Parasite to blame for fish deaths

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  • This dead fish washed up at John’s Smith Bay (File photograph)

    This dead fish washed up at John’s Smith Bay (File photograph)


The gill parasite brooklynella has been identified as the cause of death of fish washed up on Bermuda’s beaches.

Large numbers of fish from a wide range of species, including the ecologically important parrotfish, have died of the illness — linked to rising temperatures of seawater.

The Department of Environment and Natural Resources has carried out tests on dead and dying fish, and decided that brooklynella, which caused a major fish die-off eight years ago, was again the culprit.

The department added that nearby storm activity will probably lower the water temperature, which would mean fish deaths should decrease.

Offshore species like wahoo and tuna are not thought to be affected.

A department spokeswoman said a small clip of the affected gills was examined from each fresh fish specimen.

She added: “In each case, this revealed that the gills were heavily infested with mobile, single-celled parasites that resemble brooklynella, a species that was linked to the fish die-off event in 2009.

“Department scientists think that this was likely the cause of death. Other organs from these specimens did not show any obvious signs of pathogenic effects.”

Large numbers of brooklynella parasites can cause serious damage to the gills of a fish, which makes it more difficult for them to take in oxygen, which leads to death.

The life cycle of the parasite, like other micro-organisms, is accelerated by warmer temperatures, which is made worse by an increase in the stress levels of fish because of the warm water.

Bermuda Weather Service statistics showed that the average sea surface temperature in August was 85.8F, compared with the expected average of 84.6F.

The Department said: “Seawater temperatures now appear to be dropping in the wake of recent storm activity and it is anticipated that, with cooler water temperatures, fish deaths will decrease.”

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Published Sep 22, 2017 at 10:05 am (Updated Sep 22, 2017 at 11:21 pm)

Parasite to blame for fish deaths

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