Can the presence of alien Ponto–Caspian gobies affect shelter use by the native European bullhead?

Abstract

Extensive invasion of Ponto-Caspian gobies raised the question how they affect recipient ecosystems. The round and racer goby pose a threat to their native counterparts, cottid species, but the influence of other gobiids is still not sufficiently demonstrated. We experimentally assessed how monkey and western tubenose goby, two of the most widespread species across Central and Western Europe, affected time spent by bullhead in the shelter in different seasons and light conditions. Direct and indirect aggression and guarding the shelter by the fish were also checked. We observed the behaviour of single-species and mixed-species pairs in the presence of a single shelter, with bullhead as a resident and one of three species as an intruder introduced to the tank 24 h later. Neither tubenose nor monkey goby was the stronger competitor, capable of outcompeting bullhead from the shelter. Their influence on the resident bullhead was the same as that of intruding bullhead: all intruders made resident bullhead increase shelter occupancy in spring at night. Moreover, compared to the monkey goby, the tubenose goby spent more time in the shelter, occupied it similarly in both seasons, guarded it more intensely and was more aggressive. The monkey goby displayed indirect aggression more often in spring. Despite these differences, bullhead responded to the presence of both goby species similarly, especially during reproductive season.

The role of intraspecific competition in the dispersal of an invasive fish

“…This species is also crepuscular/nocturnal, spending daylight hours inside a shelter that they leave to forage during darkness (Grabowska et al., ); feeding activity is largely nocturnal (Grabowska & Grabowski, ; Kakareko et al., ). The affinity of racer gobies for shelter is especially pronounced during the reproductive season (Błońska et al., ; Grabowska et al., ; Jermacz et al., ), when shelters serve as nest sites. Because care is exclusively paternal in this species, males occupy shelters for longer than females (Błońska et al., ).…”

“…In many locations, these invasive gobies constitute the most numerous component of fish assemblages (Roche, Janač, & Jurajda, ; Van Kessel, Dorenbosch, Kranenbarg, van der Velde, & Leuven, ). The impact of these goby species on native fauna has yet to be fully characterised, but interspecific competition is one possible mechanism by which they may have an impact, which is supported by experimental studies (Błońska, Kobak, & Grabowska, ; Błońska, Kobak, Kakareko, & Grabowska, ; Jermacz, Kobak, Dzierżyńska, & Kakareko, ).…”

“…In Ponto-Caspian invasive gobies, males are highly territorial and aggressively defend their nesting shelters during the reproductive period (e.g. Błońska et al, 2016;Meunier, Yavno, Ahmed, & Corkum, 2009;Miller, 1984). In this situation, a high density in the core population may drive dispersal when small and subordinate individuals have a greater tendency to move.…”

Shelter competition between the invasive western tubenose goby and the native stone loach is mediated by sex

“…Moreover, the affinity for a shelter and its seasonal changes differ between goby species. In spring, when spawning takes place, tubenose, monkey and racer gobies were interested in seizing shelters, while after the reproductive period (autumn) only tubenose goby remained associated with shelters, whereas the other species considerably decreased their shelter occupancy (Błońska et al, 2016;Grabowska et al, 2016). This indicates that under experimental conditions the western tubenose goby has the highest affinity for a shelter throughout the year among the Ponto-Caspian gobies tested.…”

“…Shelters, like crevices under and among stones, are also important for gobies, which display a similar behaviour to that of the bullhead, with territorial males guarding their nests (Miller, 1984;Grabowska et al, 2016). The influence of the spawning season on the in- tensity of interactions between gobies and European bullhead was shown experimentally by Grabowska et al (2016) and Błońska et al (2016), but the interactions with stone loach are fairly less studied. Moreover, the affinity for a shelter and its seasonal changes differ between goby species.…”