Effect of Minimum-size Regulations on the Legal Catches

The minimum size of crayfish which may be taken from the Wellington area has recently been raised from eight inches (20.3 cm.) to nine inches (22.9 cm.) in total length. These limits have apparently been fixed in an arbitrary manner, since no research appears to have been carried out to determine the best legal limit.

The purpose of setting a size-limit is to conserve stocks. Accordingly, it is a matter of principle that small individuals should not be taken until they have had a chance to reproduce. The smallest berried female found was 7.5 in. in total length and the smallest found by Hickman (loc. sit.) was 7.7 in. in total length. It is apparent, then, that most of the females will reach maturity within the protected range. It must be noted also that small crayfish yield a relatively small amount page 10 page 11 of meat. Leg meat, rarely extracted from crayfish smaller than 9 in. because of its difficulty of removal, comprises approximately one-third of the total meat obtainable from specimens only slightly larger than 9 in. (see page 24). Protection of small specimens on the basis of their immaturity and waste of meat must, however, be reconciled with the effect on the fisherman's income. The whole random sample examined in this study included 20% below the legal size-limit. On a weight basis, this is 8% of the catch. This is the important percentage to be considered and it shows that the present size restrictions do not have a very great effect on the fishermen except in the work involved in selecting and rejecting the undersized individuals.

For the above reasons it may be said that, although the 9 in. size-limit seems to have been imposed without much preliminary research, it appears to have been a fairly good choice.