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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.
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.
Some species only grow to eighteen inches (50 cm.) in length, others to more than six feet (two meters). They are remarkably fast growers.
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).
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.
Other Non-Hobbyist Species of Jacks...
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.
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.
Big, Bigger, Biggest… even bigger. With lots of water movement… plenty of space to move around. That's what these fishes need.
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.
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.
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
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.
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.