*2.3. Management*

Some recent works were conducted to assess the ecological value of artificial habitats (ditches) for the species, with a view to manage and preserve these habitats as surrogates of saltmarsh areas [28,49]. In the Venice lagoon, abundant, well-structured, healthy and successful breeding populations were, in fact, observed in abandoned artificial ditches, once used for traditional fish farming, as small marinas or as a defence line during the two world wars [49]. These artificial ditches, located in marginal areas, completely isolated from the open lagoon, can o ffer protection from predators, high resources and determine di fferent adaptive strategies. In the lagoon of Venice, it was observed that the populations of natural salt marshes had a higher mortality rate than those of artificial canals, in a probable relation with a higher predation pressure due to the presence of piscivore fishes. The di fferent predatory pressure, combined also with a greater availability of food, has favoured the development of di fferent life histories in the populations of artificial ditches, which live longer and invest more in growth and less in reproduction [28]. These artificial ditches can, therefore, be an important resource for the conservation of local populations, but it remains important to maintain natural ecosystems in their complexity.

The strong sedentary behaviour of the species can seriously compromise its ability to adapt to environmental changes in response to human pressure, because the gene flow is reduced and it cannot guarantee a su fficient genetic variability [24,25,32]. On the other hand, the strong relationship with the habitat is an important feature when choosing the species as an indicator of habitat conservation status. Its survival and reproductive rate, in fact, depends on the possibility to find sheltered areas with low hydrodynamism. On the whole, the salt marsh structures with small tidal creeks and pools have to be maintained and protected from erosion processes but, at the same time, the connectivity among similar habitats has to be guaranteed, avoiding the fragmentation, due to land reclamation or to the construction of infrastructures or to the dredging of large and deep canals. Although sedentary, the connectivity between salt marsh areas or even lagoon systems may allow some small migrations and, hence, a better gene flow.

Considering the water quality of some habitats where the species is generally abundant, it does not seem necessary to pay particular attention to the trophic status, whereas heavy metals and organic pollutants seem to a ffect the reproduction [50] and to cause spinal deformities [51].

The mosaic of habitats occupied by the species should be investigated and managed also in relation to potential competition and distribution of *G. holbrooki*. Specific managemen<sup>t</sup> actions to reduce the impact of *G. holbrooki* on *A. fasciatus* were not found, but some authors described how to intervene with other native species, mainly in freshwater habitats. An e fficient managemen<sup>t</sup> plan of interventions could require the following actions:


### **3.** *Aphanius iberus* **(Valenciennes, 1846)—Order Cyprinodontiformes**

### *3.1. Biology and Distribution*

*A. iberus* is an endemic species of the Mediterranean coasts of Spain, often abundant in salt flats and brackish waters, but, sometimes, also present in freshwaters. It has a short life cycle (about 2 years), but a rapid growth rate and strong interannual variability in recruitment [54]. Several morphotypes are recognized, but the degree of di fferentiation is similar to that of other species of the genus *Aphanius*. The male has bluish grey, olive to bluish green body [18] with narrow silvery cross bands that also extend to the tail fin; the female has an olive green or bluish body with small black spots that tend to form stripes, one of which overlaps the lateral line. Males are also on average smaller (4.5 cm) than females (6.0 cm). The sex ratio is rather variable, but, in general, females are more abundant, due to male mortality after spawning [18]. As for the diet, it is omnivorous, combining both animal (mainly crustaceans) and plant of detritic origin [55]; as a generalist, it could be able to survive even the severe changes su ffered by estuarine and coastal habitats [56]. In fact, the diet may vary depending on the availability of prey and, although it is generally considered to be a benthivorous micropredator, close correlations with organisms in the water column have been observed, particularly in juveniles. When available, harpacticoid copepods are the dominant prey above all for smaller fish; larger fish tend to add some larger prey without completely changing the trophic niche and feeding habitat with growth [55]. *A. iberus* is a gonochoric species with a reproductive strategy typical of unstable

environments, as it reaches sexual maturity early, already a few month-olds, investing a lot of energy. The period of spawning varies depending on the latitudes, between May and August in the Ebro Delta (Catalonia, Spain) [57] and until October/November to the south, in the Mar Menor (Murcia, Spain) [58]. In one season, multiple spawning events take place [57]. Spawning and egg hatching can occur at salinities between 5 and 60 and temperatures 22–28 ◦C [18]. Populations of *A. iberus* from two areas in Catalonia (Spain) 300 km apart displayed significant genetic divergences [18]. Moreover, the species of *Aphanius* of the Atlantic coast of Spain, following genetic studies, has been recognized as *A. baeticus* and not as *A. iberus* [57].
