IJA Volume 54, Issue 4, 2002
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ItemClinical And Pathological Investigation Of Psychrobacter Immobilis Infection In Rainbow Trour (Oncorhynchus Mykiss, Walbaum)(Israeli Journal of Aquaculture - BAMIGDEH, 2002)The pathogenicity of Psychrobacter immobilis, isolated from naturally infected rainbow trout Oncorhynchus mykiss, was investigated. In experimentally-infected trout, no mortality was recorded during 35 days but the following external and internal symptoms were observed. Externally, skin was darkened, gills were pale and swimming was abnormal. Internally, there were dilatations of the vascular structures on cross-sections of the liver; vascular congestion, inflammatory mononuclear cell infiltration and degeneration in the gills; interstitial inflammatory mononuclear cell infiltration and free bleeding in patches of the posterior kidney; vascular con- gestion and free bleeding in the spleen; degeneration, atrophy, polymorphonuclear leukocyte infiltration and liquefaction necrosis in muscle fibers; edema, inflammatory mononuclear cell infil- tration and basophilic degeneration among muscle fibers of the heart; and congestion in vascu- lar structures on cross-sections of the brain tissue. It is suggested that P. immobilis is an oppor- tunist pathogen that causes secondary infections.
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ItemProduction Of Androgenetic Nile Tilapia, Oreochromis Niloticus L.: Optimization Of Heat Shock Duration And Application Time To Induce Diploidy(Israeli Journal of Aquaculture - BAMIGDEH, 2002)Diploid androgenetic Nile tilapia, Oreochromis niloticus, were produced using 5 min UV irradia- tion at 150 μW/cm and heat shock at 42.5oC for 3:30 min applied 25 min after fertilization. The survival rates to morula, pigmentation, hatching and yolk sac resorption stages were 42.84±4.73%, 10.69±2.24%, 2.03±0.60% and 0.07±0.07% (relative to controls), respectively. A significant female, but not male, effect on the survival was confirmed. Multilocus DNA finger- printing produced by hypervariable 33.15 DNA probe verified the all-paternal inheritance in the androgens. The sex ratio of the androgenetic tilapia was not significantly different from the expected ratio of 1:0 (male:female), indicating that O. niloticus has a monofactorial sex-deter- mining mechanism with female homogamety and male heterogamety. This study confirmed that the YY genotype is viable and fertile in O. niloticus.
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ItemSpat Settlement And Growth On A Long-line Culture System Of The Mussel, Mytilus Galloprovincialis, In The Southern Black Sea(Israeli Journal of Aquaculture - BAMIGDEH, 2002)Spat settlement and growth at the depths of 3 and 7 m in a long-line mussel system in the south- ern Black Sea were determined in two seasons. The first spat collectors were hung in July 1997, the second in January 1998. Temperature, salinity, seston, particulate organic matter and chloro- phyll-a were measured monthly. Depth had no significant effect on any of these parameters (p>0.05). There was a significant positive correlation between particulate organic matter and chlorophyll-a (p<0.05) at both depths. On the first collectors, most of the spat settled from October to January and on the second most settled in April-May 1998. The mean shell length, height, width and weight of the mussels from the first collectors were 32.11±0.68, 18.32, 11.76±0.35 mm and 3.40±0.22 g, respectively. Spat collectors were most efficient in February and March when heavy spat settlement occurred and predation and fouling were minimal. Growth performance of seeds was high due to the favorable environment. Recommendations for spat collection and cultivation are given.
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ItemGrowth And Survival Of Penaeus Merguiensis Postlarvae At Different Salinities(Israeli Journal of Aquaculture - BAMIGDEH, 2002)The growth and survival of postlarval Penaeus merguiensis were examined to optimize condi- tions and improve farm production. Postlarvae were subjected to one of four salinities (5-35 ppt) for a period of 28 days. Results indicated maximum survival at 25 ppt while the best growth rate was obtained at 15 ppt. The highest performance index was obtained at 15 ppt. Hence, 15 ppt was found to be the optimum salinity for the production of P. merguiensis postlarvae. The fast growth rate and good tolerance of P. merguiensis larvae to a wide range of salinity in captivity indicate that P. merguiensis is a promising candidate for aquaculture.
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ItemMilt Production Of Sea Bass Lates Calcarifer Bloch Administered An Analogue Of Luteinizing Hormone-Releasing Hormone And 17α-Methyltestosterone(Israeli Journal of Aquaculture - BAMIGDEH, 2002)The milt production responses of sexually mature sea bass Lates calcarifer to (D-Ala6, Pro9-N- ethylamide) luteinizing hormone-releasing hormone (LHRHa) and 17α-methyltestosterone injec- tions were examined. At 24 h after injection of a low dose of LHRHa (20 μg/kg BW), the sperm count decreased significantly compared to saline-treated fish, but it returned to pre-treatment levels 48 h after injection, suggesting a possible hydration of the milt. Other milt parameters (milt volume, sper- matocrit, sperm production) in LHRHa-treated fish did not vary from their controls at 24 or 48 h after injection but the overall pattern suggested a reduction in milt viscosity. Total expressible milt and spermatozoa collected over the 48-h experiment was approximately three-fold higher in LHRHa-injected fish than in saline-injected fish, indicating a stimulation of spermatozoa produc- tion, not merely milt dilution due to hydration. In a second experiment, sperm count and spermatocrit were significantly lower than those of saline-injected fish at 17 and 48 h after a single injection of a high dose of LHRHa (80 μg/kg BW). A methyltestosterone injection combined with the LHRHa injection also resulted in a significant- ly lower sperm count, but the spermatocrit remained comparable to the control group, suggest- ing a suppression of the LHRHa-induced milt hydration response. Results demonstrate that LHRHa stimulates milt hydration and spermatozoa production in milting sea bass and that a simultaneous methyltestosterone injection partially suppresses this response.
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ItemDietary Threonine Requirement Of Indian Major Carp, Cirrhinus Mrigala (Hamilton), Juveniles(Israeli Journal of Aquaculture - BAMIGDEH, 2002)A growth study was conducted to determine the dietary threonine requirement of juveniles of the Indian major carp (Cirrhinus mrigala) known as “mrigal”. Diets containing casein and gelatin as sources of intact proteins were supplemented with crystalline amino acids to obtain a crude pro- tein content of 40%. Six diets with different levels of threonine (1.0, 1.3, 1.5, 1.7, 1.9 and 2.1%) were fed to triplicate groups of mrigal juveniles twice a day for 56 days. The dietary threonine requirement, estimated by break-point analysis, was 1.66% of the dry diet (4.15% of the dietary protein). The highest growth and specific growth rate were recorded in fish fed the diet contain- ing 1.7% threonine.