Effects of Geoduck (Panopea generosa Gould, 1850) Aquaculture Gear on Resident
and Transient Macrofauna Communities of Puget Sound, Washington
Journal of Shellfish Research, Vol. 34, No. 1, 189–202, 2015
Author(s): P. Sean McDonald, Aaron W. E. Galloway, Kathleen C. McPeek and Glenn R. Vanblaricom
Source: Journal of Shellfish Research, 34(1):189-202.
Published By: National Shellfisheries Association
DOI: http://dx.doi.org/10.2983/035.034.0122
URL: http://www.bioone.org/doi/full/10.2983/035.034.0122
ABSTRACT In Washington state, commercial culture of geoducks (Panopea generosa) involves large-scale out-planting of juveniles to intertidal habitats, and installation of PVC tubes and netting to exclude predators and increase early survival. Structures associated with this nascent (bold added by RS) aquaculture method are examined to determine whether they affect patterns of use by resident and transient macrofauna. Results are summarized from regular surveys of aquaculture operations and reference beaches
in 2009 to 2011 at three sites during three phases of culture: (1) pregear (–geoducks, –structure), (2) gear present (+geoducks, +structures), and (3) postgear (+geoducks, –structures). Resident macroinvertebrates (infauna and epifauna) were sampled monthly (in most cases) using coring methods at low tide during all three phases. Differences in community composition between culture plots and reference areas were examined with permutational analysis of variance and homogeneity of multivariate
dispersion tests. Scuba and shoreline transect surveys were used to examine habitat use by transient fish and macroinvertebrates. Analysis of similarity and complementary nonmetric multidimensional scaling were used to compare differences between species functional groups and habitat type during different aquaculture phases. Results suggest that resident and transient macrofauna respond differently to structures associated with geoduck aquaculture. No consistent differences in the community of resident macrofauna were observed at culture plots or reference areas at the three sites during any year. Conversely, total abundance of transient fish and macroinvertebrates were more than two times greater at culture plots than reference areas when aquaculture structures were in place. Community composition differed (analysis of similarity) between culture and reference plots during the
gear-present phase, but did not persist to the next farming stage (postgear). Habitat complexity associated with shellfish aquaculture may attract some structure-associated transient species observed infrequently on reference beaches, and may displace other species that typically occur in areas lacking epibenthic structure. This study provides a first look (bold added by RS) at the effects of multiple phases of geoduck farming on macrofauna, and has important implications for the management of a rapidly expanding sector of the aquaculture industry.
KEY WORDS: aquaculture effects, benthic community, geoduck, habitat provision, macrofauna, press disturbance, structural complexity, geoduck, Panopea generosa
Introduction
First of all, as with all scientific articles, they must be read in their entirety, not just the abstract which is only an overview and may not fully express the basis for conclusions or the limitations of the study. You may access the full text here.
One of the reasons that I chose this article is that it is one of three articles specifically cited by Taylor Shellfish in their arguments to the Thurston County Planning Commision in 2020 against restrictions being considered on geoduck aquaculture. In the letter from lawyer Dianni Taylor E, she states “These studies demonstrate that, similar to other forms of shellfish aquaculture, geoduck farming does not have significant environmental impacts when properly managed.”
Simply stated, this scientific study proves nothing of the sort, and to characterize it as a key study supporting aquaculture is an extreme distortion. This is why.
Analysis
First, this study was published in 2015 and is based on data collected in 2009-2011, so it’s far from current. What is also important about that is that the authors describe it as a “first look.” To date, there seems to have been no attempt at further looks to corroborate their findings, yet this is considered a key study worthy of being cited in a legal argument? It’s a small study, honestly performed for the most part, but with very limited importance overall. If this were in the field of medicine, these results would never be actionable.
This study gathered data from three different sites, and, although the authors admit that there were significant differences in the sites, they had to be combined to provide enough data to be statistically analyzed.
The study looked at the effect of geoduck aquaculture in three phases, before planting, during planting, and after removal of geoduck tubes, which was roughly 2 years into the cycle. This pointedly ignores the most invasive phase which is the harvest, when hydraulic wands are used to liquefy the beach as deep as three feet to extract the mature geoduck at age 5-7 years. Ideally, a study would last through a couple of complete cycles, but that would take a lot more time. Funding tends to be limited, and there is usually pressure at Universities to publish, so there might not have been much of an incentive to extend the study.
It’s not much of a surprise that most of the mobile species (not all) increased around the structure of the tubes. I think any 3rd grader with a fishing pole knows that fish like structure, but in science, we do have to prove things. That said, they may have proved something, but an increase in some species does not allow the conclusion that there is no significant impact (a conclusion of the lawyer, not the scientist), and the lack of carrying the study through the harvest phase relegates this paper to a role of minor importance imo.
This is important. In their analysis, they identified 68 different taxa (species). However, their analysis only included 12 species, which they called the most important ones, but didn’t really say why they were the most important ones. It seems that they were the only ones for which they had enough data to analyze. Let’s think about that a minute. 12 species of 68 is less than 18%. And that is only a fraction of what should have been found. The exhaustive literature review attached to GARP suggested that a typical sand/gravel beach should contain 165 species. They made their conclusions based on a small fraction of the species present, excluding in their design anything mobile less than 6 cm long, without an explanation of why these 12 were important. By analogy, consider the Serengeti with its wildness and large population of mammals. If you chose importance by abundance, what would that say about the value of lion in the ecosystem when there might be 1000 times the number of wildebeest? In all ecosytems the interdependence of species is of paramount importance and this study seems to ignore that basic question in order to draw a conclusion from the limited data that they had available. Admittedly, observing a hooved mammal might be a great deal easier than identifying small creatures in the tidelands while scubaing through murky water, but such is the task they outlined for themselves.
There were no significant sightings of salmonids, so they appropriately excluded them from analysis. What? No conclusions about salmon in a landmark study?
This brings up a somewhat tangential subject, but the absence of salmon smolts reminds me that the control sites (a control is a separate area of study supposedly unaffected by whatever parameters are being looked at in the main study area, used for comparison) that were used as a standard, may be far from what was present historically at these sites. The Olympia oyster once covered 70% of Salish Sea tidelands, reduced to only a tiny fraction of that now. If there was a true standard to compare, and the impact being measured was on a beach covered with native oysters, the impact of the implanted geoduck tubes and the subsequent observations would likely have been far different. Out-migrating salmon used to use native Olympia oyster beds as forage ground. It is important to remind ourselves that the controls areas used in these and all similar studies are already degraded. The truth of it is that, sadly, the scientists don’t have much of a choice here.
Finally, I have a real problem with this statement in the authors introduction – “Projection of future aquaculture production to meet human food demands imply an expanding ecological footprint for these activities in nearshore environments.” Whether good or bad, this is a true statement regarding shellfish aquaculture in general, but this is a study about panopea generosa, the geoduck. We don’t eat them. We sell them abroad where they are consumed as an expensive delicacy. They are unnecessary, generally unavailable to the local consumer, and unimportant as a food source in the impacted area where they are grown; The authors inflate the importance of this study with such a statement. I also have a problem with the use of the word “nascent” in the abstract, which appropriately means beginning to be formed, but also has implications of a promising enterprise. The promise happens to be purely financial.
I would be interested in knowing what the authors think about the importance of this study relative to the big questions facing us about expanding aquaculture, especially about whether they endorse the use of their papers by Taylor Shellfish and others to support this expansion.
Ron Smith