Assessing sexual maturity of feminized Japanese eel Anguilla japonica by measuring eye size

Okamura, Atsushi; Oka, Hideo; Horie, Noriyuki; Utoh, Tomoko; Yamada, Yoshiaki; Mikawa, Naomi; Tanaka, Satoru; Tsukamoto, Katsumi

doi:10.1007/s10499-008-9172-z

Cited by 2 publications

(3 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In feminised eels, the number of weekly SPE injections administrated before ovulation was significantly less as relative eye size (eye index by Pankhurst ) increased (Okamura et al. ). The gonad somatic index (GSI) values of these eels were positively correlated with relative eye size, suggesting that sexually advanced individuals responded well to SPE (Okamura et al.…”

Section: Female Broodstockmentioning

confidence: 99%

See 1 more Smart Citation

Recent advances in artificial production of glass eels for conservation of anguillid eel populations

Okamura¹,

Horie²,

Mikawa³

et al. 2013

Ecology of Freshwater Fish

Self Cite

105

View full text Add to dashboard Cite

-Remarkable progress in techniques for maturation of adults and rearing of larvae has been achieved for the Japanese eel Anguilla japonica over the past 50 years, but recent efforts have not yet succeeded in the mass production of glass eels. This article reviews recent advances in techniques for artificial production of A. japonica glass eels. Successful new protocols for obtaining viable eggs and larvae of A. japonica are largely resulting from using artificially feminised eels instead of wild silver eels. The feminisation technique by administration of 17b-estradiol to glass eels not only provides an opportunity for using females as experimental broodstock throughout the year, but also accelerates their oocyte development or even increases the competence of females to respond to salmon pituitary extract. Induced spontaneous spawning with paired eels can improve the success rate for obtaining good-quality eggs compared with the traditional stripping-insemination method. As a result of the accumulation of field data on natural environmental conditions, such as an optimum temperature, where eel eggs and larvae were collected, the survival and growth rate of captive eel leptocephali have been much improved under these conditions. However, 50% diluted sea water (17.5 psu) that is far from the natural condition can result in better growth and survival performance in A. japonica leptocephali, possibly because it reduces the energy necessary for osmoregulation. Starvation can be a cue for triggering the onset of metamorphosis in A. japonica leptocephali, reducing the prolonged duration of the larval stage in captivity. To reach the mass production of glass eels at a commercial level, further improvement in quality of an artificial larval diet not containing eggs of the endangered shark Squalus acanthias is needed. The control of deformities in captive leptocephali and glass eels is also an important task. New techniques reducing the excessive use of exogenous hormones with parent eels should also be developed, to avoid public perception of an unhealthy product. If these techniques are completely established, we can exchange artificially produced glass eels with some part of the wild glass eels that are heavily exploited and provided to the eel aquaculture industry, and this can help to reduce the impact of eel consumption, which will contribute to the conservation of eel species worldwide.

show abstract

Section: Female Broodstockmentioning

confidence: 99%

“…The gonad somatic index (GSI) values of these eels were positively correlated with relative eye size, suggesting that sexually advanced individuals responded well to SPE (Okamura et al. ). Chai et al.…”

Section: Female Broodstockmentioning

confidence: 99%

Recent advances in artificial production of glass eels for conservation of anguillid eel populations

Okamura¹,

Horie²,

Mikawa³

et al. 2013

Ecology of Freshwater Fish

Self Cite

105

View full text Add to dashboard Cite

show abstract

“…As such, the lack of inclusion as interactions with extrinsic variables in our reviewed articles may be driving the nonsignificance found between maturity and movement. Maturity can be difficult to measure in anguillid eels; several difference indices exist (Cottrill et al 2002;Acou et al 2006;Okamura et al 2007Okamura et al , 2009 and the reviewed studies may not have been able to sample a range of sizes. It is also notable, that sample size was low with less than one third of the articles including maturity as an explanatory variable, hence the influence of maturity of eel movement in lentic systems warrants further investigation.…”

Section: Maturitymentioning

confidence: 99%

The drivers of anguillid eel movement in lentic water bodies: a systematic map

Williamson

Jacoby

Piper

2023

Rev Fish Biol Fisheries

View full text Add to dashboard Cite

Anguillid eels are near globally distributed catadromous fishes with marine spawning areas and inshore and inland growth areas in both lotic (rivers, estuaries) and lentic (lakes, ponds, lagoons) water bodies. As predators, anguillid eels play an important ecological role in both marine and freshwater systems, and several species are harvested commercially for food. However, some of the more widely distributed species have undergone severe declines in recruitment and their population status is now of significant concern. Given the multiple and lengthy migrations undertaken by anguillid eels, understanding of the drivers of movement is fundamental for species conservation and management. Yet, despite the importance of lentic systems to their ecology, most studies on anguillid eel movement have been conducted in lotic systems. Given that key influences on eel migration in lotic water bodies, such as fluctuations in flow and water temperature, may be minimised in lentic environments, the transferability of findings between lotic and lentic systems cannot be assumed. A systematic map was constructed to synthesise current knowledge on the extrinsic and intrinsic drivers of anguillid eel movement in lentic systems. The current state of knowledge of the drivers of eel movement in lentic systems is presented and compared to the relatively well-understood drivers of movement in lotic systems. We also discuss current knowledge gaps and limitations, and identify key future research requirements to inform the management and conservation of anguillid eels in understudied lentic systems. Graphical abstract

show abstract

Assessing sexual maturity of feminized Japanese eel Anguilla japonica by measuring eye size

Cited by 2 publications

References 16 publications

Recent advances in artificial production of glass eels for conservation of anguillid eel populations

Recent advances in artificial production of glass eels for conservation of anguillid eel populations

The drivers of anguillid eel movement in lentic water bodies: a systematic map

Contact Info

Product

Resources

About