Crawfish
The Crawfish (Panulirus argus) is a nocturnal marine crustacean that is an important part of Bahamian culture. Common names include Caribbean spiny lobster, crawfish, rock lobster, Florida lobster, common spiny lobster, langouste blanche, langouste. They are found throughout tropical and sub-tropical waters of the Atlantic Ocean, Caribbean Sea and Gulf of Mexico. They occur in The Bahamas, Bermuda, the West Indies and South Florida. They shelter in crevices in the reef during the day and come out at night to forage in shallow water bank /seagrass areas feeding on detritus and invertebrates.
Anatomy
The crawfish has a spine-studded shell, long antennae but no large front claws. It is an invertebrate with a hard exoskeleton, 5 pairs of jointed walking legs, a segmented body and compound eyes on stalks. The Caribbean spiny lobster (crawfish) is characterized by 4 large cream colored spots on the first to sixth abdominal segments.
Life Cycle
Crawfish inhabit three distinct habitats during their life cycle. Larvae float on ocean currents; juveniles seek shallow areas with algal beds, such as, mangrove creeks and adults live in rocky areas and patch reefs.
Adults
Spiny lobsters reproduce year round, however there is a peak during the warmer months of the year (March –August in the Caribbean). Females have a “spur” at the tip of each of the last pair of legs and extra swimmerettes shaped like claws. Males have a padded opening at the base of each of the last pair of legs. Crawfish live in excess of 12 years and grow throughout their lives. They can grow to about 500 mm (20 in) and weigh 4.5 kg (10 pounds). Adults are usually found in coral reefs and rocky areas up to depths of 90 m.
Mating
The female lobster mates after molting. When she is ready to molt, she approaches a male's den and wafts a pheromone in his direction. During mating the male lobster transfers a packet of sperm (spermatophore) to the female where it sticks and appears as a “tar spot” between the last legs.
Eggs
The eggs are laid through holes at the base of the third pair of legs and are attached to hairs on the swimmerets. The female then scratches the tar spot to fertilize the eggs. As many as 600 000 eggs may be carried by a large adult female. The eggs are carried for about three weeks before they hatch, producing phyllosome (leaf bodied) larvae. Roughly 99% of those spawned will die. The amount of eggs fertilized also depends on the size of the male that produced the spermatophore. Small males mate once per year. Large males mate multiple times per year and produce more sperm.
Larvae
When first hatched, a lobster larva has feathery hairs on its legs to help it swim; they live as plankton, floating in the water column for about 6 – 10 months. Phyllosome larvae metamorphose (change form) into the puerulus post larvae stage, pueruli are transparent but resemble miniature adults. They settle to the ocean floor in near shore nursery habitats. Maximum settlement occurs from August to December in clumps of red Laurencia algae.
Juveniles
After a week post-pueruli become juveniles, bearing the striped and banded pattern of an adult crawfish. This coloration camouflages the juveniles from predators. Juveniles inhabit algal beds in mangrove creeks, coral reefs, sponges, caves and soft corals as they grow into adults. Crawfish take up to 3 years to reach adulthood and start reproducing.
Predators
Predators include sea birds, sharks, rays, snappers, groupers, octopus, dolphins and loggerhead turtles.
Prey
Crawfish are scavengers, their diet consists of detritus, small molluscs, starfish, urchins, small crustaceans, crabs and clams.
Crawfish fishery
The Bahamian crawfish fishery is the fourth largest in the world and second largest in the Caribbean after Cuba. It is of major economic importance to the commercial fishing industry of The Bahamas. Crawfish exports make up 40% of the total exports of the Bahamas and 60% of the total fishery product landings. In the Bahamas crawfish is considered abundant in general, with localized depletions near major population centres. In the Caribbean, crawfish fisheries are mainly at maximum exploitation or overfished. The continued success of the commercial fishing industry however depends on the use of responsible fishing methods and public respect for the fishing regulations.
Regulations
- Minimum size limits for crawfish -3 ¼ inch carapace or 5 ½ inch tail.
- It is illegal to posses egg-bearing (berried) females. Stripping or removing eggs is also prohibited.
- Closed season from April 1st – Jul 31st.
- A permit is required for all vessels trapping crawfish.
- Crawfish traps, unless otherwise approved shall be wooden slat traps not more than 3 ft in length, 2 ft in width and 2 ft in height, with slats placed no less than 1” apart.
- No person shall use or have in his possession: (a) dogwood or other poisonous barks; (b) quicklime;(c) household bleach or any other noxious or poisonous substances.
Fishing methods
Crawfish are fished three ways in The Bahamas
- Condominium or casitas are large sheets of aluminum placed on blocks, with three wooden enclosed sides and one open side. They are laid by fishermen to provide artificial shelters for crawfish. Divers then harvest crawfish which aggregate at these artificially created sites.
- Spearfishing – divers either free dive or use ‘hookas’ or air compressors to spear crawfish. Spearfishing is often associated with the use of bleach which drives crawfish out of crevices. This destructive practice is prohibited and is on the decline. It destroys coral reefs, important crawfish habitat.
- Trapping – traps are made of wooden slats and baited with cowhide.
Issues facing the commercial crawfish industry
Illegal fishing – Violation of the fisheries regulations by Bahamians and tourists, as well as fishing by foreign boats from The Dominican Republic, Cuba, Honduras and the US.
Harvesting of juveniles – Fisheries regulation impose a size limit on crawfish, they should have a minimum carapace length of 3 ¼ inch or 5 ½ inch tail length.
Duration of closed season – The current closed season of April 1st – Jul 31st is considered to be too short. Many have reported that females are often bearing eggs in August; there have been moves taken towards extending the season into August to allow the crawfish sufficient time to reproduce.
Use of Condominiums – It is unclear whether condos enhance crawfish populations by providing protection from predators or whether they simply relocate crawfish from the reef. The use of these aggregating devices are a more efficient means of trapping crawfish than either trapping or spearing and may result in overexploitation of the resource.
Enforcement of fishing regulations – enforcement at sea is the responsibility of the Department of Fisheries and the Royal Bahamas Defence Force, owing to the vast nature of the Bahamian fishing grounds, this becomes difficult. Fishermen are encouraged to report violations.