Saraux Claire, Fromentin Jean-Marc, Bigot Jean-Louis, Bourdeix Jean-Hervé, Morfin Marie, Roos David, Van Beveren Elisabeth, Bez Nicolas
IFREMER (Institut Français de Recherche pour l'Exploitation de la MER), Research Unit EME (UMR 212), Sète, France.
IRD (Institut de Recherche pour le Développement), Research Unit EME (UMR 212), Sète, France.
PLoS One. 2014 Nov 6;9(11):e111211. doi: 10.1371/journal.pone.0111211. eCollection 2014.
Understanding the ecological and anthropogenic drivers of population dynamics requires detailed studies on habitat selection and spatial distribution. Although small pelagic fish aggregate in large shoals and usually exhibit important spatial structure, their dynamics in time and space remain unpredictable and challenging. In the Gulf of Lions (north-western Mediterranean), sardine and anchovy biomasses have declined over the past 5 years causing an important fishery crisis while sprat abundance rose. Applying geostatistical tools on scientific acoustic surveys conducted in the Gulf of Lions, we investigated anchovy, sardine and sprat spatial distributions and structures over 10 years. Our results show that sardines and sprats were more coastal than anchovies. The spatial structure of the three species was fairly stable over time according to variogram outputs, while year-to-year variations in kriged maps highlighted substantial changes in their location. Support for the McCall's basin hypothesis (covariation of both population density and presence area with biomass) was found only in sprats, the most variable of the three species. An innovative method to investigate species collocation at different scales revealed that globally the three species strongly overlap. Although species often co-occurred in terms of presence/absence, their biomass density differed at local scale, suggesting potential interspecific avoidance or different sensitivity to local environmental characteristics. Persistent favourable areas were finally detected, but their environmental characteristics remain to be determined.
了解种群动态的生态和人为驱动因素需要对栖息地选择和空间分布进行详细研究。尽管小型中上层鱼类会聚集形成大的鱼群，并且通常呈现出重要的空间结构，但其时空动态仍然不可预测且具有挑战性。在利翁湾（地中海西北部），过去5年里沙丁鱼和凤尾鱼的生物量下降，引发了一场严重的渔业危机，而欧洲沙丁鱼的数量却有所增加。通过对在利翁湾进行的科学声学调查应用地质统计工具，我们研究了欧洲沙丁鱼、沙丁鱼和欧洲沙丁鱼10年的空间分布和结构。我们的结果表明，沙丁鱼和欧洲沙丁鱼比凤尾鱼更靠近海岸。根据变异函数输出结果，这三种鱼类的空间结构随时间变化相当稳定，而克里格地图上的逐年变化突出了它们位置的显著变化。仅在欧洲沙丁鱼中发现了对麦考尔盆地假说（种群密度和存在区域与生物量的协变）的支持，欧洲沙丁鱼是这三种鱼类中变化最大的。一种研究不同尺度下物种搭配的创新方法表明，总体而言这三种鱼类有很强的重叠。尽管在存在/不存在方面物种经常同时出现，但它们在局部尺度上的生物量密度不同，这表明可能存在种间回避或对局部环境特征的不同敏感性。最终检测到了持续有利的区域，但其环境特征仍有待确定。
