| 长江汇流区投放鱼苗对江豚觅食行为的影响 |
| Impact of Releasing Fish Fry into the Wanhe River Estuary on the Foraging Behavior of Yangtze Finless Porpoise |
| 投稿时间：2015-02-11 修订日期：2016-03-07 |
| DOI：10.15928/j.1674-3075.2015.06.010 |
| 中文关键词:长江江豚 增殖放流 觅食行为 汇流区 |
| 英文关键词:Neophocaena asiaeorientalis asiaeorientalis stock enhancement foraging behavior confluence area |
| 基金项目:香港海洋公园(AW05-1314)项目；长江航道局专题评价项目 |
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| 中文摘要: |
| 2013年9月15日至2014年2月22日，在自然状态下观察江豚在皖河口活动作为对照组。2014年3月2、11、17、20日购买2龄鲢（Hypophthalmichthys molitrix）等冬片鱼种692 kg，在投食状态下观察江豚在皖河口活动作为试验组。每次在白天整点时刻，采用瞬间扫描法记录10 min内江豚的出水次数和出水位置，作为1个样本。皖河汇流区设置304个网格（50 m×50 m），每头江豚出水1次，在相应网格位置以黑点标注。皖河入口端线中点为圆心，以半径500 m半圆面积为有效观察窗，根据江豚平均游动速度（4.3 km/h），窗内群体之间的时间间隔超过7 min，视为2个独立的群体。结果表明，自然状态下，江豚在皖河口觅食活动主要在支流区和滞留区，9：00、12：00和14：00出现3个活动高峰期；集群规模在1～8头，平均为3.67头。投放活体幼鱼后，江豚在分离区和急流区平均出水次数增多，而滞留区减少；出水次数骤然升高，以后逐渐降低；集群规模在2～10头，均值为5.80头，可见投放鱼饵后江豚集群规模明显增大(P<0.05)。在皖河18次调查的144个样本中，有效观察时间为1400 min，共记录江豚活动87次，累计记录309头（含重复数），分为156个亚群类型，以夫妻型居多（37.10%），家庭型最少（14.67%）。自然状态下，每天观察到江豚约15头，投放鱼苗时观察到约24头，两者差异不明显（P>0.05），但出水平均次数明显增多（P<0.05）。所以在其经常出没的汇流水域投放鱼苗可以减缓施工对江豚捕食的负面影响。 |
| 英文摘要: |
| Habitat for the Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is primarily limited by availability of food resources. Abundant literature sources reveal that the species usually forages for food in the shallows; the sandbars of tortuous channels and at the confluence of tributaries. These locations are also where engineers commonly locate flow control structures and the foraging behavior of YFP is impacted by the noise of water flowing through these structures. In this study, we documented the spatial-temporal distribution of the YFP population at the confluence of the Wanhe and Yangtze Rivers under natural conditions and then with food resource enhancement accomplished by the release of fish fry. The study examined the feasibility of temporary food enhancement for YFP in confluence areas and to confirm the importance and necessity of conserving the species during periods of water flow regulation. From September 2013 to February 2014, the behavior of the YFP population under natural condition was monitored within the Wanhe River estuary. On March 2, 11, 17 and 20 of 2014, 692 kg of winter-breeding species, including two-year-old silver carp (Hypophthalmichthys molitrix), bighead carp, grass carp and white bream (Parabramis pekinensis), were released into the estuary and the behavior of the YFP population was recorded. During daylight hours, instantaneous scans were used to record the number and location of the YFP for 10 minutes each hour, beginning on the hour and each 10-minute record was treated as one sample. The confluence area of the Wanhe River estuary was divided into a grid of 304 cells (50m×50m) and the effective observation window was a semicircle with a radius of 500 m using the midpoint of the entrance line as the center of the circle. When a porpoise surfaced, a black dot was placed in the corresponding cell of the grid map. According to the average swimming speed (4.3 km/h), two independent groups were recorded when the time interval between observations exceeded 7 minutes. Results show that the foraging activity of YFP was concentrated primarily in the tributary and stagnant zones under the natural conditions. Foraging activity peaked at 9:00, 12:00 and 14:00. The group size ranged from 1-8 individuals with an average of 3.67 individuals. After releasing fish fry, the surfacing frequency of the YFP increased in the riffle and separation zones and decreased in the stagnant zone. The surfacing frequency increased rapidly then gradually decreased and the group size was 2-10 individuals with an average of 5.80 individuals. The group size of the YFP increased significantly after releasing fry (P<0.05). Of the 144 samples collected in eighteen surveys, 87 YFP activity events were recorded in the effective observation time of 1440 minutes. A total of 309 individuals (including repetitions) were recorded as 156 subgroups, in which a female-male pair was the most frequently observed group (37.1%) and family groups were the least frequently observed (14.67%). Under natural conditions, ~15 individuals were observed each day, while ~24 individuals were observed each day after fry release (difference not significant, P>0.05). However, the average surfacing frequency after fry release was significantly higher than under natural conditions (P<0.05). Therefore, releasing fish fry into confluence areas where YFP feed reduces the negative effects of water flow control structures on foraging behavior. |
| 游立新,何虎,张晓可,于道平.2015.长江汇流区投放鱼苗对江豚觅食行为的影响[J].水生态学杂志,36(6):66-71. |
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