Benfield et al Growth and emigration of Pemeus indicus 



25 



Figure 4 



Mean carapace length oi Pcnai'us indicus cohorts in the St. Lucia 

 system over time; vertical bars indicate 1 standard deviation. I'pper 

 scales indicate corresponding mean temperatures and salinitie.s aver- 

 aged across sampling stations 1-7; vertical bars indicate maxima 

 and minima. 



Figure 6 



Cumulative length-freiiuency histogram of Penaews indicut: for beam 

 trawl (August 1982-November 1984) and bait fishery (September 

 1982-August 198.5) in the St. Lucia system. Plot truncated at 30 nmi 

 CL because larger size classes contributed < 0.2.5% of total catch. 



Figure 5 



Relationship between growth rates oi Penaeus indicus (7.25-17.66 

 mm CL) and corresponding mean water temperatures in the St. Lucia 

 system determined for consecutive sampling intervals. 



Figure 7 



Monthly frequency oi F-'uku-uk imliciis >20 mm CL in the baitllshery 

 catch in the St. Lucia system. Blank intervals indicate no data 

 available for that month. 



emigration of the third cohort would likely have coin- 

 cided with declining water temperatures if it had not 

 been forced by the cyclone. 



Discussion 



Estimation of growth rates and emigi-ation size depend 

 on a representative sample of the population at each 

 sampling interval. Trawl samplers typically have a low 

 catch efficiency (Zimmerman et al. 1984) and a selec- 

 tive bias towards certain size classes (Staples 1980). 

 Our beam trawl captured P. indicus over the range 



