Selectivity of a fishing gear used in the catch of Anomalocardia flexuosa in the Northeast of Brazil

Abstract

A type of dredge was introduced as fishing gear along the extractive bank of Mangue Seco - PE from which the largest annual catch of Anomalocardia flexuosa in the world is extracted. This study was carried out with the objective of estimating the selectivity of the new fishing gear and quantitatively evaluating the length classes most compromised by the catches, especially considering 20 mm as the reference value. Specimens larger than this size are most likely to be mature. For the selectivity estimation, the methodology using codends (16 or 20 mm) and small meshed cover (2 mm) was used. To estimate the selectivity parameters, a logistic regression and the Bayesian approach were used. The transition between the state in which the specimen is invulnerable to the fishing gear and vulnerable occurs between 10 and 18 mm, using a 16 mm mesh, and using a 20 mm mesh, this transition is between 14 and 20 mm. Dredgers with 16 mm and 20 mm mesh compromise a large proportion of specimens smaller than 20 mm. If the intention is to protect this part of the population, measures such as total restriction of the 16 mm mesh and use of the 20 mm mesh should be necessary only in the months of less catching incidences, or increasing the mesh to 25 mm.

Rainfall effects on Anomalocardia flexuosa densities on the northeastern Brazilian coast using distributed lag models

“…Of course, large individuals are the most affected by the harvesting, but small individuals can also be affected by the use of fishing equipment. The use of dredges is quite widespread on site (Lima et al, 2020), and this may contribute to the mortality of individuals who escape, either by exposure to epibentonic predators or due to physical impact (Pezzuto et al, 2010;Eigaard et al, 2015), which may be more severe in small individuals who have more fragile shells. Therefore, both natural mortality and that caused by fishing affected small and large individuals to a greater degree, possibly covering up a seasonal pattern, as verified for the medium-sized group, which may have caused non-significant autocorrelation, which was presented in our results.…”

“…This is a traditional extractive region covering an area of approximately 2.9 km 2 . It is a tidal flat and has great influence due to its contribution of fresh water and nutrients from estuaries located to the South, at the mouth of the Timbó River, and to the north, at the Santa Cruz channel (Lima et al, 2020) (Figure 1). The beach line is two kilometers long, going from north to south along the coast, with shallow waters and small waves (Oliveira et al, 2014).…”

“…The first size class was small individuals up to 10 mm, which are of little interest for fishing. The second class was composed of sizes larger than 10 mm and smaller than 20 mm (medium-sized), which encompasses individuals that can already be caught (Lima et al, 2020). The third class, which has sizes equal to or greater than 20 mm, is the recommended size class for catching (Silva-Cavalcanti and Costa, 2011;Oliveira et al, 2014).…”

Distribuição vertical da Anomalocardia flexuosa (Linnaeus, 1767) (Bivalvia: Veneridae) na praia de Mangue Seco (Pernambuco, Brasil)

“…Nas praias arenosas, esse grupo é composto por espécies permanentes que normalmente têm distribuições agregadas (BROWN; MCLANCHLAN, 1990), sendo o filo Mollusca um dos mais difundidos neste tipo de ambiente (RUEDA et al, 2009). Várias espécies de moluscos são exploradas comercialmente nas praias arenosas, com destaque para os bivalves (SILVA-CAVALCANTI; COSTA, 2011;BELÉM et al, 2013;LIMA et al, 2020).…”