Shoreline Habitats

Defining and describing shore types

1990 publication cover The shoreline classes are derived from the publication “A Marine and Estuarine Habitat Classification System for Washington State” (Dethier, 1990). This classification effort, created for the Washington Natural Heritage Program, had the purpose of providing a system for identifying and describing marine and estuarine areas in a way to allow the eventual selection and ranking of sites for marine preserves. It also was designed to aid in the state’s efforts to create distinctive mapping units for shorelines. It needed to be compatible with National Wetland Inventory maps, and thus to “crosswalk” to the classification scheme of Cowardin et al. (1979). However, the NWI system lacked key parameters necessary for effectively classifying marine and estuarine habitats, especially a way to categorize energy (wave exposure), and a more detailed way of categorizing sediment types than exists in the NWI system.

The mapped shoreline classes are derived from the “ShoreZone” project, for which the entire shoreline of Washington state was flown during low tides between 1997 and 1999. Mapping was done from a helicopter, with georeferenced oblique aerial video imaging and synchronous narration of geological and biological features. The aerial imagery was then converted to repeatable classes of data (shore units), including both spatial representation that fixes the information on maps and attribute representation that classifies data into a classification system. Both geological and biological attributes were mapped and classified. The ShoreZone classification system is somewhat different than the system in Dethier (1990), e.g. it differentiates substrates across different zones of the shoreline, has somewhat different definitions of wave exposure and the marine/estuarine boundary, etc. The mapped units here (“Dethier Class”) are a hybrid of these two systems, and as such they match neither classification system perfectly. Thus some sites are considered “estuarine” in one system and “marine” in the other, or be in different wave exposure categories (e.g., semi-exposed vs semi-protected) in the two systems. As in any attempt to force nature into categories, all designations are approximate. Users of the system will undoubtedly find sites that they know well that do not “fit” into the Shore Class assigned.

One of the difficulties in assigning a set of physical descriptors to any piece of shoreline is that even within a small length of beach, the physical environment may differ substantially across the beach face. For example, commonly in Puget Sound the upper and middle beach face is relatively steep and a mix of sand and gravel, but then there is a slope break near the low water mark and sometimes a band of cobble. Classifying such beaches as one substrate type is thus difficult. In general, if Puget Sound beaches have such cobble they will be categorized as “mixed coarse”, i.e. the assigned class tries to account for such important habitat variation.

Estuarine vs. marine

Many areas in the Salish Sea are difficult to categorize as either Estuarine or Marine. In these transition areas, salinities are generally high (> 25 ppt) and the assemblages resemble those in truly marine waters, but surface salinities occasionally drop lower than this, and circulation and nutrient levels are influenced by estuarine processes. The San Juan Islands fall into this category. Extensive turbulent mixing combined with strong tidal flow from Juan de Fuca Strait generally keep salinities high, but the strong influence of the Fraser River from the north occasionally causes large drops in surface salinities, and areas to the east are influenced by freshwater runoff into Bellingham, Padilla, and Skagit Bays. Rather than rely on a purely salinity-based Marine/ Estuarine cutoff for this area (which would require arbitrary definition not only of a salinity level but also a frequency for this level of intrusion), we have drawn a geographic boundary for this transition through Rosario Strait. Areas to the east of a line from Green Point (Fidalgo Island) to Lawrence Point (Orcas Island) are considered Estuarine, as are all of the Strait of Georgia and the San Juans north of Orcas. Areas to the west are Marine (including islands on both sides of Haro Strait), as is the west side of Whidbey Island down to Admiralty Head. To the east of Deception Pass, and to the south and east of Admiralty Head (and south of Point Wilson on the Quimper Peninsula) is Puget Sound proper, which is considered to be entirely estuarine.

In the “Marine” areas outside this invisible line there clearly exist some estuarine pockets, e.g. Dungeness Bay (Dungeness River) and Sequim Bay (enclosed, with stream input). There is variation in some cases between how this parameter is mapped in ShoreZone vs. the Dethier classification system, e.g. in Westcott Bay on San Juan Island (mapped as estuarine in Shorezone, but considered marine by Dethier because of lack of freshwater input).

Defining diagnostic and common species: caveats

In marine and estuarine systems, a limited set of physical parameters – substratum types, wave or current energy, salinity, and depth or elevation – strongly constrain the distributions and interactions of plants and animals. The hierarchy of physical factors used in the mapped shore classes gives a moderate degree of predictive power about the organisms present. Based on this moderate predictability, each shore class has a list of associated plant and/or animal species that could be present. “Diagnostic” species are those that could be considered to be characteristic of a given shore class, i.e. are almost always found in sites of that type. “Common” associates are those organisms often found in such shore types but also seen in other sorts of sites. However, it is important that users realize that actual inventories of organisms at particular beaches around the state are limited; thus finding lists of species for a particular point on a map simply means that the conditions at that site are appropriate for those species, or at least have been in the past. This caveat is especially true for the listed "VEC common associates" (Valued Ecosystem Components) – these are additional species considered “valuable” by the public that could be found in that habitat type, but confidence about their actual presence is low (or otherwise they would already have been listed as 'common').

Notes on diagnostic fish additions

  • Diagnostic fish include those identified by expert judgement drawn from published and unpublished data from Puget Sound on species determined to be associated with discrete nearshore ecosystems. By diagnostic, we are including species that area predictably characteristic of their described Dethier habitat, but not species that intermittently occupy a wide variety of nearshore ecosystems. Thus, forage fishes, juvenile salmon and other highly transient or migratory fishes are not included as diagnostic because they occur over diverse Puget Sound shorlines. Accordingly, this list is restricted predominantly to fish that are resident at an extended period in their life history, or throughout their life history, rather than those species whose occurrence cannot be described as obligate. We also tended to identify species that occurred in their respective habitats in the most seasons rather than those that were seasonally ephemeral.
  • Although analysis to identify diagnostic species was typically based on examination of descriptive data, in several cases (e.g., MESA data) we either used existing quantitative community analyses (e.g., Wingert and Miller 1979) or conducted multivariate analysis (e.g., non-metric multidimensional scaling, NMDS, in PRIMER) to more quantitatively examing similarities in fish fauna among different shoreline sites. This analysis was greatly facilitated by Jason Toft, SAFS/UW.
  • It should be acknowledged that the ShoreZone classification are somewhat coarse resolution and do not capture fine-scale variations in both abiotic and biotic characteristics of the shoreline or in zoogeographic gradients in the flora and fauna. For instance, eelgrass (Zostera spp.), macroalgae (e.g., Ulvoids) and kelps may occur in small patches and not represented in the ShoreZone class, but still account for the occurrence of fish that are predominantly associated with those fine-scale habitats. Furthermore, many species are arrayed along zoogeographic gradients not defined by ShoreZone. For instance, certain species of poachers, sculpins, greenlings and snailfishes tend to be more likely to be encountered in northern Puget Sound than southern Puget Sound, and vice vesa, in exactly the same ShoreZone class.
  • Accordingly, while we universally adopt the ShoreZone classifications, we have not entirely adhered to matching the fish species composition data to the ShoreZone classification at the documented sampling site. Because of very spatially-explicit collection requirements, variations between upper and lower (e.g., low tide) characteristics, our knowledge of the fishes’ habitat associations sometimes varied from the more broadly mapped ShoreZone classification. In those cases, we identified the more appopriate ShoreZone class rather than necessarily the mapped class.

Data sources

  • Nearshore Fish [WDNR studies in northern Puget Sound/San Juan Islands; 1974-1977)
    • Miller, B. S., C. A. Simenstad, and L. L. Moulton. 1976. Puget Sound Baseline Program:  Nearshore Fish Survey, Annual Report, July 1974 ‑ September 1975, to Washington State Department of Ecology. Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑7604. 203 pp.
    • Miller, B. S., C. A. Simenstad, L. L. Moulton, W. A. Karp, K. L. Fresh, F. C. Funk, and S. F. Borton. 1977. Puget Sound Baseline Program: Nearshore Fish Survey.  Final Report, July 1974 ‑ June 1977. Fish. Res. Inst., Univ. Wash., Seattle, WA.  FRI‑UW‑7710.
  • MESA [NOAA studies in Strait of Juan de Fuca and northern Puget Sound; 1976-1979]
    • Simenstad, C. A., B. S. Miller, J. N. Cross, K. L. Fresh, N. S. Steinfort, and J. C. Fegley. 1977. Nearshore fish and macro­invertebrate assemblages along the Strait of Juan de Fuca in­cluding food habits of nearshore fish.  Annu. Report, contract No. 03‑6‑022‑335185 to NOAA, MESA Puget Sound Office.  Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑7729.  Also NOAA Tech.   Memo. ERL MESA‑20.  144 pp.
    • Cross, J. N., K. L. Fresh, B. S. Miller, C. A. Simenstad, S. N. Steinfort, and J. C. Fegley. 1978. Nearshore fish and macro­invertebrate assemblages along the Strait of Juan de Fuca in­cluding food habits of the common nearshore fish:  Report of two years' sampling.  Annual Rep. to NOAA, MESA Puget Sound Office. Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑7718.  Also      NOAA Tech. Memo. ERL MESA‑32.  188 pp.
    • Simenstad, C. A., B. S. Miller, C. F. Nyblade, K. Thornburgh, and L. J. Bledsoe. 1979. Food web relationships of northern Puget Sound and the Strait of Juan de Fuca: A synthesis of the available knowledge. EPA DOC Research Report EPA‑600/7‑79‑259 (Also Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑7914). 335 pp.
    • Miller, B. S., C. A. Simenstad, J. N. Cross, and K. L. Fresh. 1980. Nearshore fish and macroinvertebrate assemblages along the Strait of Juan de Fuca including food habits of the common nearshore fish. Final Contract Report to NOAA/MESA Puget Sound Project. EPA DOC Research Report EPA‑600/7‑80‑027. (Also Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑8001) 211 pp.
  • Nisqually Reach [1977-978]
    • Fresh, K. L., D. Rabin, C. A. Simenstad, E. O. Salo, K. Garrison, and L. Mathisen. 1978. Fish ecology studies in the Nisqually Reach area of southern Puget Sound, Washington. Annual Prog. Rep., March 1977 ‑ June 1978, to Weyerhaeuser Company. Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑7812. 151 pp.
    • Fresh, K. L., D. Rabin, C. A. Simenstad, E. O. Salo, K. Garrison, and L. Matheson. 1979. Fish ecology studies in the Nisqually Reach area of southern Puget Sound, Washington. Final Rep. to Weyer­haeuser Company. Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI‑UW‑7904. 229 pp.
  • Seahurst Bight Studies [1982-1984]
    • Thom, R., R. Albright, C. Simenstad, J. Hampel, J. Cordell, and K. Chew. 1984. Intertidal and shallow subtidal benthic ecology. Vol. IV in K. K. Chew and Q. J. Stober (eds.), Renton sewage treatment plant study: Seahurst baseline study. FRI-UW-8413, Final Rep. to Municipal. Metro. Seattle, Fish. Res. Inst., Univ. Wash, Seattle, WA. 172 pp.
  • Neah Bay [USAEC studies, 1987-1988]
    • Simenstad, C. A., R. M. Thom, K. A. Kuzis, J. R. Cordell, and D. K. Shreffler. 1988. Nearshore community studies of Neah Bay, Washington. FRI-UW-8811, Final Rep. to U.S. Army Corps of Engineers, Seattle Dist., Fish. Res. Inst., Univ. Wash., Seattle, WA. 200 pp.
  • Padilla Bay [PBNERR studies; 1986-1987]
    • Simenstad, C. A., J. R. Cordell, R. C. Wissmar, K. L. Fresh, S. Schroder, M. Carr, and M. Berg. 1988. Assemblages structure, microhabitat distribution, and food web linkages of epibenthic crustaceans in Padilla Bay National Estuarine Research Reserve, Washington. NOAA Tech. Rep. Ser. OCRM/MEMD, FRI-UW-8813, Fish. Res. Inst., Univ. Wash., Seattle, WA. 60 pp.
  • General Puget Sound [various studies]
    • DeLacy, A. C., and T. S. English. 1954. Variations in beach seine samples caused by net length and repeated hauls. Ecology 35:18-20.
    • Fresh, K. L., D. Rabin, C. A. Simenstad, E. O. Salo, K. Garrison, and L. Mathisen. 1978. Fish ecology studies in the Nisqually Reach area of southern Puget Sound, Washington. Annual Prog. Rep., March 1977   June 1978, to Weyerhaeuser Company. Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI UW 7812. 151 pp.
    • Fresh, K. L., D. Rabin, C. A. Simenstad, E. O. Salo, K. Garrison, and L. Matheson. 1979. Fish ecology studies in the Nisqually Reach area of southern Puget Sound, Washington. Final Rep. to Weyer¬haeuser Company. Fish. Res. Inst., Univ. Wash., Seattle, WA. FRI UW 7904. 229 pp.
    • Wingert, R. C., and B. S. Miller. 1979. Distributional analysis of nearshore and demersal fish species groups and nearshore fish habitat associations in Puget Sound. FRI-UW-7901, Fish. Res. Inst., School Fish., Univ. Washington, Seattle, WA. 110 pp.
    • Donnelly, R. F., B. S. Miller, R. R. Lauth and J. Shriner. 1984. Fish ecology, Vol. VI, Sect. 7 in K. K. Chew and Q. J. Stober, Renton Sewage Treatment Plant Project, Seahurst Baseline Study. FRI-UW-8413, Fish. Res. Inst., School Fish., Univ. Wash., Seattle, WA. 271 pp.
    • Hiss, J. M. 1994. Migration of juvenile pink salmon (Oncorhynchus gorbuscha) through Dungeness Bay, Clallam County, Washington. US Fish WIldl. Serv., Western Wash. Fish. Res. Off., Olympia, WA. 20 pp.
    • Thom, R. M., C. A. Simenstad, J. R. Cordell and E. O. Salo. 1989. Fish and their epibenthic prey in a marina and adjacent mudflats and eelgrass meadow in a small estuarine bay. FRI-UW-8901, Fish. Res. Inst., School Fish., Univ. Washington, Seattle, WA. 27 pp.
    • Miller, B. S., L. L. Moulton, and J. H. Stadler. 1991. Long-term trends in Puget Sound marine fishes: Selected data sets. FRI-UW-9105 and EPA-910/9-910010, Fish. Res. Inst., School Fish., Univ. Washington, Seattle, WA. 38 pp.
    • Simenstad, C. A., J. R. Cordell, K. L. Fresh, and M. Carr. 1995. Trophic linkages from epibenthic crustaceans in littoral flat habitats: Seasonal and regional comparisons. Wash. State Dept. Ecology, Padilla Bay Natl. Est. Res. Res., Mount Vernon, WA. 51 pp plus 28 figures. Padilla Bay National Estuarine Research Reserve Reprint Series No. 35.]
    • Pfister, C. A. 1996. The role and importance of recruitment variability to a guild of tide pool fishes. Ecology 77:1928-1941.
    • Beamer, E., C. Rice, R. Henderson, K. Fresh and M. Rowse. 2007. Taxonomic composition of fish assemblages, and density and size of juvenile Chinook salmon in the greater Skagit River estuary, field sampling and data summary report. Rept. prepared for US Army Corps of Engineers by Skagit River System Cooperative and National Marine Fisheries Service—Northwest Fisheries Science Center. 86 pp.
    • Toft, J.D., J. R. Cordell, C. A. Simenstad, and L. A. Stamatiou. 2007. Fish distribution, abundance and behavior along city shoreline types in Puget Sound. N. Am. J. Fish. Mgmt. 27:465-480.

Site classifications

  • 2: Marine, intertidal, bedrock, partially exposed eulittoral = Midway Rocks, Waadah Island, Slip Point and Observatory Point, Strait of Juan de Fuca
  • 18: Marine, intertidal, mixed coarse, partially exposed, eulittoral = West Beach, Whidbey Island; Beckett Point, Discovery Bay
  • 19: Marine, intertidal, mixed coarse, semi-protected, eulittoral = Port Williams, Sequim Bay
  • 22: Marine, intertidal, gravel, partially exposed, eulittoral = South Beach and  Deadman Bay, San Juan Island; North Beach, Port Townsend; Twin Rivers and Dungeness Spit, Strait of Juan de Fuca
  • 23: Marine, intertidal, gravel, semi-protected, eulittoral = Morse Creek, Strait of Juan de Fuca
  • 26: Marine, intertidal, sand, partially exposed, eulittoral = Kydaka Beach, Strait of Juan de Fuca; Eagle Cove, San Juan Island
  • 27: Marine, intertidal, sand, semi-protected, eulittoral = Neah Bay, Strait of Juan de Fuca
  • 28: Marine, intertidal, sand, protected, eulittoral = Jamestown, Discovery Bay
  • 31: Marine, intertidal, mixed fine, semi-protected, eulittoral = Alexander's Beach, Fidalgo Island
  • 32: Marine, intertidal, mixed fine, protected, eulittoral = Westcott Bay, San Juan Island
  • 65: Estuarine, intertidal, mixed coarse, open, eulittoral = Guemes Island SE
  • 66: Estuarine, intertidal, mixed coarse, partly exposed = Shannon Point, Guemes Island NE, Legoe Bay, Cherry Point, Seahurst, Point Pully (Three Tree Point), Aquarium (NE Vashon Park), Tramp Harbor, Saltwater State Park, Tatsolo Point
    • 68:  Estuarine, intertidal, mixed coarse, channel/slough, eulittoral = inside Dungeness Spit
    • 69: Estuarine, intertidal, gravel, open, eulittoral = Point No Point
    • 70: Estuarine, intertidal, gravel, partly enclosed, eulittoral = Port Townsend Bay, Kilisut Harbor, Indian Island
  • 71: Estuarine, intertidal, gravel, lagoon, eulittoral = Fidalgo Bay
  • 74: Estuarine, intertidal, sand, partly enclosed, eulittoral = Birch Bay, Alki Point, Golden Gardens, West Point, Alki Point, Dumas Bay, Dupont Dock, De Wolf Bight, Thompson Cove, Sandy Bay/Point
  • 78: Estuarine, intertidal, mixed fine, partly enclosed, eulittoral = Drayton Harbor, East Oro Bay
  • 82: Estuarine, intertidal, mud, partly enclosed, eulittoral = Padilla Bay


Chart: Local shoreline changes in King County (2012-13). Source: King County, 2014

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