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19180
Open
SC/68C/CMP/12
Gray whale's body condition in Laguna San Ignacio, BCS, Mexico, during 2021 breeding season
F. Ronz?n-Contreras, S. Mart?nez-Aguilar, S. Swartz and J. Urb?n R.
IWC
2021
Gray whale (Eschrichtius robustus) population feeds during the summer in the Bering, Chukchi,and Beaufort seas. Itmigrates to winter breeding and calving grounds along the Pacific coast of Baja California, in Mexico. The assessment of gray whale body condition upon their arrival at the breeding grounds provides an indicator of the whales' "health and reproductive condition." Itindirectly is an indicator of the health of the environment. Gray whales were photographed (n=615) to evaluate body condition in Laguna San Ignacio (LSI) in Baja California Sur in 2021. Photographs were sorted into two reproductive-sex categories: Females with calvesand Single whales (males and females without a calf). The condition of each whale was scored as "good", "fair", or "poor"using a numerical methoddeveloped for the Western North Pacific (WNP) gray whales. In 2021 the proportion of females with calves in “good condition” was 95.3% (n=41); “fair” 4.6% (n=2) and "poor" 0%. The proportion of single whales with “good,” "fair", and "poor" condition was 42.1%(n=259), 33.5%(n=206), and 24.4%(n=150), respectively. Compared to previous years, the proportion of females with calves increase during 2021. For single whales, the body conditionis very similar toprevious years(2018-2020). However,females' body conditionwith calves was not reflected in the individuals'photo-identified in 2021(n=43), compared to the average (n= 226) pairs photo-identified each year from 2011 to 2017. The proportionof single whales with "poor"body condition in 2021is the second-highest LSI observed. We conclude that all whales' body conditionwas probably similarly affected; however, comparison and correlation with environmental data from the feeding groundsand others breeding zonesis needed to understand the factors that contribute to the whales'body and reproductive condition.
