Introduction

Jasus lalandii occurs in South Africa, the southern coasts of Australia, Tasmania, New Zealand, Chile, Juan Fernandez, Tristan da Cunha, and Saint Paul (Indian Ocean).

In South Africa, Australia, and New Zealand, it is of considerable economic importance. In South Africa, a valuable canning industry has existed since 1902. In 1938–39, this produced £129,862 worth of canned "crawfish." The value of the exports of frozen tails and canned meat was £243,010 in 1939. In Australia and New Zealand, large numbers are cooked and sold on the local market. In New Zealand, in 1946, 16,766 hundredweight (£30,801) of crayfish was marketed. The value of canned and frozen crayfish exported was £11,704. The landings at Wellington were greater than at any other port (£7,685), but Dunedin exported overseas a greater amount of canned and frozen crayfish (£5,314) than Wellington (£4,938).

Jasus lalandii has been studied extensively in South Africa, chiefly by Gilchrist (1913–1920), Gilchrist and C. Von Bonde (1922), C. Von Bonde (1928), W. Von Bonde (1930), C. Von Bonde and Marchand (1935), and C. Von Bonde (1936). page 3 Some work has been done in Australia by Challenger (1943) and Sheard (1947), and in Tasmania by Hickman (1945). In New Zealand, Parker (1884) described the skeleton, and Young (1926) studied the growth of a crayfish in captivity. Apart from this, no work appears to have been done in New Zealand.

Whenever natural resources are tapped, it is essential that a sound method of utilization he adopted. Before a proper method of utilization can be evolved, it is necessary to have a thorough knowledge of the natural history of the species concerned. This is moderately well known in South Africa, but little is known of the species in New Zealand.

The work covered in this paper has been restricted to the Wellington area from Oteronga Bay to the Orongorongo River (see Fig. 2). The fishing is carried out mainly in shallow water around the rocky parts of the coast. Observations were made during 1947 and 1948 on board the fishing boats operating from Island Bay. These boats supply most of the crayfish consumed on the Wellington market, and some of the catch is sent to inland towns in the Wellington province. Random samples of the catch have been examined as often as has been possible. These observations provide data on the population composition and its variation throughout the year, the onset and duration of the spawning season, segregation of the sexes and migration, the onset of maturity in females, and the effect of minimum-size regulations on the fishermen's income. Weather and temperature conditions were noted on each fishing occasion; salinity estimations were begun but were soon terminated, as the variations were considered too small to be of biological significance (see Fig. 3). In 1948, fishing was carried out at Moa Point using a dinghy and standard pots. This work has provided additional data and specimens for tagging, for the estimation of egg production, estimation of the amount of usable meat in specimens of various sizes, and shrinkage in cooking. Of 168 specimens tagged, nine were recaptured, giving limited information on the growth rate and movements.

A total of 2,126 specimens was examined over the period of two years. Weather conditions greatly influence fishing. Accordingly, there are some months for which only limited data have been obtained. As samples from the 1947 catches are not significantly different from those of 1948, the data for the two years have been combined and the conclusions presented concern this period as a whole. The conclusions must be taken as representing the Wellington area from Oteronga Bay to the Orongorongo River as a whole. Statements made about the population in this area as a whole at some particular time may not be true of a small division of it.

I wish to express my sincere thanks to the Marine Department for financial assistance, to Professor Richardson, of Victoria University College for his guidance and assistance during the course of this study, to Mr. Kaberry, of the Marine Department, for his helpful suggestions, and to Mr. Alberino, of Island Bay, for allowing me to accompany him on many fishing trips.