J.G.P. Klein Breteler
Organization for Inland Fishery Improvement, Nieuwegein, The Netherlands
ABSTRACT
Rudd, Scardinius erythrophthalmus L., was reproduced and reared in the hatchery. Methods used are described. An individual weight of 25 mg was achieved in 10 days at 15°C. Further propagation was carried out at temperature varying between 21 and 29°C and an average weight of 5.8 g was reached after another 110 days. Feed conversion using commercial trout feed (pellets) amounted to 2.2
RESUME
La Rotengle, Scardinius erythrophthalmus L., a été reproduite et élevé dans l'écloserie. Les méthodes appliquées sont decrites. Après 10 jours d'alevinage à une température de 15°C un poids moyen de 25 g a été atteint. Il a été essayé de poursuivre l'élevage à une température entre 21°C et 29°C, ce qui a permis d'obtenir, après 110 jours, un poids moyen de 5.8 g. En utilisant des granulés de truites, le quotient nutritif était de 2.2
At the EIFAC workshop on controlled reproduction of cultivated fishes in Hamburg (1976) it was stated that for a number of cyprinid fish species no experience on controlled reproduction existed. One of them was Scardinius erythrophthalmus and “attention was called to the lack of adequate information on its controlled breeding and to the need to disseminate any available data”.
Rudd (Scardinius erythrophthalmus L.) is reared for stocking purposes of natural waters in The Netherlands since 1966. Until 1978 pond culture propagation methods were used i.e. stocking the ponds with adult fish and harvesting after 1 or 2 years. In this way it proved possible to produce on the average 40 000 yearlings per hectare after 1 year or 12 000 fishes/ha after 2 years with an average body weight of 0.6 – 6.5 g and 4.8 – 34.5 g respectively. Despite the low stocking densities the growth rate appeared to be extremely low. The variation in length and weight within the fingerlings of one single year class was considerable, probably due to intermittent spawning.
In 1978 controlled reproduction of rudd was carried out successfully in Lelystad in the hatchery of the Organization for Improvement of Inland Fisheries and fingerlings were raised in cages in the thermal effluent of a conventional electrical power plant in the vicinity of the hatchery.
1 Group consisting of 2 batches of broodfish, with an average body weight of 600 and 150 g respectively, were kept in glassfibre basins in the hatchery at 22.5°C from mid March until mid April. Afterwards all females were injected with 0.3 mg carp pituitary per kg body weight and 18 hours later a second dose of 3.0 mg/kg was administered. Stripping by hand of the females started 12 hours after the second injection. 18 Hours after the second injection stripping was no longer performed.
Males were kept together with females in the same basins until the first hypophysation of the females, after which they were separated. Males were all stripped without hypophysation.
Another group of 25 females, with an average body weight of 650 g, was transferred from the ponds into hatchery at the end of May. 15 Females were hypophysized immediately with 3.0 mg carp pituitary per kg body weight and 10 females served as a control and were injected with a physiological salt solution.
Stripping procedures for males and females were the same as mentioned above. Males had been kept separate from females in the ponds as well as in the hatchery. Every time the spawners had been handled they were treated with malachite green (0.1 ppm for 1 hour) in order to prevent fungus development.
The results are shown in Table 1 and will be discussed shortly. Only 1 from the batch of 7 fishes of 600 g and 11 out of the batch of 63 smaller fishes of 150 g could be stripped and 13 000 and 62 000 eggs were obtained respectively.
From the second group, transferred to the hatchery at the end of May, 13 out of the 15 hypophysized females could be stripped and 900 000 eggs were obtained (Table I). From the non-hypophysized females only 2 out of 10 could be stripped, producing 15 000 eggs.
The eggs were fertilized by the dry method, (Huisman, 1976), stirred for 15 minutes in a fertilizing solution (2‰ NaCl, 1.5‰ Urea) and treated twice, for 8 and 3 seconds respectively, with a solution of 0.35‰ tannic acid to remove stickiness.
The first group of eggs, collected in the middle of April, was incubated in 6 trays (12.000/tray) in a Californian incubator at 22.5°C. The water flow rate amounted to 6 1/min. The eggs, which had not been checked for fertilization percentage, hatched at the 5th day of incubation.
The second group of eggs, collected at the end of May, was incubated in cone-shaped 17 1 hatching jars (improved Elf-jars) at 19.5°C. The stocking density amounted to 300.000/jar and the water flow rate was 2 1/min. The fertilization rate of the eggs, determined by counting the viable eggs after 10 hours incubation in a sample of 4500 eggs, amounted to 74%. These eggs also hatched at the 5th day of incubation.
On the first and the second day of incubation the eggs were all treated with malachite green (15 ppm for 1 minute) in order to prevent fungus development.
The first groep fry (April) stayed in the Californian incubator until the 2nd day after hatching, when they started to eat. Sieved hard-boiled egg-yolk was fed twice on this day. After that sieved zooplankton (80 to 125 μm) was administered. On the 3rd day after hatching a group of 10.000 fry, with an average body weight of 5.0 mg, was transfered into aquaria (120 1) and was cultured up to the fingerling size. Mortality rate until the 3rd day after hatching had not been determined.
At the hatching stage the second group of larvae (May–June) was transferred into small gauze cages in a basin with running water of 19.5°C in the hatchery. Feeding procedures were the same as mentioned above. On the 3rd day the fry were used for the stocking of ponds. Mortality rate from the egg stage until the 3rd day after hatching amounted to 62%.
A group of fry was cultured up to the fingerling size. Two aquaria (120 1) were stocked each with 5.000 fry with an average body weight of 5.0 mg. Until the 10th day they were fed with sieved zooplankton (80 to 125 μm) at a temperature of 15°C. During this period the water was refreshed twice. Losses were negligible.
After a body weight of 25 mg was reached, they were transfered to a basin (4 m3 filled up to circa 1500 1) with running water of 22.5°C and fed zooplankton of increasing size from the 10th to 30th day. Later on they were fed a commercially available pelleted trout food (trouvit) by means of a Scharflinger conveyor belt feeder.
Fingerlings were treated twice a week with malachite green (0.1 ppm for 1 hour) against fungus and ectoparasites and with furanace (10 ppm for 1 hour) against Myxobacteria spp.
After 80 days losses of fingerlings amounted to 43% mainly because of predation by perch fingerlings, which had been introduced by accident into the basin as fry, together with the zooplankton fed. At this time an average weight of 1 g had been achieved.
At this stage the fishes were transferred for another 40 days into a cage (6.5 m3) in the cooling water discharge canal of a power station. Temperatures ranged from 21 to 29°C. The result are shown in Table II. Growth rate amounted to 4.5% of body weight per day and food conversion was 2.20 using trout pellets. Losses were negligible during the period in which cage culture took place.
Artificial reproduction of rudd provided possible using the same technics as for carp (Cyprinus carpio L.)
Mass rearing of fry and fingerlings in the hatchery was more difficult, mainly due to the low initial weight and low growth rate, which resulted in a longer dependence on natural food and vulnerability to accidentally introduced predatory perch fingerlings. Notwithstanding these difficulties artificial propagation of rudd, using hatchery procedures, seems to be a promising alternative for conventional pond farming methods and merits further research.
EIFAC, 1976 Workshop on controlled reproduction of cultivated fishes. EIFAC Tech. Pap., 25: 180 pp.
Huisman, E.A., 1976 Hatchery and nursery operations. EIFAC Techn. Pap., 25: 102 – 110.
Table I. Hypophysation success and egg production of female rudd, Scardinius erythrophthalmus L.
| number of females | body weight (g) | 1st hypophysation | 2nd hypophysation | females stripped | number of eggs ontained1) | number of eggs per female | |||
| date | dose (mg/kg) | date | dose (mg/kg) | number | % | ||||
| 7 | 600 | April 15 | 0.3 | April 16 | 3.0 | 1 | 14 | 13 000 | 13 000 |
| 63 | 150 | April 15 | 0.3 | April 16 | 3.0 | 11 | 17 | 62 000 | 5 636 |
| 15 | 650 | May 30 | 3.0 | -- | - | 13 | 87 | 900 000 | 69 231 |
| 10 | 650 | May 30 | - | -- | - | 2 | 20 | 15 000 | 7 500 |
1) 1 gram of eggs equals ± 1.300 eggs
Table II. Growth and feed conversion of fingerlings of rudd, Scardinius erythrophthalmus L., during 40 days in a cage
| start | after 40 days | growth rate % body weight/day | food conversion | ||
| number | body weight (g) | number | body weight (g) | ||
| 5 700 | 1.0 | 5 700 | 5.8 | 4.5 | 2.2 |
