New par­a­site found in south­ern waters

Central Otago Mirror - - BOATING AND FISHING - JO MCKENZIE-MCLEAN

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.

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