Hypothalassia acerba

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| name = Hypothalassia acerba | image = | image_caption = | regnum = Animalia | phylum = Arthropoda | subphylum = Crustacea | classis = Malacostraca | ordo = Decapoda | subordo = Pleocyemata | infraordo = Brachyura | familia = Eriphiidae | genus = Hypothalassia | species = H. acerba' | binomial = Hypothalassia acerba | binomial_authority = George 1966 }}

Hypothalassia acerba, also known as the champagne crab, is a large crab found in the muddy substrates of the deep seas off the south-western Australian and New Zealand coasts.^[1] Australian distribution, which is correlated to depth and temperature ^[2], ranges from a latitude as far north as approximately 27 degrees S on the west coast, southwards, then eastwards on the south coast to a longitude of at least 129° E ^[3]. The species usually occurs in waters with temperatures ranging between 13 and 19 degrees Celsius and in depths ranging from 200-255 m on the lower west coast and from 90 - 200 m on the south coast ^[4]. Body size is inversely related to depth of water ^[5]. H. acerba is not the same champagne crab as the other Hypothalassia subspecies, H. armata, which is found in Japanese waters.^[1]

Contents 1 Description 2 Ecology 3 Capture 4 References

Description

The species has well-defined groves on a hexagonal carapace, with a smooth dorsal surface and a spiny anterior surface. Their branchial openings are partially covered by maxillipeds, and have asymmetrical chelipeds with stiff, brown-black spines of various sizes on their walking legs. The frontal region is beige-cream and covered in many short setae. Walking legs have a dactylus of 3.7-4.3 times as long as wide.^[1]

Ecology

Although life history is not very well known, some data has been collected on reproduction. Hypothalassia acerba reproduction is highly correlated with seasons, due to water temperature fluctuations. Oviposition primarily occurs in the summer between January and March ^[4][5]. Females have a tendency to migrate from the south coast eastwards and then northwards to spawn on the lower west coast^[5][5]. The fecundity of this species may be due to it’s relatively short breeding season, therefore adapting to optimize egg production ^[5]. Hall et al (2004) propose that the larvae of this species is plantonik ^[2], and is therefore probably carried away from the lower west coast by the Leeuwin current ^[5].

Negligible reproduction occurs on the south coast, where maturity is delayed^[4].

Capture

Hypothalassia acerba was first discovered to have a fishery potential in 1966.^[1] It is fished using baited traps placed between 150-360 m water depths in southern and western waters off the coast of Australia^[6].

Females with eggs are strictly prohibited from fishing. Females have a tendency to be smaller than males, and thus males are more prevalent in catches than females^[6]. Fifty percent size at sexual maturity^[2] has been estimated at 69.7 mm and is therefore used as the minimum catch size to aid in sustainable stock levels^[6]. However, it should be noted that this estimation may be considerably under-estimated due to fishing biases ^[6][5].

Between the years 1997 and 1999, champagne crab catch rates escalated to between 30 and 45 tonnes. After the year 2000, stocks dropped to negligible levels (>100 kg) which was partially due to a decline in stock as well as a greater demand for another deep-sea crab, Chaceon bicolor. Therefore, management of champagne crabs is now primarily focused on safeguarding the biological sustainability of H. acerba and maintaining breeding stocks rather than establishing a viable commercial fishery on the west coast. ^[2]

References

1. ↑ ^{1.0 1.1 1.2 1.3} Poore, G. C. B. 2004. Marine Decapod Crustacea of Southern Australia: A Guide to Identification. CSIRO Publishing, Collingwood, 616 pp.
2. ↑ ^{2.0 2.1 2.2 2.3} Hall, N.G. et al. (2006). "Does the largest chela of the males of three crab species undergo an allometric change that can be used to determine morphometric maturity?" Journal of Marine Sciences 63: 140-150.
3. ↑ Hall, N.G., Potter, I.C. and Smith, K.D. (2004). "Biological and fisheries data for managing the deep-sea crabs Hypothalassia acerba and Chaceon bicolor in Western Australia : final report". Centre for Fish and Fisheries Research, Murdoch University.
4. ↑ ^{4.0 4.1 4.2} Smith, K.D., Potter, I.C. & Hesp, S.A. (2004). "Comparisons between the reproductive biology of two species of deep sea crabs that live in different water depths". Journal of Shellfish Research 23: 887-896.
5. ↑ ^{5.0 5.1 5.2 5.3 5.4 5.5 5.6} Smith, K.D. (2006) "Distributions, relative abundances and reproductive biology of the deep-water crabs Hypothalassia acerba and Caceon bicolor in southwestern Australia." PhD thesis, Murdoch University.
6. ↑ ^{6.0 6.1 6.2 6.3} Smith, K.D. et al. (2004) "Potential bias in estimates of the size of maturity of crabs derived from trap samples". ICES Journal of Marine Science 61: 906-912.