Understanding the distribution and habitat preferences of the Italian Spring Goby (Orsinigobius punctatissimus) in the springs of Lombardy

The Italian Spring Goby (Orsinigobius punctatissimus) is an endemic freshwater fish species considered Critically Endangered by the Italian IUCN committee. This species is closely associated with highly specific and isolated habitats, such as springs and oxbow lakes in the River Po plain, where Lombardy constitutes half of the species' range. Because of spring droughts, pollution, habitat loss and fragmentation, the species distribution in the freshwater ecosystems of Lombardy has been estimated being decreased by 70% in recent decades. However, information on the presence and ecology of this species is very limited because of the scarcity of monitoring activities in suitable habitats. For instance, the current knowledge about the habitat preferences of the species is outdated and based on past qualitative observations. Therefore, the aim of this study is to enlarge the knowledge on the ecology and distribution of the Italian Spring Goby in spring ecosystems of the Lombardy region. In spring-summer 2023 and 2024, we surveyed more than 130 springs spanned over a longitudinal gradient, collecting data on the presence of the species and fish community, as well as biotic and abiotic features of the spring. We found the species in 25 springs, corresponding to the 19% of the sampled sites. Results showed that the main predictive variables for the presence and abundance are morphological features such as substrate type, average depth, illumination, and retention of organic debris. This study provides novel insights into the habitat preferences of the Italian Spring Goby and its regional distribution.