yangtze River and the western tip of Jeju Island off the southern coast of the Korean Peninsula. The Korea Strait— divided into the Western Channel (approximately 50 km wide, between Korea and Tsushima Island) and the Eastern Channel (Tsugaru Strait approach) — marks the sea's northeastern boundary and separates it from the Sea of Japan (East Sea). To the south, the Taiwan Strait (width approximately 130–180 km at its narrowest point near Taiwan's northern cape and the Chinese coast of Fujian Province) connects the East China Sea to the South China Sea. The eastern boundary is formed by the chain of the Ryukyu Islands(Nansei Shotō), extending over 1,200 km in a northeast-southwest arc from Kyushu, Japan, to the Yaeyama Islands near Taiwan.

The most dramatic structural feature of the East China Sea floor is the profound contrast between the broad, shallow East China Sea Shelf and the deep Okinawa Trough immediately to its east. The continental shelf occupies the vast majority of the sea's area — approximately 70% of the East China Sea is less than 200 metres deep, with large areas between 40 and 100 metres. This makes it one of the widest continental shelves in the world. The shelf has a gentle gradient sloping eastward from the Chinese coast; at its widest, between the Yangtze Delta and the central Ryukyus, it extends nearly 700 km before reaching the shelf edge. During the last glacial maximum approximately 18,000 years ago, sea levels were some 120 metres lower than today, exposing much of the present East China Sea Shelf as dry land — a land bridge connecting China to Korea and Japan across which both human populations and terrestrial fauna migrated.

The Okinawa Trough is a back-arc rift basin running roughly parallel to the Ryukyu Island arc along its inner (western) flank. It stretches approximately 1,200 km from the southwest of Kyushu to northeast of Taiwan, reaching maximum depths of 2,719 metres — a geological and oceanographic boundary of great significance. The Trough is tectonically active, associated with active hydrothermal vents and submarine volcanic activity. It is also the locus of the disputed Chunxiao/Shirakaba gas fieldcluster, where the median line between China's and Japan's claimed EEZs passes through what may be a continuous geological reservoir. The seismic character of the Okinawa Trough introduces a risk of submarine landslides and tsunamis; the southern Ryukyu subduction zone is one of the most seismically active in the world.

The Yangtze River (Chang Jiang) is the sea's dominant hydrological influence. As China's longest river, draining a catchment of 1.8 million km² across central and southwestern China, it discharges approximately 900 km³ of freshwater annually into the East China Sea near Shanghai, carrying an enormous sediment load — historically around 480 million tonnes per year, though substantially reduced since the impoundment of the Three Gorges Dam in 2003. The Yangtze plume extends far into the sea, creating a zone of reduced salinity, elevated turbidity, and high nutrient loading visible in satellite imagery as a distinctive turbid brown tongue extending eastward and northward from the estuary. The plume drives both rich biological productivity and significant eutrophication. The Min River, Qiantang River (the latter famous for its tidal bore), and numerous smaller streams along the Zhejiang and Fujian coasts contribute additional freshwater and sediment.

The Ryukyu Islands form a complex archipelago of approximately 161 islands grouped in three main clusters: the Amami Islands (closest to Kyushu), the Okinawa Islands (including Okinawa Hontō, the largest island), and the Sakishima Islands (including Miyako and Yaeyama, closest to Taiwan). The islands are separated from one another by deep, navigable channels — the Tokara Strait, Kerama Gap, and Miyako Strait — through which the Kuroshio Current flows strongly, and which serve as deep-water navigation passages between the East China Sea and the open Pacific Ocean. The island chain functions as a natural eastern barrier to the sea, giving it the enclosed character of a semi-enclosed sea.

2. Oceanography & Climate

The oceanography of the East China Sea is dominated by two competing influences: the warm, saline, deep-blue waters of the Kuroshio Current along its eastern margin, and the cold, fresh, nutrient-rich waters of the continental shelf interior, heavily modified by river runoff and seasonal monsoon circulation. The Kuroshio — the western boundary current of the North Pacific subtropical gyre — enters the East China Sea through gaps in the Ryukyu Islands, most significantly through the Tokara Strait, and flows in a well-defined band 100–200 km wide along the inner edge of the Ryukyu chain before exiting northeast of Kyushu into the open Pacific. Surface speeds within the Kuroshio core reach 2–4 knots; sea surface temperatures are 24–29°C in summer and 20–24°C in winter — substantially warmer than the continental shelf waters to the west.

Over the broad continental shelf, a completely different water mass regime prevails. The Yellow Sea Cold Water Mass (YSCWM) persists in the deeper northern parts of the shelf throughout summer, trapped below the thermocline as a remnant of winter mixed-layer cooling. In the shallower central and southern East China Sea shelf, summer heating drives strong stratification, with warm surface waters (28–30°C in August) overlying cooler bottom water. In winter, the East Asian Monsoon drives vigorous mixing, deepening the mixed layer and cooling the shelf waters to 10–15°C in the north. This seasonality of the water column structure has profound implications for biological productivity and fishing — the spring breakdown of winter mixing delivers nutrients to the euphotic zone and drives the annual spring bloom.

Salinity across the East China Sea shelf is highly variable, reflecting the competing influence of the Kuroshio (34–35 ppt) and Yangtze River discharge (the estuarine plume can reduce surface salinity to below 20 ppt within the immediate outflow area in summer flood season). Seasonal averages on the inner shelf range from 29 to 32 ppt. The salinity gradient creates a frontal zone — the Yangtze Diluted Water front — that shifts seasonally with the balance between river discharge and oceanic intrusion, and which is ecologically significant as a concentration zone for fish and plankton.

The East Asian Monsoon governs the seasonal climate cycle. From November to April, the northeast monsoon brings cold, dry continental air masses from the Siberian high-pressure system across the sea, generating northeasterly winds of Force 5–7 on the Beaufort scale, accompanied by a heavy swell of 2–4 metres from the north and northeast. This season is characterised by reduced visibility due to dust haze (particularly strong in spring when Gobi Desert dust is transported across the sea), fog, and strong tidal currents. From June to September, the southwest monsoon(known in the East China Sea region as the meiyu or plum rain season during its early phase) brings warm, humid southwesterly airflows, reduced wind speeds over the open sea, and the risk of convective squalls and thunderstorms.

Typhoons represent the most severe navigational and safety hazard of the East China Sea. The typhoon season officially spans June to November, with peak activity in August and September. Typhoons forming in the western Pacific or Philippine Sea that track northward into the East China Sea are capable of extreme intensity — Category 4 and 5 typhoons have made landfall on the Chinese coast, Okinawa, and Taiwan with devastating consequences. Vessels caught in the path of a typhoon in the enclosed East China Sea face the compound hazard of extreme winds, very high seas with short wave periods over the shallow shelf, and storm surge in coastal approaches. Spring fog (March to June) is a significant hazard in the northern East China Sea and Yangtze approaches, generated when warm moist air from the south moves over the colder shelf waters; visibility can fall to zero for days at a time, with particular severity in the Yangtze estuary approaches to Shanghai.

3. Marine Ecology & Biodiversity

The East China Sea was historically one of the most productive fishing grounds in the world. The broad, shallow continental shelf, enriched by nutrients from the Yangtze and other rivers and by the productive interaction zone where shelf water meets the Kuroshio, supported vast populations of commercially important demersal and pelagic species. That ecological richness has been severely degraded by decades of intensive, poorly regulated fishing — a crisis that now constitutes one of the most serious fisheries collapses in modern marine history.

The large yellow croaker (Larimichthys crocea) was the emblematic commercial species of the East China Sea, forming the basis of major fisheries in Zhoushan, Zhejiang Province, for centuries. Annual catches of large yellow croaker in the 1950s and 1960s exceeded 100,000 tonnes; by the late 1990s, the wild catch had collapsed to below 1,000 tonnes per year — a decline exceeding 99% from historic levels — driven by industrial trawling, pair-trawl operations, and the targeting of aggregations during spawning. The species is now commercially extinct in most of its former range and survives primarily through mariculture in Fujian Province. Small yellow croaker(Larimichthys polyactis) experienced a similar, if less extreme, collapse. Hairtail(largehead hairtail, Trichiurus lepturus), another historically dominant species, remains the largest single catch by volume in the East China Sea but has been substantially reduced in average size and age, indicating strong fishing pressure.

The Japanese eel (Anguilla japonica) is critically endangered throughout its range, which includes the East China Sea coastal rivers. Eels undertake a remarkable transoceanic spawning migration to the Sargasso-equivalent spawning grounds in the western North Pacific; juvenile glass eels migrate back to the coast and enter freshwater rivers. Demand for eel in East Asian cuisine (particularly the Japanese unaju grilled eel tradition) has driven commercial glass eel collection to unsustainable levels, combined with habitat loss from dam construction and river channelisation. The species is listed as Endangered on the IUCN Red List.

Marine mammals present in the East China Sea include the Chinese white dolphin(Sousa chinensis), also known as the Indo-Pacific humpback dolphin, which inhabits coastal waters of the Pearl River Delta, Taiwan Strait, and southern East China Sea. The population is under severe pressure from boat strike, fishing gear entanglement, noise pollution from heavy shipping, and reclamation of shallow coastal habitat. The finless porpoise(Neophocaena asiaeorientalis) — both the Yangtze River subspecies (critically endangered) and the East China Sea coastal subspecies — inhabits the estuarine and shallow coastal zones. The loggerhead sea turtle (Caretta caretta) nests on beaches of the Ryukyu Islands and forages extensively in East China Sea waters; it is listed as Vulnerable globally and threatened by longline bycatch, marine debris ingestion, and nesting beach development. The Ryukyu Islands themselves host extensive coral reef systems — the northernmost significant coral reef ecosystem in the Pacific — which are under increasing thermal stress from warming sea surface temperatures and ocean acidification.

4. Maritime Trade Routes & Shipping

The East China Sea is at the heart of the world's busiest and most commercially significant maritime corridor. The combined throughput of the ports ringing the sea — Shanghai, Ningbo-Zhoushan, Busan, and the major Taiwanese and Japanese ports — makes this one of the highest-density shipping zones on earth. The principal trade axis runs through the sea as part of the main trunk route connecting the Persian Gulf and Indian Ocean, the Strait of Malacca, the South China Sea, the Taiwan Strait, the East China Sea, and the major Northeast Asian consumer and manufacturing economies of China, Japan, and South Korea.

The Shanghai–Busan–Japan corridor is one of the world's highest-frequency container shipping lanes. Dozens of container services call at Shanghai and Ningbo before proceeding north via the Yellow Sea to Busan (South Korea's primary transshipment hub), and then to Japanese ports including Nagoya, Yokohama, Tokyo, and Kobe. Ultra Large Container Vessels (ULCVs) of 20,000–24,000 TEU capacity operate the mainlane routes between Asia and Europe, routing through the Taiwan Strait and Malacca Strait. Feeder services redistribute cargo from the mainlane hubs at Shanghai and Busan to smaller regional ports throughout China, Japan, Korea, and Southeast Asia. The vessel density in the East China Sea at any given time — visible on AIS tracking systems — is extraordinary, with hundreds of merchant vessels, fishing boats, naval vessels, and coast guard ships operating simultaneously.

The Taiwan Strait is a global maritime chokepoint of the highest order. Approximately 40–50% of global container trade and a substantial portion of the world's crude oil tanker traffic transit this 180 km-wide passage annually. The Strait is served by a Traffic Separation Scheme (TSS) established in cooperation between China and Taiwan's maritime administrations, with two main lanes for northbound and southbound traffic. The geopolitical sensitivity of the Strait — it is a flashpoint in cross-strait relations between the PRC and Taiwan, with periodic military exercises by the People's Liberation Army Navy (PLAN) and Air Force that generate Notices to Mariners and temporary restricted areas — means that passage planning for Taiwan Strait transits should always include monitoring of the latest political situation and NAVTEX warnings. During PLA military exercises, specific sea areas may be declared off-limits to commercial traffic, requiring diversionary routing.

LNG (Liquefied Natural Gas) imports are a dominant cargo flow in the East China Sea, reflecting Japan's position as the world's largest LNG importer and South Korea's as the world's second-largest. Following the 2011 Fukushima nuclear disaster, Japan dramatically increased LNG imports to compensate for the shutdown of its nuclear generating capacity; China has also become a major LNG importer as part of its coal-to-gas transition programme. LNG carriers transiting the East China Sea from Middle Eastern, Australian, and US export terminals are among the most commercially critical vessels in the global energy supply chain. LNG import terminals at Niigata, Yokohama, Nagoya, and Osaka (Japan), Incheon, Pyeongtaek, and Tongyeong (South Korea), and Tianjin, Qingdao, and Ningbo (China) handle this traffic.

Crude oil tanker traffic is heavy throughout the sea, with VLCCs from the Persian Gulf routing via the Strait of Malacca and South China Sea before transiting the Taiwan Strait en route to Chinese refineries at Ningbo, Zhoushan, Qingdao, and Dalian, or Japanese refineries at Yokkaichi, Kashima, and Chiba. China surpassed the United States as the world's largest oil importer in 2017; the economic consequences of any disruption to this tanker flow through the East China Sea would be immediately felt in global oil markets. Car carrier (Pure Car and Truck Carrier, PCTC) traffic is intense, reflecting Japan's and South Korea's dominant role in global automobile exports — Toyota, Honda, Nissan, Hyundai, and Kia all use East China Sea ports as primary export gateways.

5. Key Ports & Harbours

Shanghai (CNSHA) — World's Busiest Container Port

The Port of Shanghai is the world's busiest container port by TEU throughput, a position it has held every year since 2010. In 2023 it handled approximately 49 million TEU, a figure representing roughly 10% of total global container port throughput. The port complex consists of several distinct operational areas: Yangshan Deep Water Port, constructed on reclaimed land around the Xiaoyangshan and Dayangshan islands in Hangzhou Bay and connected to the mainland by the 32.5 km Donghai Bridge (the world's longest sea-crossing bridge at its completion in 2005), handles the largest container vessels with berths dredged to 17 metres; Waigaoqiao, on the north bank of the Yangtze River near its mouth, handles significant container and general cargo volumes; and Wusong, the traditional inner-harbour area, serves cruise ships and river traffic. The Shanghai VTS (Vessel Traffic Service) manages the complex approaches via the South Channel of the Yangtze Estuary; vessels must obtain a fairway permit well in advance, and pilotage is compulsory for all foreign vessels entering the port. The approach is subject to strong tidal currents (up to 4 knots), significant sediment deposition requiring continuous dredging maintenance, and seasonal fog.

Ningbo-Zhoushan (CNNGB) — World's Largest by Cargo Tonnage

The Ningbo-Zhoushan Port complex, formed by the administrative merger of the ports of Ningbo and Zhoushan in 2015, has ranked as the world's largest port by total cargo tonnage for more than a decade, handling over one billion tonnes of cargo per year. The port is located approximately 150 km south of Shanghai at the southern entrance to Hangzhou Bay, where the Zhoushan Archipelago provides sheltered deep-water anchorages of considerable extent. Ningbo's Beilun container terminal is one of the most capable in Asia, with berths accommodating 20,000+ TEU vessels. The port complex also includes major iron ore, crude oil, LNG, and coal terminals — Ningbo is one of China's primary crude oil import and storage terminals, with enormous Suezmax and VLCC berths at Cezi Island and Zhoushan. Container throughput has exceeded 35 million TEU annually. The port's rapid growth reflects both its geographic advantage — located on Hangzhou Bay with direct access to the Yangtze Delta manufacturing zone — and major infrastructure investment.

Busan (KRPUS) — Northeast Asia's Leading Transshipment Hub

The Port of Busan, located at the southeastern tip of the Korean Peninsula where the Korea Strait meets the East China Sea, is South Korea's principal port and one of the world's top five container ports, handling approximately 22–24 million TEU per year. Busan occupies a strategic position as the primary transshipment hub for Northeast Asia — its location between China, Japan, and the main Pacific and Indian Ocean trade routes makes it an ideal relay point for cargo moving between regional feeders and mainlane services. The port is divided between North Port (the older downtown area handling general cargo and RoRo), Gamcheon, and the modern New Port (Busan New Port, or BNP) at Gaduk Island, where deep-water container berths (draft to 18 metres) accommodate the world's largest vessels. The port benefits from excellent connectivity to Korean hinterland via road and rail, and Busan Airport facilitates air cargo integration. Pilotage in Busan approaches is compulsory from the outer anchorage; the Korea Strait approaches require careful navigation particularly in the Western Channel where tidal currents reach 3–4 knots.

Nagasaki (JPNGS) — Historic Japanese Port

Nagasaki, on the western coast of Kyushu facing the East China Sea, is one of Japan's most historically significant ports and was, during Japan's period of national isolation (1639–1854), the only port open to foreign trade — with Dutch and Chinese merchants granted limited trading rights at Dejima island and the Tōjin Yashiki quarter respectively. Today Nagasaki is a significant port for ferry services to the Goto Islands, Tsushima, and other offshore islands, and hosts the Mitsubishi Heavy Industries shipyard — one of Japan's most important, which built the battleship Musashi during the Second World War and now specialises in LNG carriers, naval vessels, and offshore structures. The port is a cruise vessel destination of growing importance. Nagasaki approaches through the East China Sea require attention to the numerous islands and rocks of the Goto Rettō archipelago west of Kyushu, which present navigation hazards and restricted fishing zones.

Keelung (TWTPE) — Taiwan's Northern Gateway

Keelung (Jilong), located at the northeastern tip of Taiwan approximately 25 km from Taipei, is Taiwan's main general cargo and container port in the north of the island and serves as the principal gateway for the Taipei metropolitan region — Taiwan's political, financial, and industrial centre. The port handles approximately 1.5–2 million TEU annually and is a significant transshipment point for cargo moving between China, Japan, and Southeast Asia. Keelung is known for its challenging approach conditions: the port lies at the northeastern corner of Taiwan exposed to the full fetch of the East China Sea, and it is the foggiest major port in East Asia, with dense fog common between October and May driven by the interaction of the cold China Coastal Current and warm moist air from the southwest. The Taiwan Strait approaches require particular attention to the traffic separation scheme and the cross-strait political environment.

6. Historical & Strategic Significance

The East China Sea was a primary artery of the ancient Maritime Silk Road that linked China to Southeast Asia, India, Arabia, and ultimately East Africa and the Mediterranean world. From the Han Dynasty (206 BCE – 220 CE) onward, Chinese merchant vessels — junks carrying silk, porcelain, tea, and spices — navigated the sea using monsoon winds and the Kuroshio Current to reach Japanese ports at Hakata (modern Fukuoka), Korean ports, and the ports of Southeast Asia. The port of Quanzhou, in Fujian Province on the western shore of the Taiwan Strait, was in the 10th–14th centuries CE one of the largest ports in the world, serving as the eastern terminus of the maritime silk road under the Song and Yuan dynasties. Arab, Persian, Indian, and Southeast Asian merchant communities maintained permanent settlements there. Marco Polo described Quanzhou (as “Zaitun”) as a port of extraordinary wealth and commercial activity.

The First Sino-Japanese War of 1894–95 was fundamentally a naval conflict fought across the East China Sea and Yellow Sea. Japan's modernised Imperial Navy, built on European models, confronted China's Beiyang Fleet — then considered one of the most powerful in Asia — in the Battle of the Yellow Sea (17 September 1894), which resulted in the near-annihilation of the Chinese fleet and confirmed Japanese naval supremacy in the region. The peace treaty ceded Taiwan and the Pescadores to Japan, establishing a Japanese maritime presence that would define the strategic geography of the East China Sea for the next half-century. The war launched Japan on its trajectory as a Pacific imperial power.

During the Second World War, the East China Sea was the scene of intensive naval warfare as the United States “island-hopping” campaign moved northward through the Pacific. The Battle of the East China Sea (April 1945) saw the sinking of the Japanese super-battleshipYamato — at 72,800 tons displacement the heaviest warship ever built — by US Navy aircraft during its one-way sortie toward Okinawa, where it was intended to beach itself as an unsinkable gun platform.Yamato sank approximately 180 nautical miles southwest of Kyushu with the loss of over 3,000 crew members. The subsequent Battle of Okinawa (April–June 1945) was the largest amphibious assault in the Pacific War, resulting in approximately 200,000 deaths — one of the deadliest single battles of the entire conflict. The US military presence on Okinawa, formalised in the 1951 San Francisco Peace Treaty and subsequent Status of Forces Agreements, established the strategic posture that continues to shape East China Sea security today.

The Senkaku/Diaoyu Islands dispute is the most active territorial conflict in the contemporary East China Sea. The five main islets and three rocks are administered by Japan under its Nansei Shoto jurisdiction, controlled by the Japan Coast Guard. China and Taiwan claim sovereignty based on historical records and the principle of proximity. The dispute intensified in 2012 when the Japanese government purchased three of the islands from their private Japanese owner, triggering large-scale anti-Japanese protests in China and a sharp escalation in Chinese Coast Guard and maritime militia vessel incursions into the contiguous zone. The islands have no permanent civilian population but are of strategic interest as they sit near the Okinawa Trough oil and gas fields, command important maritime passage routes, and have symbolic significance in both Chinese and Japanese national narratives.

China's declaration of an Air Defense Identification Zone (ADIZ) over the East China Sea in November 2013 — covering an area including the Senkaku/Diaoyu Islands and requiring all aircraft entering the zone to report to Chinese authorities — was a major escalation that was immediately rejected by the United States, Japan, and South Korea. The US flew B-52 bombers through the zone without notification to demonstrate non-recognition. The Taiwan Strait question remains the most potentially destabilising strategic issue in the East China Sea: any military conflict over Taiwan would almost certainly involve the Strait and the broader East China Sea, with catastrophic consequences for global shipping. US carrier strike groups periodically conduct freedom of navigation operations in the Taiwan Strait to assert the principle of international waters passage.

7. Navigation Safety & Hazards

The East China Sea falls within NAVAREA XI, coordinated by the Japan Coast Guard's Hydrographic and Oceanographic Department (JCG HOD) in Tokyo. Navigational warnings are broadcast on NAVTEX at 518 kHz (English) and 490 kHz (Japanese) from transmitters at Nagasaki, Choshi, Moji, and other stations ringing the sea, as well as via SafetyNET on Inmarsat-C. In addition to the NAVAREA XI broadcasts, mariners in the East China Sea should also subscribe to warnings issued by China's Maritime Safety Administration (MSA), which broadcasts on its own NAVTEX system in Chinese, and to Republic of Korea Coast Guard warnings. Warnings cover offshore platform positions, new wrecks, cable-laying operations, military exercise areas, and hazards to navigation in fishing grounds.

The Taiwan Strait Traffic Separation Scheme (TSS) is one of the most important and complex regulatory traffic management arrangements in the East China Sea. Established under the auspices of the International Maritime Organization, it designates northbound and southbound lanes with a median zone, covering the central fairway of the Strait between Taiwan and mainland China. Compliance is monitored by both Taiwan's Maritime Port Bureau and China's Maritime Safety Administration. Vessels transiting the Strait should monitor VHF Channel 16 at all times and call the relevant VTS authorities as required. The proximity of Chinese naval and coast guard activity in the Strait — including periodic military exercises that may generate Notices to Mariners and NOTAM airspace restrictions — means mariners must monitor current intelligence before and during transit.

The approach to Shanghai is among the most technically demanding port approaches in the world. The Yangtze River estuary is a shallow, tidally complex approach with extensive sand banks and shifting channels. The approved deep-water approach channels — the South Channel (Nancao Channel) for outbound and the North Channel for inbound traffic — are subject to continuous tidal stream reversal, sedimentation, and reduced visibility in fog season. The Shanghai VTS requires vessels to report at designated waypoints on VHF Channel 16 and to comply with passage plans issued by the VTS. Pilotage is compulsory for all foreign-flagged vessels; pilots board approximately 30–40 nautical miles offshore at the pilot boarding ground. Under keel clearance (UKC) management in the Yangtze estuary requires tidal window planning, as the dredged channel depths may be marginal for fully laden VLCCs and large bulk carriers. Masters should obtain up-to-date dredging and surveying information from Chinese MSA Notices to Mariners before finalising approach plans.

Both Japan and China maintain Air Defense Identification Zones (ADIZs) over the East China Sea, and while these are primarily air navigation instruments, their existence reflects the militarised character of the airspace and maritime domain in the region. Ships should be aware that naval and coast guard activity from China, Japan, South Korea, and the United States is persistent throughout the sea. Naval warships exercising innocent passage rights may operate in proximity to commercial shipping lanes; fishing fleets — particularly large Chinese distant-water fishing fleets operating in the central and southern East China Sea — create significant radar clutter and collision risk in night and restricted-visibility conditions.

Typhoon routing is a critical skill for East China Sea passage planning during the June–November season. Officers should monitor Japan Meteorological Agency (JMA) and JTWC tropical cyclone advisories daily. When a typhoon warning is issued, vessels should seek a port of shelter if in range, or execute an avoidance manoeuvre placing maximum distance between the vessel and the forecast track. The fundamental principle — staying out of the dangerous (right-hand, advancing) semicircle in the Northern Hemisphere — applies; however, the East China Sea's limited sea room and complex coastline mean that full avoidance may not always be possible for vessels on coastal passages. The Okinawa Trough and its associated seismic activity creates a small but non-negligible risk of locally generated tsunamis; the Japan Meteorological Agency issues Pacific-wide tsunami warnings through the PTWC (Pacific Tsunami Warning Center) system, and vessels should be familiar with their tsunami response procedures in port and at anchor.

8. Environmental Issues

The East China Sea faces an environmental crisis of extraordinary severity, the product of decades of rapid industrialisation, population pressure, and governance failures across its coastal nations. The convergence of overfishing, pollution, habitat destruction, climate change, and geopolitical barriers to cooperative management has made the East China Sea one of the most environmentally stressed semi-enclosed seas in the world.

Overfishing is the most acute crisis. China operates the world's largest fishing fleet — estimated at over 400,000 motorised fishing vessels in domestic and distant-water operations — and the East China Sea has been the primary operating ground for large-scale industrial trawling since the 1970s. The combination of pair trawling (two vessels deploying a large net between them, sweeping the bottom clear of all biological life), stow net fisheries in the Yangtze estuary, and intensive light fishing for squid has reduced virtually all target species populations to fractions of their former abundance. China's seasonal fishing moratorium in the East China Sea (typically May–September in the Yellow and East China Sea zones) was introduced in 1995 as a partial conservation measure, but its enforcement has been inconsistent and its duration may be insufficient to allow meaningful stock recovery given the removal rate during the open season.

The Yangtze River is responsible for one of the most significant pollution inputs of any river system into any enclosed or semi-enclosed sea in the world. It delivers agricultural fertiliser runoff (nitrogen and phosphorus), industrial wastewater, heavy metals from mining operations in upstream provinces, and plastic waste at a scale commensurate with its enormous drainage basin and the concentration of industrial activity along its banks. The resulting hypoxic zone(dead zone) off the Yangtze estuary — where bottom dissolved oxygen falls below 2 mg/L, stressing or killing bottom-dwelling organisms — forms seasonally and has expanded dramatically since the 1980s, reaching areas comparable to the well-publicised Gulf of Mexico dead zone. The Three Gorges Dam, while it has reduced the sediment load of the Yangtze by trapping silt behind its reservoir, has also disrupted the nutrient flux from the river, with complex and not yet fully understood consequences for the East China Sea ecosystem.

Oil spill risk from the heavy shipping traffic in the East China Sea is high and manifesting in periodic catastrophic incidents. The most significant recent event was the January 2018 collision between the Iranian condensate tanker Sanchi and the Hong Kong-flagged bulk carrier CF Crystal approximately 160 nm east of Shanghai. Sanchi, carrying 111,500 tonnes of ultra-light condensate (an exceptionally toxic and flammable hydrocarbon mixture), caught fire and burned for ten days before sinking — the largest tanker disaster in decades. The condensate formed a massive surface slick and subsurface plume that drifted northeast toward Japan. The incident exposed the limited capability for fire suppression and environmental response in the open East China Sea. Chinese and Japanese coast guard and salvage resources were stretched to their limits, and international cooperation in response was complicated by the geopolitical sensitivities of the region.

China's programme of coastal reclamation has profoundly altered the physical and ecological character of the East China Sea coastline. An estimated 50–65% of the original tidal flat and intertidal habitat along the Chinese coast of the East China Sea has been reclaimed since the 1950s — a loss that has destroyed nursery and feeding habitat for fish, eliminated key staging areas for migratory shorebirds (the East Asian–Australasian Flyway, one of the world's most important bird migration routes, passes through this coastline), and altered coastal hydrodynamics in ways that can increase storm surge flooding risk for coastal cities. The reclamation programme continues at pace, driven by land scarcity in China's coastal provinces.

The disputed Chunxiao/Shirakaba gas field cluster in the Okinawa Trough exemplifies the intersection of environmental and geopolitical risk in the East China Sea. China and Japan claim overlapping exclusive economic zones in this area; China has constructed production platforms on its side of the proposed median line, while Japan protests that the gas field reservoir may extend across the boundary and that Chinese production constitutes unilateral exploitation of a shared resource. Negotiations on a joint development agreement have been intermittent and inconclusive. Any gas field blowout or pipeline failure in this tectonically active rift zone would pose a severe environmental hazard in waters where search and rescue, firefighting, and oil spill response capabilities are already stretched by the routine demands of the world's busiest shipping lanes. Ocean acidification, driven by the East China Sea's absorption of anthropogenic CO₂, is measurably affecting the calcification of the Ryukyu Island coral reefs and the shell-forming capacity of commercially important molluscs and crustaceans in coastal aquaculture operations.