Recent reports have emerged of dead fish strewn along Fiji’s Coral Coast and come on the heels of observations in Vanuatu of hundreds of dead fish and invertebrates floating near Pango Village on Efate, at Emten Lagoon in Port Vila and Aneityum Island.
Fish kills can occur as a result of a number of factors, ranging from a release of toxic chemicals to low concentrations of dissolved oxygen in the water.
For now, the Pacific Community (SPC) is reinforcing government warnings and urging people in affected areas to refrain from consuming the dead fish which may be harmful to human health.
While there is currently no local-level data from which to attribute a specific cause, satellite data from the National Oceanic and Atmospheric Administration (NOAA) indicate temperatures of the waters surrounding Fiji and Vanuatu have been hotter than average since late January 2016.
“This information is deeply concerning as warm water holds less dissolved oxygen than cooler water and once the level of dissolved oxygen drops below a critical threshold, fish and invertebrates can effectively suffocate,” the Director of SPC’s Fisheries and Marine Aquaculture Division, Moses Amos, explained.
“This is especially an issue in shallow water habitats which can rapidly heat up and lose dissolved oxygen, and at night-time, algae respire, removing oxygen from the surrounding water,” Mr Amos said.
Fisheries scientists from SPC are in Fiji this week to work with the Ministry of Fisheries and Forests on developing a National Fisheries Policy and will also lend assistance with investigating the cause of the recent fish kill along the Coral Coast.
Fish kills, such as those being observed in Fiji and Vanuatu, are not a new phenomenon. In 2011, a large fish kill occurred in the Marovo Lagoon, in the Western Province of Solomon Islands, with low dissolved oxygen resulting from a die-off of a harmful algae bloom the likely cause.
Events like these underscore not only the importance of inshore fisheries resources in human affairs, but also the fragility of the reef habitats that support these resources, Mr Amos said.
In addition to the fish kills, a number of coral bleaching events have been reported in the region in the past few weeks, including on the Coral Coast of Fiji.
Coral bleaching occurs when high water temperatures cause a symbiotic relationship breakdown between the coral polyp and a tiny algae that dwells inside it (called zooxanthellae). Under normal conditions, this relationship is mutually beneficial; the algae provides food for the coral through photosynthesis while the coral provides shelter for the algae. When bleaching occurs, corals may be unable to obtain enough food, and can effectively starve to death.
Widespread coral bleaching was observed on Northern Hemisphere coral reefs over the 2015 summer, triggered by the strong El Niño conditions currently in effect. This prompted NOAA to declare the ‘third global coral bleaching event’, following the two previous mass beaching events in 1998 and 2002 that devastated many coral reefs around the world.
In 2015, NOAA predicted widespread bleaching in the Pacific Islands region over the 2015–2016 summer as El Niño conditions continue to intensify.
SPC’s analysis of the future impacts of climate change on fisheries show that reef environments will become even more fragile over the next 100 years, due both to human-induced climate change and to environmental degradation from human population pressure in coastal locations.
SPC has developed a New Song for coastal fisheries that calls for renewed emphasis upon effective management of coastal fisheries, to help maintain them in the face of increased fragility along the Pacific’s reef environments.
Useful links: New Song for Coastal Fisheries – https://goo.gl/SpVFcq