Lemon Shark With RemorasPOTW June 26, 2017
This week’s POTW is a shot of a lemon shark accompanied by a squadron of remoras. The shot is from a trip I made in 2008 to a site in the Bahamas known as Tiger Beach. As the name suggests, Tiger Beach is a place where a lot of divers have seen and photographed tiger sharks. But you don’t want to overlook the lemon sharks as these beauties usually outnumber the tiger sharks.
Lemon sharks are so named for the pale yellow color on their underbellies. This coloration is unusual in the world of sharks. In addition, lemons are characterized by their heavy bodies, short snouts and evenly sized dorsal fins. They are members of the family of requiem sharks, Carcharhinidae, a group which includes many species commonly encountered on coral reefs. Most of the sharks in this family are not easily distinguished, although the yellow coloration of the underbelly lemon sharks makes it considerably easier to identify this species in natural settings
Lemon sharks occur along the eastern coast of the United States from New Jersey south all the way to Brazil as well as in Eastern Pacific waters from the southern end of Mexico’s Sea of Cortez to Ecuador. They are particularly prevalent in coral reef ecosystems, especially in sea grass and mangrove habitats. Unlike most shark species, lemons are extremely tolerant of shallow, warm waters consistent with those in mangrove swamps. Lemon sharks are active during daylight and nighttime hours, with their activity peaking at dusk and daybreak.
Lemon sharks usually feed on crustaceans, other sharks and rays, and a variety of bony fishes in the lagoons, estuaries and sand flats. As with other members of the Carcharhinidae family, lemons make seasonal migrations in search of food. Studies have shown their ability to detect variations in the earth’s magnetic field is a key factor in the ability of lemons to orient themselves during migration.
Lemons are known to have a keen sense of hearing and a well-developed sense of smell. They utilize their sense of smell to detect potential prey and to sense the differences in salinity of water. Scientists believe the ability to sense variations in salinity assists females in locating nursery grounds where pups are born live. Litter sizes vary from as few as four pups to as many as seventeen.
Full-grown lemon sharks are known to reach a length of just over eleven feet. Scientists have determined that lemons live as long as 75 years in natural conditions, and might live for as many as 125 years or more.
Like a variety of sharks, dolphins, turtles, whales and bony fishes, lemon sharks are often accompanied by remoras.
The relationship between remoras and the host animals they attach to and accompany is not completely understood. While it might seem that this relationship is an example of commensalism, a relationship in which one party benefits without harming the other, the relationship is beneficial to both parties. Scientists believe that remoras gain protection by associating with such large animals. After all, a potential predator would have to be rather “big and bad” to pursue a fish that is attached to the body of a large shark. Remoras also benefit by being supplied with a source of food as they prey upon a variety of parasites that are found on the skin of their hosts. The remoras also feed on scraps of food from the meals of their hosts. By feeding on the organisms parasitizing their hosts, the presence of the remoras serves to benefit their hosts. Remoras do not suck blood or body tissue from their host.
Just as is the case in other walks of life, there is no such thing as a “free lunch” in the ocean. While the hosts do the work of finding and killing the prey that the remoras often consume, the remains of remoras are often found in the stomach content analyses of sharks and other host animals. The only logical conclusion is that the remoras become “fair game” for their hosts when they let go of the hosts. Remoras can let go at any time, and at times they are quick to change hosts.
I hope you enjoy this week’s POTW!
See you next week,