No 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

We examined catch compositions and vulnerability of target and bycatch species in two fishing gears, namely the bottom-set gillnet and collapsible crab trap, used in small-scale fisheries of Bandon Bay, Suratthani Province, Thailand. Both gears mainly target the blue swimming crab (BSC) Portunus pelagicus, and together contribute about half of Thailand’s annual BSC catch of around 2.5 thousand tonnes. Field sampling was conducted from January to November of 2018. Specimens from bottom-set gillnets and collapsible crab traps comprised 111 and 118 taxa, respectively. Of these, 26 and 27 crab species and 41 and 46 fish species were collected by gillnets and traps, respectively. The index of relative importance of BSC was higher in gillnets (48.8 ± 16.6%) than in traps (25.0 ± 15.5%), where another swimming crab (Charybdis affinis) was more common. Cluster analysis revealed that catch compositions were seasonal and differed between the two monsoonal seasons, i.e., northeast monsoon (October to February) and southwest monsoon (May to September), and the transition period (March and April). Potential impact from both fishing gears on various stocks was assessed by standard productivity and susceptibility analysis (PSA). Vulnerability scores of the BSC stock as the main target species suggested it was at moderate risk, as assessed by PSA. The impacts of both gears to stocks of the other species in Bandon Bay showed either low or moderate risk. Ten fish stocks, including two stingrays, six species of sole and two other bony fishes, were near the threshold of high risk from gillnet fishing.