IJA Volume 55, Issue 2, 2003

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    Growth And Feed Consumption Of Young Rainbow Trout (Oncorhynchus Mykiss) Exposed To Different Photoperiods
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Ergün, Sebahattin ; Yigit, Murat ; Türker, Ali
    A feeding experiment was carried out in a brackish water (18 ppt) flow-through system to deter- mine the effects of different photoperiods (light hours/dark hours; L/D) on feed intake and growth performance of young rainbow trout (Oncorhynchus mykiss). Duplicate groups of fish (35.32 g avg body wt) were exposed to a natural photoperiod, a long photoperiod (16L/8D) or a continu- ous photoperiod (24L/0D) for 60 days and fed to satiation twice a day. The growth rate, daily feed intake and feeding rate in the natural photoperiod were significantly lower (p<0.05) than in the long and continuous photoperiod groups. Growth was highest in the continuous photoperiod, but did not significantly differ from the long photoperiod. The feed conversion ratio, feed efficiency and gross efficiency in the long and continuous photoperiods were slightly better (about 5-7%) but did not significantly differ (p>0.05) from the natural photoperiod. Survival was not significantly (p>0.05) affected by the treatment. For better growth and a lower food conversion rate, the long photoperiod is recommended for young rainbow trout.
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    The Influence of Multiple Meals On The Gastric Evacuation Rate In Rainbow Trout (Oncorhynchus Mykiss)
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Tekinary, Ahmet Adem ; Güner, Yusuf ; Akbas, IIhan ; Baysal, Hüsnü
    Rainbow trout, Oncorhynchus mykiss (mean weight 70.8±1.0 g SEM) raised in the Sea of Marmara (Turkey), were used for a preliminary gastric evacuation study. After being starved 72 hours, three groups of 110 fish, each, were fed ad libitum once, twice or three times in a single day. Ten fish from each group were withdrawn and killed in an anesthetic solution during each sampling at 0, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 hours following the last feeding. Gastric material was removed from the fish and dried for gastric evacuation modelling. Gompertz and logistic models (with fixed asymptotes) best explained the data. The gastric emptying rate of the trout offered a single meal (Group A) was faster than those fed two (Group B) or three (Group C) meals while the emptying patterns of Groups B and C were similar to each other. The time required to evacuate 95% of the gastric material from the first meal was estimated as 54.3, 68.0 and 67.8 h for Groups A, B and C, respectively, according to the Gompertz equations (with a fixed asymptote).
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    The Gut Contents Of Grass Carp, Ctenopharyngodon Idella, Drug Nursing In An Earthen Pond
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Kirkagaç, Mine Uzbilek
    Grass carp fry (0.04±0.01 g avg wt; 1.48±0.03 cm total length) were stocked into an earthen pond in June. Every week for twelve weeks, fifteen fish were sacrificed and the content of their guts was examined. At the first week, animal material represented 74% of the gut contents. From the second week onwards, plant material was higher (mean value 79%). In the seventh week, when grass carp reached 4.83±0.09 cm, filamentous algae were replaced by macrophyte frag- ments. Besides the macrophytes, animal material such as the rotifers Monostyla and Lecane and the cladoceran Bosmina were found and the proportion of animal material in the gut varied 11-26%.
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    Food Competition In Small Groups Of Juvenile Gilthead Sea Bream (Sparus Aurata)
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Goldan, Oded ; Popper, Dan ; Karplus, IIan
    Four groups of single-size and four groups of mixed-size gilthead sea bream (Sparus aurata) were raised in small observation cells for 16 days. Each group consisted of four individually marked juveniles. Agonistic behavior, motor activity and feeding behavior were monitored on days 1, 4, 10 and 16. At the end of the study, the weight gain was measured. Aggressive interactions occurred almost exclusively during feeding. A linear dominance hierarchy stabilized sooner in the mixed groups than in the single-size groups. Rank in the hierarchy had a profound effect on the behav- ior and growth of all group members. The dominant fish in each group carried out more aggres- sive acts and bit at food particles more often than the other group members. The dominant fish also had the highest relative specific growth rate. Direct competition for food is probably the major social mechanism regulating growth in small groups of juveniles of this species when food is lim- ited and defendable. The relevance of these findings for the commercial culture of this species is discussed.
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    Thermal And Hormonal Feminization Of All Male YY Nile Tilapia, Oreochromis Niloticus L.
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Karayücel, Ismihan ; Penman, David ; Karayücel, Sedat ; McAndrew, Brendan
    Hormonal and thermal sex reversal of YY male Oreochromis niloticus were compared. While similar percentages of females (34% and 32%, respectively) were produced, a significantly high- er percent of intersex individuals (18.5%) was produced in the heat (36oC) treatment than in the group treated with diethylstilbestrol (DES; 1.6%). The heat-treated groups had 62.6% survival, compared to 97.0% and 97.3% in the control and DES-treated groups, respectively. Our results demonstrate that a high temperature treatment can be an alternative to hormonal sex-reversal treatments for YY male O. niloticus. Although the low survival and high occurrence of intersex individuals may limit its use, it can be used to produce large numbers of YY male broodstock in countries where hormone use is illegal and/or consumer reaction to hormonally-treated fish is negative.
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    Carbon Dioxide Removal Rate By Aeration Devices In Marine Fish Tanks
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Eshchar, Micha ; Mozes, Noam ; Fediuk, Michael
    A procedure for measuring the transfer coefficient KLa for the removal rate of carbon dioxide by aeration devices in fish tanks was developed in the National Center for Mariculture in Eilat, Israel. The KLa for a paddlewheel and a submerged aerator were calculated, following experi- ments in which the aeration devices were used simultaneously for both carbon dioxide stripping and oxygenation. The paddlewheel was more efficient, with a transfer rate up to 1,200 g CO2 per hour and a stripping efficiency of 1.2 kg CO2 per kWh. In intensive sea bream culture, the cal- culated maximum feed load that a single paddlewheel aerator can support is 43.6 kg feed per day with an energy requirement of about 1.0 kWh per kg fish produced.
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    Genetic Variation In Strains Of Discus (Symphyodon Aequifaciata) Using RAPD PCR
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Degani, Gad
    The DNA of five strains of discus (Symphyodon aequifaciata) were compared by random ampli- fied polymorphic DNA (RAPD PCR) using seven primers. Only two primers (ZG4 and ZG8) were suitable. Using primer ZG8, the red turquoise strain had five bands common to at least one fish of another strain and two bands common to all the fish in the red turquoise strain. Panda turquoise had one band in common with at least one fish of another strain and seven bands common to all panda turquoise. For royal red, these figures were five and one and for common brown they were three and one. Within the strains, the level of band-sharing was 0.83 in the red turquoise strain, 0.13 in the panda turquoise, 0.83 in the royal red and 0.75 in the common brown. Specific bands were found only with primer ZG8 in the common brown and panda turquoise strains. Using primer ZG4, very low variation was found between the royal red, cobalt blue and red turquoise strains. With both primers, the highest genetic variation was between the common brown strain and the others (0.33-0.83).
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    Effects Of Hydrogen Peroxide, Cold Storage And Descapsulation On The Hatching Success Of Artemia Cysts
    (Israeli Journal of Aquaculture - BAMIGDEH, 2003) Saygı, Yasemin (Basbug)
    The effects of hydrogen peroxide, cold storage and decapsulation on diapause in partheno- genetic Artemia cysts from the Izmir Çamalti saltern were tested. To test the effect of hydrogen peroxide, cyst samples were incubated for 5 min in a 2% or 5% H2O2 solution. In the cold stor- age experiments, the cysts were divided into three groups. One group was stored in saturated saline, the second in a vacuum and the third in air for 15 days or one month. Decapsulation was tested after a 2-hour prehydration period. The hatching rate of the control group after 24 h in cysts harvested in November was 0, while in cysts harvested in March it was 19.2%. All the treatments for diapause deactivation resulted in increased hatching during the first 24 h but the final hatch- ing rates (at 72 h) of all treated groups were similar to or slightly lower than that of the control.