Zosterisessor ophiocephalus (Pallas, 1814)
Gobius ophiocephalus Pallas, 1814: Drensky, 1923: 98; Zostericola ophiocephalus Pallas: Drensky, 1931: 16.
Conservation status: in Bulgaria: Vulnerable VU [A1a, c]; International: IUCN [DD], BeC-III.
General distribution. The northeastern Atlantic – the Black Sea, the Sea of Azov, the Sea of Marmara, and the Mediterranean Sea.
Distribution and abundance in Bulgaria. In the past, a common species for the Bulgarian Black Sea coast [1, 2, 3, 4, 5]. It was recorded in the rivers Ropotamo and Karaagach , and in the lakes Varna, Burgas (Vaya) and Mandra . In recent years, it has been found near Kaliakra , in Varna Bay , in the Ropotamo River  and in Pomoriysko Lake [our data]. Its occurrence in the Karaagach River has not been confirmed .
Habitats. Bottom-dwelling species. It inhabits the sea littoral area and the coastal lakes, mainly on fields of eel-grass (Zostera sp.).
Biology. It reaches sexual maturity at the age of 2 years . It spawns repeatedly from April to July. Fecundity is in the range between 10 000 and 45 000 eggs. The females lay their eggs in nests, built of algae. It feeds on crustaceans, small fish, larvae of insects. It has a life span of about 5-6 years .
Similar species. In the Bulgarian section of the Black Sea, the following goby species, similar to the grass goby, can be found: Gobius bucchichi, G. cobitis, G. niger and G. paganellus. The grass goby differs from them by the higher number of scales in the lateral line (59-64) and the scaleless cheeks.
Negative factors. The main factors which caused the decrease in species abundance are the loss and degradation of habitats as a result of tourism and recreation development along the Black Sea coast, and the industrial pollution of water.
Conservation measures taken. The species was listed in the Red Data Book of the Black Sea (1999).
Conservation measures needed. Protection of the habitats against pollution, aimed at the restoration of the fields of Zostera sp.
References. 1. Drensky, 1923; 2. Drensky, 1931; 3. Drensky, 1948; 4. Drensky, 1951; 5. Stojanov et al., 1963; 6. Karapetkova, 1976; 7. Gheorghiev, 1967; 8. Sivkov, 2000; 9. Sivkov, 2003; 10. Pehlivanov, 1999; 11. Trichkova et al., 2006; 12. Miller, 1986.
Authors: Yanaki Sivkov, Teodora Trichkova, Tihomir Stefanov