Podest^: Migratory pattern of Merluccius hubbsi 



175 



exhibit a ubiquitous spawning strategy throughout the 

 shelf and, therefore, do not appear to be dependent on 

 larval drift and retention conditions. A possible excep- 

 tion is the shelfbreak area: despite its importance in 

 supporting abundant forage supplies, this area is not 

 a suitable spawning location. Eggs and larvae spawned 

 along the shelfbreak would most likely be carried 

 offshore. 



The circulation pattern of the Argentine shelf, as it 

 contributes to larval drift or retention, has not been 

 described in adequate detail. Circulation gyres or topo- 

 graphical features that may contribute to the separa- 

 tion of hake spawning groups on the Argentine shelf 

 are not apparent. If different spawning groups exist, 

 the specificity of their place and time of spawning or, 

 equivalently, the degree of mixing among them, re- 

 mains unclear. 



This work identified apparent differences in the 

 migratory pattern of hake between 1978 and 1979, 

 which were tied to the location of the confluence of the 

 Brazil and Malvinas currents along the shelllireak. Sosa 

 et al. (1976) mention 60-100 mile changes in Argen- 

 tine hake distribution associated with wind-induced 

 short-term fluctuations in the position of the conflu- 

 ence. Repeated monitoring of the confluence location 

 through satellite imagery (cf. Olson et al. 1988) would 

 make it possible to further investigate this association. 



In summary, the cyclic migration of commercial den- 

 sities of Argentine hake was roughly described using 

 data from commercial fishing operations. The migra- 

 tory pattern has evolved to maximize the chances of 

 successful spawning, while ensuring an adequate food 

 supply. During their migi-atory cycle, hake take advan- 

 tage of productive ocean features. 



A number of issues remain unclear, such as the ex- 

 istence of different spawning groups and the degree 

 of mixing among them. There is little information on 

 the recruitment variability in Argentine hake, so one 

 cannot speculate on the relationship between migi'atory 

 pattern and recruitment success. The circulation on the 

 Argentine shelf and its influence on larval drift or 

 retention requires much study. Finally, the continued 

 availability of prey for hake larvae throughout the sum- 

 mer in the tidal-fronts environment (which would lead 

 to the bulk of spawning taking place there) needs to 

 be confirmed. 



Acknowledgments 



Comments by F. Williams, N. Ehrhardt, D. Olson, 

 J. Powers, and three anonymous reviewers are ap- 

 preciated. Support was provided by the Office of Naval 

 Research and by a National Research Council Research 

 Associateship at NASA's Goddard Space Flight 

 Center. Data from the Argentine fishing fleet were 



supplied by Subsecretan'a de Pesca, Buenos Aires, 

 Argentina. The Shinkai Maru and Walther Herwig 

 data were provided by Institute Nacional de Investiga- 

 cion y Desarrollo Pesquero, Mar del Plata, Argentina. 

 Travel to compile the data was funded by the Tinker 

 Center of the University of Miami. 



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