Comprehensive Study Notes on Wildlife Biology: Ichthyofauna and Aquatic Ecology
Course Introduction and Scope of Study
The course on Wildlife Biology (Biologia della Fauna Selvatica), led by Professor Stefano Fenoglio from the University of Turin (DBIOS), focuses on the biological, ecological, and management aspects of various animal groups. The program is divided into two primary sections: Ectothermic Wildlife and Homeothermic Wildlife. The ectothermic section specifically addresses the ichthyofauna of Piedmontese waters, emphasizing characteristics, recognition, management, and conservation. This segment includes practical activities such as visits to the provincial fish hatchery in Luserna and field sampling using electrofishing, as well as thematic seminars led by ichthyological technicians. The homeothermic section examines Alpine ungulates, such as Chamois and Deer, and Alpine Galliformes, focusing on their recognition and management through field census activities and specialized seminars.
Research and study are supported by the Alpine Stream Research Center (ALPSTREAM) and the Centro per lo Studio dei Fiumi Alpini, located within the Monviso Biosphere Reserve. The course aims to provide an exhaustive understanding of fish biology and ecology, highlighting their utility in biomonitoring and the conservation of endangered species within the Italian hydrographic network.
Evolutionary Classification and the Definition of Fish
Fishes represent the largest and most diverse group of vertebrates on the planet. Biologically, they are characterized as aquatic chordates that are ectothermic, meaning their body temperature is regulated by the external environment. They typically possess a hydrodynamic, streamlined body (corpo affusolato) designed for movement through water via fins (pinne) and breathe through specialized structures known as gills (branchie).
From a phylogenetic perspective, the history of "fish" involves several distinct classes. The Superclass Agnatha (Agnati) includes jawless vertebrates, such as the extinct Class Ostracodermi and the living Class Cyclostomi (Lampreys). The Gnathostomes (jawed vertebrates) include the Class Placodermi (extinct), the Class Chondrichthyes (cartilaginous fish like sharks and rays), and the Class Osteichthyes (bony fish). In the inland waters of Italy, the Osteichthyes are the dominant group, as cartilaginous fish rarely enter freshwater systems, except for specific species of sharks and rays in neotropical regions.
Italian Ichthyofaunal Diversity and Biogeographical Classification
The Italian freshwater fish fauna is composed of 87 species belonging to 57 genera, 24 families, and 13 orders. This community is categorized based on its origin and distribution. A "Native" or "Autochthonous" species (specie autoctona) is one that is natural to a specific geographical area, such as the Chub (cavedano), Bullhead (scazzone), or Loach (cobite). Conversely, an "Alien" or "Allochthonous" species (specie alloctona) is an exotic species introduced by humans where it was previously absent; examples include the Rainbow Trout (trota iridea), Largemouth Bass (persico trota), and Wels Catfish (siluro).
Other specific classifications include Parautoctone species, which are non-native species introduced and naturalized before 1500 AD, such as the Carp (carpa). Endemic species are restricted to a very specific and limited geographical area, such as the Barbus caninus, Lasca, or Savetta. Subendemic species are primarily distributed in a specific area but can also be found in neighboring regions, such as the Marble Trout (trota marmorata), Barbel (barbo), or Bleak (alborella). Currently, the Italian situation involves 52 native species (with approximately 60% being endemic) and 51 introduced species, totaling 131 species recorded in Italian running waters.
Biology and Ecology of the Agnathans (Lampreys)
Lampreys (Petromizonti) are primitive vertebrates characterized by an elongated, eel-like body and the absence of jaws. They possess seven gill openings on each side and a circular, suction-cup mouth reinforced by ring-shaped cartilage and numerous horny teeth (dentelli cornei). Their eyes have intrinsic movement but are limited to focusing. Lampreys are highly sensitive to pollution and serve as important indicator species. Historically, they exhibit anadromous or purely freshwater lifestyles.
In Italy, four species are recorded: Petromyzon marinus, Lampetra fluviatilis, Lampetra planeri, and Lethenteron zanandreai (the Po Brook Lamprey). The life cycle of these organisms involves a larval stage known as an ammocoete (ammoceti), which lives in sandy and muddy substrates as a filter feeder or detritivore. As adults, species like L. zanandreai migrate to upstream reaches with gravelly substrates for reproduction. Research, such as the Life Minnow project, focuses on the conservation of these endangered species, particularly in the tributaries of the upper Po River, where habitat suitability models indicate potential contractions in their range due to ecological changes. Habitat variables such as flow velocity ranging from to and depth variations (e.g., ) significantly influence their presence.
Morphological and Physiological Adaptations of Bony Fish
Bony fish (Osteichthyes) are divided into two main groups: Actinopterygii (ray-finned fish) and Sarcopterygii (lobe-finned fish). Their external morphology includes keys for recognition such as the general body shape, the position of the mouth (inferior, terminal, subterminal, or superior), the presence of barbels (barbigli), the lateral line (linea laterale), and the types of fins. Most bony fish possess a homocercal tail, characterized by symmetrical lobes, though some primitive groups exhibit heterocercal tails where the vertebral column extends into the upper lobe.
Respiration occurs via gills supported by branchial arches. The efficiency of gas exchange is maximized through a countercurrent flow mechanism, where blood flows in the opposite direction of water across the lamellae, maintaining a constant diffusion gradient for oxygen. Buoyancy is managed by the swim bladder (vescica natatoria). Physostomous fish, such as Cyprinids and Eels, maintain a connection (ductus pneumaticus) between the bladder and the digestive tract to swallow air. Physoclistous fish lack this connection and use a specialized "gas gland" and a "rete mirabile" (a complex network of capillaries) to fill or empty the bladder.
Osmoregulation is a critical physiological challenge. Freshwater fish are hyperosmotic to their environment, meaning they tend to lose ions and gain water across their permeable skin. To compensate, they do not drink water, possess "diluted" kidneys to expel excess water, and actively absorb ions through specialized cells in their gills. Marine fish face the opposite problem; they are hypoosmotic, tend to dehydrate, and must drink seawater while excreting excess salts through salt glands.
Trophic Levels and Body Coverings
Fish occupy highly diversified trophic roles within aquatic ecosystems. They are categorized as herbivores, omnivores, or carnivores. Carnivorous strategies include ambush predators (predatori all'agguato), like the Pike (Luccio), and pursuit predators (inseguitori), like the Marble Trout. Some species, such as the Grayling (Temolo), specialize as invertebrate predators on the water surface, while others, like the Barbel, feed along the river bottom.
Protection and hydrodynamics are provided by scales (scaglie) of dermal origin, which grow throughout the fish's life rather than being replaced. Common types include Ganoid scales (primitive), Cycloid scales (smooth, circular, found in Salmonids), and Ctenoid scales (serrated edges to improve hydrodynamics, found in Perciformes). Some species, such as the Bullhead, exhibit "naked" skin without scales.
Biogeography and Mediterranean Endemism
The Mediterranean Basin is an ecological hotspot, characterized by a unique combination of geological history, topography, and climate. During the Würm glaciation, the Mediterranean served as a primary refuge for many species. This history, combined with the Messinian salinity crisis (approximately 12 to 5 million years ago), led to high levels of endemism (64% of species). The Italian peninsula is divided into two main ichthyological districts: the Padano-Veneto district and the Tosco-Laziale district.
Biogeographical distribution is further defined by salt tolerance. Stenohaline species are intolerant of salinity variations and are restricted to freshwater. Euryhaline species can tolerate wide salinity ranges and may move between river basins via the sea. Human influence over millennia, from Roman aqueducts to modern trans-faunations and pollution, has significantly altered the natural distribution of Italian fish. Recent studies in areas like Calabria have provided the first detailed data on fish communities in southern Italy, revealing a mix of autochthonous species (e.g., Anguilla anguilla, Salaria fluviatilis) and various introduced species.
Reproductive Migrations and Fish Zonation
Many fish species exhibit migratory patterns for reproduction and growth. Catadromous species, most notably the European Eel (Anguilla anguilla), live and grow in freshwater but migrate to the sea (specifically the Sargasso Sea) to spawn. Their life cycle includes stages such as leptocephalus larvae, glass eels, elvers, yellow eels, and finally silver eels. Anadromous species, such as the Atlantic Salmon, Sturgeon (Acipenser sturio), and Shad (Cheppia), grow in the sea and return to freshwater to reproduce.
Within river systems, fish are distributed according to ecological zonation. This zonation is driven by current velocity, substrate granulometry, and oxygen levels. The typical progression from upstream to downstream is the Salmonid Zone (cold, oxygen-rich, rocky), followed by the Cyprinid Zone for lithophilous spawners (gravel substrate), the Cyprinid Zone for phytophilous spawners (vegetated, slower current), and finally the Mugilidae Zone in estuarine reaches.
Biology of the Salmonidae
The Salmonidae family includes iconic species such as the Brown Trout (Salmo trutta), Arctic Char (Salvelinus alpinus), and various introduced species. The Brown Trout exhibits immense diversity, with distinct Atlantic and Mediterranean lineages (e.g., Salmo ghigii, Salmo cettii). Mediterranean trout are often smaller (up to ) compared to Atlantic varieties, which can reach weights of .
The life cycle of a wild trout begins with eggs buried in gravel nests called "redds" (letti di frega), where they absorb oxygen through their shells. After hatching, they become alevins, obtaining nutrients from a yolk sac. They then develop into fry and later parr, characterized by dark oval markings called "parr marks" (macchie parr). As adults, they may remain resident in their home streams or migrate to lakes or the sea. Spawning typically occurs between November and February. A female weighing can produce approximately 1500 eggs.
Challenges in Management and Conservation: The Rainbow Trout
The Rainbow Trout (Oncorhynchus mykiss), native to North America, was introduced to Europe for aquaculture and restocking due to its rapid growth and resistance. While long considered unable to reproduce naturally in Italian waters, studies (such as those on the Lemme creek) have documented established, self-sustaining populations. Research shows that naturally hatched fry reach lengths of in approximately 36 days. The Gonadosomatic Index (GSI) peaked in spring months, confirming successful local spawning.
Contemporary conservation efforts, such as the European Life Minnow project, emphasize the protection of native biodiversity against threats like habitat alteration and the introduction of invasive species. Public outreach and education, including appearances on programs like "Newton" on Rai Play, underscore the importance of rivers as "fountains of life" and the necessity of maintaining their fragile ecological balance.