Growth, mortality, and reproduction of Tagelus plebeius (Bivalvia: Solecurtidae) in Southeast Brazil

Abstract

Tagelus plebeius (Lightfoot, 1786) is a stout razor clam that is economically exploited in several countries, including several local fisheries along the Brazilian coast. Despite its wide distribution and economic importance, there are few studies that have examined the population biology of this species. This study aimed to improve the current knowledge about the biology of T. plebeius by investigating its growth and mortality on a subtropical sandy beach in Southeast Brazil over a 1-year period. In addition, the reproduction of T. plebeius was analyzed through qualitative and quantitative histological analyses during the last 7 months of the study. The parameters of the von Bertalanffy growth function were estimated to be L ? = 74.14 mm, K = 0.52 year -1 , C = 0.47, and WP = 0.94. The instantaneous mortality rate (Z) was 2.16 year -1 , and the life span was 2.58 years. We confirmed variations (H = 651.35; P \ 0.05) in the shell length over the months of the study, and the recruitment was higher-but still low-in summer. Four cohorts were observed in the distribution of shell length frequencies. The sex ratio of the population was 1:1 during the study period, and a synchronism in gonadal development and spawning was found between males and females. The high mortality (Z) and low recruitment rates can be interpreted as reflecting that the population of T. plebeius is under a low restoration process and could be an indication that this species has an endangered status in the study area.

Distribution pattern, density and growth of the stout razor clam Tagelus plebeius in a South-west Atlantic estuarine system

“…The maximum lifespan of 27 years in the recent Mar Chiquita population is much higher than values reported for fossil shells from the same location (8 years, Isla & D'Andrea, 1993) and from different sites in Brazil, below 3 years at Enseada Beach (23°43′S 45°25′W) in São Sebastião (Abrahão et al , 2010), and at Camaroeiro Beach (23°S 45°W) in Caraguatatuba Bay (da Silva et al , 2015). However, those studies evaluated growth rate and maximum age using shell size frequency analyses (Abrahão et al , 2010; da Silva et al , 2015) and external growth rings (Isla & D'Andrea, 1993). Both methods are highly prone to underestimate age in long-lived species where annual growth increments may become quite small.…”

“…Holland & Dean, 1977a; Abrahão & Amaral, 1999; Lomovasky et al , 2006; this study), while populations associated with sandy and muddy-sandy sediments show lower densities (Abrahão et al , 2010; de Farias & Rocha-Barreira, 2012). The sediment characteristics could be an indicator of environmental stability and food availability for suspension feeding species, which are facilitated by fine sediments and high OMC (da Silva et al , 2015). Similarly, a higher growth index was associated to finer sand but higher OMC in different localities from Brazil (da Silva et al , 2015).…”

“…The sediment characteristics could be an indicator of environmental stability and food availability for suspension feeding species, which are facilitated by fine sediments and high OMC (da Silva et al , 2015). Similarly, a higher growth index was associated to finer sand but higher OMC in different localities from Brazil (da Silva et al , 2015). The sediment at all sites sampled in the present study was composed of >10% silt-clay, reaching 64% in some areas.…”

“…This suspension-feeding species (Holland & Dean, 1977a; Arruda et al , 2003) is a deep burrowing species that inhabits permanent burrows (up to 0.70 m depth) showing vertical movements through each semidiurnal tidal cycle, but not showing intertidal migration (Holland & Dean, 1977b). Current knowledge of T. plebeius biology and ecology is limited to a few localities in Argentina (Mar Chiquita coastal lagoon: Cledón et al , 2004; Lomovasky et al , 2005, 2006; Addino et al , 2010, 2016; Bahía Blanca estuary: Addino et al , 2015), Brazil (Canal do Calunga, Maceió: Viégas, 1982; São Sebastião: Abrahão & Amaral, 1999; Arruda et al , 2003; Abrahão et al , 2010; Cachoeira river estuary: Ceuta & Boehs, 2012; Ceara river estuary: de Farias & Rocha-Barreira, 2012; Caraguatatuba Bay: da Silva et al , 2015), and the USA (North Inlet estuary, Holland & Dean, 1977a, b).…”