Growth rate in a population of the freshwater crayfish,Paranephrops planifronswhite

Abstract

SUMMARYObservations on growth increments at moult in a population of freshwater crayfish, Paranephrops planifrons, were made from periodic recaptures of marked animals. The growth increment increased with increasing size of crayfish up to about 20 mm carapace length (65 mm total length) after which a slight decrease was evident. By analysis of the size distributions in samples taken at different times of year it was found that four to five year classes were normally present. Growth of these age components could be followed through consecutive samples. Mean size at leaving the parent in December was 3.5 mm, after one year 11.4-11.8 mm, after two years 18.2-19.3 mm, after three years 22.1-23.8 mm, and after four years 26.7-29.6 mm, all sizes quoted as carapace lengths. After sexual maturity growth in the females was less than in the males. The number of moults completed by each year class was found by relating data on growth increment per moult to growth shown in consecutive quantitative samples. In the first year of life nine moults were completed, in the second year three moults, in the third year two moults, and in the fourth one moult. Independent data on moult frequency recorded from marked crayfish agreed well with these figures.

Aspects of the biology and ecology of the Orange-Bellied Crayfish,Euastacus mirangudjinCoughran 2002, from northeastern New South Wales.

“…Eggs were found to follow the general pattern of development observed for other parastacid crayfishes (Hopkins 1967;Hamr 1992;Honan 1998), the only notable difference being the failure of the eggs of Euastacus mirangudjin in the laboratory to cement onto the pleopodal setae of the female. It is uncertain if this is due to the laboratory conditions, or indicates that this is not a feature of the reproductive biology of this species.…”

“…It is uncertain if this is due to the laboratory conditions, or indicates that this is not a feature of the reproductive biology of this species. The latter alternative would be highly unusual, as cementing of eggs onto the setae is a well-documented aspect of the reproductive biology for both parastacoidean (Hopkins 1967;Suter 1977) and astacoidean (France 1983) crayfishes. France (1983) found acidification of the waterbody affected the glair cement on Orconectes virilis, resulting in severe recruitment failure.…”

Biology of the Blood Crayfish,Euastacus gumarMorgan 1997, a small freshwater crayfish from the Richmond Range, northeastern New South Wales

“…The eggs hatched between 49 and 56 days after capture. New hatchlings bear an undeveloped tailfan, larval cephalothorax, telson thread and the recurved terminal hook and spine arrangement on the 4 th and 5 th pairs of pereiopods, features that are characteristic of other parastacid hatchlings (Clark 1936(Clark , 1937Shipway 1951;Hopkins 1967;Suter 1977;Hamr 1992;Honan 1998). Juveniles pass through two moults (i.e.…”

Growth of two species of freshwater crayfish (Paranephropsspp.) in New Zealand

“…The only previous information on the biology of Paranephrops, apart from the observations of early naturalists such as Archey (1915), comes from a study by Hopkins (1966Hopkins ( , 1967a on streamdwelling populations of P. planifrons in the lower North Island. The studies on aquaculture outlined by Shaddick (1976) were never completed.…”

“…New Zealand has two species of freshwater crayfish -Paranephrops planifrons, confined to the North Island and the Marlborough, Nelson, and West Coast districts of the South Island, and P. zealandicus which is found in the North Canterbury, Canterbury Plains, Otago, and Southland districts of the South Island, and Stewart Island (Hopkins 1970).…”