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首页> 外文期刊>San Francisco Estuary and Watershed Science >Diet, Prey Selection, and Body Condition of Age-0 Delta Smelt, , in the Upper San Francisco Estuary
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Diet, Prey Selection, and Body Condition of Age-0 Delta Smelt, , in the Upper San Francisco Estuary

机译：旧金山河口上游地区0岁年龄段Delta Smelt的饮食，猎物选择和身体状况

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Steven B. Slater and Randall D. Baxter doi: http://dx.doi.org/10.15447/sfews.2014v12iss3art1 The Delta Smelt, an endangered fish, has suffered a long-term decline in abundance, believed to result from, in part, to changes in the pelagic food web of the upper San Francisco Estuary. To investigate the current role of food as a factor in Delta Smelt well-being, we developed reference criteria for gut fullness and body condition based on allometric growth. We then examined monthly diet, prey selectivity, and gut fullness of larvae and juvenile Delta Smelt collected April through September in 2005 and 2006 for evidence of feeding difficulties leading to reduced body condition. Calanoid copepods Eurytemora affinis and Pseudodiaptomus forbesi remained major food items during spring and from early summer through fall, respectively. Other much larger copepods and macroinvertebrates contributed in lesser numbers to the diet of older juvenile fish from mid-summer through fall. In fall, juvenile Delta Smelt periodically relied heavily on very small prey and prey potentially associated with demersal habitat, suggesting typical pelagic food items were in short supply. We found a strong positive selection for E. affinis and P. forbesi, neutral to negative selection for evasive calanoid Sinocalanus doerrii, and neutral to negative selection for the small cyclopoid copepod Limnoithona tetraspina and copepod nauplii, which were consumed only when extremely numerous in the environment. Feeding incidence was significantly higher in 2006, but among successfully feeding fish we found no between year difference in gut fullness. However, we did detect differences in fullness across months in both years. We found no difference in body condition of Delta Smelt between years yet our sample sizes were low in September when Delta Smelt reverted to feeding on very small organisms and fullness declined, so the longer-term effect remains unknown. Our findings suggest that: Delta Smelt had difficulty obtaining prey in spring 2005 or obtaining proper-sized prey in fall of both years. We detected these difficulties in some regional feeding incidence and fullness indices, but not in body condition indices.
机译：史蒂文·B·斯莱特（Steven B.Slater）和兰德尔·D·巴克斯特（Randall D.Baxter doi）：http://dx.doi.org/10.15447/sfews.2014v12iss3art1濒临灭绝的鱼类三角洲冶炼厂的长期丰度下降，据信是由于部分是旧金山河口上游中上层食物网的变化。为了调查当前食物对Delta Smelt健康状况的影响，我们基于异速生长法开发了肠饱满度和身体状况的参考标准。然后，我们检查了从2005年和2006年4月至9月收集的幼虫和幼鱼Delta Smelt的每月饮食，猎物的选择性以及肠的饱满度，以寻找导致身体状况降低的喂养困难的证据。春季和夏季初至秋季，Calanoid pe足类Eurytemora affinis和Pseudodiaptomus forbesi仍是主要食物。从仲夏到秋天，其他大得多的co足类和大型无脊椎动物对年幼幼鱼的饮食贡献较少。在秋天，幼稚的三角洲熔炼定期依赖于非常小的猎物和可能与海底栖息地有关的猎物，这表明典型的远洋食物短缺。我们发现了对链球菌和福氏疟原虫的强正选择，对规避类花环拟南芥的中性至负选择，对小摆线类co足类Limnoithona tetraspina和co足无节幼体的中性至负选择，仅当它们在极大量时才被消耗。环境。 2006年的摄食率显着更高，但是在成功摄食鱼类的过程中，我们没有发现肠道饱满度的年际差异。但是，我们确实发现了这两个月中各个月的饱满度差异。我们发现几年之间Delta Smelt的身体状况没有差异，但是我们的样本量在9月份很低，当时Delta Smelt恢复以很小的生物体为食，并且饱腹感下降了，因此长期影响仍然未知。我们的发现表明：Delta Smelt很难在2005年春季获得猎物，或者在两年的秋季都无法获得适当大小的猎物。我们在某些区域的进食率和饱满度指数中发现了这些困难，但在身体状况指数中却没有发现。

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