MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(OGL-1117-844371) An in situ evaluation of the effects of dredge-related activity on Pacific herring (Clupea pallasi) embryo development.

Jahn, A¹, Ogle, R², Salinas, E², Pincetich, C², Bradley, J², ¹ Port of Oakland, Oakland, CA, USA² Pacific EcoRisk, Martinez, CA, USA

ABSTRACT- Pacific herring (Clupea pallasi) support an important fishery in San Francisco Bay (SFBay). Because of their economic and recreational value, there are significant management efforts in place to maintain the health and abundance of the SFBay herring population. Due to concerns about the potential effects of dredging activities on herring reproduction, California Department of Fish and Game has placed seasonal restrictions on these activities. However, there have been no previous scientific investigations aimed at evaluating the effect of dredging-related activity on any aspect of Pacific herring reproduction; thus it is uncertain whether or not these restrictions are indeed necessary to maintain the health and well-being of the herring population. The present study was intended to begin to provide the necessary data with which to assess whether or not dredging activities affect Pacific herring success in SFBay. The performance of a routine maintenance dredging project during March, 2005, presented a unique opportunity to assess the effects of dredging-related stressors on Pacific herring embryo development under real-world conditions. Herring embryos (<24-hr old) were outplanted on horizontally- and vertically-oriented glass slides in in situ exposure chambers along a distance gradient from an active dredging project. After approximately 4 days exposure, the embryos were recovered from the field and allowed to continue development to hatching in the laboratory. Normal development and hatching success were evaluated. Qualitative examination of the slides confirmed some degree of siltation on the outplanted embryos, being markedly more pronounced for the horizontally-oriented slides. There were no significant differences in normal development between the Control treatments and outplanted embryos for either vertical or horizontal orientation. Hatching success was not affected on vertically-oriented slides; however, decreased hatching success was observed for some of the outplanted embryos on the horizontally-oriented slides.

Key words: Pacific herring, in situ, dredging, embryo/larval