Noel et al.,2013 1

The Yukon River Estuary and Satellite Photography as a Tool for Population Studies in

the Yukon Estuary

Team Antarctic Bottom Water:

Sarah Noel*

Emily Eckroth

Danny Maisey

Courtland Parret

Heather Schoff

Coach: Chris Backstrum*

South Anchorage High School

13400 Elmore Road

Anchorage, Alaska 99504

backstrum_chris@asdk12.org

ak.noel.907@gmail.com

Noel et al.,2013 2

Abstract

Located in Western Alaska, the Yukon Estuary encompasses the borders of the lowland

area that comprises the Yukon Delta. The abundance of freshwater runoff transports nutrients

into the ecosystem, supporting a wide variety of plant and animal life.This important estuary is

home to tens of millions of seasonal breeding birds that take advantage of the biological energy,

safety, and available breeding grounds. Biologists use counting as a means of monitoring

population health and determining breeding pairs from year to year. Technology in the form of

satellites can be a useful tool toward the goal of measuring populations.

Noel et al.,2013 3

Introduction

The Yukon Delta National Wildlife Refuge, is 4,980 square miles. With origins in the Yukon

Territory of Canada, the Yukon river absorbs 43 individual tributaries (U.S. Geological Survey),

and is the primary watershed for about 330,000 square miles in both Alaska and Canada

(National Geographics). The Yukon watershed deposits 225,000 cubic feet of freshwater per

second into the estuary (Alaskan Nature).

The Yukon River Estuary is the primary spring breeding ground for about 2 million

waterfowl (U.S. FWS). The entirety of the worlds population of Canada Geese breed within ten

miles of the oceanic coastline in the Yukon National Wildlife Refuge (U.S. FWS). The Fraser

River Estuary in British Columbia Canada and reaching down to Washington is a winter habitat

for many of these birds. Migratory populations are fluid between summer and winter estuaries

on the western coasts of North America. This fluidity makes cooperative management and

counting of birds essential.

The ability to keep accurate counts of nesting and individual bird populations is

necessary to manage and follow population change. Satellite photography presents a logical,

and efficient method to capture large areas in real time. This methods allows for more accurate

surveillance of populations and interspecies relationships, as they fluctuate over time.

Noel et al.,2013 4

Discussion

regional overview

Estuaries are generally classified by geologic features and water circulation. An estuary is

defined as an area where fresh water mixes with saltwater to create an ideal environment for

organisms thriving in brackish environments. The four most general categories for classifying

an estuary are partially mixed, well mixed, salt wedge, and fjord (Estuarine Science).

A salt wedge estuary occurs when large amounts of water are discharged into a weak tide.

Based on the massive amounts of fresh water being discharged (225,000 cubic feet/second), we

have classified the Yukon Estuary as a salt wedge (Yukon River). Fresh water is the dominant

force in the estuary.

Located in Western Alaska, the Yukon Estuary encompasses the mouth of the Yukon

River. The Yukon River travels from Canada through Interior Alaska, finally braiding out and

emptying into the Bering Sea. The Yukon Estuary sits inside that braided area.

Image A

(NASA, Yukon Delta, 9-8-11)

Noel et al.,2013 5

The Yukon River Estuary is distinct from, but still a part of, both the Yukon-Kuskokwim

Delta and the Yukon-Kuskokwim National Wildlife Refuge. The estuary itself is approximately

4,980 square miles. Image A shows the width of the Yukon River Estuary, due to the branching

of the main channel. This calculation is based partly off of the highest tide in 2005, calculated

to be 2.3 feet (NOAA, 2005). The elevations of neighboring towns on the Yukon River were

factored in to distinguish the inland travel of tidal saltwater (USGS State of Alaska Map E).

Once the inland boundaries of the estuary had been established, the boundaries on the oceanic

side were figured in and the area calculated.

The Yukon River Estuary is fed by the Yukon Basin watershed. The Yukon’s watershed

spans the entire width of the state of Alaska, and stretches many kilometers into the Yukon

Territory of Canada, reaching a total of 3,185 kilometers in length (Yukon River). The total area

of the Yukon Basin watershed is roughly 840,000 square kilometers. This watershed is the 5th

largest in North America (Yukon Drainage Management Area). It collects and discharges about

195 cubic kilometers of water yearly (Yukon River).

Image B

Noel et al.,2013 6

(USGS, July 14, 2011)

Image B shows the area the Yukon River Basin encompasses. Due to warmer

temperatures, nearly 75% of the Yukon River’s discharge happens between May to September,

or a little less than half of the year (Transport of Water). All of the nutrients and sediment that

are carried to the estuary come directly from the Yukon River watershed. These nutrients and

sediments are critical to sustaining the bird population (Transport of Water). Of those nutrients

and sediments, 95% are brought to the estuary during the 5 month period between May and

September (Transport of Water).

The braided geography, and the rich abundance of nutrients delivered by the Yukon

River make it an ideal ecosystem. The delivery of these nutrients boost the photosynthetic

production of organic carbon. All organic carbon and nutrients in the Yukon are at their highest

levels during spring and at their lowest levels during the winter. This shows the main source of

nutrients come from snowmelt and the flushing of soils into the river (Robie Macdonald, et al.).

Noel et al.,2013 7

Organic matter that rivers deposit into the oceans are a significant percentage of the

global and oceanic carbon budgets. This input occurs primarily through estuaries. Approximately

250 million tons of dissolved organic carbon (DOC) is discharged from rivers annually (Bauer,

et al.). The organic carbon makes its way out into the estuary, and carried out into the ocean by

the river. The DOC is then available for organisms in the ecosystem.

DOC is readily available for the Yukon sedge. Through the process of photosynthesis,

DOC is incorporated into the food web, and the development of habitat for the goose population.

Yukon sedge or Carex bonanzensis is a long, coastal grass native to Northern Alaska

and Northern Canada (Tande et al. 2003). This particular plant is accustomed to living in both

wet and dry environments making it a perfect plant for the brackish environment of the Yukon

River Estuary (Tande et al. 2003). Yukon sedge (Carex bonanzensis) is a perennial plant,

growing back year after year, making it an excellent food supply for the resident bird species

in the Yukon estuarine system (Tande et al. 2003). This plant is vital to the sustainment of the

ecosystem and the support of food webs. The most important role of the Yukon sedge is the

ability to recycle nutrients and the use of energy for photosynthetic processes (Sedges). This

ability allows the plant to increase biomass and create a vital food source for grazing organisms,

such as geese. Nearly the entire population of Cackling Canada geese, Emperor Geese, and

almost half of the Black Brant population depend upon Yukon sedges for nesting habitat and

protection from predatory mammals.

The estuary is divided into many individual islands by the Yukon’s braided channels.

These isolated islands offer protection for nesting pairs from predators; predominantly foxes

(U.S.FWS). There are recorded instances where foxes find themselves stranded on islands

Noel et al.,2013 8

traveling across the frozen channels during the winter. Foxes prefer not to swim across the

Yukon after the ice disbands, and therefore reside on the islands they were stranded on. These

foxes thus stay and scavenge eggs and hunt the available bird life (Fondel; pers comm).

Geese are primarily ground breeders and use areas in the estuaries that are within a mile

of the coastal waters such as outer marsh zones and Yukon Sedge pond areas (Tande et al. 2003).

Canadian Cackling Geese keep sedges well trimmed which acts as a catalyst for the

continued expansion of suitable nesting habitat. (Doolittle pers. comm). This in essence makes

the habitat more suitable for other species of birds, especially Black Brants, by increasing the

available carrying capacity of the estuary(Doolittle pers. comm). A management plan that would

allow for an increase in the Canadian Cackling Geese populations should have a natural effect on

the increase in Black Brant Geese populations thus benefiting the ecosystem as a whole.

The current management of the estuary consists mainly of monitoring and recording

populations (U.S.FWS). This program results in a fairly stable and sustainable ecosystem.

Sport hunting annually has a nearly negligible effect on waterfowl populations for two

reasons. One, sport hunting regulations on the Yukon River Estuary area limit sport hunters to

fall hunting only and very small bag limits. Second, the inaccessibility of the estuary makes it

very hard for hunters without resources in the rural villages to access prime hunting grounds.

(Steinacher,2012)

Subsistence hunting of waterfowl in the Yukon National Wildlife Refuge (Yukon NWR)

has not affected the sustainable population of the Cackling Canada Goose, whose nesting

population is listed as 142,481 individuals (arlis).

Noel et al.,2013 9

The native populations have, for thousands years, relied significantly on subsistence

hunting of birds and in the future may have significant effects on bird populations. More than 40

Yup'ik villages rely on subsistence in the estuary, an equivalent of 25,000 people (Wentworth,

2007). A four year average calculates the take of subsistence hunting accounts for 41,008 birds

each year and 11,559 eggs each spring (Wentworth, 2007). Waterfowl comprise up to 6 percent

of the subsistence diet by weight per year. The arrival of migratory birds in the spring is often the

first source of fresh meat (Wentworth, 2007). The annual weight of all birds taken by subsistence

hunting in the estuary is about 315,000 pounds of edible meat (Wentworth, 2007). When this is

substituted for the cost of 4.00 dollars per pound, the annual native subsistence take is valued at

1.26 million dollars. Of this, geese make up 45% or 140,000 pounds of the overall subsistence

take (Wentworth, 2007).

Expanding native populations have created stresses, however. This has resulted in a

decline in the goose population through hunting. Because geese do not sextually mature three

years of age, the increased subsistence take has affected the aggregate population. Only one out

of every ten gosling survive the first year and even fewer survive to mature adulthood (Alaska’s

Emperor Goose, 2002).

Emperor geese populations that have traditionally been low due to the amount of time

required to reach sexual maturity and increased hunting pressure (Alaska’s Emperor Goose,

2002). Populations have increased and stayed within designated management parameters of

80,000 geese to allow minimal hunting from 2001 to 2010. (Pacific Flyway Council)

The estuary management in this instance has acted to inform the native hunters of the

emperors plight in order to spread awareness for the birds. Though the emperors are a major part

Noel et al.,2013 10

of the subsistence take for the yupik natives; efforts are being made to reduce stresses on the

geese.(Alaska’s Emperor Goose,2002)

Graph 1

Graph 1 (Alaska’s Emperor Goose,2002)

Graph 1 shows the birds have benefited from increased effort to reduce hunting stress.

(Alaska’s Emperor Goose,2002)

The ability for populations to stay at elevated levels will continue to hinge on the health

of the estuary. Careful consideration of development on the Yukon river including large scale

mining operations, and increases in hunting pressure represent the greatest threats to the estuary.

Noel et al.,2013 11

Graph 2

Graph 2 (Fishe, 2010)

Currently, the methods being used for monitoring populations of nesting geese are

collection by Fish and Wildlife workers, nest counting and aerial photography. These collection

tools involve many man hours, resources, and time to collect necessary data. Surveying an area

has a greater probability for human error. If the current management implemented an more

effective system of data collection, such as satellite imaging, the margin of error would decrease,

allowing for more accurate population estimates, leading to better management of the particular

resource.Nesting populations are easily counted on the ground by counting nesting sites. These

sites are currently censused by aerial photography at a height of 1400 ft (Bajak,1989).

The ability to maintain accurate year to year data on bird populations in the Yukon Delta

is best accomplished through satellite photography. Satellite images were first developed for war

Noel et al.,2013 12

in 1960. Due to the resolution of 5 feet by 5 feet, satellite imaging was not a very popular when

introduced, but as resolution increased so did their usability (Bauman, 2009). In 2009 Google

Earth released the announcement of two new satellites that can resolve objects as big as 41cm

across, which is smaller than an average adult goose (Worlds Highest, 2009). Google has the

technology to take even more detailed images, however government regulations does not allow

more detailed photographs (Worlds Highest, 2009).

The current technological advantages of satellite photography makes counting birds

through this medium not only more effective but also less time consuming and efficient than

ground surveys. In particular the GeoEye-1 satellite pulls images of higher resolution than

satellite images currently used by Google (Worlds Highest, 2009). The use of computer aided

procedures for counting waterfowl has greatly reduced time necessary for cataloging population

numbers shown in images C and D (North Coast Photos).

Images C

Image C (North Coast Photos)

Noel et al.,2013 13

Bird are recognized and differentiated by their contrast and shadows to the surrounding

ground or water as seen as image D (Bajak,1989). A computer program is used to mark the birds

with a contrasting colored dot (such as image C) that can be counted recognised and counted.

These techniques are already being applied to emperor penguins in the antarctic.

The penguin colony population estimates represent one of the first applications of

satellite imaging being used to census birdlife. In april of 2012 the British Antarctic survey

used high resolution imaging to count the emperor penguin population. The team utilized

international saddlelites and spent a year perfecting a technique called pan sharpening. This

technique is essentially taking many photos of one large photo (image D) and then using these

to differentiate the birds from the ground. The original estimate of adult penguins was 300,000

before this methods count. Using pan sharpening the researchers were able to amend that number

to 600,000 individual adults. Also of the original 37 colonies originally studied, 7 more unknown

colonies were discovered. All these assertions were confirmed by ground crews thus validating

the satellites survey ability (Hi-res Satellite Study Gives Birds-eye View of Penguin Population,

2012).

Noel et al.,2013 14

Image

Image D (North Coast Photos)

Use of high resolution satellite imaging in the in the Antarctic has asserted to be a

productive and efficient way to monitor bird populations when coupled with ground surveys.

This monitoring is vital to the health of an estuary as an upkeep of population numbers.

Monitoring of this kind could be transferred to the yukon estuary as a valid management plan for

maintaining species of concern at a healthy population. This would also allow for satellite

imaging of nesting sites. Allowing for monitoring of viable habitat in order to make sure that

there is adequate nesting areas to keep interspecies competition down.

Noel et al.,2013 15

This same use of satellite technology could be incorporated into the plan for measuring

the Fraser River Estuary bird populations.

The Fraser River is located in British Columbia, Canada and encompases an area that is

approximately 78,204 acres in size (image E).

Image E

The actual Fraser river estuary is located near the mouth of the Fraser River by the city of

Vancouver and borders the United states. It is a crucial stopover especially for long distance

migrants and wintering grounds for birds that migrate along the Pacific Flyway on their way to

Noel et al.,2013 16

the Yukon delta for nesting and brooding in the spring. The Frasers quality as an estuary greatly

exceeds the criteria set forth at the 1982 Ramsar International Wetlands Conference. It is

considered a wetland of International significance. (Fraser, 2012)

The Fraser River Estuary is considered a wintering estuary where geese gather on their

migration from Siberia, Alaska, and the Yukon. Satellite imaging would be exceptionally

useful in this situation as wintering birds congregate in flocks, making the cataloging process

much easier and the satellite censing more efficient and accurate. The current method of

population collection data is gathered in the Fraser River Estuary by a Christmas bird count

which consists of volunteers manually counting bird numbers once yearly for three weeks each

December. In addition to Christmas bird counts organizations such as Ducks Unlimited and the

Canadian Wildlife Service have commissioned aerial surveys every three years of duck and gull

populations on the Fraser River Delta. These methods of collecting population data are effective

and high definition satellite technology could help to confirm counts from the ground.

In conclusion the resource we have targeted are birds species in the Yukon Estuary.

We have laid out a specific plan of management that is beneficial to the proper collection of

population data in both the Yukon Estuary and the Fraser River Estuary. This plan will help to

manage the interspecies competition within the environment as well as better regulate the nesting

grounds of spring breeding species.

Noel et al.,2013 17

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