Data-limited stock assessment of two horse mackerel species (Trachurus mediterraneus and T. trachurus) from the Mediterranean coast of Turkey

Abstract

A preliminary assessment of stock size and status of Trachurus mediterraneus and T. trachurus species were investigated via virtual population and yield prediction analyses using onboard collected length-frequency data from Northeastern Mediterranean. The length-frequency based VBGF parameters and growth performance index were L∞=28 cm, k=0.62, t0=0.58, tanc=0.52 and Φ′=2.69 for T. mediterraneus and L∞=27.46 cm, k=0.54, t0=0.49, tanc=0.41 and Φ′=2.61 for T. trachurus. Trawl-type selectivity and maturity ogives were 16.73 and 19.2 cm TL for T. mediterraneus, and 17.59 and 19.8 cm TL for T. trachurus, respectively. The virtual population analysis of T. mediterraneus resulted that the minimum and maximum fishing mortalities were 0.02 and 1.09 yr −1 for the mid-length groups for 10.5 and 24.5 cm, respectively. The minimum and maximum fishing mortality of T. trachurus were 0.0 and 0.89 yr −1 at the size of 25.5 and 27.5 cm, respectively. Biological reference points of T. mediterraneus point out that the current fishing mortality (FCurr=1.62) is lower than the fishing mortality of FMSY, and the current exploitation rate (ECurr=0.63) is lower than the reference point target benchmarks E0.5 and EMSY, showing underexploited status. The current fishing mortality (FCurr=0.76) in T. trachurus was observed to be lower than the fishing mortality for the MSY (FMSY), and the current exploitation rate (ECurr=0.46) was lower than E0.5 and EMSY, indicating currently underemployed status.