Nurse Sharks 101

Nurse Shark on the Ocean Floor

Nurse Shark Anatomy:

The sub-terminal mouth is placed well in front of the eyes. The spiracles are minute and moderately long barbels reach the mouth. Nasoral grooves are present, but there is no perinasal groove. The nurse shark is ovoviviparous, which means that the female shark carries the fertilized eggs in egg cases within her ovaries. The embryos receive nourishment from the yolk in the egg cases, and once that’s finished, the shark pups hatch from the egg case and are soon born. The gestation period for nurse sharks is about six months. Nurse shark pups start life at about a foot long. Once a female has produced a litter, it takes her 18 months to produce more eggs. The nurse shark has thousands of replaceable teeth which are serrated and fan shaped; they are capable of crushing shellfish. The teeth are arranged in rows that rotate into position when one is needed (when older ones are broken or lost).

Nurse Shark Biography:

The origins of the name “nurse shark” is unclear. It may come from the sucking sound they make when hunting for prey in the sand, which vaguely resembles that of a nursing baby. Or it may derive from an archaic word,  nusse, meaning cat shark. Nurse sharks are slow-moving bottom-dwellers and are, for the most part, harmless to humans. However, they can be huge- up to 14 feet and have very strong jaws filled with serrated teeth and will bite defensively if stepped on or bothered by divers who assume they’re docile. Nurse sharks are nocturnal and will often rest on the sea floor during the day in groups of up to 40 sharks. At present there is not a fishery for this species. The fins are not marketed and the meat, although edible, is not often retained for human consumption. However, it is sometimes sold as crab bait. Nevertheless, nurse sharks are caught and killed by fisherman in some regions because they are considered a nuisance animal that takes bait intended for other species. In the lesser antilles, where it often raids fish traps,  it is considered a pest. Commercial fishers in the United States routinely release nurse sharks alive. In the past, nurse sharks were sought for various reasons. The liver oil often was used as fuel. The oil was also used by commercial sponge fishers to calm the water surface, allowing them to more readily locate sponges on the sea floor. The skin was considered the best of all elasmobranch species, being extremely tough and thick it was used to make high quality leather. The skin also was occasionally salted for human consumption.

Geographic Location:

Common in the Atlantic and in the Eastern Pacific, in Coastal tropical and sub-tropical waters. Reported from Senegal to Gabon, Rhode Island to Southern Brazil, and Mexico to Peru. Also, some individuals have been reported in the Gulf of Gascogne in Southwest France. This species is locally very common in shallow waters throughout the West Indies, South Florida and the Florida Keys. Apart of the Eastern Pacific, the nurse shark in absent from the indo-pacific area, where other related groups have successfully evolved.

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