Targeted substrate design is required to improve post-settlement survival of shellfish

Area of Science:

• Marine ecology
• Restoration ecology
• Bivalve aquaculture

Background:

• Biotic stressors like predation significantly impact shellfish reef restoration success.
• Seeding is common in recruitment-limited systems, but post-seeding survival remains a challenge.
• Novel substrates with refuges are increasingly tested to improve shellfish settlement and survival.

Purpose of the Study:

• To investigate the effect of surface roughness and complexity on the post-settlement survival of juvenile oysters (Ostrea angasi).
• To assess if substrate complexity influences predator access and consumption rates.

Main Methods:

• Concrete tiles with sandblasted (rough) or grooved/ridged (complex) surfaces were created.
• Tiles were seeded with Ostrea angasi and deployed in the field for 15 months.
• Predator access was evaluated by measuring mussel bait consumption on complex tiles.

Main Results:

• Neither sandblasting nor surface complexity significantly altered the post-settlement survival of Ostrea angasi.
• Predator consumption of mussel baits did not differ among complex tiles.
• Previous findings of enhanced larval settlement on complex surfaces were not replicated in post-settlement survival.

Conclusions:

• While rough or complex surfaces can enhance larval settlement, they are insufficient to improve post-settlement survival of oysters.
• Restoration substrate design must address mechanisms driving survival across multiple life stages.
• Current substrate complexity was inadequate to deter predation on juvenile oysters.