EFFECTS OF SALINITY ON SPERM MOTILITY, FERTILIZATION, AND DEVELOPMENTIN THE PACIFIC HERRING, CLUPEA-PALLASI

We investigated the effects of salinity on fertilization and early dev elopment in a population of Pacific herring, Clupea pallasi, that migr ate from oceanic waters into the San Francisco Bay estuary to spawn. T he salinity range for fertilization fell between 8 and 28 ppt, with an optimal range of about 12 to 24 ppt. In comparison, the range for a p opulation of C. harengus membras (Airisto Sound, Finland) that reside year-round in the Baltic Sea was 4 to 24 ppt. Roles for both Na+ and K + were indicated in C. pallasi fertilization since increasing Na+ in t he presence of 10 mM K+ (concentration of seawater) mimicked the effec ts of increased overall salinity, whereas reduced effects were obtaine d if [K+] was held at 5 mM (that of half-strength seawater). The initi ation of C. pallasi sperm motility by components of the egg chorion, a prerequisite for fertilization, was inhibited at both elevated (28 an d 32 ppt) and reduced (4 and 8 ppt) salinities. Embryonic development through larval hatching in C. pallasi exhibited a salinity tolerance s imilar to that of fertilization; optimum development was obtained at s alinities between 8 and 24 ppt. A comparison of developmental progress ion in 3.5, 14, and 28 ppt seawater revealed that salinity effects bec ame evident during the post-gastrulation stages of development and tha t progression to hatching was delayed in both the lower and higher sal inities for those embryos that completed development.