Dreissenid mussels (including the zebra mussel
Intertidal mussels (Mytilus spp.) and their benthic invertebrate predators were monitored annually for 25 years at 10 sites within Lough Hyne Marine Reserve in southwest Ireland. Mussel abundance was relatively low in the early 1990s but increased substantially after the cold winter of 1995/1996. High mussel abundance was maintained until 2014 after which there was an abrupt decline leading to low levels in 2015–2019, when populations were dominated by older size-classes. Recruitment on benthic rock surfaces in 2018 and 2019 was low in contrast to that on an isolated mooring rope in deep water, suggesting mortality of recruits (e.g. from predation or benthic hypoxia). The generalist predatory starfish, Marthasterias glacialis, increased substantially during the study, with population peaks in 2005 and 2009 that mirrored the peaks of mussel populations. Predatory dogwhelks were not abundant at the monitoring sites and were never seen associated with mussels. Predators or other physical factors may have reduced recruitment, but the decline of the mussel population probably reflected increasing age and removal by wave action combined with consistently sparse recruitment.
more » « less- NSF-PAR ID:
- 10490371
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Molluscan Studies
- Volume:
- 90
- Issue:
- 1
- ISSN:
- 0260-1230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract We used a 27‐year record of
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Dreissena rostriformis ), which still forms a small part (<10%) of the dreissenid community, and a decline in zebra mussel body size. The decline in body size was caused by a long‐term decline in adult survivorship rather than a decline in rates of shell growth. We could detect no long‐term trends in adult abundance or spread ofDreissena onto soft sediments in the Hudson.We observed persistent, strong cycles in adult abundance and body size. These were driven by the appearance and decay of eight dominant year classes over the 27 years of our study, and were a result of temporal variation in recruitment rather than temporal variation in survivorship. The observed strongly irregular recruitment appears to arise from strong adult–larval interactions, and is consistent with previous simulation model results showing that interactions between adults and larvae can drive persistent cycling.
We found evidence that negative density dependence affects recruitment, somatic growth, and body condition of
Dreissena in the Hudson. Warm summers may also cause high adult mortality.We put our results into the context of a conceptual model of
Dreissena population dynamics, and argue that neither the dynamics nor the controls of populations of these important invaders is known satisfactorily.
