Gonad development and spawning behaviour of artificially-matured European eel (Anguilla anguilla L.)

Abstract

Gonadal development and spawning behaviour of artificially-matured European eel (Anguilla anguilla L.) was studied. Treatment of males with Human Chorionic Gonadotropin (HCG; 1 IU g/week) resulted in a Gonado-Somatic Index (GSI) of 10.88 ± 3.39 and spermiation. Treatment of females with carp Pituitary suspension (cPs) (20 mg cPs/kg body weight per week) resulted in oogenesis with a GSI of 20.0 ± 11.3 (n = 7), and the number of eggs per female was 1874 * 10 3 ± 1116 * 10 3 ; (n = 7). Ovulation of the females was induced with 17α, 20β dihydroxyprogesteron (DHP) at 2 µg/g bodyweight. Eggs of European eel were found to be non-sticky and typically pelagic. Maximum speed of eggs rising to the surface in a water column was 2.24 ± 0.33 metres (m) per hour (h). To study behaviour in a qualitative way, two females were used together with three groups of three males. During a 283 minute (min) observation of the two females, we observed female-female interaction: 'lethargic behaviour' (33.6%) vs. 'cruising together' (66.4%). In the period when males and females were together (188 min), we observed 'approaching the head region of the female' (57.7%), 'touching the operculum' (39.4%), or 'approaching the urogenital area' (2.9%) by the males (total 725 seconds (s)). Sperm release in the presence of a female took 115 s of the total approaching time of 725 s (15.9%), while in the case of male-male interaction this was only 15 s of the total period of 116 s (12.9%). Induced spawning behaviour of eels was collective and simultaneous, corresponding to spawning in a group. This is the first time group spawning behaviour has ever been observed and recorded in eels.

Changes in European eel ovary development and body and ovary chemistry during stimulated maturation under controlled conditions: preliminary data

“…The GSI in one of the females was about 32 %, the same as achieved by Pedersen (2003). The mean GSI (18.0 ± 10.6) achieved in this study in female eel after 13-16 weeks of hormonal stimulation is close to the value of GSI immediately before ovulation (20.0 ± 11.3 %) as found by other authors (e.g., van Ginneken et al 2005a). The fish in this study had a mean BWI of 115.4 ± 10.7 % (106.1-128.5 %), which is a satisfactory result compared to that found by Pedersen (2004): 110.7 ± 9.8 %.…”

“…Many intensive physiological and morphological changes take place in the eels during the maturation process (Müller et al 2004a;van Ginneken et al 2005a;Clevestam et al 2011;Nowosad et al 2014). Although the European eel is regarded as a trophic opportunist (Prigge et al 2012), it does not consume any food during its migration journey and it takes the energy it needs to travel the thousands of kilometers and undergo the maturation process from the fat accumulated in its body (Clevestam et al 2011).…”

Evaluacion de la primera madurez sexual del huachinango del Pacifico (Lutjanus peru) nacido en cautiverio

“…Sin embargo, en poblaciones silvestres sometidas a explotación, se ha observado una notable disminución tanto de edad como de la talla de la primera madurez, como es el caso del bacalao Gadus morhua (Chen & Mello, 1999), arenque Clupea harengus (Engelhard & Heino, 2004) y salmón Oncorhynchus keta (Morita et al, 2005;García de Leaniz et al, 2007), como una respuesta fenotípica de la primera madurez a las presiones del medio. Por otra parte, algunas especies como la anguila europea Anguilla anguilla L., no alcanzan la primera madurez sexual en cautiverio, probablemente debido a la falta de estímulos y de condiciones apropiadas para la natación a largo plazo (Dufour et al, 2005;Van Ginneken et al, 2005). Esto plantea un desafío para la acuicultura, debido a que tales respuestas fenotípicas pueden enmascarar la variabilidad en la edad y tamaño en la maduración, y hacer que sea más difícil seleccionar ejemplares para fines de madurez.…”

Preliminary insight into parental contributions to Japanese eel (Anguilla japonica) preleptocephali spawned on different nights

“…Because half‐sibs shared one parent, but had a different second parent, the presence of half‐sib pairs and triplets (Supporting Information Table S4) suggested that several parents might aggregate and spawn. Previous aquarium experiments with artificially matured Japanese eels (Dou et al ., 2007; Tsukamoto, 2009) and European eels (van Ginneken et al ., 2005; van Ginneken & Maes, 2005) suggested that they spawn by polygamy or group mating, because female–female or male–female pairs would frequently come together in the water column prior to releasing gametes. The results of the present and previous studies indicated that Japanese eels could form spawning aggregations in which multiple parents mate with multiple partners.…”