Irish Marine Life
inshore offshore play science coral-reefs crabs ag snámh news think imeachtaíRanching The Salmon of Knowledge
The first salmon of the 2010 season was caught on The River Moy on the last weekend in February and in the Delphi valley in the other corner of the county the day before. Almost 30% of Ireland’s total salmon catch is taken in the Mayo / West Sligo region and aptly enough, the region creates most of the quality, up to date knowledge on salmon, not just for Ireland, but for the entire North Atlantic.
Midway between these two locations, The Burrishoole fishery at Lough Furnace outside Newport has been quietly establishing itself as an internationally recognised salmon research centre since the 1950s, also becoming the world’s longest running salmon trapping facility.
The scale of research they have undertaken in that time is impressive including salmon genetics, stock enhancement with salmonoids and climate change studies.
One of the activities which Burrishoole pioneered is a most terrestrial sounding pursuit; salmon ranching. Ranching is the rearing of smolts (salmon ready for salt water) which are derived from grilse (salmon which return after one year at sea). A fish farm must provide all the food necessary in a fish’s life cycle; however ranching entails the fish living where and how nature intended once released.
Ranching, as it protects the juvenile salmon until the smolt stage produces much more fish than the river otherwise would. When the mature fish return to the river of spawning, as many as possible are caught and the eggs and milt (male gamete) harvested to spawn the next generation in the ranch’s line. Experiments on the Delphi fishery have shown good returns, matching or outdoing the native stocks’ returns from the Atlantic.
Micro-tagging and tag retrieval initiatives directed by the Marine Institute mean that Burrishoole does not just have a healthy stocky, they have a useful informative ‘herd’ of ranched fish. Data from the fish are used by the International Council for the Exploration of the Seas to determine the state of Irish stocks and according to the Irish Marine Institute, the Burishoole fishery system is one of the key index systems for salmon in the North Atlantic. This and other recent research utilising Burishoole salmon as indicators of global climate change means Mayo’s salmon are doing quite well in living up to their Salmon of Knowledge legend.
This article appeared in The Mayo News edition 16/3/2010
Monsters and Mermaids
Placed high and dry upon the clean blue pebbles by a spring tide, the mermaid’s purse I found last week was not hard to spot. Another purse some months ago was easier to miss, dark and unlovely as they are and cast as it was amongst the deposited kelp of similar leathery brown shades. That relationship of camouflage was once so necessary underwater, when the four pronged purse held a tiny shark, skate or ray and the kelp held to the rock and provided cover for the purse until its inhabitant was ready to leave. How curious that now, far from those dynamic undersea worlds, they defiantly continue this relationship as they desiccate together on the still shore, the kelp now concealing the purse from the eyes of hurried beach walkers.
The purses, egg cases which once protected a fertilised embryo, are the unremarkable reproductive clue to species such as the dogfish, our smallest and most common shark. But not all sharks reproduce like this. Mayo’s legendary basking sharks, which once entertained enough mystery in their labelling as a sea monster as Gaeilge (An Liabhán Mór) are still almost a mystery to scientists in this regard. It is believed the sharks give birth to live young, but a pregnant female has only ever been seen once and nobody knows when or where or how many young are born. Porbeagle sharks which have been landed in Clew Bay definitely do give birth to live young, usually four at a time. And although they won’t be found in Clew Bay anytime soon, its worth noting the female hammerhead shark which gave birth in a zoo in The U.S. in 2001 – despite no male contact in three years. Sharks are apparently capable of such immaculate feats, but only in extreme circumstances and it’s bad for genetic diversity.
The un-immaculate mermaids’ purses are not so dramatic. And the almost blind dogfish, which spends 23 hours a day dozing on the seafloor, is no hammerhead, but there is still useful information to be gleaned from them. Compiling records of their distribution can provide valuable information on the location of nursery areas of sharks, skates and rays. Many of these are severely threatened such as the common skate, which was once found throughout European waters, now ironically titled as it is only found in a few select locations. Purse Search Ireland are one group who have undertaken the task of compiling this info, and provide a user-friendly online form at www.marinedimensions.ie for you to log your report.
Sharks, skates and rays are related and together make up the Elasmobranch class of fish, a very ancient class dating back 400 million years. They are different to other fish having cartilage skeletons instead of bone. The Dogfish (Sycliorhinus canicula) is found all around our coastline in sandy bays and off-shore. It feeds mostly on prawns, crabs and occasionally fish. They breed annually, and nine months after mating, the female lays approximately 25 eggs which develop inside mermaid’s purses for nine months. The Basking Shark (Cetorhinus maximus) is a filter feeder, passively filtering small fish, invertebrates and zooplankton near the surface with its gaping mouth open. Recent satellite tagging studies have confirmed that the some sharks undertake huge migrations in winter. They were almost fished to extinction in the west of Ireland until the 1970s but are now believed to be making a recovery.
The violence of our peaceful seas
Normal North Atlantic order has restored itself after a most remarkable 4 weeks in Ireland’s recent meteorological history. It will be hard now to discern any surface goings-on between shore and horizon with wind and swell likely to run for weeks on end as they often do in January and February, driven to us by lows sweeping across from Newfoundland in our general direction.
These lows stopped for that extraordinarily Siberian month, blocked by a strong high pressure air- mass to our North which made for a very still Atlantic allowing me one evening to sharply define the space between caudal fin and ocean and see through the burst of spray between dorsal fin and sky. It could be September but for the 10 degree water I thought as the three dolphins surged powerfully high out of a flat sea and all of this silhouetted by a low cloudless sunset over Renvyle.
Such acrobatic behaviour, in particular whirling vertical leaps is more noted of the smaller common dolphin which is usually found far offshore over the continental shelf in great numbers. They are only occasionally seen inshore and that’s usually in the southwest of the country. There was not enough light to be sure but these were most likely bottlenoses, which do from time to time leap and spin like this, and bow ride and surf of course too. But then the bottlenoses are continuously surprising us. Reports of porpoises with great shark-like chunks taken from them a hundred miles or so south of here this summer led to the surprising discovery of research, mostly from Britain, on violent bottlenose attacks on porpoises.
Where the two species occur together, the most common cause of washed up porpoises’ death was attacks from bottlenose dolphins according to The British Environment Ministry. They don’t compete for food and scientists are guessing that it is a simple territorial aggression, with serious costs for the muc mhara (the porpoise is the pig of the sea in Irish). Damage recorded to porpoises includes broken ribs, internal organ rupture as well as bite marks. Have some of the many that wash up on Mayo’s shores experienced the same underwater violence? Probably, but data and studies could say for sure.
The bottlenose is not the indifferent play seeker we may have thought and neither does the muc mhara dip from cuain to cuainín in Clew Bay as carefree as it could appear.
The bottlenose dolphin (Tursiops truncatus) is grey to black above and light grey on the underside. They have a tall fin and a long, rounded beak with a curved mouth-line giving the familiar smiling expression. They are usually seen in small groups and frequently inshore where they are engaging and playful. The common dolphin (Delphinus delphis) is smaller than the bottlenose with a distinctive ‘hourglass’ colour pattern on its sides; yellow to the front and light grey to the back. Above this hourglass shape is black and below is white. They have a tall fin and a long black beak. They are more commonly seen in deeper waters in large numbers, but are sometimes seen off coastal headlands in summer. Report your dolphin sightings to The irish Whale and Dolphin Group at www.iwdg.ie
This piece appeared in The Mayo News 02/02/2010 edition
Humpback breaching – footage
A huge congragulations to everyone in The Irish Whale and Dolphin Group who was involved in getting the incredible footage seen by so many last night on the RTE News. Anyone who had not previously heard of the iwdg have now, and Ireland’s profile as a country that is aware of its stunning marine life has been raised considerably. Here is the video footage…
Remarkable weekend for whale watchers in Ireland
The Hook Head area was the location last week for some of the most remarkable large marine life activity ever witnessed in Ireland. These pictures from RTE.ie show a humpback whale breaching, with common dolphins, harbour porpoises and fin whales also present in the area. The activity was witnessed by the Irish Whale and Dolphin Group who also succesfully recovered a sample of whale flesh which will allow genetic analysis of the whale’s gender. Such information is of exceptional value given the humpbacks’ threatened status.
Read more about the event on the iwdg.ie website.
Shellfish on Bettystown Beach
Irishmarinelife received a report today of thousands of shellfish washed up on Bettystown Beach, Meath around the 12th of January. The observer was at a loss to identify the species, a light coloured and relatively large bivalve, smooth and unlike a scallop or oyster species.
After some researching it is probably the Otter Shell that she saw (Lutraria lutraria) which burrows in sand and mud substrates and is found mostly in The Irish Sea and also parts of Connemara.
There was a period of sustained easterly gales leading up to the 12th which led to the extraordinary disturbance of its habitat and its displacement onto the shore. We did not receive any photos of the event; if you have any, please send them to irishmarinelife@gmail.com.
The Irish Times – North Donegal Basking Shark Hotspot
Tiny Marine Birds, Big Migrations – Irish Times Article
Least we forget that our marine life is limited to the terrestrial and aquatic zones, we host an impressive selection of birds who live out their lives, or parts of them along our coasts.
They can be big like the sometimes coastal winter migrant whooper swan, 2 of which beat a low flightpath past me last week as I waited for waves outside Doughmakone Strand. They can also be tiny and impressively migrant as the Irish Times reports today of The Arctic Tern. They make a round trip of 44,000 miles, pole to pole to be comprehensively global, spending months between March and Septmeber on our shores.
Similar to The Common Tern, but smaller, it is considered to have the longest migration of all birds, as The Irish Times reports, making journeys over the course of its lifetime equal to three trips to the moon. Read the article here.
Read Birdwatch Ireland’s species profile here.
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