DIVE DRY WITH DR. BILL #836: HORNYHEADS
No, no, no... this column has little to do with critters hopped up on sex hormones. Sorry to disappoint so many of my readers. I will touch on it a bit towards the end though. A diver friend, Nick Ewbank, described a fish he had seen in the dive park recently, and based on his description I told him I was pretty sure I could tell him what it was.
Back when I first saw the fish, I thought it was an English sole so that's how I labelled it. However, a gander through Dr. Milton Love's incredible guide to West Coast fishes, made me decide my initial guess was wrong. It looked more liked a hornyhead... hornyhead turbot (Pleuronichthys verticalis) that is! I e-mailed a few of my pictures to Milton and he confirmed my new ID. In Mexico it is known as the platija cornuda.
This fish was first described back in 1880 by David Starr Jordan, first president of Stanford, and Charles Henry Gilbert. These two were pioneering ichthyologists (fish biologists) and were commissioned by the U.S. Fish Commission to undertake a study of fishes along our coast back in 1879-80.
This is a flatfish similar to sanddabs and halibut. They all look like a big heavy dude stepped on them while walking along the bottom. By that I mean they are flattened from top to bottom (or dorsal to ventral surface if you prefer). They are yellowish to dark brown with small, cream colored spots and larger dark blotches. The eyes are fairly large and located on the "right" side of the body. There is a ridge between the eyes with a sharp spine pointed toward the rear. They often swim with their long pectoral fin extended up. Hornyheads reach a maximum length of about 15 inches.
It isn't often I encounter this species, and I don't remember ever finding one in the dive park. They prefer West Coast waters from Point Reyes, California, to Magdalena Bay in Baja California, Mexico. They prefer soft bottom habitats of sand or mud which probably explains why I hardly see them I'm a kelp forest ecologist and tend to stick close to rocky reefs. Their depth range may descend to over 650 feet, far beyond my maximum dive depth.
Like many flatfish, hornyheads often lie in wait, well camouflaged and partially buried in the substrate. When a tasty amphipod, polychaete worm, or small fish ventures too close, they ambush them. Another preferred munchable is nipping at exposed clam siphons, and they will also consume tube dwelling anemones. Based on stomach content analysis, they appear to feed largely at night. Although they are taken in deep water trawls, hook and line anglers are rarely successful in catching them due to their small mouths. As bottom feeders, they are occasionally studied to determine the concentration of heavy metals, DDT and other pollutants.
Okay, so here is the sex part. Hornyheads must be driven by hormones since unlike many fish species, they are believed to spawn year-round. I'm lucky if I do it once a decade! Females are sexually mature at 6 inches. The eggs and sperm are cast into the water. If fertilization occurs (odds are a bit better than winning the lottery), they hatch into larvae that dwell in the plankton until they settle out. Sadly there is relatively little known about the details of its life history.
© 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Hornyhead turbot swimming and resting on the bottom at Yellowtail Point, Catalina Island.
No, no, no... this column has little to do with critters hopped up on sex hormones. Sorry to disappoint so many of my readers. I will touch on it a bit towards the end though. A diver friend, Nick Ewbank, described a fish he had seen in the dive park recently, and based on his description I told him I was pretty sure I could tell him what it was.
Back when I first saw the fish, I thought it was an English sole so that's how I labelled it. However, a gander through Dr. Milton Love's incredible guide to West Coast fishes, made me decide my initial guess was wrong. It looked more liked a hornyhead... hornyhead turbot (Pleuronichthys verticalis) that is! I e-mailed a few of my pictures to Milton and he confirmed my new ID. In Mexico it is known as the platija cornuda.
This fish was first described back in 1880 by David Starr Jordan, first president of Stanford, and Charles Henry Gilbert. These two were pioneering ichthyologists (fish biologists) and were commissioned by the U.S. Fish Commission to undertake a study of fishes along our coast back in 1879-80.
This is a flatfish similar to sanddabs and halibut. They all look like a big heavy dude stepped on them while walking along the bottom. By that I mean they are flattened from top to bottom (or dorsal to ventral surface if you prefer). They are yellowish to dark brown with small, cream colored spots and larger dark blotches. The eyes are fairly large and located on the "right" side of the body. There is a ridge between the eyes with a sharp spine pointed toward the rear. They often swim with their long pectoral fin extended up. Hornyheads reach a maximum length of about 15 inches.
It isn't often I encounter this species, and I don't remember ever finding one in the dive park. They prefer West Coast waters from Point Reyes, California, to Magdalena Bay in Baja California, Mexico. They prefer soft bottom habitats of sand or mud which probably explains why I hardly see them I'm a kelp forest ecologist and tend to stick close to rocky reefs. Their depth range may descend to over 650 feet, far beyond my maximum dive depth.
Like many flatfish, hornyheads often lie in wait, well camouflaged and partially buried in the substrate. When a tasty amphipod, polychaete worm, or small fish ventures too close, they ambush them. Another preferred munchable is nipping at exposed clam siphons, and they will also consume tube dwelling anemones. Based on stomach content analysis, they appear to feed largely at night. Although they are taken in deep water trawls, hook and line anglers are rarely successful in catching them due to their small mouths. As bottom feeders, they are occasionally studied to determine the concentration of heavy metals, DDT and other pollutants.
Okay, so here is the sex part. Hornyheads must be driven by hormones since unlike many fish species, they are believed to spawn year-round. I'm lucky if I do it once a decade! Females are sexually mature at 6 inches. The eggs and sperm are cast into the water. If fertilization occurs (odds are a bit better than winning the lottery), they hatch into larvae that dwell in the plankton until they settle out. Sadly there is relatively little known about the details of its life history.
© 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Hornyhead turbot swimming and resting on the bottom at Yellowtail Point, Catalina Island.
