Nurse Shark (Ginglymostoma Cirratum)

Documented life stages: Embryo, juvenile, and adult stages

Size: Up to 14 feet (473 cm)

Color: Yellow brown to gray brown; juveniles display dark spots on body

Coastal distribution: Rhode Island to Brazil; Gulf of Mexico

Habitat: Continental and insular shelves, coral reefs, shipwrecks, rocky areas, channels, sandy areas, vegetation beds, marshes, mangroves, and offshore

Local range: Lower Chesapeake Bay; summer and fall

Availability: Rare

Natural salinity range: Above 30 ppt

Salinity zone preference: Marine

Natural diet: Fishes (catfishes, mullets, puffers, stingrays, and crustaceans (spiny lobsters, shrimps, crabs, sea urchins, squids, octopi, snails, bivalves))

Aquarium diet: Small live fishes, shrimp, mollusks, crabs, and chopped seafood

Juvenile aquarium: Above 1,000 gallons (3,800 liters); moderate currents; open to rocky habitat; secured tops; 30–35 ppt salinity; 70–80 °F (21–27 °C)

Aquarium adaptation: Good to difficult

Compatibility: Good with other sharks and large fishes

Biology: Nurse sharks are typically bottom sharks that exhibit sluggish movements. Although they swim in the water column, they usually stay close to the bottom. Tropical strays primarily constitute northern range populations. They migrate north in the Gulf Stream during the spring and summer. Their social habits are described as mostly solitary. Highly specialized gill muscles allow them to remain stationary for extended periods on the bottom while breathing. Their nasal barbels and short teeth enable them to search the bottom sediments and crevices for benthic prey. Unlike pelagic sharks on the move, nurse 20 sharks patiently locate and extract benthic food organisms. Shallow Caribbean and South Florida waters are the breeding grounds for nurse sharks. Mating pairs will swim parallel to each other, with the male swimming slightly behind the female, biting her pectoral fin and rolling her over. They swim around locked for a brief period before disengaging and rapidly swimming away. Ovoviviparous reproduction results in ovarian eggs and embryos being released into the uterus to further develop into well-developed newborns or "pups". Fecundity ranges up to 28 pups. Captive nurse sharks have been laboratory trained to associate underwater cue cards with the presence of food. Making body contact with a symbol cue card, they can be rewarded with food as positive reinforcement. This is highly comparable to the classic Pavlovian instrumental conditioning experiment with dogs.

Remarks: Nurse sharks are among the easiest of all shark species to transport and maintain in captivity. They are frequently used in research laboratories, public aquariums, and large home aquariums. Aquarium hobbyists will learn that nurse sharks rapidly outgrow small aquariums which cause restricted movements and cause the frustrated sharks to jump out of the aquarium or knock and break the glass. Keep this in mind when near electric sources. Nurse sharks show no aggression toward scuba divers and will ignore their presence. Exceptions occur when careless divers grab at nurse shark tails and attempt to yank them from their business. Nurse sharks then resort to a rightful course of defensive action by coiling back and biting their human predator. Because of their vacuum suction mode of feeding, unwary divers have often emerged with a nurse shark locked onto their body like a leech. Their removal often requires painfully prying the locked jaws off the diver or a trip to the hospital to have the shark removed.