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Guy Harvey

Just wearing snorkelling gear, I was being towed behind an inflatable dive boat in 20 feet of water, holding on to a planer sled travelling along a three mile long coral barrier reef called Banner Reef. Its location is on the south side of Pedro Bank, a hundred miles south of Jamaica. I was part of a research team locating and documenting Spanish shipwrecks around Jamaica with the Institute of Nautical Archeology from Texas A&M University. Not only was this a great opportunity to learn more about underwater archaeology, but also a great chance to visit some of the remote pristine reefs on the outer margins of Jamaica’s Exclusive Economic Zone.
 
We located several wreck sites in shallow water, characterised by the pile of ballast stones and protruding anchors and cannons festooned with coral and marine growth. I was amazed at the surrounding acreage of elk-horn coral and in the sand channels between, dozens of nurse sharks. These large sharks were resting on the sandy bottom partly hidden by the elk-horn growth. I jumped off the sled and dived down for a closer look. There were a couple of nurse sharks out in the open but more inside a coral cave, piled on top of each other in an untidy mess.
 
Startled by my proximity, they unwound and headed out of the safety of the cavern. As I went further down the reef, dodging the numerous barracudas that were attracted to the sled, I spotted another group of nurse sharks. They were all big ones of nine feet long. They are characterised by their large square head, very small eyes, small mouth and they have a long barbell on the front of each nostril. Their large dorsal fins are set well back on their body and the upper lobe of the tail is very long whereas the lower lobe is shortened, as they spend so much time resting on the bottom. They are usually brownish-gray with no distinct markings, and when viewed from above, the typical aspect for a snorkeler, they have a very sinuous swimming motion.
 
As common as they appeared to be around Jamaica and these offshore banks, the nurse shark is not common in Cayman, in fact I encounter more Caribbean reef sharks here than nurse sharks. One day snorkelling near Pigeon Island off Old Harbour, I found a shallow, protected lagoon. A sudden commotion in the shallow water caught my attention and I quickly swam over to see what was happening. A female nurse shark was having pups. These little guys are perfectly formed 18-inch versions of mum were taking their first plunge. As I circled the lagoon, I saw some more slightly larger juveniles hiding out amongst mangrove roots and associated marine growth. These juveniles are targeted by adult lemon, reef and bull sharks, so they are birthed in shallow protected lagoons to escape these predators.
 
However these juvenile nurse sharks are a favourite of fish collectors for the aquarium trade, as they seem cute, but they are very tough and resilient fish. However, they grow fast under these conditions, and eventually become too big for their surroundings.
 
Like all sharks and rays, nurse sharks live for a long time, perhaps 50 years or more and will grow 14 feet. They are common in shallow back reef areas as well as being found on the deep fore-reef. They are nocturnal predators, which is why we normally encounter them under coral ledges, resting in the day time. By night they are out hunting fish resting in coral crevices, slurping up crabs or lobsters that are exposed on the sand looking for their food, other items such as small stingrays, plus a variety of other crustaceans.
 
Although nurse sharks have a small mouth they use a very powerful sucking action to inhale their prey and the rows of fine teeth can cut chunks out of larger food items such as a dead fish. Using their rubbery skin, flexible body and tough head they can squirm into narrow openings in the coral to search for fish, and then suck them down with their powerful jaws. If molested by a diver they have been known to bite back and hang on with considerable force. Divers….do not be tempted to pull on that shark’s tail you see protruding from the coral cave in front of you!
 
A single species of nurse shark occurs on both sides of the Atlantic in tropical and sub tropical locations, and a similar species is found throughout the Indian and Pacific Oceans. In many locations in Florida, the Caribbean and in the Bahamas, nurse sharks are a key participant in organised shark interactive programmes, where they interact with Caribbean reef sharks, black tips, bulls and lemon sharks providing the divers and photographers with a variety of species to experience at one location in a controlled environment.
 
Anglers are most likely to encounter a nurse shark while fishing for bonefish and permit in the shallow waters off Barkers, South Sound or Frank Sound around Grand Cayman, and in similar back reef locations around the Sister Islands. The long dark shape sinuously swimming over the sandy or grassy bottom is easily identifiable and this species poses no threat to the wading angler. While lemon sharks, black tip sharks and great hammerhead sharks are targeted by fly fishermen, the slow moving nurse shark does not attract much attention.
 
Though fairly common, nurse sharks are not abundant anywhere in their range and so far have not been targeted for their meat or large fins as have many other species of inshore sharks.
It is our collective responsibility to conserve the marine environment and maintain the biodiversity of the planet. Dive safely. Fish responsibly.   WH
 
Guy Harvey PhD.
www.guyharvey.com