Laboratory observations on the vertical swimming behavior of Japanese common squid Todarodes pacificus paralarvae as they ascend into warm surface waters

Abstract

This study examined the effect of warm temperature on the survival of paralarvae of Japanese common squid Todarodes pacificus and on their swimming behavior as they ascended to the surface. Observations were conducted on paralarvae in Petri dishes and in 85-cm-tall, cylindrical tanks that had a warmer upper layer and cooler lower layer separated by a small thermocline. Paralarvae were obtained through artificial fertilization and reared in Petri dishes at six experimental temperatures between 20.9 and 30.4°C. Paralarvae reared at lower temperatures survived longer than those reared at warmer temperatures, and survival decreased at temperatures above 24°C. When the mean temperatures in the upper layer of the tanks were 24.4-26.0°C, the paralarvae ascended through the thermocline to the surface, but when the mean temperatures in the upper layer were 29.7-29.8°C, paralarvae stopped ascending at the thermocline. These results show that paralarvae have a temperature preference but ascend to the surface in the unfavorable temperature range. The results suggest that increasing surface temperatures at spawning grounds will negatively affect both the survival and behavior of T. pacificus paralarvae.

Paralarvae of the complex Sthenoteuthis oualaniensis‐Dosidicus gigas (Cephalopoda: Ommastrephidae) in the northern limit of the shallow oxygen minimum zone of the Eastern Tropical Pacific Ocean (April 2012)

“…Given that squid paralarvae of D . gigas and Todarodes pacificus are demonstrably sensitive to temperature gradients [ Camarillo‐Coop et al ., ; Staaf et al ., ; Yoo et al ., ], and possibly also to dissolved oxygen [ Gilly et al ., ] , net haul sampling was carried out in these three layers. For the purposes of the cruise, the thermocline was defined as the temperature band 16–22°C, which was roughly centered around the maximum temperature gradient.…”

“…Vertical distributions of fish larvae are often separable into strata associated with the surface mixing layer, thermocline/chlorophyll a maximum layer, and deeper layers [e.g., Danell-Jim enez et al, 2009;Davies et al, 2015]. Given that squid paralarvae of D. gigas and Todarodes pacificus are demonstrably sensitive to temperature gradients [Camarillo-Coop et al, 2011;Staaf et al, 2011;Yoo et al, 2014], and possibly also to dissolved oxygen , net haul sampling was carried out in these three layers. For the purposes of the cruise, the thermocline was defined as the temperature band 16-228C, which was roughly centered around the maximum temperature gradient.…”

Observations on the spawning behavior, egg masses and paralarval development of the ommastrephid squid Todarodes pacificus in a laboratory mesocosm

“…A longer developmental time within the egg mass also provides an enhanced opportunity for developing embryos to absorb organic nutrients from the oviducal gland jelly (Bower and Sakurai, 1996). Vertical swimming experiments conducted by Yoo et al (2014) with T. pacificus revealed that the paralarvae consistently have a preference for surface layers. Field surveys also collected hatchling-sized paralarvae at the surface waters (Yamamoto et al, 2002).…”

Early Mode of Life and Hatchling Size in Cephalopod Molluscs: Influence on the Species Distributional Ranges

“…In fact, transport by currents has been shown to be a powerful dispersal mechanism for planktonic squid [9–14] and octopus paralarvae [15, 16]. In addition to this passive transport, the swimming capacities recorded in the laboratory for planktonic cephalopod hatchlings are within the range or higher than those found for the larval fishes [17–22], which could enhance their dispersal potential. In contrast, mark and recapture experiments with hatchlings of large, benthic cuttlefish, showed limited shallow water dispersal, as the individuals remain in the same or adjacent bays to those in which they hatched [23].…”