The mystery has been solved – a massive phytoplankton bloom. (Red tide) These blooms simply exhaust all the oxygen from the water making fish lethargic. It happened once before here about 8 years ago, but not as severe as this one. Was offshore 20 miles today – water was same colour as in a lake after heavy rain – pure brown.

Also received an e-mail from an angler fishing locally: –

I saw your depressing website update.
Same problem in Sheephaven….3 days without a mackeral and certainly nothing more glamorous.
It appears to be an Algae Bloom (Red Tide) uncommon but not unheard of here.
Prolonged calm weather and early May/June sun ideal conditions to start it off.
Dead heart sea urchins, lug worm and shore crab a sure sign.
A lot of dead lug worm in the estuary at Ards as well as cockles.
Hundreds of dead heart sea urchins all around sheephaven beaches.Shore crabs and small flat fish obviously distressed in rock pools at Marblehill.

I am told it will pass sooner rather than later but can’t find out when the fish will return.
It is a pity as fishing started so well.
Just returned from Horn Head and surrounds …still no mackerel bur definite signs of clearer water both to look at and on the depth sounder…fingers crossed for improvement.