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Oysters,Crassostrea virginica, are economically and ecologically valuable but have severely declined, and restoration is needed. As with the restoration and aquaculture of many shellfish species, restored oyster reefs are often impeded by predation losses, reducing restoration success and restricting locations where restored reefs are viable. Like many organisms, shellfish can modify their morphology to reduce predation risk by detecting and responding to chemical signals emanating from predators and injured prey. Oysters grow heavier, stronger shells in response to predation risk cues, which improves their survival. We tested if using predator cues to trigger shell hardening in oysters could be performed over a scale suitable for oyster reef restoration and improve oyster survival long‐term. We constructed an intertidal oyster reef using oysters grown in a nursery for 4 weeks while exposed to either exudates from Blue crab (Callinectes sapidus) predators or grown in controls without predator cues. Oysters grown with predators were 65% harder than those grown in controls, and after 1 year in the field, had a 60% increase in survival. Predation losses on the restored reef were significant, and the benefit of predator induction for survival was highest at intermediate tidal elevations, presumably due to intermediate levels of predation and abiotic stress. Our results suggest that manipulating the morphology of cultivated or restored species can be an effective tool to improve survival in habitats where consumers impede restoration success.
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This content will become publicly available on February 15, 2026
Costs of induced defenses dissipate by maturity for diploid and triploid oysters
Oyster reef restoration efforts and on-bottom aquaculture are frequently plagued with high predation rates. Oysters are phenotypically plastic, and rearing juvenile oysters, Crassostrea virginica, with predator cues causes them to grow stronger shells that increases survivorship in the field. However, induced defenses (e.g., shell hardening in oysters) are often associated with cost-benefit trade-offs, and the extent the increased shell strength persists into adulthood and alters the growth of somatic and reproductive tissues remains unknown. We raised diploid oysters (used in reef restoration) and triploid oysters (used in aquaculture) with and without predator cues for one month before placing individuals on an oyster farm to grow to market size. Oyster shell characteristics, soft tissue mass, and reproductive investment were measured periodically over one year of culture and compared across treatments. Both diploid and triploid oysters had significantly stronger and smaller shells than controls at the end of their nursery period. However, while diploid shells became 15 % stronger and 17 % smaller than controls, triploid shells became 28 % stronger and 23 % smaller. Additionally, triploid oysters exposed to predator cues returned to the size of controls faster and maintained their shell strength differences longer than diploids. Differences in soft tissue mass between treatments mirrored the patterns exhibited in shell size and weight with greater initial physiological costs and faster recovery for triploid individuals. There was no significant difference in somatic or reproductive tissue mass between induced and control oysters of the same ploidy after seven months in the field. Triploid oysters were 15–110 % larger than diploids depending on the characteristic measured at maturity. Additionally, there was a significant interaction between treatment and ploidy because induced triploids had marginally greater growth than their control counterparts while induced diploids had marginally less growth than controls. These findings demonstrate that physiological costs of oysters reacting to predators in early life stages are minimal by the time individuals reach maturity. Early exposure to predator cues is a promising tool for improving oyster survivorship in restoration and aquaculture operations, especially in regions with high predation pressure.
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- Award ID(s):
- 1948423
- PAR ID:
- 10599891
- Editor(s):
- NA
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Aquaculture
- Edition / Version:
- NA
- ISSN:
- 2423-0367
- Subject(s) / Keyword(s):
- Phenotypic plasticity Aquaculture Reef restoration Predator-prey interactions Growth rate
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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