Production of cyprinids for re-stocking purposes - Part 2. Out-of-season spawning
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, Aquaflow ref. :
TL2003-201
One of the most important problems in cyprinid
aquaculture is obtaining good quality gametes. For this reason, many
hormonal treatments are used to stimulate gamete maturation. In some cases,
the changing of spawning time is needed, especially when many fish species
are spawned in the hatchery. Earlier spawning gives the possibility to
produce longer and heavier juveniles, and this is important for farm
economy.
In
this project, some wild cyprinid species were subject to tests on
reproduction before the normal spawning season: asp (Aspius
aspius), dace (Leuciscus leuciscus),
ide (Leuciscus idus) and chub (Leuciscus
cephalus). Spawners were caught in October from natural waters. Fish
were transported to the hatchery and kept in 1000-L tanks with controlled
temperature and photoperiod. During first few weeks, the water temperature
and light conditions were quickly decreased to 2°C and 2hrs of light per
day, respectively. Fish were kept under these “Winter” conditions for
the next few weeks. Later, both environmental conditions were increased to
try to induce spawning in January. The temperature and photoperiod regimes
were different for different species. Before spawning, fish were kept in
water temperatures similar to those at season-time spawning. Fish from both
sexes and all species were divided into three groups, two experimental and
one control. After five days of acclimation to the optimal temperature, the
fish were treated with hormonal injections of common carp pituitary (Argent,
USA) extract with the addition of hCG, or GnRHa with dopamine antagonist
(ovopel pellets). All spawning agents were prepared with 0.9% NaCl:
pituitary extract was homogenized, hCG dissolved and ovopel pellets were
pulverized in a mortar and then dissolved. Injections of hCG were
intramuscular in the dorsal area of the body. Injections of pituitary and
ovopel extracts were intraperitoneal at the base of the pelvic fin. Before
manipulations, fish were anaesthetized with 2-phenoxyethanol (0.5mg.l-1).
Time intervals between injections are 24 hrs.
The
results showed that in treated species, both environmental conditions (light
and temperature) are important, and their manipulation is needed to achieve
successful spawning. All males from the experimental groups spermiated and
fish treated with CPE and hCG produced the highest volume of milt. Males
from both treated groups gave sperm with higher motility than those from the
control group. All females from treated groups ovulated (except chub–over
40%), which strongly contrasted with the control group, where no ovulation
was observed. It is suggested (as in the case of artificial spawning during
spawning season), that hormonal stimulation is needed to obtain gametes. The
latency time was species-dependent and was over 30hrs. The average embryo
survival to the eyed-egg-stage was over 60%. All recorded parameters were
lower than those obtained during artificial propagation in spawning season.
This was especially noted in the case of males. Males from control groups
produce only a very limited number of sperm with very poor motility. Without
hormonal stimulation, mass spawning is impossible.
For more information, contact:
KUCHARCZYK Dariusz
University of Wamia and Mazury in Olsztyn - Department of Lake and River
Fisheries
Oczapowskiego 5
PL-10-719 Olsztyn-Kortowo
Poland
Phone : +48 89 523 4436
Fax : +48 89 523 3969
e-mail: darekk@moskit.uwm.edu.pl