Population dynamics of mud crab, Scylla olivacea (Herbst, 1796) from the Sundarbans of Bangladesh

Abstract

The Sundarbans mangrove regions are the home of the mud crab (Scylla olivacea) business, as forest areas are potential places for random crab harvesting, trading, and exporting overseas seafood markets. Since the mud crab was being captured on a large‐scale in the wild for various purposes, estimation of population parameters were immediately done in terms of body weight and length‐frequency data collected from different locations in the forest of southwestern Bangladesh to understand the status of the stock. Recruitment pattern, growth parameters, mortality rates, and exploitation levels (E) were estimated to understand the population dynamics of S. olivacea. Asymptotic carapace widths (CW∝) were 14.70 and 14.18 cm, and growth co‐efficients (K) were 0.47 and 0.50 year–1 for male and female S. olivacea, respectively. The fishing mortalities were 2.32 and 1.13 year–1 and natural mortalities were 1.39 and 1.46 year–1 for males and females, respectively. Year‐round recruitment of this species takes place in the wild with a peak between June and November. The E for S. olivacea was found to be 0.63 for the male and 0.44 for the female. In summery, the stock of S. olivacea is found to be overexploited in the Sundarbans of Bangladesh. Therefore, mud crab resources should be taken into consideration under suitable fisheries management policies to conserve this national treasure in this delta. It is supposed that the findings will draw the attention of the scientists in the fields of aquatic biology, ecology, and management of the Sundarbans in restoring the mud crab population.

Biometry, Growth, and Recruitment Pattern of a Commercially Important Nereid polychaete, Namalycastis fauveli, from the East Coast of Bangladesh

“…Although the b-value was less than 3 in numerous studies [5,19,22] of polychaetes conducted around the world, b reached 3.52 in Armandia maculata (Opheliidae), 4.27 in Bithynia tentaculata (Bithyniidae), and 2.36 in Naticidae mesogastropod species [29]. In addition, the mud crab (Scylla olivacea), found in Bangladesh's Sundarbans mangrove, has b-values of 3.05 and 2.61 [40].…”

“…For example, the study area, habitat, season, etc., play pivotal roles in determining population. Due to higher temperatures and a greater abundance of food sources, northern hemisphere species usually have reproductive seasons limited to the spring and/or summer and, most crucially, show seasonal maturation, with substantially varied growth rates throughout the life cycle [40][41][42][43][44][45][46][47]. Seasonal growing peaks, shown in temperate species, may still not appear in tropical and subtropical environments, and breeding may occur year-round [48,49].…”

“…The P-cap is applied to assess the vulnerability of various sizes in a particular area at a certain time [40]. The P-cap of 0.25, indicated that 25.0% of the N. fauveli population, was subject to capture at 9.0 cm body length (Figure 7).…”

Assessing the Size-Structured Stock of the Swimming Crab Callinectes amnicola (Crustacea: Portunidae) in the Cross River, Nigeria

“…Mikpon et al (2020) also reported that most economically important aquatic resources, including crabs, are harvested by both industrial and artisanal fisheries in an unsustainable and uncontrollable manner. This excessive focus on the wild crab to support the stocking population can put undue pressure on the crab stock, resulting in overexploitation, reducing genetic diversity, and jeopardising this important resource (Zhang et al, 2021;Sakib et al, 2022). The Cross River crab fishery can be effectively managed through studies that reveal population dynamics.…”

“…The Cross River crab fishery can be effectively managed through studies that reveal population dynamics. Sakib et al (2022) found that recruitment pattern, growth, and mortality rate (total, fishing, and natural mortality) are the three most important factors contributing to fish population fluctuation. However, the importance of parameters such as longevity, exploitation rate, and catch probability to population dynamics cannot be overstated.…”