Abstract

Shellfish gathering is an artisanal activity and a means of family subsistence for several coastal communities along the Brazilian coast and Anomalocardia brasiliana is one of the main exploited mollusk species. This paper aimed to obtain information about the temporal distribution, growth, yield, and gonadosomatic index of the bivalve mollusk A. brasiliana in a natural stock to provide subsidies for the sustainable extraction of this resource. The study was carried out in an area of the Acaraú River estuary, on Volta do Rio Beach, municipality of Acaraú, Ceará, Brazil. Samples were collected monthly for one year at spring low tide, using the random squares method. Water and sediment temperature and salinity were measured in situ. Sediment samples were collected for granulometric analysis. The specimens were individually quantified, measured, and weighed. A total of 8,507 A. brasiliana specimens were sampled, and the highest density recorded was 2,534 individuals/m², whose longest shell length reached between 21 and 25 mm, while the mean meat yield was 12.42%. The means of biometric variables of individuals showed significant differences during the sample period. Frequency histograms evidenced the presence of adult and juvenile individuals, showing a continuous reproductive cycle in the studied natural stock. These results can assist the sustainable shellfish gathering activity on Volta do Rio Beach. We recommend that A. brasiliana is above 20 mm in length to be captured and the reduction in the capture effort from April to September, when the highest density of juveniles was observed, to guarantee the sustainability of this stock.

Keywords:
Shellfish gathering; Fisheries Resource; Fisheries regulation.

Resumo

A mariscagem é uma atividade artesanal e meio de subsistência familiar de diversas comunidades litorâneas ao longo da costa brasileira, sendo Anomalocardia brasiliana uma das principais espécies de molusco exploradas. Esse trabalho objetivou obter informações sobre a distribuição temporal, crescimento, rendimento e o índice gonadossomático do molusco bivalve A. brasiliana em um estoque natural a fim de fornecer subsídios para a extração sustentável deste recurso. O estudo foi realizado em uma área do estuário do rio Acaraú, na Praia Volta do Rio, município de Acaraú, Ceará, Brasil. As coletas foram realizadas mensalmente durante um ano na maré baixa de sizígia, utilizando o método dos quadrados aleatórios. A temperatura da água, do sedimento e a salinidade foram aferidas in situ. Foram coletadas amostras de sedimento para análise granulométrica. Os espécimes foram quantificados, mensurados e pesados individualmente. Foram amostrados um total de 8.507 exemplares de A. brasiliana, a maior densidade registrada teve 2.534 indivíduos/m², aqueles com maior comprimento de concha tinham entre 21 e 25 mm, o rendimento da carne apresentou um valor médio de 12,42%. As médias das variáveis biométricas dos indivíduos apresentaram diferenças significativas durante o período amostral. Os histogramas de frequência evidenciaram a presença de indivíduos adultos e juvenis, indicando um ciclo reprodutivo contínuo no estoque natural estudado. Estes resultados auxiliarão no exercício da mariscagem sustentável na praia da Volta do Rio. Recomenda-se a captura de A. brasiliana com comprimento acima de 20 mm e a redução do esforço de captura nos meses de abril a setembro, período em que foi observada a maior densidade de juvenis, a fim de garantir a sustentabilidade desse estoque.

Palavras-chave:
Mariscagem; Recurso Pesqueiro; Regulamentação pesqueira.

Introduction

One of the oldest practices of artisanal fishing is shellfish gathering - extraction of bivalve mollusks - dating back to the prehistoric period when the first civilizations used these organisms as a bargaining chip.(¹1 Monteles JS, Funo ICSA, Castro TCS, Viana DCP, Conceição FS, França VL. Percepção socio-ambiental das marisqueiras no município de Raposa, Maranhão, Brasil. Revista Brasileira de Engenharia de Pesca. 2009; 4(2): 34-45. https://doi.org/10.18817/repesca.v4i2.141
https://doi.org/10.18817/repesca.v4i2.14... ) Shellfish gathering is an extractive activity carried out mainly by women called shellfish gatherers, and they extract mollusks from the natural environment using household items, such as spoons and other varied paraphernalia.(²2 Silva-Cavalcanti JS, Costa MF. Fisheries in Protected and Non-Protected Areas: Is it Different? The Case of Anomalocardia Brasiliana at Tropical Estuaries of Northeast Brazil. Journal of Coastal Research. 2009; 56: 1454-1458. Disponível em: https://www.jstor.org/stable/25738030
https://www.jstor.org/stable/25738030... ,³3 Souto FJB, Martins VS. Conhecimentos etnoecológicos na mariscagem de moluscos bivalves no manguezal do Distrito de Acupe, Santo Amaro - BA. Biotemas. 2009;22(4): 207-218. https://doi.org/10.5007/2175-7925.2009v22n4p207
https://doi.org/10.5007/2175-7925.2009v2... ,⁴4 Santana CG. As percepções ambientais de pescadores e marisqueiras acerca da divisão sexual de trabalho na pesca em Pirambu/SE. Ambivalências. 2014;2(3): 86-105. https://doi.org/10.21665/2318-3888.v2n3p86-105
https://doi.org/10.21665/2318-3888.v2n3p... ,⁵5 Mottola LSM, Schork G, Pino JRF, Romero RM, Araújo DM. Conhecimento local e pesca de maçunim (Anomalocardia brasiliana) no sistema estuarino-lagunar do Roteiro, Alagoas - Brasil. Gaia Scientia. 2020;14(3): 92-107. https://doi.org/10.22478/ufpb.1981-1268.2020v14n3.52220
https://doi.org/10.22478/ufpb.1981-1268.... ) Shellfish collection occurs along the entire Brazilian coast.(⁶6 Nishida AK, Nordi N, Alves RRN. Abordagem etnoecológica da coleta de moluscos no litoral paraibano. Revista Tropical Oceanography. 2004;32(1): 53-68. https://doi.org/10.5914/tropocean.v32i1.5034
https://doi.org/10.5914/tropocean.v32i1.... )

Among the main species collected is Anomalocardia brasiliana (Linnaeus, 1767), a bivalve mollusk of the family Veneridae, found naturally on the Brazilian coast with different local popular names such as marisco-pedra, vôngole, berbigão, and búzio, among others.(⁷7 Denadai MR, Arruda EP, Domaneschi O, Amaral ACZ. Veneridae (Mollusca, Bivalvia) from the north coast of São Paulo State, Brazil. Biota Neotropica. 2006;6(3): 1-34. https://doi.org/10.1590/S1676-06032006000300011
https://doi.org/10.1590/S1676-0603200600... ) The venerid A. brasiliana is euryhaline and eurythermic with wide geographic distribution from the West Indies (Antilles) to Brazil and Uruguay.(⁸8 Boehs G, Absher TM, Cruz-Kaled AC. Ecologia populacional de Anomalocardia brasiliana (Gmelin, 1791) (Bivalvia, Veneridae) na Baía de Paranaguá, Paraná, Brasil. Boletim do Instituto de Pesca. 2008;34(2): 259-270.,⁹9 Rios EC. 2009. Compendium of Brazilian Sea Shells. Rio Grande, Evangraf; 2009, 668p.) This species is adapted to a wide variety of habitats such as coves, bays, mouths of estuaries, tidal marshes, and unvegetated tidal flats, where it lives buried superficially in sediment, mainly sandy-muddy sediments.(⁸8 Boehs G, Absher TM, Cruz-Kaled AC. Ecologia populacional de Anomalocardia brasiliana (Gmelin, 1791) (Bivalvia, Veneridae) na Baía de Paranaguá, Paraná, Brasil. Boletim do Instituto de Pesca. 2008;34(2): 259-270.,¹⁰10 Rodrigues AML, Borges-Azevedo CM, Henry-Silva GG. Aspectos da biologia e ecologia do molusco bivalve Anomalocardia brasiliana (Gmelin, 1791) (Bivalvia, Veneridae). Revista Brasileira de Biociências. 2010;8(4): 377-383.)

However, the disorderly exploitation of the bivalve A. brasiliana throughout the year with predatory techniques has compromised the stocks of this mollusk in several regions of the Brazilian coast.(¹¹11 Nishida AK, Nordi N, Alves RRN. Aspectos socioeconômicos dos catadores de moluscos do litoral paraibano, nordeste do Brasil. Revista de Biologia e Ciência da Terra. 2008;8(1): 207-215.,¹²12 Silva-Cavalcanti JS, Costa MF. Fisheries of Anomalocardia brasiliana in Tropical Estuaries. Pan-American Journal of Aquatic Sciences 2011, 6(2): 86-99) In Brazil, most extractive fisheries stocks do not have specific rules and regulations for the management of A. brasiliana.(¹³13 Oliveira AS, Andrade LHA. Análise da evolução do setor pesqueiro de Pernambuco. Arquivos de Ciências do Mar. 2018;51(2): 27-43. https://doi.org/10.32360/acmar.v51i2.31362
https://doi.org/10.32360/acmar.v51i2.313... )

Thus, studies on the population dynamics of the species, describing its distribution, biomass, and environmental interactions in estuarine areas of Northeast Brazil, have been developed, such as the research by Araújo and Rocha-Barreira,(¹⁴14 Araújo MLR, Rocha-Barreira, CA. Distribuição espacial de Anomalocardia brasiliana (Gmelin, 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim Técnico Científico. 2004;12(1):11-21.) Rodrigues, Maia, Medeiros, and Henry-Silva,(¹⁵15 Rodrigues Maia AML, Medeiros E, Henry-Silva GG. Distribution and density of the bivalve Anomalocardia brasiliana in the estuarine region of Northeastern Brazil. Brazilian Journal of Biology. 2018;78(1): 32-40. https://doi.org/10.1590/1519-6984.02316
https://doi.org/10.1590/1519-6984.02316... ) and Silva-Cavalcanti and Costa.(¹²12 Silva-Cavalcanti JS, Costa MF. Fisheries of Anomalocardia brasiliana in Tropical Estuaries. Pan-American Journal of Aquatic Sciences 2011, 6(2): 86-99) The state of Ceará has no studies that show a decrease in the size of the bivalve A. brasiliana related to overfishing or environmental impacts. This lack of data on the real situation of the stocks and the absence of studies could harm the sustainability of this resource and, consequently, the shellfish gathering activity in the region.

Therefore, this study aimed to obtain information on the temporal distribution, growth, yield, and gonadosomatic index of the bivalve mollusk A. brasiliana in a natural stock on Volta do Rio Beach on the west coast of Ceará, Brazil, to provide subsidies for sustainable extraction of this resource.

Material and methods

Study area

The study was carried out in an area of the Acaraú River estuary on Volta do Rio Beach, located in the municipality of Acaraú, Ceará, Brazil. Collections were carried out in a stock of A. brasiliana (02°51′28″ S and 039°57′10″ W), reported by shellfish gatherers (personal communication) (Figure 1).

Field procedures

Specimens of A. brasiliana were collected monthly from January to December 2015, during spring low tide. The random square method was used during the collections to capture and pack the animals, as described by Araújo and Rocha-Barreira.(¹⁴14 Araújo MLR, Rocha-Barreira, CA. Distribuição espacial de Anomalocardia brasiliana (Gmelin, 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim Técnico Científico. 2004;12(1):11-21.) The abiotic variables, water and sediment temperature, and salinity were measured in situ using a thermohygrometer and a refractometer, respectively. The regional rainfall was obtained from the Fundação Cearense de Meteorologia e Recursos Hídricos(¹⁶16 FUNCEME - fundação cearense de metereologia e recursos hídricos. 2015. Calendário de chuvas. Disponível em: http://www.funceme.br/app-calendario/anual/municipios/maxima/2015
http://www.funceme.br/app-calendario/anu... ) website.

Three sediment samples were collected monthly using a cylindrical PVC sampler (core), according to the methodology used by the Monitoring Protocol for Estuarine Benthic Ecosystems.(¹⁷17 Turra A, Denadai MR. (Orgs.). Protocolos para o monitoramento de habitats bentônicos costeiros - Rede de Monitoramento de Habitat Bentônicos Costeiros - ReBentos [online]. São Paulo, Instituto Oceanográfico da Universidade de São Paulo, 2015; 248p. Disponível em: https://goo.gl/C24V7V
https://goo.gl/C24V7V... ) The granulometric analysis of the sediment was carried out using the sieving and pipetting methodology.(¹⁸18 EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária. Manual de métodos de análise de solo. 2ed. Rio de Janeiro, Centro Nacional de Pesquisa de Solos, 1997; 212p.)

Laboratory procedures

The collected specimens were quantified in the laboratory and immersed in a solution of magnesium chloride (MgCl₂.6H₂O) for 10 minutes to anesthetize them. Subsequently, the morphometric variable shell length was measured using a digital caliper with a 0.05-mm precision, according to Gosling.(¹⁹19 Gosling E. Bivalve molluscs: Biology, ecology and culture. UK, Fishing News Books. 2003; 455p.) The total weight, soft tissue (body without shell) weight, shell weight, and gonad weight were obtained using a precision scale. The gonadal tissue of each individual was dissected following Rocha-Barreira and Araújo.(²⁰20 Rocha-Barreira CA, Araújo MLR. Ciclo reprodutivo de Anomalocardia brasiliana (Gmelin 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim do Instituto de Pesca. 2005; 31(1): 9-20.)

Statistical analysis

The fresh soft parts weight yield (Y) was estimated for each month, using the equation: R = Wb × 100/Wt, where Wb is the soft part weight and Wt is the total weight. The gonadosomatic index (GSI) was expressed by the formula GSI = (gonad weight/total weight) * 100.

One-way analysis of variance (ANOVA) was used to compare the temporal variation in density, weight, size, and yield of A. brasiliana over the twelve months of sampling.(²¹21 Underwood AJ. Experiments in ecology - their logical design and interpretation using analysis of variance. New York, NY: Cambridge University Press, 1997. https://doi:10.1017/CBO9780511806407.
https://doi:10.1017/CBO9780511806407... ) Tukey’s test of multiple comparisons was used when differences at a 5% significance level (p<0.05) between the means were detected. Frequency histograms for the size (shell length) were plotted, interpreted, and analyzed to determine population parameters such as growth, recruitment, and mortality.(²²22 Gayanilo FCJ, Pauly D (Eds.). The FAO-ICLARM Stock Assessment Tools (FiSAT) Reference Manual. FAO Computerized Information Series (Fisheries). No. 8. Rome, FAO, 1997. 262 p.) The number of classes was determined according to the formula by Sturges: Vi = A/K, where Vi is the interval of classes, A is the range of the variable, and K is the number of classes calculated by the formula 1 + (3.32 log n), where n is the total number of individuals.

Biological data on density, shell length, soft tissue weight, gonad weight, yield, and the gonadosomatic index were compared and correlated with the environmental parameters obtained in the sampling period. The program STATISTICA for Windows^® version 7.0 was used in all analyses.

Results and discussion

A total of 8,507 specimens of A. brasiliana were sampled during the study period. The density of A. brasiliana showed a significant difference (p<0.05) between the studied months, showing an increase in the number of individuals from May, remaining high until August (Figure 2).

Density decreased in the period of the highest rainfall of the year and with the lowest salinity values. According to data from FUNCEME,(¹⁶16 FUNCEME - fundação cearense de metereologia e recursos hídricos. 2015. Calendário de chuvas. Disponível em: http://www.funceme.br/app-calendario/anual/municipios/maxima/2015
http://www.funceme.br/app-calendario/anu... ) the highest rainfall of the year was 414.4 mm in April and the study recorded the lowest salinity (25). The highest salinity (48) coincided with the rainfall index of zero, referring to November (Table 1).

A. brasiliana tolerates a range of minimum salinity of 15 and a maximum of 45.(²³23 Rodrigues Maia, AML, Medeiros EL, Silva GHG. Effect of salinity on bivalve survival Anomalocardia brasiliana (Gmelin, 1791). Scientia Agraria Paranaensis. 2017;16(4): 495-499.) The values presented in this study showed that the months of high rainfall, that is, February, March, and April 2015, had a decrease in salinity and a reduction in A. brasiliana density. This reduction in the population of bivalves in the studied natural stock was probably a consequence of a decrease in salinity, leading to the mortality of individuals. Rodrigues Maia, Medeiros, and Henry-Silva(¹⁵15 Rodrigues Maia AML, Medeiros E, Henry-Silva GG. Distribution and density of the bivalve Anomalocardia brasiliana in the estuarine region of Northeastern Brazil. Brazilian Journal of Biology. 2018;78(1): 32-40. https://doi.org/10.1590/1519-6984.02316
https://doi.org/10.1590/1519-6984.02316... ) carried out a study on Barra and Pernambuquinho beaches in an estuarine region of the semi-arid region of Rio Grande do Norte and observed a direct relationship between rainfall and density. The authors reported that the month of highest rainfall and, therefore, the highest supply of fresh water into the estuary, showed lower mean density values of A. brasiliana.

The mean water temperature at the collection sites throughout the sampling period was 29 °C (Table 1). In contrast, the mean sediment temperature for the same period was 33.2 °C (Table 1). However, the variables water temperature and sediment temperature were not determining factors to explain the temporal distribution of bivalves on the bank under study. Belém, Moura, and Henry-Silva(²⁴24 Belém TP, Moura RST, Henry-Silva GG. Distribuição e densidade do bivalve Anomalocardia brasiliana em praias do Rio Grande do Norte durante um período de pluviosidade atípica. Biotemas. 2013; 26(1):109-122. https://doi.org/10.5007/2175-7925.2013v26n1p109
https://doi.org/10.5007/2175-7925.2013v2... ) observed no influence of water temperature on the distribution of A. brasiliana. According to the ANOVA results, the shell length of A. brasiliana varied significantly (p<0.05) relative to the sampling period. Individuals with the longest shell length were collected in January, February, and March, with sizes between 21 and 25 mm (Figure 3).

The frequency histogram (Figure 4) allows the identification of adult individuals with shell lengths above 20 mm and juvenile individuals with shell lengths between 12.9 mm and 17.9 mm(²⁰20 Rocha-Barreira CA, Araújo MLR. Ciclo reprodutivo de Anomalocardia brasiliana (Gmelin 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim do Instituto de Pesca. 2005; 31(1): 9-20.,²⁵25 Lavander HD, Cardoso Júnior LO, Oliveira R, Silva Neto SR, Galvez AO, Peixoto SRM. Biologia reprodutiva da Anomalocardia brasiliana (Gmelin, 1791) no litoral norte de Pernambuco, Brasil. Revista Brasileira de Ciências Agrárias. 2011; 6(2): 344-350. https://doi.org/10.5039/agraria.v6i2a1139
https://doi.org/10.5039/agraria.v6i2a113... ) throughout the sampling period, which suggests values similar to the sizes of species already observed in the Northeast coast(²⁰20 Rocha-Barreira CA, Araújo MLR. Ciclo reprodutivo de Anomalocardia brasiliana (Gmelin 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim do Instituto de Pesca. 2005; 31(1): 9-20.,²⁵25 Lavander HD, Cardoso Júnior LO, Oliveira R, Silva Neto SR, Galvez AO, Peixoto SRM. Biologia reprodutiva da Anomalocardia brasiliana (Gmelin, 1791) no litoral norte de Pernambuco, Brasil. Revista Brasileira de Ciências Agrárias. 2011; 6(2): 344-350. https://doi.org/10.5039/agraria.v6i2a1139
https://doi.org/10.5039/agraria.v6i2a113... ) and a continuous reproductive cycle in the studied natural stock.(²⁵25 Lavander HD, Cardoso Júnior LO, Oliveira R, Silva Neto SR, Galvez AO, Peixoto SRM. Biologia reprodutiva da Anomalocardia brasiliana (Gmelin, 1791) no litoral norte de Pernambuco, Brasil. Revista Brasileira de Ciências Agrárias. 2011; 6(2): 344-350. https://doi.org/10.5039/agraria.v6i2a1139
https://doi.org/10.5039/agraria.v6i2a113... )

We suggest the capture of organisms above 20 mm. According to Ferreira Jr. et al.,(²⁶26 Ferreira Júnior AL, Bot Neto RL, Kolm HE, Absher TM. Relationship between reproductive cycle of Anomalocardia brasiliana (Mollusca: Veneridae) and the suspended particulate matter in the Paranaguá Estuarine Complex, Brazil. Pan-American Journal of Aquatic Sciences. 2015; 10(1): 44-54.) the reproductive rate of A. brasiliana decreases in larger and older organisms, not compromising the sustainability of the population when exploited, as it would reduce intraspecific competition for food and space for juveniles that are structuring in the environment. According to Luz and Boehs,(²⁷27 Luz JR, Boehs G. Reproductive cycle of Anomalocardia brasiliana (Mollusca: Bivalvia: Veneridae) in the estuary of the Cachoeira River, Ilhéus, Bahia. Brazilian Journal of Biology. 2011;71(3): 679-686. https://doi.org/10.1590/S1519-69842011000400012
https://doi.org/10.1590/S1519-6984201100... ) the reproductive cycle of the species occurs continuously, with less frequency of gamete release in the rainy season.

A higher expressiveness of organisms with shell lengths lower than 7 mm was observed in May 2015. According to Rodrigues Maia, Medeiros, and Henry-Silva,(¹⁵15 Rodrigues Maia AML, Medeiros E, Henry-Silva GG. Distribution and density of the bivalve Anomalocardia brasiliana in the estuarine region of Northeastern Brazil. Brazilian Journal of Biology. 2018;78(1): 32-40. https://doi.org/10.1590/1519-6984.02316
https://doi.org/10.1590/1519-6984.02316... ) a high entry of young individuals into A. brasiliana populations demonstrates continuous recruitment. The size of the population structure of A. brasiliana can be regulated by the availability of resources that support the population and the degree of overlap with other species of the same ecological and trophic guilds.(²⁸28 Riera R, Pérez O, Álvarez O, Simon D, Díaz D, Monterroso O, Núñez J. Clear regression of harvested intertidal mollusks. A 20-year (1994-2014) comparative study. Marine Environmental Research. 2016;113: 56-61. https://doi:10.1016/j.marenvres.2015.11.003.
https://doi:10.1016/j.marenvres.2015.11.... ,²⁹29 Magalhães L, Freitas R, Montaudouin X. Cockle population dynamics: recruitment predicts adult biomass, not the inverse. Marine Biology. 2016; 163(16): 1-10. https://doi.org/10.1007/s00227-015-2809-3
https://doi.org/10.1007/s00227-015-2809-... )

The analysis of variance also showed significant differences (p<0.05) for gonad weight during the sample period and peaked between January and March 2015 (Figure 5). Similar behavior was observed for the gonadosomatic index and the sampling period (p<0.05) (Figure 6).

Gonad weight and the gonadosomatic index tended to decrease gradually from April and remained reduced until September, showing the lowest values from May to August, which evidences a possible release of gametes. A study on the reproductive cycle of A. brasiliana on Canto da Barra Beach, Fortim - Ceará, Brazil, identified two periods of gamete release: the first from July to October and the second from February to April.(²⁰20 Rocha-Barreira CA, Araújo MLR. Ciclo reprodutivo de Anomalocardia brasiliana (Gmelin 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim do Instituto de Pesca. 2005; 31(1): 9-20.) According to Silva, Caroslfeld, and Gálvez,(³⁰30 Silva GHG, Carolsfeld J, Gálvez AO. Gente da maré: aspectos ecológicos e socioeconômicos da mariscagem no nordeste brasileiro. Mossoró, EdUFERSA, 2014; 420p.) the same species may vary in its reproductive cycle depending on the different climate and environmental conditions to which individuals are subject.

The temporal analysis of meat yield showed variation for the entire sampled period. The meat yield (Y) of A. brasiliana presented a mean value of 12.42% in the sampled months (Figure 7). The highest mean value of Y was observed in January 2015 (16.05%), which is similar to what was recorded by Lavander et al.(²⁵25 Lavander HD, Cardoso Júnior LO, Oliveira R, Silva Neto SR, Galvez AO, Peixoto SRM. Biologia reprodutiva da Anomalocardia brasiliana (Gmelin, 1791) no litoral norte de Pernambuco, Brasil. Revista Brasileira de Ciências Agrárias. 2011; 6(2): 344-350. https://doi.org/10.5039/agraria.v6i2a1139
https://doi.org/10.5039/agraria.v6i2a113... ) in January 2009 on the north coast of Pernambuco, with a value of 16.73% (±1.97%). According to Rebelo, Amaral, and Pfeiffer,(³¹31 Rebelo MF, Amaral MCR, Pfeiffer WC. Oyster condition Índex in Crassostrea rhizophorae (Guilding, 1828) from a heavy-metal polluted Coastal Lagoon. Brazilian Journal of Biology. 2005; 65(2): 345-351. https://doi.org/10.1590/S1519-69842005000200019
https://doi.org/10.1590/S1519-6984200500... ) the high values of Y can show gonads full or partially full of gametes, and, consequently, the reduction of these values can be associated with the release of gametes. Shellfish gatherers usually say that the seafood is “fat” during this period.(²⁵25 Lavander HD, Cardoso Júnior LO, Oliveira R, Silva Neto SR, Galvez AO, Peixoto SRM. Biologia reprodutiva da Anomalocardia brasiliana (Gmelin, 1791) no litoral norte de Pernambuco, Brasil. Revista Brasileira de Ciências Agrárias. 2011; 6(2): 344-350. https://doi.org/10.5039/agraria.v6i2a1139
https://doi.org/10.5039/agraria.v6i2a113... )

The granulometric analysis revealed that fine sand was the predominant sediment class, followed by coarse sand (Figure 8). The same was observed on Mangue Seco beach, PE, where A. brasiliana was found in sediments with a percentage above 90% of coarse and fine sand.(³²32 Rodrigues S, Lavander H, Oliveira L, Batista A,Oliveira I, Gálvez AO. Distribuição e abundância relativa do berbigão, Anomalocardia brasiliana, na praia de Mangue Seco, Pernambuco, Brasil. Arquivo de Ciências do Mar. 2013;46(2): 70-75. Disponível em: http://www.repositorio.ufc.br/handle/riufc/28991
http://www.repositorio.ufc.br/handle/riu... ) According to Araújo and Rocha Barreira,(¹⁴14 Araújo MLR, Rocha-Barreira, CA. Distribuição espacial de Anomalocardia brasiliana (Gmelin, 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim Técnico Científico. 2004;12(1):11-21.) sediment is an important factor for benthic fauna, as it provides shelter, food, and protection.

The correlation analysis showed that the higher the amount of clay, the lower the density of bivalves. Boehs, Absher, and Cruz-Kaled(⁸8 Boehs G, Absher TM, Cruz-Kaled AC. Ecologia populacional de Anomalocardia brasiliana (Gmelin, 1791) (Bivalvia, Veneridae) na Baía de Paranaguá, Paraná, Brasil. Boletim do Instituto de Pesca. 2008;34(2): 259-270.) reported the absence of the species in areas where the sediment had high proportions of silt and clay in Paranaguá Bay. Therefore, the type of sediment influences the survival of individuals because the animal is exposed to desiccation, salinity, and high temperatures in the thickest sediment. In contrast, the fine sediment provides less environmental stress and higher food availability.(¹⁴14 Araújo MLR, Rocha-Barreira, CA. Distribuição espacial de Anomalocardia brasiliana (Gmelin, 1791) (Mollusca, Bivalvia, Veneridae) na Praia do Canto da Barra, Fortim, Ceará, Brasil. Boletim Técnico Científico. 2004;12(1):11-21.) It is valid to assume that the sediment found favored the settlement and development of the bivalve A. brasiliana in the studied natural stock.

Conclusion

The studied natural stock of A. brasiliana showed variations in size, weight, yield, and the gonadosomatic index similar to those described in the literature for the species throughout the sample period. January, February, and March presented larger, heavier individuals with high yield and gonadosomatic index, whereas a decrease of these indicators was observed from April to September, evidencing a possible recruitment period. Thus, we recommend the capture of A. brasiliana specimens with a length above 20 mm and the reduction in the capture effort from April to September, when the highest density of juveniles was observed, to guarantee the sustainability of this stock. These results may help the sustainable shellfish gathering activity in natural stocks on the west coast of Ceará, Brazil.

Acknowledgments

To the Laboratory of Mangrove Ecology (Ecomangue) and its staff for supporting this research. To the Laboratory of Soil of the Federal Institute of Education, Science, and Technology of Ceará - campus of Sobral and its staff for making sediment analysis possible.

References

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