Anglers may have been surprised to hear of a new state record fish recently landed, although the size of the fish wasn’t necessarily what surprised them. While almost everyone knows of the Common Dolphinfish (AKA mahi-mahi or dorado), many anglers might not have been aware of the Pompano Dolphinfish’s existence.
The two species of dolphinfish can be difficult to distinguish to the untrained eye, as Pompano Dolphinfish look very similar to young or female Common Dolphinfish. However, with a little bit of training, Pompano Dolphinfish identification isn’t as difficult as it might seem.
The first thing you’ll notice about Pompano Dolphinfish is the depth of the body. Pompano Dolphinfish are, generally, much deeper bodied than a Common Dolphinfish. According to the FAO Species Identification Guide, the body depth of the Pompano Dolphinfish is more than 25% of its standard length, whereas for Common Dolphinfish, the body depth is less than 25% of its standard length. The standard length is the length from the tip of the snout to the last vertebra. The caudal (tail) fin is not included.
Secondly, the anal fin shape of the Pompano Dolphinfish is different than that of a Common Dolphinfish. In Common Dolphinfish, the anal fin is concave, with a strong sickle-like curve to the anterior (front) of the fin. In Pompano Dolphinfish, the anal fin is not concave and does not have that same sickle-fin shape. With that being said, this characteristic can be somewhat deceiving when the anal fin is not fully extended.
Lastly, and perhaps most importantly, is the shape of the tooth patch on the tongue. Pompano Dolphinfish have a broad, squarish tooth patch, whereas Common Dolphinfish have a smaller, more oval-shaped tooth patch. This feature is one of the easiest distinguishing characteristics to use while on the water to confirm a Pompano Dolphinfish identification.
There are a few other characteristics that can be used to tell the two species of dolphinfish apart, such as the number of dorsal fin rays (fewer in Pompano Dolphinfish) or the number of caudal vertebrae (more in Pompano Dolphinfish), but these are not able to be used in the field without considerable difficulty. Thankfully, counting fin rays or caudal vertebrae isn’t necessary; the body depth, anal fin shape, and tooth patch shape should be enough to positively ID any Pompano Dolphinfish you may come across while out fishing.
To learn more about Pompano Dolphinfish, please see this excellent webpage on the Florida Museum website.
