I.—A Contribution to the Life-Histories of the Cod and Whiting

Extract

Considering the abundance of this gadoid, it is a matter for surprise that our knowledge of its life-history is not more complete. The work of Prof. Sars upon the cod in Norwegian waters is well known, and need not be referred to in any detail here. It is, however, important to avoid the assumption that his account will apply in every detail to the cod of British waters.

In 1883 Prof. M'Intosh showed that the cod spawned in early spring and that spawning was effected outside the territorial limit. Dr Fulton, from an examination of a number of captured specimens, was led to the same conclusion; and further, that the cod, whilst having an extended spawning period reaching from January to June, must be regarded as having a main period of February, March, and April, the great majority of individuals spawning in the month of March. Thus whilst 40 per cent, of the fish examined in March were mature, the proportion fell to 16 per cent, for February and April, and 10 per cent, for May. In estimating the growth of this species, by the method pursued below, it is probably most correct to regard the true spawning period as including the months of February, March, April, and May. A study of the distribution of pelagic eggs off the Frith of Forth leads to a similar conclusion. From this latter source the spawning period of the cod can be defined as extending from the third week in February to the second week in May, with a maximum in early April.