Stable isotope analyses of muscle tissue (δ13Cmuscle and δ15Nmuscle) and otoliths (δ13Cotolith and δ18Ootolith) were used to retrospectively track habitat uses of Lethrinus lentjan, and to determine any association between Setiu Lagoon (nursery habitat) and coastal artificial reefs (CARs; adult habitats) on the Terengganu coast, Malaysia. Muscle stable isotopes exhibited a spatial change from inshore to offshore habitats associated with growth, possibly related to the reef-ward movement of the fish. Otolith stable isotopes of adult fish from CARs were measured in juvenile (from outside the core to the first opaque zone of otolith) and adult (the edge of otolith) portions and were compared with those of juveniles from Setiu Lagoon, suggesting that the adult fish may not primarily use the lagoon as a nursery before ontogenetically migrating to CARs. The effects of coastal currents between monsoonal seasons could reorientate offshore juvenile migration; hence, adult cohorts in CARs may be replenished from various nursery habitats along the coast. Additionally, similarities in the δ18Ootolith values of juvenile and adult sections suggested that some individuals may not spend their juvenile phases in shallow estuarine habitats. Based on the findings of this study, we recommend that coastal conservation strategies take into account multiple nursery habitats rather than a single one.
Benthic species, though ecologically important, are vulnerable to genetic loss and population size reduction due to impacts from fishing trawls. An assessment of genetic diversity and population structure is therefore needed to assist in a resource management program. To address this issue, the two-spined yellowtail stargazer (Uranoscopus cognatus) was collected within selected locations in the Indo-West Pacific (IWP). The partial mitochondrial DNA cytochrome c oxidase subunit 1 and the nuclear DNA recombination activating gene 1 were sequenced. Genetic diversity analyses revealed that the populations were moderately to highly diversified (haplotype diversity, H = 0.490–0.900, nucleotide diversity, π = 0.0010–0.0034) except sampling station (ST) 1 and 14. The low diversity level, however was apparent only in the matrilineal marker (H = 0.118–0.216; π = 0.0004–0.0008), possibly due to stochastic factors or anthropogenic stressors. Population structure analyses revealed a retention of ancestral polymorphism that was likely due to incomplete lineage sorting in U. cognatus, and prolonged vicariance by the Indo-Pacific Barrier has partitioned them into separate stock units. Population segregation was also shown by the phenotypic divergence in allopatric populations, regarding the premaxillary protrusion, which is possibly associated with the mechanism for upper jaw movement in biomechanical feeding approaches. The moderate genetic diversity estimated for each region, in addition to past population expansion events, indicated that U. cognatus within the IWP was still healthy and abundant (except in ST1 and 14), and two stock units were identified to be subjected to a specific resource management program.
The population genetic diversity and demographic history of the longtail tuna Thunnus tonggol in Malaysian waters was investigated using mitochondrial DNA D-loop and NADH dehydrogenase subunit 5 (ND5). A total of 203 (D-loop) and 208 (ND5) individuals of T. tonggol were sampled from 11 localities around the Malaysian coastal waters. Low genetic differentiation between populations was found, possibly due to the past demographic history, dispersal potential during egg and larval stages, seasonal migration in adults, and lack of geographical barriers. The gene trees, constructed based on the maximum likelihood method, revealed a single panmictic population with unsupported internal clades, indicating an absence of structure among the populations studied. Analysis on population pairwise comparison ФST suggested the absence of limited gene flow among study sites. Taken all together, high haplotype diversity (D-loop = 0.989–1.000; ND5 = 0.848–0.965), coupled with a low level of nucleotide diversity (D-loop = 0.019–0.025; ND5 = 0.0017–0.003), “star-like” haplotype network, and unimodal mismatch distribution, suggests a recent population expansion for populations of T. tonggol in Malaysia. Furthermore, neutrality and goodness of fit tests supported the signature of a relatively recent population expansion during the Pleistocene epoch. To provide additional insight into the phylogeographic pattern of the species within the Indo-Pacific Ocean, we included haplotypes from GenBank and a few samples from Taiwan. Preliminary analyses suggest a more complex genetic demarcation of the species than an explicit Indian Ocean versus Pacific Ocean delineation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.