Eels are elongated, fish-like aquatic creatures found in diverse habitats across the globe. These animals are primarily predatory. Their diets vary significantly, influenced by their environment and stage of life.
General Feeding Habits
Eels are carnivorous, consuming a diverse array of prey. They are largely opportunistic feeders, adapting their diet to what is available in their surroundings. Common prey categories include small fish, crustaceans such as crabs and shrimp, various worms, and insects. Some larger eel species may even consume amphibians, reptiles, or other eels, demonstrating their adaptability. Eels utilize their elongated bodies and keen senses to locate and capture food.
Freshwater Eel Diets
In freshwater environments like rivers, lakes, estuaries, eels primarily consume prey found there. Their diet often includes aquatic insects and their larvae, such as mayfly nymphs, caddisfly larvae, and midge larvae. Freshwater crustaceans like crayfish are also a common food source. Small fish, amphibians such as frogs, and even carrion can supplement their diet. Freshwater eels are often nocturnal, hunting at night and using their strong sense of smell to find prey.
Marine Eel Diets
Marine eels, found in oceans and coral reefs, feed on a different range of prey found in saltwater environments. Their diet frequently includes various types of fish, cephalopods like squid and octopus, and larger crustaceans such as crabs and shrimp. Moray eels, for instance, are ambush predators, often hiding in crevices and striking quickly at passing prey. Conger eels, while also opportunistic, actively hunt fish and cephalopods in open water or scavenge for dead fish on the seabed.
Dietary Changes Across Life Stages
An eel’s diet transforms considerably throughout its life cycle, reflecting its growth and migration. The earliest stage, the leptocephalus larvae, primarily feed on particulate organic matter, often referred to as “marine snow,” a mix of detritus and biological materials.
As leptocephali metamorphose into glass eels, they become more active feeders. Upon entering coastal or freshwater environments, their diet shifts to small invertebrates, detritus, and planktonic organisms. Elvers, a more developed juvenile stage, continue this carnivorous transition, consuming small insects and very small fish, often non-selectively based on availability. Adult eels then adopt the varied and substantial carnivorous diets, consuming larger fish, crustaceans, and other aquatic organisms.