Production of oyster seed adapted for sea ranching

Description

In Canada, shellfish culture techniques currently used can be divided into two categories: off-bottom and bottom culture. Off-bottom techniques are used in most commercial oyster production in New Brunswick and in Prince Edward Island. However, most of the farm site leases granted are bottom culture leases, which are noticeably underutilized due to predation. The seed available do not meet the specific requirements of this culture technique or of the environment it provides them with.

This research aimed to develop an adapted approach to produce seed especially well-suited to bottom culture, and to establish a tailor-made seeding procedure to minimize the risk of predation. The project also sought to validate the targeted characteristics of the seed for seeding purposes, and the procedures  developed to optimize post-seeding survival rates. Additionally, the project aimed to produce oysters with thicker shells to mitigate against predation impacts, such as the stress experienced by oysters as a result of the aggressiveness of crabs, Cancer irroratus. The project provided the first quantitative information on whether the risk of oyster predation (death) can be reduced by increasing seed oyster size (shell length and thickness).

Consequently, understanding shell properties, in particular the foliated layer, can help us understand the defenses oysters use to survive predation. In the end, the mechanical defense provided by shells allows oysters to perform essential ecosystem services such as habitat formation, water filtration and benthic-pelagic coupling in marine and estuarine systems. In addition, the project aimed to help develop approaches for managing issues relating to the health of aquaculture species.

Findings

This study tested whether or not “bouncing” young oysters in floating buckets could artificially induce the production of thicker and stronger shells to improve their robustness and resiliency to predation. We quantified and compared the shell thickness (mm), compressive strength (Newtons), and shape (fan ratios and cup ratios) of juvenile oysters subjected to this bouncing technique with oysters reared in conventional floating bags, the current industry standard. Results revealed a size-dependent effect of bouncing on shell thickness and strength. Bouncing increased the shell thickness and shell strength for oysters with shell height greater than 45 mm, but decreased shell thickness and strength for oysters with shell height smaller than 45 mm, as compared to control oysters. There was no difference in shell shape between bounced and control oysters. Ultimately, the results suggest that the size at which bounced oysters are released to the benthos for grow out will dictate the usefulness of the bouncing technique for reducing predation-related mortality.

Publications

• Luke A. Poirier, Jeff C. Clements, Rémi Sonier, Léon Lanteigne, André Nadeau, Luc A. Comeau, Testing the efficacy of bouncing-bucket nursery systems for enhancing shell strength and thickness in on-bottom cultured Eastern oysters (Crassostrea virginica),
  Aquacultural Engineering, Volume 90, 2020, 102101, ISSN 0144-8609,
  https://doi.org/10.1016/j.aquaeng.2020.102101.

Program name

Aquaculture Collaborative Research and Development Program (ACRDP)

Years

2017 – 2020

Principal investigator

• Rémi Sonier, Biologist, Fisheries and Oceans Canada, Gulf Fisheries Centre, Gulf Region
  Email: remi.sonier@dfo-mpo.gc.ca
• Luke Poirier, Biologist, Fisheries and Oceans Canada, Gulf Fisheries Centre, Gulf Region.
  Email: Luke.Poirier@dfo-mpo.gc.ca

Team member(s)

Luc Comeau, Research Scientist, Fisheries and Oceans Canada, Gulf Region, Gulf Fisheries Centre, Gulf Region

Collaborator(s)

Léon Lanteigne, L2 - Recherche et Production Aquacole Inc.