Valle San Leonardo

In the fishing valleys, the skilled hand of man regulates the salinity and turbidity of the water to promote the growth of submerged flowering vegetation

In this way, true underwater prairies are formed, which, depending on the composition of the seabed and salinity, can host different species of plants.

Where salinity is lower, meadows of Sea Grass (Ruppia cirrhosa) extend, while in areas with higher salinity, the Dwarf Eelgrass (Nanozostera noltii) thrives. These plants are very important because they stabilize the seabeds, clean the water, retain suspended particles, and dissolved organic substances: an excessive accumulation of these could become harmful to the valley and trigger phenomena of anoxia, insufficient oxygen in the environment.

Moreover, these plants provide valuable nourishment for waterfowl, especially for ducks, which base their winter diet precisely on their presence, and for other valley fauna.

Marine macrophyte meadows represent a unique environment in the territorial landscape, so much so that there are no similar counterparts in coastal lagoons or other similar environments.

Of considerable importance in terms of valley vegetation are the parts of land that emerge from the water. The mudflats and “ponsaùre” are flat islets often shaped by man to favor internal hydraulic circulation in the valley’s lakes, to create discontinuities in the seabeds, and to provide resting areas for species of hunting interest.

Together with the “arginelli” (embankments), built to divide the different water bodies, they host very important vegetation, which has adapted to live with high concentrations of salt in the substrate and this is defined as halophilic vegetation, meaning it thrives in salty environments and therefore defined as halophilous, i.e. salt-loving, vegetation.

The various plants are distributed according to the height of the mudflat, the distance from the water, and the tolerance of salt in the substrate: the less tolerant plants are positioned near the water, where the salt is more diluted, while those that tolerate it more are found on the summit, where it is less present. Here we find the annual Salicornia (Salicornia veneta), the Sea Aster (Tripolium pannonicum), the Sea Purslane (Halimione portulacoides), the Sarcocornia Glauca (Arthrocnemum mascrostachyum), the Sea Lavender (Limonium narbonense), and many other valuable species.

These associations are favored by waterfowl as a breeding site.

The fishing valleys are extensive farms for fish species of high commercial interest, maintained in a semi-natural state, without artificial feeding or the administration of other products

The farmed fish, Gilthead Seabream (Sparus aurata), European Sea Bass (Dicentrarchus labrax), European Eel (Anguilla anguilla), Sand Smelt (Atherina boyeri), and the Mullets, remain in the waters of the valley until they reach the right size, living according to their natural dynamics, maintaining all the characteristics of properly wild species, including the tendency to migrate. The collective name “cefali” (from the Greek kephalē, meaning head) groups together five different species of fish  that are very similar to each other, although they have different habits and various divisions in terms of diet and commercial value: Mugil cephalus, Liza ramada, Liza saliens, Liza aurata, Chelon labrosus.

Dialectal names of valley fish: The Thicklip Grey Mullet or Flathead Grey Mullet (Mugil cephalus), the Thinlip Grey Mullet (Liza ramada), the Leaping Mullet (Liza saliens), the Golden Grey Mullet (Liza aurata), the Thicklip Grey Mullet (Chelon labrosus), the European Eel (Anguilla anguilla), the European Sea Bass (Dicentrarchus labrax).

In addition to these, there are also numerous small species without commercial value, due to their small size, but very important from a naturalistic point of view. We find, in fact, the Mediterranean Gull (Aphanius fasciatus), a species typical of lagoon and more open valley waters, equipped with algal vegetation, the Lagoon Goby (Knipowitschia panizzae), and the Sand Goby (Pomatoschistus canestrinii). The last two species, in particular, are endemic to the coastal wetlands of the Upper Adriatic, and as such, very rare and localized. They reproduce at the bottoms of the valleys and lagoons of the Delta, hiding the eggs inside shells of dead shells or other structures, and practice parental care for the eggs.

Valleys with lower levels of salinity can also host fish communities typical of freshwater, such as the Common Carp (Cyprinus carpio), the Crucian Carp (Carassius carassius), the Black Bullhead (Ameiurus melas), alongside other species typical of the surface water network of the Delta area.

At the end of autumn, after a flight of nearly a thousand kilometers, the ducks  arrive in the valleys of the Po Delta. They are migratory birds that winter in the south, coming from the north, from the tundra and the taiga—semi-desert areas that become inhospitable in winter due to extremely cold temperatures, the few hours of light, and the almost total lack of food

For ducks, the fishing valley represents the ideal ecosystem to meet the needs of each individual species; for this reason, flocks of thousands of individuals form in the valleys, which will remain in the valley throughout the winter to return to reproduce in spring in northern Europe.

Ducks are divided into two main groups: surface-feeding ducks and diving ducks. The first group includes: Wigeons (Anas penelope), Mallards (Anas platyrhinchos), Gadwalls (Anas strepera), Northern Pintails (Anas clipeata), and Northern Shovelers (Anas acuta): they are surface-feeding ducks, so-called because they do not fully immerse themselves and feed by filtering water or at most by immersing their neck. These ducks prefer shallow, even brackish waters of large lakes rich in “eelgrass” (Ruppia maritima), an aquatic plant with a typical filamentous appearance. Other surface-feeding ducks, such as Teals (Anas crecca) or Garganeys (Anas querquedula), instead frequent the small channels between the reeds at the edges of the valley where it is easier to hide.

In the fishing  valleys, we also find large deep lakes, with freshwater or brackish water, which host diving ducks: Tufted Ducks (Aythya feligula), Common Pochards (Aythya ferina), Greater Scaups (Aythya marila), Ferruginous Ducks (Aythya nyroca), and sometimes also Red-crested Pochards (Netta rufina), which unlike the former are able to dive completely and reach the depths to fish mollusks, invertebrates, or small fish, which are abundant in the valleys.

Surface-feeding and diving ducks can be distinguished from each other by the way they take off: surface-feeding ducks can take off vertically, while diving ducks have a rather clumsy takeoff; they must indeed run along the water’s surface for a long time before they can fly, and this is due to the position of their legs, which are more backward than the former, allowing them to swim more easily during immersion.

Ducks do not only frequent the valleys for wintering. Some species also find the ideal place to nest, as Mallards and Common Shelducks (Tadorna tadorna) do, which lay their eggs on the valley’s ridges covered with vegetation or in small cavities in the ground, and then incubate them.

Dialect sayings:
 “Fin a Nadale se spéna, dopo Nadale se pena” a saying used by valley hunters to indicate the propitious times for hunting: good until Christmas, increasingly scarce after that date.

Dialect names of ducks:
Masorin (Mallard), Pignòlo (Gadwall), Sarsègna (Teal), Crècola (Garganey), Dasià, Asià (Pintail), Ciòsso (Wigeon), Fòfano (Shoveler), Magàsso (Pochard), Penacìn, Magassìn (Duck), Brinon co (Gray Duck), Risaròla (Tabard duck).

Among the many bird species that inhabit the valleys, some are more easily visible due to their size and attract the attention of those who spend time in these environments

They belong to the order Pelicaniformes: wading birds with long legs, necks, and bills; birds of various families; herons, egrets, and bitterns of the Ardeidae family, which retract their long necks in flight; storks of the Ciconiidae family, which instead keep their necks elongated and fly high; ibises and spoonbills of the Threskiornithidae family. The most numerous family is that of the Ardeidae.
The most common species are the white Little Egret (Egretta garzetta) and the Grey Heron (Ardea cinerea), both resident, joined in winter by the Great Egret (Ardea alba) and the Eurasian Bittern (Botaurus stellaris).

During the day, it is easy to see them, motionless in shallow waters, patiently waiting like fishermen for prey that they spear with their bills thanks to a sudden movement of their long necks.
In wooded areas, on the edges of the valleys, “heronry” form, colonies of herons of various species, which also include the Black-crowned Night Heron (Nycticorax nycticorax), the Squacco Heron (Ardeola ralloides), and the Purple Heron (Ardea purpurea), which arrives in spring and joins the others for nesting.

The Glossy Ibis (Plegadis falcinellus) and the Eurasian Spoonbill (Platalea leucorodia) are instead more active in searching for food in shallow and muddy waters. The Glossy Ibis gets its name from “mignatte,” an archaic term for leeches, which along with other aquatic invertebrates, are part of its diet.

It is the peculiar shape of the bill that gives the Spoonbill its name, as it slowly moves its broad beak from side to side, rhythmically probing the water and the bottom in search of prey. When these touch the particularly sensitive inner wall of the beak, it instantly closes, trapping them.

For over twenty years, numerous colonies of Greater Flamingos (Phoenicopterus roseus) have been encountered in the valleys: beautiful and elegant, noisy and dancing, they seem to dance in shallow waters; in this way, they make the mud more fluid before filtering it with their bill, which, equipped with special lamellae, can retain the microorganisms and small crustaceans they feed on. However, the fact that this fluidized mud can be negative for fish, as when with the bora wind the marsh forms (the mud at the bottom rises clouding the water), which, settling on the fish’s gills, suffocates it.

The avifauna of the valley is largely composed of birds that feed on fish: many are omnivores, with fish making up a portion of their daily diet; others, however, feed exclusively on fish

Among them, there are those who enjoy, in addition to fish, herbs and seeds, or crustaceans, mollusks, and gastropods; but also, feeding, as in the case of herons, on amphibians, reptiles, and small mammals Among them, there are those who enjoy, in addition to fish, herbs and seeds, or crustaceans, mollusks, and gastropods; but also, feeding, as in the case of herons, on amphibians, reptiles, and small mammals

Those that predominantly feed on fish are called ichthyophages, and they use surprising techniques for fishing. Spectacular are the dives from above by Terns, kingfishers (Alcedo atthis), and little Terns (Sterna albifrons), capable of hovering in the air, rapidly beating their wings: this technique, called the “Holy Spirit,” is used to spot prey in the water, which these birds catch using their “specialized” beak. The Osprey (Pandion haliaetus), which fishes using the same technique, uses its powerful talons to catch prey.

The quintessential piscivorous species are the Great Cormorant (Phalacrocorax carbo) and the smaller Pygmy Cormorant (Phalacrocorax pygmeus); the Cormorant, in particular, has large feet with large membranes that allow it to push underwater powerfully, where it can fish even at depths of 6 meters.

Adaptable to both fresh and saltwater, the Cormorant has permeable feathers and for this reason, spends a lot of time with its wings open to the wind or sun to dry itself; but the Cormorant is above all a very skilled hunter. Its predatory ability is facilitated by the fact that it is one of the few species capable of moving its eyes, making it easier for the individual to catch a wide variety of fish, which it swallows whole once brought to the surface. For these reasons, in Asian countries, the Cormorant is used as a fishing tool.

A study conducted in the Po Delta (Volponi, 1997) reports data indicating a diet of 350-500 grams of fish per day for each individual.

In recent years, Cormorants and Pygmy Cormorants have become particularly numerous in the Po Delta, especially in the winter period, to the point of becoming a real threat to fish farming and even to the survival of fishing in the valleys.

Waders, literally ‘the inhabitants of the mud,’ are a group of aquatic birds that have developed a series of adaptations that allow them to live in shallow waters with muddy bottoms, where they catch the invertebrates they feed on using beaks of various shapes and lengths

Many of these birds winter or breed in valley environments, while others frequent  them to rest and feed during their long migrations from the Arctic tundra to the coasts of southern Africa. Among the species that can be found in wetland habitats, it is worth mentioning the elegant Black-winged Stilt (Himantopus himantopus), with its black and white body and long red legs, which nests among the perennial glassworts. The Avocet (Recurvirostra avosetta), with its distinctive upward-curving beak, is also noteworthy and is a target species of the LIFE project “Natura 2000 in the Po Delta”. Similarly, the Kentish Plover (Charadrius alexandrinus), a small and rare wader that nests on vegetation-free islets, camouflages its eggs among shells and other debris. Other important species, although not listed as project targets, include the Oystercatcher (Haematopus ostralegus), which feeds on bivalve mollusks by forcing their shells open with its powerful orange chisel-shaped beak, and the Common Redshank (Tringa totanus), a noisy wader that nests on islets covered with halophytic vegetation.

Terns and gulls: numerous target species of the LIFE project “Natura 2000 in the Po Delta” belong to these two families and nest in wetland habitats, where anthropogenic management creates favorable conditions for reproduction. The Common Tern (Sterna hirundo), the Little Tern (Sternula albifrons), and the Gull-billed Tern (Gelochelidon nilotica) are species that form substantial colonies, sometimes consisting of hundreds of breeding pairs, in these environments, nesting on sandbars and artificial embankments, and feed in water bodies by hunting small fish and invertebrates, diving below the water’s surface. They are long-distance migrants with long and slender wings, suitable for long journeys. The Mediterranean Gull (Ichthyaetus melanocephalus) is another target species of the project, recognizable by its black hood and beautiful coral-red legs and beak. It frequents the fishing valleys, also forming reproductive colonies composed of hundreds of pairs in late spring.