Length-weight relationshisp and relative conditions factor for the halfbeak Hemiramphus far Forsskål , 1775 from the Karachi coast

Abstract

Growth of an organism means a change in length or weight or both with the Increase of age. Increment in size is due to conversion of the food matter into building mass of the body by the process of nutrition. A vector diagram known as growth curve is obtained, when length or weight of an individual are plotted against a specified time period. The curve appears as a sigmoid one, which may vary for the same fish from different localities or for the same fish at different seasons. The rate of growth may easily be influenced by many physical and physiological factors. Different organs of body or have different rates of growth. Theoretically, it is expressed by the formula of cube law (LeCren, 1951), W = KL 3, where, W = weight of fish, L = length of fish, K = constant. This formula is true when the fish showing symmetrical or isometric growth throughout the growth stage. However, in nature, the body proportion of a fish continuously changes with ageing. So the simple cube law expression therefore does not found properly throughout the life history of fish, as the value of K is not constant but subject to great variation. Therefore, a more satisfactory formula is given as follows: W = aL n, or (Log W= log a + n Log L)