In 2007, the Washington Legislature, at the prompting of environmental organizations such as People For Puget Sound, and the shellfish industry, funded a long term study of the effects on geoduck aquaculture on beaches. This highly politicized issue, due to the expansion of long term geoduck farming on ever increasing locations in the South Sound in particular, was viewed as the best way to resolve the bitter disputes over the industry. Some environmentalists were hoping this would be a ‘smoking gun’ of the issues that the industry is having, while the industry assumed it would vindicate them. It appears that the results do not do either, but do point to concerns that need to be researched over a much longer period in time, and about the trade offs in expanding this industry while attempting to save eelgrass beds for salmon habitat. This is the first real long term study ever attempted here in Puget Sound. Fifteen scientists took part in the study over a six year period.
The short conclusion to the data was that it appeared that there was no immediate concern that geoduck farming is distinctly doing long term negative affects on the ecosystem. Concerns were raised over possible effects that were longer than the scope of this project, and recommendations for further research on these were stated.
There were six priorities to investigate, as mandated by the Legislature:
1. the effects of structures commonly used in the aquaculture industry to protect juvenile geoducks from predation;
2. the effects of commercial harvesting of geoducks from intertidal geoduck beds, focusing on current prevalent harvesting techniques, including a review of the recovery rates for benthic communities after harvest;
3. the extent to which geoducks in standard aquaculture tracts alter the ecological characteristics of overlying waters while the tracts are submerged, including impacts on species diversity and the abundance of other organisms;
4. baseline information regarding naturally existing parasites and diseases in wild and cultured geoducks, including whether and to what extent commercial intertidal geoduck aquaculture practices impact the baseline;
5. genetic interactions between cultured and wild geoducks, including measurement of differences between cultured and wild geoducks in term of genetics and reproductive status; and
6. the impact of the use of sterile triploid geoducks and whether triploid animals diminish the genetic interactions between wild and cultured geoducks.
Conclusions of the study indicated that the farms do impact eelgrass while the farms are in place, but that the grass recovers when they are removed. But more research on the effects is needed they added.
Effects of harvest on the benthic layer showed little negative impact, but there are a variety of other issues around this topic that need further study, such as spatial and temporal cumulative effects, the report added.
Effects of Nitrogen and Phosphorus accumulation was ‘mixed’ but did not show any kind of damning evidence that would be cause for immediate action. It appears that the beds do lead to a small increase in both these elements.
Disease issues included finding of several previously unreported parasites in geoducks. However, this data only creates a baseline for future studies. There was no conclusion as to the long term negative effects and whether the farms are contributing in any signficant way to the parasites presence.
Issues related to destruction of eelgrass beds showed that the long term effects seemed minimal, but the short term effects were significant. This raises the issue, given the efforts to recover and protect eelgrass beds, that there is a trade off on a yearly basis between salmon habitat and geoduck planting. There is no conclusion as to how significant this is. More research is needed on this topic, the report stated.
More research was recommended on cumulative effects longer time frames, water column effects, disease identification tools and prevalence in farmed populations, contribution of issues of reproductive effects on natural populations, and genetic effects on native stocks.
The entire report can be viewed at: