Mortality of post-settlement clams Rangia cuneata (Mactridae, Bivalvia) at an early stage of invasion in the Vistula Lagoon (South Baltic) due to biotic and abiotic factors

Ryszard Kornijów,Leszek Rolbiecki,Agata Rychter,Krzysztof Pawlikowski,Aleksander Drgas

doi:10.1007/s10750-017-3489-4

Abstract

The clam Rangia cuneata, originating from the Gulf of Mexico, was recorded in the Vistula Lagoon for the first time in the early 2010s, and quickly became the dominant component of the zoobenthic biomass. To assess mortality as a factor potentially controlling the growth of Rangia population, a year-long field experiment involving marked bivalves placed in sediment-filled trays deployed on the bottom was conducted in 2014 and 2015. Predator-induced mortality of the clams was low in summer, and very high in the winter–spring period. It was inversely proportional to the size of the clams. Such changes can be partially attributed to predation from at least five fish and three duck species, which contained clams in their digestive tracts. Non-predatory mortality particularly affected large individuals, and was highest in spring, several weeks after the end of winter. We hypothesize that it could be caused by persistent low temperatures over several winter months which led to considerable weakening of the condition of clams. A long winter could also reduce their resistance to environmental stress and potential effect of epibionts, as well as increase susceptibility to predation.

Highlights

Invasive alien species are an increasingly serious ecological and socio-economic issue worldwide (Williamson & Fitter, 1996; Sala et al, 2000; Katsanevakis et al, 2014), positive impacts do exist (e.g., Charles & Dukes, 2007)
No research has been conducted on temporal patterns of survivorship/mortality of R. cuneata throughout the year
The literature on the subject provides only data referring to single findings concerning winter mass mortality of clams probably caused by factors unrelated to predation (Tenore et al, 1968; Gallagher & Wells, 1969; Hopkins & Andrews, 1970; Gusev & Rudinskaya, 2013)

Summary

Introduction

Invasive alien species are an increasingly serious ecological and socio-economic issue worldwide (Williamson & Fitter, 1996; Sala et al, 2000; Katsanevakis et al, 2014), positive impacts do exist (e.g., Charles & Dukes, 2007). We analysed losses of clams caused by predators and nonpredatory causes that could result from the influence of abiotic factors (e.g., water oxygenation and salinity, temperature). We expected increased clam losses due to predation pressure in summer, when ectothermal predators are most active, and increased mortality caused by abiotic factors in winter, as a result of harsh conditions.

Results

Conclusion