DIVE DRY WITH DR. BILL #873: THE TWO-TONED BUTTERFLYFISH
A friend of mine (Rob) on Facebook posted an interesting video of a scythe butterflyfish (Prognathodes falcifer) taken out on the west end of Catalina. Now I've filmed them in several locations around the island over the last few decades and they've been here since before I started filming... at least if you don't count my very early attempts in 1969 and 1970 which were rather disastrous.
As I watched Rob's video, I noted something I had never seen before. The right side of the fish had one color pattern, an unusual one I'd never seen. Then when it did a 180° in the video, I noted the left side had the more normal coloration I've seen in every scythe butterflyfish I've ever filmed. The right side was largely black in color beneath the scythe rather than yellow and white as in normally colored butterflyfish.
I sent the still images up to the fishiest guy I know, Dr. Milton Love, at UCSB. Milton and I worked together on early Jean-Michel Cousteau Project Ocean Search programs on Catalina in the 1970s. We have also coauthored a few papers on new fish species seen in California. His weighty tome, Certainly More Than You Wanted to Know About the Fishes of the Pacific Coast is my "go to" bible on the species in our waters... written with Milton's unique sense of humor. Milton had never seen anything like this in the species. He sent the images off to some of his fishy friends who study tropical and subtropical species.
Yes, the scythe butterflyfish is normally found in waters to the south. The geographic range is Santa Cruz Island to the tip of Baja California and islands off Mexico and other central American countries. However, that does not necessarily mean it can only live in warm water. Milton Love states they may be found at depths up to nearly 900 fsw. Since they tolerate the low temperatures at such depths, once they arrive in our waters they easily adapt to the temperatures in our shallows. I generally see them at 30 to 60 fsw.
Rob mentioned that he observed a growth on the "dark side" of the fish near the mouth. He described it as "small light-colored raised dots." Perhaps the discoloration is due to a disease rather than being a genetic anomaly. I would think if it was a mutation that we'd be seeing it in the next generation. I've filmed juvenile scythe butterflyfish at other dive sites. Assuming these are the offspring of the local population rather than ones that arrived as larvae from down south, we might see such a pattern in them.
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Odd coloration (left) and normal coloration (right); juvenile scythe butterflyfish and adult.
A friend of mine (Rob) on Facebook posted an interesting video of a scythe butterflyfish (Prognathodes falcifer) taken out on the west end of Catalina. Now I've filmed them in several locations around the island over the last few decades and they've been here since before I started filming... at least if you don't count my very early attempts in 1969 and 1970 which were rather disastrous.
As I watched Rob's video, I noted something I had never seen before. The right side of the fish had one color pattern, an unusual one I'd never seen. Then when it did a 180° in the video, I noted the left side had the more normal coloration I've seen in every scythe butterflyfish I've ever filmed. The right side was largely black in color beneath the scythe rather than yellow and white as in normally colored butterflyfish.
I sent the still images up to the fishiest guy I know, Dr. Milton Love, at UCSB. Milton and I worked together on early Jean-Michel Cousteau Project Ocean Search programs on Catalina in the 1970s. We have also coauthored a few papers on new fish species seen in California. His weighty tome, Certainly More Than You Wanted to Know About the Fishes of the Pacific Coast is my "go to" bible on the species in our waters... written with Milton's unique sense of humor. Milton had never seen anything like this in the species. He sent the images off to some of his fishy friends who study tropical and subtropical species.
Yes, the scythe butterflyfish is normally found in waters to the south. The geographic range is Santa Cruz Island to the tip of Baja California and islands off Mexico and other central American countries. However, that does not necessarily mean it can only live in warm water. Milton Love states they may be found at depths up to nearly 900 fsw. Since they tolerate the low temperatures at such depths, once they arrive in our waters they easily adapt to the temperatures in our shallows. I generally see them at 30 to 60 fsw.
Rob mentioned that he observed a growth on the "dark side" of the fish near the mouth. He described it as "small light-colored raised dots." Perhaps the discoloration is due to a disease rather than being a genetic anomaly. I would think if it was a mutation that we'd be seeing it in the next generation. I've filmed juvenile scythe butterflyfish at other dive sites. Assuming these are the offspring of the local population rather than ones that arrived as larvae from down south, we might see such a pattern in them.
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Odd coloration (left) and normal coloration (right); juvenile scythe butterflyfish and adult.
