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Genetic variability of a small captive population of the Cobia (Rachycentron canadum) through pedigree analyses

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Relation http://eprints.cmfri.org.in/13004/
10.1016/j.aquaculture.2018.08.047
 
Title Genetic variability of a small captive population of the Cobia
(Rachycentron canadum) through pedigree analyses
 
Creator Sakthivel, M
Tamilmani, G
Nazar, A K A
Jayakumar, R
Sankar, M
Ramesh Kumar, P
Anikuttan, K K
Samal, Amir Kumar
Anbarasu, M
Gopakumar, G
 
Subject Fish Genetics
Cobia
 
Description The genealogical information of a small captive population of the Cobia fish was
evaluated to assess the genetic variability and the status of inbreeding through
pedigree analyses. Pedigree data (n=238) for 6 years (2010-2016) were analyzed and
offspring born from 2015 to 2016 were considered as reference population to
compute the population genetic parameters based on the gene origin probabilities
using the program ENDOG (version 4.8). Molecular marker based FAP (Family
Assignment Program, version 3.6) was used for parentage assignment. The pedigree
completeness was 68% for the parent, 29% for the grandparents and 7% for the greatgrandparents
generations with a mean equivalent to complete generations of 2.66.
Mean generation interval, computed from four pathways, was 2.38 years. Considering
the reference population into account the coefficients of average inbreeding and
average relatedness were computed as 9.6% and 9.9%, respectively. The mean values
of individual increase in inbreeding (rate of inbreeding) were 6.5% and 2.5% for the
reference population and for the whole pedigree, respectively. Realized effective
population size was computed from the individual increase in inbreeding and from the
individual increase in coancestry as 7.7 and 10.6, respectively. The effective numbers
of founders (fe), ancestors (fa), founder genomes (fg) and non-founder genomes (nfe)
for the reference population were computed as 6, 6, 3.8 and 11.1, respectively. About
85% of total genetic variation was explained by 7 most influential ancestors, with a
maximum individual contribution of 33.5%. Though the genetic bottleneck, as
expressed by the fe/fa ratio as 1.0, was not evident, the loss of genetic variability caused by genetic drift was evident by fg/fe ratio which was 0.64 for the reference
population. The analysis revealed the evidences on loss of genetic diversity with a
very critical effective population size. Recommendations were made to improve the
genetic variability in the herd. The present study signifies the importance of
maintaining the pedigree and can help in carrying out similar studies on captive-bred
fish species where small populations are inevitable.
 
Publisher Elsevier
 
Date 2019
 
Type Article
PeerReviewed
 
Format text
 
Language en
 
Identifier http://eprints.cmfri.org.in/13004/7/Sakthivel%20et%20al%202019_AQ_Pedigree%20Analysis%20in%20Cobia.pdf
Sakthivel, M and Tamilmani, G and Nazar, A K A and Jayakumar, R and Sankar, M and Ramesh Kumar, P and Anikuttan, K K and Samal, Amir Kumar and Anbarasu, M and Gopakumar, G (2019) Genetic variability of a small captive population of the Cobia (Rachycentron canadum) through pedigree analyses. Aquaculture, 498. pp. 435-443.