Record high gray whale count found in Laguna San Ignacio in 2011
By Steven L. Swartz, Co-Director LSIESP
After four years (2007-2010) of declining counts of Eastern North Pacific gray whales within Laguna San Ignacio, Baja California, Sur, Mexico, the number of whales utilizing this lagoon during their 2011 winter breeding season was significantly higher than that seen in recent winters.
Weekly census counts of the number of whales in the lagoon began on 18 January 2011 and continued until April to document the number of whales utilizing the lagoon during the winter. Eastern North Pacific gray whales visit Laguna San Ignacio Lagoon each winter to mate and rear their newborn calves. Gray whales continued to enter the lagoon through January and February and counts of whales reached a maximum of 320 adult whales on 26 February, representing a 60% increase above the average high counts between 2007-2010 and approaching adult whales counts observed in the 1980’s
The number of single whales (whales not accompanied by calves) observed in 2011 reached its maximum of 261 whales on 26 February, and was similar to single whale counts obtained in the 1980’s . During the period from 2007-2011 single whales do appear to arrive and to leave the lagoon 7-10 days later than during the 1980’s, which corresponds to similar shifts in a later fall southward migration from the summer feeding grounds in the North Pacific and Arctic seas.
Of particular significance were the number of female whales with newborn calves utilizing the lagoon in 2011. From 2007 to 2010 between 20 and 40 mother-calf pairs were counted in Laguna San Ignacio, and numbers declined by April until no female-calf pairs remained in the lagoon. However, this winter the number of mother-calf pairs began to increase early in the winter season, continued to increase after the maximum adult counts in late February, and reached a maximum count of 133 mother-calf pairs on 28 March. This late-season increase after the birthing period suggests that mother-calf pairs from areas to the south of Laguna San Ignacio (e.g., Bahia Magdalena) were entering the lagoon late in the season, perhaps as they begin their northward migration to the summer feeding range. While the overall number of mother-calf pairs in 2011 is less than the numbers observed 30-years ago, this year’s counts represent a return to the previous pattern of late-season lagoon use by mother-calf pairs originally observed during the 1978-1982 studies conducted by Mary Lou Jones and Steven Swartz Preliminary discussions with the researchers that monitor gray whale abundance in the larger Laguna Ojo de Liebre to the north of Laguna San Ignacio indicate that similar increases in the number of whales, and mother-calf pairs also occurred in that lagoon during the 2011 winter.
In recent years (2007-2010) most gray whales were distributed in the areas nearest to the lagoon’s entrance and in the middle lagoon area, with few whales occupying the innermost northern areas of the lagoon furthest from the sea. However, in 2011 gray whales were distributed throughout the entire lagoon, again resembling the distribution patterns observed during the 1978-1982 time period.
It is not clear at this time why more gray whales utilized Laguna San Ignacio in 2011 than in previous years. In general water temperature was 16-17 degrees C during most of the winter, compared to 18-19 degrees C in a warm water year. These colder than the average temperatures or a “La Ninia” conditions, may have influenced the number of whales that entered and spent time in Laguna San Ignacio. Researchers also noted that the condition of the newborn calves looked very “fat”, with few “skinny” whales observed during the 2011 winter, which suggests that gray whales may be recovering from the nutritional stress that was observed following the range-wide die-off of 1998-2000.
Analysis of the 2011 census counts, photographic identification data, and environmental data from Laguna San Ignacio will continue during the next few months and results will be reported on the LSIESP web-site (www.lsiecosystem.org) as they become available.