Abstract
Portunus trituberculatus is an important invertebrate species distributed in the Yangtze Estuary. However, its biomass and enrichment have been affected seriously by ongoing human activity in recent decades. The length-based Bayesian biomass estimator (LBB) is a novel and potent method to estimate the stocks for most commercial fishes and invertebrates in offshore using only length and frequency data. In this study, the results showed that the ratio of current exploited biomass relative to unexploited biomass (B/B0) was smaller than relative biomass capable of producing maximum sustainable yields (BMSY/B0) after handling of the catches of the P. trituberculatus collected from the Yangtze Estuary in 2018 using the LBB method. Therefore, this evidence indicated that the biomass of the swimming crab was relatively low as a result of the overfishing in this water area and the catches of the crabs should be controlled at a reasonable level in the future. Meanwhile, LBB is a promising method providing a theoretical basis for the management and protection of fishery resources.
Highlights
The Yangtze Estuary and its adjacent areas are an important channel for material transportation and exchange between the Yangtze River, the East China Sea and the Yellow Sea [1]
This study presents the length-based Bayesian biomass estimator (LBB) method for the analysis of the carapace width of P. trituberculatus captured from the Yangtze Estuary
Due to its remarkable effect, stock enhancement has been gradually extended to the coastal areas of the country, due to which the biomass of the crabs increased significantly and it became the dominant species in the Yangtze Estuary and its adjacent areas again [2,22], which was in accord with the results published by Shen [23]
Summary
The Yangtze Estuary and its adjacent areas are an important channel for material transportation and exchange between the Yangtze River, the East China Sea and the Yellow Sea [1]. The runoffs from the Yangtze River continuously transport nutrients to the area, making the estuary a habitat and a baiting, fattening and breeding site for many commercial fishes and invertebrates. Portunus trituberculatus (Miers, 1876), an edible crab inhabiting the sandy or pebble seafloors throughout the majority of seawaters in China, is the perennial dominant species of invertebrates in the Yangtze Estuary [2]. The catch of P. trituberculatus in China had increased significantly from 130,000 tons in 1989 to 490,000 tons in 2018, among which the catch from the Yangtze Estuary and its adjacent areas accounted for about 50% [3]. The swimming crab, with high economic value, was an important breed of aquaculture. The aquaculture yield of the swimming crab revealed a trend of rapid growth since recorded from 2003, the proportion of which was about 25%
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