Fish kills off Kaikoura linked to toxic algae

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New findings by scientists at the National Institute of Water and Atmospheric Research (NIWA) have revealed that the death of kina, starfish, and possibly other fishes, in late January and early February off the Kaikoura coast appears to be linked to toxic algae.

Samples of dead kina and starfish tested by Environmental Science Research (ESR) contained a toxin indicative of gymnodimine. This toxin is produced by an algal species called Gymnodinium cf. mikimotoi. This indicates that this toxic alga was present off Kaikoura at the time of the fish kills. No toxin, however, has been detected in the guts of dead paua or in marlin, and at this point the cause of death for both these species remains a mystery.

This toxic alga was also present at the time of fish kills (tuna, marlin, swordfish, louvars, moonfish, paua, kina, starfish, lobsters) off the Wairarapa coast in mid January to early February. The presence of this alga was not only linked to fish kills, but also to respiratory distress suffered by beach-goers at a number of areas off this coast and in Hawkes Bay. Schoolchildren on a beach education programme at Riversdale, beachgoers, residents, and swimmers in the same area, and on beaches around Castlepoint and Mataikona, all complained of a dry cough, sore throats, burning nose, and eye and skin irritations. The alga Gymnodinium cf. mikimotoi was identified by Dr Hoe Chang, a scientist at NIWA, in water samples collected from Riversdale and Castlepoint. This is the first time that the build-up of this species has been reported off the southeast coast of the North Island, and the first time that this species has been implicated in respiratory distress in humans in New Zealand.

The presence of toxins indicative of this toxic algal species off Kaikoura has now shown that it was widespread off the east coasts of both the North and South Islands, between Hawkes Bay and the Kaikoura coast. The occurrence of this toxic species is likely to be linked to large-scale changes in oceanographic conditions in the region. Results from a current research voyage off the east coast of the North Island on NIWA’s research vessel Tangaroa have shown that warmer subtropical water is further south than usual and associated with strong southward currents. Intrusion of this warm water inshore and upwelling of deep, cold nutrient-rich water along the east coast have also been observed. Research into the cause of these patterns, likely to be associated with El Nino, and their relationship with the presence of toxic algae, is ongoing.

Over the last week fish and seal deaths have been reported from west coast beaches near Foxton. One report from this area gave an account of about 300 dead fish, including leatherjackets, jack mackerel, porcupine fish, and red cod. Three fur seals were reported to be dead on a beach in the same area. NIWA is seeking water samples from the Manawatu coast, but as yet has no information on the causes of these recent deaths of sealife.

Research subject: AlgaeFish
 

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Archived on 9 April 2019