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Is that lionfish a Pterois Miles or Pterois Volitans?

July 25, 2016 3 Comments

Pterois Volitans or Pterois Miles?

Many divers and lionfish hunters are not aware that there are actually two different species of lionfish in the invaded range of the Western Atlantic, the Pterois Volitans (Red Lionfish) and the Pterois Miles (Devil Firefish). (Click here to learn more about why lionfish are a problem.) There are over 350 different species of lionfish which are in the family Scorpaenidae (Scorpionfish), but only the Miles and Volitans make up the invasive population that are currently plaguing our Atlantic waters. Researchers are working to narrow down the percentage of each type of lionfish in different locales as well as working to determine if there is a difference in habitat, diet, or behavior. We have heard the ball park number of 93% of the lionfish in the invaded range are of the species Pterois Volitans and the Pterois Miles makes up the smaller remaining percentage.

The two species are nearly identical in appearance, with only a subtle difference in the number of dorsal fin rays and anal fin rays. Amazingly, there is a much broader difference of appearance among the same species than between the two. We have seen lionfish that are a bright crimson red and others that are almost black in color. We also see a surprising number of ‘mutants’ with partial or completely missing dorsal spines. To be clear, only a DNA test is 100% effective in determining which of the two species of lionfish you are looking at, because the method of determination of species which I’m about to explain has proven wrong in a very few cases due to variability of the ray count among the two species. However, that rate of error is small (about 5%) and for the most part the below method will work in determining which of the two species you are looking at.

Pterois Volitans

The Pterois Volitans species of lionfish is distinguished by the 11 Dorsal Fin Rays and by the 7 Anal Fin Rays, as shown in the image below. Click image for larger view.

Pterois Volitans fin ray count

photo courtesy of Paul Bartels


Pterois Miles

The Pterois Miles is identifiable by its 10 Dorsal Fin Rays and its 6 Anal fin rays as shown in the image below. Click image for larger view.

Pterois Miles fin ray count
The next time you are looking at a lionfish take a closer look at those ray fins and see if you can determine the type of lionfish that you are removing in your area. With more people paying attention to which of the two types of lionfish they are removing we will have a better chance of figuring out if there are habitat, temperature constraints, diet differences or any other delineation between the two species. The important thing to remember is that they are both delicious and with enough human effort out there hunting the lionfish we will be able to keep the population in check until nature finds a way to restore balance in our ecosystem.

The following image shows the study from which the data for the identification method was gained. 

About the Author:

Andy is a former US Navy Diver and Submariner, 20 year PADI Dive Instructor, USCG 100 ton Captain, Inventor & entrepreneur, manufacturer, Yachtbroker, skilled mechanic & electrician, and an avid hunter of lionfish.

Comments (3)

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  1. Eric ROLLAND says:

    Since 2012, considering this subtle difference in the number of dorsal fin rays and anal fin rays, I never find a pterois Miles in Guadeloupe.

  2. Barbara says:

    Hello Andy,
    I would be curious to know where you got your information, since you don’t sight your reference material.
    According to the ray fin counts for the two species are not as clear-cut as you state in your article.
    According to their description the volitans have been found with dorsal soft ray fins numbering from 9-12 and anal soft ray fins numbering from 6-8.
    The miles dorsal ray fins have been found to number from 9-11 and anal soft ray fins from 6-7.
    So the only positive ID one could make would be a fish with 12 dorsal soft ray fins or 8 anal soft ray fins. They could be identified as volitans.

    Barb Crites

    • Andy Lowe says:

      Hi Barbara, the image below is from an older study by Schultz (1987) showing the deviation of fin ray count between the two species. You are right, it is not full proof or guaranteed, but it is greater than 90% accurate. fin counts

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