Age and growth rate of blue mackerel ( <i>Scomber australasicus </i>Cuvier, 1831) in the Gulf of Aden
Some aspects on the growth rate of blue mackerel Scomber australasicus in the Yemen waters are presented. The data were obtained from 38 research cruises to the Yemen waters and eastern coasts of Africa as well as from 80 expeditions to the adjacent waters (Somalia, India, Pakistan, Oman, and Mozambique). All the accessible data on the Soviet catches of blue mackerel within the Yemen Republic waters were processed. In order to determine blue mackerel age, its otoliths, scale and opercula were collected during 1981-1983. From 1980 to 1991, 808 pairs of otolith samples were processed. Owing to the fact that in the fishery cruises only standard fish length was measured, specific formu las were calculated to unify standard and fork lengths. Data were collected within the range of all lengths in the catches (12-36 cm). Altogether, 620 blue mackerel specimens were analyzed. It is shown that t he relationship between standard length and fork length can be represented by a straight-line equation. The relationship between length and mass is expressed by a parabolic curve. Application of several methods to determine the age-length relationship made it possible to find out that the process of fi sh growth up to the age of 2.5 can be most explicitly expressed by a parabolic curve, approximating the data of direct observations; further fish growth is properly represented by the Bertalanffy curve. The three stages of blue mackerel growth were distinguished in the life cycle: rapid length growth during the first year of life, rapid weight growth from the second to the sixth year of life, and decrease of length and weight growth rate after the sixth year of life.