Jellies, jellies everywhere
January, 2003
During the winter months we have experienced a great influx of Jellyfish in the waters around Oman. The most commonly seen is a species of the Genus Crambionella shown in the photographs below.

They can be seen floating or actively swimming in mid-water, piled up in 'drifts' in crevices between rocks and washed up on the beach at low tide. The generally accepted reason is the high concentration of plankton in the coastal waters at this time of the year which provides a rich source of food.

To divers, swimmers and beach strollers Jellyfish are a nuisance. They belong to the animal phylum Cnidarians. along with corals and anemones. All Cnidarians have stinging cells called nematocycts which they use to catch and immobilize their prey.
Divers or swimmers who brush against the tentacles of floating Jellyfish can get stung. Usually the encounter is harmless because the nematocysts are not able to penetrate human skin. However, in the case of a few species where penetration takes place painful stings will result.
The most dangerous of all Jellyfish - some say of all marine creatures - is the Australian Box jellyfish (Chironex fleckeri). The sting of this species is usually fatal.


For the reef fish that live along the coast the influx of jellies is a valuable source of food. The picture on the right above shows a Blackspotted butterflyfish (Chaetodon nigropunctatus) feeding on a Jellyfish. We have seen many with all their tentacles and part of the body itself, called the bell, eaten away. If you look closely at the jelly in the photo on the left you will see that little bits have been nibbled away from the outer edge of the bell.
Larger Jellyfish are used as a floating nursery by a variety of fish species. The tiny juveniles shelter amongst the tentacles of the jelly the same way as clownfish amongst the tentacles of the Sea anemone.

The photo above shows a very shiny little fish, probably a juvenile Alectis jack, hiding amongst the tentacles of a large jelly of the genus Cephea, getting a free ride as well as protection from predators.