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/A Diversity of Aquatic Life

Do You Know Jacks? You Will. The Family Carangidae

By Bob Fenner

Gnathodon speciosus, three footers

Jacks are often mistaken for Tuna fishes… with their robust, compressed to torpedo-shaped (fusiform for you fancy types) bodies, thin caudal peduncles, large eyes… other adaptations for continuous, at-times rapid swimming in open water. What does this family have to do with pet-fishing? Good question… as more and more we've seen a couple of species of carangids regularly offered in the hobby. Jacks, though often beautiful, interesting behaviorally, get way too big, fast, for home hobbyists. Hence my cautionary article on them here.

Classification: Taxonomy, Relation With Other Groups

Jacks and Pompanos are typically "shiny" in appearance, most with just tiny cycloid (non-interdigitating) scales, often with separate finlets behind their one or two dorsal fins… often with bony scutes along lateral line… large eyes, deeply forked tail fins… being good fighters on a fishing line, and tasting (many of them) great. This is a good-sized family of some 33 genera and about 147 species… many are important food and game fishes.

Range:

Carangids are all marine fishes with some species venturing into brackish waters. The Family ranges widely in the tropical to temperate Atlantic, Indian and Pacific Oceans. They are mainly found in shallow water, above reefs and in the open ocean.

Size:

Some species only grow to eighteen inches (50 cm.) in length, others to more than six feet (two meters). They are remarkably fast growers.

Key Species:

Though the trade mainly sees just the following two, periodically other species of carangids are offered. Their lack of mention here should not encourage you in trying them. None have proven to be easy to keep unless received in good condition and met more than halfway in their requirements (see below).

Gnathodon speciosus (Forsskal 1775), the Golden Trevally, what a beautiful fish! As a juvenile to adulthood this bold, golden splendor is a sight to behold… all shiny gold to silver bodied and finned, with an assortment of vertical black barring. My first memory of this fish is as a boy, snorkeling off of Southern Japan. A tiny yellow, almost-just-a-dot fish "leading" just before my mask… like a miniature pilot! (THE Pilotfish, Naucrates ductor is part of this family btw). Small juveniles do associate with jellyfish, sharks and divers, likely for protection. 

Two inch juveniles A five inch specimen in captivity Two foot plus ones in a Public Aquarium

This fish has become a darling of the Public Aquarium business… with their gorgeous coloring and active schooling behavior (I swear they're working for Kodak!); the species was bound to be a winner there. Unfortunately, this is a very active, eager-eating/metabolizing species that can/does grow to more than three feet (110 cm.)! NOT stunted by being kept in small (less than several hundred gallon plus) systems.

Selene brevoortii (Gill 1863), is the Mexican Lookdown. This and THE Lookdown, Selene vomer make their way into the trade (the latter through tropical West Atlantic collectors). This unusual looking (slightly tilted downward, looking at the bottom) fish does have two things going for it that most Jacks don't… It doesn't get that big (38 cm., about 15 inches long maximum… aquarium specimens smaller), and it's not that active (eating, eliminating, breathing, swimming) a species. 

 Selene vomer (Linnaeus 1758), the Lookdown. Western Atlantic. To about 18 inches overall. http://fishbase.org/Summary/speciesSummary.php?ID=1004&genusname=Selene&speciesname=vomer

Other Non-Hobbyist Species of Jacks...

Genus Alectis:

Alectis ciliaris (Bloch 1787), the African Pompano. Worldwide in tropical seas. To 130 cm. Here in the Lembah Strait. http://fishbase.org/Summary/speciesSummary.php?ID=988&genusname=Alectis&speciesname=ciliaris

Alectis speciosus (Bloch 1787), the Threadfin Pompano. Worldwide in tropical seas. To 150 cm. Like many Jacks, can be kept as juveniles but fare poorly as adults in captivity. Aquarium photo of a 10 cm. specimen at Atlantis Aquarium in Long Island, NY. 


Genus Carangoides:
Carangoides bajad (Forsskal 1775), the Orangespotted Trevally. Indo-West Pacific; Red Sea to the Philippines. To twenty two inches in length. Two color varieties in the Gulf of Aqaba, Red Sea.

Carangoides caballus Gunther 1869, the Green or Horse Jack. Indo-West Pacific; Red Sea to New Caledonia. To 120 cm. in length. This one off Hurghada in the Red Sea.

Carangoides fulvoguttatus (Forsskal 1775), the Yellowspotted Trevally. Indo-West Pacific; Red Sea to New Caledonia. To 120 cm. in length. This one off Hurghada in the Red Sea.

Carangoides orthogrammus (Jordan & Gilbert 1882), the Island Trevally. Western Indian Ocean to Mexico. To twenty eight inches in length. A young one off of N. Sulawesi and a larger one off of Maui in the Hawaiian Islands.


Genus Caranx:
Caranx ignobilis (Forsskal 1775), the Giant Trevally. Indo-West Pacific; East Africa to Hawai'i, Marquesas. To more than five feet in length, 53 kg. This one of a group hanging around our dive boat in Queensland, Australia, and a school off Richelieu Rocks in the Andaman Sea off Thailand. 


Caranx latus Agassiz 1831, the Horse-eye Jack.  Western and Eastern Atlantic. To a meter in length. This one in the Bahamas.

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

Caranx lugubris Poey 1860, the Black Jack.  Circumtropical. To a meter in length. One in the Bahamas, another off the Galapagos.

Caranx melampygus Cuvier 1833, the Bluefin Trevally. Tropical Indo-Pacific; Red Sea, East Africa all the way over to the eastern Pacific. Recorded to 117 cm., more than 43 kg. This group off of Egypts Red Sea.

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

 

Caranx ruber (Bloch 1793), the Bar Jack. Central Western Atlantic. To twenty one inches. This one off the Bahamas.. Western Atlantic; North Carolina to Venezuela. To thirty inches wide. W/ a Urobatis jamaicensis (Cuvier 1816), the Yellow Stingray in Cozumel 2011 below.  

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

Verticals (Full/Cover Page Sizes Available
Caranx sexfasciatus. Here off Ras Muhamed, Egypt's Sinai.


Genus Scomberoiodes:

Scomberoides lysan (Forsskal 1775) the Doublespotted Queenfish. Indo-Pacific; Red Sea and east Africa to Hawai'i. To three and a half feet total length. A minor game fish... perhaps a candidate for large public aquariums? Image made in Kona, HI.


Seriola rivoliana Valenciennes 1833, the Almaco Jack. Circumtropical. Maximum recorded length 160 cm. A juvenile in N. Sulawesi, and a mid-size adult in the Galapagos. 


Selaroides leptolepis  (G. Cuvier 1833), Yellow-Stripe Scad. Bali 2014
Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.


Genus Trachinotus:

Trachinotus falcatus (Linnaeus 1758), the Permit. Central Western Pacific. To 114 cm. in length. This one in the Florida Aquarium, Miami. 

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

Trachinotus rhodopus Gill 1863, the Gafftopsail Pompano. S. Cal. to Peru. To 40 cm. in length. Costa Rica (Pacific side) 2011

Selection: General to Specific

Size is a strong criterion for keeping aquarium specimens physiologically AND psychologically fit/happy. Besides, for starting, smaller individuals are more adept at adjusting readily to the vagaries of aquarium life. An ideal range for purchase is somewhere between 2 to 4 inches in overall length.

Environmental: Conditions

Chemical/Physical: Filtration

Jacks are not particularly fussy as regards absolute water quality. Due to their continuous daytime cruising and prodigious waste production, strong circulation and high-power filtration is a requirement.

Display

Big, Bigger, Biggest… even bigger. With lots of water movement… plenty of space to move around. That's what these fishes need.

Behavior

Due to their size, food requirements, these fishes are typically casual toward other fishes other than the ones they can consume. Most species school together in the wild and if they are presented to you as more than one to a tank at the dealers you are best advised to maintain them as such (or as a pair if they are) in a system of several hundred to thousands of gallons in volume.

Introduction/Acclimation

First a note regarding netting. I strongly suggest you utilize two nets to direct these fishes into a stationary underwater container (doubled bags), rather than lifting the animal into the air. They assuredly will thrash around either way, but the latter is almost assuredly will result in more injury.

Once the fish is "home" it is best placed and left alone unfed in an unlighted system for a day. Jacks are one of my exceptions to the general rule of quarantine; most are clean and ready to go with just a preventative freshwater dip. Put another way, moving them again is not worth the damage that the small potential for disaster warrants from simple introduction to the main/display system.

Predator/Prey Relations

Jacks can be trusted with non-fishes in the way or sedentary invertebrates of all kinds. They will/do eat crustaceans, squids, worms… and small fishes in the wild.

Reproduction, Sexual Differentiation/Growing Your Own:

Some species of Jacks have been artificially spawned (through hormonal manipulation), raised to an extent of development in captivity for mariculture interests. There is no discernible differences amongst/between the sexes.

Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes

Readily take all kinds of foods… and quickly adapt to captive fare… more, and more frequently are the rules here in foods/feeding.

Disease: Infectious, Parasitic, Nutritional, Genetic, Social

Jacks are very resistant to infectious and parasitic disease. What are paramount with carangids are quickly receiving healthy specimens, a minimum of "handling" and their placement in proper circumstances

Close:

Do you have a huge system, with more than vigorous aeration, circulation, tremendous filtration and a big pocketbook for food and energy to keep Jacks? I would look for more suitable aquarium species if not. These are fishes for Public Aquariums and sportsfisherfolk.

Bibliography/Further Reading:

Baensch, Hans & Helmut Debelius, 1994.Marine Atlas, v. 1. Mergus, Germany.

Burgess, Warren E., Herbert R. Axelrod & Raymond E. Hunziker III, 1990. T.F.H. Publications, Inc. NJ.

Fenner, Bob. 2001. Do you know Jacks? The family Carangidae. FAMA 5/01.

Nelson, Joseph S., 1994. Fishes of the World, 3rd Ed. John Wiley & Sons, NY.


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