Photo: Stockfile/FIS

The decline of the giant squid population in the Gulf of California

MEXICO
Thursday, October 10, 2024, 00:10 (GMT + 9)

Sperm whale departure linked to decline in jumbo squid population in Gulf of California

A PeerJ study has revealed a significant departure of sperm whales (Physeter macrocephalus) from the central portion of the Gulf of California, is linked to the collapse of the jumbo squid (Dosidicus gigas) population, their primary prey.

The study, led by researchers Msc. Héctor Pérez-Puig and Dr. Alejandro Arias Del Razo, offers insight into the relationship between apex marine predators and their environment, highlighting sperm whales as key indicators of oceanic health.

Location of the eastern Midriff Islands Region and the central coast of Sonora in the Gulf of California. Survey area around the eastern Midriff Island Region of the Gulf of California. Base map obtained from GADM (https://gadm.org/, 2024).

The research, conducted over a 9-year period in the eastern Midriff Islands Region of the Gulf of California, utilized extensive survey data and photo-identification techniques to track sperm whale populations. Findings indicate a striking correlation between the decline of jumbo squid and the disappearance of sperm whales from the region, with no sightings recorded from 2016 to 2018.

Key findings:

• Population decline: Between 2009 and 2015, the population of sperm whales in the central Gulf of California ranged between 20 and 167 individuals, with a total "super population" of 354 whales. However, from 2016 to 2018, sperm whale sightings ceased entirely.
• Impact of jumbo squid collapse: General additive models show a positive relationship (R2 = 0.644) between sperm whale sightings and jumbo squid landings, indicating that as squid populations dwindled, sperm whales left the region.
• Environmental drivers: 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 Gulf of California. The jumbo squid population has been particularly affected, showing a shift to smaller phenotypes, which may no longer sustain larger predators like sperm whales.

Squid landings in the waters off the state of Sonora (CONAPESCA, 2018), sperm whale sightings in the eastern Midriff Islands Region, and hours of survey effort.

Ecosystem implications

Sperm whales, as apex predators, play a crucial role in controlling energy flow within marine ecosystems. Their departure from the Gulf of California suggests broader ecosystem changes and raises concerns about the long-term health of the region. The study underscores the importance of long-term data collection in understanding population trends and the effects of climate change on marine species.

Lead author Héctor Pérez-Puig emphasized the broader ecological implications of the findings, "The departure of sperm whales from the Gulf of California serves as a sentinel signal, reflecting significant shifts in marine ecosystems. As the environment changes, so too does the delicate balance between predators and prey."

The study calls for more detailed analysis to fully understand the movements of sperm whales and their prey, particularly in light of the ongoing "tropicalization" of the Gulf of California. Researchers recommend continued monitoring to assess the impact of environmental changes on marine species and the overall health of the ecosystem.

This research offers a vital contribution to the field of marine biology and ecology, with implications for the conservation of both sperm whales and the larger marine environment in the Gulf of California.

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