A new study has revealed that a collapse in the jumbo squid population in the Gulf of California has resulted in the departure of one of the area's most significant species: the sperm whale.
The decline of both species is attributed to environmental changes, including sustained ocean warming and intensified El Niño events, which have shifted the ecosystem dynamics in the sea between the Baja California peninsula and the Mexican mainland.
Jumbo squid (Dosidicus gigas) have been particularly affected by these changes, but as their numbers have dwindled so too have those of the sperm whales, which rely on the squid as their primary food source.
The study – led by researchers Héctor Pérez-Puig and Alejandro Arias Del Razo – was conducted over a nine-year period in the eastern Midriff Islands Region of the Gulf of California, and involved the use of extensive survey data and photo-identification techniques to record sperm whale populations.
Between 2009 and 2015, the population of sperm whales in the central Gulf of California ranged from 20 and 167 individuals, with a total 'super population' (a theoretical infinite population) of 354 whales. However, from 2016 to 2018, there were no sperm whale sightings at all.
This decline correlates with the collapse of the jumbo squid population, indicating that as squid numbers dwindled, sperm whales left the region.
The implications of this shift are stark, says Pérez-Puig, who explains that, as apex predators, sperm whales play a crucial role in controlling energy flow within marine ecosystems.
"The departure of sperm whales from the Gulf of California serves as a sentinel signal, reflecting significant shifts in marine ecosystems," says Pérez-Puig. "As the environment changes, so too does the delicate balance between predators and prey."
The researchers say that more detailed analysis to fully understand the movements of sperm whales and their prey is required, particularly in light of the ongoing 'tropicalisation' of the Gulf of California.
Find out more about the study: The departure of sperm whales (Physeter macrocephalus) in response to the declining jumbo squid (Dosidicus gigas) population in the central portion of the Gulf of California, published in PeerJ Life and Environment.
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