Alternative reproductive tactics are associated with sperm performance in invasive round goby from two different salinity environments

Abstract

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Sperm performance limits the reproduction of an invasive fish in novel salinities

“…Fish of freshwater origin kept in 16 PSU were the least likely to spawn, suggesting that despite higher sperm velocity in 16 PSU, these freshwater fish had limited reproductive ability. Lower energy reserves are commonly seen in freshwater round gobies (Kornis et al, 2012, Table 1; but see Green, Niemax, et al, 2020) and round gobies from brackish origin show increased stress levels in freshwater (Puntila-Dodd et al, 2021). If more energy is required in adverse salinities (Behrens et al, 2017), initial low energy reserves of freshwater round goby are likely to limit their reproductive output even further.…”

“…Adults can migrate from brackish coastal waters and into freshwater streams (Christoffersen et al, 2019), and under laboratory conditions, they readily tolerate varying salinities (Behrens et al, 2017). Adults can in theory also avoid investing in reproduction during unfavourable conditions (Green, Niemax, et al, 2020).…”

“…The gobies in the European rivers, which seem less adapted to freshwater, could have solved the issue by producing longer‐lived sperm. Since trade‐offs between sperm longevity and sperm velocity exist in the round goby (Green, Niemax, et al., 2020), investing in longevity could pay off when velocity is compromised by the environment.…”

“…Adults can migrate from brackish coastal waters and into freshwater streams (Christoffersen et al., 2019), and under laboratory conditions, they readily tolerate varying salinities (Behrens et al., 2017). Adults can in theory also avoid investing in reproduction during unfavourable conditions (Green, Niemax, et al., 2020). Since nest‐holding round goby males are also able to “control” the spawning event via timing of courtship and number of ejaculations, any negative effects of fluctuating environmental conditions may be overcome through behavioural traits instead of plastic physiological responses.…”

“…After salinity ramping, fish were transferred to a breeding tank fitted with a nest box (see below) to produce clutches. Small round goby males can engage in sneaking behaviour and often avoid keeping nests of their own (Green, Niemax et al., 2020; Marentette et al., 2009). To avoid sneaking behaviour, males were always paired with females that were of shorter total length.…”