A large pod of bottlenose dolphins, resident in the Shannon Estuary for centuries, may not be nearly as well-known as a fellow dolphin further down the coast, in Dingle, Co Kerry, writes Donal Hickey
However, the Shannon dolphins, believed to be the biggest such group in Europe, are interesting in their own right.
The celebrated Fungie appears to be a solitary dolphin in Dingle Harbour, but the pod in the estuary numbers up to 140 and the figure has remained stable for many years. To all appearances, the dolphins they are doing very well. Though I’ve crossed the estuary on the car ferry many times, I’ve never seen the dolphins. For watchers, the best thing to do is probably to go on a scheduled tour.
The pod has been monitored for more than 20 years; is protected under the Wildlife Act; is a tourist attraction and produces upwards of 10 calves each year. Studies point to varied threats to the Shannon dolphins, nevertheless, highlighting the need for vigilance.
Simon Berrow, project manager with the Shannon Dolphin and Wildlife Foundation and co-author of recent study, says chemicals are posing a threat to coastal species. Some chemicals, banned for many years, are still getting into the marine environment. There’s little that can be done to remove them and a toxic time bomb is being created, he warns.
According to Dr Berrow, a lecturer in marine biology at the Galway-Mayo Institute of Technology, samples showed concentrations in the Shannon dolphins were the lowest in Europe, but the levels were still well above the toxicity threshold, which can have serious impacts on health and breeding.
Biology and Environment, published by the Royal Irish Academy, has a report in its latest issue by Dr Berrow and Joanna Barker on information about the Shannon dolphins gathered over the last seven years.
Dolphins eat a lot of fish and the report urges a careful approach to the management of the estuary, especially in regard to pair trawling, to ensure the dolphins have enough food during the autumn and winter months.
“The Shannon Estuary is the only Special Area of Conservation for bottlenose dolphins in Ireland, thus the ecological impact of pair trawlers should be fully assessed before fishing commences,’’ the report says. The fishing fleet there is normally limited to eight small boats catching lobster and crab in pots. However, in recent years, pair trawlers have occasionally been allowed catch sprat and herring in autumn and winter.
Although catches were small, the reports voices concerns that the removal of these fish may affect the dolphin diet. It says the unintentional catching of dolphins during small-scale trawling in other areas could also be a threat to the estuary dolphins.
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