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Dive Dry with Dr. Bill

#631: Hey, Chubby!

Although it's well after the holidays, many of us are still facing the dilemma of how to lose all that excess "bioprene" we put on drinking eggnog and eating Christmas cookies. Okay, so that wasn't the full extent of my "diet" in December but I blame them for the most part. Of course this column will not be about how difficult is in trying to slip into my shrinking wetsuit. I'm going to talk about a group of fish in our waters known as the sea chubs.

The three chubs I'll write about today are the Catalina blue perch, the button-back perch and the zebra perch. Funny how common names are misleading since none of these fish are perch. They all belong to the sea chub family Kyphosidae. The common names I prefer are the halfmoon (Medialuna californiensis), the opaleye (Girella nigricans) and the zebra perch (Hermosillo azurea). Okay, so the last one is still referred to as a "perch," but now my readers know better than that!

The sea chubs are found in habitats near shore from the temperate to the tropical zone. I have filmed them here (obviously) as well as in warmer waters (to which I will soon head). There are some 45 species found in the Pacific, Atlantic and Indian Oceans. Only five of them frequent our waters.

Perhaps the most common is the opaleye which may exceed two feet in length but is usually smaller. The most obvious feature other than their green to gray-green color and blue eyes is the one to three light colored spots beneath their dorsal fins. They are known from Oregon to Cabo San Lucas but are most common from central California south. Like other chubs they spawn in open water and the fertilized eggs and larvae drift with the plankton. Young opaleye may also disperse by following drifting kelp rafts

The halfmoon is named for its tail which resembles a half moon (well, without all the craters and "seas"). Their bodies are blue to gray-blue in color with hints of vertical bands, but can actually change to a darker color when frightened. There is a dark spot at the upper rear of the gill cover or operculum. They reach about 19" in length. The halfmoon is known from Vancouver Island to the southwestern Gulf of California. These sea chubs are more mobile than the opaleye and may be found out in open water away from shore.

The zebra perch is similar in size to the halfmoon. The species name azurea means sky blue in Latin but the body color is green, silvery or brown with many dark bands along the side. The blue must refer to the blotch located on their gill cover. Their range extends from the Klamath River in Oregon to the Gulf of California, but they are most common from southern California south. In the fall I frequently see small juveniles (3-4") feeding on the algae that grows on the lower dive park stairs.

These three sea chubs all favor a largely vegetarian diet of seaweed. I frequently see the opaleye and halfmoon chomping down on the blade of giant kelp. They will also take other algae including reds and greens. However, they are not strictly vegan or even vegetarian. They will take invertebrates including amphipods, isopods, small snails and worms. It is said that in our cooler waters they need the extra protein compared to their brethren further south. Juveniles occasionally clean parasites off other fish and I have filmed mature halfmoon cleaning ocean sunfish (Mola mola) out at offshore Farnsworth Bank (no relation to U.S. Bank or Wells Fargo).

I've always thought of the opaleye as a "trash" fish, not worthy of gracing a dinner plate. After all, they've even been seen munching on cigarette butts (a nicotine craving?) and I often see them with long strands of fibrous (algae-based) poop dragging behind. Disgusting! . I was surprised to find in Dr. Milton Love's incredible fish guide that they were targeted commercially back in the 1800s along with halfmoon. Neither fish is considered a worthy catch by anglers today... perhaps in part because their small mouths make them difficult to take on rod-and-reel. Besides, it is hard to bait a hook with kelp (although green peas will do the trick).

© 2015 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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Opaleye and halfmoon; zebra perch and disgusting opaleye trailing its poop behind

This document maintained by Dr. Bill Bushing.
Material and images © 2014 Star Thrower Educational Multimedia