FISHERY BULLETIN: VOL. 72. NO. 3 



the more coastal waters. Larvae that have 

 shifted into the countercurrents from the South 

 Equatorial Current in the eastern part of its 

 course may well be returned in time for 

 metamorphosis near the coast or at offshore is- 

 lands. It seems probable, however, that safe re- 

 turn from the area of the more westward sta- 

 tions surveyed is doubtful in view of the great 

 distance covered and the expected attrition 

 through predation, etc. Assuming, as before, 

 that the larvae occurring below about lat. 10°N 

 near long. 120°W, originated in the Galapagos 

 Islands area and allowing an average of 20 

 nautical miles per day westward flow of the 

 South Equatorial Current it would require 3 mo 

 sustained drift to cover the 1,800 nautical miles 

 involved. If shifted promptly at this point into 

 the North Equatorial Countercurrent with an 

 average speed of 15 nautical miles per day 

 another 4 mo of sustained transport would be 

 required to reach an adult area suitable for 

 metamorphosis. It should be noted, however, 

 that only larval stages VII to XI (final stage) 

 were taken at the more distant stations on all 

 skipjack cruises except David Starr Jordan 

 cruise 65, the one nearest to the Galapagos Is- 

 lands. This would indicate that even the 

 youngest larvae taken near long. 120°W were 

 probably older than 3 mo and the likelihood of 

 much additional delay in returning by way of 

 countercurrents militate against a safe return 

 unless metamorphosis can be delayed pending 

 encountering conditions favorable to metamor- 

 phosis and assumption of the benthic habit. Re- 

 cruitment must depend mainly on larvae that 

 have been retained relatively near the coast by 

 coastwise currents, eddies, and backwashes. 



None of the east Pacific larvae taken in the 

 far offshore areas show any tendency to gigan- 

 tism such as was believed to occur in some 

 Crustacea when settlement has been postponed 

 (Bruce, 1970). 



To what extent metamorphosis of the phyl- 

 losoma larvae to the postlarval stage may take 

 place in the far offshore waters is not known. 

 No palinurid postlarvae were found in any of 

 the cruises. However, a single specimen of Scyl- 

 larides astori postlarva (known as a nesto) was 

 taken in a trawl at lat. OriT'N, long. 120°06'W 

 during Townsend Cromwell cruise 51 (Johnson, 

 in press). 



The chances of the larvae continuing to float 

 successfully westward all the way to the 



mid-Pacific islands is unlikely and the absence 

 of the species, except for P. penicillatus , in these 

 islands substantiates this supposition and 

 clearly manifests the East Pacific Barrier func- 

 tioning against westward migration of the east 

 Pacific species. 



ACKNOWLEDGMENTS 



The plankton collections and field data were 

 kindly supplied to me by the coordinators of the 

 Skipjack Cruises, involving the Institute of 

 Marine Resources at Scripps Institution of 

 Oceanography (SIO) and the National Marine 

 Fisheries Service (NMFS), Southwest Fisheries 

 Center, La Jolla, Calif. The laboratory work 

 was supported by the Marine Life Research 

 Program, the SIO part of the California 

 Cooperative Oceanic Fisheries Investigation 

 sponsored by the Research Committee of the 

 State of California. Thanks are extended to 

 Mizuki Tsuchiya of SIO for discussions pertain- 

 ing to the hydrography and to Mary Farrel of 

 NMFS for aid in sorting some of the samples. 



LITERATURE CITED 



Bruce, A. J. 



1970. On the identity of Periclimenes pusillus Rathbun, 

 1906. (Decapoda, Pontoniinae). Crustaceana 19:306-310. 



Chace, F. a., Jr. 



1962. The non-brachyuran decapod crustaceans of Clip- 

 perton Island. Proc. U.S. Natl. Mus. 113:605-635. 

 Chittleborough, R. G., and L. R. Thomas. 



1969. Larval ecology of the western Australian crajrfish, 

 with notes upon other panulirid larvae from the east- 

 ern Indian Ocean. Aust. J. Mar. Freshwater Res. 

 20:199-223. 

 Garth, J. S. 



1966. On the oceanic transport of crab larval stages. In 

 Proceedings of the Symposium on Crustacea, Part 1, p. 

 443-448. Mar. Biol. Assoc. India, Symp. Ser. 2. 

 George, R. W. 



1969. Natural distribution and speciation of Marine ani- 

 mals. J. R. Soc. West. Aust. 52(2):33-40. 

 Johnson, M. W. 



1960. Production and distribution of larvae of the spiny 

 lobster, Panulirus interruptus (Randall) with records 

 on P. gracilis Streets. Bull. Scripps Inst. Oceanogr., 

 Univ. Calif 7:413-461. 



1971. The palinurid and scyllarid lobster larvae of the 

 tropical eastern Pacific and their distribution as re- 

 lated to the prevailing hydrography. Bull. Scripps Inst. 

 Oceanogr., Univ. Calif 19:1-36. 



In press. The postlarvae of Scyllarides astori and 

 Evibacus princeps of the Eastern Tropical Pacific 

 (Crustacea, Decapoda, Scyllaridae). Crustaceana. 



646 



