Artificial substrates as a tool for the conservation of the Italian Spring Goby (Orsinigobius punctatissimus).

The Italian Spring Goby (Orsinigobius punctatissimus) is a critically endangered freshwater fish species native of the River Po plain. It thrives in habitats with spring water, including resurgences and oxbow lakes. Reproduction typically occurs in spring and summer, where suitable substrates such as stones, branches, and leaves are used for eggs laying. Male parental care extends from eggs fertilization until hatching. In the last decades, threats such as spring droughts, climate change, pollution and habitat loss have led to the 70% decline in the distribution of the species across Lombardy region, resulting in habitat fragmentation, decrease of suitable reproductive substrates, and consequently impairments of the reproduction and population decline. Thus, the improvement of reproductive substrate including artificial substrates emerged as a promising conservation strategy for this species. In this study, we tested the efficiency of the improvement of reproductive substrate including hollow bricks into 10 springs where populations of the Italian Spring goby were detected. Springs were visited every two weeks to check for the use and effectiveness of artificial substrates for the reproduction, as well as to measure environmental variables. We observed reproduction and eggs deposition 2 weeks after the substrates were positioned. Multiple depositions were observed in the same hollow brick, with a preference for the smaller holes. Although the holes were also used by the red swamp crayfish (Procambarus clarkii) it was possible to detect eggs of the Italian Spring Goby at different developmental stages. These findings indicate that artificial substrates can be used as a safe reproductive refuge and therefore representing a promising strategy for the conservation of Italian Spring Goby populations.