Biological characteristics and inter-annual changes of Saurida tumbil in spring in the Beibu Gulf, South China Sea

Abstract:

Using data from the spring fishing port samples and bottom trawl surveys in the Beibu Gulf, the biological characteristics and inter-annual changes of Saurida tumbil were investigated. The population structure of S. tumbil in the Beibu Gulf had a miniaturization trend - the average standard length (SL) and body weight (BW) decreased from 2008 to 2018, with ranges of 15.8~16.9 cm and 48.8~77.5 g, respectively. There were also temporal variations in SL and BW; the average values decreased by 6.5% and 34.5% from 2008 to 2018, respectively. The range of the allometric parameter b was 3.03~3.42, indicating that S. tumbil had positive allometric growth (b>3) in the Beibu Gulf in spring. Analysis of the inter-annual change in length at 50% maturity (L50) in females showed that the S. tumbil population maturated before the L50, decreasing 12.6% from 2008 (19.0 cm) to 2018 (16.6 cm). Compared to 2011 (18.6 cm), the 2015 female L50 reduced by 3.8% (17.9 cm). Fatness also declined from 2008 to 2018 (range: 1.09~1.29), as evidenced by consistent downward trends in the fatness samples from both fishing methods. However, fatness had an overall increasing trend with increasing SL.