1. Martín E. Hernández Rivas, Sylvia P. A. Jiménez Rosenberg, Alejandro Hinojosa Medina, Ricardo Saldierna Martínez y Gerardo Aceves Medina. CICIMAR-IPN mrivas@ipn.mx INSTITUTO POLITÉCNICO NACIONAL CENTRO INTERDISCIPLINARIO DE CIENCIAS MARINAS DEPARTAMENTO DE PLANCTON Y ECOLOGÍA MARINA

2. STUDY AREA Arriaga Cabrera, L., E. Vázquez Domínguez, J. González Cano, R. Jiménez Rosenberg, E. Muñoz López, V. Aguilar Sierra (coordinadores). 1998. Regiones marinas prioritarias de México. Comisión Nacional para el Conocimiento y uso de la Biodiversidad

3. STUDY AREA

4. MATERIAL AND METHODS The IMECOCAL program has conducted oceanographic expeditions every three months since 1997 to date with the aim to monitor the southern region of the California Current, by means of similar methodology to that implemented for the CALCOFI program. CTD, the CUFES system for fish eggs sampling, and Bongo and Calvet nets have been used as sampling devices. Fish larvae obtained with oblique bongo tows (60 cm diam. and 500  mesh), were separated and identified to the minimum possible taxon. The sardine larvae identified were grouped into four development stages, namely: preflexion, flexion, postflexion and transformation. The larval abundance was normalized to 10 m 2 sea surface and larval indexes were computed. The census estimations were adjusted to the area in order to prevent that the area factor would augment them.

5. RESULTS Distribution and Abundance of Sardinops sagax larvae 2003 is not included because the low numbers of larvae

6. Positive stations in Sebastián Vizcaíno Bay The red dot indicate only 3 sampled stations in this cruise

7. IMECOCAL INDEX, % POSITIVE STATIONS ONLY 3 STATIONS SAMPLED IN THIS CRUISE

8. IMECOCAL INDEX BY MONTH

9. R. Durazo, et al. 2005 TEMPERATURE

10. SALINITY

11. LARVAL INDEX BY CRUISE IN S. VIZCAÍNO BAY

12. CONCLUSIONS The tendency of de abundance of sardine larvae en Sebastián Vizaíno area is to decrease. The presence of larvae of temeprate stock was more abundant during all period. The larvae of cold stock was found in the spring IMECOCAL cruises, increased from April 1999 to April 2002, after that dissapear in the area. The IMECOCAL Index (N+/NT), in general decreased from August 1999 to October 2003.