A recent report in the journal Endangered Species Research identifies that data on white marlin abundance is flawed and that as much as 27% of fish identified as white marlin (top fish in photo) are actually roundscale spearfish (bottom fish in photo).
White marlin, highly prized by marine sport fishermen, may be in worse shape than previously thought. White marlin are accidentally caught on commercial longlines set to hook tuna and swordfish. Efforts two years ago by the Center for Biological Diversity to list white marlin on the endangered species list failed but now may be in question.
The white marlin and roundscale spearfish are difficult to distinguish for the average angler. If you don’t have a molecular genetics lab available to you then your best option is to look at the distance from the anal fin to the vent. On the white marlin the distance from the anal fin to the vent is about 2 inches and about 5-6 inches on the roundscale spearfish.
Photo source: Los Angeles Times