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

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

DIVERSIDADE DE PEIXES NA ZONA COSTEIRA DO ESTADO DO MARANHÃO A PARTIR DE DADOS DA PESCA ESPORTIVA

The state of Maranhão has a vast coastline that promotes the development of coastal recreational fishery, an activity that has attracted more and more fans in recent years. In this context, the objective of this work was to demonstrate the importance of sport fishing as an auxiliary source in monitoring the diversity of fish on the beaches of the metropolitan region of São Luís, Maranhão, through the monitoring of sport fishing tournaments, held in December 2018 on the beach do Olho d‟água and in July 2019, at Araçagi beach. The captured fish were stored in isothermal boxes containing ice and transported to the laboratory for taxonomic identification. 252 specimens were captured, belonging to 19 species, and distributed in 10 families. The family Sciaenidae was the most representative with 3 species. The predominant species were Conodon nobilis and Genyatremus luteus from the Haemulidae family, which together represented 39% of the specimens captured on the Olho d‟água beach and 24% on the Araçagi beach. The individuals of C. nobilis had an average weight of 29.4 ± 12.7 g and an average length of 12.3 ± 2.0 cm, with a curve of weight x length ratio represented by the equation PT = 0.034 CT2.6637 and R2 = 0, 67, with b = 2.67. While in G. luteus, the individuals had an average weight of 96.5 ± 82.2 g and an average length of 15.8 ± 4.4 cm, with a curve of the weight x length ratio represented by the equation: PT = 0.0145CT3.0999 and R2 = 0.81, with b = 3.09. The diversity of fish in beach fisheries can contribute to studies of fishery biology to support the development of management strategies and conservation of fish stocks.