These are the jellyfish you are perhaps most likely to see around the shores of Minorca (based on many years observation whilst windsurfing, surfing and beach walking). There are a few other species that are less prevalent, though still common, which haven't (yet!) made it to this page.
Velella velella - Sailor by the wind
Some years there are a truly astonishing number of Velella when it can literally carpet the surface of the sea, or be stranded on beaches in huge numbers. The jellyfish (or more correctly hydroid polyps) are only a few centimetres across and consist of a disc-shaped raft with an upright sail that catches the wind. They are closely related to the Portuguese Man o' War (Physalia physalis) jellyfish, which is also distributed by surface winds. However, unlike the Man o' War, Velella has very short tentacles (only a few millimetres) and its sting cannot be felt by humans.
There are 2 symetrically different forms of Velella, which differ in the position of their sails. This results in each form sailing a different course (much like yachts on different 'tacks', or left and right flipflops seperating as they are blown by the wind from a common start point).
Velella is entirely harmless but and in any case can easily be avoided by choosing beaches where the winds are blowing offshore. Decomposing plagues of Velella (such as may be found stranded on a beach after a period of stormy weather) can be quite smelly.
Pelagia noctiluca - Purple-striped Jellyfish
This species is widespread throughout the Mediterranean and Atlantic. They have some capacity for independant movement but mostly end up going wherever the currents take them. Near the shore this means they may become concentrated in particular areas together with natural organic marine debris and (man's less natural contribution) floating plastics.
The colour of this jellyfish ranges from brown to purple. Although the body is relatively small, usually only up to around 10cm across, it trails fine tentacles which are capable of delivering a painful sting and often leave a whip-like scar. In rare cases of allergic reactions, life-threatening conditions like anaphylactic shock can occur.
Consequently even relatively low numbers of this jellyfish can make bathing unpleasant and most years there are some days when, at some beaches, you would choose not to swim. However it is usually only beaches on a particular coast that are affected (depending upon the wind direction) so there are usually alternatives available. If the wind has been blowing offshore for a while this will tend to take the jellyfish away from the coast. Rough sea conditions will also tear apart these delicate creatures.
Higher concentrations of these jellyfish sometimes occur (particularly in winter) that can complicate immersion watersports such as surfing and windsurfing. Concentrations high enough to turn the sea black have occasionally been observed.
Cotylorhiza tuberculata - Mediterranean jelly or fried egg jellyfish
This is one of the larger Mediterranean jellyfish and typically reaches around 35cm in diameters. It is common around Minorca from mid-summer to Autumn.
By jellyfish standards this species is capable of a significant degree of autonomous movement, which perhaps explains how it is often observed in groups and why it is rarely found stranded on beaches. It also migrates vertically enabling it to escape rough seas.
Despite its size C.tuberculata presents no real inconvenience to water users. Its tentacles are short and their sting cannot be felt by humans (or is, at worst, extremely mild). It also tends to keep to deeper water. It is in fact a rather attractive jellyfish and frequently provides home to a number of small fish. The colours it develops are thanks to a symbiotic relationship with unicellular algae.
General Jellyfish Sting Treatment
- Rinse the area with sea water. Do not scrub or wash with fresh water which will aggravate the stinging cells.
- Deactivate remaining cells with a vinegar rinse before removing them, otherwise inactive cells may be triggered. If no vinegar is available then urine is a possible alternative.
- Lift off any remaining tentacles with a stick or similar. If cells still linger, dust with flour and carefully scrape off with a blunt knife.
- After all tentacle sections have gone, pain can be treated with a cold pack and/or a local anaesthetic such as a sunburn lotion or insect bite treatment that lists '...ocaine' as an ingredient.
- If there is continued swelling, or itchiness, apply a light steroid cream e.g. Hydrocortisone eczema cream.
- If muscle spasms persist see a doctor.
Portuguese Man 'o War Sting Treatment
[These are still very unusual around the Balearics, stings are very painful but only usually life threatening if the victim has an allergic reaction.]
- Rinse with salt water NOT VINEGAR.
- Lift off any tentacles with a stick or similar.
- Apply an ice pack.
- Apply a local anaesthetic (sunburn cream/insect bite cream).
http://www.flickr.com/photos/sublimedesign/244549131/ (picture of Velella)