S373 Document heading Length-weight relationship and morphometrics of the sailfish, Istiophorus platypterus (Shaw & Nodder) from Parangipettai, Southeast coast of India Velayudham Ravi * , Veeramuthu Sekar and Kaila Kesavan Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Tamil Nadu, India Asian Pacific Journal of Tropical Biomedicine (2012)S373-S376 Asian Pacific Journal of Tropical Biomedicine journal homepage:www.elsevier.com/locate/apjtb *Corresponding author: Velayudham Ravi, Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Tamil Nadu, India. E-mail: ravi.velayudham@gmail.com 1. Introduction The I ndo-Pacific Sailfish Istiophorus platypterus ( I. platypterus) (Shaw and Nodder, 1792) (Family (Istiophoridae) is one of the world ’ s charismatic fish species and cosmopolitan in nature. Report on the fishing effort and size groups of the sailfish in the landings are essential [1] . The sailfish is currently emerging as a significant billfish fishery along the Indian coast [2] and they are captured using hooks and longlines in India. The billfish (including sailfish) catch was 8 303 tonnes in the year 2010 [3] and their resources along the Indian coast has been reported [1-7] . Meanwhile, studies on sailfish from Parangipettai region are also available on distribution [8] and dietary composition [9] . Being an important factor in the biological study of fishes and their stock assessments, the length-weight relationship (LWR) plays a significant role in parameterizing yield equations and in the estimations of stock size [10] and this relationship can also be used for the studies on gonad development, feeding rate, metamorphosis, maturity and condition [11] . The present study is on the salient morphometric parameters and length-weight relationship of the sailfish (I. platypterus) from Parangipettai coast (Tamil Nadu), southeast coast of India. 2. Materials and methods A total of 130 sailfishes (I. platypterus) were measured and weighed (Length: 92 cm to 385 cm TL; weight: 2.5 kg to 105 kg, respectively) from the landing centre at Parangipettai (Lat. 11曘29’ N; Long. 79曘46’E) during the study period (July 2010 to June 2011). In this region, the fishing gears used include drift gillnets/ longline gears. Total length of the sailfish was measured from the tip of the snout to the extended tip of the caudal fin. Total weight of individual fish was gauged to the nearest gram with an electronic balance after the removal of excess water from surface of the body. Salient morphometric and meristic characters were also measured (cm). Identification of species was made based on FAO Species Identification Sheets [12] . The length-weight relationship (LWR) was estimated by using the equation W ARTICLE INFO ABSTRACT Article history: Received 4 January 2012 Received in revised form 27 January 2012 Accepted 28 February 2012 Available online 28 April 2012 Keywords: Istiophorus platypterus Morphometric characters Length-weight relationship Objective: To obtain the morphometric characters and to determine the length-weight relationship for the sailfish captured off from Parangipettai, Tamil Nadu, Southeast coast of India. Methods: Samples of the sailfish were collected from the landing centre of this region during July 2010 to June 2011 using longline, gillnet and handline through commercial vessels. Salient morphometric and meristic characters were also measured (cm). Results: The total length recorded in the present study was ranged between 92 and 385 cm (mean 244.30暲15.08). The I dorsal fin base was varied from 18 to 145 cm (mean 98.40暲3.21); I dorsal ray fin height from1.4 to 21 cm (mean 10.30暲0.30); last ray fin length from 0.9 to 16 cm (mean 8.30暲0.05) and the highest ray length from 28.2 to 126 cm (mean 85.60暲2.15). The linear regression analysis was also executed to study the length-weight relationship; the ‘r’ value for the sailfish from this region was found to be 0.986 6 and the regression equation Log W= -5.4431 L 3.007 . Conclusions: In the present study, the slope value (b) was in the expected ‘3’ that indicates a fish becomes more slender as it increases in length. Further the slope value which is greater than 3 denoting stoutness or allometric growth. However, deviation from isometric growth is often observed, as most fish change their body shape as they grow. Contents lists available at ScienceDirect