Got Squid? Changes in the Ecological State of the Gulf of California Since the 1940 Steinbeck-Ricketts Expedition with a Focus on Humboldt Squid

Abstract

Got Squid? Changes in the Ecological State of the Gulf of California Since the 1940 Steinbeck-Ricketts Expedition with a Focus on Humboldt Squid W. F. Gilly (bio), Unai Markaida (bio), Carlos Robinson (bio), and Bilin Liu (bio) Introduction Although the exact number of invertebrate species collected by Steinbeck and Ricketts in conjunction with the 1940 Sea of Cortez expedition on the Western Flyer is uncertain (Brusca, this volume), it is clear that the number of cephalopod species observed was small—fewer than 1% of the species collected. In particular, Dosidicus gigas, the Humboldt or jumbo flying squid, was apparently not seen during the expedition. This stands in contrast to the remarkable ease with which this species was observed north of Santa Rosalía in the Guaymas Basin region of the Gulf of California during a 2004 retracing of the 1940 expedition during the same time of year and using the same type of vessel and similar observational methods (Sagarin et al. 2008). Dosidicus is a monocyclic, short-lived species that matures only once at a broad size range. During favorable years, large squid prevail and commonly reach a mantle length (ML) of >60 cm and a mass of 20 kg or more at maturity, with a life span of 1.5–2.0 years in the Sea of Cortez (Hoving et al. 2013). [End Page 411] Large squid of this sort supported the third- or fourth-largest commercial fishery in Mexico for the decade preceding the 2004 trip, with the vast majority of landings coming from the Guaymas Basin area (Rosa et al. 2013). These factors made it hard for even a casual observer in the Central Gulf to be unaware of Dosidicus gigas between 1995 and 2009. It thus seems that large Humboldt squid were likely not to have been abundant in the Gulf of California in the spring of 1940, and reasons for the apparent change in the status of Humboldt squid since that time have been discussed without reaching any firm conclusion (Sagarin et al. 2008). Shortly after publication of the 2008 paper, a strong El Niño in 2009–2010 influenced the Central Gulf in a profound way. Humboldt squid in this region responded to this climatic anomaly by taking on a characteristic of the tropical portion (Costa Rica to Ecuador) of their large range, where squid mature at extremely small size (~30 cm ML, ~0.1 kg) and live for only about 6 or months (Hoving et al. 2013). In addition, commercial landings crashed. Both phenomena also occurred in conjunction with the strong El Niño of 1997–1998 (Bazzino et al. 2007; Morales-Bojórquez and Nevárez-Martínez 2010). Although recovery of landings and return to a large size at maturity occurred within a few years after the 1997–1998 event (Markaida 2006), recovery has not occurred during the years after El Niño 2009–2010, a period characterized in the Central Gulf by reduced wind-driven upwelling and productivity (Robinson et al. 2016) and, as documented in the present paper, increased warming at depth (see also Frawley et al. 2019). Another strong El Niño occurred in 2015–2016. These observations suggest that the ecological state of the Gulf of California can show drastic, long-lasting alterations that involve the size of Humboldt squid. Although small Humboldt squid are probably still abundant in the Gulf (Hoving et al. 2013 and unpublished jigging data), they are clearly much less obvious (and more difficult to capture by jigging) than larger squid were a decade ago. This new awareness is relevant to the question of why Steinbeck and Ricketts did not record this species in the Sea of Cortez in 1940. We examine several possibilities in reassessing this question. First, squid may not have been of much interest to the intertidal explorers in 1940, so not much attention was paid to this group. Second, small, juvenile specimens of Dosidicus gigas were in fact collected but misidentified. Third, large Humboldt squid were temporarily absent from the Gulf during their visit because of the effects of El Niño. Fourth, [End Page 412] large (and potentially smaller) squid were absent because of chronically unfavorable...