Spiny fish (Gasterosteus gymnurus): population situation in the Gobela and Asua rivers (Bizkaia) - Euskadi Nature Information System

Spiny fish (Gasterosteus gymnurus) is a taxon listed in the category of Vulnerable in the Basque Catalogue of Endangered Species of Wild and Marine Fauna and Flora (Decree 167/1996 of 9 July 1996 of the Basque Government). For its part, Bizkaia has a Management Plan for the species in which the areas of special interest for it are determined, two of them being the Gobela and Asua rivers. Precisely in the course of the river Gobela several years ago some works of great entity that involved profound changes in the environment and that forced the rescue of the specimens of spiny fish to avoid their death during the phase of works. Another of the actions carried out was the translocation of these rescued fish to the Asua River, a basin very close to that of the Gobela. Four years after the end of the works, it was especially important and timely to know the current situation of this species cataloged in both areas of special interest. Thus, through the use of electrofishing, four sampling stations were prospected in March 2020 in the Gobela River (in the affected area in the works phase) and two others in the Asua River (in the section in which the thorny ones rescued in the works were released). In the samplings carried out in the Gobela River, 8 different species were caught: Spiny fish (Gasterosteus gymnurus), goby (Gobio lozanoi), piscardo (Phoxinus bigerrii), loina (Parachondrostom miegii), eel (Anguilla anguilla), gambusia (Gambusia holbrooki), barbo de Graells (Luciobarbus graellsii) and flounder (Platichtys flesus). In the waters of the Asua river were 6 species detected: goby (Gobio lozanoi), piscardo (Phoxinus bigerrii), loina (Parachondrostoma miegii), locha (Barbatula quignardi), eel (Anguilla anguilla) and trout (Salmo trutta). It has been found that the whole stretch of the Gobela River affected by the works has been recolonised by the thornfish, with the highest densities being obtained in the stretch where the aquatic vegetation is most prosperous and, therefore, in the area where the habitat is most natural and, presumably, most suitable. In two of the stations of this river, the density of the species is higher than that obtained in the previous fauna rescue works, while in the other two the population contingent has decreased. Finally, it should be noted that no specimen of thornfish has been caught in the two stations prospected in the Asua River, so it can be said that the acclimation and colonization of the species in this channel after the translocations that were carried out have been null.裸腹棘鱼（Gasterosteus gymnurus）被列入《巴斯克地区野生与海洋动植物濒危物种名录》（巴斯克政府1996年7月9日第167/1996号政令），分类等级为易危。西班牙比斯开省针对该物种制定了专项管理计划，明确了其重点保护栖息地，其中戈贝拉河与阿苏阿河为两处核心保护区域。早在数年前，戈贝拉河河道内曾实施大规模工程，对流域生态环境造成了显著改变，工程实施期间为避免该物种个体死亡，需开展种群抢救工作。同期实施的另一项辅助措施为：将抢救获得的裸腹棘鱼个体转迁至距离戈贝拉河流域较近的阿苏阿河。工程结束四年后，评估这两处重点保护区域内该物种的当前生存状况，既具有重要科学意义，也恰逢其时。为此，研究团队于2020年3月采用电渔法开展野外采样：在戈贝拉河工程影响河段共设置4个采样点，在阿苏阿河已释放抢救个体的河段设置2个采样点。在戈贝拉河的采样中，共捕获8种鱼类：裸腹棘鱼（Gasterosteus gymnurus）、洛萨诺鮈（Gobio lozanoi）、比格鱥（Phoxinus bigerrii）、米氏副切唇鱼（Parachondrostoma miegii）、欧洲鳗鲡（Anguilla anguilla）、霍氏食蚊鱼（Gambusia holbrooki）、格氏亮鲃（Luciobarbus graellsii）以及欧洲欧鲽（Platichthys flesus）。在阿苏阿河的采样中共检测到6种鱼类：洛萨诺鮈（Gobio lozanoi）、比格鱥（Phoxinus bigerrii）、米氏副切唇鱼（Parachondrostoma miegii）、奎氏条鳅（Barbatula quignardi）、欧洲鳗鲡（Anguilla anguilla）以及褐鳟（Salmo trutta）。调查结果显示，戈贝拉河受工程影响的全河段均已被裸腹棘鱼重新定殖；其中水生植被最为繁茂、生境最接近自然状态的河段，该物种的种群密度最高。在该河段的2个采样点中，裸腹棘鱼的种群密度高于此前抢救工程实施阶段的监测结果，而另外2个采样点的种群数量则有所下降。最后值得注意的是，阿苏阿河的2个采样点均未捕获到裸腹棘鱼个体，由此可见，此次转迁实施后，该物种在阿苏阿河流域的驯化与种群定殖均未获得成功。