These large, prehistoric looking sharks typically inhabit deep, dark waters off the continental shelf (at depths of 200-2,500 m). However, there are a few special sites discovered off Co. Clare, by local charter skipper Luke Aston, where these apex predators can be found in relatively shallow water (50-60 m).
Video of the shark (Credit Trinity College Dublin)
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The team of scientists set out last week to learn more about this unusual shark population. Led by Haley Dolton, PhD Candidate in Trinity’s School of Natural Sciences, the team deployed modified ABUVs (patented fish-identifying video recorders) developed by Belfast-based marine survey company, Fjordstrong.
And soon after, they grabbed footage of a 4 m sixgill shark casually cruising past their lens several times. The exciting encounter occurred after the team had seen numerous more common fish species, leading one of the researchers to shout: “That’s not another dogfish!”
Haley Dolton said that “Sixgill sharks are an incredible species and this particular site off the Irish coastline is of particular interest as large, females have regularly been sighted in shallow waters.
“For some reason this area is important to them and, given that all sixgills caught by Luke Aston appear to be females, there is a suggestion that this area is important for reproductive purposes. Getting the chance to try and solve this riddle in sixgill shark biology is a very intriguing part of my PhD and could have major implications for conservation of this species.”
This sighting kicked off a series of studies by this all-Ireland team to understand why the south-west coast of Ireland is such a hotspot for elasmobranchs (sharks and rays). The intrepid aquanauts are only beginning to answer the mystery as to why the sixgills are lurking off Co. Clare and will expand their ocean exploration of this area over the next 18 months.
A huge amount still needs to be done before scientists can fully understand elasmobranch ecology and behaviour in Irish waters. The challenge for Irish marine biologists is daunting, such is the diversity (and scale) of the questions.
Ireland has the richest elasmobranch diversity in Europe, with giants like the basking sharks and sixgills regularly cruising by. It is also one of the last refugia on earth for the critically endangered flapper skate (the largest skate on earth).
These factors are reflected by the increasing attractiveness of Ireland as a destination for shark biologists (Haley’s supervisor Dr Nick Payne recently moved here from Australia where he worked with great whites and tiger sharks).
Dr Nick Payne, Assistant Professor in Trinity’s School of Natural Sciences, said: “It’s like an aquatic Jurassic Park out there! Ireland is the gateway to the Atlantic and we are increasingly amazed at how important Irish waters seem to be for these huge shark and ray species. It means we in Ireland have a responsibility to look after them.”
“Only by working together with commercial and sports fishers, conservation bodies and government agencies, citizen naturalists and the marine technology industry can we begin to realise and understand our great marine diversity – a heritage of all the people of Ireland. With this knowledge, we are better placed to manage the 90% of our state that currently lie underwater so that future generations can gasp in awe at the giants in our midst.”
Dr Patrick Collins, Lecturer at Queens University Belfast, added: “We are going to need a bigger boat… to come back here next year and collect more data – we have only just scratched below the surface.”
The research is being partially funded by the Irish Research Council and Fjordstrong.