Location: Forage Seed and Cereal Research Unit
Project Number: 2072-63000-004-000-D
Project Type: In-House Appropriated
Start Date: Dec 14, 2014
End Date: Dec 13, 2019
Objective:
This research will develop an improved understanding of the ecology of bivalve shellfish aquaculture in the estuarine environment in order to increase production by reducing mortality while ensuring that culture practices are sustainable and environmentally compatible. Mortality of bivales during this rearing process can be high resulting in low harvest and production. This project addresses two sources of juvenile mortality and attempts to quantify them at the estuarine landscape scale. Burrowing shrimp act as pests causing oysters to sink under the surface of the sediment and die. Shrimp have pelagic larvae that settle and recruit annually to the benthic population on estuarine tidelands where shellfish are grown. Recruitment will be modeled to develop improved control strategies for the industry. Juvenile shellfish are also subject to changing water chemistry due in part to anthropogenic carbon dioxide release and reduced carbonate saturation states which cause problems with shell formation and growth. This problem will also be examined to seek strategies that could mitigate effects at the estuarine landscape scale. Shellfish production is also constrained by regulatory actions regarding siting shellfish farms in the estuarine environment. The estuarine landscape includes a number of habitats including beds of submerged aquatic vegetation, open mudflat and shellfish. This project seeks to quantify these habitats, describe the interaction between shellfish culture production and aquatic vegetation and describe the functional value of these habitats for fish and invertebrates at the estuarine landscape scale.
Objective 1: Quantify and model burrowing shrimp and ocean acidification as sources of juvenile shellfish mortality that constrain oyster aquaculture production in the West Coast estuaries.
Sub-objective 1.1. Quantify how annual recruitment patterns affect population dynamics of burrowing shrimp in the estuaries. Model this at the landscape scale and develop control strategies for sustainable shellfish culture.
Sub-objective 1.2. Determine whether reduced carbonate saturation states are a source of reduced growth and increased mortality of juvenile oysters after they leave the hatchery. Quantify juvenile oyster growth and mortality at a landscape scale in estuaries comparing habitats and locations as potential mitigating factors.
Objective 2: Quantify the influence of shellfish aquaculture practices on existing estuarine habitats and quantify utilization of these habitats, including shellfish aquaculture, by fish and invertebrates at the estuarine landscape scale.
Subobjective 2.1. Quantify the effects of oyster aquaculture on aquatic vegetation and utilize habitat maps to examine this interaction at the estuarine landscape scale and over inter-annual time frames.
Subobjective 2.2. Quantify fish and invertebrate use of intertidal habitats including oyster aquaculture in Willapa Bay; evaluate the functional value of these habitats for fish and invertebrates.
Approach:
This research addresses two current problems that constrain the shellfish aquaculture industry: 1) a lack of understanding about and the ability to eliminate or at least mitigate the effects of early mortality of juveniles caused by changing ocean conditions and pests such as burrowing shrimp and 2) environmental regulations concerning the impact of shellfish farming practices on the estuarine environment. Long term records of burrowing shrimp populations and new collections of animals from shellfish beds and control areas will be used to quantify the contribution of annual recruitment to shrimp population dynamics. Shrimp will be aged using the pigment lipofuscin and data used to develop a predictive index and define a threshold at which treatment to control these pests is necessary. Shellfish growers have observed the effects of changing ocean conditions (high PC02, acidic water) on larvae in the hatchery and potential effects on juvenile oyster seed in some growing areas. Field experiments will be conducted to verify oyster mortality due to poor water quality and track growth and survival over time along estuarine gradients. The effect of eelgrass which can potentially mitigate the effect of poor water chemistry via photosynthesis will also be investigated to suggest potential best management practices.
Shellfish aquaculture modifies the estuarine environment and habitat including the presence of seagrass utilized by fish and invertebrates at the local scale. The known role of seagrasses as valuable estuarine nursery habitat for fish and invertebrates and existing no-net-loss provisions in federal and state regulations has resulted in a very precautionary approach by managers that avoids any direct impacts or damage to seagrass. The Army Corps of Engineers nationwide permits for shellfish aquaculture require notification prior to any shellfish activity in seagrass and a buffer zone between shellfish culture and seagrass, yet little scientific guidance exists regarding the functional value of either seagrass and especially aquaculture for species of concern at the estuarine landscape scale. During the next five years we will expand on prior research addressing effects of shellfish at mostly experimental scales using surveys and maps created from aerial photography for three west coast estuaries to examine effects on the estuarine landscape. Use of landscape scale features like the native eelgrass corridors, meadows and habitat edges as well as shellfish aquaculture beds and edges will also be evaluated utilizing underwater video and other trapping techniques. Habitat function will be assessed by conducting field microcosm and tethering experiments with juvenile Dungeness crab and English sole. This research will quantify disturbance to eelgrass by shellfish aquaculture at the landscape scale and define functional value of both habitats for species of concern providing a common understanding and a model decision tree for stakeholders making management decisions at individual locations.
