*3.2. Conservation Status*

Along the Spanish coast, seven operational conservation units (OCUs) were distinguished with an overall low gene diversity [59]. The degree of isolation of populations is very high and it was observed that small-sized *A. iberus* can have a really restricted home range (approx. 250 m) [48]. The high sedentary behaviour has been accentuated by the fragmentation of habitats and the heavy changes suffered by the estuarine and coastal environments, such as the increase in intensive farming practices, the diversion of waterways, tourism pressure related to seasonal variability of domestic effluents and to nautical activities, the use of wetlands for rice cultivation, and aquaculture [5,55]. The tendency of *A. iberus* to prefer isolated areas is one of the main factors that threatens its survival in an environmental context in which human pressures have accentuated the fragmentation of the territory. The scarce gene flow, as in the case of *A. fasciatus*, can seriously compromise adaptative processes. In addition, habitat destruction (e.g., salt mines along the coast), water pollution and the introduction of exotic species, especially *Gambusia holbrooki*, are factors that need to be counteracted and to which conservation actions need to be directed. Laboratory and mesocosm experiments have identified the possible negative effects that *G. holbrooki* can have on native populations. The coupling of *G. holbrooki*'s aggressive behaviour toward *A. iberus*'s adults and the predation on its juveniles increases stress, reduces feeding rates and decreases reproductive activities [60]; although, in the wild, it tends to live more on the seabed and in saltier waters, and, hence, has fewer direct interactions with *G. holbrooki*.

In addition, continental populations, which live in small streams, are at risk of decline due to poor managemen<sup>t</sup> of aquifers, which may experience periods of drought [57]. The combination of habitat degradation with the presence of invasive species puts this species at risk according to IUCN assessments and in an unfavourable/inadequate state of conservation [61]. The species is reported at 39 Natura 2000 sites but only 29 are coastal lagoons (Table 3) and they are all distributed along Mediterranean coasts of Spain.
