旧金山河口长鳍鱼幼鱼和幼鱼的食性与鱼体大小和猎物密度的关系

IF 1 4区 生物学 Q3 FISHERIES
Zair P. Lojkovic Burris, Randall D. Baxter, Christina E. Burdi
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引用次数: 0

摘要

浮游动物猎物的密度和质量影响着幼鱼和幼鱼的摄食成功率,从而影响着它们的生长、生存和繁殖。作为调查远洋鱼类数量下降的潜在原因的一部分,我们研究了旧金山河口春季和夏季幼鱼长鳍鱼的区域摄食成功(食物存在/缺失,胃饱足),饮食组成和猎物选择作为鱼类大小和猎物可用性的函数。由于天气和河流流量对猎物群落组成和位置的影响,我们在两个湿年和两个干年进行了采样。幼鱼和幼鱼表现出食物限制的迹象:空腹比例高(≤70%),胃内容物总量<最大胃内容物体积的10%。猎物的总重量随着鱼的长度而增加,在大多数地区和年份,这是由于鱼类随着生长而消耗更大的猎物;然而,在干旱年份的许多地区,随着鱼类的生长,它们会消耗更多的猎物,而不是更大的猎物。除了轮虫或nauplii密度极高时,幼鱼优先食用Eurytemora。在大多数地区和年份,幼鱼消耗的猎物种类更多,但依赖于蛹。成鱼类桡足类(Pseudodiaptomus spp.、Eurytemora spp.和Acartia spp.)在幼鱼的饮食中具有重要的区域性,在蛹密度较低时(主要在干旱年份的东部地区)被积极选择。这种从大得多的豆科动物到小得多的鱿鱼类桡足动物的转变解释了这些地区猎物数量(而不是猎物大小)的增加。这些结果,再加上大多数地区的食物限制,表明旧金山河口目前浮游动物的密度和质量限制了长鳍鱼幼鱼的捕食成功和潜在的生长和生存。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Larval and juvenile Longfin Smelt diets as a function of fish size and prey density in the San Francisco Estuary
The density and quality of zooplankton prey affect the feeding success of larval and juvenile fishes and thus can drive growth, survival, and recruitment. As part of a larger effort investigating potential causes of a pelagic fish decline, we examined regional feeding success (food presence/absence, stomach fullness), diet composition and prey selection of young Longfin Smelt (Spirinchus thaleichthys) in spring and summer as a function of fish size and prey availability in the San Francisco Estuary. We conducted our sampling during two wet and two dry years, because weather and river flow influence prey community composition and location. Larval and juvenile fish showed evidence of food limitation: high proportions of empty stomachs (≤ 70%) and stomach contents totaling <10% of maximum stomach content volume. The total weight of prey consumed increased with fish length, and in most regions and years this resulted from fish consuming larger prey as they grew; however, in many regions during dry years, fish consumed greater numbers of prey instead of larger prey as they grew. Larval fish preferentially consumed Eurytemora spp. except when rotifers or barnacle nauplii occurred in extremely high densities. Juvenile fish consumed a greater diversity of prey yet relied on mysids in most regions and years. Adult calanoid copepods (Pseudodiaptomus spp., Eurytemora spp., and Acartia spp.) were regionally important in juvenile diets and were positively selected when mysids were in low densities, mostly in eastern regions during dry years. This switch from much larger mysids to smaller calanoid copepods explains the increase in prey number (instead of prey size) consumed in these regions. These results, coupled with food limitation in most regions, suggest that the current densities and quality of zooplankton in the San Francisco Estuary are limiting feeding success and potentially growth and survival of young Longfin Smelt.
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