Laguna San Ignacio Ecosystem Science Program (LSIESP) Gray Whale Research & Monitoring Summary Report – 2008
The 2008 winter field season at Laguna San Ignacio started with very cold water in January and February. The research team fro the Autonomous University of Baja California Sur (UABCS) arrived at Laguna San Ignacio the third week in January and began surveys to document the number of gray whales in the lagoon. Surveys during the first four weeks documented the lowest numbers of gray whales, particularly mothers with calves, ever recorded in Laguna San Ignacio during the whales’ winter breeding season. By mid-February reports were received from vessels traveling along the Pacific coast of Baja that gray whales were observed gathering in Toto Santos Bay off Ensenada and outside of the Cedres and Benitos islands. Gray whales were also being seen off Cabo San Lucas at the southern tip of the Baja peninsula (south of Laguna San Ignacio) and well into the Gulf of California as far north as Loreto.
The water temperature inside Laguna San Ignacio and immediately offshore during this time hovered around 15 degrees C, suggesting a colder than normal or “La Nina” oceanographic condition along the Baja peninsula. The last two weeks of February the water temperature increased to 18-19 degrees C, and whale surveys within the lagoon documented an increase in the number of whales comparable to those observed in recent years. We surmised at this point that the low whale counts and reports of significant numbers of whales outside of the lagoon were related to the prevailing colder water during the first half of the winter season. We know that the gray whales’ winter distribution along the Baja California coast and in the Gulf of California is influenced by water temperature, with the whales moving further south and into the Gulf of California during cold water years.
The winter field season was completed the first week in April. In May several members of the LSIESP attended the Mexican Marine Mammal Society (SOMEMMA) conference in Ensenada and presented papers and posters on their research. In June Jorge Urban attended the International Whaling Commission’s Scientific Committee meeting in Chile and presented papers on gray whales in Laguna San Ignacio. Analysis of the 2008 winter field work will continue through the 2008 summer.
Gray Whale Monitoring & Assessment: The gray whale team was led by Co-PIs, Dr. Jorge Urban R. from the Autonomous University of Baja California Sur (UABCS) in La Paz, Steven Swartz of Cetacean Research Associates, Maryland USA, and included four UABCS graduate students (Alejandro Gómez-Gallardo U., Sergio González C., Benjamín Troyo V., and Mauricio Nájera C.) and two volunteers (Anaid López U. of UABCS and Angie Sremba of Oregon State University). The team arrived at Laguna San Ignacio the third week in January, and completed 14 surveys of the number of gray whales in the lagoon by the end of the 2008 winter season in early April. This completes a 30-year series of census surveys that began in 1978, the longest such series for any of the gray whale breeding lagoons in Baja California. Surveys during the first four weeks of 2008 documented the lowest numbers of gray whales, particularly mothers with calves, ever recorded in Laguna San Ignacio during the whales’ winter breeding season. Gray whale photographic identification studies documented the presence of individual whales, particularly females with calves, within the lagoon’s interior. Approximately 250 individual whales were identified from photographs. Analysis will continue through June 2008 to identify individual whales and calves of the year. Final analyses will determine annual return rates for individual whales, minimum duration of stay in the lagoon, calving frequency, intervals, and rates for known females, and allow detection and evaluation of any “skinny” or resource compromised individuals.