2010 Basking shark season begins.

28th Mar 2010 A number of basking shark Cetorhinus maximus sightings received by the IWDG heralding the start of what we hope will be another good year for this "honorary" whale.

The first basking shark observed this year was off the Mullet peninsular on 5 March recorded during the IWDG survey of the Wave Energy Rest Site but this was an isolated sighting.

It was always on cards, that the next period of settled weather would produce our 1st basking shark sightings of the year. And I guess that day was yesterday, 27th March, when IWDG received two records from both West Cork and Slea Head, Co. Kerry, along with a further sighting off Dog's Bay, Rounstone, Connemara. The longer days and sun's increased intensity during spring create the conditions that produce phyto-plankton blooms, which kick-start the marine food chain, and herald the arrival of this mega-grazer.

Basking shark sightings along the southwest coast anyway peak during the May/June period, but may peak later off the North coast "hotspots" such as Malin Head, where Emmett Johnston, NPWS is carrying out much of the local research.

While these may seem like early records, land- based effort watches have consistently produced sightings of this species as early as March/April. A review of the last six years shows the following dates and locations of the 1st basking shark sightings: 28 March 2004, Oysterhaven, Co. Cork, 19th March 2005 Aran Islands, Co. Galway, 18th April 2006 Fanad Head, Co. Donegal, 4th April 2007 Ventry, Co. Kerry, 8th April 2008 Ram Head, Co. Waterford and last year was 23rd March off Kilkee, Co. Clare.

So while these data don't show any clear spatial trend, they do illustrate a strong temporal trend. It is indeed likely that some sharks remain in Irish waters year round, but stay in deeper water and further satellite tagging will no doubt answer these questions in the years ahead.

Yesterday's West Cork sighting was all the more interesting, as a pod of 4-5 killer whales were seen at the same time and in the same area by several observers, including Colin Barnes. It would be interesting to prove if there this was mere coincidence, or whether the two sighting events are somehow linked. There is evidence of predation by this apex predator on basking sharks in Cornish waters, but perhaps best to wait till we observe it first hand in Irish waters before we over-speculate.

So please do keep your eyes open for this fish and either let us at IWDG know or pass on your records to www.baskingshark.ie. Now that there is an established group set up whose focus is the basking shark, we are not so precious about receiving reports of these animals...as long as the records are sent to someone.

Also between now and late July (basking shark season), expect all records of "breaching whales" to be treated with a degree of caution. In our experience, the majority of large breaching animals seen in the coming months are likely to be basking sharks, which are capable of breaching no less spectacularly than whales. The key difference is that basking shark generally breach completely unexpectedly, without any hint that they were ever present, and show no signs of their whereabouts once they have stopped breaching. This is in sharp contrast to whales; as you will generally be aware of a whale's presence, as a result of their typically larger size, visible blow and the fact that they show alot more of their bodies out of the water than basking sharks.

If IWDG accepted every record of "breaching whales" in the coming months, our database would suffer from inflated numbers of whale sightings, at the expense of important shark records. So before assuming you've just witnessed a breaching whale, ask yourself, could it have been

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