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Tunas off northwest Africa: The epipelagic diet of The Bigeye and Skipjack tunas
Fisheries Research ( IF 2.4 ) Pub Date : 2021-03-03 , DOI: 10.1016/j.fishres.2021.105914
Joana Romero , Paulo Catry , Margarida Hermida , Verónica Neves , Bárbara Cavaleiro , Lídia Gouveia , José Pedro Granadeiro

Tunas are among the most exploited top predators worldwide, with negative impacts on some of their stocks. Changes in their population abundance can impact marine food-webs and have the potential to alter entire ecosystems. To better understand the impacts of the exploitation of tuna stocks in the most critical habitats, basic knowledge on the diet of these species in each region is required. Here, we describe the diet of the two most fished tuna species in the archipelago of Madeira, the Bigeye tuna Thunnus obesus and the Skipjack tuna Katsuwonus pelamis, based on stomach contents analysis. To gain further insights into the diet, and also better assess the possible bias caused by the occurrence of live bait in stomachs, we compared tuna mercury values with those of two other predators with similar diets that are not directly targeted by fisheries, and with Bigeye and Skipjack tunas from other ocean basins. Bigeye tunas fed mostly on Atlantic chub mackerel Scomber colias and mackerel Trachurus sp., which together contributed with 85% of total prey weight. Only 7.5% of prey weight was constituted by mesopelagic prey, including myctophids and cephalopods. Skipjack tunas had an epipelagic diet (NF = 97%), with the Atlantic chub mackerel representing half of the total prey weight, despite Longspine snipefish Macroramphosus scolopax and Sand smelt Atherina sp. accounting for 62.9% of the total number of prey. There were interannual variations in diet likely linked to interannual pelagic community shifts. Bait did not bias the results of the stomach analysis of these tunas and bait species were observed to be part of the natural diet of both tuna species. Baseline data provided by this study should allow for more informed decisions for an efficient ecosystem-based fisheries management.



中文翻译:

非洲西北部的Tunas:Bigeye和Skipjack tunas的上层饮食

金枪鱼是全球最被开发利用的顶级捕食者之一,对其一些种群造成负面影响。人口数量的变化会影响海洋食物网,并有可能改变整个生态系统。为了更好地了解在最关键的生境中开发金枪鱼种群的影响,需要有关每个区域这些物种饮食的基本知识。在这里,我们描述了马德拉群岛上两种捕捞最多的金枪鱼的饮食,大眼金枪鱼金枪鱼金枪鱼和and鱼金枪鱼Katsuwonus pelamis,根据胃内容物分析。为了进一步了解饮食,并更好地评估由活饵在胃中引起的可能偏倚,我们将金枪鱼的汞含量与其他两种捕食者的捕食者的汞含量进行了比较,这些捕食者的饮食没有被渔业直接作为目标,而Bigeye的捕食方式并非如此。和其他海盆的Ski鱼金枪鱼。大眼金枪鱼馈送大多科利鲭鲐豆粉蝶属和鲭鱼竹荚属,其与总重量猎物85%一起作出了贡献。只有7.5%的食肉重量由中生食肉动物组成,包括食肉动物和头足类动物。Long鱼金枪鱼的表皮鱼类为上皮饮食(NF = 97%),尽管有Longspine ipe鱼,大西洋chu鱼仍占猎物总重量的一半Macroramphosus扇贝和沙冶炼Atherina sp。占猎物总数的62.9%。饮食中存在年际变化,可能与年际中上层群落转变有关。诱饵没有对这些金枪鱼的胃分析结果产生偏见,并且观察到诱饵是两种金枪鱼自然饮食的一部分。这项研究提供的基准数据应有助于作出更明智的决定,以便进行有效的基于生态系统的渔业管理。

更新日期:2021-03-03
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