2018 gray whale abundance in Laguna San Ignacio and Bahia Magdalena, Mexico
J. Urban R., S. L. Swartz, S. Martinez A., L. Viloria G., and A. Gomez-Gallardo U.
International Whaling Commission
The 2018 winter gray whale abundance in Laguna San Ignacio (LSI) and Bahía Magdalena lagoon complex (BM) was characterized by numbers of single adult breeding whales similar to that observed in recent years, but numbers of female-calf pairs were lower than expected compared to previous winters, and they departed from the lagoon early. Boat surveys were conducted as previous years. In LSI 13 surveys began on 18 January and continued until 2 April. The counts of single adult whales (breeding males and females without calves) reached a maximum of 160 whales on 15 February, which was greater and occurred earlier in the season than the 120 single whales seen on 3 March 2017, but less than the 213 single whales observed on 12 February 2016. The number of female-calf pairs seen in 2018 was far less than that observed in 2017 (107 pairs) and in 2016 (124 pairs). In BM the highest numbers of gray whale females with calves were consistently observed in the Canal de Santo Domingo: 3-pairs on 13 January; 9-pairs on 7 February; and 16 pairs on 7 March. Although the number of female-calf pairs in the Canal de Santo Domingo was noticeably less than were observed in this area in 2017 and 2016. The abundance of female-calf was lower than expected, and similar to the abundance observed during the winter breeding seasons from 2007 to 2010 following the range-wide “mortality event” in the late 1990’s. However, the whales appeared to be in good nutritional health, and any indication of nutritional stress or poor condition of the gray whales was not evident.