The Alboran Sea and the Balearic Islands are two contrasting areas in terms of primary productivity. The former is among the most productive areas of the whole Mediterranean Sea, whereas the Balearic Islands is among the less productive ones in the western Mediterranean. The two areas also show different patterns in the bottom trawl fishing footprint. In the Alboran Sea, the fishing effort on the upper slope is much higher than in Balearic Islands. However, the opposite applies to the middle slope, the vast majority of it remaining unexploited in Alboran Sea, whereas a widespread fishery targeting blue and red shrimp Aristeus antennatus develops in Balearic Islands.

Galeus melastomus is a small demersal shark species inhabiting slope bottoms, where adults and juveniles are segregated and concentrate in the middle and upper slope, respectively. It feeds intensively on mesopelagic preys which, in turn, feed on low trophic level organisms close to primary producers. In this work we aimed to study the effect of surface primary production on the condition of deep sea demersal communities. We compared the condition, diet and potential intra- and inter-species competition for feeding resources in the juveniles of G. melastomus between Alboran Sea and Balearic Islands. The comparisons of Le Cren’s relative condition factor, and hepatosomatic and digestivosomatic indices evidenced an opposite pattern to that a priori expectable: better condition in the less productive area. The analysis of stomach contents showed similar diets in both areas, but lower food ingestion in Alboran Sea than in Balearic Islands. Different abundances of potential intra- and inter-specific competitors for feeding resources in the two areas, apparently linked to the different fishing footprints, seems the most likely explanation for the better nourished individuals in Balearic Islands. Whereas juveniles of G. melastomus dominate the shark community in the Balearic Islands upper slope, where the presence of adults of this species is almost negligible, in Alboran Sea this stratum is dominated by adults and potential competitors of other small demersal shark species. All shark species together, including G. melastomus, showed abundances 38% higher in Alboran than in Balearic Islands. Our results show that condition of deep sea demersal fish is ruled by complex inter-relationships among different factors, needing the combination of biological, ecological and fisheries knowledge to understand its variability.

就初级生产力而言，奥尔博兰海和巴利阿里群岛是两个截然不同的地区。前者是整个地中海生产力最高的地区之一，而巴利阿里群岛是地中海西部生产力较低的地区之一。这两个区域在底拖网捕鱼足迹中也显示出不同的模式。在奥尔博兰海，上坡的捕捞努力量远高于巴利阿里群岛。然而，中坡的情况正好相反，其中绝大多数在奥尔博兰海仍未开发，而在巴利阿里群岛则发展了以蓝虾和红虾为目标的广泛渔业。

Galeus melastomus是一种栖息于斜坡底部的小型底栖鲨鱼物种，成鱼和幼鱼被隔离并分别集中在中坡和上坡。它主要以中层猎物为食，而后者又以靠近初级生产者的低营养级生物为食。在这项工作中，我们旨在研究地表初级生产对深海底层群落状况的影响。我们比较了G. melastomus幼鱼的条件、饮食和潜在的种内和种间饲料资源竞争位于奥尔博兰海和巴利阿里群岛之间。Le Cren 的相对状况因素与肝体和消化体指数的比较证明了与先验预期相反的模式：生产力较低的地区状况更好。胃内容物分析表明，这两个地区的饮食相似，但奥尔博兰海的食物摄入量低于巴利阿里群岛。在这两个地区，不同的潜在物种内和物种间竞争者的丰富程度不同，这显然与不同的捕鱼足迹有关，这似乎是巴利阿里群岛个体营养状况更好的最可能解释。而G. melastomus 的幼鱼在巴利阿里群岛上坡的鲨鱼群落中占主导地位，在那里该物种的成鱼几乎可以忽略不计，在奥尔博兰海，这一层主要由成鱼和其他小型底栖鲨鱼物种的潜在竞争者主导。包括G. melastomus在内的所有鲨鱼物种在奥尔博兰的丰度比在巴利阿里群岛高 38%。我们的研究结果表明，深海底层鱼类的状况受不同因素之间复杂的相互关系支配，需要结合生物、生态和渔业知识来了解其变异性。