*3.3. Management*

Restoration efforts aimed at increasing the connectivity of habitats in the Ebro Delta, after about 2–3 years did not show significant increases in the populations of *A. iberus*, which indeed decreased, probably due to climatic events (very low temperatures in winter and heavy rainfall with a consequent sudden change in salinity [54]). It is believed that the success of habitat restoration actions or introductions of individuals for repopulation would take about 10 years to determine whether the population will survive [54,57]. However, the reintroduction of *A. iberus*, also, may not be sufficient to reinforce the wild populations because the gene diversity is globally poor [59]. Alcaraz and García-Berthou [41] observed that the periodically flooded glasswort habitats presented a higher density of mature *A. iberus*, with the availability of both aquatic and terrestrial preys and a greater foraging efficiency. Beyond the preservation of the few areas where *A. iberus* is still present, the functional role of flooded habitats, such as the glasswort, may have significant implications to improve its conservation status [41]. *A. iberus* is demographically more fragile, and its distribution is more difficult to be managed than that of *A. fasciatus*. Despite this, more intervention projects (both national and international) have been dedicated to the managemen<sup>t</sup> and the recovery of the Spanish endemism. Since 1996, three Spanish projects were co-funded by European LIFE programme aiming at the conservation of the species by means of habitat restoration (LIFE96 NAT/E/003118—introduced 20,000 specimen in Catalonia deltas [62]; LIFE99 NAT/E/006386—restored wetlands in Catalan Baix Ter coastal lagoon [63]; LIFE09 NAT/ES/000520—recovered Ebro Delta's Alfacada and Tancada lagoon hydrologic functioning [64]). Therefore, as for *A. fasciatus*, the habitat restoration is the first objective to be addressed, even though particular attention has to be paid to the introduction of alien species. At present, *G. holbrooki* does not appear to be a threat [60], but the introduction of further competitive species can be lethal. In fact, another potential competitor could be *Fundulus heteroclitus* [65,66], which can live also in brackish and estuarine waters, even though, at present, the effects of the interaction between the two species is not described.

### **4.** *Knipowitschia panizzae* **(Verga, 1841)—Order Gobiiformes**

### *4.1. Biology and Distribution*

*K. pannizae* is an euryhaline species, endemic in the Adriatic and the Ionian Sea, where it lives in shallow, well-vegetated environments such as streams, lakes, estuaries, lagoons and terminal stretches of rivers [67]. The body is grey-yellowish with darker and reticulated mottles; the females have a body and fins that are brighter than those of males and during spawning the females' bellies are yellow [68]. It is a small predator (a few centimetres in length), of no commercial interest [69], opportunist and generalist [70], that feeds, above all, on meio-fauna and juvenile macrofauna [71–74]. Reproduction takes place in brackish waters where the life cycle is completed in about 1 year, as adults disappear after spawning during their second summer of life [69,75]. Females are generally more abundant than males [75]; moreover, the female density increases during the reproductive period, but this observation can be biased by a lower susceptibility to catching of males that remain close under the nest [69].

The reproductive strategy is r-type (abbreviate iteroparity, sensu Miller [76]), suitable for unstable environments, which leads to a rapid increase of individuals, a long breeding season with multiple spawning, and females who release at each spawn about 100–150 eggs within the nests of different males. Males, that are territorial, carry out parental care and preferably use bivalve shells as shelter and a breeding site. Both the male and the female produce sounds, while the female approaches the nest [39]. The male emits sounds while remaining in the nest and the female produces them only when the ventral part is almost in contact with the male's head. The sounds cease when the female moves away, and are not produced during courtship outside the nest, nor during the spawning. Although it is not entirely clear the role of these "pre-deposition" sounds, they are supposed to influence the choice of the male by the female [77]. The species has sexual dimorphism that manifests, above all, in the nuptial coloration of the female with a conspicuous yellow/orange pigmentation in the ventral part. This coloration depends on the pigmentation of the dermis and is closely linked to the spawning: in fact, it disappears afterwards. The presence of nuptial coloration is a signal indicating the approaching spawning and its size, which varies from individual to individual, is a reliable indicator of the quantity of eggs that will be released [78]. Since the reproductive success of the male depends on the fertility of the female, it is believed that the conspicuousness of the nuptial coloration is the ornamental character on which the male bases its choice [79]. In fact, there is no evidence of competition between females and there is no correlation between body length and ventral coloration conspicuousness [78]. It is a carotenoid-based pigmentation, which can be considered indicative of the good health of the organism. Therefore, it is believed that the male chooses females with a bigger yellow ventral patch since they are in better condition and therefore are more fertile, preferring them also to larger females but with a less extensive coloration [79]. After breeding, adults die and only juveniles survive [70,75].

The high plasticity in the diet and the reproductive strategy make this species able to survive in very unstable environments. Very abundant populations of *K. panizzae* have been observed in hypertrophic basins, such as Comacchio lagoons, where dystrophic crises are frequent. This population is probably favoured by the grea<sup>t</sup> availability of preys before dystrophic crises, then, during the

unfavourable conditions, individuals move away to areas with greater circulation and oxygenation [67]. It has also been observed, with laboratory experiments, that, as a survival strategy, in particular environmental conditions, intraspecific cannibalism can occur on juveniles or adults. Such events seem not to be determined by just food shortages but by a combination of factors: low availability of food in the reproductive period or poor quality of prey, as can happen during an anoxic crisis [74].
