Migration ecology in the freshwater eels of the genus Anguilla Schrank, 1798

1. Measurements of net flux of water have been made on isolated gills removed from freshwater-adapted and seawater-adapted eels and incubated in various media of differing osmotic pressure. 2. From these measurements it has been possible to determine the osmotic permeability coefficient of the gill directly from the net water flux. The values obtained (0.50±0.14x10-5 cm.sec-1 for freshwater eels and 0.43±0.07x10-5 cm.sec-1 for seawater-adapted eels) indicate that there was no significant change in this parameter on adaptation of the eels to sea water. 3. The direct measurements made of the net water flux across the isolated gills appear to be compatible with the osmoregulatory pattern of eels as deduced by other workers using different techniques. In particular they illustrate and further emphasize the significance of drinking in the freshwater fish. 4. Calculations indicate that, for a freshwater teleost, the osmotic and ionic problems caused by drinking in fresh water have an insignificant energetic effect and hence, energetically, it matters little to the fish whether it drinks or not.

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SPECIES COMPOSITION OF FRESHWATER EELS (Anguilla spp.) IN EIGHT RIVERS FLOWING TO PALABUHANRATU BAY, SUKABUMI, INDONESIA

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.29244/jitkt.v7i2.11027 ◽

2016 ◽

Vol 7 (2) ◽

Author(s):

Agus Alim Hakim ◽

M Mukhlis Kamal ◽

Nurlisa A Butet ◽

Ridwan Affandi

Keyword(s):

Cluster Analysis ◽

Discriminant Analysis ◽

Species Composition ◽

Dominant Species ◽

Morphological Identification ◽

Morphometric Data ◽

Freshwater Eel ◽

Glass Eels ◽

Freshwater Eels ◽

Tropical Freshwater

Freshwater eel (Anguilla spp.) is a catadromus fish that migrates from freshwater into seawater for spawning and return to freshwater during larvae stage to grow. The objective of this study was to determine species composition of tropical freshwater eels based on morphology collected from several rivers flowing in to the Palabuhan Ratu Bay. Young, adult, and glass eels were caught in August 2014 until Desember 2014. Glass eels were only caught in Cimandiri River. Freshwater eels were classified by ano-dorsal length (AD) divided by total length (TL), cluster analysis, and discriminant analysis based on morphometric data. The results showed different AD/TL of young and adult, i.e., 1.93±0.51 for A. bicolor bicolor, and 16.99±0.65 for A. marmorata, and three different AD/TL of glass eels i.e.,1.72±1.05 for A. bicolor bicolor6.60±1.79 for A. nebulosa nebulosa, and 15.07±1.04 for A. marmorata. Cluster analysis showed three groups of population characters of young and adult eels i.e. A. bicolor bicolor (2 groups) and A. marmorata (1 group). Discriminant analysis showed three groups of glass eels population i.e., A. bicolor bicolor, A. nebulosa nebulosa, and A. marmorata. Morphological identification showed that young and adult eels in Cibareno and Citepus rivers had two species i.e., A. bicolor bicolor and A. marmorata. Glass eels from Cimandiri river had three species i.e., A. bicolorbicolor, A. nebulosanebulosa, and A. marmorata. A. bicolor bicolor was found in each rivers and as a dominant species in Palabuhan Ratu Bay.Keywords: A. bicolor bicolor, A. marmorata, A. nebulosa nebulosa, species composition

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Variation in Population Structures of Tropical Freshwater Eels, Anguilla Marmorata, A. Bicolor Bicolor and A. Bengalensis Bengalensis, in the Indo-Pacific

10.21203/rs.3.rs-136957/v1 ◽

2021 ◽

Author(s):

Takaomi Arai ◽

Hussein Taha

Keyword(s):

Tropical Species ◽

Pacific Region ◽

Oceanic Current ◽

Dispersion Patterns ◽

Population Structures ◽

Different Populations ◽

And Migration ◽

Current Systems ◽

Freshwater Eels ◽

Spawning Sites

Abstract Freshwater eels, genus Anguilla, have a distinctive catadromous life history, which could be associated with certain oceanic current systems and offshore spawning sites. Thus, migration and dispersion patterns are believed to be important factors influencing the population structures of each species. Temperate eel species are well studied, while little research has been conducted on the tropical counterparts that comprise two-thirds of all eel species. The population structures of three tropical species, A. marmorata, A. bicolor bicolor and A. bengalensis bengalensis, which are distributed widely in the Indo-Pacific region, were explored by means of DNA sequence analysis of mitochondrial cytochrome c oxidase subunit I (COI). This study found that A. bicolor bicolor had two genetically distinct populations, and these different populations co-occur geographically in the Indo-Pacific region, while A. marmorata and A. bengalensis bengalensis showed a panmictic-population structure in this region. The populations of A. bicolor bicolor were also found to have lower genetic variability than the populations of A. marmorata and A. bengalensis bengalensis. This study is the first to explore the population genetic structure of A. bengalensis bengalensis. The present results also suggest plausible dispersion and migration of these tropical species into their continental habitats.

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