Population structure, condition, and reproduction characteristics of native monkey goby, <I>Neogobius fluviatilis</I> (Actinopterygii: Perciformes Gobiidae), in the Bulgarian Danube

Abstract

Konečná M., Jurajda P. 2012. Population structure, condition, and reproduction characteristics of native monkey goby, Neogobius fluviatilis (Actinopterygii: Perciformes Gobiidae), in the Bulgarian Danube. Acta Ichthyol. Piscat. 42 (4): 321-327.Background. Monkey goby is one of many Neogobius species that have invaded European waters in recent decades. Little interest has been paid to this species up till now, probably due to its lower rate of invasiveness compared to some other goby species, e.g., round goby. As with any non-native species, however, it represents a potential danger for native fauna. The aim of this study is to fill in the missing data concerning monkey goby biology and population structure in its native area of distribution, thereby providing a baseline for future comparative studies in non-native distribution areas. Materials and methods. Samples of monkey gobies, Neogobius fluviatilis (Pallas, 1814), were obtained seasonally from the lower, Bulgarian stretch of the Danube River during 2006. The fish collected were sexed, measured, and weighed. After that the gonads were removed and weighed. These data were used to calculate sex ratio, length-frequency distribution, condition coefficient, and gonadosomatic index. Dissected ovaries were used for histological analysis of oocyte distribution.Results. The monkey goby population displayed a relatively balanced sex ratio, while length-frequency distribution demonstrated two-(April), and later three (October), clearly visible peaks, representing three age classes. The condition factor of both males and females was influenced by season. We were able to estimate the starting time and the duration of the spawning season using both gonadosomatic index and ovarian histological analysis. Conclusion. Population of monkey goby in the Bulgarian Danube is an example of a stable native population defined by balanced sex ratio, three-year life span, and recruitment represented by strong cohort of 0+ fish, some of them maturing in their second year of life.

Aspects of reproductive biology of the red gobyTrypauchen vagina(Gobiidae) from the Mekong Delta

“…are also multiple spawners, laying eggs from May to November in the nest under rocks, according to Yamasaki, Kondo, Maeda, and Tachihara (). This spawning strategy is also observed in the round goby N. melanostomus from May to July in Canada (Macinnis & Corkum, ) and the monkey goby Neogobius fluviatilis from May to August in the Bulgarian Danube (Konečná & Jurajda, ). These two species also spawn from mid‐March to mid‐September the Lower Rhine, Germany (Gertzen et al., ).…”

“…Likely, the serial spawning species with group‐asynchronous oocytes were also found in several gobies, i.e., P. elongatus , (Tran, ) B. boddarti (Dinh et al., ) and P. serperaster (Dinh et al., ) caught from the Mekong Delta. Moreover, this spawning strategy is also found in amphidromous goby Sicyopterus lagocephalus from La Réunion Island (Teichert et al., ), the round goby N. melanostomus from Canada and Germany (Gertzen et al., ; Macinnis & Corkum, ) and the monkey goby Neogobius fluviatilis from Bulgarian Danube and Germany (Gertzen et al., ; Konečná & Jurajda, ). Conversely, the goby Valenciennea strigata is a serial spawner depositing eggs every 13 days for a year‐round (Reavis, ) and the bighead goby Ponticola kessleri (e.g., Neogobius kessleri ) displays roughly two batches per season in Slovakia from May to August (Kováč, Copp, & Sousa, ) and in Germany from March to July (Gertzen et al., ).…”

Plasticity in habitat use of two native Ponto-Caspian gobies, Proterorhinus semilunaris and Neogobius fluviatilis: implications for invasive populations

“…The Ponto-Caspian (P-C) region (Black Sea, Sea of Azov and Caspian Sea) remains an important donor region of many invasive species, including invasive gobiid fishes (Roche et al, 2013). Invasions of P-C gobies are now apparent across much of Europe (Wiesner, 2005, Naseka, 2005, Rizevsky et al, 2007, Antsulevich, 2007, Janáč et al, 2012, Konečná and Jurajda, 2012 and in North America (Dillon and Stepien, 2001;Kornis and Vander, 2010;Kocovsky et al, 2011). Invasive gobiids include the western tubenose goby Proterorhinus semilunaris and the monkey goby Neogobius fluviatilis.…”

Novelty versus environment: two viewpoints on the same phenomenon?

“…In our samples, every Neogobius kessleri and N. melanostomus female from both Germany and Bulgaria had one clearly visible batch of mature or maturing oocytes (1.0–1.8 mm) and one clearly visible group of vitellogenic oocytes (0.4–0.8 mm) representing a possible second, and even third, batch. It is true that mature oocytes were not found in N. fluviatilis ; however, this was because the N. fluviatilis spawning season starts considerably later than the two previous species (Konečná & Jurajda ). There is a very high probability, therefore, that all of the females in our study had not yet spent any of their egg batches.…”