ZOOLOGY OF CHORDATES: STUDY GUIDE - Zakakharenko M.O. - 2015

CHAPTER 3. SUBPHYLUM GNATHOSTOMATA (JAWED VERTEBRATES)

3.5. Characteristics of Selected Bony Fish Representatives

Subclass Sarcopterygii (Lobe-finned Fishes). Scales are cosmoid or bony. The notochord persists throughout life and is surrounded by a dense connective-tissue, fibro-elastic sheath. Upper and lower arches are well developed, while rudimentary vertebral centra are occasionally visible in the caudal region. The cranium is amphistylic or autostylic. The Skull roof bones include a squamosal. The tail is heterocercal (in fossils) or diphycercal. Paired fins possess a fleshy lobe at the base and are biserial. The Heart features a conus arteriosus. The intestine contains a spiral valve and opens into a cloaca. One or two sacs, functioning as Lungs, branch off from the ventral side of the Esophagus. First found in Lower Devonian deposits.

Superorder Crossopterygimorpha (Crossopterygians). The neurocranium is divided into two parts: the olfactory and the proper braincase. The skull is amphistylic. Secondary jaws are well developed; Teeth are strong and sharp. The Skeleton of the paired fins has a shortened central axis and a well-developed basal element at the base. Freshwater predators that repeatedly invaded marine environments.

Order Coelacanthiformes. Representatives of this order evidently diverged from primitive rhipidistians. Choanae are absent. The tail is diphycercal, with an additional median lobe. Fins have robust yet relatively short bases and elongated lobes. The swim bladder is poorly developed. They inhabited freshwater bodies and invaded the seas during the Paleozoic. However, during the Triassic, they were displaced by actinopterygians. Coelacanth remains still occur in the Jurassic and Cretaceous, but have not been found in later strata. Consequently, they were considered an entirely extinct group.

In 1938, an unknown fish was caught off the coast of South Africa, which J.L.B. Smith identified as a coelacanth and named Latimeria chalumnae (Fig. 98).

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Fig. 98. Latimeria

It turned out that coelacanths inhabit the northern part of the Mozambique Channel (between Madagascar and Africa) at depths of up to 300 m, leading a benthic lifestyle. The population of Latimeria is small: just over a hundred cases of fish catches have been documented. The well-developed notochord features a thick, dense, and elastic fibrous sheath. The Brain occupies no more than one percent of the braincase volume, which is filled primarily with a fat-like substance. The swim bladder, similar to the lungs of lungfishes, originates from the ventral side of the esophagus; it is short, tube-like (5–8 cm long), and transitions into a fat-surrounded cord. The intestine possesses a spiral valve, and the heart has a conus arteriosus. In a sexually mature female weighing 78 kg, the right Ovary (the left is rudimentary) contained 19 eggs, 8–9 cm in diameter and weighing about 300 g each; they are ovoviviparous. Latimeria is a typical relict species; its survival to the present day in a restricted area of the World Ocean is the result of a chance combination of favorable conditions.

Superorder Dipneustomorpha (Lungfishes). Paleozoic lungfishes possessed a solid bony Structure or several separate bones in the neurocranium. In modern species, cartilaginous ossifications are underdeveloped. Internal nostrils (choanae) are present. The skull is autostylic. Teeth form powerful dental plates. The notochord persists throughout life. Upper and lower (hemal) arches are present, alongside vertebral centra in some fossil forms. The skeleton of the paired fins is of the biserial type. Evolution shows a posterior shift of the unpaired fins and their fusion with the caudal fin. Scales are cosmoid or bony. Modern species possess one or two lungs—outgrowths of the ventral side of the esophagus. There is an incipient division of the atrium and The formation of a Pulmonary Circulation loop. Lungfishes represent a lateral, specialized branch that diverged from primitive lobe-finned fishes as early as the Lower Devonian. They are divided into three orders; six extant species exhibit a relict distribution pattern.

Order Ceratodiformes (Australian lungfishes).

The neurocranium is almost entirely cartilaginous. Dermal bones are few. Secondary jaws are absent. Paired fins are well developed. They possessed only a single lung. Scales are bony and large.

Currently, only one species exists (Fig. 99) — the Australian lungfish, Neoceratodus forsteri (found in a few Water bodies in Western Australia).

Fig. 99. Australian lungfish

It reaches up to 1.5 m in length and over 10 kg in weight. It inhabits overgrown rivers with a slow current. Drought periods are weathered in pools remaining from the riverbed. Every 40–50 minutes, it surfaces and audibly ventilates its lungs. If the pool dries up completely, it dies. It feeds on invertebrates, although the gut usually contains plenty of finely pulverized plant remains. Eggs (up to 6–7 mm in diameter) are laid on aquatic plants. Larvae breathe primarily through gills. After the resorption of the yolk sac, they become more active, stay in open pool reaches, and feed on filamentous Algae. Pectoral fins appear on the 14th day after hatching. From this time, the lung begins to function. Pelvic fins form after 2.5 months. Australian lungfishes were intensively hunted for their tasty meat. Today, they are protected.

Order Lepidosireniformes. The neurocranium is almost entirely cartilaginous. Dermal bones are few. Secondary jaws are absent. Dental plates feature sharp ridges. Paired fins are tentacle-like; their skeleton consists solely of a segmented central axis. Small cycloid scales are deeply embedded in the Skin. Lungs are paired. Development proceeds with metamorphosis: larvae develop external skin gills that disappear once the lungs begin to function. Few fossil remnants have been discovered in the Permian horizons of the USA and the East European Platform. Currently, five species across two genera are known.

Four species of the genus Protopterus inhabit Central Africa (Fig. 100).

Fig. 100. Protopterus

The largest reaches 2 m in length, while the smallest is only 30 cm. They inhabit river reaches and temporary lakes. They lead a crepuscular and nocturnal lifestyle. They feed on diverse animal prey: Annelids, Mollusks, amphibians, and fish. During droughts, when the water level drops to 5–10 cm, the protopterus digs a burrow. The chamber for larger fish is located at a depth of up to half a meter. Due to the hardening of skin mucus, a dense cocoon forms around the fish (its wall thickness is only 0.05–0.06 mm); a thin tube forms at the upper part of the cocoon through which air reaches the HEAD. The fish remains in this state until the next rainy season, for about 6–9 months (over four years in experimental conditions).

During the rainy season, the soil gradually softens, water fills the air chamber, and the fish, breaking through the cocoon, pushes its head out to breathe air. Within a few hours, it leaves the burrow. Over time, urea is excreted outward via the gills and Kidneys.

Following estivation, the breeding season begins. In a burrow excavated by the male, the female lays up to 5,000 eggs measuring 3–4 mm in diameter. The larvae possess a large yolk sac and 4 pairs of feathery external gills. Throughout the incubation period and the first weeks of the larvae's life, the male stays near the nest and actively defends it. The larval stage lasts 3–4 weeks. The South American lungfish, Lepidosiren paradoxa, inhabits the Amazon basin (Fig. 101).

Fig. 101. Lepidosiren

It predominantly inhabits temporary water bodies, escaping drought by burrowing into the mud in the exact same manner as protopterids. However, the lepidosiren does not form a cocoon — the body

of the dormant fish is enveloped solely in mucus. The male also guards the eggs and fry. During this period, rich capillary-dense, branched cutaneous outgrowths 5-8 cm in length develop on its pelvic fins. It remains definitively unconfirmed whether these outgrowths assist in oxygenating the water within the nesting chamber or compensate for the inability to utilize pulmonary Respiration while inside the burrow.

Subclass Ray-finned fishes - Actinopterygii.

Infraclass Ganoidei - ganoidei.

Order Polypteriformes. This is an ancient group of fish (known since the Eocene), whose fossil ancestors have not yet been discovered (Fig. 102).

Fig. 102. Reedfish: calamoichthys (1) and Nile bichir (2)

Body lengths range from 30 cm to 1.2 m. The body is elongated, covered with rhombic ganoid scales. The head is flattened, with a pair of small barbels. The Mouth and teeth are large. The dorsal fin consists of several (6 - 18) small finlets, each featuring a large spine and several soft rays. The large pectoral fins possess fleshy lobes similar to those found in lobe-finned fish. The swim bladder is located beneath the digestive tract, performs a respiratory function, and consists of two chambers, one of which is connected to the Pharynx. A spiral valve is present in the intestine. The conus arteriosus is well developed. Lifespan is up to 12 years. They are found in freshwaters of tropical Africa, with the majority of species inhabiting the Zaire River basin. They can survive out of water for extended periods thanks to respiration via the swim bladder. However, at the same time, without access to atmospheric air, they perish within 2 - 3 hours. They reproduce during the rainy season in flooded meadows. Eggs are deposited on the substrate or aquatic vegetation. Development takes about 4 days; the larvae possess large external gills.

Order Lepisosteiformes - Lepisosteiformes (Fig. 103).

Fig. 103. Longnose gar

Lepisosteiformes are a species-poor order of ganoid fish (Holostei). Known since the Eocene. In ancient times, Lepisosteiformes were distributed across

Europe, India, and North America. Today, their range encompasses the water bodies of Central and North America, as well as Cuba. Sizes reach up to 3 m, with weights up to 150 kg. The body shape resembles that of pikes. The body is covered with rhombic ganoid scales, forming a sturdy armor capable of withstanding a shot from a speargun. The dorsal and anal fins are shifted far backward. The snout is elongated; the jaws resemble those of caimans in shape and bear A large number of large teeth. The upper jaw also bears nostrils. THE Vertebral Column is ossified, with vertebrae that are convex anteriorly and concave posteriorly. The swim bladder is cellular and connects to the pharynx, enabling the fish to breathe atmospheric air. The intestine features a spiral valve. The heart retains a conus arteriosus. Lifespan can reach several decades. They are freshwater fish, though they may enter brackish estuaries. In terms of lifestyle, members of this order resemble pikes — they are typical ambush predators. Sexual maturity is reached in the 3rd to 4th year of life. Spawning is seasonal and communal (1 - 4 males per female). The eggs are demersal, adhesive to the substrate, and toxic. The incubation period is about 3 days; the newly hatched larvae remain attached to the substrate for several more days. Juveniles initially feed on small invertebrates, switching to fish fry once they reach 4 cm in length.

Order Amiiformes - Amiiformes (Fig. 104)

Fig. 104. Bowfin

This order, along with the garpikes, is frequently combined into the group (superorder) of bony ganoids — Holostei. Two extant genera have survived to the present day. Bony ganoids are characterized by the presence of ganoid scales (reduced in bowfins) and a lesser degree of chondrocranium ossification. The caudal fin is weakly heterocercal. The swim bladder, with its cellular walls, serves as an accessory respiratory organ and opens on the DORSAL SIDE OF the anterior esophagus. The sole surviving modern species, the bowfin Amia calva, inhabits swampy, shallow water bodies of North America. The body is covered with cycloid scales. The vertebrae are amphicoelous. The heart retains a shortened conus arteriosus, while the intestine exhibits a somewhat reduced spiral valve. It is an active predator. Prior to spawning, the male bowfin builds a nest out of plant debris. The female deposits 20,000–70,000 eggs there. The fry attach to the walls of the nest using a sticky secretion produced by a gland located on the snout. The male guards the nest for several months. Its commercial value is insignificant.

Order Acipenseriformes - Acipenseriformes (Fig. 105).

Modern species retain many archaic structural features. The upper lobe of the heterocercal tail bears ganoid scales (fulcra); highly characteristic are bony plates known as scutes, formed from fused scales and arranged in five regular longitudinal rows along the body. A well-developed notochord encased in a dense sheath persists; vertebral bodies are absent, but cartilaginous neural and haemal arches are present. Over the cartilaginous braincase, an armor of numerous dermal bones has formed. In the skeleton of the paired fins, radial bones are well developed. In the upper part of the operculum, a rudimentary spiracle is sometimes retained. The heart features a developed conus arteriosus, and the intestine contains a spiral valve. Known from the Triassic, though they have never been numerous. Currently, 25 species across two families survive; they are found exclusively in the Northern Hemisphere.

Family Acipenseridae unites three genera comprising 23 species (Fig. 105).

Fig. 105. Acipenseriformes

1 - sturgeon; 2 - beluga; 3 - stellate sturgeon; 4 - sterlet; 5 — dwarf sturgeon

The largest dimensions are attained by the beluga - Huso huso, which inhabits the Black, Azov, and Caspian Seas as well as the eastern part of the Mediterranean Sea; it reproduces in rivers flowing into these seas at the age of 9-23 years, reaching a length of 1.5-2 m. Individual specimens live up to 100 years, attaining a length of 5.5 m and a mass exceeding 1.5 t.

The sturgeon genus Acipenser includes 16 species, 8 of which inhabit our waters. The most well-known are the Atlantic, Siberian, Amur, and North American sturgeons, as well as the stellate sturgeon (sevruga), sterlet (Fig. 105), and ship sturgeon. Among these, only the sterlet permanently inhabits rivers. The others are anadromous fish that spawn in rivers with pebble and rocky bottoms hundreds or thousands of kilometers from the river mouth. After spawning (which occurs annually or biennially), adult fish return to the sea. Some sturgeons live to be 30–60 years old, reaching lengths of 2.5 m and weights of 100–120 kg; the maximum length of the sterlet is 1–1.2 m, with a weight of up to 16 kg.

Many anadromous sturgeon species exhibit two distinct ecotypes: winter and spring races. Winter-run fish enter rivers in autumn, overwinter there, and migrate back to the sea in spring after spawning; spring-run fish enter rivers in spring, spawn in late spring or early summer, and immediately return to the sea. The existence of these two races allows for the sequential utilization of spawning grounds and food resources; additionally, winter populations more easily reach distant spawning grounds in the upper reaches of rivers. In the rivers flowing into the Aral Sea (Amu Darya and Syr Darya), three species of shovelnose sturgeons of the genus Pseudoscaphirhynchus reside.

The paddlefish family, Polyodontidae, is currently represented by two species: the American paddlefish (Polyodon spathula), which reaches 2 m in length and a weight of 75 kg, inhabiting the lakes and rivers of the Mississippi River basin.

Infraclass Teleostei — Teleost fishes; Order Anguilliformes — Eels; European eel Anguilla anguilla (Fig. 106)

Fig. 106. European eel

There are no subspecies. Previously, American and Japanese eels were considered subspecies of the European eel, but they are now classified as distinct species. From the sea, juvenile eels migrate into all European rivers, ranging from the Baltic and Barents seas down to the Black Sea. Eels are found in small numbers in the Black Sea, and individual specimens have been caught in the Danube, Dniester, Southern Bug, and Dnieper rivers. Their length typically ranges from 50 to 150 cm, with a maximum of up to 200 cm. Weight is normally up to 4–6 kg, although a specimen weighing 12.7 kg has been documented. They reproduce at great depths in the Sargasso Sea. The larvae (leptocephali) rise to the surface and are passively transported by the Gulf Stream to the shores of Europe, a journey that takes 2.5 to 3 years. In the Glass eel stage, they approach river mouths in May and migrate upstream. Eels spend a significant portion of their lives in fresh water. Their coloration varies depending on age and habitat. Two forms of eels are distinguished: sharp-headed and broad-headed. Sharp-headed eels are more commonly found in areas with small prey organisms. Smaller individuals feed on insect larvae, mollusks, worms, and crustaceans, whereas larger eels feed predominantly on fish (perch, ruffe, roach). They grow slowly, though under favorable conditions, weight gains of up to 500 g per year have been recorded. The feeding season lasts from April to November; they do not feed in winter, spending the cold months in hibernation. Eels live in rivers for 5 to 25 years before beginning their return migration to the sea. They are a valuable commercial species, caught in moderate quantities.

Order Clupeiformes — Herrings

Black Sea tyulka (sprat) Clupeonella cultriventris (Fig. 107)

Fig. 107. Black Sea tyulka

This species is found in the basins of the Black, Azov, and Caspian seas. C. cultriventris inhabits the Sea of Azov and the brackish areas of the Black Sea, entering the Don, the Kuban delta, the Dnieper, the Southern Bug, the Dniester, and the Danube. It has become a highly abundant species in almost all reservoirs. Its maximum lifespan is 6 years; it reaches lengths of up to 15 cm (usually 10 cm) and a weight of 22 g. It is a pelagic, euryhaline fish that occurs and reproduces both in the sea and its brackish zones, in rivers, and—in certain purely freshwater forms—in lakes and reservoirs. Its main diet consists of Copepoda and Cladocera, and less frequently rotifers, mollusk larvae, and fish. Spawning takes place from April to June. Larvae and fry inhabit shallow coastal waters. The tyulka is a schooling pelagic fish that does not approach the shoreline directly. It is one of the primary commercial fish species, with its populations steadily increasing in reservoirs. It frequently serves as prey for predatory fish.

Order Salmoniformes — Salmons; Suborder Esocoidei — Pikes; Family Esocidae — Pikes; Northern pike Esox lucius (Fig. 108)

Fig. 108. Northern pike

In Europe, it is widely distributed across the basins of the North, Baltic, Barents, White, Black, and Caspian seas. It reaches lengths of 150 cm and weights of 35 kg, with a maximum lifespan of 12–15 years. In rivers, it permanently inhabits the littoral zone, whereas in large lakes and reservoirs, it ventures into open pelagic waters. It is an obligate predator. During their first months of life, juveniles feed on zooplankton, switching to young fish—primarily cyprinids and percids—once they reach 4 cm in length. Adult pikes feed on mass fish species. Growth is most rapid in the delta regions of large rivers. Spawning occurs in early spring at a water Temperature of 3–6°C. Fecundity ranges from 3,000 to 233,000 eggs. Development takes 10–14 days. Spawning in shallow waters often leads to the drying out and destruction of eggs during sudden drops in floodwater levels, which reduces juvenile survival rates and depletes pike stocks. It is a major commercial species everywhere.

Order Cypriniformes — Cypriniforms; Family Cyprinidae — Carps.

Genus Abramis — Bream.

Blue bream Abramis ballerus (Fig. 109).

Fig. 109. Blue bream

Basins of the North, Baltic, Black, and Azov seas. It reaches an age of 9–10 years, a length of 45 cm, and a weight of 600 g. It inhabits freshwater bodies and can also be found in brackish waters. It is a typical lake-river pelagic fish that often forms schools and predominantly inhabits flow-through lakes. In rivers, it prefers slow-flowing areas. The blue bream's diet consists mainly of zooplankton, along with some benthic organisms and aquatic vegetation. In rivers, its growth is slow. Males reach sexual maturity at 3–4 years of age, and females a year later, at a length of 18–20 cm. Fecundity ranges from 4,000 to 52,000 eggs. Spawning occurs from late April to mid-June in flooded shallows at a depth of 30–80 cm. It is a commercial fish, though of low economic value.

Common bream Abramis brama (Fig. 110).

Fig. 110. Common bream

Found in rivers, lakes, and brackish areas of the Northern, Baltic, White, Aegean, Black, Azov, Caspian, and Aral seas. It lives up to 20 years, reaching a length of 75-80 cm and a weight of 6-9 kg, while average sizes are 25-45 cm and 0.5-1.5 kg, respectively. It prefers moderately flowing water bodies and lakes, and is a typical benthophage. Large bream may prey on juvenile fish. They are schooling fish. Sexual maturity is reached at 3-4 years in the south. Spawning occurs from late April to early June in the southern regions, and in May-June in the north. Fecundity ranges from 92,000 to 338,000 eggs. The eggs develop within 4-6 days. It forms two ecological forms: resident and semi-anadromous. The latter feeds in the sea and ascends to the lower reaches of rivers to spawn. It is a major species for freshwater fisheries and aquaculture.

Bighead carp - Aristichthys nobilis (Fig. 111).

Fig. 111. Bighead carp

A Chinese species widely acclimatized in the European part of the CIS and other countries as an aquaculture species in the thermal waters of thermal power plants and nuclear power plants. It is a large fish, up to 146 cm in length and weighing up to 32 kg. Its main food source is zooplankton, though the proportion of phytoplankton in its gut increases by autumn. It matures at 2-6 years of age. It spawns during periods of sharp water level rises, later than the silver carp, in late May. The eggs are demersal-pelagic and spawned in portions. In natural conditions, it hybridizes with the silver carp. It is a valuable commercial fish with higher meat quality than that of the silver carp, representing a promising species for acclimatization, pond, and thermal-water farming.

Silver carp - Hypophthalmichthys molitrix (Fig. 112).

Fig. 112. Silver carp

Introduced from the Amur River and northern China, it has been widely distributed in pond farms across all lowland water bodies. However, self-sustaining populations have established only in the middle reaches of the Amu Darya and Syr Darya. In other water bodies, populations can only be maintained through periodic stocking from fish farms. It is a large, schooling pelagic fish, occasionally exceeding 1 m in length and 40 kg in body weight. Sexual maturity is reached at 3-4 years. Spawning occurs when water temperatures reach 18-20°C, coinciding with a sharp rise in river water levels in May-June. In natural conditions, eggs are released in fast-flowing river currents with eddies. The eggs are pelagic; upon contact with water, they swell, increase in size, and develop as they drift downstream. If they enter stagnant water, the eggs sink and die. A river stretch of 100 km or more with such current is required for egg development. Fecundity is high—up to 3 million eggs in large brood fish weighing over 20 kg. It feeds on phytoplankton.

Grass carp (Ctenopharyngodon idella) (Fig. 113).

Fig. 113. Grass carp

The grass carp can grow over a meter long and reach a weight of several dozen kilograms. Individuals with a body length of up to 1.22 m have been recorded, with such giants weighing over 30-35 kg. It features an elongated body that is slightly compressed laterally. All fins of the grass carp are distinctively colored. The head of the grass carp—another name for this species—has a specific appearance, appearing quite small relative to its massive body. The fish has a robust yet streamlined torso. The dorsal and caudal fins are darker in tone compared to the ventral and anal fins. The back of the grass carp has a greenish tint, while the belly casts a golden sheen. Its scales are very large, showing a golden hue on the sides with dark-rimmed edges. Experts have determined that the highest commercial yield from grass carp cultivation is achieved in southern water bodies located south of the 45th parallel north. This is because the grass carp cannot tolerate low water temperatures and ceases reproduction. Nevertheless, cultivating grass carp in northern regions is feasible in the warm waters of thermal and nuclear power plants. From artificial reservoirs, the grass carp inevitably penetrates natural water bodies. Its extremely high popularity is largely due to its diet. Although herbivorous, fry feed on microorganisms, earning the species the nickname of a true "aquatic cow". Higher aquatic vegetation begins to enter the grass carp's diet when it reaches one year of age, at a body length of just three centimeters. Later on, the grass carp consumes both aquatic plants and terrestrial plants that accidentally fall into rivers, showing a preference for young and soft vegetation.

Genus Bleaks - Alburnus.

Bleak - Alburnus alburnus (Fig. 114).

Fig. 114. Bleak

A small fish reaching a maximum length of 20 cm, a weight of 60 g, and an age of 10-12 years, though typical sizes in catches are 19-24 cm with a weight of 10-12 g. It inhabits rivers, lakes, flowing ponds, and reservoirs, and is also found in the brackish waters of river mouths and bays. It forms schools in the upper water layer. Adult fish feed on plankton, airborne insects, and their aquatic larvae, occasionally consuming eggs (both their own and those of other fish), larvae, and small fish fry. Sexual maturity is attained in the 3rd year of life at a length of 7-8 cm. Spawning takes place in May, June, and early July at water temperatures no lower than 15-16°C. Most females deposit eggs in three portions (some in four to six). Spawning grounds are usually located at depths ranging from 7 to 50 cm. Total fecundity can range from 3,000 to 10,500 eggs. The juveniles feed on microscopic algae and small zooplankton. Widely abundant everywhere, it is a minor commercial species, primarily targeted by amateur anglers. Its scales were historically used to manufacture artificial pearls.

Genus Asp - Aspius.

Asp - Aspius aspius (Fig. 115).

Fig. 115. Asp

Three subspecies are distinguished. In Europe, the nominative subspecies A. aspius aspius is the common asp. It is widely distributed in Central Europe within the basins of the North, Baltic, and Black seas, and occurs in all rivers of the Black Sea basin (Danube, Dniester, Dnieper, Bug, Don, Kuban). River populations do not reach large sizes. The migratory form is larger, growing up to 80 cm in length and weighing 4-5 kg, with catches typically dominated by individuals 60 cm long and weighing 2.5 kg. The maximum lifespan is 9-10 years in northern populations and 5-6 years in southern ones. A pelagic predator, it inhabits river channel areas and reservoir pools in the upper and middle water layers. It leads a solitary lifestyle, forming small schools only during the spring spawning period and when settling into wintering pits in autumn. It feeds on planktonic organisms and the fry of various fish species. In early stages, juveniles consume small crustaceans (Copepoda and Cladocera), as well as surfacing larvae and pupae of chironomids and other insects. At a length of 5-9 cm in August-September, the asp begins feeding on the fry of white bream, silver bream, bleak, sabrecarp, and common carp. In northern populations, it reaches a length of 40-50 cm only at the age of 10, whereas in southern ones, it does so at 6 years. Fecundity in the Azov-Black Sea basin is 40,000-200,000 eggs. Spawning lasts for 2 weeks in spring (April-May) at water temperatures ranging from 4-5 to 11-12°C. Once the larvae reach 7 mm in size, they are carried away into floodplain water systems where they forage. It is a secondary commercial fish species.

Genus White Bream - Blicca.

White bream - Blicca bjoerkna (Fig. 116).

Fig. 116. White bream

Sometimes this species is included in the genus Abramis, but it is more often considered valid based on Anatomical Features. It is widely distributed in Europe east of the Pyrenees and north of the Alps and the Balkans. It inhabits rivers and lakes in the basins of the North, Baltic, Black, Azov, and Caspian Seas. Living up to 15 years, it reaches a length of 35 cm and a mass of 1.2 kg, though typically it grows up to 25–30 cm and 0.5 kg. Like the common bream, THE WHITE BREAM prefers water bodies with slow or no current, well-developed vegetation, and a muddy or clayey bottom. It is a thermophilic species inhabiting waters where summer temperatures do not drop below 16–17°C. A sluggish fish, it tends to stay in one place for long periods, generally favoring well-warmed biotopes such as shallow areas with dense aquatic vegetation. In spring and autumn, these fish form large schools or dense aggregations. The diet of adult fish depends on the type of water body; silver bream feed primarily on chironomid larvae and mollusks, along with frequent intake of algae and detritus. Aerial insects and higher vegetation make up a minor portion of their diet. Sexual maturity is reached at the age of 3–4 years at a length of 11–15 cm. Females release eggs in 2–3 portions with an interval of 10–15 days. Spawning occurs at night, with a fecundity ranging from 11 to 109 thousand eggs. Egg development takes 4–6 days. Until the yolk sac is absorbed, the larvae attach to aquatic vegetation. Juveniles initially feed on phyto- and zooplankton. It is a commercial fish of minor value.

Genus Crucian Carps – Carassius.

Prussian carp (Carassius gibelio) (Fig. 117).

Fig. 117. Prussian carp

A species with a vast modern distribution spanning Eurasia and America. The native range of the Chinese crucian carp includes China, Japan, and the islands of Taiwan and Hainan. High-bodied and low-bodied forms are distinguished depending on the trophic Base of the water body. Due to artificial breeding, it has spread worldwide. It lives up to 14–15 years, typically 7–10 years, reaching a length of 45 cm and a mass of over 1 kg, though usually not exceeding 20 cm and 350 g. Compared to the crucian carp, this species is more closely associated with large lakes and is also found in major rivers. It feeds on plankton, detritus, algae, insect larvae, worms, and other invertebrates. Growing faster than the common crucian carp, it reaches 45 cm in length and 1 kg in mass. Sexual maturity is attained at the age of 2–4 years, with a fecundity ranging from 30 to 400 thousand eggs. Spawning is intermittent, usually occurring in May. Populations of this species frequently consist exclusively of females that spawn with males of other cyprinid species (such as common carp, crucian carp, or tench). The spermatozoon penetrates the egg Cell without fertilizing it, merely stimulating embryonic development, which results in all-female progeny (gynogenesis). The Prussian carp occasionally experiences sharp population booms. It is a valuable target for fisheries and aquaculture. The Chinese crucian carp and its varieties are popular in ornamental aquaculture, with over a hundred breeds of goldfish recognized. These include the comet, wakin, shubunkin, veiltail, demekin, ranchu, lionhead, oranda, telescope, and others. Several color variations exist, including red, silver, and black. Various combinations of these traits and colorations yield numerous distinct forms of goldfish, which is believed to boast more breeds than any other domestic animal. Goldfish can live up to 35–40 years.

Crucian carp or golden crucian carp – C. carassius (Fig. 118).

Fig. 118. Crucian carp

High-bodied and low-bodied forms are distinguished depending on the habitat. It has a wide distribution across Europe and Siberia, living up to 10–12 years. It reaches a length of 50 cm and a mass of 5 kg, though typical sizes in catches range from 9 to 24 cm with a mass of up to 600 g.

It inhabits lakes, river floodplains, and ponds, showing greater tolerance to oxygen depletion compared to the Prussian carp. It lives in swampy, overgrown waters and floodplain lakes, while being rare in rivers, where it keeps to areas with a sluggish current. It tolerates freezing and temporary drying of water bodies well by burying deep into the silt. It feeds on chironomid larvae (bloodworms) and other insects, small mollusks, worms, algae, and detritus. Under unfavorable conditions, it often stuns or degenerates, forming a stunted dwarf variety. Sexual maturity occurs in the 4th to 5th year of life. It is a valuable commercial and aquaculture species.

Fig. 119. Nase.

The nase inhabits rivers of the Northern, Baltic, Black, and Aegean Sea basins, though it is absent from the rivers of Crimea. It generally lives for no more than 10 years, reaching a length of 40 cm and a mass of 1.6 kg, with typical dimensions not exceeding 25–30 cm and 0.3–0.4 kg. A typical rheophile, it cannot tolerate standing water and leads a highly active, schooling lifestyle. It stays in the current within river floodplains, close to the bottom. Its primary food source consists of microalgae coating the stones on the bottom of the water body. It also consumes aquatic insect larvae, eggs spawned by other fish, and in summer, earthworms washed from the banks by rain. Spawning takes place in April at a water temperature no lower than 6–8°C, with a fecundity of 1.5–12 thousand eggs. Egg development takes 2 weeks. It is listed among rare fish species.

Genus Carps – Cyprinus.

Common carp – C. carpio (Fig. 120).

Fig. 120. Common carp (sazan)

The common carp and European wild carp currently inhabit fresh and brackish waters of the basins of the North, Baltic, Mediterranean, Black, Azov, Caspian, and Aral Seas. The Danube basin is believed to be the ancestral region from which the common carp spread. Due to artificial stocking, its range has expanded in Asia beyond its native limits. It is present in Kamchatka, Sakhalin, and Lake Baikal, and in the Amur basin, it is known from Lake Buir Nur and the Argun River. It is common in lakes and lower river reaches, with a maximum lifespan of 30 years. It can reach lengths of 100 cm or more and weights up to 16–32 kg. The average length in catches is 35–55 cm, with a mass of 1–3 kg. While primarily a freshwater fish, it also occurs in brackish waters, where it forms semi-anadromous ecotypes. Sexual maturity is reached at 3–5 years of age at a length exceeding 30 cm. Eggs are deposited on soft vegetation at shallow depths (up to 0.5 m). Fecundity ranges from 96 thousand to 1.8 million eggs. It is a valuable large commercial fish and an important species for pond aquaculture.

Fig. 121. Gudgeon

A widely distributed Eurasian species with a disjunct range, found from Portugal to the Amur basin and the rivers of the Sea of Japan.

It reaches an age of 8–10 years, a length of 20 cm, and a mass of 226 g, though typical sizes do not exceed 12–15 cm. Females are larger than males. It inhabits both lakes and slow-flowing lower river reaches, as well as the upper stretches of fast-flowing rivers, keeping close to the bottom. In summer, it forms small aggregations in shallow waters, moving to deeper areas in winter. It feeds on invertebrates and may consume the eggs of other fish. Sexual maturity is attained at a length of 8 cm. Reproduction occurs at night during spring and early summer (April–June). Spawning is intermittent, taking place in the current in shallow areas with a stony-sandy bottom. Fecundity ranges from 1 to 3 thousand eggs, and embryonic development takes about 8 days. Larvae and fry feed on plankton and other microscopic invertebrates. Lifespan rarely exceeds 3 years.

Genus Leucaspius - Dace.

Moderlieschen or sabre carp - L. delimatus (Fig. 122).

Fig. 122. Moderlieschen

Inhabits Europe from the Rhine to the Volga basin, as well as the lower reaches of the Kura and Kumbashinka rivers. Lives up to 5 years. Reaches a length of 8-9 cm, most commonly 6 cm. Inhabits ponds, small lakes, and dammed sections of small rivers. Forms small schools. During the day, it swims near the surface, feeding on aerial insects. At nightfall, it descends to the depths to feed on zooplankton. Reaches sexual maturity at 2 years of age at a length of about 4 cm. Spawning is portioned. The larvae hatching from the eggs are 5 mm long and immediately capable of swimming and foraging. Due to its very small size, the moderlieschen has no commercial value.

Genus Squalius - Chub

Chub L. cephalus (Fig. 123).

Fig. 123. Chub

Widespread throughout Europe, Asia Minor, the Caucasus, and Transcaucasia, extending to the Tigris and Euphrates river basins. Lives up to 15-18 years, reaching a length of 80 cm and a mass of 6-8 kg. Usual sizes are 30-40 cm with a mass of up to 1 kg. A typical river fish. Prefers relatively small, fast-flowing rivers with clean, cold water and abundant springs. In summer, it feeds on insects falling into the water, crustaceans, worms, and filamentous algae. In autumn, it consumes mice crossing the river, frogs, gudgeons, and other small fish. Reaches sexual maturity in its 3rd-4th year of life at a body length of about 20 cm. Spawns in spring, from late April to late May. Spawning is portioned. Migrates upstream for reproduction. Widespread and locally abundant, but has no commercial significance. Flow regulation and river pollution are the main causes of its population decline in recent years.

Ide, silver orfe L. idus (Fig. 124).

Fig. 124. Ide

Distributed in the rivers of the Black Sea basin from the Danube to the Kuban. Lives up to 15-20 years. Reaches a length of 1 m and a mass of 6-8 kg, though usual sizes are 30-50 cm with a mass of about 1 kg. Inhabits rivers and lakes. Prefers deep backwaters with slow currents, deep holes and eddies, and areas with clayey and silty bottoms. A schooling fish. Feeds on insects falling into the water, river crayfish during molting, earthworms, insect larvae, small mollusks, and fish. Migrates upstream into tributaries to reproduce. From lakes, it ascends into inflowing rivers for spawning. Reaches sexual maturity at 4 years of age. Spawning occurs In the second half of April at a water temperature of 5-7°C. Spawning lasts for 2-3 days. A fairly abundant commercial species across many parts of its range.

Genus Pelecus - Razorfish (Sabrecarp) - P. cultratus (Fig. 125).

Fig. 125. Razorfish

In the Black Sea basin, it populates the Danube, as well as the Dniester, Southern Bug, Dnieper, Don, and Kuban. Reaches a maximum length of 60 cm with a weight of 2 kg. In the early 20th century, individuals weighing up to 3.5 kg were caught in the Dnieper delta. Maximum lifespan is 9 years, and up to 12-13 years in reservoirs. Average sizes in catches are 30-40 cm and 300-400 g. Inhabits rivers, lakes, and reservoirs, and enters the sea. Forms resident and migratory forms. A pelagic fish, living in the water column down to a depth of 30 m. At 5 years of age, the razorfish reaches a length of 23-27 cm. Resident river populations spawn in riverbeds in the surface water layers over currents. In reservoirs, the razorfish spawns in the water column over hard bottoms. A valuable commercial fish, though it constitutes an insignificant proportion of commercial catches in most water bodies. Genus Rutilus - Roach.

Roach - R. rutilus (Fig. 126).

Fig. 126. Roach

Distributed in Europe, east of the Pyrenees. Absent in Crimea. Reaches a length of 36 cm and a mass of 2 kg. Usual sizes in catches are 16-19 cm with a mass of 100-300 g. Life span is up to 10 years. Prefers lakes. In rivers, it selects areas with weak currents, overgrown with reeds and other vegetation. Feeds on filamentous algae, though adults can also consume animal food (crustaceans, mollusk eggs, insect larvae, worms, fish eggs, and fry). Reaches sexual maturity in its 3rd-5th year of life at a length of over 12 cm. Spawning is portioned, taking place from April to June. Widespread and locally abundant, but a low-value commercial species.

Genus Scardinius - Rudd

Common rudd - Scardinius erythrophthalmus (Fig. 127).

Fig. 127. Common rudd

Widely distributed in the water bodies of Europe (excluding the southern Caspian Sea and rivers flowing into the Arctic Ocean), Central and Middle Asia. Introduced to Ireland, Morocco, Madagascar, Tunisia, New Zealand, Canada, and Spain. In New Zealand and Canada, it is considered a pest fish that displaces native species. Body length up to 36 cm, weight up to 400 - 500 g, occasionally up to 2 kg. The body is deep, laterally compressed, with relatively large scales. The head is small, the mouth is superior and oblique, and teeth are arranged in two rows. The dorsal fin is shifted markedly backward. The back is dark brown with a greenish tint, the sides are yellowish-golden, and the belly is silvery. The dorsal and pectoral fins are grey with red tips, while all other fins are bright red. The eyes are yellow. It feeds on aquatic plants, particularly filamentous algae, the eggs of mollusks and other fish species, various invertebrates (worms, larvae, as well as adult insects falling onto the water surface); adults also consume young fish. Sexual maturity is reached at the age of 4 - 5 years with a body length of at least 12 cm. Spawning occurs in late May or early June when the water warms up above 15 °C. Eggs are deposited on aquatic vegetation.

Genus Tenches - Tinca.

Tench T. tinca (Fig. 128).

Fig. 128. Tench

Inhabits rivers and lakes of the Baltic, Black, and Caspian Sea basins. Absent in Crimea. It reaches a length of 63 cm and a mass of 7.5 kg (typically ~30 cm with a mass of 1.5 kg). Lifespan is up to 10 years or more. Adults feed on aquatic insects, their larvae, small mollusks, and crustaceans. Widely targeted by commercial and recreational fisheries.

Family Loaches - Cobitidae.

Genus Spined loaches - Cobitis.

Spined loach - C. taenia (Fig. 129).

Fig. 129. Spined loach

Inhabits water bodies of the Baltic, North, Mediterranean, Black, and Caspian Sea basins. Reaches a length of 13.5 cm and a mass of 10 g. Found almost everywhere in flowing waters, tributaries, river bays and backwaters, lakes, reservoirs, and ponds. Prefers clean rivers with hard bottoms, easily burrowing into sandy substrate. It typically hides under stones or beneath clumps of filamentous algae and aquatic moss, where it sometimes hangs in a peculiarly curved position. It leads a rather secretive lifestyle, occurring singly or in groups of 2-3 specimens. Feeds on various benthic organisms. Has no commercial value.

Genus Weatherfish - Misgurnus.

Weatherfish M. fossilis (Fig. 130).

Fig. 130. Weatherfish

Reaches a length of 25-30 cm, though average sizes are around 23 cm with a mass of 140 g. Lifespan is 6-7 years. Prefers marshy, sluggish, or standing waters. In rivers, it favors muddy areas overgrown with dense aquatic vegetation, often living in channels, bays, or oxbow lakes. It survives even in marshy lakes and ditches devoid of other fish, including crucian carp. Highly tolerant of low dissolved oxygen concentrations in water, facilitated by accessory intestinal respiration. If a water body dries up completely, the weatherfish burrows into damp mud and endures unfavorable conditions in a state close to hibernation. The weatherfish is sedentary. It feeds on insect larvae (especially chironomids), crustaceans, worms, small mollusks, as well as detritus and, to some extent, benthic vegetation. Growth is slow. Spawns in spring and summer. Has no commercial value.

Order Siluriformes. Family Siluridae.

Wels catfish S. glanis (Fig. 131).

Fig. 131. Wels catfish

Particularly abundant in delta regions of large rivers (Volga, Don, Dnieper) and in reservoirs with slowed flow. Rare in river upper reaches. Wels catfish reaching up to 5 m in length and 300 kg in mass have been recorded. Currently, specimens are rarely larger than 2.5 m in length and 150 kg in mass at an age of up to 30 years, while average sizes in most water bodies are 70-150 cm with a mass of 5-50 kg at an age of up to 15 years. They overwinter in large aggregations in deep depressions, ceasing to feed until spring. They feed mainly at dusk, using barbels and their entire skin to detect water vibrations when searching for prey. Instances of wels catfish attacking waterfowl and mammals (even dogs crossing a river) have been documented. Prior to spawning, the male builds a nest at a depth of 30-70 cm, shaped as a rounded, flat depression with walls made of vegetation. A valuable commercial species.

Order Perciformes. This is the largest order of teleost fishes, comprising over 6,500 species across 140-160 families. Representatives of the order inhabit both fresh and marine waters, with species diversity being particularly high in the tropics. Sizes range from 1-2 cm in length and 10-30 mg in mass to 5 m and 700-900 kg.

Suborder Percoidei. Family Percidae. Genus Perca.

European perch – P. fluviatilis (Fig. 132).

Fig. 132. Perch

Widespread in Europe (excluding Spain, Portugal, and northern Scandinavia). In the second half of the 19th century, European perch were transported from Great Britain to the waters of Australia, Tasmania, and New Zealand, where they successfully established populations. The largest specimens reach lengths of up to 40 cm and weights exceeding 2 kg (a catch of a 55 cm long perch has been documented). Perch reach sexual maturity early: males at 1–2 years, and females at 3–4 years. Depending on their size, females spawn from 12,000 to 300,000, and occasionally even 900,000 eggs. Spawning occurs at water temperatures ranging from 1 to 15 °C. Eggs are deposited on last year's vegetation, snags, roots, willow branches, and sometimes even directly on the substrate. During their first year of life, small river perch inhabit coastal shallows, while those in lakes and reservoirs exhibit high ecological plasticity in choosing food sources and habitats. Some act as true planktivores, feeding in the pelagic zone, whereas others stay within coastal vegetation, feeding on invertebrates or acting as predators. Perch may transition to a predatory diet at a length of 2–4 cm, but typically become apex predators upon reaching a length of over 10 cm. They feed on small fish, the juveniles of larger fish, and even conspecifics. Producing 1 kg of perch body mass requires consuming 5 kg of live-weight forage fish.

Genus Pikeperches – Sander.

Zander – Sander lucioperca (Fig. 133).

Fig. 133. Zander

An important commercial and sport fishing species. Total dorsal fin rays: 13–20; soft dorsal rays: 18–24; anal rays: 2–3; soft anal rays: 10–14; vertebrae: 45–47. The anterior part of the upper jaw bears 1–2 canine teeth; the second dorsal fin has 18–22/2 branched rays, and the lateral line contains 80–97 scales. Widespread in the freshwaters of Eastern Europe and Asia, found in the river basins of the Black and Azov Seas, as well as in lakes and brackish estuarine areas. Recorded as an introduced species in Western Europe. Quite sensitive to dissolved oxygen concentration and suspended solids, which is why it is absent from silted water bodies. During the warm season, it inhabits depths of 2–5 m. In winter, it gathers in deep river holes, often alongside cyprinids (such as bream, carp, etc.). The zander is a typical apex predator. It feeds on fish, while smaller individuals also consume aquatic invertebrates. Its diet is dominated by slender-bodied fish. Gobies, gudgeons, bleak, and tyulka herring make up the core of its diet. For spawning, it selects shallow areas—typically with submerged bushes, trees, or large debris on the bottom—at depths ranging from half a meter to one and a half meters. The eggs are small and yellowish. Under favorable feeding conditions, zanders can reach a mass of up to 500–800 grams by their second year of life. However, they usually spawn for the first time in their 3rd or 4th year.

Genus Ruffes – Gymnocephalus.

Eurasian ruffe – Gymnocephalus cernua (Fig. 134).

Fig. 134. Eurasian ruffe

The Eurasian ruffe is the most widely distributed of the five ruffe species—its natural range includes northern and eastern France, eastern England, the Baltic Sea basin rivers, Central and Eastern Europe, and northern Asia. In Ukraine, the ruffe is found everywhere except the Crimea. Ruffes are highly adaptable, typically schooling fish that thrive in a wide range of environmental conditions. Sexual maturity is usually reached at 2–3 years of age, at a body length of about 11–12 cm; in some water bodies, ruffes may begin reproducing as early as one year old, which researchers attribute to warmer average water temperatures or high early-life mortality rates within those populations. This species deposits its eggs on A wide variety of substrates at depths of 3 meters or less, without providing parental care. Spawning takes place from mid-April to June across a fairly wide temperature range, with spawning documented at both 6 °C and 18 °C. The pH tolerance range for normal ruffe egg development is among the widest recorded for fishes studied for this parameter, spanning between 6.5 and 10.5.

Donets ruffe – Gymnocephalus acerinus (Fig. 135).

Fig. 135. Donets ruffe

It differs from the Eurasian ruffe by its longer snout, smaller scales, head shape, and body proportions. It is found in the Black and Azov Sea basins: in the Dniester, Southern Bug, Dnieper, Don, and Kuban rivers, and in

their tributaries in areas with fairly rapid currents. The body coloration is yellowish, the upper back is predominantly olive-green, the belly is silvery-white, and the sides and dorsal fin bear several rows of dark spots, giving the fish a highly mottled appearance. The Donets ruffe is somewhat larger than the common ruffe, with a typical length of 8–13 cm; individuals measuring 16–18 cm are quite common (with a record of 20.3 cm). Spawning occurs in spring, earlier than other members of the genus, in fast-flowing rivers over clean sandy bottoms. The eggs are demersal and adhesive, containing large oil droplets. Adult Donets ruffes, like other fishes lacking a swim bladder, are benthic dwellers. They feed on bottom-dwelling worms, small mollusks, aquatic insects, and mosquito larvae. They are active during the evening and night. Donets ruffes winter in schools within deep, silted river holes.

Family Sunfishes – Centrarchidae.

Genus – Sunfishes – Lepomis.

Pumpkinseed – Lepomis gibbosus (Fig. 136).

Fig. 136. Pumpkinseed sunfish

Widespread in the rivers and lakes of the USA and Canada, certain species have spread to water bodies worldwide. The opercula of fish in this genus are scaled. The maximum size of this fish reaches 40 cm, though under Ukrainian conditions it grows up to 20 cm, with a weight of up to 0.6 kg. The body is brightly colored and deep. The back is greenish, the flanks feature orange spots and dark vertical bars, and the belly is yellow. The body and head are covered with numerous green and red spots, the Lips are blue, and the fins are yellow. Males possess distinctive "earflaps"—black with a red spot—which are reddish-yellow in females. The species has been successfully acclimated in Europe and Asia; in Ukraine, its range encompasses the lower reaches of rivers flowing into the Black Sea, though nowadays it is frequently caught in the Dnieper River, the Kakhovka Reservoir, and in recent years even near Kyiv. It inhabits shallow waters among aquatic vegetation. It is a rather sluggish fish. It feeds on various invertebrates and does not shy away from fish fry or fish eggs. Sexual maturity is reached at approximately 2 years of age. Spawning is protracted and occurs in batches from late May to late July. The species has no commercial value and can be somewhat detrimental by preying on the fry of commercially valuable fish.

Suborder Gobioidei

Family Eleotridae, or sleepers

Genus Perccottus

Amur sleeper, rotan — Perccottus glenii (Fig. 137).

Fig. 137. Amur sleeper (rotan)

The Amur sleeper, also known as the Chinese sleeper or rotan, is a freshwater fish belonging to the monotypic genus Perccottus within the family Odontobutidae (sleepers). It is sometimes confused with the round goby, but these are entirely different fish species. Growing up to 25 cm in length, it has an elongated, somewhat cylindrical body that is thick near the head and laterally compressed toward the tail. The head is quite large, featuring a wide mouth with a protruding lower jaw and fleshy lips. The teeth are well-developed, arranged in multiple rows, and curved. The eyes are large. The body and most of the head are covered with relatively large scales. Its native range encompasses the water bodies of the Russian Far East. In 1912, it was introduced to Europe as an aquarium fish and subsequently released into natural water bodies, where it successfully adapted to new environmental conditions and began expanding its range. Today, it is found across a significant portion of European Russia, Siberia, Kazakhstan, and Uzbekistan, and has spread to several European countries, notably Poland and the Danube River basin. Currently, the westernmost point of its range is Bavaria, where it has been recorded in ponds within the Danube basin. In Ukraine, it has been present since the late 1970s, when it was accidentally introduced into the waters of western Ukraine alongside phytophagous fish species. Later, it was recorded in the Latorica River basin in Transcarpathia. In recent years, it has expanded throughout the upper Dniester, Prut, and Dnieper river basins. It has also been documented in the lower Danube near the town of Vylkove, and its presence has been confirmed in the Southern Bug basin, specifically in the Hirskyi Tikych River. The Amur sleeper is characterized by remarkable hardiness and high ecological plasticity. It can inhabit water bodies that freeze solid or dry up completely, tolerate low oxygen levels, and even survive in swamps. Under adverse conditions, it burrows into the silt. It tends to dwell among dense aquatic vegetation. The Amur sleeper is a voracious predator, attacking any prey smaller than itself, including conspecifics (cannibalism). It may continue to prey on fish even with a full Stomach, and it also feeds on fish eggs and carrion. The lifespan of the Amur sleeper in European waters is 8–10 years. Sexual maturity is reached at 3–4 years of age at a body length of 5–7 cm. Spawning begins in May when the water temperature warms up to 15°C. Spawning occurs near the banks, where the eggs are deposited on aquatic vegetation or other hard substrates.

Fecundity reaches up to 4,500 eggs. During incubation, the male guards the deposited eggs, driving away intruders and providing aeration by fanning them with his pectoral fins.

Family Gobiidae

Genus Neogobius

Monkey goby, or sand goby — Neogobius fluviatilis

(Fig. 138).

Fig. 138. Monkey goby

A fish of the family Gobiidae within the order Perciformes, and a Ponto-Caspian relict. In Ukraine, it is of commercial importance, particularly in the Sea of Azov and the Dnieper-Bug Estuary. During the spawning season, males turn entirely jet-black with yellowish margins on their unpaired fins. They reach a length of 7–10 cm (occasionally up to 18–20 cm) and weigh about 50 g. The native range of this species covers the fresh and brackish waters of the Black Sea and Sea of Marmara basins. In recent years, the species has been recorded as an introduced alien in Western European countries. It inhabits sandy bottoms in shallow coastal areas with flowing water. For the winter, it migrates to deeper waters, secretes a thick layer of mucus, ceases feeding, and remains largely immobile. It lives for 5–7 years. The monkey goby is a typical malacophage, though mollusks play a smaller role in its diet compared to the round goby. Sexual maturity is attained in the second year of life when the fish reaches a length of 10 cm. Spawning takes place from late April to early June at water temperatures of 10–13°C, typically in shallow coastal waters. Females lay between 700 and 2,800 greenish eggs (at least 2.5 mm in diameter) inside cavities that males excavate in the sand or mud beneath stones. The eggs develop into larvae within 2–3 weeks at a water temperature of 15–16°C, and free-swimming fry emerge 5 days later. In their first year of life, the fish reach 3–5 cm in length, 6–10 cm in the second year, and 12–20 cm by the fourth year.

Round goby — Neogobius melanostomus (Fig. 139).

Fig. 139. Round goby

A small-sized benthic fish. Round gobies grow up to 25 cm in length, with males being slightly larger than females. Young-of-the-year are grey, while adults display grey, black, brown, and olive colorations. During the spawning season, adult males turn intensely black with a distinct white margin on their unpaired fins. The invasion METABOLISM/13.html">History of the round goby dates back to the 1980s, when this species, along with five other goby species, was first recorded in the middle Dnieper near Kyiv. Adult round gobies are typical malacophages, feeding primarily on mollusks. Females live for 4–5 years, whereas the majority of males die shortly after their first spawning season. Some round gobies reach sexual maturity as early as their second year of life, sometimes at a body length of only about 5 cm. By the age of three, all individuals are sexually mature. Spawning occurs from April to September.

Genus Mesogobius

Toad goby — Mesogobius batrachocephalus (Fig. 140).

Fig. 140. Toad goby

A fish species of the family Gobiidae distributed in the Black Sea and Caspian Sea basins. In recent years, the toad goby has expanded its range in the Dnieper River and has become a common species in the vicinity of Kyiv and the Kyiv Reservoir. It inhabits coastal waters, estuaries, and the brackish and freshwater lagoons of the Black and Azov seas. It reaches lengths of 35–40 cm with a weight of up to 600 g and lives for up to eight years. It begins spawning in its third year of life, reproducing once a year between February and March, and deposits its eggs among stones. Preferring sandy and rocky substrates, it feeds on shrimp and other crustaceans, mussels, other mollusks, as well as small gobies and other small-sized fish.

Suborder Mugiloidei. They possess two dorsal fins separated by an interval; pelvic fins are positioned behind the pectoral fins. Scales are cycloid or ctenoid. Comprising about 150 species distributed in tropical and temperate marine waters, this group includes many valuable commercial species. Barracudas are pike-like in appearance — predatory fishes equipped with large, sharp teeth that hunt schooling fish and large invertebrates. Various species of mullets (genera Mugil and Liza) feature a torpedo-shaped body and a small mouth with tiny teeth. They inhabit coastal marine waters and estuarine areas, feeding on detritus and benthic invertebrates.

Genus Mullet - Mugil

Flathead mullet - Mugil cephalus (Fig. 141).

Fig. 141. Flathead mullet

Genus Liza - Liza.

In the Black Sea, leaping mullet (гостроніс) - Liza saliens is common (Fig. 142).

Fig. 142. Leaping mullet

Golden grey mullet - Liza aurata (Fig. 143).

Fig. 143. Golden grey mullet

Redlip mullet, or haarder - Liza haematocheila (Fig. 144).

Fig. 144. Redlip mullet

A semi-anadromous fish of the mullet family (Mugilidae). Sometimes the haarder is assigned to the genus Mugil (originally described as Mugil soiuy), but currently this species is classified under the genus Liza [1]. At all stages of postembryonic development, the haarder can inhabit water with a wide range of salinity (0 - 33%о) and temperatures. It forms schools. It feeds mainly on detritus and occasionally on small invertebrates. The Azov haarder is distinguished by larger size (sometimes reaching up to 80 cm in length and 12 kg in weight) and more intensive growth compared to the Far Eastern population. Adult individuals in the Black and Azov Sea basins remain active throughout the year; feeding ceases only when water temperatures drop to 5-8°C. Sexual maturity is reached at the age of 4 - 5 years. Spawning occurs in the coastal zone in May - June.