Jackknife Fish (Equetus lanceolatus)
The jackknife fish (Equetus lanceolatus) is an interesting shaped fish from the family Sciaenidae.
This fish isn't as commonly found in the home aquarium as many other marine fish species, but it is an interesting and graceful fish.
The body shape and appearance of the jackknife fish is said to confuse predators by appearing to be two different fish rather than just one fish. (However, it still looks like only one fish to me, but what do I know? I'm not a fish predator - I'm a vegetarian.)
Jackknife fish are found in the Western Atlantic and Caribbean.
It reaches a size of approximately 10 inches (25 cm) when full-grown.
It is a shy fish and needs plenty of hiding spots in the form of caves and crevices from well-established live rock.
Jackknife fish will often eat the inhabitants of a reef tank, such as ornamental shrimps, polychaete worms, and sometimes, fireworms. They will also eat small reef fish.
The jackknife fish is somewhat difficult to feed in captivity.
This is typically the problem when bringing a fish species into captivity, such as the jackknife fish, and then not providing it with the reef inhabitants it normally finds to eat in its natural habitat. We don't want our reef inhabitants to be eaten, but getting a new fish that is used to eating off the reef to eat a substitute diet is often difficult.
In the beginning it won't recognize frozen marine foods as fish food. This is why having well-established live rock and sand available is so important. At least this fish is used to finding food from these sources.
Live foods may be required to induce feeding behavior. Try live vitamin-enriched brine shrimp, mysis shrimp, black worms, or even small live fish. Jackknife fish are carnivores.
Eventually your jackknife fish may accept frozen marine meaty foods, as well as chopped up seafood. At least if you have provided your jackknife fish with well-established live rock and sand it will have a familiar food source while it is learning to eat a substitute diet in captivity.
To keep a jackknife fish healthy and happy you'll need a spacious aquarium with plenty of hiding places. Also, don't overcrowd their tank. It is best to only keep them with peaceful species, and don't keep them with small fish that may become their dinner unless this is what you intend to have happen.
You may keep more than one jackknife fish in your aquarium as long as they are added at the same time. Make sure there is plenty of room and hiding spots for everyone.
Jackknife fish can be obtained for about $75 each.