980 resultados para Tilapia mariae


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El sector piscicultor en el Huila presenta un potencial para el departamento y el país que debe ser explotado, buscando el desarrollo de ventajas competitivas sostenibles que lleven al crecimiento, expansión y desarrollo en general del sector. El presente trabajo pretende explorar diferentes estrategias que pueden ayudar al desarrollo de estas ventajas competitivas. Realizando una evaluación de diferentes factores que influyen en el sector de acuerdo con el Diamante de la competitividad de Michael Porter y explorando la cadena de valor de las empresas del sector, generamos un análisis de Debilidades, Oportunidades, Fortalezas y Amenazas (análisis DOFA) para generar una visión de las estrategias a seguir en la generación de valor. Luego de explorar las posibles estrategias que podría seguir el sector, encontramos unos puntos que se vuelven común denominador: la generación de marca para el reconocimiento de los productos en los consumidores finales y el desarrollo valor agregado a través de nuevos productos o llegando a nuevos segmentos de mercado. Teniendo en cuenta las experiencias internacionales que han tenido otros sectores, es recomendable que las empresas del sector piscicultor del departamento del Huila generen espacios de cooperación (a manera de clúster) en los cuales se tengan objetivos enfocados en la generación ventajas competitivas para todo el sector y el fortalecimiento de una marca que sea reconocida internacionalmente.

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The effects of aluminum on plasma ion, lipid, protein and steroid hormone concentration were evaluated in Oreochromis niloticus broodstock females. Lipid and protein concentrations from the gonads and liver were also measured Experiments were performed at neutral and acidic water pH Four groups of fish were tested for 96 h. 1) control conditions at neutral water pH, 2) control conditions at acidic water pH (CTR-Ac). 3) aluminum at neutral water pH (Al-N), and 4) aluminum at acidic water pH (Al-Ac) Aluminum and acidic water pH exposure caused no ionoregulatory disturbances Total lipid concentration increased in the mature gonads and decreased in the liver, suggesting an acceleration of lipid mobilization to the ovaries in animals exposed to aluminum However, a decreased protein concentration in ovaries was also observed Exposure of control fish to acidic water pH caused an increased concentration of plasma 17 alpha-hydroxyprogesterone However, females exposed to aluminum at acidic water pH showed a decreased of plasma 17 alpha-hydroxyprogesterone and cortisol. No differences in plasma 17 beta-estradiol were observed The physiological mechanisms underlying the disturbances observed are discussed focusing on reproduction We suggest that aluminum can be considered an endocrine disrupting compound in mature O. mloticus females (C) 2010 Elsevier Inc. All rights reserved

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Samples of the muscle and liver of tilapia (Oreochromis mossambicus) obtained from the five reservoirs in four catchments in southern Sri Lanka in 1998 were analyzed for 16 elements: As, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn by inductively coupled plasma emission spectrophotometry, and Hg by atomic absorption spectrophotometry. The concentrations of Cr, Ni, and Pb were below the detection limits of the instrumental techniques employed in all samples. The elements As, Ca, Co, Cu, Fe, Hg, K, Mg, Mn, Na, Sr, and Zn were detected in the muscle and liver tissue, with Cd detected in some liver samples. There were no statistically significant differences between the individual concentrations of any of the metals and the site from which the tilapia were collected (P>0.05). Furthermore, no statistically significant correlations were found between total length of fish and metal concentration. No elements were found at concentrations of toxicological concern. However, a principal component analysis suggests that the populations of tilapia in the reservoirs may be exposed to different regimes of metals, possibly associated with different catchment land-use patterns.

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Samples of the muscle and liver of the Nile tilapia (Oreochromis niloticus) were obtained from a single reservoir in each of three Sri Lankan catchments (Kaudulla, Rajanganaya, and Udawalawe reservoirs in the Mahaweli, Kala Oya, and Walawe Ganga river basins, respectively) in 2002. The concentrations of 12 elements were consistently detected in the tilapia muscle and liver (Ca, Cd, Cu, Fe, Hg, K, Mg, Mn, Na, P, Sr and Zn). However, a three factorial principal components analysis suggested that there were no differences in the metal profiles (range of elements and concentration) of the fish obtained from any of the three reservoirs, although the chemistries of each tissue (muscle and liver) were different. Metal concentrations were below WHO and Food Standards Australia and New Zealand guideline values, and substantial quantities of tilapia would need to be consumed each week on a regular basis to exceed intake limits (e.g. more than 1.5 kg to exceed intake lits for Cu), suggesting consumption of tilapia from these reservoirs poses little risk to human health.

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Samples of the muscle of two species of tilapia (Oreochromis mossambicus and O. niloticus; 17-20 cm length) were obtained from at least one reservoir in each of the six river basins (Aruvi Aru, Kala Oya, Kirindi Oya, Ma Oya, Mahaweli, and Walawe Ganga catchments) in Sri Lanka. The metals Ca, Cu, Fe, K, Mg, Mn, Na, and Zn were consistently detected in the muscle tissue. Overall, there were few differences in the concentration of metals between the two species of fish, although there were also some statistically significant differences (p < 0.05) in the concentrations of some metals in fish obtained from some of the reservoirs. Aruvi Aru stands out as a river basin in which the two fish species have significantly lower concentration of metals when compared to other river basins. The concentration of the metals studied were below WHO and FSANZ guideline values for fish, suggesting that the consumption of the metals found in tilapia from these reservoirs poses little risk to human health.

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Fourteen microsatellite loci were used to examine genetic changes of four strains in Nile tilapia (Oreochromis niloticus) derived from genetically improved farmed tilapia (GIFT) and two strains derived from a local Chitralada strain of Nile tilapia in Thailand. Reference populations, including the ninth generation of GIFT strain, the original Chitralada strain, two conspecific reference populations from Ivory Coast and Uganda, and one population each of Oreochromis mossambicus and Oreochromis aureus, were also examined. Despite minor genetic changes, three of the four GIFT-derived populations retained their purity as GIFT while genetic variation did not decline. One of the GIFT-derived populations showed high levels of introgression from the Chitralada strain. Likewise, introgression from GIFT to the Chitralada-derived populations was seen. Inter-specific introgression from O. mossambicus was observed in the GIFT reference population and one of the Chitralada-derived strains. Introgression from O. aureus was detected in one of the GIFT-derived populations with a history of intensive inter-strain crossing. However, the introgression resulted in elevated genetic variation relative to the Chitralada original strains.

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Two experiments were conducted to investigate the efficacy of three androgens applied through immersion treatments on the sex ratio of Nile tilapia (Oreochromis niloticus L.) fry. In experiment 1, 14 days post-hatching (DPH) larvae were exposed to a single immersion treatment in 17α-methyltestosterone (MT), 17α-methyldihydrotestosterone (MDHT) or 17α-ethynyltestosterone (ET) at 200, 600 and 1800 μg L−1 over 4 h (130 larvae per treatment). In experiment 2, Nile tilapia larvae were exposed to the higher androgen concentration (1800 μg L−1) applied as either a single immersion (14 DPH) or double immersion (10 and 14 DPH) over 4 h (125 larvae per treatment). Change in sex proportion within each experiment as well as between experiments was analysed by the chi-square test. In experiment 1, MT, MDHT and ET were equally effective in significantly increasing the proportion of males when applied at 1800 μg L−1 (86.0%, 90.0% and 86.7% respectively). At 200 μg L−1 none of the androgens altered sex ratio. At 600 μg L−1, only MDHT slightly, but significantly skewed the sex ratio towards males (73.0%). In experiment 2, a single immersion treatment at 14 DPH (1800 μg L−1) significantly increased the proportion of males, but at this time the response was significantly hormone dependent (MDHT, 100.0%; MT, 91.6%; ET, 76.9%). When compared with a single immersion, two-immersion treatments significantly increased the proportion of males in the MT-treated group (from 91.6% to 98.3%), decreased the proportion of males in the MDHT group (from 100.0% to 93.4%) and had no significant effect the ET-treated group (change from 76.9% to 82.5%). The overall comparison of the sex ratio among same treatments from different experiments (a single immersion in 1800 μg L−1) was not significantly different.