Which Marine Catfish Did you Catch?

Marine Catfish are common not only in Singapore waters, but all tropical to sub-tropical waters in the world. It is easy to identify a catfish with its long whiskers, known as barbels, but often even experienced fishers often struggle to differentiate various marine catfish species from one another.

Marine catfish belong to the order Silurifomes which house all 41 families of catfish; of which only two are found in marine environments: Ariidae and Plotosidae. Identification between the two marine families is relativly simple. Ariidae catfish are also known as the shark-tailed catfish, while Plotosidae are known as eel-tailed catfish.

1: Ariidae catfish, notice the shark-like tail. 2: Plotosidae catfish, notice the eel-like tail.

Why Identification is Challenging

Marine catfish of the same family can often be difficult to identify, even ofr experiacned fishers and researchers. Many species share similar body shapes, colours, fin strauctures and their appreance can change as they grow. To make matters worse, catfis hare not sexually dimorphic meaning that males and females often look the same with no distingishing features. Juveniles and adults of the same species may look vastly different, while different species can look identical at first glance.

In Singapore, identification is further complicated by the lack of up-to-date local guides and the fact that some species have historically been misidentified or grouped together under general names.

What to look for when Identifying a Catfish

You do not need to be a sceientic or an expert on fish to make useful observations. You do not need to memorise names or scientific terms to be able to contribute to research. noticing and recoring a few basic features can provide valuable information. This is what you should look for:

• Overall head shape and size: The shape of the head and its features such as dots, bumps or smooth can often be the distinguishing factor between species. (e.g. torpedo shape, flat and square-ish)

• Number and length of Barbels: These are whisker-like structures around their mouths that help them sense their environment. While catfish often have three pairs, certain species do have fewer. (e.g. three pairs of barbels, on pair short, two pairs half the length of their body).

• Body Shape and length: Marine catfish typically have a flattened body, which aids in their movement through the water. Length often can indicate the age of the fish, helping research to know if they are looking for juvenile or adult characteristics to identify the species. (e.g. 30 cm long fish from nose to tip of the tail, pointed oval body shape)

• Fin and tail shape and size: The fin and tail shape and size often help indicate differeing species. Certain species have uniquely shaped fins like the Gafftopsail catfish which makes them easy to identify. (e.g. very tall first spine on dorsal fin, rounded tail lobes)

• Coloration: Their skin can vary in colour, often featuring shades of gray, brown, or yellow, which helps them blend into their surroundings and helps researches identify the species. (e.g. blue-ish tinted body, silvery fins with red fringe tail.)

Do not worry if you are unsure, even simple descriptions can help narrow down possible species or groups. You can log the details of your catfish catch here or in the report catch link.

Photos Matter more than Names

Clear photogrpahs are often more useful than exact names. A good photo allows researchers to examine features that may not be obvious in the field.

Helpful photos include:

• A side view of the whole fish

• A close-up of the head

• The fins, especially if spines are visible

• The tag, if one is present

We understand that getting multiple high-quality photos while fishing is not always practical. Stopping to thoroughly photograph every catch can be disruptive, and we do not expect this for every fish.

If possible, a single clear photo is more than sufficient—ideally a side view of the fish with a ruler or another object for scale. This one image alone can provide valuable information for identification and size estimation.

Do not worry if the photo is not perfect. Partial or slightly blurry images can still be useful and are far better than no photo at all. Feel free to share a photo(s) by emailing marinecatfishresearch@gmail.com.

What if I am unsure?

Not knowing the exact speceis is completely normal. Many researchers often find themsleves looking at a fish and thinking "what is this???". Often time in research, records are only identifiable to a general group or genus level, but this information is still very valuable.

Avoid guessing or focring a match to a speceis name. Submitting an observation as "unknown marine catfish" is still perfectly acceptable and helps maintain data quality. And do not worry, you best description will still be be immensely helpful.

How to Submit a Record

Records can be submitted through the report catch form on this website. Both tagged and untagged marine catfish are welcome and encouraged. Simply follow the prompts in the form to record basic information about your catch.

Each submission adds to a growing dataset that helps improve understanding of marine catfish diversity, distribution, and habitat use in Singapore’s coastal waters. Whether it’s a single photo, a tag number, or a brief location note, your contribution makes a meaningful difference.

Thank you for supporting local marine research.