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Gray Whale Abundance Increases for Second Year in 2012
The 2012 gray whale research team included Sergio MartĂnez A., Diana LĂłpez A., Tabata Olavarrieta G., Laura Rodriguez J., and Mauricio RodrĂguez A. They were joined in February by LSIESP Â co-director Dr. Steven Swartz, and assisted by Susana Tobar H., Flor VĂˇzquez, Claudia DĂaz, and Erandi CalderĂłn Y.
The team began abundance surveys on January 18th and continued until April 15th, effectively covering the entire winter gray whale occupation of the lagoon. These surveys revealed that, like the 2011 winter, the overall number of gray whales utilizing the lagoon was greater than was observed between 2007 and 2010. Â The greatest number of adult whales was counted on February 22nd and included 205 single adults and 63 female-calf pairs (Fig. 1).
As was seen in 2011, there was an increase in the number of mother-calf pairs late in the winter. The highest counts of these whales were 86 pairs on March 9th and a second high count of 110-pairs on April 7th (Fig. Â 2). This late season increase suggests that mother-calf pairs were entering Laguna San Ignacio from other calving areas in Baja California.
The late season gathering of females with their calves was originally documented during the 1978-1982 winters, but it was not seen in Laguna San Ignacio until 2011. The the comparison of photographs from Bahia Magdalena and Laguna San Ignacio will confirm if there is an exchange of gray whales between these two winter aggregation areas. Researchers also noted that the condition of the newborn calves looked very healthy, and very few â€śskinnyâ€ť whales were observed in 2012. This suggested that gray whales are continuing to recover from the nutritional stress that was observed following the range-wide die-off the 1998-2000.
Counts of single whales reached a maximum of 205 whales on February 22nd (Fig. 3). In recent years (2007-2010) most gray whales were distributed in the areas nearest to the lagoonâ€™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 and again in 2012 gray whales were distributed throughout the entire lagoon, resembling the distribution patterns observed during the 1978-1982 time period. It is not clear why more gray whales are now utilizing more of Laguna San Ignacio than during the previous decade.
The abundance if gray whales and the timing of their occupation of Laguna San Ignacio observed in 2011 and 2012 suggest that the whales are continuing to utilize this lagoon as a primary winter breeding and calving area each winter. The increase in the number of mother-calf pairs suggests that more female whales are utilizing the Laguna San Ignacio region as a winter aggregation area than during the 2007-2010 winters. Also, the increased counts of mother-calf pairs are occurring in late-March and early-April that include calves that are estimated from their size to be 1-2 months old. This suggests that female-calf pairs from other winter aggregating areas (e.g., Laguna Ojo de Liebre and Bahia Magdalena) are moving into Laguna San Ignacio late in the winter breeding season, a pattern seen during the 1977-1982 survey years, but not during the period from 1996-2010. Â LSIESP’s ongoing analysis and comparison of photographs from Bahia Magdalena and Ojo de Liebre Â with photographs obtained in Laguna San Ignacio will perhaps confirm this hypothesis.