PREPARED FOR:

NOAA National Marine Fisheries Service

National Sea Grant College Program,

Office of Oceanic and Atmospheric Research

Washington D.C.

DATED:

23 July 2003

WITH A GRANT TO:

Washington Fish Growers Association

10420 173rd Ave. SW
Rochester, WA 98579

PREPARED BY:

J.E. Jack Rensel.^1/ J.R.M. Forster.^{2/ ,}

^{1/  Rensel} Associates Aquatic Sciences Consultants

    4209 234th Street N.E. 

    Arlington, Washington 98223

    jackrensel@att.net

^{2/  Forster} Consulting Inc.
    533 East Park Avenue,
    Port Angeles, Washington 98362

    jforster@olypen.com

Introduction

This summary report is an expanded abstract of the second year (2002) of field studies conducted in the Strait of Juan de Fuca (the “Strait”) for the NOAA Fisheries-sponsored offshore mariculture feasibility study described in prior reports (Rensel and Forster 2002a, 2002b).

Figure 1 shows the general configuration of the Strait and Figures 2, 3 and 4 are maps of specific study areas.  As discussed in prior reports, all of these areas have potential for net pen aquaculture and none of them should have significant, site specific resource or shoreline owner conflicts which have prevented growth of the industry in Puget Sound.  However, this may not deter those who are generally opposed to aquaculture in the region from raising objections.

In 2002 we made vessel based observations on 14 separate days, to add to long-term thermograph and satellite (sea surface temperature) data collected continuously.  Current and wave meter and circulation (drift object) studies were conducted too.  No attempt is made to recap a literature survey and year 1 (part of 2001) results, but 2002 results are summarized herein.  See Rensel and Forster (2003) for the full report from which this summary is drawn.

Growing and Environmental Impact Conditions:

We are studying a number of factors relating to fish culture siting and impact assessment, but one of the most important considerations in this area for fish growth is dissolved oxygen (DO).  Seasonally low DO occurs in all marine waters of the Strait and northern Puget Sound during the late summer and fall, but our prior literature review showed that it was poorly documented in the Strait. 

One important question addressed by this study is:  Are dissolved oxygen conditions worse, the same, or better than at existing inshore fish farms in (North) Puget Sound? 

From our work to date it appears that conditions are generally similar, particularly in the west end and Port Angeles-Green Point areas.  This means that all forms of net pen finfish culture should be technically feasible in the Strait, and perhaps more so than in Puget Sound as discussed below.

We are encouraged by the results to date and feel that the Strait offers some distinct advantages for net pen culture compared to other coastal US areas.  The DO studies may be summarized by noting:

·         DO concentrations in surface water of the Strait do not appear to be an impediment of marine fishes being considered for net pen culture, especially for black cod (sablefish).

·         The true annual duration of relatively low surface DO concentrations (<4.5 mg/L) during the fall over very long periods (e.g., a decade) remains a speculative matter, but based on our literature survey, and results of two years of sampling it likely varies from zero days per year in full scale El Niño events to at most a month in La Niña or drought years like 2001. 

·         We observed higher dissolved oxygen concentrations in surface waters of the Strait in the fall of 2002 than during 2001.

·         Dissolved oxygen and algal biomass were positively correlated and both were inversely correlated with degree of tidal amplitude.  Large tidal exchange mixes deep water into the surface and limits algal population by dilution.  See Figure 5 for an example.

·         Our vertical profile data showed that DO was generally similar on same day samplings throughout the Strait, reaching a low point of ~4.5 mg/L in early October 2002 (Fig. 6).  Upwelling intensity on the open coasts matched this pattern of occurrence.  The shape of the vertical profiles in 2002 was different than 2001, when there was only a thin layer a few meters deep of most highly oxygenated surface water.   The distributions were much more gradual in 2002.  Our vertical profile data, however, were not as extensive as the satellite data discussed below.

·         Comparison of vertical profile averages in the Strait with concurrently collected data in the San Juan Islands at Cypress Island indicated similar to slightly higher DO concentrations in the Strait (Fig. 7).   Cypress Island is the site of a long-term (>15 years) net pen farm.

·         A combination of reduced river flow from the 2000-2001 drought (Fig. 8) and increased upwelling on the Washington State coast during the fall of 2001 (Fig. 9)were apparently responsible for the relatively low DO measured in the Strait during the fall of 2001.

·         A moderate El Niño occurred in the tropics during 2002, but it was only weakly felt in the study area, according to other government studies. 

·         Given the above, our two study years appear to have bracketed conditions from very low DO to moderately enhanced DO, a fortuitous range in terms of describing the range of conditions.

·         A review of many sea-surface-temperature (SST) satellite images of the Strait from the late summer and early fall of 2002 suggests that the central Strait (immediately west of Port Angeles to Pillar Point including the Agate Bay-Whiskey Creek area) is often cooler than either end of the Strait (see example images Figures 10-13).

·         Since DO and near surface water temperature are positively correlated in this area during the late summer and fall (Rensel and Forster 2002b), we tentatively conclude that the middle Strait area may be less suitable for salmon culture than either the west or east portions of the Strait. The precise cause(s) of the differences are unknown, but may relate to constriction of the Strait to its narrowest width at this point. The east end near Dungeness Bay and Port Angeles had slightly higher water temperatures that appear to be related to higher DO content (Table 1). 

·         Slack tide periods are very minimal and current velocity is stronger in the Strait than in much of Puget Sound, providing a more continuous and sustained DO supply. But the strong currents may also make it difficult for small fish, requiring that they be reared in 'nursery' facilities elsewhere and then 'grown out' to market size in the Strait

·         Slightly lower water temperature in the Strait during summer should also be an advantage in reducing basal metabolic demand for oxygen, while winter temperatures are slightly warmer than Puget Sound which should help increase growth.

·         Correlation analysis showed that 60% of the variation of near surface DO in the Strait near Port Angeles was associated with changes in phytoplankton biomass, i.e., algae are partially responsible for oxygenation of the surface waters.   Inflow of water from other areas including surface water from Puget Sound and the Pacific Ocean must account for the balance.

·         Slightly higher DO concentrations were noted in Port Angeles Harbor versus a station offshore of Ediz Hook in the Strait and were related to differences in standing stock of phytoplankton.

Tidal Variation and Water Temperature Variation

Shallow water temperature and DO varied significantly with tidal activity in the Strait of Juan de Fuca and portions of North Puget Sound.  Specifically:

• The temperature at five meters depth was inversely related to amplitude of tidal exchange, although the relationships, while appearing visually strong, were statistically only moderate.  Other factors including weather and changes in solar heating play important roles. 
• The water temperature and tidal exchange relationship took longer to be established at Cypress Island than at Port Angeles Harbor.  Higher average and more extreme high temperatures occurred at Cypress Island from June through August 2002, and then much cooler water was prevalent Port Angeles into the 2^nd week of November.
• Water temperature trends generally matched each other at both sites, but some significant and inexplicable differences were noted, particularly in mid August when a sunny/hot weather affected water temperatures at Cypress Island but apparently not a Port Angeles Harbor. 

Currents and Drogue Studies:

Preliminary acoustic Doppler current profiler (ADCP) and drogue (drift object) data were collected offshore of Neah Bay, Whiskey Creek and Green Point in the west, central and eastern/central areas of the Strait, respectively.  See Figures 14 through 22 for example work products from the full report.  Direct comparison of velocity among sites is not appropriate for these data as the surveys were collected on different (but sequential) days with varying tidal conditions.  However, it can be stated that:

·         Tidal current velocity at all studied locations appear more than adequate for minimizing impact of large scale mariculture, i.e., currents are strong, flow direction is mostly parallel to shore, sea bottoms are relatively flat and featureless which would facilitate solids dispersion, and  essentially no near-field permanent deposition would be expected.   

·         A two month winter record of tidal current velocity and wave data was recorded offshore of Neah Bay, and the results show monthly maximum velocity for a short period of ~95 cm/s.  Most observations, however, were in a moderate range from 10 to 60 cm/s with a mean of 31 cm/s.  A similar meter was deployed several meters below the surface at Green Point but later recovered in Port Angeles Harbor with a damaged data module.  The meter apparently was hit by a vessel and dragged into port.

·         Some eddy activity was seen nearshore and at moderate depth at Whiskey Creek that may be related to nearby headlands and bathymetry. 

·         Current velocity was generally strong at Whiskey Creek during ADCP surveys.  From depths of about 90’ (MLLW) depth and greater, near bottom to mid depth tidal currents were lower in velocity than the 50’ to 90’ (MLLW) depth zone. 

·         Modeling studies of other workers suggest the possibility of transient eddies near Green Point, but more work is required in the field to validate the extent of these occurrences.   

·         Unusual surface to bottom current speed distributions were noted during ebb tide offshore of Neah Bay.  Subsurface and mid-depth tidal velocities were stronger than those at the surface.

·         Concurrent with the unusual current distribution offshore of Neah Bay, surface water masses flowing through the existing “offshore” scallop culture areas flowed directly into Neah Bay.  Subsurface water moved in a different direction, flowing westerly past Waadah Island.

·         The Green Point area had moderately strong currents during the drogue study, but lowest relative transport rates during he ADCP surveys. More ADCP and drogue data are needed for Green Point, and will be collected concurrently on specific tidal days. 

·         Maximum currents at Neah Bay and Whiskey Creek are likely stronger than necessary for pen culture and can be viewed as an impediment to some existing pen designs, although within the range of conditions previously experienced for Ocean Spar type cages.

Remaining Study Issues:

·         An inventory of existing shore support facilities needs to be completed which will include a description of boat launches, marinas, commercial docks, etc.  This information is generally known, but needs to be quantified.

·         Navigation lanes for ships are well defined in the Strait, but fishing areas and transit routes by other small vessels also needs to be quantified.

·         Bottom substrate is already known to be very coarse (sand and cobble) at Whiskey Creek and Offshore of Neah Bay, but inspection of conditions near Green Point should be conducted using video and/or grab sampling for grain size.

·         There is a need for more current meter (ADCP) data at Green Point as the available data is limited to an inappropriate tidal cycle period. Additional drogue surveys could be accomplished at the same time over a complete flood and ebb tide during more average conditions.

·         We have some physiological literature regarding alternative species such as black cod, but some of the information is dated and there is a need to integrate it with newer observations from local and British Columbia researchers.

·         Sea Surface Temperature images from the low DO period of 2001 and several prior years should be reviewed to see if the mid Strait area is consistently the lowest water temperature area.  This could be a qualitative analysis.

·         Modeling studies of nutrients, algal and DO effects are not completed yet, but will be later this year.

Figures in Order of Citation Above:

Figure 1 .  Location map showing primary study zones in western (box on left) and central Juan de Fuca Strait (box on right), target zones in italics 1) offshore of Neah Bay, 2) in vicinity of Whiskey Creek to Pillar Point and 3) Green Point.   Also shown are existing net-pen sites in Port Angeles Harbor and Cypress Island.   (Base map from Thompson, 1981).

Figure 2 .   Neah Bay Study area, width of map is 9.3 km.  Approximate siting area shown in red circle.

Figure 3 .  Whiskey Creek Study Area, central Strait.  Width of section shown is 12. 1 km

Approximate siting area shown in red circle, with arrow pointing to Ocean Spar test cage location from the early 1990s.

Figure 4 .  Green Point Study area east of Port Angeles Harbor.  Width of  map is 20.2 km.

Approximate siting area shown in red circle. 

Figure 5.   Cypress Island Daily average and range dissolved oxygen and water temperature with red arrows showing center of neap tide action.

Note in Figure 5 how periods of neap tidal exchange generally coincide with increased water temperature and DO.  This is a probably a result of a mixture of interrelated factors that are linked to changes of vertical mixing of deep water toward the surface.  During large tidal exchanges the deeper water masses are forced upward by uneven bathymetric features such as sills or headlands.  During neap periods, less mixing occurs and solar heated surface waters add to the stability of the water column, resulting in enhanced phytoplankton production.  The relative contribution of these factors, upwelling and DO production by algae can not be exactly quantified with our available resources.

There is considerable anecdotal evidence that harmful algae blooms are more likely to occur during neap tidal periods, and it is well established that many microflagellates and dinoflagellate are able to tolerate or even prosper in such conditions compared to other phytoplankton taxa.  As phytoplankton biomass increases, oxygen production occurs concurrently.  This neap tide phenomenon is common knowledge among fish farmers in the affected areas and commonly used as a risk factor in monitoring and management decisions.

Figure 6.  Comparison of composite near surface DO for key sampling points in the Strait of Juan de Fuca.

Figure 7.  Comparison of mean daily dissolved oxygen at Cypress Island versus composite of Neah Bay, Whiskey Creek and Port Angeles on same days in 2002.  Error bars represent range of 3 per day measurements at Cypress Island or range of single profiles among sites for the Strait.

Figure 8.  Skagit river discharge near Mount Vernon, Washington from July 2001 to May 2003 with bracket noting end of year 2000-2001 drought.   Figure based on data from USGS, Tacoma WA. (Due to html conversion the following data does not show on graph --July 2001 through October 2001 was below normal. Mid-april 2002 thorugh October 2002 was normal or greater.)

(Due to html conversion the following data does not appear: Relatively more upwelling during 09/01)

Figure 9.  Coastal upwelling index for the Washington coast near LaPush (48˚N) in 2001 (above) and 2002 (below).  (Due to html conversion the following data does not appear: Relatively less upwelling from before 09/01 through 11/01) 

Figure 10.  Sea surface temperature image and data from August 27, 2002 Strait of Juan de Fuca.

Graphs on the left are perpendicular to shore transects, graphs on right are a series of parallel near shore transects through the entire Strait near the US shore.  See full report for details.

Figure 11.  Sea surface temperature image and data from Sept. 5, 2002 Strait of Juan de Fuc

Figure 13.  Sea surface temperature image and data from Sept. 24, 2002 Strait of Juan de Fuca

Table 1.  Nearshore water temperatures in degrees C taken from 2 to 3 km offshore of coastline or spit, in the case of Ediz Hook and Dungeness Spit.  Rank: best = 1, least = 5, red color = highest, blue = coolest.

North is purple, east is blue, south is green, west is red, see index below

(Note subsurface maximum velocity)

(Note above general easterly flow during flood tide stage, but some indication of surface variation.)

Figure 14.  Example of Neah Bay ADCP contour plots: velocity in meters/sec above, direction in degrees true above.

Line: 003 (perpendicular to shore) Nov 22/02 1103PST      1 m/sec ~ 2 knots

 48 22.3217                                                                                                                                                                          48 22.6271

124 34.0760                     purple and blue are slower, yellow to red are fastest, see index below                  124 33.7347 

Note stronger currents near surface in 20 m depth, generally homogeneous elsewhere

Figure 15.  Example of Green Point ADCP contour plots.

Line: 006 (perpendicular to shore, starting at mooring) Nov 22/02 1650PST   Note velocity scale with lower maximum

  48 07.8227                                                                                                                                                                  48 08.1055

123 20.1806                                                                                                                                                                123 20.1171

Note cluster of higher velocity cells nearer shore on right of chart above. Note less current at depth over edge of drop off, siting in 18 to 30 m depth might provide more than adequate velocity above.

Figure 16.  Example of Whiskey Creek ADCP contour plots. Note consistency of flow, with slight shift at depth.

Line: 009 (perpendicular to shore, SE to NW direction) Nov 23/02 0918PST

  48 10.8157                                                                                                                                                                    48 09.5804

123 47.4873                                                                                                                                                                      123 46.7877

Figure 17.  Current meter velocity in cm/s at 5 m depth offshore of Neah Bay at S4 meter location.

Figure 18.   Wave frequency (time period or Tp in seconds) and significant height (Hs in meters) for S4 meter deployed offshore of Neah Bay.   (Portion of record during a series of winter storms).

Figure 19.  Neah Bay Offshore:  Initial releases  offshore ~ 65’ depth near Scallop Culture area at beginning of flood tide.

(Example of work product from full annual report)

Shallow drogue entering Neah Bay and slowed down (0.2 m/s) but deeper drogue skirted west side of Waadhah Island and kelp beds at an average of 0.33 m/s, see Appendix B for more data.

Shallow 1 m Drogue:  ^{___________________}

Deeper  5 m Drogue:  ---------------------

Figure 20.  Neah Bay Offshore:  Releases at 76’ depth at 15:07 hr for 1 m and 5 m drogues.

Similar to above, but faster, averaging 0.62 m/s for both depths

Figure 21. Green Point, initial releases at 50 and 60’ depth. 

Both 1 m drogues traveling at an average velocity of ~ 0.4 m/s. 

Figure 22.  Whiskey Creek, releases at 11:40 AM in 65’, 75’ and 93’ depths.

One each 1 m drogues at each location and a 5 m drogue at the 75’ deep station. Average velocities at 65’ depth 0.6 m/s.  75’ depth drogues both about 0.55 m/s and 93’ depth area drogue averaged 0.46 m/s

References Cited

NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado,

 USA, from their Web site at http://www.cdc.noaa.gov/

Rensel, J.E. and J.R.M. Forster.  2002a. Strait of Juan de Fuca, offshore finfish mariculture

 Literature review and preliminary field results.  Prepared for U.S. National Marine Fisheries Service, Office of Oceanic and Atmospheric Research.   87 pp.

Rensel, J.E. and J.R.M. Forster.  2002b.  Offshore Mariculture in the Strait of Juan de Fuca,

Year one study report.  Prepared for U.S. National Marine Fisheries Service, Office of Oceanic and Atmospheric Research.   5 pp.

Rensel, J.E. and J.R.M. Forster.  2003.  Strait of Juan de Fuca, offshore finfish mariculture: Feasibility Study, Data Report, Year two.   Prepared for U.S. National Marine Fisheries Service, Office of Oceanic and Atmospheric Research.  71 pp.

Thomson, R.E.  1981.  Oceanography of the British Columbia Coast.   Canadian Special Publications of Fisheries and Aquatic Sciences 56.  Dept. of Fisheries and Oceans, IOS, Sidney B.C. and Ottawa.

Acknowledgments

This report was prepared in cooperation with D. Woodruff and  N. Evans of the Battelle Marine Sciences Laboratory, Sequim, Washington.   Data were also provided by C. Coomes and K. FitzGerald of Evans Hamilton Inc., Seattle, Washington. J. Schmitt of Whiskey Creek Resort provided assistance with vessels and moorings.  The Makah Tribe provided similar support in their area.   Extensive data, cooperation and field support were also provided by Cypress Island Inc. staff at Cypress Island and Port Angeles Harbor.   We sincerely thank the subcontractors and cooperators in this venture. This report was prepared with funds provided by NOAA, Office of Oceanic and Atmospheric Research, grant # NA16RG1592.

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