Dataset Information

A combination mode of climate variability responsible for extremely poor recruitment of the Japanese eel (Anguilla japonica).

ABSTRACT: Satellite data and assimilation products are used to investigate fluctuations in the catch of Japanese eel (Anguilla japonica) in eastern Asian countries. It has been reported that the salinity front has extended farther south, which has shifted the eel's spawning grounds to a lower latitude, resulting in smaller eel catches in 1983, 1992, and 1998. This study demonstrates that interannual variability in the eel catch is strongly correlated with the combination mode (C-mode), but not with the El Niño-Southern Oscillation. These eels continue to spawn within the North Equatorial Current (NEC), but the salinity front shifts south during a canonical El Niño. On the other hand, the spawning grounds accompanied by the salinity front extend farther south during the C-mode of climate variability, and eel larvae fail to join the nursery in the NEC, resulting in extremely poor recruitment in East Asia. We propose an appropriate sea surface temperature index to project Japanese eel larval catch.

SUBMITTER: Lin YF

PROVIDER: S-EPMC5353692 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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A combination mode of climate variability responsible for extremely poor recruitment of the Japanese eel (Anguilla japonica).

Lin Yong-Fu YF Wu Chau-Ron CR Han Yu-San YS

Scientific reports 20170316

Satellite data and assimilation products are used to investigate fluctuations in the catch of Japanese eel (Anguilla japonica) in eastern Asian countries. It has been reported that the salinity front has extended farther south, which has shifted the eel's spawning grounds to a lower latitude, resulting in smaller eel catches in 1983, 1992, and 1998. This study demonstrates that interannual variability in the eel catch is strongly correlated with the combination mode (C-mode), but not with the El ...[more]

PMID: 28300135

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Project description:Long-term (1967-2008) glass eel catches were used to investigate climatic effects on the annual recruitment of Japanese eel to Taiwan. Specifically, three prevailing hypotheses that potentially explain the annual recruitment were evaluated. Hypothesis 1: high precipitation shifts the salinity front northward, resulting in favorable spawning locations. Hypothesis 2: a southward shift of the position of the North Equatorial Current (NEC) bifurcation provides a favorable larval transport route. Hypothesis 3: ocean conditions (eddy activities and productivity) along the larval migration route influence larval survival. Results of time series regression and wavelet analyses suggest that Hypothesis 1 is not supported, as the glass eel catches exhibited a negative relationship with precipitation. Hypothesis 2 is plausible. However, the catches are correlated with the NEC bifurcation with a one-year lag. Considering the time needed for larval transport (only four to six months), the one-year lag correlation does not support the direct transport hypothesis. Hypothesis 3 is supported indirectly by the results. Significant correlations were found between catches and climate indices that affect ocean productivity and eddy activities, such as the Quasi Biennial Oscillation (QBO), North Pacific Gyre Oscillation (NPGO), Pacific Decadal Oscillation (PDO), and Western Pacific Oscillation (WPO). Wavelet analysis reveals three periodicities of eel catches: 2.7, 5.4, and 10.3 years. The interannual coherence with QBO and the Niño 3.4 region suggests that the shorter-term climate variability is modulated zonally by equatorial dynamics. The low-frequency coherence with WPO, PDO, and NPGO demonstrates the decadal modulation of meridional teleconnection via ocean-atmosphere interactions. Furthermore, WPO and QBO are linked to solar activities. These results imply that the Japanese eel recruitment may be influenced by multi-timescale climate variability. Our findings call for investigation of extra-tropical ocean dynamics that affect survival of eels during transport, in addition to the existing efforts to study the equatorial system.

Project description:Japanese eel (Anguilla japonica) constitutes one of the most important food fish in Japan; accordingly, genome sequencing and linkage mapping have been conducted for the purpose of artificial cultivation. In the next stage, integration of genomic sequences within linkage groups (LG) is required to construct higher-resolution genetic markers for quantitative trait loci mapping and selective breeding of beneficial traits in farming. In order to identify LG1-linked scaffolds from the draft genome assembly (323,776 scaffolds) reported previously, we attempted to isolate chromosomes corresponding to LG1 by flow sorting and subsequent analyses. Initially, single chromosomes were randomly collected by chromosome sorting and subjected to whole-genome amplification (WGA). A total of 60 WGA samples were screened by PCR with primers for a known LG1-linked scaffold, and five positive WGA samples were sequenced by next-generation sequencing (NGS). Following reference mapping analysis of the NGS reads, four of the five WGA samples were found to be enriched by LG1-linked sequences. These samples were cytogenetically assigned to chromosome 5 by fluorescence in situ hybridization. Using blastn searches with 82,081 contigs constructed from the NGS reads of the four WGA samples as queries, 2323 scaffolds were identified as putative LG1-linked scaffolds from the draft genome assembly. The total length of the putative LG1-linked scaffolds was 99.0 Mb, comparable to the estimated DNA amounts of chromosome 5 (91.1 Mb). These results suggest that the methodology developed herein is applicable to isolate specific chromosome DNAs and integrate unanchored scaffold sequences onto a particular LG and chromosome even in teleost fishes, in which isolation of specific chromosomes by flow sorting is generally difficult owing to similar morphologies, sizes, and GC-contents among chromosomes in the genome. The putative LG1-linked scaffolds of Japanese eel contain a total of 6833 short tandem repeats which will be available for higher-resolution linkage mapping.

Dataset Information

A combination mode of climate variability responsible for extremely poor recruitment of the Japanese eel (Anguilla japonica).

Publications

A combination mode of climate variability responsible for extremely poor recruitment of the Japanese eel (Anguilla japonica).

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