Fast growing aquaculture production is threatening the rich biodiversity in the seas bordering Japan, People’s Republic of China, Republic of Korea and the Russian Federation, according to an assessment by a United Nations marine environmental health monitoring centre in Toyama, Japan.
Alien species, habitat alteration and eutrophication of seas caused by entry of excessive nutrients are among major threats to the region’s marine biodiversity, and aquaculture is a main contributory factor, says the study by the Toyama-based Special Monitoring and Coastal Environmental Assessment Regional Activity Centre (CEARAC).
There has been a dramatic increase in aquaculture in the Northwest Pacific over the past 15 years. The region produced 60 per cent of the global aquaculture harvest in 2015 with China accounting for 61 million of the 63.8 million tons regional aquaculture yield. Feed for cultured fish is a major source of eutrophication-causing nutrient discharge in seas. Aquaculture of non-indigenous species is one of the pathways of introduction of alien species in nature.
Eutrophication, alien species and habitat alteration are also being caused by rapid industrialization, heavy fertilizer use and the large shipping traffic in the densely populated Northwest Pacific, says Assessment of major pressures on marine biodiversity in the NOWPAP region, published by Special Monitoring and Coastal Environmental Assessment Regional Activity Centre. The Centre is one of four regional activity centres of the 25-year-old UN Environment Action Plan for the Protection, Management and Development of the Marine and Coastal Environment of the Northwest Pacific Region (NOWPAP).
“Aquaculture is not a unique driver (of these three threats) in other regions; however, its impact on marine biodiversity is quite strong in the Northwest Pacific,” says the study. Action taken by the four Northwest Pacific member countries to address this threat “may be insufficient for addressing the growing pressures on marine biodiversity,” it notes.
The Centre’s assessment was carried out in the coastal areas of Yantai and Dalian in China, North Kyushu Sea area and the coastal area of Hokuriku region in Japan, Saemangeum in Korea and Peter the Great Bay in Russia. It uses the driving forces – pressure – state – impact – response framework to identify the causes of eutrophication, invasive species and habitat alteration, the impact of these on biodiversity and the response to this threat.
According to the study’s findings, aquaculture is a major cause for eutrophication and entry of invasive species which are threatening marine biodiversity in the Northwest Pacific. Aquaculture farms in the region, increasingly being set up in sea areas, use huge volumes of fish feed which generates eutrophication-causing nutrients. Fecal production by aquaculture-farmed fish also causes eutrophication and hypoxia in bottom waters.
The growing use of foreign species in aquaculture in the Northwest Pacific has increased the risk of escape into the natural environment. In China, 25 per cent of aquaculture production is of non-native species and these have escaped from aquaculture farms and damaged native marine ecosystems by predation and hybridization. The sea urchin Strongylocentrotus intermidus, introduced from Japan into northern China, escaped from breeding cages and became a huge threat for seaweed beds in coastal areas.
More than 100 non-indigenous species have been found in the coastal waters of the four Northwest Pacific member states – 27 in China, 31 in Japan, 41 in Korea and at least 37 in Russian Northwest Pacific waters.
The threat of entry of non-indigenous species by ship ballast water and ship hull-fouling is also growing due to the large volume of sea trade traversing the region which is a global maritime commerce hub. All Northwest Pacific member states but P.R. China have ratified the Ballast Water Management Convention that entered into force in 2017.
The Centre’s assessment will help Northwest Pacific member states reduce pressures on biodiversity in the region in keeping with the Aichi Biodiversity Targets and the Sustainable Development Goals. The assessment is an important step towards development of the Regional Action Plan on Marine and Coastal Biodiversity Conservation over the next few years.