The effect of macrofaunal disturbance on Cerastoderma edule post-larvae

Abstract

Populations of the Common European cockle (Cerastoderma edule) often have highly patchy distributions and variable recruitment success. One of the proposed reasons is that high densities of filter feeders and / or bioturbators are thought to reduce the success of larval settlement and post-settlement survival, but the direct causal processes driving these observations are not clearly identified and validated. Through combined field and laboratory experiments, we test the hypothesis that macrofauna cause decreases in post-larval density through feeding and movement activities. The effect of excluding the bioturbating lugworm Arenicola marina and filter-feeding adult cockles on post-larval cockle densities was estimated in separate field experiments at two locations from the time of initial larval settlement in May 2012 to late summer August 2012. Lugworm exclusion led to a significant increase in cockle post-larval densities whereas the opposite was true for adult cockles, where exclusion led to a reduction in C. edule post-larval density. Although clear effects were observed in the field, experiments conducted in the laboratory failed to detect changes in mortality or byssus drifting of post-larvae as a consequence of macrofaunal activity. This study demonstrates that the presence of macrofauna can have both positive and negative effects on post-settlement density of C. edule post-larvae. Thus the density, distribution and identity of macrofauna have significant effects on the density and spatial distribution of C. edule post-larvae during the post-settlement period. These observations have implications for conservation and fishery management of this species.Keywords: Arenicola marina, Cerastoderma edule, interaction, post-larvae, cockle, settlement Highlights  The effect of macrofauna presence on colonisation of cockle post-larvae was tested.  Combined field and laboratory studies were used.

Biology of the common cockle Cerastoderma edule (Linnaeus, 1758) in Ria de Aveiro (NW Portugal): Implications for fisheries management

“…Donadi et al (2014) refer that adult cockles can enhance the recruitment of juvenile conspecifics by increasing sediment stability in high-energy tidal sand flats. Although it was not recognised the key driving factor, Whitton et al (2016) stated that the exclusion of adult cockles led to a significant reduction in C. edule post-larval densities and may reduce up to 50% the recruitment potential of an area. On the other hand, there is some evidence that C.…”