Archet. — Fresh-water Crayfish of New Zealand. 309 



Since this paper was read before the Canterbury Philosophical Institute 

 Mr. A. Dudley Dobson has informed me that some years ago, when water- 

 races were first constructed from the Murray River in Australia, the cray- 

 fish did so much damage to them that the races had to be lined with concrete. 



Amongst the hills around Waimate are main- deep pools, known as 

 the " Crayfish Holes," from which the crayfish can be taken in any quantity. 

 Faxon (1898, p. 681), quoting from a letter received from Dr. Chilton 

 with regard to specimens obtained near Dunedin, observed that the speci- 

 mens taken from small streams were of very small size, though sexually 

 mature, and had few spines, while those taken from a reservoir formed 

 by damming up one of the small streams attained a length of 158 mm. 

 and were heavily tuberculated. This is also the case with the specimens 

 I have used, and it seems that fairly dee}, slow-moving waters provide 

 the best conditions for their growth. 



A similar example of the connection between the size of an animal and 

 the volume of water in which it lives appears in Sempers volume on 

 "Animal Life*' (1899, pp. 160-61) in the International Scientific Series, 

 which contains an account of two series of experiments connected with 

 the growth of a gastropod mollusc- — Limnaea stagnalis—\xv'mg in different 

 volumes of water, but otherwise in equally favourable conditions for growth. 

 The results were that " the smaller the volume of water which fell to I 

 share of each animal, the shorter its shell remained." 



The abundance of crayfish in special localities suggests that it would 

 be possible to breed the animals for use as articles of food, for the^- are 

 said to be excellent eating ; but it would be necessary, before this could 

 be done successfully, to ascertain the number of years they require to grow 

 to a full size, as well as to obtain more definite information with regard 

 to their breeding and life-history. The frequent floods to which so main' 

 of our rivers are subject are the cause of the destruction of large numbers 

 of crayfish, which may be washed out of the small streams into the deep 

 rapid rivers. A correspondent from Southland has stated that he has 

 seen hundreds washed up on the lower beaches of the large rivers after a 

 flood. It is also evident that, in common with other members of our native 

 fresh-water fauna, the crayfish are being destroyed by eels and the introduced 

 fishes. Trout have been caught with partly digested crayfish in their 

 stomachs, and it is probable that the restriction of crayfish to such places 

 as cannot be inhabited by these fish is only a matter of time. 



(B.) Food. 



Some specimens were kept for a time in large glass battery- jars, into 

 which was thrown a certain amount of river-weed, mainly for the aeration 

 of the water. The crayfish were never actually seen eating any of this, 

 but at evening it was noted that the bottom of the jar was quite clean, 

 while in the morning there would be seen lying around chopped-up pieces 

 of the plant. Small worms or pieces of meat placed in the jar were in- 

 variably left untouched, though crayfish are often caught by using meat as 

 bait. An examination of the contents of the stomach of several individuals 

 showed the presence of the roots and stems of plants, pieces of such 

 fresh-water algae as Spirogyra.smd Vauckeria, together with broken frag- 

 ments of the different kinds of small aninnls generally found amongst 

 the river-weed. A fairly large piece of the flesh of some animal was 

 found in the stomach of one individual. 



