New parasite found in southern waters
A new parasite has been discovered in fish from Central Otago’s Lake Hawea, and could be in other southern waterways.
Otago Fish and Game is asking anglers who catch salmonids from Central Lakes to check for the parasite Ligula intestinalis and if detected to record where it was caught, fish species, number of parasites in the fish and total weight and length.
Morgan Trotter, of Otago Fish and Game, said recently an angler contacted the University of Otago’s Ecological Parasitology Laboratory after discovering the parasite in fish from Lake Hawea.
Analyses confirmed the parasite as a large cestode introduced from the Northern Hemisphere.
‘‘Be assured that this parasite is of no health concern and does not pose a risk to human health. Fish infected with the parasite can safely be eaten and anglers should have no apprehension about consuming their catch or even about any change of taste.’’
Otago University’s Dr Clement Lagrue said the parasite had a ‘‘complex life cycle’’ where the parasite needed three different host species to complete a generation.
‘‘Fish are actually only part of the parasite development and not the end point. Adult parasites live in the guts of fish-eating birds, most likely Crested Grebes and shags in New Zealand central lakes, and the eggs are released in the water with the bird feces.’’
Although this parasite was anecdotally recorded from New Zealand previously, it had never been documented from the South Island, he said.
‘‘It was thought to have been introduced occasionally to the North Island by infected birds travelling from Australia where Ligula intestinalis is also present, and appeared not to persist for long in New Zealand waters. However, these new records show that it is indeed present and that a variety of fish from Lake Hawea serve as hosts to the parasite.’’
Although the parasite was unlikely to significantly affect fish populations as a whole, it could have ‘‘fairly severe’’ pathological effects on its individual fish host when numbers got high, including mortality, he said.
Members of the Otago Parasitology team would be at the Lake Hawea fishing competition in November to collect samples and provide information. Collaboration from anglers would be appreciated, he said.