*4.3. Management*

Sand gobies are often dominant and they can be used as an indicator of habitat productivity. In Venice lagoon saltmarshes, in particular, their productivity was found to be higher than in other Mediterranean wetlands, reaching up to a total annual production >600 g ha−<sup>1</sup> year<sup>−</sup><sup>1</sup> [70]. The main threat compromising this significant contribution to secondary production in coastal lagoons is represented by the destruction of saltmarshes. *K. panizzae* itself is not at risk of extinction, given its high adaptability. In Italy, in fact, accidental introductions are reported along the Tyrrhenian coast, in Trasimeno and Bolsena Lakes and in Sicily, with good survival [39,70,83]. The concern could be on the survival of local populations that have to be preserved, protecting or restoring saltmarsh systems. Moreover, the reproductive rate of *K. panizzae* could be reduced by the absence of the preferred bivalve shells for nest. Beyond the interventions to preserve coastal lagoon shallow habitat, river systems can also have a significant role in population survival, as demonstrated by the fact that the populations so far attributed to *K. mrakovcici* and *K. radovici* are *K. panizzae* and usually live in freshwater environments in the Croatian Krka and Neretve basins [12]. Since 2010, *K. panizzae* has been among the target species of three Italian projects co-funded by European LIFE programme (LIFE10 NAT/IT/000256—improved hydraulic circulation and as a consequence water quality in Italian coastal salt meadows [84]; LIFE12 NAT/IT/000331—contributed to the achievement of good ecological status by transplanting seagrasses in some areas of the Venice lagoon [85]; LIFE13 NAT/IT/000115—improved hydraulic conditions in Po delta's Sacca di Goro [86]).

On the other hand, particular attention has to be paid to the accidental introduction of *K. panizzae* in other basins, because it can become invasive and compromise the ecological equilibrium in fragile ecosystems [70], entering in competition with local species with a similar ecological niche.

### **5.** *Ninnigobius canestrinii* **(Ninni, 1883)—Order Gobiiformes**

### *5.1. Biology and Distribution*

*Pomatoschistus canestrinii* has recently been attributed to the genus *Ninnigobius*, which includes few species, but is phylogenetically well-distinguished by both *Pomatoschistus* and *Knipowitzschia* [12]. *N. canestrinii* is a small goby (about 6.5 cm), epibenthic, of no commercial interest and endemic of the Adriatic basin [39,67,69]. The lifespan is at most 16 months, and the spawners disappear after spawning [75]. The body is grey to bright brown, marked with very clear black points at least on the cheeks and the opercula; males are significantly larger than females, whose coloration is, on the whole, paler than that of the males, especially during the breeding period [68]. It lives preferentially in unvegetated sandy or muddy environments at the mouths of rivers or in the shallow lagoon areas [39,80], feeding on small meiobenthic invertebrates [75,87]. Its preferred habitat, characterized by low salinity, high turbidity, shallow waters and the presence of bivalve beds, is very similar to *K. panizzae*'s one [80,88]. However, *N. canestrinii* is known to prefer lower salinity and saltmarsh-dominated areas in the inner part of the Venice lagoon [89]. This should not depend on competition between the two species, because the choice of nest, reproduction times and predation tactics [39,80] are di fferent, although there are similarities in the behaviour, including the production of sounds during the reproductive period [77,90]. *N. canestrinii* is less selective in the choice of the nest, which is created using shells, stones, bowls and any submerged object [39]. The male has a territorial behaviour for the defence of the nest and carries out parental care until the hatching of the eggs. Although the mechanism of sound production is not clear, it has been observed that, in the phase immediately before the spawning, the male "communicates" with the female, which in turn manifests a very active behaviour [90].

The species of the Gobionellidae family are often dominant in the communities of temperate and tropical transition environments [91] and, above all, the smaller ones play an important role in the trophic network as they favour the turnover of resources present in mobile sediments [69]. Well-structured populations are present in the lagoon of Venice [80,88] and in the basins of the Comacchio lagoons [67]. However, since this species does not tolerate salinity over 30, it is often also observed in oligohaline and freshwater environments [87], in some of which it was introduced accidentally, i.e., Trasimeno Lake in Italy [92] and reservoir of the Riˇcica River in Croatia [82,93]. Records were also made in Bosnia-Herzegovina, in the freshwaters of the coastal lake Svitava in the Neretve basin [94]. As the environmental characteristics of the Neretve Delta are potentially ideal as a habitat for *N. canestrinii*, Tutman et al. [94] hypothesize that it has always been present in that areas, but that in the past no special attention has been paid to investigate its presence.
