Population Dynamics of the Caroun Croaker Johnius carouna (Cuvier, 1830) in Coastal Fishing Ground in the Middle Gulf of Thailand

Abstract

The stock status of coastal species is currently of high concern among the people. In the Gulf of Thailand, Croakers are important economic species commonly found in the coastal fishing ground, especially in Nakhon Si Thammarat province. The population dynamics of the Caroun croaker, Johnius carouna (Cuvier, 1830), was investigated using length-frequency distribution data collected from February 2019 to January 2020. The length-weight relationship equation suggested that J. carouna is isometric growth. The asymptotic total length (L∞) and curvature growth (K) were 22.28 cm and 0.72 year-1, respectively. Based on L∞ and K, the total mortality rate during the study period was estimated at 3.66 year-1; natural mortality and fishing mortality rates were estimated at 1.62 and 1.74 year-1, respectively. While biological data revealed that matured size was 15.3 cm, the fishing data suggested that the average catch size (15.12 cm) was slightly smaller than the matured size. The exploitation rate was 0.52 year-1. The result from this research suggests that current fishing pressure is slightly high. This study suggested that increasing catch size by increasing mesh size of gillnets seems to be a better solution to improve J. carouna stock in Thasala fishing ground in the future. HIGHLIGHTS The first report onJohnius carouna fishery biology in coastal fishing ground in the middle Gulf of Thailand Johniuscarouna is an isometric fish Matured size of Johniuscarouna is 15.3 cm Current fishing pressure on Johniuscarouna is slightly high GRAPHICAL ABSTRACT