NATURE Mapping Mayo’s seas

Outdoor Living
Mapping Mayo’s seas

Marine Life
John Paul Tiernan

To map something is to record, or graphically represent, in one document, its features, boundaries, populations, activities and other important points of interest. Straightforward enough on land, but how does one map the unmappable? The great expanse of ocean which lies to the west and north of this county, for example. Its shifting currents, dynamic, ever-changing populations and its lucid and fluid bulk makes virtually everything that lies beyond the first few metres an unmapped mystery.
How would one create a comprehensive atlas of this part of our world? And what would it include? The Marine Institute, under the MEFEPO (Making the European Fisheries Ecosystem Plan Operational) project, have risen to the challenge and created the North Western Waters Atlas, a 168-page document which allows us to look to the waters off Mayo in a more-informed way than ever before.
It includes, besides the obvious geographical concerns of area and depth, the directions and speeds of the relevant currents and water movements, the climatic details of the area, the habitat of the sea floor, the sea birds that occupy the coast and offshore, the nutrient inputs and what happens to them, the plankton that blooms and is consumed throughout the year, the reptiles that visit from the south and the timing and distribution of the seals, whales and dolphins that endlessly please.
Human activities, such as mariculture (fish and shellfish farming), seaweed harvesting, oil and gas exploration, renewable energy, leisure use, and transport and shipping, are also accounted for. Who knew this was such a busy place?
Of particular interest to a lot of people will be the fish-spawning areas, distributions of juvenile fish and the fishing effort – that is, where people fish, when and how much. Here, the atlas reveals gems of information, such as the mackerel spawning grounds that occur off Mayo in March but shift southwards as the season continues. Distribution of juvenile Mackerel is, unsurprisingly, greatest in Mayo as well, with the atlas showing sizeable populations to the north and west of Belmullet.
In line with these fish population profiles, the atlas also shows an impressive fishing effort off our county’s coast, which makes one wonder, how many of these boats come home to harbours in Mayo?

The North Western Waters Atlas is freely available to download from the Marine Institute’s website,

John Paul Tiernan
, Louisburgh, runs, a website dedicated to the creation of knowledge of our marine ecosystems. He is currently studying for an MSc in Marine Science.