• HOME
• COURSES
• DIVING
• DIVE SITES
• EQUIPMENT
• INJURIES
• LESSONS
• SEA LIFE

Home › Sea Wildlife › Marine Species › Vertebrate › Catfishes

Interesting Facts about Catfishes

[Catfish Phylum: Chordata] [Class: Actinopterygii] [Superorder: Ostariophysi] [Order: Siluriformes]

The vast diversity and global distribution of more than 3,000 different species of catfishes comes from an amazing adaptability to colonise many of the most challenging habitats.

This section contains a collection of little-known facts about catfish (Siluriformes), including where they live, what they eat, and how they reproduce.

Catfish Worldwide Distribution and Habitats

Excluding Antarctica, you can find members of the catfish species living in every continent.

Nonetheless, the geographical hotspots for this group of ray-finned fish are the inland and coastal waters of:

• Asia (especially the Mekong River)
• South America (the Amazon River) and North America (the Mississippi, Missouri, and Ohio River basins)
• West-central Africa (the Congo River)

Catfishes mainly live in fresh water as well as some brack water environments. Most of the species thrive better in shallow, murky bodies of water (for maximum camouflage) with moderate movement, such as rivers, streams, and ponds.

Others can tolerate the 'unpredictability' of lakes, vernal pools, swamps, and floodplains. But, they get the benefit of nutrient-rich feeding grounds when seasonal flooding occurs.

Interesting Fact: At least eight catfish families actually live underground (hypogean), such as the cistern catfish (Phreatobius cisternarum), and three other families spend their lives inside caves (troglobitic) with oxygen poor water (hypoxic).

Catfish Characteristics and Behaviour

They belong to the order Siluriformes, and they look like electric eels (Electrophorus). So, it is fair to call catfishes one of the most diverse groups of all marine vertebrates.

The species may not have the funniest fish names in the spectrum. Even so, the "whisker-like" barbels that dangle from their mouths are the reasons behind the catlike common names.

In fact, the barbels are sensory organs that help them locate food in dark or silty water. The body of most catfishes is scaleless, yet the skin is smooth, and usually covered in a protective layer of mucus.

But wait - there's more:

Some species of catfish have modified respiratory structures that they use to breathe air "directly" - such as those living in hypoxic environments.

Other Siluriformes are known to have sharp spines that contain potentially lethal venom to humans. The venomous catfish species produce a potent protein in the tissue that covers their prominent dorsal and pectoral fins (Plotosus lineatus for example).

Most of these bottom-dwellers are comfortable forming large shoals. Others live a solitary life and tend to be more territorial in nature.

Catfish Size and Weight

With more than 3,000 different catfishes, the range of sizes and weights varies tremendously throughout the species.

One of the smallest is the pygmy catfish, which rarely grows more than three (3) centimetres long (one inch).

Whereas, the largest freshwater fish in Southeast Asia is the official contender for the biggest catfish in the world.

Fully grown adults can be three (3) metres long (10 feet) and weigh more than 300 kilograms (660 pounds).

What Do Catfish Eat?

Catfish are generalists (meaning they eat almost anything they find) and they are scavengers. Many of them are also nocturnal and more active during the dark hours.

Some of the omnivorous catfishes tend to be more opportunistic with their diet, and regularly feed on organisms such as:

• Aquatic insects (and insect larvae)
• Crustaceans (e.g., crabs, crayfish, shrimps)
• Detritus
• Mayflies (Ephemeroptera)
• Mollusks (clams, snails)
• Plant material (algae, seeds)
• Small slow-moving fish
• Water beetles

Even so, there are some predatory catfish species (such as the flathead catfish) that prefer to consume live prey, and the candiru catfish (Vandellia cirrhosa) is one of the parasitic scavengers that enters the gill cavities of other fish.

Fun Fact: Having multiple taste buds all over their body means that catfish are amazingly sensitive to taste - the ideal attribute for scavengers that hunt in cloudy and turbid environments.

Different Types of Catfish Species

How Do Catfish Reproduce?

Catfish reproductive strategies vary according to the species. Even so, many display morphological characteristics (sexual dimorphism) and follow these general patterns.

Seasonal floods, rising water temperatures, and extended hours of daylight, are the usual triggers for the start of the spawning season.

Even though many catfish species build nests, they also have their preferred locations. For instance, some of the nest builders (usually the males) will choose holes in riverbanks or within dense vegetation, and others will build their nests underneath sunken logs.

Egg Laying and Parental Care

Compared with many of the typical marine vertebrate examples, it's fair to say that catfish are good parents and they take good care of their eggs.

Once the female has finished laying her sticky eggs inside the nest, often several hundred per clutch, the male goes ahead and fertilises them "externally".

In general, it's the male's role to guard the nest against predatory hunters. He also uses his fins to fan the eggs and oxygenate them by circulating the water.

Hatching into Baby Catfish

Like many of the jawfish species, some catfish are also mouthbrooders that carry eggs or "live" young inside the mouth for extra protection.

Within a few days the eggs start to hatch, and the young fry (baby catfish) rarely move far away from the safety of the nest. They will start to swim freely once they have completely absorbed the yolk sac.

Interesting Facts: The males of some catfish species are internal fertilisers that use their intromittent organ (a modified anal fin) during copulation. Others spawn inside caves, and some South American catfish (Corydoras) store their eggs inside a pouch (modified pelvic fins) and attach them to plants after they have been fertilised.

Catfish Predators and Threats

Few ray-finned species can match the toughness and diversity of the catfish families. In spite of that, they face a number of natural predators - and a few human-induced threats as well.

As a matter of fact, the reason why there are more than 3,000 surviving species of catfish is mostly due to their defensive traits, especially:

• Hardened, sharp dorsal and pectoral fin spines (some venomous) can cause injury to large predators (along with some adventurous anglers).
• The cryptic colouration and camouflage of mottled and dark skin tints helps them blend in with dim murky riverbeds.
• Having night-time feeding behaviours help to reduce exposure to many of the daytime predators (e.g., some freshwater and coastal hunting birds).

In the wild, the main animals that hunt for catfish are the large predatory fish, especially pike and muskellunge (Esox masquinongy) in North America. But other predators include:

• Birds (e..g, cormorants, herons, eagles, and ospreys).
• Mammals (such as raccoons and otters)
• Reptiles (especially alligators, large snakes, and crocodiles)
• Humans (fishing for catfish is considered as an exciting sport worldwide and many are eaten by people)

Important: An assessment released by the IUCN Red List of Threatened Species shows the conservation status of most catfishes worldwide is of "Least Concern" (LC). However, data recorded in 2011 shows that the Mekong Giant Catfish (Pangasianodon gigas) is "Critically Endangered" (CR) with a "Decreasing" population trend.

Divers also enjoyed reading about...