Length-Weight Relationships (LWRs) of Fourteen Marine Pelagic Fish Species in the Southeastern Arabian Sea

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Length-Weight Relationships (LWRs) of Fourteen Marine Pelagic Fish Species in the Southeastern Arabian Sea K. M. Rajesh 1

&

Prathibha Rohit 1 & Subal Kumar Roul 2

Received: 9 August 2019 / Revised: 1 January 2020 / # Springer Nature Switzerland AG 2020

Abstract The length-weight relationships (LWRs) of fourteen marine pelagic fish species were determined in the southeastern Arabian Sea. Specimens were collected on weekly basis from two major fishing harbours (Mangalore and Malpe) along the Karnataka coast during 2017–2018. The fish were caught using wide variety of fishing gears such as trawlnets, purse seines, ring seines, gillnets and long lines. The estimated LWRs were highly significant (p < .001, r2 > 0.90) for all the species. The allometric coefficient b ranged from 2.7 to 3.4, falling within the expected ranges. The results of analysis of covariance (ANCOVA) revealed no significant difference (p < .005) in the LWRs between the sexes for all the species. The LWRs in most of the species were either positive allometric (b > 3) or negative allometric (b < 3) whereas few species such as Sardinella longiceps (male), Euthynnus affinis and Sphyraena obtusata (male and combined sex) exhibited isometric growth (b = 3). The study provides the basic biological information on the LWRs of fourteen commercially important pelagic fish species which will be useful as baseline information for further biological research in the region. Keywords Pelagic fish . Arabian Sea . Length-weight relationships . Allometric growth

Introduction The southeastern Arabian Sea is one of the prime areas in marine fish production of India. Among the maritime states, Karnataka contributes immensely to the marine fisheries of the country. The state has 300 km coastline, a shelf of about 25,000 km2 and historically known as the mackerel coast of India (Mohamed et al. 1998). The state recorded a maximum landing of 5.5 lakh tones during the year 2017 which contributed about 4.4% of the total marine fish landings of India and ranked fourth among the maritime states of the country (CMFRI 2018). Pelagic fishes dominated the marine fish landings, contributing about 65% of the total marine landings of the state (CMFRI 2018). Length-weight relationships (LWRs) is an important tool used to estimate the average weight of a known length group * K. M. Rajesh [email protected] 1

ICAR-Central Marine Fisheries Research Institute, Mangalore Research Centre, P.B. No. 244, Hoige Bazar, Mangaluru, Karnataka 575 001, India

2

Puri Field Centre, ICAR-Central Marine Fisheries Research Institute, Puri, Odisha 752 002, India

and conversion of length measurement into weight where the technical difficulty in measuring weight of the fishes exist particularly during field observation and on-board vessel (Moutopoulos and Stergiou 2002; Froese 2006; Froese et al. 2011). In addition, reproductive status of fish can be checked using their length-weight relationships (June et al. 2014; Park et al. 2016). In spite of the major contribution of pelagic fishery in th