*5.3. Management*

The preservation of the habitats suitable for *N. canestrinii* survival is the main objective to be achieved by creating protection plans that regulate the human activities [87]. However, from 1992 to 2018, only four Italian projects co-funded by European LIFE programme, dedicated to restoration of coastal lagoon ecosystems, indicated *N. canestrinii* among target species that would benefit from the interventions ([84–86] and LIFE16 NAT/IT/000663—restoration of salinity gradient in an area of the Venice lagoon from salinity <5 towards <15 up to <25 [97]). One of them pays particular attention to the salinity values, introducing freshwaters and restoring the lagoon original gradient that would favour *N. canestrinii* increase [89,97]. Despite that it shares the same sub-habitat as *K. panizzae*, no competition seems to exist, whereas in the Po Delta, di fficulties to access the structures to build the nest have been observed for the coexistence between *Pomatoschistus marmoratus* and *Salaria pavo* [18]. Therefore, particular attention has to be paid to keep not only the morphological structures of saltmarshes with their tidal creeks and pools, but also the bottom undisturbed to favour the presence of submerged objects, such as shells. On the fishing managemen<sup>t</sup> plans, the activities impacting the bottoms have to be carefully assessed to avoid the sediment resuspension and the nest destruction. As an example, in the late 1990s, in the Venice lagoon, the clam harvesting activity with hydraulic and mechanical dredging systems that dug 10–30 cm deep furrows dramatically a ffected the biological equilibrium and the benthic communities [98,99].

Moreover, the introduction of allochthons Gobionellidae could be a serious threat due to the competition for resources.

### **6.** *Valencia* **spp.—Order Cyprinodontiformes**

In Annex II of the Habitat Directive, other two Cyprinodontiformes species are listed belonging to the family Valenciidae: the Spanish endemism *Valencia hispanica* and the Greek *Valencia letourneuxi*. Both *V. hispanica* and *V. letourneuxi* are priority species (indicated with an asterisk in Annex II, under Article 1 letter h), whose preservation required special responsibility. They are freshwater species, but, living in coastal lakes or pounds and sometimes tolerating low salinity, can be a significant indicator of coastal lagoon status.

### *6.1. Valencia hispanica (Valenciennes, 1846)*

### 6.1.1. Biology and Distribution

The distribution of *V. hispanica* is limited to the coast of eastern Spain, where it lives in small freshwater systems (pools and marshes) and occasionally in brackish areas, such as lagoons or estuaries. Adult males, on average smaller (<6.7 cm) than females (<7.1 cm), have a blue-grey coloration with narrow dark cross bars and yellow/orange edge on pectoral and caudal fins. They are slow-growing individuals who can live beyond 4 years for females and over 3 for males; sexual maturity is reached late, but multiple spawning can be observed in the period between April and June [100]. Although behavioural differences among individuals of the same population can occur, the general tendency of the species is to feed on 3 types of prey (Gammaridae, Sphaeromatidae and Chironomidae larvae) and preferably on living organisms, which live in the muddy/sandy vegetated seabed or on the surface of the water. The high specialization in the diet, even if prey of other groups can be available, seems to be one of the main constraints for the survival of the species [56]. In addition, other threats are added, such as habitat loss or fragmentation, the introduction of exotic species such as *Gambusia holbrooki*, and worsening water quality. *V. hispanica* and *G. holbrooki* can interact frequently because they tend to move vertically in the water column. Numerous *G. holbrooki* aggression phenomena have been observed, with negative consequences for *V. hispanica* courtship activities and feeding rates [60].
