Aquaculture Research. 2020;00:1–10. wileyonlinelibrary.com/journal/are | 1 © 2020 John Wiley & Sons Ltd 1 | INTRODUCTION Brazilian oyster culture is concentrated in the state of Santa Catarina, which represents only 8% of the coastal line and yet accounts for 90% of total national production. This is due to an existing techno- logical package for the Pacific oyster Crassostrea gigas culture, which was introduced in the state in 1987 (Melo et al., 2010). Crassostrea gigas, however, is restricted to cold seawater temperature areas (Poli, 2004). Thus, the expansion of oyster farming in Brazilian trop- ical waters is linked to the domestication and the development of technological basis for native species (Legat, et al., 2017). The mangrove oyster, Crassostrea gasar (= Crassostrea brasiliana), inhabits most of the Brazilian coast, from the state of Pará to Santa Catarina (Melo et al., 2010), and is commonly found forming clusters in the mangrove ecosystem (Nascimento, 1991). Among indigenous oysters, C. gasar is the most cultivated species because it reaches greater size than Crassostrea rhizophorae (Christo & Absher, 2006) and presents similar growth to C. gigas in Europe and to Crassostrea virginica in the United States of America (Legat, et al., 2017). As reproduction is one of the most important physiological pro- cesses in the life cycle of any bivalve (Enríquez-Díaz et al., 2009), the farming of oysters has led to many different studies being performed in various locations to better understand their annual reproductive cycles. A more thorough understanding of these reproductive cycles allows farmers to better determine the optimal moments for har- vesting, with the aim of obtaining oysters with a higher meat weight before spawning and also seed collection. Despite the environmental and economic importance of the Brazilian mangrove oyster, few studies have been conducted to evaluate its reproductive cycle. To the best of our knowledge, only two studies using standard histological techniques have previously been performed in field in Brazil's South Region (Castilho-Westphal Received: 26 May 2020 | Revised: 18 September 2020 | Accepted: 7 October 2020 DOI: 10.1111/are.14954 ORIGINAL ARTICLE Reproductive cycle of the mangrove oyster, Crassostrea gasar (Adanson, 1757), in tropical and temperate climates Jefferson Francisco Alves Legat 1,2 | Angela Puchnick-Legat 1,2 | Simone Sühnel 2 | Alitiene Lemos Moura Pereira 1 | Aimê Rachel Magenta Magalhães 3 | Claudio Manoel Rodrigues de Melo 2 1 Embrapa Tabuleiros Costeiros, Empresa Brasileira de Pesquisa Agropecuária, Aracaju, Brasil 2 Laboratório de Moluscos Marinhos, Universidade Federal de Santa Catarina, Florianópolis, Brasil 3 Núcleo de Estudos em Patologia Aquícola, Universidade Federal de Santa Catarina, Florianópolis, Brasil Correspondence Jefferson Francisco Alves Legat, Embrapa Tabuleiros Costeiros, Av. Beira Mar, 3250-Jardins, Aracaju-SE. CEP: 49040-490 Aracaju, SE, Brasil Email: jefferson.legat@embrapa.br Abstract The reproductive cycle of Crassostrea gasar oysters from a single origin (Federal University of Santa Catarina hatchery) was studied by culturing the species for 1 year in four distinct areas of Brazil; two of which were in tropical climates (02°44′S, 41°58′W; 02°47′S, 41°55′W) and two in temperate climates (26°28′S, 48°50′W; 27°35′S, 48°32′W). In each area, 20 individuals were collected each month for re- productive cycle analysis using standard histological techniques. Oysters cultivated in tropical climates demonstrated intermittent reproductive cycles, with individuals spawning throughout the year and rarely entering a resting stage. Oysters cultivated in temperate climates demonstrated spawning periods associated with increases in water temperatures, occurring in late spring and summer. Resting stages were clearly seen in samples from latitudes of 26 and 27 °S, with approximately 75% to 100% of the individuals in this stage between May and July. KEYWORDS Crassostrea gasar , mangrove oyster, reproductive investment, temperature