An email about jelly fish

HI Ian

this has been an exceptional year for blue jellies and the clear, moon jellies - the reason there are so many this year as far as I know is because the conditions for their survival has been perfect- every spring thousands of jelly fish polyps release millions of larval jelly fish simultaneously.Many years the conditions are not good and most will die - if the conditions are good a huge swarm forms - this year the combination of late algal bloom and a slow start to the summer has favoured moon jellies in our area this species is usually rare - these are the clear ones with purple half moon shaped sections around the centre. the blue jellies must have also found conditions to be good. We have had a lot of settled weather and lots of northerly winds that have moved the swarms onto our shores - in other years these creatures would most probably have ended up in the Irish sea due to prevailing south-westerly. Another theory is that as we over fish commercial fish species there is less competition for the planktonic food that both larval fish and jellies feed on so the jellies are doing better. I dont think we are quite at this stage yet but it has been seen to have happened in more enclosed areas such as the baltic sea.
I hope this helps

cheers
Matt
Curator
Blue Reef Aquarium
Newquay