No abstract

The oriental river prawn (Macrobrachium nipponense) is a non-obligatory amphidromous prawn, and it has a wide distribution covering almost the entire Taiwan. Mitochondrial DNA fragment sequences of the cytochrome oxidase subunit I (COI) and 16S rRNA were combined and used to elucidate the population structure and historical demography of oriental river prawn in Taiwan. A total of 202 individuals from six reservoirs and three estuaries were separately collected. Nucleotide diversity (π) of all populations was 0.01217, with values ranging from 0.00188 (Shihmen Reservoir, SMR, northern Taiwan) to 0.01425 (Mingte Reservoir, MTR, west-central Taiwan). All 76 haplotypes were divided into 2 lineages: lineage A included individuals from all sampling areas except SMR, and lineage B included specimens from all sampling locations except Chengching Lake Reservoir (CLR) and Liyu Lake Reservoir (LLR). All F ST values among nine populations were significantly different except the one between Jhonggang River Estuary (JGE, west-central Taiwan) and Kaoping River Estuary (KPE, southern Taiwan). UPGMA tree of nine populations showed two main groups: the first group included the SMR and Tamsui River Estuary (TSE) (both located northern Taiwan), and the second one included the other seven populations (west-central, southern and eastern Taiwan). Demographic analyses implied a population expansion occurred during the recent history of the species. The dispersal route of this species might be from China to west-central and west-southern Taiwan, and then the part individuals belonging to lineage A and B dispersed southerly and northerly, respectively. And then part individuals in west-central Taiwan fell back to and stay at estuaries as the sea level rose about 18,000 years ago.

Sequence analyses on the intron from the elongation factor-1a gene were conducted to examine the population structure of sword prawn (Parapenaeopsis hardwickii) in the East China Sea and Taiwan Strait. Five samples including 207 individuals were separately collected from the north of East China Sea (NECS) and waters off Tamsui, Taichung, Putai, and Cheding, and 102 alleles were identified. Despite no phylogeographic structure in alleles, pairwise F ST values and analysis of molecular variance (AMOVA) showed significant genetic difference between the NECS and the other four samples. The UPGMA tree of five samples showed two distinct clusters; one included the NECS sample; the other included the rest of samples. The results suggest that two populations exist in the East China Sea and Taiwan Strait. To ensure resource sustainability and maintenance, the sword prawn in the Taiwan Strait and the north of the East China Sea should be treated as two separate populations and then be separately managed in future. Both Tajima's D and Fu and Li's D statistics and analysis of mismatch distribution for overall alleles suggested that sword prawn in studied area had experienced population expansion.

Mangrove degradation is a well-documented trend, but the spread of mangroves within the Siangshan Wetland in Hsinchu, Taiwan, runs contrary to that trend. The spread of mangroves changes the structure and functions of habitats for benthic organisms, causes infilling of estuaries and flooding and creates breeding grounds for small black mosquitoes. A large-scale mangrove-removal project was undertaken by the Hsinchu City Government from October 2015 to March 2016. They also investigated the consequences of mangrove removal on benthic organisms and adjacent habitats from October 2015 to September 2016, and the density, species count, Shannon–Wiener index (H′), and Pielou’s evenness index (J′) of the mangrove and non-mangrove regions were compared. In this study, we used satellite telemetry images to monitor fluctuations in mangrove density from 2006 to 2016. The non-mangrove region exhibited more variations than the mangrove region. After mangrove removal, species returned to their original habitats and noteworthy biological values significantly increased in the mangrove regions. This study presents evidence to argue that mangrove removal benefits benthic organisms. The results indicate that mangrove removal can be an appropriate habitat rehabilitation strategy for benthic organisms. The ecological findings of this study can inform coastal managers or other officials who seek to steward mangrove biomass.