Chinook Salmon and Houseboats

Sharing an Urban Lake

Introduction

James Fallows, in his article Saving Salmon, or Seattle? pointed out that people who are interested in protecting the salmon use different goals to describe that protection. "…At least three different goals: protecting the fish themselves… against threats to their existence as a species; maintaining fisheries, whose purpose is to allow fishermen to catch and people to eat the fish; and preserving the wild natural environment in which the fish spawn." 8  

Today there is what might be described as a fourth goal, a plan to create a natural habitat for the migrating Chinook salmon from the highly manipulated Lake Washington Ship Canal.

What Makes This Fish Special?

In the late summer and autumn the struggle of the Chinook salmon to return, to reproduce and then die, has found it's way into lore. But the beginning of the Chinook salmon life cycle is perhaps even more fascinating. And it is on the beginning that this article will focus. It is this early stage of life, the migration from fresh to salt water that is of greatest interest to residents on Lake Union and Portage Bay.

• The adult Chinook salmon, after an average of 4-5 years in the ocean, return to somewhere in the Cedar River Watershed or via the Sammamish River to Bear Creek to spawn and die in their natal stream. Chinook prefer to spawn in large fresh water rivers. Thousands of eggs are laid and the Chinook that survive the salmon egg stage pass on to the alevin stage described as "a thread with eyes and an enormous yolk sack." 24  26
• The first month is spent in shallow water and then the fish, now called a fry, may spend several months in quiet pools and growing to about 40-50 mm long. The river reared Chinook juvenile will, as they grow, move into open, faster moving water. 24 26  The fish do not enter Lake Washington at the same time. There are five identified groups: early and late groups from Bear Creek and early and late groupings from the Cedar River. The fifth group is from the Issaquah Hatchery. Each group moves downstream into Lake Washington. These fry rear along the shores of Lake Washington.18
• The smolt stage follows. This is the stage during which the kidneys and gills begin adapting the fish for a saltwater environment. "The most significant process in the juvenile life history of Chinook salmon is smoltification, the physiological and morphological transition from a freshwater to marine existence. The emigration from river to ocean is thought to have evolved as a consequence of differences in food resources and survival probabilities in the two environments."24  By the time the smolts, reach Portage Bay, they have grown to 80-110mm in length.18  During this stage the parr marks of the fry, used as camouflage in fresh water, are replaced. The smolt develops a dark back and light underside, typical of fish in open water.24   The juvenile Chinook prefers deeper water and avoids light.3
• In the Lake Washington Ship Canal (LWSC), the Chinook juveniles seem to be either migrating or rearing. Migrating fish pass through Portage Bay and into the Ship Canal quickly. Rearing smolts are feeding, resting and growing and may linger for many days.

Brief History of the Lake Washington Ship Canal and the Chittenden Locks

Before we consider 'recreating' a Chinook salmon habitat along the LWSC, it is useful to understand how modified this waterway is.  Prior to 1917, the Chinook salmon migrated down high streams and creeks and entered Lake Washington. The only route out of Lake Washington for them was down the Black River, at the south end of the lake, into the Duwamish River and then to the Duwamish Estuary.

The LWSC was completed when the Montlake Cut was opened and Lake Washington dropped 10 feet to the level of Portage Bay. This drop exposed miles of Lake Washington shoreline. That loss of shoreline destroyed the Chinook salmon smolt habitat. The Black River dried up with the 10-foot drop. The Chinook salmon smolts were forced to find a new route to the ocean. Their only exit from Lake Washington to the ocean became the Montlake Cut. Instead of finding a fast moving river leading to tidal creeks and estuaries, the smolts ended up in Portage Bay on the west side of the Montlake Cut. They entered new territory, a canal created from Portage Bay, Lake Union and Salmon Bay. But still there was no ocean, no estuary. Not until they passed through the dangerous Chittenden Locks via the fish ladder and smolt flumes did they reach salt water.

It is hard to believe these first fish did find a way to the sea.  Or perhaps it is not so fantastic. Research shows the Chinook salmon are amazingly adaptable.  For example, 'Ocean-type Juveniles', which these lake reared Chinook are,16 may reach the ocean as early as a month of age. In most river systems these salmonids migrate between 60-150 days after hatching, and reach the ocean in the late summer or autumn of their first year. So what causes this variability? "When environmental conditions are not conducive to sub-yearling emigration, ocean-type Chinook salmon may remain in freshwater for their entire first year."24

As cleaned up as Lake Union and Portage Bay are, threats remain to the Chinook salmon juvenile migrating to the ocean. There is the turbulent water created by heavy boat traffic. This increase, beginning in the spring, coincides with the Chinook salmon smolts downstream migration. On Portage Bay and Lake Union there are few sandy shallow beaches and little pools like the Chinook might have found along creek banks. There aren't many gently sloped banks covered in overhanging trees.  The littoral areas (shallow, submerged shore) with woody debris, under which Chinook juveniles could hide, are not always accessible. Instead there are large and small buildings along the shore and on the water; structures like houseboats, as well as marinas with small crafts and large vessels tied up to docks and piers.  And each day the impact of urban life on a lake becomes more noticeable. There is continuing upland development.  In many areas, steep slopes are supported with bulkheads and rip rap. Some of the predators are non-native, introduced by sport fishermen. The surface temperature of the water is increasing, possibly due to climate change. There are oil spills and storm drain overflows. Garden fertilisers and pesticides contribute to chemical pollution. Exotic water plants, replacing the natural water flora, grow in the shallower waters. Countless hazards threaten the Chinook salmon after they are through the locks and spend the next five plus years swimming up to Alaska and back.  It probably is no surprise that the Puget Sound Chinook salmon was placed on the Threatened Species List in 1999.

The Houseboat Community and the Environment

So, what does all this mean to the houseboat community?  When the first Chinook salmon smolts came through the Montlake Cut, they discovered a houseboat community; in fact there were scores of houseboats on Portage Bay and several hundred houseboats on Lake Union at the beginning of WW1.7   In 1917 there was also a thriving community of boat marinas, water related businesses, boat builders and mills. One early business was the Pacific Ammonia and Chemical Company, located in 1909 on the west side of Lake Union. Old timers report a shoreline crowded with businesses designed to serve boat builders and the houseboat community. By 1943 the Washington State Pollution Commission reported "45 industries were listed adjoining Lake Union…There were 10 machine shops and metal foundries; 10 lumber and plywood mills; 12 fuel and oil storage and service facilities; 8 companies dealing with sand, gravel, concrete or asphalt; the Seattle City Light Power Plant and the Seattle Gas (coal gasification) Plant. The gas plant was listed as one of the worst sources of water pollution." 9 After World War 2 the number of floating homes began to decrease and by 1970 there were 450 left.7   During this time the Chinook salmon continued to migrate through the Ship Canal. Lake cleanup started long before the Chinook salmon began to decline about 20-30 years ago.

In the houseboat community today, residents work on environmental causes such as The Puget Soundkeepers Alliance.  Most houseboaters consider themselves stewards of the lake. They recycle, and avoid using fertilizers and materials toxic to fish. This community, floating on the water, prides itself on living close to the natural world. This is a community of wildlife observers and nature photographers. These observers don't hesitate to report oil spills, and sightings of non-native animals and exotic water plants.  Many houseboaters know the lake upon which they live is far from wild or natural. They understand Lake Union is a severely altered environment surrounded by extensive development.

Early in March 2009 the Floating Homes Association received the City of Seattle's Department of Planning and Development (DPD), Best Available Science 2005 document. This document, prepared by DPD staff, stated that houseboats have a negative impact on Chinook salmon, and that over-water coverage is detrimental to salmon migration through the LWSC. 5   On May 27, 2008 the DPD staff had convened the first meeting of the Citizens Advisory Committee (CAC), made up of lakeshore stakeholders, who were asked to provide input on the Shoreline Master Plan update. This committee is to help shape policy effecting Seattle's shoreline jurisdiction. The Floating Homes Association is represented on the CAC, and has been working to protect and preserve the community while remaining mindful of protecting the threatened Chinook salmon.

Fisheries Research and the Houseboat Community

While gathering this information, it was determined that fisheries studies done in and around LWSC since 2000 would be preferred sources. "I would be careful about applying data from other systems, sometimes it overlaps nicely, but the Lake Washington-Ship Canal is a very modified system, and a unique situation at least around Washington where Chinook rear in a lake." 21   And, Roger Tabor who has conducted a number of studies, cautions, "Little is known of their habitat use in lakes, as Chinook salmon rarely occur in lakes throughout their natural distribution."15   Although a good portion of fisheries research has focused on over-water structures, one extensive review of the literature reported no studies were found assessing the environmental effects of houseboats.1

Based on the science, in what ways does the houseboat community threaten the Chinook salmon?  How great is that threat? If we make changes, to what degree will those changes benefit the fish?  And, how feasible is it for the Floating Homes Community to instigate suggested changes?

What negative Impact does the houseboat community have along the LWSC shoreline?

Seattle DPD has, identified that houseboats

• shade the water.
• interfere with smolts access to the shoreline.  
• provide cover for predators.  
• may impede water circulation.
• contribute to warming surface of the lake.  

One solution, DPD has identified for discussion would decrease the amount of over-water coverage.

1. How much do houseboats shade the shore and water edge?

A study conducted in late October 2002, inventoried and mapped the shoreline along a section of Lake Washington, all of the Ship Canal and a short section of Shilshole Bay.20   The shoreline was studied for types of docks (including over-water platforms), height of docks, armoring (bulkheads, etc), soil composition of shore, shore side plantings, and shading of shore. The results of this study suggest the houseboat community accounts for a small part of over-water structures.  

Inventory of docks were as follows:

These docks, over-water structures and platforms account for shading 17.3 % of shoreline edge.

2. How is over-water coverage detrimental to the Chinook salmon smolt migration through the LWSC? Or, is shading the shore a good or bad thing for the Chinook salmon smolts?   

The trees, shrubs and grasses of a riparian corridor (the interface between land and a stream) has been shown through the dappled shade provided by riparian vegetation, to aid in keeping the water temperature lower. Over-water structures, such as docks, cast definite shadows on the water and larger structures, like houseboats prevent light from ever reaching some areas. However, random daytime surveys produced information that Chinook salmon were always close to some type of structure such as docks or overhanging vegetation.15   Docks are sometimes used by smolts as protection from predators or as a resting place. But, do Chinook salmon smolts go under houseboats? The answer is ambiguous. Some have been observed to occasionally go under houseboats; they may go under a float of 4 feet deep or maybe10 feet deep and other observers have never seen Chinook juveniles go under houseboats. Research does indicate migrating Chinook juveniles often avoid passing under over-water structures, instead they use the periphery of the structure, as was observed at a large over-water condo on Lake Washington.  The edge provided cover for these smolts from bird predators.18

Chinook salmon smolts have been seen to avoid houseboats and docks within 30 feet of the shoreline. "At night Chinook salmon appear to avoid the darkest areas such as locations with overhead structures or overhanging vegetation.  Most likely, Chinook salmon avoid areas with very low light at night to avoid nocturnal predators such as large prickly sculpin which may be more abundant in complex habitats."15   Over-water structures, like houseboats and recreational docks are frequently associated with armouring (bulkheads). Are the juveniles avoiding the over-water structure or avoiding a bulkhead?  "Additional experiments would be useful to test the relationship between Chinook salmon habitat use and other types of shoreline modification, such as various dock designs." 15   Chinook salmon smolt behavior around large over water structures in lakes is not well understood. "This lack of comparative data inhibits firm conclusions being drawn."3

The aversion to large structures and the sharply defined shadow these structures offer may be due to the slow eye adaptation of the Chinook smolts moving from bright sunlight to shadow. It is suggested it may take as long as 20 minutes before the eye adapts, leaving the fish blind for some moments.12   So dappled shade is good, while shade with definite edges is not beneficial to the Chinook salmon smolt.

Light is important for the Chinook salmon smolts. Where there is light, algae will grow, and algae provide a source of food.

3. Do houseboats interfere with juvenile Chinook access to the shoreline?

If this is true, then how has the Chinook salmon survived since the opening of the LWSC?  There are not good records, but there were possibly 300+ houseboats in 1917. And in 1939 there was a rough survey conducted that found 946 houseboats. 7   Vague numbers, but there is evidence that Chinook salmon have lived with the presence of houseboats for 80+ years. Although Chinook salmon smolts may use the littoral area for foraging and rearing, it seems there isn't definitive information on this occurring regularly in Portage Bay. However Tabor suggests that in a recent unpublished study, the juveniles are rearing in Lake Union.18   Littoral area use on Portage Bay may be discouraged by the collection of houseboats along the shore. However, many of those houseboat docks are short, on which three or fewer houseboats are moored. Many of the longer docks appear to have wide channels between docks, which allow Chinook salmon juveniles easy access to the shore.

Until there is more research on lake reared Chinook salmon smolts, one must make conjectures based on the recent studies done in Lake Washington and the LWSC.  Celedonia and Tabor's 2007 study in Lake Washington indicates the fry and fingerlings stay close to the shore during the day in 1-5 m of water. They move into the deeper water at night. But, as they get older and once they go through the Montlake Cut, their behavior changes.3   A variety of behaviors, from migrating quickly through Portage Bay, to a holding pattern during which feeding, resting and rearing takes place.2, 3, 15   It has been noted that some of the juvenile Chinook may spend as much as 4-6 months rearing in Lake Washington.16

There is evidence that differences in Chinook salmon smolt behaviors are related to site conditions, for example the clarity of the water or the inaccessibility to shoreline, physiological conditions (smoltification), external cues or a combination of these factors. 3   Tabor and Piaskowski noticed in 2001, that after May, Chinook salmon smolts still used the shore but appeared to progressively move to deeper water as their size increased. (Tabor & Piaskowski 2001) There is evidence that many Chinook salmon smolts are migrating once they move into the LWSC.  Or perhaps when confronted with less clarity of the water, warmer water, less accessible shore line, they choose not to linger.

4. How significant is the coverage houseboats provide for predators?

The DPD reports, "The numerous docks, piers and bulkheads have significantly altered the lake's shoreline and littoral (shallow shore) habitat. The primary concern regarding these shoreline structures is their potential to increase preferred habitat for predators while reducing shallow water refuge, thus potentially resulting in increased predation on Chinook and other salmon that occupy littoral habitat." 5  As the review of history shows, the shore-line of Lake Union and Portage Bay was altered long before the Chinook salmon entered the LWSC. Although there is evidence that houseboats, dock and piers provide hiding places for predators, other predators, such as the prickly sculpin, lurk on the sandy beaches and in shore-side woody debris. "Piscivorous fishes have their greatest advantage over forage fishes under low light conditions." 3    And, as they grow, the juvenile Chinook avoid the littoral areas, because in shallow, shaded water they are less able to avoid predators.18  Chinook avoidance of over-water structures seems very likely due to the presence of predators. At night the juveniles avoided shallow areas near over-water structures, and were found in deeper water and/or in shallow open areas away from over-water structures. These behaviours were used to avoid the prickly sculpin.18

At least 23 non-native predator fish have been identified in the area. These include largemouth bass, smallmouth bass, yellow perch, rainbow trout, cutthroat trout, and river lamprey. A great loss of Chinook salmon smolts is due to predation. Chinook salmon smolts of 90mm length have become prey for bass as small as 138mm.9  "It is possible that in a highly altered ecosystem like Lake Union and the Lake Washington Ship Canal, reducing predation by exotic species may be as beneficial or more beneficial to the survival of juvenile Chinook salmon than restoration of some of the natural habitat forming processes…" 9    As much as there is concern that houseboats provide shelter for predators, the log floats do provide a source of small prey for the Chinook juveniles.1

5. Do houseboats impede water circulation?

As well as shading the water surface near the shore, it is suggested that houseboats, along with docks and marinas, also impede water circulation.5  Frequently, over-water structures are  associated with armoring of the shore.  It is possible the impediment to water circulation is the bulkhead rather than the houseboat and researchers have suggested this should be studied.

DPD has suggested that deeper flotation under a houseboat may impede water circulation, which could contribute to higher water temperature (see below).

Riparian corridors can slow runoff of precipitation by holding water in plants and in the soil.  This ability regulates the flow of runoff and maintains more constant cooler water temperatures during summer periods. "The vegetation canopy adjacent to streams shields the water from direct sunlight, which moderates extreme temperature fluctuations during summer.  This canopy can be grasses and shrubs for smaller streams, as well as trees and shrubs for larger streams."5

6. Does the presence of houseboats warm the surface water?

Elevated surface water temperatures may contribute to desmolting and residualism (incomplete smolting and/or precocious maturation). It is uncertain if the warmer temperatures of the LWSC contribute to this.3   There is research on Atlantic salmon that suggests fish held at lower temperatures maintained smolt-like characteristics, but fish held at higher temperatures passed through a 'smolt window'.  However, further studies of lake reared Chinook smolts need to be conducted.

How the small, constant community of houseboats contribute to current rising temperatures in the LWSC has not been demonstrated. Instead, it is possible the water coverage from houseboats may help, in a small way, to decrease the surface temperature. There is greater evidence that climate change, or at least the increasing number of warm summer days, is responsible for rising temperatures at the Fremont Bridge and at the Ballard Locks.  The use of a concrete float, in some cases used as living space, has received scrutiny from the DPD. They suggest the heated space, leaches heat into the surrounding water, but no scientific evidence has been presented to support this.

Summary

So what have we learned?

• Over-water structures are considered stressors to the Chinook salmon smolts. Houseboats are a category of over-water structures that cast large shadows with definite borders.
• Research shows the Chinook salmon juvenile eye has slow light to dark adaptation. Diffuse shadows, found at the peripheral edges of houseboat-like structures, have been seen to provide refuge for Chinook salmon juveniles, but predators lurk in the shadows and in the dark that is created by floats.  
• Some research shows that the larger smolts prefer deeper water, but the littoral area remains an important habitat for the rearing smolts.
• Piscivorous fish hide under over-water structures. One predator fish, the smallmouth bass, is a non-native species known to hide under structures such as houseboats. But, an over-water structure provides the Chinook juvenile with access to tiny prey hiding in the uneven surface of submerged logs.
• All houseboat docks have near-shore houseboats that may prevent smaller, rearing smolts access to a sandy littoral area. Long houseboat docks may impede smolt access to the shore. But research indicates as the juvenile matures it prefers deeper water to littoral area.
• The shores of Lake Union and Portage Bay are modified with docks and marinas, not just houseboats. Steep slopes are protected with armouring. The sandy beaches, preferred habitat for Chinook salmon fry and fingerlings, are in short supply.  
• There is no evidence that houseboats impede the circulation of water or contribute to warming conditions of the LWSC.

Conclusions

So should the houseboat community be considered a major factor in the decreasing Chinook salmon population? No. The Chinook salmon and the houseboat community have coexisted for 92 years on this man-made canal.  When the Chinook salmon count declined, houseboat coverage of the lake was half of what it had been in the 1940s.  And the water quality of Lake Union and Portage Bay by the 1980s was the best it had been since before the opening of the LWSC.  

Although houseboat docks account for only 4.4% of the shading of shore and water edge, over-water structures, including houseboat placement along the edge of the lake, is unhelpful for salmon propagation. Lake Union's shoreline has been modified since the late 1800s and was never a natural waterway for migrating salmon. However, houseboats, along with docks and marinas, and other over-water structures, do not enhance the riparian and littoral habitat these fish may need.

Before decisions pertaining to modifications of dock structure, riparian and littoral habitats are made there should be further research. Modifications need to be carefully evaluated for benefit to the Chinook salmon smolt and the feasibility of any change needs to be realistic.

Addendum:

As this report was being written the DPD released information that it will not pursue the goal of reducing individual float size.  The Floating Homes Community representatives continue to work on a final draft that will accommodate the community and will satisfy the DPD.

Bibliography for Chinook Salmon and Houseboats

1.Carrasquero, Jose. Over-water Structures: Fresh Water Issues, White Paper 2001. Herrera Environmental Consulting.

2. Celedonia, Mark & Roger Tabor, et al. Movement and Habitat Use of Chinook Salmon Smolts and Two Predatory Fishes in Lake Washington and the Lake Washington Ship Canal: 2004-2005 Acoustic Tracking Studies. U.S. Fish and Wildlife Services, December 2008. (Funded by King Conservation District and Seattle Public Utilities, City of Seattle.)

3. Celedonia, Mark & Roger Tabor, et al. Movement and Habitat Use of Chinook Salmon Smolts, Northern Pikeminnow, and Smallmouth Bass Near the SR520 Bridge: 2007 Acoustic Tracking Study. U.S. Fish and Wildlife Services, October 2008. (Funded by the Washington State Department of Transportation.)

4. Crowley, Walt. Lake Washington Ship Canal. History Link, July 2001. www.historylink.org

5. Department of Planning & Development, City of Seattle. Environmentally Critical Areas Code Updated: Best Available Science Review, August 2005.

6. Department of Planning & Development, City of Seattle. Shoreline Characterization Report, March 2009.

7. Droker, Howard. Seattle's Unsinkable Houseboats. Watermark Press, Seattle, Washington, 1977.

8. Fallows, James. Saving Salmon, or Seattle? The Atlantic Monthly, Digital Edition, October 2000. (Online version appears in two parts.)

9. Houck, Douglas with Deb Lester & Scott Brewer. Lake Union / Lake Washington Ship Canal System. Seattle's Aquatic Environments: Lake Union / Lake Washington Ship Canal System, 2001. www.centerforlakewashingtonstudies.com/nsr/pdf/LkUnionShipCanal.pdf

10. Kingle, Matthew W. Emerald City, An Environmental History. Yale University Press, New Haven & London 2007.

11. Myers, J.M., R.G. Kope, G.J. Bryant, D. Teel, L.J. Lierheimer, T.C. Wainwright, W.S. Grand, F.W. Waknitz,K. Neely, S.T. Lindley, and R.S. Waples. Status Review of Chinook Salmon from Washington, Idaho, Oregon, and California.1998 U.S. Dept. Commerce. NOAA Tech. Memo. NMFS-NWFSC-35,443. www.nwfsc.noaa.gov/publications/techmemos/tm35

12. Nightingale, Barbara and Charles Simenstad.  Over-water Structures: Marine Issues. Washington Department of Fish and Wildlife, Washington Department of Ecology, Washington Department of Transportation. 2001.

13. Sorensen, Eric. Lake Union: A Reflection. Seattle Times, September 9, 2001.

14. Tabor, Roger. Lake Habitat Preference of Juvenile Chinook in Controlled Experimental Areas: 2003 & 2004. Seattle Public Utilities.

15. Tabor, Roger and Richard Piaskowski. Near-shore Habitat Use by Juvenile Chinook Salmon in Lentic Systems of the Lake Washington Basin.  Annual Report, 2001. U.S. Fish and Wildlife Service.

16. Tabor, Roger, Julie A. Scheurer, Howard A. Gearns, and Eric P. Bixler. Nearshore Habitat  Use By Juvenile Chinook Salmon in Lentic Systems of the Lake Washington Basin, Annual Report, 2002.  U. S. Fish and Wildlife Service, 2004.

17. Tabor, Roger, Mark T. Celedonia, Francine Mejia, Rich M. Piaskowski and David L Low.  Predation of Juvenile Chinook Salmon by Predatory Fishes in Three Areas of Lake Washington Basin. U S Fish and Wildlife Services. 2004.

18. Tabor, Roger. Telephone Communication, March 30, 2009.

19. Toft, J., J Cordell and B Starkhouse.  Salmon Bay Natural Area Pre-Restoration Monitoring 2004, Wetland Ecosystem Team, U of W School of Aquatic and Fisheries Science, Prepared for Seattle Public Utilities, City of Seattle.

20. Toft, J., C. Simenstad, C. Young & L Stamatiou. Inventory and Mapping of City of Seattle Shorelines along Lake Washington, The Ship Canal and Shilshole Bay 2002. Wetland Ecosystem Team, U of W School of Aquatic and Fisheries Science.  Prepared for Seattle Public Utilities, City of Seattle, 2003.

21. Toft, Jason. Personal Communication, February 26, 2009.

22. WRIA 8 Chinook Salmon Conservation Plan, Report finalized 2005. www.govlink.org/watersheds/8/planning/chinook-conservation-plan.aspx

Others:

23. Black River: History of a Lost River.  www.burgesslegacy.org/blackriv.htm

24. Chinook Salmon Facts 1996.  www.psmfc.org/habitat/edu_chinook_facts.html

25. Creek Restoration. Seattle Public Utilities. www.ci.seattle.wa.us/util/About.SPU/Drainage

26. Cyber Salmon: Chinook Salmon Fairbanks Fish and Wildlife Field Office, U.S. Fish and Wildlife Service.  www.cybersalmon.fws.gov/chin.htm  

27. Montlake Cut, Wikipedia.