Sarda et al.: Spatio-temporal structure of a population of Aristeus antennatus 



605 



Figure 6 



Conceptual model of the spatio-temporal dy- 

 namics of Aristeus antennatus in the study area 

 (see text for more details). MS=middle slope; 

 US=upper slope, and LS=lower slope; circle= 

 spring; square=summer; triangle=autumn; 

 diamond=winter. 



Jan. 



Feb. 

 Mar 



Apr 



May 



Jun 



Jul 



Aug. 



Sep. 



Oct. 

 Nov. 



Dec J 



canyon 



middle 

 slope 



canyon 



) 20 30 40 50 60 

 CL, mm 



Figure 7 



Monthly size frequencies for rose shrimp, Aristeus 

 antennatus (carapace length) taken in commercial 

 catches from the upper slope (US) and middle slope 

 (MS) (data from Demestre, 1990). 



that observed for A. antennatus. Size-frequency 

 modes were evident in spring and summer but did 

 not progress in autumn and winter (Fig. 6). Sparre et 

 al. (1989) advised using the annual-return matched 

 sample method to estimate growth parameters in such 

 cases. Failing to take these aspects into account when 

 considering a population exploited by a given fleet 

 in a given area may lead to errors in calculating bio- 

 logical parameters and, consequently, in decision- 

 making for fishery management. 



Acknowledgments 



We thank J. B. Company for his assistance in col- 

 lecting the samples and G. Fuster and J. M. Anguita 

 for our technical assistance. We also wish to express 

 their appreciation to all the team members who par- 

 ticipated in the MAR90/757 project, funded by the 

 Spanish Ministry of Education and Science (CICYT). 

 W. Norbis was supported by a doctoral grant from the 

 Agencia Espanola de Cooperacion Internacional del 

 Ministerio de Asuntos Exteriores. R. Sacks prepared 

 the English translation. 



