Dive Dry with Dr. Bill

#521: The "Barn Door" Halibut

Back in February of 2002 I was cruising over the native seaweeds on the shallow ocean floor in the dive park, back before the exotic Sargassum appeared, when the seaweed exploded in front of me. Now, I'm supposed to be some high falutin' phycologist... you know, a guy who studies seaweed. However, I'd never seen anything like this. The carpet of brown and green algae suddenly lifted off like a magic carpet and began swimming away!

I was shell shocked... and thought I was seeing something I'd never seen before or since. Given its estimated size of 5 to 6 feet, I assumed it was a Pacific halibut (Hippoglossus stenolepis) that had been camouflaged against the bottom. The only time I've seen a Pacific halibut has been on TV when watching commercial fishermen haul in the big ones in the Bering Sea... or on my dinner plate smothered in tartar sauce (which made it difficult to ID properly)!

Until recently I had assumed the fish I saw was indeed this species, and my column this week was to describe it. However, in looking more closely at the images from that dive, I realized that this monster was more likely a HUGE California halibut (Paralichthys californicus)... far larger than any individual I'd seen before or since. Pacific halibut reach lengths of 8-9 ft and weigh up to 700 lbs while their smaller cousin reaches a maximum of five feet and about 70 pounds. Although things do look bigger underwater, the one I saw certainly exceeded this as far as I could tell!

The best way to distinguish a California from a Pacific halibut is by looking at the mouth. The jaw of the California halibut extends beyond the eye and has lots of sharp, conical teeth while that of its larger cousin stops at the front edge of the eye. The individual I observed did not let me get a good look at any teeth inside its mouth as it swam away from me. In addition, the Pacific halibut has a slightly concave ("lunate") tail while that of the California halibut is arched slightly outward and is notched near the tips. Both these diagnostic features can be seen in the still images (unless your eyesight is as bad as mine).

California halibut are "left-eyed" flounder in the family Bothidae while Pacific halibut are "right-eyed" flounder in the family Pleuronectidae. For those of you who skipped my column on flatfish evolution, all halibut, sole, sand dabs and other flatfish are often referred to as flounders. But, Dr. Bill, if these two species have their eyes on different sides of the head, why couldn't you tell immediately that this individual was a left-eyed flounder? Well, because it just isn't that simple! Yes, most Pacific halibut are right-eyed, but some do have both eyes on the left side... and most California halibut are left-eyed but as many as 40% may have the eyes on the right (wrong?) side!

California halibut have several other "common" names including Monterey halibut, chicken halibut, southern halibut and flatty. Small ones may be referred to as "swatters" while the large ones like this individual are called "barn doors." Although generally seen in uniform shades of brown or gray, this one was greenish in color with mottling. They do change color to match their surroundings so this would explain that.

The species is known from the Quillayute River in northern Washington to Magdalena Bay on Baja, with a separate population in the upper Gulf of California (Sea of Cortez). Most of the population is centered from southern California to central Baja. These fish frequent soft bottoms of sand, silt or mud from the surf zone to depths in excess of 900 ft, but are only common above 200 ft. The young are often found in shallower water with the adults at deeper depths. They are often partially or fully covered with sediment as they can bury themselves by undulating their body.

When young these flatties feed primarily on crustaceans including copepods, amphipods, isopods, shrimp and crabs with squid, worms and clam siphons thrown in to vary the diet a bit. As they grow larger they feed more heavily on anchovies, sardines, grunion and other small fish. In turn they are eaten by larger halibut, angel sharks, torpedo rays, soupfin sharks, terns, sea lions and bottlenose dolphin.

Males mature at 2-3 years while the ladies take about 2 years longer. All males are mature by 13 inches and the girls by 23 inches. They may spawn in shallow waters throughout the year although activity is greatest from January to April with a possible second peak from then until as late as early fall. The larvae drift with the plankton for three weeks or more, staying near the bottom during the day and at the surface at night. Once they've settled to the bottom, the young seek out protected areas along the open coast including bays, estuaries and lagoons. The boys live as long as 23 years while the girls may make it to 30 years.

California halibut were a pretty important menu item for Native Americans and even us later immigrants love them. By the late 1800s they were targeted by commercial fishermen off the California coast, although the "glory days" for fishers of this species ended in the 1920s. Beach seiners in San Diego Bay reportedly kept fish as small as 2-6 inches! As early as 1884 David Starr Jordan reported that large "barn doors" were not as plentiful as they had been. Imagine what it must have been like back in the mid 1500s when Europeans first entered our region. Maybe there were a lot more barn doors back then!

© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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The monstrous California halibut ("barn door") in shallow water in the dive park.

This document maintained by Dr. Bill Bushing.
Material and images © 2012 Star Thrower Educational Multimedia