John Graves
Professor of Marine Science
Virginia Institute of Marine Science
College of William and Mary

The hatchet marlin is a pretty interesting story. When the billfishes were last reviewed in 1985 by Nakamura, there were a few problem areas. One was the roundscale spearfish and the other was the hatchet marlin. The roundscale spearfish was described based on one specimen taken off Madeira, and they didn't keep the specimen. Nakamura chose to include the species in his publication — Tetrapturus georgii. While Nakamura did not recognize the hatchet marlin, he pointed out that it might be another species of billfish.

For the Fourth International Billfish Symposium that was held last year on Catalina Island, California, my colleagues and I presented a new study of the billfish based on morphological and molecular characters. We had specimens of all billfish except for roundscale spearfish. What our data showed was that the hatchet marlin was indeed a different species than white marlin, and it grouped with the spearfish. At the symposium another researcher from Florida presented molecular information on the roundscale spearfish indicating that it was a valid species. When I saw his pictures of the fish I thought to myself that it was a hatchet marlin. After the meeting we exchanged samples and sure enough, the hatchet marlin and the roundscale spearfish are the same animal.

It was just lucky to get three more specimens of hatchet marlin at the Mid-Atlantic $500,000 in August 2006. It provided us a chance to look at morphological differences between whites and hatchet marlin. While most of us use the squared off fins to designate a hatchet marlin, it turns out that that character does not always work. Whites can have truncated fins. There are three really good characters to identify a hatchet marlin/roundscale spearfish: (1) the location of the vent - in a white the vent is about two inches forward of the anal fin; in a hatchet marlin/roundscale spearfish it is about six inches in front; (2) the lenght of the branchiostegals (the rays below the gill cavity on the ventral side of the head) - in a white marlin they are relatively short, extending to the pre-opercle (about two- thirds of the way out on the gill cover), while on hatchet marlin/roundscale separfish, they extend almost all the way to the end of the gill cover; and finally (3) the scales - if you look at the side of a white it is fairly smooth in coloration while in a roundscale spearfish it appears almost polka-dotted and if you run your hand forward on a white you'll get stuck by the scales - that doesn't happen on a hatchet marlin/roundscale spearfish.

Cheers,

John