Originally Posted by recedite
It's busy enough with shipping and leisure craft, I think they would be known about if they were there. We know about resident bottlenose dolphins (fungi) and the transient groups visiting the shannon estuary. If you were to follow the coast in a boat,as a circumnavigation, you would not find any huge sealion colonies (or any sealions at all) but you would find a steady supply of small groups of seals. 5 or 6 in a cove here and 20 or 30 hauled up on a sandbank there. Also plenty of porpoises. A GW or pod of Orcas could presumably keep patrolling the coast with regular forays out to sea for large fish. But then we would have seen them. What deters them from staying around?
As stated earlier in this thread, Atlantic Great Whites are not known to predate on seals to any great degree, they specilize on fish prey, with the deep swimming six gill shark being one of their main prey species. So why would they be seen near the surface or near the shore?
The Orca pods around Ireland and Britain have long been known to be mainly fish hunters also, so why would they follow the totally different behavioural traits of Orca that prey primarily on marine mammals.
You seem to be working on the assumption that the large predators that are in Irish waters, and the large predator that may come into Irish waters are feeding and hunting in a manner that Atlantic Orca and Atlantic great whites do not do, which is predate mainly on marine mammals.
If we were discussing Orca and indeed great whites off the West Coast of America for example, then what you are saying would stand up, as both species there prey mostly on marine mammals, and as such get seen much closer to shore, and much nearer the surface.
Just as an example of the size of a six gill shark compared to a seal, here is a picture of a six gill caught off of the Clare coast earlier this year. Plenty of eating in these guys, and as said earlier they live in deep water, and are known to be one of the main and preferred species that the Atlantic Great whites prey upon.
Also this year another species that the Atlantic GW preys upon was found in large numbers off of the Kerry coast, and it is another member of the cow shark family, the seven gill shark. This discovery is the one that has drawn the interest of marine biologists, as it is the most common cow shark, and everywhere else on the planet where it is in numbers, the great white shark has been found.
Just to correct you on something you said about the bottlenose dolphin. You called the dolphin in the Shannon estuary transient. That is incorrect, the bottlenose dolphin there are the ONLY known resident bottlenose dolphins in Irish waters, they are not transient at all.
Plus they are not preyed upon by the Orca in Irish waters and have often been seen swimming together. Fish eating Orca do not pose a threat to Dolphin unless the Orca is literally starving.