Giant goby
| Giant goby | ||||||||||||
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Giant goby in an aquarium in Galicia, Spain |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Gobius cobitis | ||||||||||||
| Pallas , 1814 |
The Riesengrundel ( Gobius Cobitis ) is a benthic living fish of the genus Gobius from the family of gobies (Gobiidae). G. cobitis is one of the largest goby species with a length of up to 27 cm. The preferred habitat of G. cobitis are brackish water- filled tidal pools lying on the coast . The species was first described in 1814 by Peter Simon Pallas .
features
The distinguishing features of G. cobitis include its relatively small eyes and short tail stalk . Its body is covered with small scales, with the scales on the head not reaching eye level. The scales are mottled gray to olive in color. Dark spots can be clearly seen along the sideline . The outside of the dorsal fin (dorsal), caudal fin (caudal) and anal fin (anal) are grayish in color. The upper rays of the pectoral fin of G. cobitis are not connected by a fin membrane. Side lobes can be clearly seen on the front edge of the small and round pelvic fins (ventral).
During the mating season from spring to mid-summer, the males are darker in color than the females.
G. cobitis reaches a length of up to 27 cm. There are no differences between males and females.
distribution and habitat
G. cobitis is a widespread species of fish in Europe. It occurs on the south west coast of England , from Wembury to the Isles of Scilly . In the eastern Atlantic it can be found from the western English Channel to Morocco . Furthermore, G. cobitis occurs in the entire Mediterranean and, apart from a few areas in the northwest, also in the Black Sea . In Africa, G. cobitis can be found in the Gulf of Suez .
You meet G. Cobitis mainly in the upper intertidal zone in rock pools , so small pools that cater to coastal areas in rock depressions of the splash zone have formed the sea at. It usually stays at a depth of no more than 10 m. The tidal pools occupied by G. cobitis are mostly filled with brackish water and often have a small freshwater inflow . The tidal pools have a high abundance of ulva , a genus of multicellular green algae . The tide pools are mostly rocky and contain large boulders with crevices that are large enough to provide shelter for the fish. Especially the fry with a size of up to 7 cm spend their first months in these tidal pools. When G. cobitis reaches a size of over 7 cm in its first autumn, it is increasingly found in the deeper connecting channels between the sea and tidal pools. Here, too, he looks for large rocks with crevices in which he can hide. Adult fish have been observed following the coast vertically along the tides throughout the day . It is believed that in doing so they maximize their possible food supply.
Despite isolated reports of G. cobitis living in freshwater , there are no documented records of G. cobitis living in freshwater in Europe.
nutrition
G. cobitis is an omnivore that feeds on macro benthos that live on hard substrates . G. cobitis likes to eat green algae . As a predator, it also eats crustaceans , poly bristles , insects and smaller fish .
The eating habits change with the size and age of the fish. Younger G. Cobitis , with a length of up to 8-9 cm feed mainly on small organisms such as copepods , ostracods and amphipods . The larger the fish, the larger the organisms G. cobitis can eat. These include beach crabs , larger amphipods, poly-bristles and large amounts of green algae.
It has been proven that G. cobitis eats almost three times more fish at high tide than at low tide. He remains on the rock bed as a stalking hunter and lies in wait for smaller prey fish. Its prey fish are mainly small sea tadpoles and the larvae of slime fish .
G. cobitis also changes its eating habits with the seasons . In the winter months he has to hunt his food mainly as a predator, since green algae are hardly available at this time of the year.
Reproduction
G. cobitis reaches sexual maturity after 2 years. Females can spawn twice per season. The mating season takes place between spring and summer. Depending on the population, the mating season takes place in different months. Then planted G. Cobitis off the coast of Naples from March to May in Varna continued on the Black Sea from May to July and off the Portuguese coast of the East Atlantic between the beginning of April and July.
Temporal variations in the mating season of fish near the coast are not uncommon. Populations that occur in lower latitudes have a longer mating season than their conspecifics in higher latitudes. This is justified by the fact that winter begins earlier in the higher latitudes. The adults cannot mate until late in the year, as otherwise, due to the lower temperatures and the decreasing food supply in winter, the fish larvae would have to struggle with a significantly higher mortality rate .
The females of G. cobitis usually lay their spawn well protected on the flattened underside of boulders. The boulders under which spawning takes place are located in the tributaries between the sea and tidal pools , which are filled with water even at low tide. The boulders are about 50 cm tall. The spawn is attached to the substrate as a single layer in a spindle-shaped manner with threads. On average, a female lays between 2,000 and 12,000 eggs, depending on her body length. The eggs have an average size of 4.2 mm.
The males guard the area around the boulder with the spawn they have fertilized and, like all goby species, maintain the brood until the larvae hatch. Many males of G. cobitis are polygynous . This means that they fertilize several clutches during the mating season. As a result, the males simultaneously care for the brood for at least two clutches of different females.
At temperatures of 12–16 ° C, the larvae hatch after 22–24 days. If the water temperature is between 15-18 ° C, the larvae hatch after 15-17 days.
Both male and female G. cobitis live on average up to 10 years of age.
Importance to humans
G. cobitis is harmless to humans. In the fishing has G. Cobitis very little importance. However, it is listed as a "Gamefish", which means that it is relevant in sport fishing . In the Red List of Threatened Species of the IUCN was G. Cobitis not yet classified and assessed because of the risk of respect G. Cobitis studies exist not enough.
Individual evidence
- ↑ a b c d e f g h i j H. M. Tillin, K. Riley: Gobius cobitis Giant goby. In: Marine Life Information Network: Biology and Sensitivity Key Information Reviews. Retrieved February 27, 2020 .
- ↑ a b c d e f R. N. Gibson: Observations on the biology of the giant goby, Gobius cobitis Pallas. In: Journal of Fish Biology. Volume 2, 1970, pp. 281-288.
- ↑ D. Verdiell-Cubedo, FJ Olivia-Paterna, M. Torrlava: Condition of Gobius cobitis (Pallas, 1811) juveniles in the Mar Menor coastal lagoon (SE Iberian Peninsula): Effects of inter- and intraspecific fish competition. In: Scienta Maria. Volume 70, 2006, pp. 303-310.
- ↑ C. Faira, VC Almada: Tidal shifts in microhabitat use by Gobius cobitis: an adaptation to its feeding strategy? In: Journal of the Marine Biological Association of the United Kingdom. Volume 89, 2009, pp. 641-643.
- ↑ C. Faria, V. Almada: Microhabitat segregation in three rocky intertidal fish species in Portugal: does it reflect interspecific competition? In: Journal of Fish Biology. Volume 58, 2001, pp. 145-159.
- ^ A b C. Faria, VC Almada: Patterns of spatial distribution and behavior of fish on a rocky intertidal platform at high tide. In: Marine Ecology Progress Series. Volume 316, 2006, pp. 155-164.
- ↑ a b c R. Froese, D. Pauly: Species summary for Gobius cobitis, giant goby. In: Fishbase. Retrieved February 26, 2020 .
- ↑ a b c d e C. Faira, VC Almada: Some aspects of the breeding ecology of Gobius cobitis Pallas and Gobius paganellus L. in the West coast of Portugal. In: Arquivos do Museu Bocage. Volume 2, 1995, pp. 463-471.
- ^ PJ Miller: Age, growth and reproduction of the rock goby, Gobius paganellus L. in the Isle of Man. In: J. Mar. Biol. Ass. UK Volume 41, 1961, pp. 737-769.
- ↑ C. Mazzoldi, MB Rasotto: Extended breeding season in the marbled goby, Pomatoschistus marmoratus (Teleostei: Gobiidae), in the Venetian Lagoon. In: Environmental Biology of Fishes. Volume 61, 2001, pp. 175-183.