IJA Volume 56, Issue 4, 2004

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    Alteration Of Renal Tissue In Nile Tilapia, Oreochromis Niloticus, After Transfer To Saline Water
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) Benli, A.C. Karasu ; Yildiz, H. Yavuzcan
    Changes in renal tissues and plasma osmolality were investigated in Nile tilapia (Oreochromis niloticus) 72 hours after transfer from fresh water to 9 or 18 ppt salinity. Exposure to high salin- ity was associated with cell infiltration into renal tissue. Plasma osmolality increased with increasing salinity but the hematocrit remained unchanged.
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    Masculinization Of Genetic Females Of The Common Carp (Cyprinus Carpio L.) By Dietary Administration Of An Aromatase Inhibitor
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) Tzchori, Itai ; Zak, Tatyana ; Sachs, Ofer
    In the present study, we demonstrated the ability of Fadrozole, an aromatase inhibitor, to induce sex inversion of genetically female common carp fry during the critical sex differentiation period. Thirty-day-old female fingerlings with a mean initial weight of 4.0 g (experiment I) and 3.5 g (experiment II) were fed a diet containing Fadrozole for 36 or 50 days, respectively. Not a single male was found in the control groups of both experiments. In experiment I, Fadrozole at 200 mg/kg feed resulted in 58.6% males, while fish receiving 17α-methyltestosterone at 50 or 100 mg/kg feed resulted in only 5-10% males. In experiment II, the efficiency of Fadrozole was dose- dependent; the lower dose of 100 mg/kg caused masculinization in 86% of the treated fry while the higher doses of 200 and 400 mg/kg feed increased the percentage of males to 97%. These results confirm the importance of aromatization during the labile period in common carp since low aromatase activity during this period, regardless of genotype, resulted in masculinization.
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    In Vitro Melatonin Rhythm Reveals A Clocked Pineal In The European Sea Bass, Dicentrarchus Labrax
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) Ron, Benny
    The melatonin-generating system of the European sea bass, Dicentrarchus labrax, was studied in vitro using a perfusion tissue culture methodology. The examined properties included photic entrainment in the pineal gland, and circadian rhythmicity in alternating dark and light, in contin- uous darkness, and in continuous light. Pineal glands were removed from adult fish and placed in a perfusion tissue culture at a constant temperature of 24°C. Melatonin discharge into the cul- ture medium was measured using radioimmunoassay. Melatonin concentrations during a pho- toperiod of 12h light:12h dark were low during the light periods and high during the dark. The melatonin discharge was inhibited by continuous light but strong and rhythmic in continuous dark with a circadian period (Tau) of about 24 h (n = 10). The results demonstrate that the European sea bass pineal gland is photosensitive, with ability to be entrained, and contains an internal cir- cadian oscillator that regulates melatonin production.
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    Effect Of Feeding Frequency On Consumption, Growth, And Efficiency In Juvenile Tilapia (Oreochromis Niloticus)
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) Riche, Marty ; Oetker, Michael ; Haley, David I. ; Smith, Tiffany ; Garling, Donald L.
    Triplicate groups of juvenile Oreochromis niloticus (34.4 g) were fed a commercial diet once, twice, three, or five times a day for 29 days. Consumption, growth, and feed utilization were eval- uated. No significant differences in growth, feed efficiency, or protein utilization were detected among the fish fed two, three, or five times daily, but all were significantly better than in fish fed only once. Fish fed three meals had significantly higher gross energy and lipid and lower crude protein contents than fish in the other treatments (p<0.05). Energy retention in fish fed three times daily (84.7%) was significantly higher than in fish fed five times (49.4%). Feeding juvenile tilapia nutrient dense pelleted feeds obviates the need for frequent feedings.
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    Effect Of Feed Type On Growth And Fertility In Ornamental Fish, Xiphophorus Helleri
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) James, Raja ; Sampath, Kunchitham
    The effects of feed type on feed intake and conversion, ovary weight, and fertility were studied in red swordtail, Xiphophorus helleri, for 235 days. Five groups of 30-day-old juveniles (0.05±0.001g; 16.84±1.59 mm) were fed Artemia, earthworms, liver, pelleted feed, or a mixed diet. Mean body length and weight were higher in fish that consumed the mixed diet or Artemia than in those that consumed the other diets. Pelleted feed produced the highest feeding rate but the poorest conversion rate. Fish fed pelleted feed consumed 143 mg/g/day, which was con- verted into 13 mg/g/day flesh. Those fed the Artemia, earthworm, liver, or mixed diets consumed 46, 56, 89, and 84 mg/g/day, repectively, which were converted into 16, 18, 21, and 24 mg/g/day, respectively. The conversion rate dropped after parturition, possibly due to allocation of a major portion of the feed energy to development of gonads and young. Irrespective of feed type, gonads appeared on day 42. On day 84, the gonad weight of fish fed earthworms was 16 mg (wet weight), significantly (p<0.01) increasing to 25 mg in fish fed Artemia, 31 mg in fish fed liver, 86 mg for pellets, and 145 mg for the mixed diet. A similar trend was noted in the gonadosomatic index. Females fed the mixed diet, Artemia, and liver released 753, 612, and 509 fry in four breeding cycles while those fed earthworms and pellets bred only three times, releasing 315 and 155 fry, respectively.
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    Use Of Nitrification Inhibitors To Increase Efficiency Of Nitrogenous Fertilizers In Aquaculture
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) Thakur, Amrita ; Banerjee, Abira ; Chattopadhyay, G.N.
    High doses of nitrogenous fertilizers are often applied in fishponds but only a small part of the added nitrogen is utilized for improving primary productivity and, thereby, fish yields. A large por- tion of the nitrogen is lost from the pond environment through various mechanisms, especially nitrification. In the present investigation, we studied the effects of three nitrification inhibitors: (a) neem (Azadirachta indica) extract, (b) karanj (Pongamia glabra) extract, and (c) sodium azide (NaN3), on the transformation of applied nitrogen in simulated fishpond conditions. The study revealed that nitrification inhibitors considerably retard the rate of nitrification from the ammoni- um form of nitrogen (NH4+), resulting in a higher amount of nitrogen in the soil and water. The increased nitrogen concentration significantly increased gross primary production and, hence, improved the efficiency of the added nitrogen.
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    Correlation Between Biochemical And Spermatological Parameters In Rainbow Trout (Oncorhynchus Mykiss) Semen
    (Israeli Journal of Aquaculture - BAMIGDEH, 2004) Secer, Selçuk ; Tekin, Necmettin ; Bozkurt, Yusuf ; Bukan, Neslihan ; Akcay, Ergun
    Levels of biochemical parameters in seminal plasma and physical parameters of rainbow trout (Oncorhynchus mykiss) semen were determined and compared. Seminal plasma contained 80.51±31.48 mmol/l Na+, 46.21±12.58 mmol/l K+, 4.65±1.57 mg/dl Ca2+, 3.48±1.18 mEq/l Mg2+, 112.5±25.93 mmol/l Cl-, 1.33±0.76 mg/dl glucose, 0.15±0.09 g/dl protein, 2.55±2.47 mg/dl cho- lesterol, 8.0±2.84 mg/dl triglyceride, and 31.65±40.78 mg/dl urea. Semen volume was 19.9±21.43 ml, spermatozoa motility 60.0±30.09%, duration of spermatozoa movement 174.0±1.82 s, spermatozoa concentration 1.52±0.70 x 109/ml, total spermatozoa number 44.25±64.59 x 109, and pH 6.7±0.25. There were significant positive correlations between semen volume and Na+ (r = 0.667, p<0.05), total spermatozoa number and semen volume (r = 0.977, p<0.01), total spermatozoa number and spermatozoa concentration (r = 0.652, p<0.05), Na+ and Cl- (r = 0.733, p<0.05), Na+ and triglyceride (r = 0.632, p<0.05), K+ and protein (r = 0.728, p<0.05), and Ca2+ and protein (r = 0.685, p<0.05). Significant negative correlations were found between Cl- and glucose (r = - 1.00, p<0.05), and triglyceride and urea (r = -0.716, p<0.05). Consequently, although there were no definite correlations between biochemical and spermatological parameters, it was observed that a higher Na+ content has a positive effect on semen volume.