The impact of an invasive mud crab on brood success of nest-building fish in the Northern Baltic Sea

Abstract

1Native fauna in species poor communities, such as those of the Baltic Sea, may be particularly 2 vulnerable to the effects of species invasions. However, the interspecific interactions that 3 result in the negative impacts on native species tend to be poorly understood. One 4 contributing factor to this knowledge gap may be that the vulnerability of native species can 5 vary between different life-history stages. For example, the parental care phase is often risky 6 both for the developing offspring and care-giving parents. Accordingly, we investigated the 7 interactions between invasive mud crabs, Rhithropanopeus harrissii, and native nest-building 8 littoral fish, with a special focus on the sand goby, Pomatoschistus minutus. Firstly, our field 9 survey demonstrated that while the recently established mud crab and native nest-building 10 fish have different habitat and depth optima, their distributions also have a considerable 11 overlap, with a high potential for interactions between them. Secondly, our laboratory 12 experiments indicate that the crabs are likely to impact the fish negatively, especially by 13 taking over occupied nests, as well as pre-occupying nesting resources that are of very limited 14 supply in the studied population. We did not find evidence for successful predation on eggs 15 guarded by male sand gobies naive to the mud crabs. Collectively, the results suggest that the 16 invasive crabs have high potential to negatively impact native fish. Furthermore, the results 17 support the scenario that the parental phase can be a particularly vulnerable life-history stage 18 in face of novel selection pressures, such as species invasions. 19 20

Male phenotype and resource type influence nesting behaviour in a fish

“…Such size-assortative choice is most probably due to large males being better able to meet the energetic and ecological demands of owning a large nesting resource. These demands are associated with, for instance, covering the resource with more sand, circulating larger volumes of water when aerating eggs in the nest, or defending the nest and eggs against usurpation, parasitic egg fertilisations or would-be egg predators (Kvarnemo, 1995;Lindström & Pampoulie, 2005;Olsson, Kvarnemo, & Svensson, 2009;Lehtonen et al, 2018).…”

“…Wong, B. B. M., Lehtonen, T. K., & Lindström, K. (2018). Spatial and temporal patterns of 629 nest distribution influence sexual selection in a marine fish.…”

“…In particular, nest characteristics (e.g. size and architecture) can physically limit the maximum number of eggs a male is able to acquire (Lindström, 1988), and affect the investment in brood care (Järvi-Laturi, Lehtonen, Pampoulie, & Lindström, 2008), the susceptibility of eggs to predation (Lindström & Ranta, 1992;Lehtonen, Vesakoski, Yli-Rosti, Saarinen, & Lindström, 2018), or the intensity of intra-specific competition (Lindström, 1992;Svensson & Kvarnemo, 2003).…”

Lack of anti-predator recognition in a marine isopod under the threat of an invasive predatory crab

“…Within the Finnish Archipelago, the crab not only forages on mussels and snails but also on amphipods and isopods (Forsström et al 2015), which provoked a shift in the invertebrate community (Forsström et al 2015;Jormalainen et al 2016). Recently, it was shown that the crab prefers the shelter of rocky bottoms independent of food availability (Riipinen et al 2017), and also that they are likely to negatively impact nest-building fishes by taking over their occupied nests (Lehtonen et al 2018).…”

Context-dependent resource choice in a nest-building fish

“…his mating success (Lindström, 1988). However, bigger is not necessarily better: occupying a large nesting resource is also likely to be associated with costs, such as the need to use more sand for covering the resource, circulation of larger volumes of water when aerating eggs in the larger nest, or defending the nest and eggs against usurpation, parasitic fertilisations and potential egg predators (Kvarnemo, 1995;Lindström & Pampoulie, 2005;Lehtonen, Vesakoski, Yli-Rosti, Saarinen, & Lindström, 2018). Interestingly, males were found to prefer a large nesting resource in the presence of a second, smaller alternative (Wong, Lehtonen, & Lindström, 2008;Lehtonen, Lindström, & Wong, 2013;Flink & Svensson, 2015), whereas some studies presenting sand gobies with a choice of three different sized resources have found a preference for the intermediate option (Kvarnemo, 1995;Japoshvili, Lehtonen, Wong, & Lindström, 2012;Lehtonen, Wong, & Kvarnemo, 2016).…”