Arno goby (Padogobius nigricans)

The Arno goby (Padogobius nigricans) is a freshwater fish which is endemic to a small number of rivers and lakes in Central Italy ⁽¹⁾. A relatively small species, the Arno goby has a large head and an elongated body which flattens towards the back. The mouth appears almost disproportionately large in comparison with the rest of the body and is equipped with numerous small teeth ⁽³⁾. The male Arno goby is typically larger than the female ^{(3) (4)}.

The Arno goby is dark on the head and yellowish-orange with dark spots on the body. There is a particularly distinctive spot on the bony flap, called the ‘operculum’, which covers the gills ⁽³⁾. The two dorsal fins are grey-brown or reddish-yellow, with spines present on the first dorsal fin, and branching rays on the second ^{(2) (3)}. The pelvic fins of the Arno goby are joined together ⁽³⁾.

Size

Length: up to 12.5 cm ⁽²⁾

A relatively short-lived species, the Arno goby usually begins breeding at around one year of age ⁽²⁾. Spawning occurs between April and July, with the exact timing varying according to the temperature of the water ^{(1) (3)}.

The male Arno goby produces a variety of sound signals during courtship of the female ^{(4) (6) (7)}. This species is extremely territorial during the breeding season ^{(2) (3) (7)}, and the male also demonstrates considerable acoustic activity during the spawning period and when defending the nest or shelter ^{(2) (6) (8)}. The female Arno goby deposits eggs between stones, shells and aquatic plants on the river bed, and the eggs are guarded by the male until they hatch after five to six days ^{(2) (3) (4)}.

The Arno goby feeds on a wide variety of small invertebrates, fish eggs and insect larvae ^{(2) (3) (4)}.

The Arno goby is restricted to six river basins and two lakes in the Tyrrhenian catchment of Central Italy ^{(1) (5)}.

An entirely freshwater species, the Arno goby is typically found in small, shallow, fast-running rivers that have a pebble, gravel or stony bottom and clear, well-oxygenated water ^{(1) (2) (4) (5)}. It may also be found in lakes ⁽¹⁾, and generally occurs close to the shore, particularly in well vegetated areas ^{(2) (3)}.

The Arno goby is classified as Vulnerable (VU) on the IUCN Red List ⁽¹⁾.

The Arno goby has a fairly restricted range, and the population is under pressure from a number of threats. In particular, the Arno goby is threatened by the introduction of the non-native, invasive goby species, Padogobius bonelli, which competes with the Arno goby for space and resources. Padogobius bonelli is thought to have caused the local extinction of the Arno goby in the river basins of Ombrone, Amaseno and Mignone in Central Italy ⁽¹⁾.

The Arno goby is also threatened by habitat destruction and fragmentation, water extraction and pollution. It may also be affected by climate change ^{(1) (7) (9)}. 

This species is listed on Annex II of the European Union Habitats Directive ⁽¹⁰⁾ and on Appendix III of the Bern Convention on the Conservation of European Wildlife and Natural Habitats, which aims to conserve wild flora and fauna and their natural habitats ⁽¹¹⁾. The Arno goby is also protected by regional law in Central Italy ⁽⁹⁾.

• FishBase:
  http://www.fishbase.org/

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Dorsal fin

The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.

Pelvic fins

In fish, the pair of fins found on the underside of the body.

Spawning

The production or depositing of large quantities of eggs in water.

Territorial

Describes an animal, a pair of animals or a colony that occupies and defends an area.

1. IUCN Red List (May, 2011)
   http://www.iucnredlist.org/
2. FishBase - Arno goby (May, 2011)
   http://www.fishbase.org/summary/speciessummary.php?id=6345
3. L’Istituto per lo Studio degli Ecosistemi: Specie ittiche d’acqua dolce e salmastra del territorio Italiano - Padogobius nigricans (May, 2011)
   http://www.iii.to.cnr.it/pesci/ghioarno.htm
4. Zeruniana, S., D'onofrioa, E. and Gibertinia, G. (1988) The biology of Gobius nigricans (Osteichthyes, Gobiidae). I. Observations on the reproductive behaviour. Italian Journal of Zoology, 55: 293-298.
5. European Topic Centre on Biological Diversity (2009) Habitats Directive Article 17 Reporting. Padagobius nigricans. European Environment Agency, Copenhagen. Available at:
   http://eea.eionet.europa.eu/Public/irc/eionet-circle/habitats-art17report/library?l=/datasheets/species/fish/fish/padogobius_nigricanspdf/_EN_1.0_&a=d
6. Lugli, M., Torricelli, P., Pavan, G. and Miller, P.J. (1996) Breeding sounds of male Padogobius nigricans with suggestions for further evolutionary study of vocal behaviour in gobioid fishes. Journal of Fish Biology, 49(4): 648-657.
7. Scalici, M. and Gibertini, G. (2009) Freshwater goby life history in a Mediterranean stream. Hydrobiologia, 628: 177-189.
8. Lugli, M., Yan, Y. and Fine, M.L. (2003) Acoustic communication in two freshwater gobies: the relationship between ambient noise, hearing thresholds and sound spectrum. Journal of Comparative Physiology, 189: 309-320.
9. Tockner, K., Uehlinger, U. and Robinson, C.T. (2008) Rivers of Europe. Academic Press, London.
10. EC Habitats Directive (May, 2011)
    http://www.jncc.gov.uk/page-1374
11. Council of Europe: Bern Convention (May, 2011)
    http://conventions.coe.int/Treaty/EN/Treaties/Html/104.htm