Size-related variation in fecundity of European eel (Anguilla anguilla)

MacNamara, Ruairí; McCarthy, T. K.

doi:10.1093/icesjms/fss123

Cited by 29 publications

(41 citation statements)

References 21 publications

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“…Some A. anguilla fecundity estimates have been obtained from hormone treated eels (e.g. Amin, 1998, see also Table 2 in MacNamara & McCarthy, 2012), but estimates from wild silver eels are limited to north-west Europe (from Ireland, Northern Ireland and England) and this study from the eastern Mediterranean (Greece). Fecundity estimates of 400 g silver eels from north-west Europe ranged between ca.…”

Section: Discussionmentioning

confidence: 99%

“…MacNamara & McCarthy, 2012), only eels with an eye index >6.5 (Pankhurst, 1982) and GSI >1.2% (Durif et al, 2005) were considered for fecundity analysis.…”

Section: [ { ( Right Horizontal Eye Diameter + Right Vertical Eye Diamentioning

confidence: 99%

“…Gonads were treated according to the protocols described by Barbin & McCleave (1997) and MacNamara & McCarthy (2012). Each pair of gonads were thawed and placed in a container of 250 mL 2% acetic acid.…”

Section: [ { ( Right Horizontal Eye Diameter + Right Vertical Eye Diamentioning

confidence: 99%

“…However, studies are primarily focused on eel subpopulations migrating from western and northern Europe, the Baltic region and the western Mediterranean (e.g. MacNamara & McCarthy, 2012;Marohn et al, 2013;Quadroni et al, 2013;Amilhat et al, 2014). The eastern Mediterranean (defined here as east of 20° E) is distinctly under-represented, even in 'pan-European' type studies (Jakob et al, 2009;Belpaire et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Reproductive potential of silver European eels (Anguilla anguilla) migrating from Vistonis Lake (Northern Aegean Sea, Greece)

et al. 2014

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The European eel (Anguilla anguilla), once abundant throughout much of Europe and North Africa, has recently been classified as critically endangered. Information on its biology from the eastern Mediterranean is lacking, especially in relation to spawner quality. Therefore, silver eels were sampled during their seaward spawning migration from Vistonis Lake in Greece. Characteristics linked to reproductive output and success (i.e. body size and condition, sex ratio, silvering, Anguillicola crassus infection, fecundity and oocyte diameter) were examined. The lake produced large (687-1138 mm), exclusively female silver eels, 61.7% of which were infected by A. crassus. Silver eel fecundity, the first estimates from the southern part of the species range, was positively related to body length (R 2 = 0.693; P < 0.001) and body weight (R 2 = 0.731; P < 0.001). Fecundity did not differ between A. crassus infected and uninfected silver eels, but Greek silver eels were significantly more fecund than those in northwest Europe. The reproductive potential of Vistonis Lake silver eels and their contribution to the A. anguilla spawning stock is discussed.

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Section: Discussionmentioning

confidence: 99%

“…MacNamara & McCarthy, 2012), only eels with an eye index >6.5 (Pankhurst, 1982) and GSI >1.2% (Durif et al, 2005) were considered for fecundity analysis.…”

Section: [ { ( Right Horizontal Eye Diameter + Right Vertical Eye Diamentioning

confidence: 99%

Section: [ { ( Right Horizontal Eye Diameter + Right Vertical Eye Diamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reproductive potential of silver European eels (Anguilla anguilla) migrating from Vistonis Lake (Northern Aegean Sea, Greece)

et al. 2014

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“…It is often found that F2 hybrids show reduced fitness because of disruption of sets of co-adapted genes by recombination that occurs in the second or later generations when assortment of alleles at different loci takes place (Gharrett and Smoker, 1991;Johnson et al, 2010). Eels are highly fecund, with an estimated mean fecundity of 3.6 million of eggs per female (MacNamara and McCarthy, 2012); therefore, even though the expected proportion of heterozygous loci in first-generation backcrosses is 50%, there will be variance around this number. In a large number of offspring from a single cross, there would consequently be some individuals that show high heterozygosity for diagnostic alleles at loci that presumably are under selection.…”

Section: Patterns Of Hybridizationmentioning

confidence: 99%

Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms

et al. 2014

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The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N ¼ 159) and from the neighboring Faroe Islands (N ¼ 29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel female Â American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid Â pure European eel) and three individuals identified as second-generation backcrosses originating from American eel Â F1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization.

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Ontogenetic habitat shift of Anguilla marmorata and A. japonica in the rivers of southern Japan: Implications for habitat use evaluation and conservation

Kumai,

Kuroki,

Goto

et al. 2023

Aquatic Conservation

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Understanding the habitat requirements of fishes throughout their life cycle is essential for effective conservation. Despite the growing need to conserve anguillid eels, the current understanding of the ontogenetic habitat shifts during their riverine stages remains limited, particularly for the Japanese eel Anguilla japonica and the Indo‐Pacific eel Anguilla marmorata. Here, changes in habitat use during the riverine stages of these two eel species were investigated in the southern Japan rivers, where they coexist. Eels were classified into total length (TL) classes at 10 cm intervals, and generalized additive models were constructed using these classes as an ordinal, quasi‐continuous explanatory variable. The models showed that the habitat use of the two species changed with growth; both species shifted to deeper and more lentic habitats as they grew larger. Small‐ and mid‐sized (<25 and 25–55 cm in TL, respectively) A. japonica used more lentic habitats with smaller substrates, ranging from sand/silt to cobbles, than small‐ and mid‐sized A. marmorata, which mainly used lotic habitats with cobble and boulder substrates. However, compared with small‐sized conspecifics, mid‐sized A. japonica mainly used habitats with larger substrates, such as pebbles and cobbles, suggesting that the interspecific overlap in habitat use is relatively high for mid‐sized individuals of both species. Large A. marmorata (85 cm) mainly used habitats with smaller substrates as they grew larger. The results suggest that using a fine body size classification and including these classes as a quasi‐continuous explanatory variable in habitat models capture gradual changes in habitat use, improving habitat use evaluation of anguillid eels. Preserving the environmental heterogeneity of river habitats in terms of water depth, current velocity and substrate size would facilitate habitat segregation of both conspecifics and allospecifics in the same rivers, thereby promoting the conservation of anguillid eels.

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Size-related variation in fecundity of European eel (Anguilla anguilla)

Cited by 29 publications

References 21 publications

Reproductive potential of silver European eels (Anguilla anguilla) migrating from Vistonis Lake (Northern Aegean Sea, Greece)

Reproductive potential of silver European eels (Anguilla anguilla) migrating from Vistonis Lake (Northern Aegean Sea, Greece)

Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms

Ontogenetic habitat shift of Anguilla marmorata and A. japonica in the rivers of southern Japan: Implications for habitat use evaluation and conservation

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