Hornaday, William Temple, The American natural history : a foundation of useful knowledge of the higher animals of North America, Vol IV, Reptiles, Amphibians, and Fishes, at 246, 1914. Drawn by J. Carter Beard.

I’ve been reading about tarpon. There are more alien things, eyeless lizards that live in the depths of caves, big-eyed large-toothed fish at the bottom of the sea, sloths, but I haven’t been reading about sloths.  I’ve been reading about tarpon. And one shouldn’t fly fish for sloths.

Hornaday, William Temple, The American natural history : a foundation of useful knowledge of the higher animals of North America, Vol IV, Reptiles, Amphibians, and Fishes, at 246, 1914, at 279. Drawn by J. Carter Beard

There are two species of tarpon, our tarpon, Megalops atlanticus, and the Indo-Pacific tarpon, Megalops cypnrinoides. The Pacific tarpon ranges from the east coast of Africa to the Indian Ocean or thereabouts–my geography gets a bit vague.  Atlanticus, our tarpon, ranges down the Atlantic Coast  from Virginia to Brazil. They move through the Panama Canal to the western coast of Panama.  There are populations in the eastern Atlantic on the west coast of Africa ranging from Senegal to the Congo. Wherever they are, Atlantic tarpon aren’t made up of genetically distinct populations.  They may only be cousins, but genetically they’re kissing cousins.

Everyone who fly fishes admires all things anadromous: Salmon, steelhead, striped bass, even the lowly shad. These are fish that do it up right. They’re spawned in freshwater rivers, go to sea to grow, and then in their turn return up-river to spawn. It’s a perfectly reasonable life cycle.  Join the navy, see the world.

There are other ways to do it though.  The counterpoint to anadromous is catadromous, which is how the Chesapeake drainage American eel reproduces. Catadromous is peculiar, at least to my ears. True eels are born in saltwater, then the larvae drift with currents into freshwater and grow into adulthood upriver.  When it’s time the eels migrate back to the ocean to spawn.  It’s just wrong. Not that it takes much for eels to seem wrong.

Uwe Kils, eel larvae of Anguilla rostrata, 2003

Tarpon are not considered catadromous, but are often compared to eels because of the larvae stage.  Like eels, tiny tarpon larvae migrate via currents inshore. Unlike eels, tarpon can develop as juveniles in any estuarine environment, salt, fresh, or brackish, and as adults they move back and forth  between salt and estuary, and even upriver into fresh.  Twenty years ago we didn’t know much about tarpon: I’ve read old stuff that says we don’t know if they spawn inshore or offshore. Now folks know more. They spawn offshore, maybe as far offshore as 100 miles. They broadcast spawn, so there’s not a lot of close and personal, but there’s at least got to be some vicinity. The lady tarpon flings out her lady stuff and the boy tarpons fling out their boy stuff and the eggs get fertilized in the deep blue sea. There’s no eHarmony for tarpon, so without spawning grounds, how would tarpon meet up? How would they get to the same place at the right time to fling their stuff?

Identifying and protecting spawning grounds would be a good thing.  Tarpon are considered a vulnerable population by the International Union of Conservation of Nature. Some folk eat tarpon, particularly in Central America, Columbia, and the Caribbean, and they’re killed as by-catch in commercial fisheries. Juveniles require relatively specific habitat to mature, and that habitat is shrinking with coastal development and damage to water quality. They’re also killed by anglers, both intentionally and as a by-product of catch and release. The IUCN reports that over-exploitation of tarpon by sport fishers is a particular problem in southwest Florida, and neither Mississippi nor Louisiana have tarpon catch limits. Absent predation by sharks, the IUCN estimates post-catch mortality of adult catch-and-release tarpon at 5 percent. In a 2005 study in Tampa Bay, the Florida Fish and Wildlife Conservation Commission estimated that with shark predation figured in, tarpon mortality after release was about 10 percent.

Populations of adult tarpon are thought to be both migratory and resident. Migratory Texas tarpon have been tracked from the middle Texas coast nigh on to Quintana Roo.  Researchers track Floridian west coast tarpon up the Florida coast (with the height of the season in Tampa from May to July) on around the Gulf Coast to Louisiana–these are travelin’ fish–but lodges in Belize and Nicaragua routinely advertise resident tarpon. As tracking studies get more sophisticated, researchers hope to get better population numbers by figuring out how and how many fish migrate.  And maybe someone will let me know where the tarpon hide in Galveston Bay.

Being strange and witchy creatures, it’s fitting that the tarpon spawn is linked to moon phases, the new and full moons.  That must be why their eyes are up top on their heads. One wouldn’t want to miss a good spawn because one wasn’t looking up at the moon (or absence thereof). If I were a tarpon, it would be just my luck to be caught looking at my shoes while the other tarpon were out on the town.

NOAA, Southeast Fisheries Science Center