Eels are teleost fish that belong to the order Anguilliformes. Over 800 species of eels exist, some of which are classified as the more common freshwater eel, and others as marine eels. The two types of marine eels are Moray eels and Conger eels. The most apparent characteristic of eels is their elongated body. Both varieties of freshwater and saltwater eels will have a long, continuous fin down their back, which actually is the dorsal, caudal and anal fins fused together. Only freshwater eels have small pectoral fins towards the front. Moray eels vary in size but are generally the largest eels, with Conger eels reaching larger sizes than freshwater eels. Moray eels also have an elongated snout, large eyes, and a large mouth with two lines of teeth.
Eels spawn in the open ocean water column, with freshwater eels migrating from fresh to saltwater during these times. Eels are free-spawners whose free-floating gametes become fertilized eggs that develop into larvae known as leptocephali. Larvae will then develop into what are known as glass eels, followed by the elver stage, before reaching the inevitable juvenile and adult life stages. Eels are carnivorous with a diet of fish, mollusks, crabs and other hard-shelled invertebrates. Most are ambush predators that will spend most of their time rock crevices, caves or cracks. Conger eels are bottom feeders with a similar diet. Conger eels live in bodies of water near European and American coasts, while Moray eels are found worldwide in both deep and shallow water. Moray eels can be found around coral reef areas, usually in warmer temperature waters.
Eels are a common food item in Japanese, and some Chinese, cuisine. While eels’ blood is actually toxic to mammals, including humans, the heat from the cooking process will destroy the toxic protein. A lapse of time and even the digestive process itself will also destroy the protein. Moray eels are popular attractions at aquariums. While they may appear threatening with their large mouths open frequently, this gaping behavior is actually just to allow water to pump through their oral cavity and over the gills. Snorkelers and divers are advised to remain cautious and avoid harassing eels in the wild, least the eel become aggressive and strike with lightning speed. There are a few eels that have been placed on the IUCN Red List of Endangered Species: the freshwater eel, Japanese eel, and European eel. The main cause for low recruitment rates is difficult to determine because of the eel’s life cycle. It could be the result of climate change, predation, habitat loss, migration barriers, or something else. Sustainable practices are in effect, with the most common method of recovery being restocking a certain percentage of captured eels back into their habitat.