Fish Creek

A fish & wildlife hotspot

Fish Creek estuary is far from pristine, as shown in the historical series on right. But this resilient little park continues to attract great numbers of fish, birds and mammals from surrounding forests and wetlands. Removed from the noise and bustle of the airport (2 miles north) it remains our best reminder of the peaceful beauty that once characterized the entire Mendenhall Wetlands. Managed for recreation and wildlife by the City and Borough of Juneau, this is a wonderful place to fish, picnic, watch birds, or observe dynamic responses to human and natural disturbances. Here, we offer some pieces of the puzzle of Fish Creek’s history. Why did Fish Creek carve the watershed on Douglas Island? Why is the mud outside Entrance Point a magnet for water birds?

Faults, glaciers, sea levels, streams

Smooth colors show bedrock uplands only thinly covered by glacial deposits. Stippled colors show deeper marine, glacial, alluvial (stream), and colluvial (landslide) deposits. Inset indicates movement on both vertical and horizontal planes along the Fish Creek fault. Horizontal displacement is reflected by offset of the older Silverbow fault. Rock strata tend to dip more steeply northeast of Fish Creek fault. 
At the peak of the great ice age, about 20,000 years ago, all of this scene was covered by southeastward-moving ice about a mile deep, excavating the weaker, more fractured rocks along the Fish Creek fault. This deep gouging explains why Fish Creek is the largest watershed on Douglas Island; all other streams (except Peterson to the west) are short, steep channels dropping directly from ridgetop to beach. (Surficial geology from Miller (1975).   Inset based on Haeussler (1992).)

Geologic faults are gigantic fracture zones along which large masses of earth have moved relative to each other. The Fish Creek fault runs up Admiralty Island’s Oliver Inlet, splits the spine of Douglas Island, then passes beneath Auke Lake before converging with the even larger Gastineau Channel fault. Comparing Fish Creek and Silverbow faults (dashed purple lines on map), can you tell which is older? Hint: look for offset. Answer in caption.

When a slowly melting glacial remnant occupied the basin at today’s Eaglecrest (map, lower left), it compacted the rubble beneath, resulting in poorly drained soils that underlie the boggy habitats of today’s cross-country ski loop. Fish Creek originates in Hilda divide and the downhill ski bowls, flowing northwestward down the line of Fish Creek fault, gaining tributaries en route. On this map, stream color shows channel type: “contained” channels (shades of blue) are confined by bedrock or deep canyons in glacial and marine sediment, as opposed to “flood-plain” channels (orange) that meander freely through broad stream deposits, typically framed by large spruce trees.

By about 14,000 years ago, most of the great ice had melted, but a stagnating glacier remained in the upper Fish Creek basin. Migrating meltwater channels built up an outwash plain in the middle valley. Sea level was 500 feet higher than it is today, submerging today’s barrier falls and allowing Dolly Varden to colonize. The gently rolling bench surrounding most of Douglas Island is blanketed by fine, poorly drained marine sediments, explaining the prevalence of bogs and scrub forest.

Flood-plain channels are best for spawning and rearing fish, but on Fish Creek, steep rapids form a barrier only 2.3 miles from the beach. Above, only small, resident Dolly Varden live. These probably have a mixed ancestry: some arrived on their own more than 10,000 years ago when sea level was higher (map, lower left); others were planted by people; and still more were likely dropped accidentally by dippers or kingfishers carrying prey to their nestlings.

Uplifted estuary

Based on Miller (1975).

Downstream (NW) of the highway, Fish Creek sediments spread out to form an alluvial fan. These coarse, sorted gravels were dredged, as shown in the right-panel photo series.

During the recent Little Ice Age, land was depressed 5 to 10 feet, and is now rising at about half an inch per year. Formerly tidal areas south of West Pond are rising above extreme high water, but are too poorly drained to support forest. In 1972, this area was blocked off from tidal access by a dike (grey on map) connecting to the gently curving, marsh-enclosing spit (yellow).

Ecologists Mary Willson and Aaron Baldwin sampling for invertebrates just outside Entrance Point. Here, Fish Creek deposits mud, gravel–and most important–small rocks permitting attachment by mussels, barnacles and rockweed (Fucus). These in turn host a rich community of crustaceans, worms and snails. At low tide, these flats often swarm with hungry shorebirds, dabbling ducks, gulls and crows. At high tide, diving ducks like scoters and goldeneyes target the same banquet of estuarine organisms. The flats north of Hut Point have 23 acres of this rock-dependent community–a quarter of its coverage on the entire Mendenhall Refuge. (Robert Armstrong photo)

The spit was built by storm waves fairly recently. We know it didn’t always protect the estuary, because there are uplifted wave-cut faces just inside the forest fringe, created many centuries ago when tides reached higher and the estuary was more exposed.

Uplift succession

Fish Creek Vegitation Chart

The air photos above show response to natural and human disturbance.Acreage of extremely valuable tidal communities–bare mudflat and sedge-dominated low marsh–have declined precipitously. That’s bad news for sedge-grazing geese and the many fish species that rear in the lower tide flats. On the other hand, uplift meadow and young alder-willow-spruce stands have increased–good news for most mammals and songbirds.

Birding diversity

Almost every bird species recorded on the greater Mendenhall Wetlands has been seen here at tiny Fish Creek Park–a reflection of the fine-scale mosaic of many different habitats in the inner estuary and flats outside.

Stories in sand and snow

Since 1988, thousands of 3rd-to-5th-graders have learned tracking here on Discovery Southeast field trips. We try to time these visits to periods of good snow cover, but traces of mammal passage can be seen year-round on sand and mudflats. Scats and feeding sign give further clues. For young naturalists, learning track ID is like basic spelling; from there we proceed to “literature:” why are these hare tracks concentrated in the willow patches? What’s the safest route into the park for a small black bear hoping to catch a pink salmon? When was the last time long-tailed voles reached peak numbers, girdling shrubs and tree saplings?

Aangooxa Yé

Animal's and thier tracks

“Hut Point” was so-named in 1880 for the presence of an Auk Kwáan village and nearby fort. It was known to the L’eeneidí clan as Aangooxa Yé (Goldschmidt & Hass, 1998). Before gold discoveries diverted settlement to Juneau and Treadwell, estuaries at Fish Creek and Outer Point hosted the principle village sites on Douglas Island. Not only were they rich in resources; bluffs near both creek mouths afforded good views and defense in times of war.

Air photo series

Fish Creek Air photo series

1948 Tide reached 3 feet higher than today. North Douglas Highway would not cross Fish Creek until 1957. Members of Auk Kwáan still had smoke houses at Hut Point–Aangooxa Yé–but they were joined increasingly by white homesteaders. There was even a school, serving about a dozen students through the 1930s and 40s. Salt-tolerant sedges (Carex lyngbyei) grew almost to the head of the estuary, and bare mudflat extended much higher than today. A few spruce saplings had begun to colonize the wave-built spit. On the bedrock knob at Entrance Point, ancient hemlocks indicate that tide never covered this site during the Little Ice Age.

1962 Tides reached 28 inches higher than today. East Pond was dredged to a depth of 50 feet. The 1960s were a time of rapid development throughout Juneau, with few regulations protecting streams and coastal habitats. The Fish Creek salt marsh was buried in new sediment washed down from dredging activities. Ten years after this photo, West Pond (south of the creek) was dredged to 28 feet.

1984 Tides reached 15 inches higher than today. In addition to the dikes containing West Pond, a connector dike reached west to the wave-built spit, isolating the southern wetlands from tidal influence. Alders (Alnus crispa) and willows (Salix spp) rapidly colonized older dikes and other raw surfaces exposed by construction activities. On Thanksgiving Day, 1984, 3 months after this photo, a severe storm combined with extreme high tides breached the West Pond dike. It was never repaired. Today, this pond hosts a terminal king fishery. New homes were appearing both north and south of the estuary. Compare this 1984 shot to the central panel for a 2006 view.

Sources: Goldschmidt, W. & T. Haas. 1998. Haa Aaní. Our Land: Tlingit and Haida land rights and use. U Wash Press. • Haeussler, P. 1992. Structural evolution of an arc-basin: the Gravina belt in central SE Alaska. Tectonics, 11(6), 1245–1265. • Miller, R. 1975. Surficial geology map of the Juneau urban area and vicinity, Alaska. Misc. Inv. Series I-885.

Fish Creek Area Map

Trail Access

Distance: Fish Creek bridge to Entrance Pt, 0.7 miles.
Park acreage: 150 acres, CBJ and State combined.
Elevational relief: 40 ft, road to creek bed.
Difficulty: easy, but no ADA trails.
Ownership: CBJ, State of Alaska.
Notes: The 2.5-mile Upper Fish Creek Trail begins north of the bridge and ends at 2.3 mile, Eaglecrest Road.

Tread Lightly!
• Please do not pick or dig
up wild flowers.
• Do not feed wildlife.
Pack it out
• Carry out all trash.