Prawn sandwiched between nets and nurture

ANOTHER LIFE:LIVING WITH such a far horizon and so much that is still unknown about the sea, I seize eagerly upon any new maps of Ireland's ocean. We have had those magic, sonic readings of the seabed, right out to the shelf edge, the great Rockall Trough and Porcupine Seabight, and the abyssal plain beyond. Now, with the contours of that vast and Tolkienesque landscape revealed, we have pictures of the human hunt for seafood spread out across it – pictures painted, appropriately, in swarming, tiny dots.

Each dot records a trawler, from some European port, at some point over the past five years. That is the age of the VMS, the EU’s vessel monitoring system. When any sizeable trawler – more than 15 metres – is at sea, it must report its position by satellite at least every two hours. This is raw data from which the Marine Institute has spun such revelatory maps.

In its Atlas of Commercial Fisheries (downloadable free at www.marine.ie), the maps show where the trawlers spend most time, and the relative measure of fishing effort by each nation’s fleet. Especially dramatic are the great swirls of the French and Spanish fleets fishing within Ireland’s Exclusive Economic Zone for hake, anglerfish (monkfish), megrim and more.

On the map of Ireland’s fishing effort, three big red blobs of dots stand out: one just west of the Aran Islands, another in the western Irish Sea, off Dundalk Bay, another off the south-east in the Celtic Sea, half-way between Wexford and Cornwall.

Here are three large patches of muddy seabed, home to billions of Nephrops norvegicus, the miniature lobster that is neither a prawn, nor lives in Dublin Bay. As the Dublin Bay Prawn, nonetheless, it can reach 8cms long, for posh restaurants, or, at a quarter that size, can be minced up into tubes and squeezed out into concealing batter as mouthfuls of “scampi”. Next to mackerel, and described simply as prawns, it is Ireland’s most valuable sea-catch, worth €31 million at the quay.

Hence the relief last month at the annual EU fisheries negotiations when the threat of a precautionary cut of 50 per cent in Nephrops catches was finally whittled down to a mere 9 per cent. The clash of science and politics habitually works against conservation, but there were real complications in this instance. A uniform cut for EU waters would have taken no account of local variation, not least the Marine Institute’s own view that the prawn stocks on the main Irish grounds are “relatively stable”.

Despite Nephrops’ sedentary habits in the right sort of mud – ideally a sort of chocolate mousse – assessing their numbers and reproduction rates has proved notoriously difficult. For one thing, they spend much of their time in branching

burrows, perhaps a metre or more long, and their emergence depends on time of year, tidal strength and intensity of light.

The females have been holed up for the winter, incubating their next clutch of eggs. The males come out, mainly at night, to scavenge and battle over territories, and the annual moults of the growing young take them back to their burrows for protection.

All this, plus huge fluctuations in catches, has driven researchers to making annual surveys with television cameras pulled along on sledges – recording, say, 10-minute tows on DVDs, spaced out on the Nephrops grounds. Counts of burrows and their density in the mud are matched to water temperature, depth, salinity and samples of mud. For example, on the grounds at the back of Aran, says the Marine Institute, “around a billion burrows”, averaging one per square metre, supply the main catch of the trawlers of Ros a Mhil in Connemara. But they fluctuate considerably in space and time.

A fourth notable location for Nephrops has been patches on the Porcupine Bank, which in the 1980s yielded landings of more than 4,000 tonnes to Irish and Continental trawlers. Following a collapse in catches, a proposal for seasonal closures, originating with Irish fishermen, was adopted by the EU.

Since the main predators of Nephrops, including cod, rays and skate, have been so grievously overfished, their present productivity is not, perhaps, surprising. Skate has long vanished as a catch in the Irish Sea, where the lights of massed prawn trawlers can sometimes resemble a floating town, and the discarding of juvenile cod and whiting caught in Nephrops trawls became a part of collapsing stocks.

Since 2000, square-meshed and other separator panels, allowing many fish to escape, have been fitted into many Nephrops trawls, not only in the Irish Sea, but on the west and south coasts. But even more selective gear is needed if we are not to be left with a choice between prawns and jellyfish which, we are told, are fast taking over the seas.

EYE ON NATURE

We have an aggressive blackcap in our garden. It has got rid of the greenfinches, sparrow, goldfinches, chaffinches and tits from the nut and seed feeders, attacking all visitors.

Willi Kiefel, Tuam, Co Galway

Separate the feeders as far from each other as possible.

During the cold months three of the local water hen population took to banging on my office window for a share of my lunchtime sandwich.

Tom Wade, Santry, Dublin

I received a wonderful book entitled Bird Brains: The intelligence of crows, ravens, magpies and jays. In it is a quotation from Rev Henry Ward Beecher (1850s): “If men had wings and bore black feathers, few of them would be clever enough to be crows”.

Louis Mullen, Riverstown, Co Louth

Before Christmas, on Ballybay Wetland walk, we saw a great white egret. It stayed near enough to get great views. It remained in the area for some time.

Elsie David Nesbitt, Ballybay, Co Monaghan

They are recent immigrants. One was also seen near Kilcolgan in Co Galway during the November floods.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo. Please Include a postal address. Also viney@anu.ie