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21.
Global change and habitat fragmentation are critical issues in our society. While considerable progress has been made in these issues worldwide, the unique features of the agroecosystems in the Great Plains have not been given enough attention. In this region, croplands occupy the majority of the landscape, forming the mosaics with linear riparian zones and shelterbelts. These three elements play different roles in the maintenance of biodiversity, and their continued effectiveness under a changing climate is critical to maintaining a healthy and productive agricultural ecosystem. This article evaluates current research and discusses future directions. The goal is to provide a scientific base for future conservation biology and wildlife management. 相似文献
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Using net enclosures in an earthen pond, we established three culture treatments with the sea cucumber Apostichopus japonicus and the Chinese white shrimp Fenneropenaeus chinensis: monoculture of sea cucumbers (C), monoculture of shrimp (S), and co-culture of the two species (CS). We measured levels of suspended particulate matter in the water column; total organic matter, total organic carbon, total nitrogen, and carbon/nitrogen ratios in both settling particles and the sediment; and chlorophyll a levels in the sediment. We then compared these variables between the three treatments. We also examined growth, survival, and yield of the two species in the different treatments. From June to September, the mean monthly suspended particulate matter sedimentation rates in the CS and S treatments were significantly (P<0.05) greater than those in the C treatment. From August to November, the mean monthly total organic matter, total organic carbon, total nitrogen, and chlorophyll a contents in the sediment in the CS and S treatments were significantly ( P <0.05) greater than those in the C treatment. Final wet weight, specific growth rate, survival rate, and total yield of sea cucumbers in co-culture were all significantly greater than those of sea cucumbers in monoculture. There were no significant differences among any of these variables for shrimp reared in the two systems. The bioturbation of the sediment and fecal production of the shrimp likely supplied natural food for the sea cucumbers. Co-culture of the two species is a viable option for increasing yield per unit area, maximizing use of the water body, and diversifying crop production. 相似文献
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The exceptionally large individual growth variation has been previously recognized in several sea cucumber cohorts. However, there is a lack of information regarding the mechanism of such individual differences. In this study, the sea cucumber Apostichopus japonicus(Selenka)was reared individually in order to eliminate possible effects of social interaction, stocking density, etc. The results showed that there were substantial differences in growth among the sea cucumber individuals during the 100-day experiment. The special growth rate of the sea cucumber individuals differed by up to three folds(from 0. 40% to 1.01%), and the coefficient of variation in body weight increased from 12. 04% to 40. 51%. The final wet body weight, food intake and food conversion efficiency for each sea cucumber were generally positively correlated with their initial wet body weight(P<0. 05). Energy budget of the animals showed that the food energy spent on respiration was much greater(about four folds)but energy deposited for growth was much less for(initially)smaller than for larger A. Japonicus. The present result implies that there are obvious genetic differences among the sea cucumber individuals, largely accounting for the individual growth variation of the cohort sea cucumber. These results will provide some basic data for promoting selective breeding and farming of the sea cucumber. 相似文献
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以过硫酸氢钾、沸石粉和膨润土为主要成分,分别添加0%(对照)、0.5%、1%、2%、4%和8%的过碳酰胺配成6种底质改良剂,分别标记为A、B、C、D、E和F,本实验研究了以上6种不同组分的底质改良剂对刺参生长和底质环境的影响。实验过程中,分别于第0、7、14、28、42和56天测定底泥氧化还原电位和营养盐变化,实验结束后测定刺参特定生长率。结果表明:E组底泥氧化还原电位最高,但与F组间无显著差异(P>0.05);底泥中NO_3--N含量同样在E组达到最大值,且与F组间差异不显著(P>0.05);底泥NH4+-N、NO_2--N、和TN含量均在D组达到最小值,但与E组和F组间无显著差异(P>0.05);D组刺参特定生长率最高,但与E组和F组间无显著差异(P>0.05)。综上所述,底质改良剂中添加过碳酰胺能够显著改善底质环境,以特定生长率为评价指标,当添加量为4.8%时最利于刺参的生长。 相似文献
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Monoculture of sea cucumber (pond S) and polyculture of shrimp with sea cucumber (pond SS) were established to evaluate the effect of shrimp on the environmental conditions of sea cucumber farming pond. Contributions of sediment organic matter (SOM2) resuspended from benthic sediment and the suspended particulate organic matter (SPOM) deposited from the water column to the precipitated organic matter (SOM1) collected with sediment traps were estimated with carbon stable isotope analysis. The results showed that the levels of SPOM and SOM2 in pond SS significantly decreased in comparison with those in pond S at the end of experiment (P < 0.05), indicating that co-culturing shrimp in sea cucumber farming pond could purify the farming water. Carbon stable isotope analysis showed that the proportion of SOM2 in SOM1 in pond SS (84.97% ± 0.38%) was significantly lower than that in pond S (95.20% ± 0.30%) (P < 0.05), suggesting that the resuspension of organic matter from benthic sediment into overlying water was reduced in polyculture pond. In contrast, the proportion of SPOM in SOM1 in pond SS (15.03% ± 0.38%) was significantly higher than that in pond S (4.80% ± 0.30%) (P < 0.05), indicating that the sedimentation of SPOM from water column was enhanced in pond SS owing to the biodeposition effect of shrimp. 相似文献
28.
Estivation, hibernation, and starvation are indispensable inactive states of sea cucumbers Apostichopus japonicus in nature and in culture ponds. Generally, temperature is the principal factor that induces estivation or hibernation in
the sea cucumber. The present study provided insight into the physiological adaptations of A. japonicus during the three types of inactivity (hibernation, estivation, and starvation) by measuring the oxygen consumption rates
(Vo2) and biochemical compositions under laboratory conditions of low (3°C), normal (17°C) and high (24°C) temperature. The results
show that the characteristics of A. japonicus in dormancy (hibernation and estivation) states were quite different from higher animals, such as fishes, amphibians, reptiles,
and mammals, but more closely resembled a semi-dormant state. It was observed that the shift in the A. japonicus physiological state from normal to dormancy was a chronic rather than acute process, indicated by the gradual depression
of metabolic rate. While metabolic rates declined 44.9% for the estivation group and 71.7% for the hibernation group, relative
to initial rates, during the 36 d culture period, metabolic rates were not maintained at constant levels during these states.
The metabolic depression processes for sea cucumbers in hibernation and estivation appeared to be a passive and an active
metabolic suppression, respectively. In contrast, the metabolic rates (128.90±11.70 μg/g h) of estivating sea cucumbers were
notably higher (107.85±6.31 μg/g h) than in starving sea cucumbers at 17°C, which indicated that the dormancy mechanism here,
as a physiological inhibition, was not as efficient as in higher animals. Finally, the principle metabolic substrate or energy
source of sea cucumbers in hibernation was lipid, whereas in estivation they mainly consumed protein in the early times and
both protein and lipid thereafter. 相似文献
29.
为探究大西洋鲑(Salmo salar)幼鱼的适宜投喂频率和胃排空规律,进行了养殖实验和胃排空实验.养殖实验设置了1次/天(F1组)、2次/天(F2组)、3次/天(F3组)、4次/天(F4组)和连续投喂(C F组)共5种投喂频率.胃排空实验采用连续测定胃含物的方法,用数学模型对胃含物数据进行拟合.研究表明:F1组日摄食... 相似文献
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Chuanxin Qin Shuanglin Dong Fuyi Tan Xiangli Tian Fang Wang Yunwei Dong Qinfeng Gao 《中国海洋大学学报(英文版)》2009,8(3):296-302
Optimal stocking densities were investigated for the sea cucumber Apostichopus japonicus Selenka under feed-supplement and non-feed-supplement regimes in net enclosures for 333 d. Substantial weight loss occurred
during the aestivation phase (AE). Decreased growth rates were also observed during the winter phase (WT). In contrast, sea
cucumbers showed rapid growth during the spring (SP) and autumn (AU) phases. Feeding regimes considerably influenced the growth
performance, i.e., sea cucumbers grew faster under feed-supplement regime than under non-feed-supplement regime (P < 0.05). The average survival rates of sea cucumbers under feed-supplement regime were higher than those under non-feed-supplement
regime for both the autumn phase and spring phase, but the differences were only significant for the latter phase (P < 0.05). The fitted B-N curves showed that the optimal stocking densities, in terms of net production, were 22.3 ind. m-2
for feed-supplement regime and 14.1 ind. m-2 for non-feed-supplement regime. 相似文献