Growth of juvenile lobster-krill Munida gregaria (Decapoda, Galatheidae) in the San Jorge Gulf, Argentina

VARISCO MARTIN; VINUESA JULIO

Quingdao

Congreso; Seventh International Crustaceans Congress; 2011

Chinese Crustacean Society

The lobster-krill or squat lobster Munida gregaria (Fabricius, 1793) is one of the most abundant decapod in the benthic-demersal community of the San Jorge Gulf. The species has a key trophic role in this community because it is prey of several commercially important species of fish and shellfish. This paper analyzes the growth and moulting of juvenile M. gregaria in its first year of postlarval life. Juveniles were collected between January and December 2009. They were sampled using a plankton net, a bottom trawl net of 10 mm mesh and also by direct collection at rockpools in intertidal. A subsample was used to determine the stage of the moulting cycle and the rest of the sample was frozen. Carapace length was recorded in all lobsters from posterior orbital margin to the posterior median margin of the carapace. Moulting was assessed by epidermal changes at the distal end of the uropods. Growth parameters were estimated by length frequency distribution with 0.5 mm length interval of carapace using Pauly equation. The first postlarval instar was observed during November and lobsters grow significantly during the summer and fall. During winter and spring juveniles did not show significant increases in size. A large variability in the phases of the moult cycle was observed; so, moulting periods could not be delimited. This might be related to a high frequency of moulting, which is characteristic of many juvenile decapods. The smaller increase in size observed during winter and spring is consistent with the high frequency of individuals in intermolt and the occurrence of small ovigerous females between September and November. The investment in reproductive function has a detrimental effect on growth.The allocation of resources to gametogenesis results in a decrease in investment in growth. Size distribution in the analyzed months is unimodal. Data show that female M. gregaria in the San Jorge Gulf attain sexual maturity at approximately 9 ? 12 mm CL. So, can reproduce effectively during its first year of life.