Ascension Island
© Iyobi / Wikipedia
Over the last few weeks we have been recording high numbers of dead fish washing up onto the beaches around the Island.

The same thing happened, at the same time of year, in 2008. A report was published recently, called 'Reef fish mass mortality event in an isolated island off Brazil, with notes on recent similar events at Ascension, St Helena and Maldives' by Hudson Pinheiro, Joao Gasparini and Jean-Christophe Joyeux. The report states that 'it is possible that blooms of toxic algae, under certain conditions, caused cascading intoxication along the trophic web. Toxic algae occur in other Atlantic oceanic islands and there are reports of algal blooms occurring in remote areas that suffer low human impact. A second hypothesis is that seasonal upwelling events of anoxic or hypoxic waters may be involved (the low oxygen content would be due to the re-suspension of sediment and organic matter deposited at geological scales) often heavily loaded with hydrogen sulphide. Oxygen-poor waters of the Benguela upwelling have been reported to affect the southeastern Atlantic continental shelf and these waters, in years of strong Benguela upwelling, can even reach the Mid-Atlantic Ridge island of St Helena.' The full report is available to download from our website.

We are currently consulting with contacts in the UK and Falklands. I have sent them as much information as I have, including species affected, numbers, symptoms and photographs. They will be able to offer advice on the best course of action. I have also been in touch with one of the authors of 2010 report, this was his response:

I think that, as usual, nothing will be "provable" directly, which should not impede us to look for hints.

My best bet would be to check for microbial fauna (bacteries and fungi) from dying (not dead yet) and healthfull fishes, for comparison.

My second best bet would be to keep documenting kills and "associated" events in the hope a common factor emerges.

Finally, I would think that a medium- to long-term monitoring program for M. niger (black fish) mid-Atlantic populations, that seem so prone to fishkills, would greatly help in eliminating a number of hypotheses (e.g, those related to superpopulation, predation of ingestion). However, I would not expect to get real insights before having 5 to 10 years of work done, which means that is to be done by a dedicated administration and not by Masters or PhD student.

In 2008 some samples were sent to Virginia for testing. The following was reported:

Initial observations suggest that the grouper may be suffering from an opportunistic bacterial infection. Fish normally have bacteria and fungi present on their body. However, with stressful events like spawning or a seasonal change in water temperature, the fish can become vulnerable to bacteria and grow ill or die. Fish suffering from a bacterial or fungal infection will show symptoms like those seen on sick grouper on Ascension: "popeye" or distended eyeballs, white patches on scales, and white mouths and tails. In rare cases, consumption of raw, diseased fish can make humans ill.

The symptoms appear to be the same on the fish this year. Reports will be published in the Islander when we have more information on the situation.