Oceanographic Observations in Monterey Bay, California, January 1972 to April 1973: Annual Report, Part 3, 1973

This report completes the hydrographic data series obtained during 27 monthly oceanographic cruises in Monterey Bay. This oceanographic study was initiated under a grant from the Office of Sea Grant Programs, and the data collection began in February 1971. In September 1971 additional funding was received from the Association of Monterey Bay Area Governments. The data obtained during 1971 have been published previously (Broenkow 1972), and some initial interpretation of this work has been reported by Smethie (1973), Broenkow and Smethie (1973), and Oceanographic Services, Inc. (1973). (PDF contains 336 pages)

Northern range extension, abundance and distribution of Pacific coastal Bottlenose doplhins (Tursiops truncatus gilli) in Monterey Bay, California

Pacific coastal bottlenose dolphins (Tursiops truncatus gilli) have apparently moved to Monterey Bay as a result of a shift north of their known range. Between 1983 and 1993, 417 sightings were reported off central California. Eighty-four boat-based surveys, between October 1990 and November 1993, resulted in the photo-identification of 68 uniquely marked individuals. School size ranged between 2 and 35 animals (mean = 16.60, S.D. = 7.72). Forty-three (63%) of the dolphins identified were previously photographed in the Southern California Bight before 1989. Jolly-Seber population estimates indicated an increase in the Monterey Bay population from 1990 to 1993. At least 13 of the photo-identified dolphins were present in Monterey Bay throughout the study period. All but two of the calculated coefficients of association were 0.35, indicating a strong bond among resident animals. The occurrence of an El Niño from January 1992 to the end of 1993 may have affected the number of animals present in the bay: mean school size was significantly greater during El Niño.

In utero domoic acid toxicity: a fetal basis to adult disease in the California sea lion (Zalophus californianus)

California sea lions have been a repeated subject of investigation for early life toxicity, which has been documented to occur with increasing frequency from late February through mid-May in association with organochlorine (PCB and DDT) poisoning and infectious disease in the 1970's and domoic acid poisoning in the last decade. The mass early life mortality events result from the concentrated breeding grounds and synchronization of reproduction over a 28 day post partum estrus cycle and 11 month in utero phase. This physiological synchronization is triggered by a decreasing photoperiod of 11.48 h/day that occurs approximately 90 days after conception at the major California breeding grounds. The photoperiod trigger activates implantation of embryos to proceed with development for the next 242 days until birth. Embryonic diapause is a selectable trait thought to optimize timing for food utilization and male migratory patterns; yet from the toxicological perspective presented here also serves to synchronize developmental toxicity of pulsed environmental events such as domoic acid poisoning. Research studies in laboratory animals have defined age-dependent neurotoxic effects during development and windows of susceptibility to domoic acid exposure. This review will evaluate experimental domoic acid neurotoxicity in developing rodents and, aided by comparative allometric projections, will analyze potential prenatal toxicity and exposure susceptibility in the California sea lion. This analysis should provide a useful tool to forecast fetal toxicity and understand the impact of fetal toxicity on adult disease of the California sea lion.