Abstract
Losses due to predation are recognized as an important factor affecting shellfish stocks, restoration efforts and aquaculture production. Managing and mitigating the impact of predators require information on the population dynamics and functional responses to prey availability under varying environmental conditions. Asterias spp. are well-known keystone predators with the capacity to exert a top down control on shellfish populations. Asterias spp. populations are extremely plastic, booming fast when prey is abundant and exhibiting a remarkable individual resilience to starvation and adverse environmental conditions. These aspects have led Asterias spp. to be considered pests by shellfish producers and fishers and to be catalogued among the most devastating invasive species. Assessment and mitigation of the impact of Asterias rubens in northern Europe have been the objective of several projects. However, there is still a limited understanding of the processes behind A. rubens population plasticity and how environmental conditions affect individual growth and predation. Under these circumstances a comprehensive eco-physiological model becomes necessary. These models can integrate available information on biology and eco-physiology to gain understanding of the effect of the environmental conditions on the impact of A. rubens.In this work, we performed a number of eco-physiological experiments and combined them with field data from a Danish estuary to estimate and validate the parameters of a dynamic energy budget (DEB) model for the whole life cycle of A. rubens. DEB models can be used to assess the effects of environmental variability on the life cycle and key population traits allowing the prediction of the performance, abundance, resource requirements and potential distribution of individuals and populations under dynamic environments. As such the DEB model presented in this study aims to become a tool to be used to assess and manage the impact of A. rubens in cultured and natural shellfish populations. The successfully parameterised DEB model describes A. rubens as a plastic species, an efficient predator with low maintenance costs and, at least while feeding on mussels, a high energy yield from its prey. The model validation against independent data resulted in the model being capable to assess growth, food demand, reproductive output and reserves dynamics of A. rubens under experimental and natural conditions. Moreover, application of the model to the Limfjorden seastar fishery is used to further discuss the use of the model to understand biology and ecology of this pest species in the context with the management of shellfish stocks and impact mitigation.
Highlights
Bivalve fisheries management, population restoration and aquaculture industries have recognized losses to predation as an important factor determining their productivity (Murray et al 2007; Marino et al 2009; Agüera et al 2012; Wilcox and Jeffs 2019)
Assessment and mitigation of the impact of A. rubens in northern Europe shellfish aquaculture and fishing have been the driver of several projects (Hancock 1958; Dolmer 1998; Gallagher et al 2008; Agüera 2015). This interest has resulted in a large number of studies on A. rubens growth, feeding, thermal response, osmotic stress, reproductive dynamics and larval development (Barker and Nichols 1983; Nichols and Barker 1984; Wong and Barbeau 2005; Agüera et al 2012). These results offer a description of the biology and physiology of this species, pointing out the particularities that make of A. rubens a species difficult to manage, such as its indeterminate growth, its highly plastic body continuously adapting to available prey, its resilience to adverse food and environmental conditions and its high reproductive output
A detailed description of the standard dynamic energy budget (DEB) model can be found in the following work (Kooijman 2010; Agüera and Byrne 2018) (Fig. 1)
Summary
Population restoration and aquaculture industries have recognized losses to predation as an important factor determining their productivity (Murray et al 2007; Marino et al 2009; Agüera et al 2012; Wilcox and Jeffs 2019). Predators with a capacity to top-down control prey populations are capable of decimating populations of wild bivalves and aquaculture stocks (Menge 1982; Witman et al 2003). Seastars of the genus Asterias are wellknown keystone predators with the capacity to exert a control on their prey population, consisting mainly of bivalves (Menge 1982). This aspect has led them to be considered. Swarms or feeding fronts that eradicate prey populations are commonly described for Asterias rubens (Sloan 1980; Witman et al 2003)
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