About Proterorhinus semilunaris (Heckel, 1837)
Proterorhinus semilunaris (Heckel, 1837), commonly called the western tubenose goby, is a small goby fish that most often reaches 12 cm (4.7 in) in length, with an average size of 12.7 cm. Its body and head are flattened laterally, and the width of the head is usually less than the head's height. The species has a cylindrical body with a flattened ventral surface, which matches the flattened body profile of all tubenose gobies. It has 37β46 large cycloid scales; cycloid scales also cover the crown, nape, upper edges of the operculums, origins of the pectoral fins, belly, and posterior part of the throat. This species lacks scales on its lateral line, while the rows above the lateral line hold 45 to 48 scales. Small scales cover the top of the head behind the eyes and along the body midline. Its jaws are equal in length, and it has a wide, slightly subterminal mouth with large lips and no barbels. It has an abdominal sucker without distinct blades, and its ventral fins are fused into a single suction cup shape. The species has no swim bladder. It can be distinguished from the closely related marine tubenose goby P. marmoratus by its head length, which makes up 28β32% of the fish's standard length. The posterior membrane of its first dorsal fin reaches the origin of the second dorsal fin. The first dorsal fin has 7 or 8 spines. The anterior naris reaches the upper lip or the uppermost margin of the lower lip; the tubular nostril is 2β4 centimetres (0.79β1.57 in) long. Eye diameter makes up 16β21% of head length. The caudal fin is rounded and has a triangular black spot at its base. Like all tubenose gobies, it gets its common name from its distinct nostril tubes. The western tubenose goby has tubular nostrils, with the nostril tube extending to the upper lip. This feature distinguishes it from the round goby, which lacks these nostril tubes; it can also be told apart from the round goby by its long anterior nostrils and lack of a black spot on the posterior base of its dorsal fin. Body coloration ranges from brown to yellowish-gray, with 4β5 dark streaks on the back that transform into spots below the middle of the body. The back and sides also have broad, oblique blotches set against a lighter brown or olive background, while the underside of the fish is cream to white. Fins are typically striped. The species is native to fresh waters of the Black Sea basin, and the Maritza and Struma rivers that drain into the Aegean Sea. Its native range includes the Danube River from the delta up to the mouth of the Morava, as well as Danube Lakes from the Prut to IaΘi. In Bulgaria, it is native to the Kamchiya, Ropotamo, Veleka, and Rezovska rivers. It also inhabits the basins of the Dniester and Southern Bug rivers. In the Dnieper river, its natural range extends from the estuary up to the Trubizh River. Within the Sea of Azov basin, it lives in the Don River, Seversky Donets (up to Sviatohirsk), and the Kuban River estuary. It also inhabits Lake Neusiedler. As a non-native invasive species, it has been recorded in Eurasia in the upper reaches of the Danube and Dnieper rivers, the North Sea basin's Rhine-Main system, and the Vistula. Between 2008 and 2010, it was recorded in the Meuse River along the border between Belgium and the Netherlands. This species was introduced to the St. Clair River from Eastern Europe via ship ballast water. It is thought to have spread to Canada and the broader Great Lakes region through use as live bait. By the early 2000s, it had spread north to the Minnesota-Wisconsin border and east to the border of New York and Pennsylvania. Proterorhinus semilunaris inhabits freshwater areas, specifically shallow shore water less than 5 meters deep with slow movement, high plant cover, and abundant macrophytes in lakes and rivers. In the Detroit River, tubenose gobies are positively associated with complex macrophytes in the fall, and negatively associated with these macrophytes in the spring and summer. The species can withstand extremely low levels of dissolved oxygen. It creates nests under rocks and logs in shallow water, and individuals aggressively defend their nest sites. These nesting preferences mean the species could potentially inhabit the shallow waters of all five Great Lakes. Currently, the species is not spreading rapidly, but if it expands its range it could become a threat to native Great Lakes species. Females of this species can live up to 5 years, while males generally have shorter lifespans. Males guard nesting sites to protect their eggs and young. Spawning occurs multiple times during the warmer months of the year, making the species rather prolific. While the species is not spreading rapidly at present, this prolific spawning could create a threat to the native species rainbow darters and Northern madtoms.
