Resumen del producto

The Eastern North Pacific (ENP) blue whale population is considered the most recoveredworldwide. Despite this, its subspecies taxonomy is yet to be resolved. A previous morphologicalanalysis using vertical aerial photogrammetry on blue whales from the ENP suggested thatthey are morphologically similar to the Indian Ocean pygmy blue whale Balaenoptera musculusbrevicauda. This subspecies has been discriminated from the Antarctic blue whale B. musculusintermedia by a shorter total length and a proportionally shorter caudal peduncle (from dorsal finto notch of flukes), a difficult morphological characteristic to measure at sea. In this study, we presentallometric and morphometric analyses of the caudal peduncle proportion in relation to totallength based on photogrammetric data from whales observed in the Gulf of California, Mexico (awinter ground for the ENP population), to compare with caudal peduncle measurements availablefrom both Southern Hemisphere subspecies. Throughout allometric analysis, the caudal peduncleshowed negative growth as the individual got older, indicating that this body part differs accordingto age-class. Our morphometric analysis indicated that the caudal peduncle proportion ofthese blue whales was significantly larger than that of the Indian Ocean pygmy blue whale. Theintegration of our results with the previous photogrammetry study suggests that more than onemorphotype inhabits the ENP, and highlights gaps in our knowledge on the taxonomy of thesewhales. The inexpensive photogrammetric technique used in this study could be easily combinedwith other studies to better understand and protect these endangered whale populations.

Palabras clave: Balaenoptera musculus; Morphometry; Allometry; Aerial photogrammetry; Subspecies

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