Bionomics of Penaeus vannamei boone and Penaeus stylirostris stimpson in a lagoon on the Mexican Pacific Coast

Abstract

Lagoon populations of Penaeus vannamei and P. stylirostris were sampled by cast-nets and a 2 m beam trawl twice a month from March 1974 until December 1975. Conversion factors between total length/carapace length, total weight/carapace length, tail weight/carapace length, tail weight/total length and tail weight/total weight were calculated for both species. The relation of dry weight to wet weight is given for P. vannamei only. Mean monthly growth rates, determined from length-frequency distributions, ranged from 0·02 mm increase in carapace length per day (mm c.l. d−d) in March to 0·44 mm c.l. d−1 in September for P. vannamei. The growth rate of P. stylirostris ranged between 0·03 mm c.l. d−1 in April and 0·64 mm c.l. d−1 in August. P. vannamei grew faster in 1975 than in 1974 and the difference is thought to be related to rainfall. Both species grew slower in the winter dry season (November-May) than in the summer wet season (June-October). Patterns of immigration and emigration are discussed.