Eels of Costa Rica

Easily mistaken as sea snakes, eels are actually elongated fish measuring from the smallest 5cm to the largest 4meters and weighs from lightest 30 grams to the heaviest 25 kilos. Unlike your regular-shaped fish, eels have a slender body with no pelvic fins and many species have no pectoral fins as well. Their dorsal and anal fins are fused together with the anal fin. These characteristics have made them the masters of living and hiding in cracks and crevices.

Most eels live in shallow water, burrowing in sand or hide themselves in rocks. Most of the eel species are nocturnal and highly active during night time to feed usually on small fish, crustaceans and mollusks.

Aside from the slender body, what is common among eels is the constant opening of the mouth. Do not be confused with this as an aggressive behavior as it only facilitates respiration by bringing in water inside its mouth and through the gills.

A Profusion of Importance and Threat

Eels around the world are highly threatened either used as human food or traded as an aquarium fish. With the importance to manage and conserve the remaining eel population, we decided to include the length at first maturity in each species section. This is important for us to allow undersized eel to grow, mature and allow it to reproduce and replenish the lost population.

In most instances, there are relatively few data on species weight. But if you are lucky enough and observe an eel that is out in the open, you can estimate the weight by just determining the length and use the length-weight relationship formula: axb. The a and b values are computed and constant figures and is different from every species.

For example: during your dive in Catalina Island, you saw a Panamic Green Moray Eel at about 75 centimeters long. You can now compute for the weight, with the following data:
a = 0.00195, b = 3.10 and x = 75.

0.00195(75)3.10 = 1,266.9 grams or roughly 1.3 kilos

Take note that the formula is applicable to all fish species. So you should remember and be familiar with this as we will be using this method in other species of fish.

Costa Rica’s Eel Variety

There are 800 species of eels found worldwide. In Costa Rica, there are over a hundred species of eels found along the coast and deep-water environments. Here are some of the common species that you may encounter during a dive.

Panamic Green Moray Eel (Gymnothorax castaneus)

Max. Length: 150 centimeters
Length at 1st Maturity: 76 centimeters
a value: 0.00195
b value: 3.10
Weight:
Depth Range: 3 – 36 meters (10 – 120 feet)
Frequency: Common, but highly vulnerable to aquarium fish trade

Photo courtesy from Wikipedia

Photo courtesy from Wikipedia

Also called as the chestnut moray eel, this large eel can grow up to 1.5 meters in length. This brown to brownish green colored species usually lives in rocks, boulder strewn and vertical environments like a reef wall. You can see them lurking in holes, crevices and dark spaces during the day but goes out in the open and feeds at night. This species occasionally go out during the day especially in sandy areas but not too far from their hiding places to feed on small fish and crustaceans.

Spotted Moray Eel (Gymnothorax moringa)

Max. Length: 200 centimeters
Length at 1st Maturity: 100 centimeters
a value: 0.00102
b value: 3.070
Weight: 2.5 kilograms
Depth Range: 5 - 200 meters (17 – 660 feet)
Frequency: Common, but highly vulnerable to aquarium fish trade

spotted-moray-eelAlso named as the speckled moray eel, this eel has a relatively long snake-like body having a white to pale yellow in color. Their common length is usually at 60 centimeters but they can grow up to 2 meters. They are usually found in shallow rocky to grassy areas on the reef. Although their main diet are fishes and crustaceans, be cautioned as this species of eel are known to be quiet aggressive to humans. So keep a safe distance. Spotted moray eels have become popular as an aquarium fish and have been traded worldwide.

For more information, please read our species related article http://www.costarica-scuba.com/spotted-moray-eels/

Zebra Moray Eel (Gymnomuraena zebra)

Max. Length: 150 centimeters
Length at 1st Maturity: 77 centimeters
a value: 0.00112
b value: 3.06
Weight:
Depth Range: 3 – 50 meters (10 – 150 feet)
Frequency: Common, but highly vulnerable to aquarium fish trade

Photo courtesy from Next Door Zoo

Photo courtesy from Next Door Zoo

This medium-sized eel can reach a maximum length of 1.5 meters but it has a common length of half a meter long. It’s short round snout with a densely banded dark and white color pattern of its body has been the main reason of naming this species. Zebra moray eels are highly active at night where they primarily feed on crustaceans, sea urchins and mollusks. Although they are harmless to humans, keeping a safe distance is still highly recommended.

Yellow-Edged Moray Eel (Gymnothorax flavimarginatus)

Max. Length: 214 centimeters
Length at 1st Maturity: 116 centimeters
a value: 0.00040
b value: 3.3350
Weight:
Depth Range: 5 – 150 meters (17 – 500 feet)
Frequency: Common, but highly vulnerable to aquarium fish trade

Photo courtesy from Matthew Meier

Photo courtesy from Matthew Meier

Yellow-edged moray eels are usually found in rocky areas with a generally flat terrain and along drop-offs. You can easily identify this kind of eel by its yellowish color with a dense mottled brown body. The front of its head has a purple to grey color and the eyes are sometimes observed to be red. They are highly sensitive to injured or stressed out fish where they can easily hunt them. Although they are eaten in some parts of the country, be aware that their meat contains ciguatera which is a kind of chemical harmful to humans.

Tiger Snake Eel (Myrichthys maculosus)

Max. Length: 100 centimeters
Length at 1st Maturity: 53 centimeters
a value: 0.00151
b value: 2.91
Weight:
Depth Range: 3 – 250 meters (10 – 800 feet)
Frequency: Common, but highly vulnerable to aquarium fish trade

Photo courtesy from Robert Harding

Photo courtesy from Robert Harding

This medium- sized eel has an average length of 50 centimeters but can attain a maximum length of 1 meter. It has a pale cream body color with dotted patterns of large and small black dots. Their behavior involves total exposure in open sandy flats in search for food. Although, they are usually solitary during the day but when you go night diving, you can see them in aggregates while simultaneously searching for food.

Abbott’s Moray Eel (Gymnothorax eurostus)

Max. Length: 60 centimeters
Length at 1st Maturity: 34 centimeters
a value: 0.00195
b value: 3.10
Weight:
Depth Range: 3 – 75 meters (10 – 250 feet)
Frequency: Common, but highly vulnerable to aquarium fish trade

abbotts-moray-eel22-1024x768Discovered by Abbott, a taxonomist in the year 1860, this eel is characterized having a purple to brown body with small yellow spots scattered around. Also called as the Stout Moray Eel, they are usually found in shallow water and has been known to be a voracious nocturnal feeder.

For more information, please read our species related article http://www.costarica-scuba.com/abbotts-moray-eel/

References

Wikipedia: https://en.wikipedia.org/wiki/Panamic_green_moray_eel
Fishbase: http://www.fishbase.org/summary/Gymnothorax-moringa.html

video courtesy from Ken & Esther’s World Adventures

Tristan Paylado

a.k.a. TRIX, is a Marine Biologist, CMAS 2 Star Dive Instructor and a proficient writer that thinks like an octopus but acts like an Orca.

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