Geoduck Floating Nursery Mason County, Washington
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Year 5 Annual Report Geoduck Floating Nursery Mason County, Washington Prepared for Seattle Shellfish, LLC August 31, 2017 12755-01 Year 5 Annual Report Geoduck Floating Nursery Mason County, Washington Prepared for Seattle Shellfish, LLC August 31, 2017 12755-01 Prepared by Hart Crowser, Inc. Jessica Blanchette Marine Biologist 12755-01 August 31, 2017 Contents 1.0 INTRODUCTION 1 2.0 METHODS 2 2.1 Surface Observations 2 2.2 Diver Surveys 3 3.0 RESULTS 4 3.1 Surface Observations 4 3.2 Diver Surveys 5 4.0 DISCUSSION 6 5.0 REFERENCES 7 TABLES Table 1 – Depths for Each Site, by Date 4 Table 2 – Light Attenuation Coefficients for Each Site, by Direction and Date 5 Table 3 – Dive Survey Results (attached) FIGURES Figure 1 – Monitoring Site Map APPENDIX A Photo Log 12755-01 August 31, 2017 Year 5 Annual Report Geoduck Floating Nursery Mason County, Washington 1.0 INTRODUCTION On March 17, 2010, Seattle Shellfish LLC (Seattle Shellfish) submitted an application through the U.S. Army Corps of Engineers (USACE) to transition an existing intertidal “kiddie” pool geoduck nursery system to a floating nursery system in Spencer Cove, an inlet on the northeast side of Harstene Island (Reference Number NWS-2010-258; USACE 2010; Figure 1). The floating nursery system would provide a protected environment to grow geoduck seed clams to an optimal size for survival during the out- planting process (0.4 to 0.6 inches [10–15 millimeters] shell length). Seattle Shellfish typically holds their seed for 6 weeks to 6 months in a protected structure (i.e., nursery), depending on the time of year when it is obtained from the hatchery. Concerns with potential impacts of the intertidal pool system (e.g., habitat impacts, water-quality effects) led Seattle Shellfish to propose the use of a floating geoduck seed nursery system. The floating system is comprised of a series of rafts connected to galvanized steel pilings. This allows for natural hydrologic processes within the intertidal and subtidal environments while still allowing Seattle Shellfish to maintain healthy stocks of geoduck seed (Photograph 1) that will have a higher chance of survival following planting. The Biological Evaluation (BE) for the nursery facility indicates that the seafloor below the floating nursery rafts varies in depth from –5 to –9.3 feet mean lower low water (MLLW) (letter from Environ International Corporation [Environ] to USACE Seattle District, April 25, 2010). Given these shallow depths, shading effects of the floating rafts may be great enough to affect benthic plant and invertebrate communities. In addition, several studies have documented that migrating salmonid juveniles avoid darkened areas, altering their paths to avoid these areas. Mason County issued a conditional Shoreline Permit for this project on May 26, 2010 (Mason County Shoreline Permit No. SHR2008-00016). This permit is subject to five conditions as follows: 1. “The County shall hire a suitably qualified expert to devise and implement a five year monitoring plan at the expense of the Applicant. The monitoring plan shall identify and assess impacts to endangered fish and its habitat. Additional mitigation shall be imposed by staff as necessary to mitigate impacts identified in the monitoring of the plan. 2. Lighting shall be the minimum required by applicable regulations for navigation safety, unless additional lighting is deemed necessary by staff for safe navigation. 3. The floating nurseries shall never reach less than three feet above ground level. 12755-01 August 31, 2017 2 | Year 5 Annual Report – Geoduck Floating Nursery 4. Areas and gear subjected to herring spawn shall not be disturbed until the eggs have hatched, unless the Applicant establishes to staff that compliance with this condition would unreasonably interfere with aquaculture operations. 5. Sand for the nurseries stored in upland areas shall be covered to prevent adverse impacts to water quality.” Hart Crowser involvement includes on-site monitoring for determining outcomes specific to Conditions 1 and 3. Quaterly and annual monitoring of the nursery and habitat provides an assement of potential impacts to aquatic habitat and endangered fish—though currently there are no endangerd fish listed in the vicinity of the nursery—as well as tracking the water depth above the ground level below the floating nursery. This document provides results from the fifth and final year of monitoring. 2.0 METHODS 2.1 Surface Observations Conditions at the floating nursery rafts were documented quarterly between June 2013 and June 2017. The nursery rafts are connected to a floating walkway, referred to as the log boom, which is in turn tethered to the steel pilings. The log boom runs approximately north to south (Figure 1). One survey monitoring station was established at each end of the log boom, with three stations along the log boom at relatively equal distances. The north station was marked as Site 1, with Site 5 at the south end of the log boom. The five stations were permanently marked along the log boom for comparative monitoring. Information documented at each station included photographs, depth measurements, light readings, fish counts, dominant algae and invertebrates, and other general observations. Photographs were taken in the four (approximate) compass directions, in order to capture the surrounding location and water conditions. Depth measurements were taken directly under the log boom, relative to MLLW. Depth was considered accurate to the nearest 10 centimeters (cm), given the soft sediment and poor visibility to the bottom; however, localized currents and wave action can cause readings to vary by 0.5 meters. Light levels were monitored using a LICOR quantum irradiance meter equipped with air and underwater sensors. The LICOR allows for simultaneous air and water light measurements, thus taking into account ambient light levels at the time in-water measurements are collected. Light readings were taken off the east and west sides of the log boom, at the surface and at depth, to measure any shading effects beneath the floating structures. Light units are measured in micro-einsteins per meter squared, and the difference between surface and depth readings was calculated as the attenuation coefficient (K) using the equation: 퐼 ln ( 푧) 퐼 K = 0 −z where I0 is the irradiance at the surface, Iz is irradiance at depth, z (Dixon and Kirkpatrick 1995). 12755-01 August 31, 2017 Year 5 Annual Report – Geoduck Floating Nursery | 3 Greater attenuation coefficients indicate greater light absorption levels through the water column as, for example, from turbidity or plankton. Collectively, the data on light levels allow for the determination of the extent and magnitude of shading caused by the nursery facility. 2.2 Diver Surveys An assessment of fish presence and aquatic habitat conditions was conducted both under and adjacent to the Seattle Shellfish nursery facility on June 21, 2017. This survey followed methods described by Hart Crowser in their Geoduck Floating Nursery Monitoring Plan (2013), and the Field Reconnaissance Studies Report prepared by Environ (2010). Six diving transects were established in the reconnaissance survey of the site. GPS waypoints from the pre-project baseline survey were used by Hart Crowser to reestablish these transects, to allow for comparisons of newly collected data with the observations made in prior years. Two divers swam side-by-side, making observations of biological conditions of the seafloor along the six transects. Each diver made observations within 1 meter on one side of the transect lines, so that collectively their observations covered an area 2 meters wide for the length of each transect. These observations were recorded at 10-meter intervals along each transect. Five of the transects were 50 meters long and ran perpendicular across the floating nursery system while one 150-meter transect ran parallel along the western edge of the log boom. The location of the selected transects are illustrated in Figure 1 and are described as follows. Transect 1: 50 meters long, to the north and perpendicular to the existing floating system where there was no impact from the construction of the float or operation of the shellfish nursery. This is considered a reference transect. Transect 2: 50 meters long, at the north end of the log boom and perpendicular to the existing floating system. Transect 3: 50 meters long, perpendicular to the existing floating system. This transect crosses under the floats near the center of the operation. Transect 4: 50 meters long, perpendicular to the existing floating system. This transect crosses under the floats near the south end of the facility. Transect 5: 50 meters long, at the south end of the log boom and perpendicular to the existing floating system. Transect 6: 150 meters long and along the western edge of the floating structure. This transect ran directly below the rafts that were moored to the log boom. To determine habitat conditions, information documented included sediment condition and type, depth along the transect, microalgae, eelgrass (if present), epibenthic invertebrates, and fish. Macroalgae were quantified by percent cover per square meter. Epibenthic invertebrates and fish were identified to the lowest possible taxonomic unit based on visual observations. 12755-01 August 31, 2017 4 | Year 5 Annual Report – Geoduck Floating Nursery 3.0 RESULTS 3.1 Surface Observations Photographs for each monitoring period were included in previous quarterly monitoring reports. Select photos are included in this report for comparison between monitoring events (Photographs 1–5). The number of platforms attached to the log boom varied between monitoring events. Platforms included the nursery rafts, work platforms for carrying equipment and supplies, and vessels for transporting supplies and personnel. There were generally between three and nine platforms attached to the log boom during observations. No fish were observed in Year 5. Other biota observed included algae and invertebrates.