Three groups (wild-WS, semi-pond-SPS, and pond-cultured-PS) of ide Leuciscus idus (L.) were examined. Each group consisted of 30 females and 10 males, aged 5-8 years. All groups were stimulated with two agents: carp pituitary homogenate (CPH) and a synthetic hormonal preparation Ovopel. The amount of ovulating females decreased in conjunction with females' domestication level, mainly because of very low efficacy of CPH for pond-reared ide stimulation. The percentage of ovulating females stimulated with Ovopel (97.0 %) was significantly higher comparing to CPH (63.0 %). No significant differences were found in latency time between the groups but spawning synchronization increased in conjunction with ide domestication. The positive correlation between domestication level and latency time, i.e., the higher the domestication level, the higher the latency time, was stated. No significant differences were found in PGSI as well as in total volume of obtained eggs, but groups differed significantly in the number of dry eggs and in number of swollen egg. Significant negative correlation between domestication level and number of swollen eggs, i.e., the higher the domestication level, the lower the number of eggs, was detected. The survival rate at the eyed stage was the highest in WS group (60.4 %) and PS group (57.7 %), and was significantly higher than in SPS group (51.8 %). Eggs obtained after CPH stimulation had higher survival rate at the eyed-egg stage
Stocking hatchery-reared brown trout in different densities into a wild population -a comparison of growth and movementIn spring 2001 and 2002 a small stream was stocked with tagged hatchery-reared yearling brown trout (Salmo trutta), in order to study their influence on the resident brown trout population. The stream was separated into six sections: two sections without stocking, two sections where stocking doubled the trout population and two sections where the fish population was quadrupled. The working hypothesis was that due to food limitation (competition) growth of the wild fish will be negatively influenced by stocking, and wild fish will be displaced by the (possibly more aggressive) hatchery fish. Surprisingly, growth rate of wild and stocked fish of the same age was similar and independent of stocking density. Two main reasons may be responsible for this finding: only a low percentage of the stocked fish remained in the stream, and food was not limited during summer. Only 12-19% of the stocked fish were recaptured after six months, in contrats to 40-70% of one-year old and up to 100% of older wild trout. The wild fish were not displaced by hatchery-reared fish: During summer the wild fish remained more or less stationary, whereas most of the stocked trout had left their release site. The results indicate that in a natural stream stocking of hatchery reared brown trout does not influence negatively growth and movement of the wild fish independent of stocking density. Baer, J. (Fisheries Research Station of Baden-Wu¨rttemberg, Untere Seestraße 81, 88085 Langenargen, Germany). Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density Genetic quality of domesticated African tilapia populations Anecdotal and empirical evidence exists for substantial (up to 40%) declines in growth among Oreochromis populations domesticated in both large and small-scale fish farms in Africa. These declines are at least partly attributable to poor genetic management, including inadvertent selection, inbreeding, bottle-necks and founder effects. Due to restricted cash flow and investment capital, genetic management and selective breeding for the improvement of domesticate populations are difficult for small-scale farmers, but feasible on larger-scale farms. In managing domesticated gene pools, feral populations can serve as a broodstock reservoir, making the use of indigenous species advantageous. A development model of large-scale hatcheries producing selected lines of sex-reversed, indigenous tilapia for sale to smaller-scale farmers is proposed as a solution to the problems of poor genetic management in African aquaculture. Brummett, R. E. & Ponzoni, R. (WorldFish Centre, BP 2008, Yaounde´, Cameroon). Polyculture production of juvenile fishes for survival in natureProduction of seed for stock enhancement projects requires consideration of the behavioural quality of the animals to be released in the wild. Our approach to improving behavioural quality of hat...
Stocking hatchery-reared brown trout in different densities into a wild population -a comparison of growth and movementIn spring 2001 and 2002 a small stream was stocked with tagged hatchery-reared yearling brown trout (Salmo trutta), in order to study their influence on the resident brown trout population. The stream was separated into six sections: two sections without stocking, two sections where stocking doubled the trout population and two sections where the fish population was quadrupled. The working hypothesis was that due to food limitation (competition) growth of the wild fish will be negatively influenced by stocking, and wild fish will be displaced by the (possibly more aggressive) hatchery fish. Surprisingly, growth rate of wild and stocked fish of the same age was similar and independent of stocking density. Two main reasons may be responsible for this finding: only a low percentage of the stocked fish remained in the stream, and food was not limited during summer. Only 12-19% of the stocked fish were recaptured after six months, in contrats to 40-70% of one-year old and up to 100% of older wild trout. The wild fish were not displaced by hatchery-reared fish: During summer the wild fish remained more or less stationary, whereas most of the stocked trout had left their release site. The results indicate that in a natural stream stocking of hatchery reared brown trout does not influence negatively growth and movement of the wild fish independent of stocking density. Baer, J. (Fisheries Research Station of Baden-Wu¨rttemberg, Untere Seestraße 81, 88085 Langenargen, Germany). Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density Genetic quality of domesticated African tilapia populations Anecdotal and empirical evidence exists for substantial (up to 40%) declines in growth among Oreochromis populations domesticated in both large and small-scale fish farms in Africa. These declines are at least partly attributable to poor genetic management, including inadvertent selection, inbreeding, bottle-necks and founder effects. Due to restricted cash flow and investment capital, genetic management and selective breeding for the improvement of domesticate populations are difficult for small-scale farmers, but feasible on larger-scale farms. In managing domesticated gene pools, feral populations can serve as a broodstock reservoir, making the use of indigenous species advantageous. A development model of large-scale hatcheries producing selected lines of sex-reversed, indigenous tilapia for sale to smaller-scale farmers is proposed as a solution to the problems of poor genetic management in African aquaculture. Brummett, R. E. & Ponzoni, R. (WorldFish Centre, BP 2008, Yaounde´, Cameroon). Polyculture production of juvenile fishes for survival in natureProduction of seed for stock enhancement projects requires consideration of the behavioural quality of the animals to be released in the wild. Our approach to improving behavioural quality of hat...
Stocking hatchery-reared brown trout in different densities into a wild population -a comparison of growth and movementIn spring 2001 and 2002 a small stream was stocked with tagged hatchery-reared yearling brown trout (Salmo trutta), in order to study their influence on the resident brown trout population. The stream was separated into six sections: two sections without stocking, two sections where stocking doubled the trout population and two sections where the fish population was quadrupled. The working hypothesis was that due to food limitation (competition) growth of the wild fish will be negatively influenced by stocking, and wild fish will be displaced by the (possibly more aggressive) hatchery fish. Surprisingly, growth rate of wild and stocked fish of the same age was similar and independent of stocking density. Two main reasons may be responsible for this finding: only a low percentage of the stocked fish remained in the stream, and food was not limited during summer. Only 12-19% of the stocked fish were recaptured after six months, in contrats to 40-70% of one-year old and up to 100% of older wild trout. The wild fish were not displaced by hatchery-reared fish: During summer the wild fish remained more or less stationary, whereas most of the stocked trout had left their release site. The results indicate that in a natural stream stocking of hatchery reared brown trout does not influence negatively growth and movement of the wild fish independent of stocking density. Baer, J. (Fisheries Research Station of Baden-Wu¨rttemberg, Untere Seestraße 81, 88085 Langenargen, Germany). Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density Genetic quality of domesticated African tilapia populations Anecdotal and empirical evidence exists for substantial (up to 40%) declines in growth among Oreochromis populations domesticated in both large and small-scale fish farms in Africa. These declines are at least partly attributable to poor genetic management, including inadvertent selection, inbreeding, bottle-necks and founder effects. Due to restricted cash flow and investment capital, genetic management and selective breeding for the improvement of domesticate populations are difficult for small-scale farmers, but feasible on larger-scale farms. In managing domesticated gene pools, feral populations can serve as a broodstock reservoir, making the use of indigenous species advantageous. A development model of large-scale hatcheries producing selected lines of sex-reversed, indigenous tilapia for sale to smaller-scale farmers is proposed as a solution to the problems of poor genetic management in African aquaculture. Brummett, R. E. & Ponzoni, R. (WorldFish Centre, BP 2008, Yaounde´, Cameroon). Polyculture production of juvenile fishes for survival in natureProduction of seed for stock enhancement projects requires consideration of the behavioural quality of the animals to be released in the wild. Our approach to improving behavioural quality of hat...
Stocking hatchery-reared brown trout in different densities into a wild population -a comparison of growth and movementIn spring 2001 and 2002 a small stream was stocked with tagged hatchery-reared yearling brown trout (Salmo trutta), in order to study their influence on the resident brown trout population. The stream was separated into six sections: two sections without stocking, two sections where stocking doubled the trout population and two sections where the fish population was quadrupled. The working hypothesis was that due to food limitation (competition) growth of the wild fish will be negatively influenced by stocking, and wild fish will be displaced by the (possibly more aggressive) hatchery fish. Surprisingly, growth rate of wild and stocked fish of the same age was similar and independent of stocking density. Two main reasons may be responsible for this finding: only a low percentage of the stocked fish remained in the stream, and food was not limited during summer. Only 12-19% of the stocked fish were recaptured after six months, in contrats to 40-70% of one-year old and up to 100% of older wild trout. The wild fish were not displaced by hatchery-reared fish: During summer the wild fish remained more or less stationary, whereas most of the stocked trout had left their release site. The results indicate that in a natural stream stocking of hatchery reared brown trout does not influence negatively growth and movement of the wild fish independent of stocking density. Baer, J. (Fisheries Research Station of Baden-Wu¨rttemberg, Untere Seestraße 81, 88085 Langenargen, Germany). Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density Genetic quality of domesticated African tilapia populations Anecdotal and empirical evidence exists for substantial (up to 40%) declines in growth among Oreochromis populations domesticated in both large and small-scale fish farms in Africa. These declines are at least partly attributable to poor genetic management, including inadvertent selection, inbreeding, bottle-necks and founder effects. Due to restricted cash flow and investment capital, genetic management and selective breeding for the improvement of domesticate populations are difficult for small-scale farmers, but feasible on larger-scale farms. In managing domesticated gene pools, feral populations can serve as a broodstock reservoir, making the use of indigenous species advantageous. A development model of large-scale hatcheries producing selected lines of sex-reversed, indigenous tilapia for sale to smaller-scale farmers is proposed as a solution to the problems of poor genetic management in African aquaculture. Brummett, R. E. & Ponzoni, R. (WorldFish Centre, BP 2008, Yaounde´, Cameroon). Polyculture production of juvenile fishes for survival in natureProduction of seed for stock enhancement projects requires consideration of the behavioural quality of the animals to be released in the wild. Our approach to improving behavioural quality of hat...
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