DISPERSION AND DEVELOPMENT PATTERNS IN LARVAE OF NYCTIPHANES-SIMPLEX (EUOPAUSIACEA) IN THE UPWELLING REGION OFF BAJA-CALIFORNIA

Distribution of Nyctiphanes simplex larvae in relation to development stage and presence of fecund females is described for January-February , April, July and October 1966 in the area between Point Baja and Poin t Abreojos, off Baja California, Mexico. Recruitment was observed to b e year round, but most intensive in fall and winter. Largest aggregati ons of fecund females (>10 ind. m-2) occurred off Point Baja-Point Can oas in all months except July. Vizcaino Bay seems to be a feeding site in winter and a very important reproduction site in fall. Heating of waters offshore and the presence of a clockwise eddy inside Vizcaino B ay at the end of the most intensive months of upwelling constrained th e distribution of females. Although fewer spawning females (carrying e xternal eggs or spent) were present during winter, spring and summer, females in those seasons had greater body lengths (11.3, 12.4 and 11.6 mm on average respectively) than those during fall (10.1 mm on averag e). The largest spawning female (15.8 mm) was found in July off Point Eugenia. Proportions of particular furcilia forms in stages F1 to F2 ( distinguished by the degree of development of pleopods) were more simi lar along the north-south axis than onshore-offshore, following the ge nerally along-shore orientation of isotherms. Dominance of short devel opmental pathways in F1 and F2 stages (single instar in each stage) wa s most often observed near the shore, associated with isotherms of 17- degrees-C in winter and summer and with low temperatures in spring. El sewhere the dominant pathway for this species was 1 instar in F1 and 2 instars in F2. However, even the longest pathways were sometimes asso ciated with stations near the coast. Greatest body lengths, especially in late furcilia stages, were found at stations where developmental p athways were generally short, while smaller larvae (in equivalent stag es) were associated with longer pathways.