Relative abundances and size compositions of champagne crabs, Hypothalassia acerba, on two coasts and in different water depths and seasons

Abstract

Hypothalassia acerba was sampled seasonally using traps at depths of 35, 90, 145, 200, 255, 310 and 365 m on the west and south coasts of Western Australia. Catch rates peaked at depths of 200 m on the west coast and 145 m on the south coast but at similar temperatures of 16.1–17.1°C. The west and south coast catches contained 69% and 84% males respectively. The carapace length of H. acerba declined significantly by 4 mm for each 100 m increase in depth. The maximum carapace length of males was greater than females on the west coast (135 v. 113 mm) and south coast (138 v. 120 mm). Furthermore, after adjustment to a depth of 200 m, the mean carapace lengths of males were greater than females on both the west coast (96.6 v. 94.6 mm) and south coast (101.5 v. 91.4 mm), with the difference on the south coast being significant (P < 0.001). Thus, in summary, (1) distribution was related to depth and temperature; (2) body size was inversely related to water depth; and (3) males grew larger and were caught in greater numbers than females. There was also evidence that the distribution changed slightly with season and of spatial partitioning by H. acerba and other large deep-water invertebrate predators.