Changes in the Chemical Composition of the Tissues of the Herring in Relation to Age and Maturity

Abstract

NUMEROUS proximate analyses of the tissues of the herring and other clupeoid fishes have been published from time to time. Milroy [1906, 1907, 1908] and Johnstone [1915, 1918, 1919, 1920] have established the fact that herrings caught at different times and in different localities vary widely in composition, especially in fat-content, and they have correlated these variations with the reproductive phases and periods, and with the bodily measurements of the fish. Up to the present, however, no attempt has been made to ascertain the extent to which age, as distinct from maturity or size, affects the chemical composition of the tissues. This is doubtless due to the fact that no reliable and universally applicable criterion of age has been available. Length, and other standardised measurements, may afford fairly reliable evidence as to the relative ages of the individuals in a single shoal, but the existence, within the species, of separate "races " of fish, of widely differing characters, in- validates any comparison of data obtained from other and distant shoals.