Hatchery fish detected with disease

Otago Fish & Game has had confirmation from MAF that a yearling trout from the Macraes Hatchery has been positively identified as being infected with the Aeromonas bacteria.

The bacterial disease was first detected in lamprey in the Mataura River.

“Fish & Game has been working closely with MAF since being notified of the disease and we’ve been extra vigilant in our hatchery activities,” says Otago Fish & Game chief executive Niall Watson.

“It was this vigilance that caused our hatchery manager to detect a poor conditioned trout with lesions at the Macraes Hatchery last week. The trout was promptly sent away to MAF who have now confirmed it was infected with the bacteria.

“We’re awaiting MAF analysis to confirm which strain we might be dealing with,” says Mr Watson. “Two other fish with suspicious markings have also been sent away for analysis but at this stage we’ve had no other mortalities.

“It’s not at all uncommon to have an occasional sick fish in a hatchery situation – the rest of the 3000 trout appear fit and healthy at this stage.

“Until we know exactly what we’re dealing with though we’ve stepped up the monitoring of our hatchery stock and will be restricting access to the hatchery itself to staff involved in essential management. Also, no fish liberations will proceed until the situation is clarified.”

During September approximately 3500 trout were liberated into 10 small reservoirs and lakes in Otago as part of our normal stocking programme but no liberations have been made since the end of September. All fish were healthy when released with no signs of illness.

“Fish diseases are found in wild populations but are often more pronounced and more detectable in hatchery situations where fish are under stress from handling.”

Fish & Game continues to work closely with MAF, the lead agency investigating this disease outbreak.