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Projects

Shellfish Aquaculture in an Ecosystem Context

The Ecological Interactions Research Program is currently developing several projects to investigate bottom-up and top-down ecosystem drivers and their interactions with shellfish aquaculture activities.

1. Bottom-Up Drivers

Shellfish aquaculture interacts with both pelagic and benthic environments through deployment of aquaculture structures, harvesting and seeding activities.

In the pelagic environment, within the water-column, oceanographic conditions such as currents, water-column properties, nutrients and primary productivity are important drivers of shellfish population dynamics.  Aquaculture structures in pelagic and benthic habitats (e.g. oyster rafts, intertidal fencing) can alter current dynamics which may influence larval recruitment, nutrients, plankton distributions and particulate material flux to suspension and deposit feeding organisms.   

In the benthic environment aquaculture activities can influence sediment characteristics by changing species abundances or diversity through harvesting and/or artificially seeding beaches. Bivalves have the capacity to affect their own environment through feeding, excretion and bioturbation. These activities alter sediment silt, oxygen, organic and water content. They can also affect sediment stability, modify nutrient dynamics and alter the composition of benthic communities.

In the benthic environment the practice of seeding beaches with clams or oysters alters ‘pre-settlement’ processes (e.g. larval transport and supply) which influence adult population abundance.  This practice provides a unique opportunity to assess the importance of larval supply and settlement to onshore community dynamics - a long-standing question in marine ecology. This question is also of interest to the industry, as shellfish farmers do not know how effective artificial seeding is for increasing shellfish harvest yields.

Research Objectives:

  • Determine the influence of aquaculture structures in nearshore (e.g. deepwater) and onshore (e.g. beach) environments and their interactions with wild and cultured shellfish populations.
  • Monitor oceanographic conditions at aquaculture and control sites and determine their influences on benthic communities
  • Establish the influence of shellfish assemblages on sediment characteristics
  • Determine the importance of natural versus artificial settlement to adult shellfish population dynamics
2. Top-Down Drivers

Aquaculture activities interact with top-down drivers in the ecosystem through shellfish grazing and the alteration of predator distributions. 

Bivalve shellfish populations can exert ‘top-down’ control by reducing total phytoplankton abundances, selectively filtering phytoplankton species, and increasing light penetration.  Top-down control can also be exerted by higher trophic levels predators (e.g. crabs, moonsnails, birds) which are often excluded from intertidal shellfish farms by anti-predator netting or direct removal.  The importance of predators in structuring prey communities is well established; however the ecological consequences of predator-management activities are largely unknown. 

Research Objectives:

  • Investigate the influence of cultured shellfish grazing on phytoplankton communities in deepwater and shallower, nearshore habitats
  • Determine the influence of aquaculture activities on predator distributions

These projects are funded by: Canada Research Chair Program, Canada Foundation for Innovation and the British Columbia Knowledge Development Fund

Olympia Oyster Settlement, Survival and Recruitment

The Olympia oyster (Ostrea lurida) is the only native oyster species in British Columbia and the entire west coast of North America.  Historically this species supported sustenance and commercial fisheries, until over-exploitation, habitat alteration and pollution led to significant declines along the entire coast and near-extirpation in some areas.  Since the early 1900s, impacts on the remaining Olympia oysters have been dramatically reduced. For example, improved industrial practices to reduce sedimentation rates in estuaries and reductions in pollution and habitat alteration. Despite this, their populations have not rebounded.

To improve our understanding of Olympia oyster population dynamics this project will investigate the physical and biological factors influencing larval survival, settlement, and recruitment.  Results will help elucidate the reasons for the lack of population recovery despite negligible harvest pressure since the collapse of the fishery almost a century ago. It will also provide valuable information to commercial industry for species diversification and to conservation organizations for restoration practices.

Research Objectives:

  • Quantify the physical tolerances of Olympia oyster larvae and juveniles
  • Evaluate settlement substrate preferences
  • Monitor natural settlement, recruitment and survival in the field
  • Investigate predation pressure on new recruits and juveniles 

This research is being conducted in collaboration with the World Fisheries Trust and is part of an MSc project being conducted by Alicia Donaldson at the University of Victoria.

This project is funded by:  Canadian Wildlife Federation, Vancouver Island University Research Award and an NSERC PGS-M Award