Alegre Ana, Ménard Frédéric, Tafur Ricardo, Espinoza Pepe, Argüelles Juan, Maehara Víctor, Flores Oswaldo, Simier Monique, Bertrand Arnaud
Instituto del Mar del Perú (IMARPE), Callao, Peru ; Institut de Recherche pour le Développement (IRD), UMR212 EME IFREMER/IRD/UM2, Sète, France.
Institut de Recherche pour le Développement (IRD), UMR212 EME IFREMER/IRD/UM2, Sète, France.
PLoS One. 2014 Jan 20;9(1):e85919. doi: 10.1371/journal.pone.0085919. eCollection 2014.
The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and prey. We investigated the ontogenetic and spatiotemporal variability of the diet composition of jumbo squid in the northern Humboldt Current system. For that purpose we applied several statistical methods to an extensive dataset of 3,618 jumbo squid non empty stomachs collected off Peru from 2004 to 2011. A total of 55 prey taxa was identified that we aggregated into eleven groups. Our results evidenced a large variability in prey composition as already observed in other systems. However, our data do not support the hypothesis that jumbo squids select the most abundant or energetic taxon in a prey assemblage, neglecting the other available prey. Indeed, multinomial model predictions showed that stomach fullness increased with the number of prey taxa, while most stomachs with low contents contained one or two prey taxa only. Our results therefore question the common hypothesis that predators seek locally dense aggregations of monospecific prey. In addition D. gigas consumes very few anchovy Engraulis ringens in Peru, whereas a tremendous biomass of anchovy is potentially available. It seems that D. gigas cannot reach the oxygen unsaturated waters very close to the coast, where the bulk of anchovy occurs. Indeed, even if jumbo squid can forage in hypoxic deep waters during the day, surface normoxic waters are then required to recover its maintenance respiration (or energy?). Oxygen concentration could thus limit the co-occurrence of both species and then preclude predator-prey interactions. Finally we propose a conceptual model illustrating the opportunistic foraging behaviour of jumbo squid impacted by ontogenetic migration and potentially constrained by oxygen saturation in surface waters.
巨型鱿鱼（Dosidicus gigas）在海洋食物网中作为捕食者和猎物都扮演着重要角色。我们研究了洪堡洋流系统北部巨型鱿鱼饮食组成的个体发育及时空变异性。为此，我们对2004年至2011年在秘鲁沿海收集的3618个巨型鱿鱼非空胃的广泛数据集应用了多种统计方法。共鉴定出55个猎物分类单元，我们将其归为11组。我们的结果证明了猎物组成存在很大变异性，这在其他系统中也已观察到。然而，我们的数据并不支持巨型鱿鱼在猎物组合中选择最丰富或能量最高的分类单元而忽略其他可用猎物的假设。事实上，多项模型预测表明胃饱满度随猎物分类单元数量增加而增加，而大多数内容物较少的胃仅包含一两个猎物分类单元。因此，我们的结果对捕食者会寻找单一种类猎物的局部密集聚集这一普遍假设提出了质疑。此外，巨型鱿鱼在秘鲁很少捕食秘鲁鳀（Engraulis ringens），而秘鲁鳀有大量的生物量。似乎巨型鱿鱼无法到达靠近海岸的氧气不饱和水域，而秘鲁鳀主要集中在那里。实际上，即使巨型鱿鱼白天能在缺氧的深水中觅食，之后也需要表层正常含氧量的水来恢复维持呼吸（或能量？）。因此，氧浓度可能会限制这两个物种的共存，进而排除捕食者与猎物之间的相互作用。最后，我们提出了一个概念模型，说明巨型鱿鱼受个体发育迁移影响且可能受表层水氧饱和度限制的机会主义觅食行为。
