Length-weight relationships (LWR) of the most landed pelagic fish species Sardina pilchardus Walbaum, 1792 and Engraulis encrasicolus Linnaeus, 1758 in the Izmir Bay purse seine fishery were determined to reveal latest situation. Purse seine is a non-selective fishing gear compare to the other fishing gear such as gillnet or trammel net. For this reason, sampling all size individuals is very important to calculate mean length and other LWR parameters. In this study, seasonal LWR coefficient and minimum-maximum lengths were established as monthly basis. LWR of S. pilchardus and E. encrasicolus were W = 0.0059L2.7930 (r² = 0.94) and W = 0.0019L3.4207, (r² = 0.87), respectively. Growth type of the S. pilchardus was found negative allometric whereas E. encrasicolus was positive allometric. A decrease of the mean total length of S. pilchardus has been considerable variable from 1994 to 2014 in Izmir Bay but with this study, it is observed that mean length of the sardine found near of 2006 value related to seasonal fishing pressure.
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