Variations in vertical distribution of developing snow crab Chionoecetes opilio and red snow crab Chionoecetes japonicus (Crustacea, Decapoda, Majoidea) larvae in experimental temperature gradients

ABSTRACT

In the Sea of Japan, field studies have found snow crab and red snow crab larvae occur between the surface and depths of up to 550 m and 1100 m, respectively. In this region, snow crab larvae hatch at depths of 240–260 m and red snow crab larvae hatch at 1000–1500 m. To understand their vertical distribution during the larval period, we investigated the upward swimming speed of newly hatched larvae (first-stage zoea) and the behaviour of all larval stages (first and second zoeal and megalopal stages) in a temperature gradient under laboratory conditions. Our results showed that the larvae have the potential to reach the surface within a few days of hatching. As the larvae developed, they preferred greater depth and lower temperatures; although they temporarily rose to higher levels immediately after each moult. The zoeae and megalopae of both species did not occur beyond the 16 and 6°C temperature layers, respectively. The preferred position of the larvae in the gradient temperature did not differ between the two species. The present study suggests that Chionoecetes larvae transported to unsuitable temperatures may not die, but could escape from low temperatures by upward swimming and from high temperatures by sinking.

KEYWORDS:

• Deep-sea crab
• pelagic larva
• regulation of distribution
• thermocline
• thermotaxis

Acknowledgments

We are grateful to Mr. Fujio Yamashita, Captain of the fishing vessel Taikimaru, and Mr. Hirotsugu Yamashita and Mr. Yoshihiro Yamashita, Co-Captains of the fishing vessel Kanshomaru, for collecting the ovigerous crabs used in this study. We are also grateful to two anonymous reviewers for their valuable comments and suggestions, which have improved the manuscript. The Fisheries Agency of Japan funded this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07924259.2024.2366243.

Additional information

Funding

This study was supported by Promotion Program for the Marine Fisheries Stock Assessment and Evaluation for Japanese Waters (Fisheries Agency of Japan).