12 Indian J. Fish., 61(1) : 12-15, 2014 Growth and mortality of Osteogeneiosus militaris (Linnaeus 1758) from Mumbai waters PRANAYA KUMAR PARIDA * , A. K. JAISWAR, R. PALANISWAMY, PAWAN KUMAR AND S. K. CHAKRABORTY Central Institute of Fisheries Education, Panch Marg, Yari Road, Mumbai - 400 061, Maharashtra, India * Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana - 141 004, Punjab, India e-mail : sushanta.c@rediffmail.com ABSTRACT Based on the length frequency data collected during the period January 2002 to August 2004, the growth and mortality parameters of Osteogeneiosus militaris was estimated. The asymptotic length (L ∞ ), growth coeficient (K) and t o were estimated as 583 mm, 0.67 yr -1 , and -0.0396 years respectively. Based on the von Berttalanffy growth (VBG) parameters, the growth of the ish during 1 to 5 years of its age works out to be 292, 426, 487, 516, and 529 mm respectively. The growth performance index was estimated as 3.55. The instantaneous rate of total mortality was estimated as 3.55, natural mortality as 1.04 and ishing mortality as 2.51. The phi prime was estimated as 3.35. The exploitation ratio (U) and exploitation rate (E) were worked out as 0.67 and 0.70 respectively. The vulnerability of catish in general and O. militaris in particular with respect to over-exploitation, destruction of eggs, incubating males and the inherent low fecundity of the family are discussed in the present communication. Keywords: Asymptotic length, Growth coeficient, Growth parameters, Osteogeneiosus militaris Introduction Marine cat ish belonging to the family Ariidae (Tachysuridae) is one of the important ish resources of the country. Growing to a size of nearly 50 – 60 cm, the average annual total marine ish catch in India during 2002-2011 period was about 2.92 mmt and during the same period, the annual average catch of marine catish was 71000 t which was 9.35% of the demersal catch and 2.24% of the total marine ish catch of the country (Anon, 2002-12). From the isheries point of view, ive species of marine catish are important viz., Netuma thalassina, Netuma dussumieri, Plicofollis tenuispinis Arius jella and Osteogeneiosus militaris. The major catish producing states in India are Gujarat, Maharashtra, West Bengal and Odisha. The annual average catch of catish during the period 2002-2012 in Maharashtra was around 11827 t contributing 2.78% to the total catch (Anon, 2002-2012). A good number of researchers have worked on the catish ishery resources of India (Pantulu, 1963; Dan, 1980, 1981; Gulati et al., 1996; Chakraborty et al., 1997; Menon, 1979; Krishna, 1981; Menon et al.. 1992; Raje et al., 2008). Raje and Vivekanandan (2008) discussed about the vulnerability of catish especially with reference to growth overishing and low fecundity. Osteogeneiosus militaris is distributed along the Indo-Paciic region from the west coast of India to Bangladesh, Myanmar, Singapore, Malacca, Indonesia, Brunii, Darussalam, Malaysia and Pakistan. In the present communication, the growth and mortality parameters of O. militaris is reported. This study is based on the length frequency data collected from New Ferry Wharf, Sassoon Docks and Versova during the period from January, 2002 to August, 2004. Materials and methods Weekly length frequency data were collected from the three landing centres of Greater Mumbai viz., New Ferry Wharf, Sassoon Docks and Versova. Total length of the ish was taken from the tip of the snout to the tip of the caudal in in mm. During the period of study, 2635 specimens in the length range of 154 to 489 mm were measured. The total catch was estimated on the day of observation. The data thus collected were distributed into 20 mm groups and was raised for the day and subsequently for the month following Sekharan (1962). The growth was expressed using the von Betrtalanffy’s formula given as : Lt = L ∞ *(1-e -K(t- t o ). Growth parameters like L ∞ and K were estimated employing the Bhattacharya’s (1967) method which involves separating the normal distribution each representing a cohort of ish from the overall distribution. By this method, a rough estimate of asymptotic length (L ∞ ) and growth coeficient (K) was made. These two parameters were further reined using Gulland and Holt’s plot (1959) where the pair of data used for regression are mean length L and difference in length at different age ∆L/∆t, which gives the value of L ∞ and K as K = - b, and L ∞ = -a/b. The t o was estimated by von Bertalanffy (1938) plot which is given as – L n (1-lt/L ∞ ) = -K*to + K*t where ‘t’ is the independent variable. The equation becomes linear and the values of ‘a’ and