Boetius and Boetius, 1980



Citation


Boetius, I. and Boetius, J. (1980) Experimental maturation of female silver eels, Anguilla anguilla (L.). estimates of fecundity and energy reserves for migration and spawning. Dana, pp.

Associated characteristics


Species Development state Trait Primary Data Secondary Data
Anguilla anguilla Spawning conditions Mating system The number of participating males was 1-3 per female. During the first 15 minutes or so the male will swim around as if he were searching for someting while the female will remain almost quiet. When finally the male has detected the female he starts rubbing her belly with his head. He is especially attracted by her abdominal apertures. The female is thereby pushed slowly forwards through the water and starts a slow swimming. Still while the couple is moving, the stimulated male will try to obtain maximum contact between the bodies and is often seen to cling on the female with his back against her belly. When two or three males were placed together with one female they all tok part in the initial courtship. In every case, however, only one of the participating males released sperm during the experiment No category
Anguilla anguilla Spawning conditions Nycthemeral period of oviposition Only a few of our eels were direclty observed to spawn a significant amount of eggs. But no doubt several other eels at intervals (especially by night) have releaseed small amount of eggs Night
Anguilla anguilla Female Maximum GSI value Maximum GSI obtained in different studies: 12.6 only, 40 in other previous experiment and 60.7. 12.6 percent
Anguilla anguilla Female Relative fecundity The data in the present paper can be converted to average 1.6 million/kg, which is about half of the Russian figure 1.6 thousand eggs/kg
Anguilla anguilla Egg Temperature for incubation Incubated at 21-23°C 22.0 °C
Anguilla anguilla Egg Egg size after water-hardening Eel eggs during further development will swell to diameters of 2.3 to 2.9 mm 2.3 mm
Anguilla anguilla Egg Egg Buoyancy In sea water of 31 °/oo all eggs sink Semi-Pelagic
Anguilla anguilla Egg Oocyte diameter Eggs diameters are relatively uniform 1.05 ± 0.15 [Some discrepancy exists between different authors as to size of the European eel egg: 0.93-1.4, 1.0-1.1, 1.2-1.6, 0.9-1.1.3 mm] 1.05 mm
Anguilla anguilla Female Absolute fecundity The estimated fecundity of matured eels ranged from 0.7 to 2.6 million eggs [For immature eel the US authors give records of European specimens having 5-10 millions eggs on average with 15-20 million for the largest specimens] 7.5 thousand eggs
Anguilla anguilla Female Weight at sexual maturity Body weight of eels at catch averaged 0.8 Kg (range 0.5 to 1.5 kg) 0.8 kg
Anguilla anguilla Male Length at sexual maturity Male silver eels about 38 cm were brought to the laboratory 38.0 cm
Anguilla anguilla Male Weight at sexual maturity Male silver eels about 80 g were brought to the laboratory 80.0 kg