Fish o' the Day - cobia

The last of our coastal fish, for the time being.  Tomorrow, I anticipate having some entries contributed by the students in my summer fish class.  Tonight, we'll look at the cobia, Rachycentron canadum, the only living member of its family, the Rachycentridae.  The genus (and family) name translates roughly to "stinging spines" a reference to the short, stout spines supporting the dorsal fin.  Like a couple of freshwater fish we've seen (the bowfin comes to mind), the cobia is known by many other names to those that encounter it in tropical and temperate waters.  On the Gulf Coast, ling and lemonfish are common nicknames.  Where they're encountered in the Pacific, they may be known as black kingfish or aruan tasek.  Wherever found, they're big, powerful fish, reaching a length of six feet and weighing as much as 100 pounds.  The body is long and sleek, with a flattened head and small eyes.  A chocolate brown dorsal coloration grades to a white belly.  A pair of bands on their sides are more pronounced during the spawning season.  The lower jaw protrudes a bit past the upper jaw, giving them a pugnacious look.  The body shape, along with the large pectoral fins, gives them a distinctly shark-like appearance, and cobia hanging beneath the surface are frequently mistaken for small sharks.

Surprisingly, cobia's closest relatives include the remoras in the Family Echeneidae.  As juveniles, they more closely resemble remoras, although they don't have their characteristic dorsal attachment structure.  Cobia are pelagic fish (making their lack of a swim bladder a little surprising).  They're typically solitary, except when they form spawning aggregations.  They're fond of structure, and can often be found beneath floating objects (debris, seaweed, etc.).  Cobia will feed on a variety of prey, but seem to be particularly fond of swimming crabs.  They're migratory, with a population wintering off south Florida and migrating north in the spring.  They're fished heavily at that time, and the first "ling" of the year is always big news.

Nice video here of a group of cobia.