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/A Diversity of Aquatic Life

The Chubs Called Rudderfishes, Subfamily Kyphosinae

By Bob Fenner

Kyphosus sectatrix

If I had a hand in re-naming the part of the sea chub family Kyphosidae ("key-fos-id-ee") called Rudderfishes (for their habit of following ships at sea) I'd volunteer the appellation "swimming footballs"; for their oval-shape, vigor, and fondness for feeding. Though they have small mouths equipped with equally small teeth, the subfamily Kyphosinae are eager eaters.

Hardiness is this group of fishes singular strongpoint; like some of the cichlids and livebearers, there are naturally occurring "golden" morphs, notwithstanding most are silvery with darker highlights. Another strike against Rudderfishes is their size; most attain more than a foot. All species are best displayed in a small school, and this obviously requires a system of large proportions.

Nevertheless, these fishes can be easily captured, ship and live well in captivity; and in the age of so many public aquariums and private folks with humungous tanks, Rudderfishes do have their place.

Classification: Taxonomy, Relation With Other Groups

Modern schemes include three or more subfamilies (ending in -inae) within the principal sea chub family Kyphosidae:

The subfamily Girellinae are called nibblers for their habit of grazing. The cool water California opaleye, Girella nigricans, Baja's endemic gulf opaleye, G. simplicidens and the prettier Zebrafish G. zebra from the southern half of Australia occasionally make their way into hobby markets.

The Scorpidinae, termed Halfmoons for the semi-lunate shape of their tail fins. Indo-Pacific to cool water California; rarely seen in the hobby.

The Kyphosinae subfamily is the Rudderfishes proper; they are also called chubs or sea chubs (of course), and pilot fishes. Rudderfish species bodies are high in profile, and compressed side to side, bearing large, forked tails. They have small heads with equally small terminal mouths. If you look carefully, you will observe that their dorsal and anal fins are somewhat overlapped by a sheath of scales. Four genera, Hermosilla, Kyphosus, Neoscorpis and Sectator with eleven species.

None of the subfamilies members are stock items in the trade. A few are exhibited regularly in public displays and a handful are offered from time to time. In the genus Kyphosus, K. elegans, the Cortez chub of Mexico's Baja and the sympatric Atlantic/Bermuda chub K. sectatrix, are available from time to time, as is K. cinerascens; mainly out of Hawaii. The first and third of these occur in golden/xanthic forms and sometimes "Koi" mixed color (silver, white, black, golden-yellow) naturally occurring varieties.

Kyphosus bigibbus Lacepede 1801, the Gray Sea Chub. Indo-Pacific;  to the Hawaiian Islands. To 60 cm. overall length. Hawai'i image. Has shorter dorsal fin than K. cinerascens. Occurs in all yellow, white and koi varieties. This one in Hawaii.

Kyphosus cinerascens (Forsskal 1775), the Blue Sea Chub. Indo-Pacific; Red Sea to the Hawaiian Islands. To 50 cm. overall length. Hawai'i images. 

Kyphosus elegans (Peters 1869), the Cortez Sea Chub. Eastern Pacific; Sea of Cortez to the Galapagos. To 38 cm. Feed principally on attached, benthic algae. Socorro Island pix of normal, xanthic individuals at right, group in the Galapagos below. 

Kyphosus secatrix (Linnaeus 1766), the Bermuda Sea Chub. West and eastern Atlantic coasts, mid-latitudes to tropics. To 76 cm. Feeds on algae, mollusks, small crustaceans Belize image. 

Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

Kyphosus vaigensis (Quoy & Gaimard 1825), the Brassy Chub. Indo-Pacific; Red Sea to the Hawaiian Islands. To 76 cm. Red Sea image

Also hailing from Mexico's Pacific side are the zebra perch, Hermosilla azurea and rainbow chub, Sectator ocyurus; both quite pretty, but not often collected.

Microcanthus strigosus (Cuvier 1831), the Stripey. Sporadically distributed in western and eastern Australian waters, Japan, Taiwan, Hawai'i. To six inches in length. Often placed in its own family Microcanthidae. One in the wild and another in captivity.

Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

Sectator ocyurus (Jordan & Gilbert 1881), the Rainbow Chub. Baja California to the Galapagos. To 60 cm. Here lining up to be cleaned by a Hogfish in Costa Rica (Pacific side) 2011

Natural Range

The larger family is found worldwide in tropical and temperate shallow seas around land masses. The subfamily of Rudderfishes are about as widely spread out; in warmer waters of the Indian, Atlantic and Pacific Oceans.

Selection: General to Specific

On the rare occasion Rudderfishes are offered in the trade, they are almost invariably in good health. Despite their active natures, much the same as shipping the minnows called "barbs" and "sharks", these fishes calm down to zero when bagged and boxed. There are just two criteria in which I judge their purchase:

Apparent Physical Health: 

Kyphosids are captured by one of three techniques; passive fish traps, hand and fence netting, and "hook and line". The latter in particular tends to tear the mouth and traumatize the specimens. Look for mouth sores, missing rows of scales (especially around the dorsal and anal fins), and evidence of secondary infection (reddening). Chubs in good shape are active, curious animals, in constant motion during the day.

Feeding Behavior: 

Worthy specimens accept all kinds of foods readily; in the wild they are on the constant prowl for edibles, nibbling on rocky offerings and searching the suspended plankton. A Rudderfish that refuses food should be passed by.

A note regarding catching and moving chubs; take care when doing so. These fishes are powerful swimmers, with stout anterior dorsal and three anal spines that get hung on nets and puncture unwary hands. Better to use your nets to herd them one at a time into an awaiting heavy duty plastic bag.

Environmental: Conditions


In three words; rocky, large and surgy. Kyphosids are found in close association with rocky reefs and shoals where they hole up to sleep on the bottom at night... and avoid predators by day. Their tanks should be large and with lots of water motion in recognition of these fishes size, swimming needs, oxygen use and circulation to remove wastes.


Not too surprising, Rudderfishes display broad tolerance to a wide range of chemical and physical conditions. They can often be observed in tide pools as juveniles, and near river outfalls as adults; typifying resistance to highly variable surroundings.

They are eurythermal, easily living in water in the 50-80's F.; euryhaline, tolerating near fresh to straight marine salinities; and vie with the damsels as the most metabolite resistant of fishes.


Should be oversized and vigorous. Remember, kyphosines are large, fast moving, big-eating fishes. Your circulation ought to aid their picking and swimming efforts in collecting particulate matter, leaving no "dead spots" in the system. Four or more turn-overs in circulation and filtration volume per hour is called for.


My ideal set-up for showing off these fishes would involve a biotopic rocky surge zone, a small school of a rudderfish species, the Sergeant Majors (genus Abudefduf) that occur in their range and which they share habitat, a large 'show' specimen angelfish and some surgeonfish/tangs of the same stipulation.

Behavior: Territoriality

Some of the other members of the whole family, especially the Opaleyes (subfamily Girellinae) can be outright aggressive, bullying all other livestock in your system. By contrast, the Rudderfishes of the subfamily Kyphosinae are outright aloof, leaving all but edible shrimp and algae alone.


The chief concern in introducing the Rudderfishes is not mode or technique of acclimation, as they respond very well to being moved into new situations, but concern for social hierarchies as they must/will readjust from their addition. As stated elsewhere, these fishes are best shown in a species school setting, with as many individuals as your system will accommodate, but a minimum of three. All should be placed at the same time, and observed for a day or two to make sure they are not being bullied by the alpha fishes in the tank.

Predator-Prey Relations:

Besides being "fleet of fin" and quite spiny, Rudderfishes are notably poor eating (game-fishers throw them back). Predatory fishes tend to not eat them either.

Feeding/Foods/Nutrition Feeding/Foods/Nutrition:

Chubs are omnivorous fishes with long digestive tracts that take copious quantities of benthic algae, plankton and small invertebrates in the wild. In captivity they are eager feeders on all foodstuffs.

Some greenery should be intentionally included in their regular feedings and if possible, be available as live material or attached feed throughout the day. More frequent, smaller offerings are best for these fishes, as foraging all day is their usual habit.

Disease: Infectious, Parasitic, Nutritional, Genetic, Social

As far as external complaints, these fishes are amongst the most parasite and trouble free. In a dire pollution, mechanical/controller failure, or other "wipe-out" scenario, Kyphosids are the last to die.

As "toughies" I don't specifically encourage routine treatment, dips or even quarantine with these fishes. The damage from handling and social upset is of greater consequence than the accrued benefits of such prophylaxis.


So now you know about the subfamily of Rudderfishes, Kyphosinae (and a bunch re their larger family heading, Kyphosidae). While not spectacular physically or color-wise, nor "character" specimens like angels or triggers, the chubs called Rudderfishes do have their place; principally as "other" and dither fish for large marine and biotopic set-ups.

Provide them with a large enough system (hundreds of gallons), frequent and plentiful food including greens, and vigorous filtration and circulation, and you'll be rewarded with endless interesting behavioral observation.

Bibliography/Further Reading:

Burgess, Warren E., Herbert R. Axelrod & Raymond E. Hunziker. 1990. Atlas of Aquarium Fishes, v.1, Marine Fishes. T.F.H. Publications, NJ.

Fowler, Henry W. 1967 authorized reprint. The Fishes of Oceania. Verlag Von J. Cramer, Germany.

Johnson, G.D. 1984. Percoidei: development and relationships. In H.G. Moser et al. (Eds.), Ontogeny and systematics of fishes. Spec.Publ.No.1, Amer. Soc. Ichthyol. and Herp.:464-498.

Nelson, Joseph S. 1994. Fishes of the World, 3d ed. John Wiley & Sons, Inc. NY.

Randall, John E. 1968. Caribbean Reef Fishes. T.F.H. Publications, NJ.

Stratton, Richard F. Girella my dreams. TFH 3/92.

Thomson, Donald A., Lloyd T. Findley & Alex N. Kerstitch. 1979. Reef Fishes of the Sea of Cortez. Wiley-Interscience, NY. 

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