Crevalle Jack: Fish, Fishing, and Robotics, by Don Orth

The Crevalle Jack Caranx hippos is a prized game fish especially in the Gulf of Mexico.  The scientific genus name, Caranx is derived from the French word, carangue, for a Caribbean fish, and hippos is Greek for “horse” There are six species of Caranx with a cosmopolitan distribution in tropical and subtropical waters of the Atlantic Ocean and some extend to temperate zones.  All 150 species of Carangidae have hard scutes that run forward of a sickle-shaped tail. Crevalle Jacks are countershaded with greenish-bluish to black on dorsum and silvery to golden on ventral surface.  A small black spot on opercular margin and a black blotch on lower pectoral fin rays.  Young jacks provide food for numerous carnivorous fishes while the adults are carnivores.  

From Biodiversity Heritage Library, Marcus Elieser Bloch Oeconomische Naturgeschichte der Fische Deutschlands

The Crevalle Jack was described by Linnaeus in 1766 as Scomber hippos from a dried specimen. However, in 1801, Bernard Germain de Lacépède  reassigned it to the genus Caranx and the taxonomy remained uncertain until recent times. The Crevalle Jack complex is now recognized as three species; Caranx hippos in the Atlantic, Longfin Crevalle Jack Caranx fischeri in the Eastern Atlantic (sympatric with C. hippos), and Pacific Crevalle Jack Caranx caninus in the Pacific (Smith-Vaniz and Carpenter 2007).   
   

The Crevalle Jack represents a common morphological adaptation for rapid and efficient swimming. The streamlined body, deeply forked caudal fin, narrow caudal peduncle, and scutes that form a lateral caudal keel all contribute to reduced resistance during swimming. In fact, the swimming mode is named carangiform swimming. Carangiform swimming is a type of cruising in which approximately half to two thirds of the body is not very flexible and bends only slightly during swimming.  The back third provides the forward thrust propelling the fish forward. Carangiform swimming allows for high sustained swimming speed, but not quite as fast as tunas, marlin, and sailfish. It is very difficult to study the realized maximum sustained swimming speed in the wild and most reports of swimming speeds are not to be trusted.  Consequently, we don’t really know how fast a Crevalle Jack can swim in the wild.  If we apply 4.5 body lengths/s from lab experiments of Dickson et al. (2012), one would extrapolate that a 1 meter long Crevalle Jack could swim at 4.5 meters/sec for 30 seconds -- more than enough to bend your rod tip. 

Tail motion in carangiform fish from Liu and Hu (2010).

Liu and Hu (2010) studied the carangiform swimming mode in order to simulate motion control in a bionic fish.  This is more difficult than one might imagine. It requires separate motion control algorithms for cruising and maneuvering.  Cruising is swimming at a constant linear or angular speed, whereas maneuvering involves actions such as acceleration, deceleration, quick turning, up/down motions, and hovering. 

 Robotic fish  from Liu and Hu (2010).

Adult Crevalle Jacks feed on schools of small fish and schools of Crevalle Jacks work to trap baitfish at the surface, creating a feeding frenzy.  This video  from Florida Fish and Wildlife Conservation Commission shows how a school of Crevalle Jacks have trapped many Pinfish Lagodon rhomboides nearshore.   Typically, schools of Crevalle Jack will corner a school of baitfish at the surface and feed with commotion that can be seen at great distances. Crevalle jacks are common in both inshore waters and the open sea, and they feed mainly on small fish.

Crevalle Jack. Photo by Brett Albanese

Crevalle Jacks may be found inshore or offshore and often schooling with other jacks, though larger specimens (up to 5 feet) are often solitary.   Life history of Crevalle Jack is all about growing fast, producing many small eggs, and breeding in large aggregations in estuaries and inshore reefs. Eggs ride the currents and the small larvae are pelagic and as they grow and develop.  Juveniles are associated with buoys and Sargassum weed, a behavior known as ‘piloting’ (Hunter and Mitchell 1968).  Juveniles have a deeper body form than adults and have 5 dark bars that remain until the fish reaches about 6 inches in size.    

Illustration of juvenile Crevalle Jack at 15.3mm.  From Berry 1959.

Crevalle Jacks are a popular game fish. Because they are open water predators that chase prey fish to the surface, anglers can target Crevalle Jacks. Any fast-moving fish-mimicking lure will do. Their adaptations for swimming mean they put up a powerful fight for their size and often fight to exhaustion.  The Texas record is 52.25 inches, 50.25 pounds.  Sport anglers typically practice catch and release and are encouraged to resuscitate fish to minimize release mortality.   Increase the odds they will live to fight again!

Release of captured Crevalle Jack.  Source

Crevalle Jack have good quality flesh, as long as they are bled immediately.  Caranx species are important to artisanal fishers in many tropical regions.  Further, they have great aquaculture potential in Brazilian waters as they are well adapted to captivity in near-shore cages (Rombenso et al. 2016). 
 

References

Berry, F.H. 1959.  Young jack crevalles (Caranx species) off the southeastern Atlantic coast of the United States. Fishery Bulletin 59:417-535.

Dickson, K.A., J.M. Donley, M.W. Hansen, and J.A. Peters. 2012. Maximum sustainable speed, energetics and swimming kinematics of a tropical canangid fish, the green jack Caranx caballus. Journal of Fish Biology 80:2494-2516.  

Hunter, J.R., and C.T. Mitchell. 1968. Field experiments on the attraction of pelagic fish to floating objects.  Journal du Conseil - Conseil Permanent International pour l'Exploration de la Mer 31(3):427-434.

Liu, J., and H. Hu. 2010.  Biological inspiration: From carangiform fish to multi-joint robotic fish.  Journal of Bionic Engineering 7:35-48.

Rombenso, A.N., J.C. Bowzer, C.B. Moreira, and L.A. Sampaio. 2016.  Culture of Caranx species [Horse-eye Jack Caranx latus (Agassiz), Blue Runner Caranx crysos (Mitchill), and Crevalle Jack Caranx hippos (Linnaeus)] in near-shore cages off the Brazilian coast during colder months. Aquaculture Research 47:1687-1690.

Sánchez-García, C., O. Escobar-Sánchez, M. Candelaria Valdez-Pineda, J.S. Ramírez-Perez, R.E. Morán-Angulo, and X.G. Moreno-Sánchez.  2017.  Selective predation by crevalle jack Caranx caninus on engraulid fishes in the SE Gulf of California, Mexico.  Environmental Biology of Fishes 100:899-912.

Smith-Vaniz, W.F., and K.E. Carpenter. 2007. Review of the crevalle jacks, Caranx hippos complex (Teleostei: Carangidae), with a description of a new species from West Africa. Fishery Bulletin 105:207–233.