Locomotion and behavior of Humboldt squid,Dosidicus gigas, in relation to natural hypoxia in the Gulf of California, Mexico

Abstract

SUMMARYWe studied the locomotion and behavior of Dosidicus gigas using pop-up archival transmitting (PAT) tags to record environmental parameters (depth, temperature and light) and an animal-borne video package (AVP) to log these parameters plus acceleration along three axes and record forward-directed video under natural lighting. A basic cycle of locomotor behavior in D. gigas involves an active climb of a few meters followed by a passive (with respect to jetting) downward glide carried out in a finsfirst direction. Temporal summation of such climb-and-glide events underlies a rich assortment of vertical movements that can reach vertical velocities of 3ms , characteristic of the midwater oxygen minimum zone (OMZ), can influence the daytime depth of squid, but this depends on location and season, and squid can ʻdecoupleʼ from this environmental feature. Light is also an important factor in determining daytime depth, and temperature can limit nighttime depth. Vertical velocities were compared over specific depth ranges characterized by large differences in dissolved oxygen. Velocities were generally reduced under OMZ conditions, with faster jetting being most strongly affected. These data are discussed in terms of increased efficiency of climband-glide swimming and the potential for foraging at hypoxic depths.

Aperture effects in squid jet propulsion

“…Regular vertical excursions followed by sinking could result in significant energetic savings, as has been demonstrated for numerous negatively buoyant zooplankton (Haury and Weihs, 1976). Hop-andsink behavior has been reported in other cephalopod paralarvae (Zeidberg, 2004;O'Dor, 1988a;Boletzky, 1974) and may well be an adaptation to save energy, as in the similar strategy of climb-and-glide swimming exhibited by adult D. gigas (Gilly et al, 2012).…”

“…Owing to the energetic loss of accelerating a relatively small jet of water to high speed, as well as the costly refilling period, during which there is no active thrust, squid jet propulsion is inherently inefficient in comparison to undulatory locomotion in fish O'Dor and Webber, 1991). Efficiency of jet propulsion in squid can be improved by climb-and-glide jetting (Gilly et al, 2012), but this option is also open to fish (Schaefer et al, 2007), leaving squid still at a disadvantage. However, one possible efficiency-increasing measure is unique to pulsed jet locomotion: the formation of vortex rings.…”

ITAG: an eco-sensor for fine-scale behavioral measurements of soft-bodied marine invertebrates

“…For example, decreased temperatures or increased pCO 2 levels can induce delays in squid embryo development [16,17]. Vertical movements and respiratory patterns of the Humboldt (jumbo) squid Dosidicus gigas appear tied to both dissolved oxygen and local environmental temperatures [18][19][20]. Some medusae may undergo reverse development when environmental conditions are reproductively unfavorable, enabling "temporal persistence" and longer foraging periods [21].…”

“…Measurements of such responses would elucidate the natural swimming modes, predation behaviors, and metabolic rates of squid and jellyfish. Further, environmental measures are often made in the broad area but not at immediate surroundings of the animal [20], potentially obscuring vital fine-scale animalenvironment interactions with conditions such as thin layers, thermoclines or oxygen minimum zone boundaries. Even with state-of-the-art oceanographic equipment such as CTDs and Argo Floats, we often lack fine-scale habitat measures, particularly in coastal areas, at scales relevant to soft-bodied organisms.…”

“…In addition, tags were typically affixed to jellyfish by attaching plastic cable-ties and lines to oral arms; this attachment technique cannot be applied across many jellyfish taxa where these morphological features are absent. Large Humboldt squid (D. gigas) were tagged using relatively large depth-temperature satellite transmitting tags (with ~1 Hz resolution) and "Crittercam" video packages [20]. Reducing the size of the tagging package will enhance the range of available species and age/size classes available for study, and measurements at higher sampling frequencies (>60 Hz) will help to enable the characterization of animal swimming modes, predation behaviors, and metabolic rates of squid and jellyfish.…”