Resumen del producto

As opposite to other migratory mysticetes, blue whales (Balaenoptera musculus) feed continuously during their wintering permanence at low and middle latitudes, in this case, the Gulf of California. Their feeding requirements are based almost exclusively on the euphausiid Nictiphanes simplex, which implies that the whales distribution within the Gulf is intimately related to the persistence of some environmental processes that produce blooms of primary producers capable of sustaining large aggregations of krill. The southwestern Gulf of California is one the most important habitats used by the blue whale, both for breeding and feeding purposes. Here, we analyzed the spatial seasonality of this environment by extracting seasonal harmonics to the sea surface wind, sea surface temperature, and sea surface chlorophyll-a trough a series of least-squares regressions, spanning the period 1998-2008. These models were compared to the spatial distribution of blue whales between 2002 and 2007. We also analyzed available hydrographic data from Bay of La Paz, parallel to blue whale population density estimations. Although Loreto is the richer area during most of the wintering period, La Paz presents a local high peak of chlorophyll-a and low temperatures at the end of the wintering season, when the rest of the southwestern Gulf, including Loreto, is more oligotrophic and warmer. The biological richness around Loreto corresponds to a generalized coastal high along the entire southwestern Gulf, influenced by the dominant wind monsoonal regime, whereas the peak at the end of the wintering season around La Paz responds to a local phenomenon, possibly a persistent cyclonic circulation. These conditions coincide with an increment in blue whale abundance in Bay of La Paz at the end of the wintering season. Thus, the environmental seasonality of southwestern Gulf suggests the relevance of Bay of La Paz as a temporal habitat for the aggregation of blue whales, prior to their migration to the north. Therefore, we encourage to include this area in further management decisions for the conservation of the species, especially those regarding to boat traffic and whale watching activities.

Palabras clave: Ballena azul; distribución vertical; alarma de tsunami

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