Diversity in reproductive traits of arapaima (Arapaima spp., Müller, 1843) in Amazonian várzea floodplains: Conservation implications

Abstract

1. Understanding the reproductive ecology of freshwater fishes is essential to minimize the losses in global freshwater biodiversity but is often limited in data-poor regions, such as tropical floodplain ecosystems. Specifically, the study investigated whether size at first sexual maturation and nesting features for arapaima vary within and across regions in the floodplain of the Amazon River. 2. Data were collected at several sites in the Lower Amazon with varying arapaima densities and fishing practices. Female gonads were examined from commercial catch to calculate total length of first sexual maturation (L 50 ). Nest features were surveyed in the field. The size at first maturation and nest features (i.e. nest morphology, habitat, and density) were compared among sites with different population densities in the Lower Amazon and among estimates drawn from the literature for other regions. 3. In the Lower Amazon, L 50 showed significant variation between high-density (139 cm) and other sites (~168 cm). Overall variation in L 50 estimates for arapaima range from 139 cm in the Lower Amazon to 207 cm in the Upper Amazon in Peru. Nests in different regions show variation among certain nest features and a positive relationship between nest density and arapaima population density. In the Lower Amazon, 90% of nests were found under woody vegetation.4. The results show considerable diversity in size at first maturity and nesting features for arapaima. This suggests that there may be multiple evolutionarily significant units or species, even within the study area. This study also illustrates the importance of forest cover to arapaima spawning. Furthermore, different nesting morphologies were found at different sites. There are meaningful variations in arapaima reproductive behaviour, both locally and basin-wide, that require further study as they have implications for effective management and conservation initiatives.

Morphology of the Amazonian Teleost Genus Arapaima Using Advanced 3D Imaging

“…ranges from 137 to 207 cm depending on geographical site (Gurdak et al, 2019). At this length the females are approximately 5 years old, (Godhino et al, 2005), so our Specimen One was a mature adult.…”

“…In years when they spawn, they often have multiple batches which reduce the risk of clutch failure (Queiroz, 2000). However as arapaima are partial spawners, they never have an empty ovary (Gurdak et al, 2019). With the start of the rising water season, reproductive activity begins and males and females pair off (Queiroz, 2000).…”

“…The males build nests which are different in different regions. In the Lower Amazon, 90% of nests were found under woody vegetation (Gurdak et al, 2019). The males are responsible for caring for the young for approximately 4 months after breeding (Queiroz, 2000;Castello et al, 2011).…”

Cytogenetics, genomics and biodiversity of the South American and African Arapaimidae fish family (Teleostei, Osteoglossiformes)

“…The natural distribution of these fishes covers a large part of the Brazilian Araguaia–Tocantins and Amazon River basins [ 16 , 17 ]. They live preferentially in lentic environments such as floodplains and lakes, with significant sedentary behavior [ 18 , 19 ], displaying complex reproductive strategies, including nest building and a high level of parental care [ 20 , 21 ]. Being one of the largest freshwater fishes of the planet, with individuals measuring up to 4 m in length, they have been subjected to extensive fishery activities for years [ 6 ].…”

GnRHa implants and size pairing effects on plasma and cephalic secretion sex steroids in Arapaima gigas

“…Arapaima gigas is gonochoristic and iteroparous with fish reaching first sexual maturity after three to five years of age (Godinho et al, 2005;Gurdak et al, 2019). In their Amazonian habitat, spawning occurs year round peaking in the rainy season from December to May (Castello, 2008;Núñez et al, 2011).…”