SHOREZONE LITERATURE REVIEW - CONCLUSIONS & RECOMMENDATIONS|
Conclusions and Recommendations
As expected, analysis of the literature collected for this review has both answered questions, and revealed new questions. The following will be a summary of the findings of this review arranged in two categories: what the review tells us, and what the review does not tell us.
What the literature review tells us.
Most chinook salmon enter Lake Washington as fry from January through March; they are closely oriented to the shoreline during this period, preferring shallow, sandy beaches. A second wave enters the lake as smolts in May and June. Smolt outmigration peaks in May and June, but extends at least through August. The majority of coho salmon enter the lake as smolts in May and June.
The primary predator of juvenile salmonids in Lake Washington is cutthroat trout. Their distribution closely overlaps that of chinook fry, subjecting age-0+ chinook to cutthroat predation for the duration of their rearing and migration.
The distributions of bass (smallmouth and largemouth) overlap that of chinook juveniles, from April through the end of smolt outmigration.
The majority of known bass predation on juvenile salmonids occurs in the Ship Canal. Smallmouth bass are the primary predator, preying most heavily on chinook juveniles due to their small size relative to sockeye and coho yearlings.
Bass are structurally oriented for both spawning and foraging, and smallmouth bass may prefer artificial structures such as piles for nest sites. Both species will utilize artificial structures in lieu of natural structure, and piers may concentrate bass in systems that lack natural structure (such as Lakes Washington, Sammamish and Union).
Small prey fish (i.e., chinook and coho fry) require complex habitat such as rootwads, undercut banks, overhanging vegetation, and CWD, and also shallow water as refuge habitat from the numerous predators within the Lake Washington system.
Piers are structurally simple, lacking the complexity necessary to function as prey-refuge habitat. Thus, they confer an advantage to predatory fish and birds over vulnerable juvenile salmonids.
Bulkheads are also structurally simple relative to undisturbed shorelines. Bulkhead construction generally entails the permanent removal of CWD and other complex features such as shoreline vegetation, which eliminates the sources of future CWD. Bulkheads waterward of OHW eliminate shallow-water refuge and foraging habitat of juvenile salmonids. Bulkheads with large interstitial spaces provide concealment habitat for sculpin, which prey upon juvenile chinook. Chinook fry appear to avoid bulkheads, which may affect their dispersal.
Shorezone development, and specifically the proliferation of bulkheads and bulkheads in combination with piers, consistently results in a reduction of fish and invertebrate diversity and the dominance of the fish assemblage by disturbance-tolerant species (centrarchids - primarily smallmouth bass), and the extirpation of rare species.
Bulkheads interrupt the recruitment and transport of native sediment to lakes, resulting in both local and along-shore erosion. Piers also disrupt sediment transport. The resultant changes in sediment composition and distribution may affect bass and salmonid spawning (as well as other species), and could also affect the distribution and abundance of invertebrate prey items of juvenile salmonids.
Piers reduce primary productivity by both phytoplankton, and macro- and micro-fauna. The amount of reduction is a function of the reduction in light intensity by the structure.
Removal of shoreline vegetation can reduce the allocthonous input (terrestrial insects and detritus) to the lake, ultimately affecting productivity.
Sediment and water contamination can result from leaching of PAHs and heavy metals from treated wood. Hydrocarbon input from two-stroke watercraft engines can be a significant factor in water quality reductions in lakes. However, in urban drainages, and Lake Washington in particular, outboard motors contribute less than 1 percent of PAH input. Chinook smolts exposed to an estuary contaminated with heavy metals and PAHs exhibited suppressed immune responses.
Artificial lighting retards migratory progress of sockeye fry, subjecting them to increased predation. Lights from industrial areas in south Lake Washington facilitate nocturnal foraging by piscivorous birds.
Pile driving can affect the distribution and behavior of juvenile salmonids in the marine environment over long distances, and appears to produce a habituation to the sound that could prevent a fish from sensing an approaching predator.
Minor turbidity increases can cause significant reductions in lake productivity, and produce sublethal effects in salmonids that could reduce their fitness and survival. Acute exposure to high turbidity can be lethal for salmonids.
Boating is not an environmentally benign activity. Potential impacts range from spreading exotic species of plants and plankton to physical injury or death to fish.
The artificial water level regime maintained in Lake Washington for operation of the Ballard locks during boating season may inhibit the establishment of emergent vegetation along the shoreline.
Emergent vegetation can be an effective barrier for attenuation of wave energy.
What the literature review does not tell us:
How do juvenile salmonids respond to piers, bulkheads, and other artificial structures in local lakes (i.e., do they seek or avoid them, will they swim under or go around)? Is response size-dependent? Do variations in design (configuration, materials) affect prey response to structures?
Is there a relationship between piers and predation on juvenile salmonids (by all predators, but especially bass and cutthroat, and avian predators) in local lakes? How are the structures utilized by the various predators?
Which characteristics or combination of characteristics (shade, cover, structure, etc.) of piers attract bass (or other predators) in local lakes? How do variations in design (configuration, materials) affect predator attraction?
Do prisms and grating change predator or prey response to piers? How effectively do they reduce shading in situ?
How do bulkheads and piers affect sediment distribution/composition and benthic invertebrate distribution and abundance in local lakes?
How does pier lighting affect the behavior of chinook fry and their predators in Lake Washington and Lake Sammamish, and ultimately the predation rate on chinook fry?
How do juvenile salmonids and their prey, and adult salmonids respond to drop-hammer and vibratory pile driving in lakes?
What are the cumulative impacts of overwater coverage on total lake productivity from the existing structures on Lakes Washington, Sammamish, and Union?
How do juvenile salmonids in local lakes respond to temporary construction-related turbidity?
What is the current contribution of two-stroke marine engine emissions to PAH contamination in local lakes? How is the productivity of the lakes, and the health of fish, being affected?
How pervasive is the use of dock-cleaning chemicals by homeowners around local lakes, and what chemicals are being used? What hazard does this chemical use pose to fish? Same questions for lawn-care products.
How do juvenile and adult salmonids respond to local boating and swimming activity?
How do changes in sediment distribution/composition affect populations of bass?
With these answers and questions, we have a framework for directing our future research efforts, and for determining our regulatory responsibilities.
These recommendations reflect a conservative approach based on the significant findings and uncertainties identified in the literature review. The most important point of this review is the verification of the intuitive relationship between shorezone development and the loss of properly functioning shorezone habitat (including riparian and littoral zones and their interconnection). The dependence on quality shoreline habitat of sensitive juvenile salmonids and the continual onslaught on the quality of that habitat within an urbanizing watershed was juxtaposed throughout the literature reviewed for this report. The ultimate goal of regulatory personnel charged with protecting ESA-listed salmonid species, or other fish species, should be the protection of that species' critical habitat. With that goal in mind, prevention of the continued simplification of shoreline habitat within the lakes of the Tri-County area is the primary recommendation from this report to policy makers and regulators.Secondary recommendations follow:
New bulkheads should not be permitted unless a critical personal property loss can be demonstrated. In most cases, there are soft alternatives to shoreline armoring. If bulkheads are determined necessary, make every effort to pull the structure shoreward of OHW.
Encourage the removal of bulkheads in favor of shoreline restorations [i.e., native emergent and riparian plant species, low-gradient beach (or as appropriate for specific site), native structural elements (CWD, rock) in combination with emergent vegetation for wave energy attenuation]. Such designs have been successfully incorporated into recovery efforts in the Great Lakes (Schollen 1995).
Encourage property owners to retain driftwood and fallen trees on their properties.
Shorezone construction should not occur during the January through June period when juvenile chinook are most likely to be in the littoral zone. More restrictive allowable construction windows would be appropriate in some areas (i.e., Ship Canal, north end of Lake Washington, south end of Lake Washington, and near mouths of spawning tributaries in Lakes Washington and Sammamish). Consider site proximity to a spawning stream or river, and the likely timing of juvenile and adult migration.
Instigate an aggressive bass removal campaign in confined areas, such as the Ship Canal, utilizing unlimited catch restrictions and bounties if necessary.
Consider a "no new piers" policy as the best option for protecting fish and fish habitat. Encourage the use of floats or buoys instead. If politically impractical, see #7 below.
No net increase in overwater coverage should occur in the Lake Washington system - permits for new construction should be contingent on permits for replacement structures. Only replacement structures that demonstrate a reduction in overwater coverage should be permitted. The amount of overwater coverage eliminated from the replacement pier could be held in a "surface area mitigation bank," which new piers would have to draw from. Gradually lower the total net coverage over local lakes.
All piers, both new and replacement structures, should be restricted to a 3.5-foot-wide cantilever bridge that spans the nearshore area to a narrow moorage structure of the minimum size necessary to moor the applicant's boat.Cantilever bridge structures should be grated, and as high off the water as practicable, and moorage structures should be no less than 24 inches above OHW. Floating structures should have maximum light penetration, and be removed annually after boating season.
Prisms and grating should be studied to determine their efficacy at providing sufficient ambient light for macrophyte production under piers. The best products should be utilized in all new or replacement overwater structures to minimize losses of primary productivity.
Minimize the number of piles used in all structures. Study pile dimension to provide evidence for or against mandated pile dimension. Require the removal of existing treated piles if present.
Every shorezone development application should be considered an opportunity for a habitat improvement project. Require shoreline restoration as mitigation for shorezone structures.
Do not permit shoreline or pier lighting unless future studies suggest otherwise.
Discourage the use of pesticides, herbicides, fertilizers, and cleaners, especially near or over the water.
Consider phasing-out sales of two-stroke outboard marine engines.
Aggressively enforce a "no lake-water withdrawal" policy with waterfront property owners.
Future research should focus on the 13 questions in the "what the literature review does not tell us" section. Two studies that could result in a relatively rapid regulatory response would be the determination of the effectiveness of prisms and grating for facilitating macrophyte growth under piers, and a study of the effects of the two methods of pile driving on salmonids in local lakes. Results from each of these studies could be used immediately to determine WDFW Hydraulic Project Approval (HPA) or municipal requirements for pier design and construction methods. Another top priority might be a determination of the response of predators and prey to pier lighting, since having that knowledge could produce a rapid regulatory response.
Studies should be directed at determining the predator population response to shorezone alterations and structures; do these alterations and structures enhance predator abundance or simply concentrate the population in predictable areas? If predator populations are limited by factors other than structure availability, placing additional structures may not increase their abundance.
What is the spatial and temporal correlation between artificial structures, gravel, juvenile salmon and predators? Can cause and effect be demonstrated experimentally (i.e., perform a replicated before-after-control-treatment experiment where piles are introduced in "accretion" and "non-accretion" zones, and monitor for one to two years for changes in substrate and fish use).
Our understanding of how various pier designs affect salmonid/bass (and salmonid/salmonid) interactions remains limited. The basis of bass attraction to piers and piles is poorly understood. Spawning bass are attracted to structures protruding from the substrate, but it is unknown which pier features attract foraging bass. Circumstantial evidence suggests that the amount of shade or the area of overhead coverage provided by a structure is important to foraging bass.
Investigations of bass utilization of structures of various designs are necessary. How salmonids and their predators respond to light-transmitting pier design elements (i.e., prisms, grating), overhead cover, and piles of various diameters requires investigation. Until investigations of prisms and grating are complete, they should not be relied upon as a mitigation measure that reduces bass attraction.
Finally, the summer boating season corresponds with the highest water levels in Lake Washington. Erosion caused by power boating can be severe. The high water levels that occur during the periods of heaviest boat use increase the potential of boat wake-induced erosion damage around the lake. Efforts to restore natural shorelines in Lake Washington will be hindered by artificially maintaining a high summer lake-level. The ecological implications of the continuation of the existing water-level management regime in Lake Washington should be critically examined. Ongoing and Further Study
There are a number of ongoing studies within the Lake Washington system from which results will be available to the public in the near future. Roger Tabor (USFWS) and staff from the Muckleshoot Indian Tribe's Fisheries Department have been studying the predation by largemouth and smallmouth bass and northern pikeminnow on salmon smolts in the Lake Washington Ship Canal and in the Lake proper. Preliminary results from this study were presented at the North Pacific International Chapter-American Fisheries Society meeting from 10 to 12 April 2000, and were included in this document (Tabor et al. 2000). Kurt Fresh (WDFW) is currently studying the timing of entry and distribution of juvenile chinook salmon in Lake Washington; details on the availability of results are pending. Rod Malcom (MITFD) has three reports in preparation:Preferential association of smallmouth bass nests with residential piers and artificial structures in Lake Sammamish, King County, Washington. 1995. Muckleshoot Indian Tribe.
Changes in the number and overwater coverage by residential piers in Lake Sammamish, King County, Washington. 1995. Muckleshoot Indian Tribe.
Changes in the number and overwater coverage by residential piers in Lake Washington, King County, Washington. 1995. Muckleshoot Indian Tribe.
Details on the availability of these reports were not available.
Additional studies on docks and bulkheads may be currently in progress in the region but information was unavailable at the time of publication. Acknowledgments
We thank B. Footen, K. Walter, E. Warner, and R. Malcom of the Muckleshoot Indian Tribe Fisheries Division for assistance in developing the scope of the review, for reviewing an earlier draft of this report, and for sharing information. We also thank K. Fresh, WDFW, and R. Tabor, USFWS for reviewing an earlier draft of this report, and sharing information. We thank A. Myers of The Watershed Company for editorial support. We thank Kit Paulsen, City of Bellevue, for developing the original scope of the project, for functioning as our liaison at the City of Bellevue, for reviewing every draft of this report, and for orchestrating the cooperative effort between The Watershed Company and the University of Washington Cooperative Fish and Wildlife Research Unit.