Swarming in Stylocheilus striata

Dear John,
Thanks for these photos. I guess it is a matter of semantics. I am aware of Stylocheilus being found in large dense populations, that's why I referred Stephen to Cory Pittman's observations of large numbers of Stylocheilus drifting together in Hawaii.

The question is how or why these animals come to be together in high densities. Are they together as a behavioural phenomenon, such as migrating to a special place - like eels, or been attracted together by pheromones etc, or have they been physically washed together by water movement? Or have they have been together since they settled out of the plankton? To me, the word swarming suggests a behavioural phenomenon and my understanding of the research is that large densities of Sea Hares occur because of heavy larval settlement at a particular locality, and is accentuated by animals being washed together late in life by physical factors - waves, storms, currents - in a phenomenon which can lead to mass mortality. There is no question that they can occur in large numbers as you have illustrated. I guess the distinction I am trying to make is that dense 'crowds' of Sea Hares occur, not as the result of Sea Hare behaviour, but through a conjunction of random events - high larval settlement, good growth of food algae, good weather during growth period etc.

Hope that makes sense,
Best wishes,
Bill Rudman