The broodstock section has the same facilities available last year (9 round fiberglass spawning tanks and 12 outdoor concrete round tanks). The heating control system of the seawater supply has been improved. Its 3-way valve is now regulated electronically.
Two improvements recommended by the consultant at the end of his previous mission have been realized.
First, a group of four spawning tanks has been connected to the cooling system, making it possible to lower the water temperature. Since the light control is already available, four groups of breeders can now be conditioned in order to induce an earlier maturation and spawning.
Second, an asbestos cement roofing has been installed over the outdoor tanks to shade from the sun.
The earth ponds foreseen by the project as long term broodstock holding facilities remain not realized.
This year larger stocks of seabream and seabass breeders were available. The broodstocks used the last season have been incremented with animals coming from cage farms (Bodrum area) and from the Beymelek Lagoon. The lagoon gave many fluent seabream males (no female seabream was found) and about twenty seabasses. The animals were captured by means of the fish barrier at the lagoon mouth and by trammel nets. In female seabasses gonadal maturation was not completed due to the low salinity of the lagoon waters. They can be used the next season.
All the existing stocks of female breeders of both species have been treated with hormone to induce spawning either this year or the previous one, or both (Annex 1). Fish treated last year with hormone (hCG) gave good results to a second treatment with the same hormone this year, meaning that they were properly reared during their rest period. However, due to the risk of refractoriness to that hormone after following treatments, it is suggested not to reuse the next season those females that have received hCG treatment for two following years (Annex 1). The other hormone used, LH-RHa, does not cause refractoriness.
It is however highly recommendable to recruit other healthy female breeders of both species, possibly from the wild, for the next production season to assure continuity of results, in particular for seabream (see Recommendations for more datails).
Based on the experience of the present season, it is adviced not to rely too much upon the nearby lagoon for the recruitment of large numbers of female breeders, seabream in particular. On the contrary, recruitment of fluent male seabreams does not represent a constrain since there are plenty of them in the lagoon.
Since the handling and feeding protocols have not been modified from the previous year, they are not reproduced here.
No mortality due to manipulation was observed.
Also this season, no spawning occurred naturally and all females gave eggs only after hormonal treatment. Male breeders had no problem (as usual) to release sperm.
Two different hormones were employed: the human chorionic gonatropin (hCG, the same hormone used during the last reproductive season) and a synthetic analogue of the luteinizing hormone-releasing hormone (des-Gly10-[D-Ala6]-LH-RH-EtA, produced by Sigma, USA).
The latter, a superactive non-immunogenic peptide, replaced hCG since its use might lead to an immune response in treated fish and refractoriness to the hormone. However all seabreams treated with LH-RHa (5 μg/kg b.w. given two times) gave very poor results (Annex 5, batches 1 to 9) compared with treatments with hCG (Annex 5, batches 10 to 25). It is possible that breeders were not fully mature for that hormonal treatment, as suggested by the increase of fertility rates and egg quality (expressed as % of viable eggs at harvest time) in time (Annex 6). Hormone dosage could also be questioned, even if research evidenced better results with such low dosages in seabreams.
After the failure of LH-RHa, the remaining batches of spawners of both species were treated with hCG only. On average only half dose (500 IU/kg b.w.) was given one time instead of two compared with the treatment given the previous season.
As usual, before treatment fish was submitted to ovarian biopsy and only fish showing oocytes greater than 500 μm (seabream) and 750 μm (seabass) in diameter was injected. Only female spawners were treated.
Only three groups of seabreams (batches 10, 11 and 12) received a second treatment of 500 IU/kg b.w. short after the end of their first spawning period (Annex 6). Their second spawning period was shorter in time and give less eggs of lower quality than the first one (Annex 3 and 6).
In both seabream and seabass spawning started 48 to 55 hours after hormone injection.
Eggs were collected by means of floating collectors. The use of overflow collectors was discontinued last year because less effective and more stressful for eggs.
A total amount of about 16.6 kg viable seabream eggs and 9.5 kg viable seabass eggs was produced (Annex 4). Monthly productions are listed in Annex 2 (December 1994), Annex 3 (January 1995) and Annex 4 (February 1995). The greater production of seabream than last year is due to its lower final survival rate compared to seabass and to a increased demand by local farmers.
Due to the induced spawning, a large amount of non-viable eggs was also harvested (Annex 4). The overall lower quality of eggs due to induced spawning was also confirmed by the amount of viable eggs that died during the incubation phase, even if at a lower rate than the previous season. Around 15.2 kg seabream eggs and 11 kg seabass eggs were actually stocked into the larval tanks (Annex … and …).
Fertility rates and egg quality of this season are presented in Annex 7 together with the results of the season 1993–4 for comparison. Seabream average output was 41% higher than last season: average egg production expressed as percentage of body weight was 29.6% in 1994–5 against 21.0% in 1993–4. On the contrary, the percentage of viable eggs was slightly lower (11%). In seabass it was the opposite: a 17% decrease in production with a 15% increase of viable eggs than last year. Overall performances in both species remain however small, if compared with natural spawnings.
Average egg size and unit weight were bigger than one year ago, probably because of a better management of breeders during the rest season (Annex 8). However, at least in seabass, eggs remains smaller than those coming from natural spawning (Annex 8).
This section is usually staffed by one head and two workers (same as in 1993–4 season). When the spawning tanks are used for the larval rearing of seabass, staff is increased by adding two workers (Annex 22).
Since the instructions (feeding, weekly feeding schedule, ovarian biopsy and hormone treatment, egg harvesting and handling, daily working programme, cleaning procedures, weekly consumption of consummables and duty rota system) given the staff last season (Final Report dated May 1994) did not changed, they are not reproduced here.
