Projecte Escanyagats: A Long-Term Strategy for the Conservation of Stickleback (Gasterosteus aculeatus) in Catalonia ^†

Abstract

Stickleback (Gasterosteus aculeatus) is an endangered species in Catalonia. It has disappeared from most of its historical range, including at least five whole basins, and the remaining populations continue to decline. Our monitoring, carried out on most Catalan populations in the north-east of the country, indicates that over the last 15 years there has been a reduction of between 50% and 75% everywhere. Even worse, many of the remaining populations are in heavily modified Mediterranean river stretches, subjected to multiple anthropogenic pressures or highly vulnerable to increasingly drastic droughts due to climate change. In this context, in 2018 we started a project that aims to implement a long-term, low-cost strategy for the conservation of this species in Catalonia. We have opted for a combination of broad-spectrum alternative measures: (1) Strategic restoration of small stretches of river of high interest to the species, mainly intended to ensure the maintenance of flooded pools during extreme droughts. (2) Reintroduction in river stretches with historical presence, firstly in watersheeds with extant populations. (3) Gradually, application of assisted migration to water bodies without historical presence, but with good ecological conditions for a probable successful establishment. (4) Creation of new ex-situ populations in small artificial water bodies, from urban ornamental ponds to small irrigating reservoirs, reaching agreements with the owners, and often carrying out essential previous actions, such as the exotic fish removal. (5) Continuation and extension of regular sampling, in order to implement a permanent monitoring of its trends, and expand the specific knowledge on some key aspects of its ecology. (6) Implementation of a specific environmental awareness and education campaign, as well as environmental volunteering, for the involvement of society in the conservation of this small fish and its habitats. The known genetic differentiation of the remaining populations is being taken into account in the planning of these actions. We will present the results achieved so far, and the plans for the coming years.