Caribbean Spiny Lobster
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Central Mangrove Wetlands
The Caribbean Spiny Lobster (Panulirus argus) is a popular food item in many homes and restaurants throughout the Cayman Islands. As a result, their population has dramatically declined over the last 20-30 years. Marine Conservation Laws are in place to protect a number of commercially valuable species at risk of over exploitation, including the lobster.
There are 35 species of lobster, in six families, which occur in the Caribbean Sea and neighbouring waters. The Caribbean Spiny Lobster is the most abundant species, getting its name from the sharp spines that adorn its hard outer shell and antennae.
Lobsters belong to the subclass Malacostraca, which includes shrimps, crabs and other crustaceans. Their bodies have 19 segments, each with a pair of legs. The first 13 segments are fused together forming a rounded outer shell or carapace. The head region of the carapace contains the eyes, long whip-like antennae, flexible antennules and jaws. The thorax region of the carapace contains the five pairs of spindly legs with the last 6 segments forming the abdomen and tail fan. Caribbean Spiny Lobsters have a brown background colour with four cream coloured spots on the dorsal surface of the abdomen and much smaller cream spots scattered over the rest of its body.
In order to avoid the ever-present threat of capture, lobsters will always face their potential predators. In this position they are best able to use their large abdominal muscles and tail fan to rapidly propel them backwards and away from an advancing predator. An additional defense mechanism is their ability to break off, or assist in breaking off, an appendage when caught. Once free from the predator's grasp the lobster can then flee to the safety of the reef and, in time, will re-grow its missing appendages.
Lobsters begin life as tiny, transparent, spider-like larvae. Females release millions of larvae into the adjacent oceanic current during the reproductive season. Larvae spend 8-12 months in the ocean currents feeding on microscopic animals. They are able to travel short distances quickly and use the claw-like ends of their legs to pierce and hold prey. They are extremely greedy predators, attacking animals equal to or greater in size to themselves.
After 8-12 months in the ocean, the larvae molt into the puerulus stage; a transparent, miniature adult form. The sole purpose of the puerulus is to get itself into coastal waters in time for its molt into a juvenile lobster. It does not eat and travels in the top 2 cm of the water column during the darkest hours of the night. Once in waters less than 8 metres deep, the puerulus will bury itself in the sand during its non-active hours. The journey reaches its end when the puerulus finds a suitable habitat, such as an algal mat clinging to a red mangrove root, on which to settle.
After a few days on its new algal mat home, the Caribbean Spiny Lobster puerulus molts into a colourful, sedentary juvenile lobster. The colouration is a cryptic blend of bands and lines camouflaging the lobster against the algae. Here it feeds on crustaceans and mollusks during the night, when it is least likely to be seen, and hides during the day. This behaviour pattern will continue throughout its adult life. Approximately seven months after settling within the mangrove roots, the juvenile lobster will have grown to 12.7 cm. (5 in.) in length and will leave the algal mat for a more nomadic existence. The Caribbean Spiny juvenile lobster now frequents rocky holes, small ledges and undercut edges of seagrass beds where other lobsters are living. They are constantly on guard from predators like nurse sharks, octopus, groupers, large rays and trigger fish. In approximately three years, the lobsters mature and move to the outer edges of the reef to mate.
At the outer edges of the reef the lobsters are close to the offshore oceanic currents that disperse their larvae. The males are territorial with regard to reproductively active females and the largest 2 or 3 males on the reef will mate with most of the females. Males are normally larger than females and tend to initiate the courtship behaviour. In courtship, the mating pair face-off with antennae pointed at each other. After several minutes they gradually move towards each other swinging their antennae out to either side. In this position they touch and vibrate their antennules rapidly against one another. After a few minutes the male closes in on the female. Both are now standing high on their legs. The male grabs the female with his front legs, swinging his abdomen underneath her. He deposits his spermatophore or 'tar spot' (sperm mixed in a gelatinous matrix) on the underside of the female where it remains until ready for use.
Female lobsters spawn 2-3 times during the reproductive season and not all mate prior to spawning. A female will spawn anywhere from a hundred thousand to over three million eggs at a time depending on her size. When spawning, she creates a spawning chamber by cupping her tail and extending her tail fan over her gonopores at the base of her third pair of legs. She then discharges her eggs through the gonopores into this chamber where they are fertilised by the sperm released by the female by scratching the attached spermatophore. Once fertilised, she then cares for her eggs, now attached to the underside of her tail, for 3-4 weeks until they are ready to hatch.
In 1987 the Marine Conservation Laws were implemented designating a closed season for lobsters from March 1st to November 30tht, a limit on the minimum size (15cm / 6in. tail length) and a maximum number of lobsters allowed to be taken (3 per person per day or 6 per boat per day - whichever is less). The laws also designate marine protected areas (Marine Parks, Replenishment Zones and Environmental Zones) that prohibit the taking of lobsters at any time. Local fishermen once claimed colossal numbers of lobsters, but recent research indicates that numbers are declining. For more information see our sustainable seafood program Cayman Sea Sense.
The apparent decline in the local Caribbean Spiny Lobster population is thought to be due to its demand in the booming tourism industry and its past popularity as fish bait. Lobsters were regarded as prime bait by local fishermen and juvenile lobsters residing in the shallow waters around the Cayman Islands were easier to catch than the adults in deeper water. The removal of immature lobsters means there are no replacements for the aging, reproductively active adults. This leads to fewer acts of reproduction, putting greater stress on lobster populations. In addition, the impact of lobster poaching signals a worrying time for the Caribbean Spiny Lobster.
Furthermore, the numbers of immature lobsters finding their way into local waters appears to be low and sporadic. A study assessing Caribbean Spiny Lobster populations in the North Sound, Grand Cayman's largest lagoonal environment in which lobsters might settle, is being conducted by the Cayman Islands Department of Environment. With the information gained from this project, the Department of Environment hopes to find ways to protect the existing populations of immature lobsters entering our waters and, in doing so, ultimately increase the number of adult Caribbean Spiny Lobsters in the North Sound.
Last Updated: 27 Jun 2012