Differences in diet, population size and reproductive performance between two colonies of Audouin's gull Larus audouinii affected by a trawling moratorium
Differences in diet, population size and reproductive performance between two colonies of Audouin's gull Larus audouinii affected by a trawling moratorium
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DOI：
10.2307/3677229
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发表时间：
1996-09-01
影响因子：
1.7
通讯作者：
GarciaGans, J
中科院分区：
文献类型：
--
作者：
Oro, D;Genovart, X;GarciaGans, J
自1991年以来，西班牙东北部的塔拉戈纳省和卡斯泰洛省实施了拖网捕捞禁令，这两个省相距80公里，分别位于埃布罗三角洲（在大陆上）和科伦布雷特斯群岛。(60离海岸10公里）。而科伦布莱特家族则是。殖民地成立于1973年，只增长了一点点（约。埃布罗三角洲殖民地成立于1981年，今天拥有世界总人口的70%（约600对，1995年）。1995年10300对）。拖网捕捞暂停与该物种的繁殖季节相吻合，尽管每年受影响的特定繁殖阶段不同。由于暂停捕捞造成拖网丢弃物的缺乏以及鲱形目鱼类种群可能减少，影响了该物种的摄食和繁殖生物学。然而，食物供应减少的影响在科伦布雷特斯群岛更大，可能是因为缺乏替代食物资源。当拖网渔船作业时，海鸥的饮食在两个殖民地非常相似，但当暂停开始时，在分类学和类型学水平上都发现了显着差异。稻田里的猎物充当了埃布罗三角洲殖民地的缓冲区，而在科伦布雷特斯是。海鸥被迫积极捕鱼，可能要付出更大的能量代价。在暂停的几年里，繁殖成功率总是显着较低的科伦布雷特斯是。比在埃布罗三角洲的要多;更极端的是，在科伦布雷特斯没有羽翼丰满的年轻人。1993年离合器的大小也显着降低在哥伦布是。殖民地，即使当暂停不符合奠定阶段，这表明捕食黄腿鸥车道cachinnans可能是一个额外的限制因素，在这个地方，繁殖对黄腿奥杜因的海鸥的比例比埃布罗三角洲高得多。与以前的研究相反，较大的殖民地（埃布罗三角洲）比较小的殖民地（科伦布雷特斯群岛）有更好的繁殖性能，这表明，密度依赖效应可能不会在埃布罗三角洲殖民地运作，因为觅食栖息地（稻田，泻湖，沙丘，海滩）和高生产力的海洋关闭这个殖民地。虽然人口规模在埃布罗三角洲殖民地建议没有限制因素，直到建立拖网捕捞暂停，规模的科伦布雷。群体表明繁殖地点的限制，并可能与黄腿鸥的竞争。
Since 1991, a trawling moratorium has been enforced in the provinces of Tarragona and Castello, NE Spain, where two Audouin's Gull Larus audouinii colonies are located 80 km apart: the Ebro Delta (on the mainland) and the Columbretes Is. (60 km off the coast). While the Columbretes Is. colony was established in 1973 and has grown only slightly (ca. 600 pairs in 1995), the Ebro Delta colony was established in 1981 and today holds 70% of total world population (ca. 10300 pairs in 1995). The trawling moratorium has coincided with the breeding season of the species, though the particular breeding stage affected was different each year. The lack of trawl discards caused by the moratorium and the likely decrease of clupeiform populations have affected both the feeding and breeding biology of the species. However, the effects of a reduced food supply were greater in the Columbretes Is., probably because of the lack of alternative food resources. When trawlers operated, the gulls' diet was very similar in the two colonies, but when the moratorium started, significant differences were found at both taxonomic and typologic levels. Prey from rice fields acted as a buffer for the Ebro Delta colony, whereas in the Columbretes Is. the gulls were forced to fish actively, probably at greater energy costs. In the moratorium years, breeding success was always significantly lower in the Columbretes Is. than in the Ebro Delta; extremely, no young fledged in the Columbretes Is. in 1993. Clutch size was also significantly lower in the Columbretes Is. colony, even when the moratorium did not coincide with the laying stage, suggesting that predation by Yellow-legged Gull Lanes cachinnans could be an additional limiting factor at this locality, where the ratio of breeding pairs of Yellow-legged to Audouin's Gulls is much higher than in the Ebro Delta. In contrast to previous studies, the larger colony (Ebro Delta) had better breeding performance than the smaller colony (Columbretes Is.), suggesting that density-dependent effects may not operate in the Ebro Delta colony because of the large variety of foraging habitats (rice fields, lagoons, dunes, beaches) and the high productivity of the sea off this colony. While population size in the Ebro Delta colony suggested the absence of limiting factors until the establishment of the trawling moratorium, the size of the Columbretes Is. colony indicated a breeding site limitation, and probably competition with the Yellow-legged Gull.