YYeeaarr ooff tthhee CCaattffiisshh A monthly column about Catfish The Salty Corner meets The Year of the Catfish: Marine Catfish

By Derek P.S. Tustin

So Klaus, recognizing something is missing in our club, has begun a new series of articles in Tank Talk on marine fishkeeping. I’ll admit I’ve been tempted at times to start up a saltwater tank, and I know that several members of our club have taken the leap in the last couple of years. I’ve been reading Klaus’ new selection of articles, published under the name The Salty Corner, with some interest. In doing so, and considering the research I’ve been doing for our Year of the Catfish, I got to wondering, “Are there any marine catfish?”

Short answer is yes. Realistic answer is a bit more complicated. It appears that there is no family of catfish wherein all members of the family are marine Plotosus lineatus catfish. But there are two families of catfish, Ariidae and Plotosidae, where some species of the family are indeed brackish and marine.

Ariidae

Ariidae is a family of catfish that encompass marine, brackish and freshwater species, with the majority of the species being from marine habitats. As a group they are called “Sea Catfish” and are found in the tropical to sub-tropical zones of North America, South America, Africa, Asia and Australia (being absent from both Europe and Antarctica).

There are about 30 genera in the Ariidae family encompassing approximately 150 species. They usually have a deeply forked caudal fin, three pairs of barbels, and bony plates on their heads and near their dorsal fins. Most are mouth brooders, with the males incubating the eggs until the fry become free swimming.

The majority of species in the Ariidae family are much too large to be housed in Arius graeffei home-based aquaria, be it freshwater, brackish or saltwater, and as a result, there are very few species that are available for the aquatic hobbyist. Those that are available tend to be smaller examples of

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Tank Talk March 2013 / Volume 40, Number 07 Page either brackish or freshwater species from the family. But even these are rather large fish, requiring larger tanks. Examples of Ariidae species that are sometimes available are the Lesser Salmon Catfish (Arius berneyi), which lives in coastal streams and rivers of Northern Australia and New Guinea and grows to 38 cm (15”) in length, the Australian Shark Catfish / Blue Catfish (Arius graeffei), again from Australia and growing to 50 cm (20”) in length, and the Columbian Shark Catfish (Sciades seemanni, previously Hexanematichthys seemanni), a Central and South American catfish which can grow in excess of 50 cm (20”) in length. Notice should especially be taken of the later fish, as it is quite often sold as a freshwater species, but is actually an anadromous fish (that is, born in freshwater but living most of their lives in a saltwater environment).

In reality, there are no members of the Ariidae family that are truly suitable for maintenance in a home based aquaria due to their size, predatory nature and specialized care requirements.

Plotosidae

The second family of catfish where some marine species of catfish are found is Plotosidae. Known as “Eel-tail Catfish”, they encompass 10 genera with approximately 35 species, which are native to the Indian Ocean and the western Pacific from Japan to Australia. Around half of the 35 Plotosidae species are exclusive to freshwater, with most of those species being from Australia and New Guinea.

As suggested by the common name for the family of fish, the tail of the fish resembles that of an eel. In all cases a fin encompasses the entire back part of the body, it being a merging of the dorsal, tail and anal fins. The species in the family range in size from 10 cm (4”) up to 150 cm (60” or 5’), all have four pairs of barbels, and like all catfish, are scaleless.

However, the most important item of note is that this family of fish contains many members who can inflict painful and even fatal wounds. In some species the dorsal and pectoral fins have the ability to generate and inject a potent venom.

While some of the freshwater species are kept by dedicated specialists, the one marine species from this family that is occasionally seen for sale is the Coral Catfish (Plotosus lineatus).

Plotosus lineatus

Plotosus lineatus was first described by Carl Per Thunberg in 1787 as Silurus lineatus. The lineatus part of the binomial name is derived from the Latin word for “line” and refers to the striped colour pattern of the young adults of the species.

The juvenile of the species are entirely black. As they mature, the body colouration transforms to a rich brown, developing yellow or white horizontal stripes along the body. It is at this point where they are most commonly available in aquarium stores, usually around 4 cm (1½”) to 6.5 cm (2½“) in size. However, what is often not revealed at the time of purchase is that each of these small fish has the potential to grow to 30 cm (12” or 1’) in Plotosus lineatus size. Further, as they mature, the attractive stripped patterning fades and the brown further fades to a dull brown, leaving a rather plain looking fish.

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Tank Talk March 2013 / Volume 40, Number 07 Page In the wild the young juveniles and young adults will congregate in large schools of hundreds of fish, feeding and living as a group. It is reported that a rolling ball of these fish is a sight to behold. However, as they age they become more solitary, and in nature they separate, going their own ways. But when purchased, they are still young adults, and require a social group (recommended to be odd numbers starting with at least five fish) in order not only to thrive, but even to survive. If kept solitarily, they will die.

Their native habitat is around coral reefs (the only species of marine catfish to be found around coral) in the Indo-Pacific, usually just above sandy substrates. They will dig through the substrate, using their barbels to locate food. As they age solitary specimens may be found in water as deep as 30 m (100’), and have been known to enter freshwater rivers where they can survive for a short period of time.

In captivity, the substrate of the tank should be sandy to replicate the native habitat. While found around coral reefs in nature, they should not be considered for a traditional reef aquarium as, while they will not damage the coral, they will eat all fish and invertebrates smaller than themselves, pretty much destroying the integrity of a reef eco-system. They are also known to inadvertently damage coral in pursuit of smaller fish and invertebrates. Appreciating good water circulation, they also require areas of calmer areas in the aquarium. They are good co-habitants with fish equal to or larger in size as themselves. Lighting should be bright, with several shaded areas or caves so they can hide.

Breeding has not been recorded in the aquarium, but in nature they spawn during the summer months. The male will dig a nest in the substrate, usually in a shallow rocky area and then try and entice the female to the nest to mate. The male will guard the small eggs until they hatch.

They are omnivorous, and in captivity should be fed a variety of fresh or frozen seafood and flake food at least twice a day. As they naturally search the substrate for food, the best method is to have meaty foods sink down to the substrate.

It once again must be emphasized that these are very venomous fish. The first dorsal fin and each pectoral fin has the potential to inject a highly venomous toxin, so extreme care must be taken when undertaking aquarium maintenance, and physical handling of the fish should be avoided. An envenomation can lead to excruciating pain that main result in unconsciousness, and in rare cases, death.

Species Profile

Latin Name: Plotosus lineatus Common Name(s): Coral Catfish Striped Eel Catfish Size: 30 cm (12”) Temperament: Aggressive Reef Compatible: With Extreme Caution Note: Venomous! Temperature: 20 – 27oC (68 – 81oF) pH: 8.1 – 8.6 Salinity: 1.017 – 1.019 Minimum Tank Size: 285 litres (75 gallons) Diet: Omnivore Distribution: Indo-Pacific

So it seems that while you can keep some species of marine catfish, the vast (and safest!) majority of catfish species available to the aquatic hobbyist are indeed from freshwater habitats. But the Ariidae and Plotosidae families contain a vast number of species, many of which aren’t available in the hobby, and many of which are actually from freshwater habitats, but several of which can potentially be kept in a specialized set-up where their unique appearance and characteristics can be enjoyed.

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Tank Talk March 2013 / Volume 40, Number 07 Page