Occupation, body size and sex ratio of round goby (Neogobius melanostomus) in established and newly invaded areas of an Ontario river

Abstract

Invasive species represent a challenge because the particular characteristics of a species' invasion are often unknown before the invasion. To provide some clarity as to how invasive species demographic structure might change as a population advances its range, we compared the proportion of occupied sites, size structure and sex ratio of round gobies in the area where they first invaded with more recently invaded areas at the extent of their range in a river in south-eastern Ontario. We used a standardized angling technique to sample gobies larger than 45-mm total length in the summer and early autumn of 2007. Round goby at the upstream and downstream extent of their range occupied a lower proportion of randomly selected sites, and contained a wider distribution of sizes as well as significantly larger individuals. Sex ratios in all areas were malebiased and the male-to-female ratio was significantly higher in the upstream segment of the river (2.2:1) compared to the area of first introduction (1.4:1). The difference between the newly invaded and the established sites suggests that round goby population structure may be affected by density. The results of this study help us further describe the demographic characteristics of biological invasions whilst examples of population structure and behaviour in gobies and other species provide a basis for generating hypotheses for range expansion.

Changes in population characteristics and structure of the signal crayfish at the edge of its invasive range in a European river

“…Such studies have recently become increasingly present in the field of aquatic invasions (cf. Gutowsky and Fox, 2011), partly due to high susceptibility of freshwater ecosystems to invading species (Strayer, 2010) and the extensive and continually increasing rate of unintentional and intentional non-indigenous species introductions (Ricciardi, 2001).…”

First information on age and growth ofPadogobius bonelli(Bonaparte, 1846) outside of its native range: River Aggia (Central Italy)

“…Sexual dimorphism based on the larger size of males is reported as a typical trait of the species Gandolfi et al, 1991;Marconato et al, 1989). Among gobies, males are usually bigger than females, as noted in many other researches (Cápová et al, 2008;Filiz and Toðulga, 2009;Scalici and Gibertini, 2009;Borcherding et al, 2011;Gutowsky and Fox, 2011;Grul'a et al, 2012;Pompei et al, 2015b). Due to maleguarding behaviour, males of several gobies species, such as P. bonelli, may be subjected to a strong sexual selection because the larger males will occupy better nests Marconato et al 1989;Bobbio et al, 1990;Lugli et al, 1992;Scalici and Gibertini, 2009), obtaining a greater chance of attracting a female.…”

“…Females predominance is considered a common trait among gobioid fishes (Miller, 1984) and several researches focused on the biology of gobies noted that females outnumber males (Pampoulie et al, 1999;Azevedo and Simas, 2000;Malavasi et al, 2005;Gutowsky and Fox, 2011;Gkenas and Leonardos, 2012;Grul'a et al,. 2012).…”

“…Parental care is not only energetically costly but also increases the vulnerability of males to predators (Guo et al, 2013), causing a female predominance. Nevertheless, a male-biased sex ratio is found to be frequent on goby populations introduced in a new environment (Tomczak and Sapota, 2006;Kornis et al, 2012;Corkum et al, 2004;Young et al, 2010;Gutowsky and Fox, 2011;Roche et al, 2015). A positive relationship between the egg survival rate and the preponderance of males over females has been observed (Kovtun, 1980), since each male will have to guard nests with fewer eggs, resulting in a greater probability of survival of fry: an unbalanced sex ratio towards males would be favoured in populations settled in a new environment (Tomczak and Sapota, 2006;Kornis et al, 2012).…”

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

“…Overall, the population displayed an even sex ratio, which is typical of a stable native population (Patimar et al 2008, Sasi andBerber 2010), rather than the male-biased sex ratio typical of developing non-native populations (Corkum et al 2004, Gutowsky andFox 2011). Slight differences between samples in different seasons, with males often dominating samples immediately before and during the spawning season, may have been caused by the male's earlier migration to spawning sites (Grabowska 2005).…”