4.1 Genetic diversity
Haplotype diversity
(H d) and nucleotide diversity (π ) are two
important indicators to measure genetic diversity, and πrepresents the proportion of each haplotype in the populations, which
can reveal the polymorphism of mtDNA in the populations more accurately
(Chen et al., 2022). Grant & Bowen (1998) concluded thatH d was higher than 0.5 and π was greater
than 0.005, which indicated higher species diversity. This study
revealed high levels of haplotype and low levels of nucleotide
diversity, which is common among some marine fish species (Avise et al.,
1987; Zhang et al., 2006).
High genetic diversity plays a crucial role in the exploitation and
restoration of fishery resources (DeWoody et al., 2021). Assessing
genetic diversity is an effective approach the adaptability and survival
ability of species in response to environmental changes (Schmitt and
Hewitt, 2004), which is essential for species management and
conservation. The fish of L. spadiceus is an economic species and
has been caught for a long time. Compared with other marine fishes in
the same sea area, L. spadiceus had a lower nucleotide diversity
(Yi et al., 2021; Niu et al., 2019; Xu et al., 2021), reflecting that
the L. spadiceus population in the South China Sea has a fragile
genetic diversity and requires conservation as well as a sustainable
development planning from fishery management.