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We investigated the effect of raising runt white sturgeon (Acipenser transmontanus) separately from dominant fish during the initial stages of grow-out in a commercial farm. Runt fish are poor-growers, have underdeveloped muscle mass, swim slowly and are more-frequently found at the top of the water column. The objective of the study was to describe the mortality and recovery rates (and their determinants) of white-sturgeon runts after separating them from dominant fish. Runt white sturgeon were stocked into twelve 2 m × 2 m rectangular tanks and graded periodically during a follow-up of 46–102 days. Overall mortality rates ranged from 0.3 to 7 dead fish per 1000 sturgeon-days at risk and overall recovery rates from 3.9 to 13.5 recovered fish per 1000 sturgeon-days at risk. Period-specific mortality and recovery rates increased over time. The period-specific mortality rates for all three periods were significantly higher for tanks of runts originating from grow-out tanks with high mortality (p-values: first period = 0.06; second period = 0.09; third period = 0.03), but were similar for tanks of runts of high- and low-mean initial weight. The period-specific recovery rates were significantly higher in runts originating from high-mortality grow-out tanks only for the third period (p = 0.05) but not the first and second periods (p-values = 0.33 and 0.25, respectively). Recovery rates were significantly higher in the higher-mean-weight runts tanks for the first and third period but not for the second (p-values: first period = 0.02; second period = 0.65; third period = 0.06). We concluded that the proportion of runts that recover during a 46–89 day period is substantial (16–58%); therefore, it might be worthwhile growing such fish separately in a fish farm for about three months. Financial analysis showed that this practice was profitable, if the value of white sturgeon fish for the farm exceeded $2.05 per kg. 相似文献
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M. P. Georgiadis R. P. Hedrick W. O. Johnson I. A. Gardner 《Preventive veterinary medicine》2000,43(4)
We investigated the effect of raising runt white sturgeon (Acipenser transmontanus) separately from dominant fish during the initial stages of grow-out in a commercial farm. Runt fish are poor-growers, have underdeveloped muscle mass, swim slowly and are more-frequently found at the top of the water column. The objective of the study was to describe the mortality and recovery rates (and their determinants) of white-sturgeon runts after separating them from dominant fish. Runt white sturgeon were stocked into twelve 2 m × 2 m rectangular tanks and graded periodically during a follow-up of 46–102 days. Overall mortality rates ranged from 0.3 to 7 dead fish per 1000 sturgeon-days at risk and overall recovery rates from 3.9 to 13.5 recovered fish per 1000 sturgeon-days at risk. Period-specific mortality and recovery rates increased over time. The period-specific mortality rates for all three periods were significantly higher for tanks of runts originating from grow-out tanks with high mortality (p-values: first period = 0.06; second period = 0.09; third period = 0.03), but were similar for tanks of runts of high- and low-mean initial weight. The period-specific recovery rates were significantly higher in runts originating from high-mortality grow-out tanks only for the third period (p = 0.05) but not the first and second periods (p-values = 0.33 and 0.25, respectively). Recovery rates were significantly higher in the higher-mean-weight runts tanks for the first and third period but not for the second (p-values: first period = 0.02; second period = 0.65; third period = 0.06). We concluded that the proportion of runts that recover during a 46–89 day period is substantial (16–58%); therefore, it might be worthwhile growing such fish separately in a fish farm for about three months. Financial analysis showed that this practice was profitable, if the value of white sturgeon fish for the farm exceeded $2.05 per kg. 相似文献
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Runt white sturgeon (Acipenser transmontanus) develop during grow-out and are characterized by atrophied muscles and decreased growth. Our first objective was to compare the growth (and body condition) of previously-runt white sturgeon after they recovered from the runt state and sturgeon that had never been runts. On 12 occasions, recovered runts and age- and size-matched controls that had never been runts were tagged and put in a tank that already contained fish of similar age and size. Tagged groups were followed for 119–134 days. Median relative growth rates (RGRs) of the recovered runts were significantly (p ≤ 0.05) higher than those of the controls in three tanks. Multiple linear regression was used to model final weight as a function of initial weight and status (recovered runt or control). Status was not significantly related (p = 0.71) to final weight, after adjusting for initial weight, “tank” and time of follow-up. Our second objective was to determine factors that influenced the loss of tags by white sturgeon during the follow-up period. Logistic regression analysis indicated that higher initial weight and being a control fish might have been associated with losing both tags. We concluded that once white sturgeon runts recovered and started growing, they grew at least as well as fish that had never been runts. 相似文献
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[目的]研究普通丝瓜生长过程中出现的一些异常现象及其原因。[方法]对112个普通丝瓜品种进行调查,研究弱苗、僵苗和瓜过顶的发生比例及其原因。[结果]112个品种内有13个品种出现弱苗现象,占总品种11.6%。弱苗植株长势弱、植株矮小,但无僵苗和瓜过顶现象。43个品种出现僵苗现象,占总品种38.4%,僵苗率100%的有8个品种。22个品种出现瓜过顶现象,占总品种19.6%。瓜过顶植株都是僵苗。干旱和频繁喷药是造成僵苗发生的主因。[结论]在生产过程中采用催芽育苗可减少弱苗。为减少僵苗和瓜过顶现象,应采取以下措施:提高地温;精细定植、中耕;施充分腐熟粪肥,均匀追肥;适时适度灌溉。 相似文献
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