Species identification and morphological differences of anguillid glass eels recruiting to Viti Levu Island of Fiji in the western South Pacific

There are six species of anguillid eels that live in various regions of the western South Pacific but the species compositions of glass eels recruiting to many of the islands of the region are not well known. A total of 1368 anguillid glass eels were collected fortnightly at the mouth of a small river at Namelimeli near Navua in Fiji Islands between April 2015 and June 2016. These were found through DNA barcoding to have a species composition comprising of two longfin eels Anguilla marmorata and A. megastoma, and one shortfin eel A. obscura. 35 glass eels from each species were then selected for morphological studies, it was found that the external morphological characters of anodorsal length ratios, caudal pigmentation patterns, and the internal characters of total, predorsal, and anodorsal vertebral counts were sufficient to classify these three species using morphological characters alone. These findings will simplify research and monitoring techniques of anguillid glass eel recruitment for conservation, fisheries management or aquaculture purposes in the South Pacific

Efficiency of Peptide Nucleic Acid-Directed PCR Clamping and Its Application in the Investigation of Natural Diets of the Japanese Eel Leptocephali

Polymerase chain reaction (PCR)-clamping using blocking primer and DNA-analogs, such as peptide nucleotide acid (PNA), may be used to selectively amplify target DNA for molecular diet analysis. We investigated PCR-clamping efficiency by studying PNA position and mismatch with complementary DNA by designing PNAs at five different positions on the nuclear rDNA internal transcribed spacer 1 of the Japanese eel Anguilla japonica in association with intra-specific nucleotide substitutions. All five PNAs were observed to efficiently inhibit amplification of a fully complementary DNA template. One mismatch between PNA and template DNA inhibited amplification of the template DNA, while two or more mismatches did not. DNA samples extracted from dorsal muscle and intestine of eight wild-caught leptochephalus larvae were subjected to this analysis, followed by cloning, nucleotide sequence analysis, and database homology search. Among 12 sequence types obtained from the intestine sample, six were identified as fungi. No sequence similarities were found in the database for the remaining six types, which were not related to one another. These results, in conjunction with our laboratory observations on larval feeding, suggest that eel leptocephali may not be dependent upon living plankton for their food source

Strontium/Calcium ratios in statoliths of the neon flying squid, Ommastrephes bartrami (Cephalopoda), in the North Pacific Ocean

Strontium to calcium ratios were observed along longitudinal sections of statoliths of nine neon flying squid, Ommastrephes bartrami (LeSueur, 1821), including three mature females (422 to 454 mm mantle length, ML; 207 to 306 d old) obtained from the North Pacific (27–35°N; 144–150°E) during winter and six immature males and females (187 to 226 mm ML; 126 to 164 d old) collected from 39°N; 145°E and 39°N; 169°W during summer. The distances between the nucleus (core) and the edge of the dorsal dome were approximately 660 to 690 μm in mature females and 450 to 510 μm in the immature squid. Sr/Ca ratios were determined at intervals of 30 μm between the nucleus and edge of the dorsal dome. Sr/Ca ratios were higher in areas near the nuclei and peripheral portions of the dorsal dome than in the middle portions of the statoliths (270 to 420 μm from the nuclei, corresponding to ages of 60 to 90 d) in mature females; thus a U-shaped pattern was evident. Sr/Ca ratios in the six immature squid decreased from nucleus to the dorsal dome; in three squid the ratios slightly increased toward the dorsal dome edge. The observed Sr/Ca ratios in immature squid were considered to represent younger portions of the U-shaped pattern. In the present study we discuss this pattern in relation to environmental and biological conditions of O. bartrami, which undertakes seasonal migrations between spawning grounds in the Subtropical Domain and feeding grounds in the Subarctic Domain and Transitional Zone in the North Pacific Ocean. Although Sr/Ca ratios are potentially affected by ambient water temperature and ontogenetic conditions, including somatic growth and statolith growth, it was impossible to evaluate each environmental and biological effect separately, as variations in these factors are complicated and effects could be interdependent

Early life history of tropical freshwater eels (Anguilla spp.)recruiting to Viti Levu, Fiji Islands, in the western South Pacific

The oceanic early life histories of three species of tropical anguillid glass eels, namely Anguilla marmorata, Anguilla megastoma and Anguilla obscura, recruiting to Viti Levu, Fiji Islands, in the western South Pacific, were studied using otolith microstructures of 94 individuals. A. megastoma had the shortest leptocephalus duration, age at recruitment and metamorphosis stage (mean ± s.d. 104.7 ± 7.2, 141.3 ± 8.7 and 36.6 ± 8.5 days respectively), followed by A. marmorata (September–October recruitment peak: 113.0 ± 11.9, 115.1 ± 8.3 and 39.2 ± 11.1 days respectively; April recruitment peak: 152.2 ± 13.5, 154.0 ± 12.5 and 38.9 ± 10.1 days respectively) and A. obscura (118.0 ± 10.2, 168.4 ± 16.5 and 49.6 ± 12.5 days respectively). A. obscura also had the shortest oceanic glass eel duration of (12.2 ± 3.4 days), followed by both peaks of A. marmorata (23.3 ± 3.2 and 20.2 ± 3.3 days) and A. megastoma (20.7 ± 6.7 days). Otolith increment rates during the leptocephalus stage did not differ significantly among the three species, but there were significant differences between the leptocephalus duration and metamorphosis stage of A. megastoma compared with A. marmorata and A. obscura, as well as in the oceanic glass eel duration of A. obscura compared with A. marmorata and A. megastoma. There were also significant differences in the age at recruitment among all three species. Back-calculated hatch dates suggest separate peak seasonal spawning periods for each of the three species

Early life history of tropical freshwater eels (Anguilla spp.) recruiting to Viti Levu, Fiji Islands, in the western South Pacific

The oceanic early life histories of three species of tropical anguillid glass eels, namely Anguilla marmorata, Anguilla megastoma and Anguilla obscura, recruiting to Viti Levu, Fiji Islands, in the western South Pacific, were studied using otolith microstructures of 94 individuals. A. megastoma had the shortest leptocephalus duration, age at recruitment and metamorphosis stage (mean ± s.d. 104.7 ± 7.2, 141.3 ± 8.7 and 36.6 ± 8.5 days respectively), followed by A. marmorata (September-October recruitment peak: 113.0 ± 11.9, 115.1 ± 8.3 and 39.2 ± 11.1 days respectively; April recruitment peak: 152.2 ± 13.5, 154.0 ± 12.5 and 38.9 ± 10.1 days respectively) and A. obscura (118.0 ± 10.2, 168.4 ± 16.5 and 49.6 ± 12.5 days respectively). A. obscura also had the shortest oceanic glass eel duration of (12.2 ± 3.4 days), followed by both peaks of A. marmorata (23.3 ± 3.2 and 20.2 ± 3.3 days) and A. megastoma (20.7 ± 6.7 days). Otolith increment rates during the leptocephalus stage did not differ significantly among the three species, but there were significant differences between the leptocephalus duration and metamorphosis stage of A. megastoma compared with A. marmorata and A. obscura, as well as in the oceanic glass eel duration of A. obscura compared with A. marmorata and A. megastoma. There were also significant differences in the age at recruitment among all three species. Back-calculated hatch dates suggest separate peak seasonal spawning periods for each of the three species