Genetic diversity of tambaqui broodstocks in stock enhancement programs

Abstract

Natural populations of tambaqui (Colossoma macropomum) have significantly decreased in recent decades especially due to human extraction activities. So that the environmental impact may be reduced, the restocking of fish and increase in fish production are enhanced. Genetic evaluations using molecular markers are essential for this purpose. Current study evaluates the genetic variability of two tambaqui broodstocks used in restocking programs. Sixty-five samples (33 samples from broodstock A and 32 samples from broodstock B) were collected. DNA was extracted from caudal fin samples, with the amplification of four microsatellite loci: Cm1A11 (EU685307) Cm1C8 (EU685308) Cm1F4 (EU685311) and Cm1H8 (EU685315). Fourteen alleles in the stock of broodstock A were produced, five alleles for Cm1A11 locus (230, 255, 260, 270 and 276 bp), three alleles Cm1C8 (239, 260, and 273 bp), two alleles Cm1F4 (211 and 245 bp), four alleles for Cm1H8 (275, 290, 320 and 331 bp) and two unique alleles were found for Cm1A11 loci (alleles 270 and 276 bp) and Cm1H8 (alleles 275 and 331 bp). In broodstock B, ten alleles were produced, the same alleles of the first stock except for alleles 270 and 276 bp in Cm1A11 locus and 275 and 331 bp in Cm1H8 locus. Broodstock A revealed low frequency alleles in Cm1A11 loci, Cm1C8, Cm1F4 and Cm1H8, whereas broodstock B had no locus with low allelic frequency. Loci Cm1A11, Cm1C8 and Cm1H8 exhibited significant deficit of heterozygotes in both broodstocks, revealing changes in Hardy-Weinberg equilibrium. Genetic diversity between stocks was 0.1120, whilst genetic similarity was 0.894, with F ST rate = 0.05, and Nm = 3.93, indicating gene flow between the two broodstocks. Results show that broodstocks are genetically closely related, with no great genetic variability. Strategies such as a previous genetic analysis of breeding with its marking, use of a large Ne crossing between the most genetically divergent specimens, and the introduction of new genetic material to broodstocks may maximize genetic diversity and minimize inbreeding within the next generation.

Genetic diversity of Tambaqui (Teleostei - Characidae) broodstocks from Northern region of Brazil using microsatellite markers

“…The total number of alleles per locus ranged from five (Cm1C8, Cm1E3 and Cm1H8) to eight (Cm1A8), with sizes between 140 bp (Cm1A8) to 310 bp (Cm1E3). The number of alleles identified in loci Cm1A11, Cm1C8 and Cm1H8 was similar to that observed in two broodstocks investigated by Moraes et al (2017). However, the six loci presented lower numbers of alleles than those found by Santos et al (2009) in a wild population collected on the São Miguel Island, Pará, who obtained number of alleles between 7 (Cm1A8) and 21 alleles (Cm1H8) for the same loci implemented in this study.…”

“…In a study with C. macropomum broodstocks in Brazil, Santos et al (2016) found He ranging from 0.48 to 0.63 and Ho from 0.26 to 0.52, which demonstrated a heterozygote deficit shown by the F IS . Moraes et al (2017) also found values of this coefficient from 0.229 to 0.348 in two broodstocks in the Northern region. It is expected that in stocks kept in captivity, there will be a decrease in genetic diversity as a consequence of intentional selection and of the mating among parental (Jacometo et al, 2010;Lopera-Barrero et al, 2015;Santos et al, 2016).…”

“…Its production is currently widespread, spanning several fish farms in the Southeast, Central West and Northeast regions of Brazil. Despite its commercial and cultural importance, its populations have been reported to be declining in the basins where it naturally occurs, with extractives being one of the main causes (Moraes et al, 2017).…”

“…Tambaqui is the most produced native species in Brazil with a highest production rate at the northern region, so its genetic evaluation is extremely important to increase productivity in fish farming. Priorly, the literature does not take into consideration ancestral studies for the subsequent reproduction and maintenance of genetic diversity in fish populations (Brabo et al, 2016;Moraes et al, 2017;Peixe BR, 2020). The objective of this paper is to evaluate the genetic diversity of three broodstocks of C. macropomum from the State of Rondônia.…”

Genetic characterization of tambaqui stocks from two pisciculture stations in the lower São Francisco River

“…Tambaqui production has been increasing in Brazil over the last years and, according to Instituto Brasileiro de Geografia e Estatística [IBGE] (2018) the cultivation of this species was responsible for 19.7% of continental aquaculture production in 2018. Nevertheless, there is still a lack of information on genetic evaluation in breeding programs for tambaqui (Moraes et al, 2017). The management of genetic diversity in cultivated fish stocks of economic importance such as tambaqui is critical and can have direct implications on the quality of the products available to consumers.…”