Abstract
The spiny lobsters are caught at Mutwal by bottom set gillnets operated by 17'-22' mechanised fibre reinforced plastic (FRP) boats and non- mechanised canoes and wooden crafts (theppam). The mesh sizes of these nets vary from 90 mm to 180 mm. The mean catch per unit effort (CPUE) of mechanised boats was found to be higher than those of non-mechanised crafts. The mean CPUE of FRP boats, canoes and wooden crafts showed a ratio of 4:2:1. Production was found to be higher during the inter-monsoon period than during the monsoon period. The sex ratio appears to be approximately 1:l. The percentage of ovigerous females is higher just before and after the monsoon period. The calculated natural and total mortality coefficients were I.04 and 1.08 respectively giving an exploitation rate of 0.04. Spiny lobsters (Family - Palinuridae) are widely distributed in the Indian Ocean. These are the most valuable of the crustaceans in wziters around Sri Lanka, India, Malaysia, South Africa and many other regions. This fishery is very important to Sri Lanka as it is a very good export earner. Spiny lobsters are exported mainly to Japan, France and the U.S.A. Six species of spiny lobsters have been recorded from Sri Lankan waters4 Out of these Panulirus hoinarus (Linnaeus), P. ornatus (Fabricius), P. ver- sicolor (Latrielle) and P. peizicilliatus (Olivier) are caught off the waters at Mutwal. P. homarus forms the major constituent. The biology and the fishery of spiny lobsters have been described from many parts of the world as for exam le from haila and, ~ritain,'~ USA? Australia,13 yemen'' and Sri LanI~a.',~.~~De Bruin studied the capture methods, ecology and distribution while Jayakody & Kensler described the fishery in the Southern coast of Sri Lanka. The present study deals with the fishery and some biological aspects such as sex ratio and population parameters such as asymptotic length (LQ), growth constant (K.), total mortality (Z), natural mortality (M) and the explo~tation rate (E) of P. homarus population from Mutwal, with the aim of understanding the status of the fishery of this stock of P. homarus.
Highlights
Spiny lobsters (Family - Palinuridae) are widely distributed in the IndianOcean
These are operated in the same area by 17'-22' fibre reinforced plastic (FRP) boats powered by 6-25 HP out-board engines and non-mechanised canoes and wooden crafts made out of logs which are tied together
Of the four species of spiny lobsters caught at Mutwal P. homarus contributed to 92% of the total lobster landings during the study period (Table 1)
Summary
India, Malaysia, South Africa and many other regions. This fishery is very important to Sri Lanka as it is a very good export earner. The biology and the fishery of spiny lobsters have been described from many parts of the world as for exam le from haila and," ~ ritain ,USA?. Bruin studied the capture methods, ecology and distribution while Jayakody & Kensler described the fishery in the Southern coast of Sri Lanka. The present study deals with the fishery and some biological aspects such as sex ratio and population parameters such as asymptotic length (LQ), growth constant (K.), total mortality (Z), natural mortality (M) and the explo~tationrate (E) of P. homarus population from Mutwal, with the aim of understanding the status of the fishery of this stock of P. homarus
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