Jellyfish in Vieques, Puerto Rico

Jellyfish in Vieques, Puerto Rico

By Stephanie Velazquez

Ouch, they sting, they hurt, and you sure don't want to stay near them! Jellies are simple organisms made of water. To be exact, they are 95% H2O. Jellies have no brain, heart, or blood. There are approximately 200 species in the world. We find them extremely elegant as they float in the ocean, which is the contrary when taken out of the ocean. They look like gelatine blobs when they are out of the ocean. Jellies do not have supportive internal or exoskeleton; they simply have three principal cell layers: epidermis (outer layer), gastrodermis (inner layer) and mesoglea (middle layer). The middle layer, mesoglea, is the layer responsible for giving the jelly their jellylike quality. It is also responsible for buoyancy and helps the jellies maintain their shape underwater.

The tentacles that extend from the bell, or the body, are often armed with nematocysts (stinging cells), which they use as a defense mechanism to immobilize their prey. The potency of the venom in the stinging cells varies from species. Some species may cause welts on human skin, and interfere with the central nervous system. Luckily, we don't have poisonous jellyfish here on the island like the box jelly that inhabits in Australia. 

Three types of jellies we have encountered around Vieques 

1.) Moon Jellyfish (aurelia aurita): This is one the most common jellyfish in Puerto Rico. They can grow about the size of a plate. You are able to recognize them by the four circles they have on their bell, or body. These circles are purple and they are actually gonads, the reproductive organs at the bottom of the stomach. 

2.) Upsidedown Jellyfish (cassiopea): Upsidedown jellyfish are a type of jellyfish that is common as well in the island. We encounter them at bays like Tres Palmitas, Bahia Tapon, and Puerto Mosquito (Mosquito Bay). They will always be near seagrass. You will notice that they are usually seen at the bottom of the bay upside down on the top of its bell, with the oral arms or tentacles upwards. 

 3.) Sea Nettle (chrysaora quinquecirrha): A jelly we should all watch out for is the sea nettle. Although it not dangerous or poisonous to humans, the sting is a lot more painful than getting stung by a moon jelly or upsidedown jellyfish. 

What do jellyfish eat?

Jellies usually feed on copepods, which are crustacean zooplankton. They also feed on fish eggs, small plants or small fishes. They immobilize their prey with their tentacles. Then, they pass them to the mouth. They are not all active predators, for example, the upsideown jellies harbor zooxanthellae algae, which delivers the nutrients to their host. 

How can I get stung? 

Luckily, these ocean creatures are not out to get you. They don't actively pursue humans. Most of the time when humans get stung by a jellyfish is while plainly not being aware of their surroundings. You can happen to bump into them accidentally and stinging immediately upon contact will occur. 

An item we have made part of our first aid kit during a Snorkeling Tour is vinegar. It won't take the pain entirely away, but it sure helps alleviate it. A good idea during jellyfish season would be to wear a wetsuit that would cover your entire body, or rashguard along with long pants or yoga pants. You can also find rashguard pants online. One of our favorite brands for ocean gear is Mares

It is always ideal going into the ocean with a local expert, especially if you are not familiar with the location. A local guide would be able to take you to locations where there aren't as many to no jellyfish at all during the scheduled tour. In case of an encounter with these ocean creatures, your guide is also able to re-direct the jellyfish away from your body saving you from getting stung, this while not getting stung themselves. 

When is jellyfish season in Puerto Rico? 

We have noticed the jellyfish bloom during August through the end of October. 

Jellyfish Predators 

In the past, populations of jellyfish were kept in balance by predators like sea birds, sea turtles, tuna, certain types of angelfish, filefish, and other types of jellyfish eating fish. Unfortunately, due to the depletion of these predators, jellyfish populations are growing at an alarming rate. These blooms are problematic for both swimmers and the islands' tourism industry.

Even though these ocean creatures seem so fragile, they are able to thrive in negligible conditions. Some reasons for these blooms include overfishing, which removes jellyfish predators, warming ocean caused by climate change, pollutants that stimulate rapid growth of the plankton food sources preferred by the jellies, and hypoxic sea conditions that jellies are able to tolerate, such conditions unbefitting for the fish.




Reef Life – A Guide to Tropical Marine Life; Brandon Cole; text: Scott Michael; Pages 470-476.