Growth and mortality parameters of Platycephalus indicus, Grammoplites scaber, and G. suppositus (Teleosti: Platycephalidae) in the southern coastal waters of Iran

Abstract

Population parameters of three dominant benthic fish (Bartail flathead, Spotfin flathead, and Rough flathead) were estimated during the period from April 2022 to October 2023; The specimens were caught as by-catch of shrimp bottom trawlers, and also in coastal stake nets. The b value of the total length and weight relationship for the Bartail flathead was 3.23 and for Spotfin and Rough flatheads were calculated as 3.33 and 3.29, respectively, which revealed a positive allometric growth pattern in all species. Von Bertalanffy's growth parameters including TL∞, K, and t0 were estimated at 56 mm, 0.5 (Y-1), and -0.27 for P. indicus; 40 mm, 0.6 (Y-1), and -0.25 for G. suppositus and 33 mm, 0.9 (Y-1), and -0.17 for G. scaber, respectively. The natural mortality (M) for the mentioned species was estimated (at 0.95, 1.17, and 1.61 per year), fishing mortality (F) was (1.16, 1.39, and 2.57 per year) and total mortality was (2.11, 2.56, and 4.18 per year), respectively. The exploitation coefficient (E) was estimated at 0.55 for the Bartail flathead, 0.54 for Spotfin flatheads, and 0.61 for the Rough flathead, which indicates the relatively high fishing pressure on these species in the region. To mitigate this pressure, it is recommended to reduce fishing efforts, install bycatch reduction devices on trawl nets, and increase monitoring of coastal stake nets in the region.