Life history-related organotin body burden in the catadromous eels Anguilla marmorata and A. bicolor pacifica in Vietnam.

In order to understand the ecological risks caused by organotin compounds (OTs) in diadromous fish migrating between sea and freshwater, tributyltin (TBT) and triphenyltin (TPT) compounds, and their breakdown products, were determined in the catadromous eels Anguilla marmorata and A. bicolor pacifica, collected in Vietnam waters. Ontogenic changes in otolith strontium (Sr) and calcium (Ca) concentrations were examined along life history transects in order to determine habitat use in the eel. There were generally no significant correlations between TBT and TPT accumulation and various biological characteristics such as total length (TL) and body weight (BW). In A. bicolor pacifica, TBT and the total butyltin (BT) concentrations of yellow-stage eels (immature eels) were significantly higher than those in silver-stage eels (mature eels). This suggests that yellow-stage eels have a higher risk of contamination by TBT than silver-stage individuals. Positive linear relationships were found between Sr:Ca ratios, total BTs and total phenyltins. These results suggest that the ecological risk of OTs in these eels increases with increasing sea residence period. Thus, migratory history and maturation stage are the most important factor for OT accumulation in catadromous eels

Notes on the occurrence of the tropical eel Anguilla bicolor bicolor in Peninsular Malaysia, Malaysia

Previous studies indicated that a tropical freshwater eel Anguilla bicolor bicolor occurs in Africa, India, Sri Lanka, Bangladesh, Myanmar, Indonesia and Australia, but an intensive survey has indicated an extended distribution range for the species into Peninsular Malaysia. Thus, A. b. bicolor is a native subspecies of Malaysia

Age at maturation of a tropical eel Anguilla bicolor bicolor in Peninsular Malaysia, Malaysia.

Anguillid eel species are widely distributed throughout the world. The eels have catadromous life history, migrate between freshwater growth habitats and offshore spawning areas. Fifteen species of Anguilla have been reported worldwide, ten of which occur in tropical regions (Ege 1939). Of the latter, seven species/subspecies occur in the western Pacific around Indonesia and Malaysia, i.e. A. celebesensis, A. interioris, A. nebulosa nebulosa, A. marmorata, A. borneensis, A. bicolor bicolor and A. bicolor pacifica (Ege, 1939; Castle & Williamson, 1974; Arai et al., 1999). The tropical species is thought to be more closely related to the ancestral (primitive) form than their temperate counterparts. Studying the distribution and life history of tropical eels may provide some clues to understanding the nature of primitive forms in anguillid eels and how the distribution of the genus became established. The recent decline of glass eel (juvenile) catches in East Asia has caused serious problems in eel aquaculture in Japan and Taiwan. Eighteen percent of the eel consumed in Japan is produced in the country (23, 211 tons, aquaculture; and 817 tons, wild in 1999), and the remainder is imported from China, Taiwan, and Malaysia (Kato & Kobayashi, 2003). Therefore, the tropical eels are considered to be a major target species for the eel trading recently. However, little attention has been given to natural populations and the resource management of eel in Malaysia. Therefore, the objective of this study was to gain the biological information of a tropical eel Anguilla bicolor bicolor collected in the Peninsular Malaysia. In the present study, we found maturing stage of the eel in Malaysian waters. There is no information available regarding the maturation in the tropical eel species. We reported the first eel biology study in Malaysia. A total of 10 specimens were collected by local fishermen mainly in Kurau River in Bukit Merah and Penang River in Peneng Island of the northwestern peninsular (4°59'-5°23 N, 100°12-100°40'E) during November 2008 and August 2010. The eels were collected by angling and bamboo trap at night. The total length (TL), predorsal length (PDL), preanal length (PAL) (Fig. 1), body weight (BW) and gonad weight were measured. The gonad and body weights were measured to determine the gonado somatic index (GSI) of each eel

Cách sử dụng trợ từ Nhật ngữ

169 tr. ; 21 cm

Analysis of fluvial migration of the Irish pollan Coregonus autumnalis, using Sr:Ca ratios of otolith

The Irish pollan Coregonus autumnalis pollan (Pallas, 1776) is a unique and an endangered fish species endemic to the island of Ireland. However, there is little information available regarding the life history and migration of the species. The migratory history of the C. autumnalis pollan was examined for the first time in terms of strontium (Sr) and calcium (Ca) uptake in the otolith, by means of wavelength dispersive X-ray spectrometry on an electron microprobe. The Sr:Ca ratios measured along a transect from the core to the otolith edge showed consistently low Sr:Ca values, averaging from 1.0 × 10−3 to 1.4 × 10−3. The results suggested the non-anadromous (fluvial) life history styles of the Irish pollan C. autumnalis pollan, although the Arctic cisco C. autumnalis is typically an anadromous fish in low productivity river and coastal systems

Life history patterns of silver eels Anguilla japonica collected in the Sanriku Coast of Japan

The migratory history in the silver eel stage of the Japanese eel, Anguilla japonica, collected in the mouth of Kozuchi River along the Sanriku Coast of Japan, was examined using the otolith microstructure and analysis of strontium (Sr) and calcium (Ca) concentrations with wavelength dispersive X-ray spectrometry by an electron microprobe. The line analysis of Sr :Ca ratios along the life history transect of each otolith showed a peak (ca 12-15×10<-3>), which corresponded to the period of their leptocephalus and early glass eel stages in the ocean. The mean Sr : Ca ratios from the elver mark to the otolith edge indicated that there were eels with several general categories of migratory history, that included sea eels that never entered freshwater (average Sr : Ca ratios, >_6.0×10<-3>) and others that had entered freshwater for brief periods, but returned to the estuary or bay. This evidence of the occurrence of sea eels in this northern area indicates that Japanese eels of the Sanriku Coast do not necessarily migrate into freshwater rivers during recruitment as glass eels at the beginning of their growth phase, and even those that do enter freshwater may later return to the marine environment