Ascension : Conservation Weekly
Submitted by The Islander (Conservation Office) 09.02.2012 (Article Archived on 23.02.2012)
Crayfish is one of the many names used for the Spiny Lobster, Panulirus echinatus. Other names given to this crustacean are long legs, crawfish and crawdad
Ascension Island Conservation Department
Ascension Island Marine Life
Contributed by Natasha Williams
Crayfish (Spiny Lobster)
Crayfish is one of the many names used for the Spiny Lobster, Panulirus echinatus. Other names given to this crustacean are long legs, crawfish and crawdad.
Crayfish is typical of most shrimp like crustaceans and is characterised by a joined head and thorax, midsection, and a segmented body which is sandy yellow, green, white, pink or dark brown in colour.
The size of Crayfish varies across the oceans - here in Ascension’s waters we have some of the largest that grow up to approximately 40cms in length. Amongst the smallest is the 2.5cm long Cambarellus diminutus of the south-eastern United States. Among the largest is Astacopsis of Tasmania, its length may also reach over 40cm and its weight about 3.5kg (8lbs).
The head has two pairs of sensory antennae and a pair of eyes on movable stalks. The appendages of the thorax include four pairs of walking legs which, as well as walking, are to probe cracks and crevices between rocks looking for food. All legs can be regenerated if broken off.
Crayfish have a hard outside skeleton. This jointed exoskeleton provides protection and allows movement, but limits growth. As a result crayfish regularly gets too big for its skeleton, sheds it and grows a new larger one. This called molting, and occurs six to ten times during the first year of rapid growth, but less often during the second year. For a few days following each molt, crayfish have soft exoskeletons and are most vulnerable to predators.
Crayfish often conceal themselves under rocks. They are most active at night, when they feed. Adults one year old become more active at dusk and continue heavy feeding activity until daybreak. Young crayfish are more likely to be the ones out during bright sunny days, while the older crayfish are more active on cloudy days and during the night. General movement is always slow, but if startled, crayfish use rapid flips of their tail to swim backwards and escape danger.
Generally Crayfish species live short lives, usually less than two years. Therefore the rapid, high volume reproduction is important for the continuation of the species.
Crayfish are very easily damaged and have little chance of survival if you break legs or antennae off. Crays sitting with their tails curled underneath them are most probably are in berry (carrying eggs), and should be left alone. Crays who are nearly sitting out in the open and appear dopey are most probably soft-shelled and should be left alone as well. When handling Crayfish that you intend to return to its habitat, you should do so with extra care, and avoiding exposing them to sunlight which causes blindness.
Over the year’s analysis have shown that grouper first starts their lives as females and then after breeding a few times they change their sex to male. Female groupers mature about 3 years, and can breed for up to 20 years. Also it has been found that St Helena has lower water temperatures than Ascension, therefore the population growth is slower on St Helena than it is here. Female grouper are usually bigger than the male.
Turtle tours can now be booked either at the Conservation Office on telephone number 6359, or via the Obsidian Hotel on 6246. You may also email us on the below email addresses:
Please be advised that due to on-going field work the Conservation Office will open from 7.30am -10am during week days. We open as normal on Saturdays, 10am-12noon, signs will be posted on the door when the office is closed.
Sorry for any inconvenience this may cause.
Volunteers welcome. Please contact Natasha Williams or Jolene Sim. Ascension Island Conservation Department. Georgetown. Tel: 6359. Email: email@example.com or firstname.lastname@example.org