Catch composition and risk assessment of two fishing gears used in small-scale fisheries of Bandon Bay, the Gulf of Thailand

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.

Catch assemblages in the small-scale trap fishery with relation to hydrographic features of a tropical bay in the Gulf of Thailand

“…Although the small-scale trap fishery in Bandon Bay targets the blue swimming crab, this fishery employs indiscriminate fishing gear, similar studies of the bay have reported that these trap nets catch roughly 100 species of aquatic animals [14,17]. However, the catch composition from bottom gill nets, another common fishing gear for blue swimming crab, usually includes more species than traps-as many as 150 taxa [36].…”

“…Fourteen (14) sites within the fishing ground of SSF in Bandon Bay were selected (Fig 1 ); once a month, 90 traps were taken from the fishers in each site. The traps were deployed for 12 h before retrieving.…”

“…Its area is 477 km 2 , with 120 km of coastline and a mean depth of approximately 2 m. Offshore tides are moderate and are amplified toward the inner part of the bay. The tidal range at the middle of the bay is about 0.6 m during neap tide and 2.1 m during spring tide [14]. The bay is governed by Asian-Australian monsoonal climate, having the southwest monsoon (SWM) between July and September, and the northeast monsoon (NEM) between November and March.…”

“…The bay bottom has highly varied substrates of mud, clay and sand, and a large mudflat extends about 2 km offshore [16]. Due to the bay's characteristics, it is home of at least 340 fishes and other aquatic animals; mollusks and crustaceans are particularly abundant, and support many SSF activities [14,17]. Moreover, Bandon Bay also supports intensive sea farming, especially of bivalve species such as blood cockle, green mussel and oysters [18].…”

Hydroacoustic survey on fish spatial distribution in the early impoundment stage of Yuwanghe Reservoir in southwest China

“…The status and the role of species in the community were classified according to their number and the weighted proportion of catches. Species with an index of relative importance (IRI) > 1,000 are defined as dominant, those with IRI between 100 to 1,000 are important species, those with IRI between 10 to 100 are common species, and those with IRI < 10 are occasional species (Jutagate and Sawusdee, 2022). On the basis of this criterion, topmouth gudgeon (Pseudorasbora parva) was the dominant species in the fish community, Carassius auratus and Culter alburnus were important species, and Micropercops swinhonis and Paramisgurnus dabryanus were common species (Table 1).…”