Lovrich and Vlnuesa Reproduction of Paralomis granulosa 



665 



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68° 67°30 



ISLA GRANDE DE 



T1ERRA DEL FUEGO 



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66° 30 



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68°30 



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Figure 1 



Location of sampling area. 



Channel is an elongate glacial valley which stretches 

 east-west, extending between the Isla Grande de Tierra 

 del Fuego, and Navarino and Hoste Islands (Rabassa 

 et al, 1986). It is 210 km long and on average 4 km 

 wide and has a maximum depth of 160 m. Surface sea- 

 water temperatures range from 4.2 to 4.3°C in August 

 and from 8.9 to 9.8°C in January; the annual mean 

 temperature varies from 6.5 to 6.8°C. Salinity ranges 

 from 26.Th in November-December to 31.3%c during 

 July and is highly variable during October and No- 

 vember because of ice melt. 



Monthly samples were obtained from commercial 

 catches from January 1989 to December 1990. Crabs 

 were captured in traps deployed on bottom lines with 

 10 traps each. Traps were fished for 48 hours and 

 usually baited with chicken, fish, horse, pig, cow, or 

 lamb meat and bones. Each month 30-40 females and 

 10 males were randomly selected from the catch of a 

 single line, placed in tanks with circulating seawater 

 and transported alive to the laboratory. Carapace length 

 (CL, midline distance between posterior orbital mar- 

 gin, excluding the rostral spine, and the posterior me- 

 dian margin) and right chela height (CH, measured at 

 the anterior dorsal margin of the propodus, between 

 the two anterior spines) of each crab were measured 

 to the nearest 0.1 mm with a vernier caliper. Live body 

 weight was measured to the nearest 0.01 g. The cara- 



pace of each crab was aged according to the following 

 subjective scale: 



1 Postmolt (POM): Shell soft, bright red, membra- 

 nous and non-calcified, without epibiota. 



2 Early Intermolt (EIM): Shell hard but brittle, 

 bright red, without epibiota. 



3 Median Intermolt (MIM): Shell hard, red to 

 brown, variably covered with epibiota such as serpulids. 



4 Advanced Intermolt (AIM): Shell hard, dark 

 red, with numerous epibionts including balanids 

 (6-8 mm maximum basal diameter), bivalves (Mytilus 

 edulis, Aulacomya ater, 4-6 mm length), serpulids, and 

 other calcareous polychaetes, bryozoans, and brown 

 algae. 



5 Premolt (PRM): Similar to AIM but the old 

 shell is partially raised, revealing the new shell. 



For both sexes, we used two methods to determine 

 the size at which 50% of individuals were mature: 



• Analysis of reproductive features. Females were con- 

 sidered to be mature if they had eggs or empty egg 

 cases attached to the pleopods; males were considered 

 to be mature if spermatophores were found in their 

 vas deferens. The proportion of mature individuals was 

 calculated for each 5-mm-CL interval and a logistic 

 function was adjusted to provide 50% maturity. 



• Allometric growth of the right chela. This method is 

 based on the relative change in chela height at sexual 



