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The riddle of the sands: How population dynamics explains causes of high bivalve mortality

Callaway, Ruth; Burdon, Daryl; Deasey, Anna; Mazik, Krysia; Elliott, Michael

Authors

Ruth Callaway

Daryl Burdon

Anna Deasey

Profile image of Mike Elliott

Professor Mike Elliott Mike.Elliott@hull.ac.uk
Emeritus Professor of Estuarine and Coastal Sciences/ Research Professor, Institute of Estuarine and Coastal Studies



Contributors

Chris Frid
Editor

Abstract

Large-scale bivalve mortalities in estuarine and coastal habitats are a major environmental and economic concern. They may have obvious causes such as extremely cold winter temperatures, but in the absence of an apparent chain of cause and effect, a rigorous, objective approach is needed to define a probable set of factors responsible for such mortalities. This study interrogates recurrent mortalities of the cockle Cerastoderma edule L. in the Burry Inlet (South Wales, UK), where the causes of the observed die-offs were obscure. Spatial and temporal patterns in cockle population dynamics were analysed to determine whether mortalities were episodic or continuous, and related to cockle density. Laboratory survival experiments complemented the field studies to indicate the fitness of the cockles. The population dynamics of other species were studied to test for environmental disturbances affecting the entire benthic community. High cockle mortalities occurred throughout the estuary in a specific cohort, namely 1-year-old cockles after their first winter. The mortalities did not appear to be episodic, but happened over the spring to early summer months. Cockle densities played a minor role in the decline. The laboratory experiments showed that cockles from the Burry Inlet had higher survival rates than those collected from other areas at early life stages (0-year class). However, by the time they reached the end of their first year (1-year class), their survival rates declined significantly. Results suggested a physiological weakness in the cohort after the first winter. Other benthic species did not suffer unusual mortalities. Synthesis and applications. We emphasize that (i) interrogating patterns in population dynamics allows us to limit the number of likely causes of high bivalve mortality and generate more specific hypotheses; (ii) extending studies to other benthic species indicates the likelihood of environmental problems that affect the entire ecosystem; (iii) joined-up field and laboratory studies suggested that probable causes of cockle mortality were primarily species-, or even cohort-specific, biological factors; and (iv) well-designed monitoring systems will indicate the population dynamics of the target species on spatio-temporal scales suitable for assessing shifts in the populations, such as unexpected extirpation. We emphasize that (i) interrogating patterns in population dynamics allows us to limit the number of likely causes of high bivalve mortality and generate more specific hypotheses; (ii) extending studies to other benthic species indicates the likelihood of environmental problems that affect the entire ecosystem; (iii) joined-up field and laboratory studies suggested that probable causes of cockle mortality were primarily species-, or even cohort-specific, biological factors; and (iv) well-designed monitoring systems will indicate the population dynamics of the target species on spatio-temporal scales suitable for assessing shifts in the populations, such as unexpected extirpation. © 2013 British Ecological Society.

Citation

Callaway, R., Burdon, D., Deasey, A., Mazik, K., & Elliott, M. (2013). The riddle of the sands: How population dynamics explains causes of high bivalve mortality. The journal of applied ecology, 50(4), 1050-1059. https://doi.org/10.1111/1365-2664.12114

Journal Article Type Article
Acceptance Date Apr 29, 2013
Online Publication Date Jun 25, 2013
Publication Date Aug 1, 2013
Deposit Date Jul 19, 2018
Journal Journal of Applied Ecology
Print ISSN 0021-8901
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 50
Issue 4
Pages 1050-1059
DOI https://doi.org/10.1111/1365-2664.12114
Keywords Bivalves; Burry Inlet; Cerastoderma edule; Cockle fisheries management; Population ecology; Wales
Public URL https://hull-repository.worktribe.com/output/532417
Publisher URL https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2664.12114