This paper was written as part of the 2006 Alaska Oceans Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.

Kenai Peninsula Ecosystem Management Plan for Pandalid Shrimp

Authors

Phelan Miller
Tyler Crista
Amy Collman
Luke Fry

Team Seward Shrimp Hawks

Seward High School
2001 Swetmann Dr.
PO Box 1049
Seward, Alaska 99664

Abstract

Populations of the pandalid shrimp in the mid-peninsula waters of southcentral Alaska have been declining for nearly 30 years. The decline has affected the multiple habitats throughout the Gulf of Alaska. This paper investigates the biology of the shrimp, the ecosystem surrounding them, and the possible reasons for a decline. We have made an ecosystem-based management plan based on the information we found. The shrimp influence populations of organisms by feeding on them, while at the same time feeding other species of animals. The reduction of shrimp populations affects the abundance of zooplankton communities they feed on. Reduced numbers of shrimp also affects the people living in the region. Some towns in the area, including Seward, depend on tourism to maintain economic stability. The decline in shrimp in the glacial fjords near Seward may have caused other larger animals to leave the area. Newly weaned harbor seals feed on shrimp when learning to effectively capture fish. Lack of shrimp may have affected harbor seal populations that also declined during that period. (Hoover-Miller 2005) The diversity of life in glacial areas creates visitor appeal. If one organism suffers, the entire ecosystem, including humans, suffer.

The cause of the shrimp decline has been speculated for years. One potential cause is the amount of trawling and harvesting done in earlier decades. Others include biological or chemical changes that affected the pandalid shrimp. The aspects of the decline we researched include overfishing, a major environmental regime shift, and predation. We have reviewed research findings from many research and management plans from other parts of the world with similar problems. Based on our research, we developed a unique and effective management plan to promote responsible harvest management of pandalid shrimp on the Kenai Peninsula with consideration of ecosystem change. This plan addresses problems of dealing with a vibrant but fragile ecosystem and takes appropriate steps to maintain a stable shrimp population in a dynamic environment. We have tried to make subtle changes that can improve the shrimp populations over time. These include changing fishing regulations and controlling predator populations.

Introduction

An ecosystem is defined as "an interdependent and dynamic system of living organisms with their physical and geographical environment". (Minister of Public Works and Government Services Canada 2003) Crustaceans, including small shrimp, in waters adjacent to glaciers are drawn to the surface by nutrients accumulated by upwelling and glacial sediment deposits. Nutrients may also be obtained in the fecal matter of other animals attracted to tidewater glacier environments. Surface-feeding crustaceans provide a nutrient-rich food source for fish marine mammals in the area. (Alaska Department of Fish and Game 2001) Such is the environment of the pandalid shrimp in the Kenai Fjords National Park. The shrimp control populations of the animals and plants they eat, and feed other species themselves. If this resource is not managed carefully (with consideration of other components of the ecosystem), overharvesting can have wide ranging environmental impacts.

Five species of pandalid shrimp are common to Alaskan waters. These include: pink shrimp, Pandalus borealis; humpback shrimp, Pandalus goniurus; coonstriped shrimp, Pandalus hypsinotus; spot shrimp or prawn, Pandalus platyceros; and sidestriped shrimp, Pandalopsis dispar. Pink shrimp is most common ranging from the Chukchi and Bering Seas to the Columbia River in Washington. They also are found to the east in Hokkaido, Japan. Pandalus borealis are also found in the Atlantic Ocean. These shrimp are generally found in silty or muddy areas including tidewater glaciers. The spot shrimp extends farther south to San Diego and is mostly found in rocky areas and the sidestriped shrimp is found only in the eastern Pacific. All other species are similar to the pink shrimp and are found in muddy areas. Figure 1 shows major harvest areas of multiple species of pandalid shrimp in southcentral Alaska.

Shrimp have been harvested commercially in the Aialik Bay area for over 50 years. (Cook and Norris 1998) The first commercial shrimp harvest in the Cook Inlet area took place in Kachemak Bay in 1939. Concurrently with, salmon, halibut, and herring fishery declines in the early 1960s, the shrimp industry boomed. Many towns on the Kenai Peninsula, including Seward, underwent a much-needed economic growth spurt due to commercial shrimping. Within the years of 1959-1963, three new canneries were built on the Kenai Peninsula for shrimp. After a short decline in the mid-1960s, the industry revived. Since the early 1980s the economic viability of commercial harvesting has diminished. Populations have decreased greatly. To sustain pandalid shrimp populations, responsible management is needed. In our research, we explored potential causes for the decline along the southern Kenai Peninsula and elsewhere in the Gulf of Alaska. Based on our research, we developed a plan to effectively manage shrimp populations and sustain the ecosystem of the area. (Alaska Department of Fish and Game 2001)

Shrimp

Shrimp have five pair of swimmerets to help propel through the water habitat and five pair of crawling legs to walk on the rocky and sandy environment where they live. Shrimp also have a fan like tail that helps them propel through their environment. Compound eyes and four very sensitive antennae help them navigate and find potential prey. As an egg the shrimp grows bacteria on self for protection from possible prey. After hatching the shrimp larva is free floating and it relies on the current to carry it. As young larvae shrimp are very tolerable of fresh water influxes.

When shrimp mature they grow in size and sink down to the bottom of their environment. Once on the bottom, their tolerance level for fresh water influx diminishes and influxes of fresh water increase their chance or mortality if they stay in the area of the fresh water influx. Shrimp prefer shallow water which is about 35-40 degrees Fahrenheit and love to hide in any nook or crannies they can find. Although more shrimp in Prince William Sound thrived until a regime shift in the late 70's that hurt their population. Shrimp also prefer areas with little fresh water influx because of their intolerance to the lesser salinity. This poses a problem for shrimp in Prince William Sound, because Seward has a huge amount of fresh water influx which potentially increases stress and mortality rate of the shrimp.

Pacific Cod live in the cold waters of Alaska and shellfish are a huge part of their diet which also includes mollusks, other fish and worms. Shrimp comprise a high percentage of the Pacific Cod's diet. Female cod may produce up to 2,500,000 eggs in a single season. These eggs are deposited at a lower depth but once fertilized they float to the surface where many of them are eaten. After a twelve day gestation the fish hatch. Cod are an important fish for the Alaskan commercial fisheries so if the Pandalid population drops, the cod that depend upon the Pandalids will need to find other food to survive.

Fresh water flows into Resurrection Bay in massive quantities. Water sources include rain snow melt and melting glacial ice. Exit Glacier is rapidly receding and by the glacial melt flowing into the river it raises and increases the amount of fresh water flow into the bay. Shrimp who are living around less saline areas exposed to more dehydration than those who are in more marine waters. Shrimp are very sensitive to their environment. If the water warms as studies show the shrimp must move deeper to cooler water, but as the shrimp go deeper there optimum habitat becomes scarcer.

Prior to the mid 1970's water temperatures in the Kenai Fjords were cold, the predator numbers were down and the amount of run off and fresh water influx was a lot lower. The early 1950's the Seward shrimp industry was looking up. At one point in time the shrimp was coming into Seward so heavily that Seward had to install four shrimp peeling machines. This made production of the shrimp a lot easier. The shrimp numbers were very high during this era. The massive numbers encouraged fisherman to over harvest them and the numbers started to fall. The shrimp were nearly gone, but they started to recover in the late 1960's. With a shift in the Pacific Decadal Oscillation in 1977 the shrimp population was pushed into a steady decline, the decline is graphed in figure 2.

Changes in the Ecosystem

One important factor affecting survival of Pandalid hatchlings is the timing of plankton blooms. If the plankton blooms late in the spring the Pandalids produce a higher population and have a better survival rate. If the bloom occurs early in spring or during mid season, the survival is still moderately high. If the number of shrimp is high then Pacific Cod and other predators have more food to eat and their numbers will increase. That may have helped start the crash of shrimp population was the combined effects of increased water temperatures, increased abundance of natural predations such as cool and over harvesting by fisheries.

An abrupt temperature change that occurred in the mid 1970's as the Pacific Decadal Oscillation shifted from cold mode to its warm mode. That shift was further enhanced by a strong El Nino event. These events initiated a series of long standing ecological change that has been described as a "regime shift." During this phase of the regime shift, from 1976 – 1998, numbers of shrimps on crabs and other crustacean diminished while numbers of cods and flatfish flourished. "Regime shifts are a change in the marine ecosystem occurring inter-decadally and globally. They are induced by what is referred to as climate forcing, or increases in global temperatures or global warming. (Wright 2003) "Regime shifts can occur, for example, when changes in ocean conditions, such as warming, affect plankton production, an event that easily propagates up the food chain. Changes in ocean conditions can also affect migration patterns, growth rates, and mortality of fish species." (Cugini 2004) In this case the warming of the air and ocean temperatures has cause melting glaciers, resulting in raised sea levels and a changed salinity due to an influx of fresh water run-off. "A dramatic 'regime shift' occurred in the late 1970s, producing a major increase in temperature and a reduction in seasonal ice cover." (Alexander 2000)

There are two different types of regime shifts, cold and warm. During a warm regime shift a type of plankton that supports a more surface level area of the water column, becomes the dominant plankton. Now in a cold water regime shift a type of plankton that promotes the sea bottom becomes dominant. Since the regime shift in the 1970's salmon numbers have been on the increase while herring, capelin, and Sea Lions were decreasing.

The warm waters associated with the change in the Pacific Decadal Oscillation caused numerous population problems, with many different species. "A climatic regime shift during the mid-1970s in the North Pacific resulted in decreased availability of lipid-rich fish to seabirds and was followed by a dramatic decline in number of kittiwakes breeding on the Pribilof Islands." (Bech 2005) The decline of the shrimp species in the Cook Inlet area has been studied for years. Most of the conclusions to the problem revolve around the existence of a regime shift. A regime shift is a very important part of our ecosystem.

Shellfish populations dropped in the 1970's, due to there inability to cope with the change in their environment (increased temperature). Diminished shrimp populations were further impacted by vulnerable to increased numbers of predators including cod and halibut. In 1998, the Pacific Decadal Oscillation has shifted to a colder phase. Although not as cold as in the 1960's and early 1970's, populations of shrimp are beginning to recover as stock grow commercial fisheries will grow. To minimize the likelihood of future occurrences we must learn from past harvesting mistakes and manage stocks from a multi-species ecosystem perspective.

Commercial and Recreational Shrimping History on the Kenai Peninsula

A summary of fishing activity by Cook and Norris (1998) outlined the history of shrimping and shrimp harvests on the Kenai Peninsula. In 1935 there was a small number of shrimp available in Resurrection Bay but they were not sufficient to support commercial industry. While commercial shrimp harvest had been under way elsewhere on the Kenai Peninsula since 1939, the Seward area did not begin commercial shrimp harvesting until the late1950s. In the early 1970s yields of shrimp were at a maximum. Large harvesting during this time likely contributed to the crash in numbers of shrimp observed. (Cook 1998) By 1980 there was another in tense fishing effort developed in responses to increased shrimp abundance by 1984 over half a million pounds of shrimp were caught. Since then there has been a steady decline typically with harvests of less than 25,000 pounds. (Table 1)

Shrimp Harvest Management

In order to reverse shrimp population declines in Kenai Peninsula waters, careful examination of other areas with similar problems must be made. Yakutat has experienced a problem with shrimp numbers similar to ours but a management plan for their area has already been established. Yakutat Area developed a shrimp management plan that supports a relatively small shrimp fishery that maximizes exvessel prices to the fisherman. This plan provides techniques for regulating numbers of shrimp harvested and for providing fishers with the maximum profits for their harvests while minimizing risks associated with overharvesting. The plan focuses on the harvest of spot shrimp, the most profitable species. The plan identifies a closed season each year to protect shrimp during the egg hatch period. The establishment of a maximum number of pots per participant helps limit harvests. Trawl fishing has been limited in productive areas that are used by pot fisherman to minimize conflicts between gear types and protect the shrimp. Harvests need to be monitored. The Yakutat plan relies on shrimp tickets to provide information on the pounds harvested. The addition of logbooks would be desirable to provide greater detail on harvest with respect to fishing effort. Because male shrimp change sexes as they mature, harvest techniques need to protect them and focus on harvesting the oldest mature females. The Alaska Board of Fisheries discourages the harvest of shrimp less than 2 years of age. The Yakutat Area Plan requires a stretch mesh size of 1.5 inches to minimize the retention of the smaller male, transitional, and female spot shrimp and other species. (Alaska Department of Fish and Game 2005b)

Our Proposed Mid Kenai Peninsula Ecosystem Management Plan for Pandalids

The Cook Inlet Shellfish Harvest Area needs to be divided into smaller sections including an area around Resurrection Bay and the fishing community of Seward. From the western edge of Northwestern Fjord to the eastern edge of Johnstone Bay could be known as the Mid Peninsula Regime Study Area (MPRSA). The area suggested is located in the region observed by Figure 1. Maintaining a small area like the one described will allow greater understanding and quicker feedback on how effectively the management plan works. (Alaska Department of Fish and Game 2005b)

In order to manage the shrimp populations located in the MPRSA, there needs to be an organization dedicated to monitoring, regulating, and enforcing the rules necessary to keep the shrimp an active part of our marine ecosystem. This would be one of the responsibilities of the Mid Peninsula Regime Ecosystem Board (MPREB). MPREB would not focus directly on the shrimp population but on the whole ecosystem. They will be dedicated to understanding the way the regime shift affects the environment and how fisheries can operate profitably without threatening ecosystem resources. MPREB would work in conjunction with the Alaska Department of Fish and Game to produce regulations that will sustain ecosystem management. A task of this organization will be focused on the regulation of crustaceans and ground fish that are so strongly affected by different phases of the PDO. Likewise the MPREB will work closely with National Marine Fisheries Service, Alaska SeaLife Center, University of Alaska Fairbanks, Institute of Marine Science, and other organizations with expertise on the local maintenance of an ecosystem to provide data and expertise needed by MPREB to make management decisions.

Stock assessment trawls are one way that the MPREB will observe changes in the ecosystem. Trawls will record the ratio of shrimp to Pacific cod and monitor shrimp stocks. Records on the sex, size, and species of the shrimp caught will be taken. The stock and densities will be contrasted to commercially harvested quantities in Prince William Sound, Yakutat, and Southeast Alaska. Any change in the collected trawl and temperature data might suggest a change in the environment's regime and will be considered when setting harvest levels such as what occurred in the mid 1970's and 1998.

During the warm regime phase it will be hard to responsibly manage a shrimp fishery and harvest levels must be very conservative. Because of low numbers of shrimp and high natural predation to shrimp ratios, additional human harvest could risk total removals of shrimp from shallow areas as was experienced during the warm period following 1977. Such a management strategy would not be suitable for this area. If the shrimp numbers increase, a small commercial fishery could be developed and used as a means to collect data in conjunction with commercial harvesters.

Because the PDO typically cycles every 15-20 years, increased shrimp stock would not be expected when the ground fish are flourishing. As the cold phase of the PDO develops, a return to high numbers of shrimp and lower groundfish numbers might be expected. Evidence suggests that a cold phase of the PDO supports an increased shrimp population and can bring sufficient numbers of shrimp to support a trawl fishery. Until stocks improve we need to avoid endangering the shrimp species by restricting harvesting to low levels. Cancellation of the trawl fishery might be a practical solution. A commercial pot fishery will give fishermen a chance to harvest shrimp in this area but it will avoid dramatic overharvests of shrimp species within large areas. A quota system for shrimp harvesting in the area will be a requirement for all participants. Careful records will be taken by Fish and Game and the areas fished will be recorded, too. If areas are being overfished a closure of some or all of the MPRSA will be necessary. The harvest season will be shorter than the previous seasons in the Cook Inlet area so the shrimp have increased opportunities to reproduce, and mesh restrictions will be enforced to target older, more profitable shrimp.

Because a quota system would be in place, commercial fishermen might avoid the fishery all together if they are unable to profit by it. Seward should promote the fishermen's ability to maximize the profitability of the harvests by helping them sell their catch directly to public, restaurants and markets rather than as frozen product to a cannery. One option is to give the fishermen a chance to make money off their catch by selling it themselves and not to a cannery. This will ensure fishermen receive good prices and will be more satisfied with a fishery than the current less regulated one that may be overharvesting available stocks.

Cod are a major predator of the shrimp, and a key species that can be regulated to benefit shrimp. A different management strategy for cod fishery that promotes harvests during warm PDO cycles could allow higher numbers of the shrimp stock to survive. Extending the cod fishery so the annual cod abundance is reduced could greatly diminish one of the predators to shrimp. If we promote harvests of cod during the warm phase of the PDO the risk of shrimp extinction might be greatly reduced. Increased cod harvest could reduce cod stocks for following year, providing shrimp a greater chance to survive. Nevertheless, cod are an important part of the ecosystem, and an important food resource for marine mammals. Poor management of cod resources can be potentially hazardous to the environment and other ecosystem components.

If we look at other areas that have experienced problems with shrimp and cod fisheries we can prepare for what might happen in the future. In the Vancouver area predation mortality by Pacific cod on pink shrimp declines in the mid 1980s and late 1990's due to depleted Pacific cod stocks. (Martell 2002) This evidence shows that a depleted cod stock might bring the shrimp population up.

The Scotian Shelf and Bay of Fundy region has experienced a problem concerning the cod in that region. Cooling waters suppressed the Atlantic cod appetites spurring a decline in which these species have not recovered from. A problem like this could be devastating to our cod fishery and our ecosystem. (MacKenzie 2002) The MPREB would need to be very aware of this potential problem when the PDO moves into a cold phase.

It is not surprising to find that there is a program that is focused on this problem already, but on a global scale. U.S. GLOBEC (Global Ocean Ecosystems Dynamics) has been researching ecosystem changes for years. One GLOBEC program focuses ecosystem research on the Northeast Pacific Ocean and is an excellent resource regarding ecosystem change in Alaska.

Funding

As with a lot of scientific research and management, funding will be needed to support an ecosystem approach to management. The creation of a research based organization requires a stable funding base, involving multiple management groups and a variety of stakeholders using resources on the Kenai Peninsula. Funds will be needed to support key MPREB personnel and to organize and host meetings with experts and stakeholders. Also, part of our solution includes conducting trawl samples to monitor the stock and condition of shrimp.

Grants will be sought to provide funding for the MPREB especially in the first few years. We will seek initial funding from the Alaska Sea Grant program. Our problem and solution fit directly into their funding criteria. Because they are focused on understanding Alaska, our project would be very worthwhile for them to invest money into. We also will seek funding and collaboration with the Alaska Department of Fish and Game and the National Marine Fisheries Service. Because the MPREB addresses issues throughout the ecosystem both agencies would be able to provide valuable resources. We will also request expertise from the University of Alaska, School of Fisheries and Ocean Sciences, and the Alaska SeaLife Center for our scientific panel. If we develop specific research needs, we may seek funding from scientific funding sources such as the North Pacific Research Board, Exxon Valdez Trustee Council, and National Science Foundation.

Conclusion

The regime shift of 1977 has shown us the effects of warm water on a temperature sensitive ecosystem. We believe our management plan will provide the ability to monitor and manage shrimp populations within a changing ecosystem. Because the regime shift can be challenging to anticipate, any solution must be flexible in order to adapt to the changing environment. We have researched what other groups of people have done to ensure a stable shrimp fishery in their area, and used that as a guide to form our own plan. It is difficult to change one aspect of an ecosystem without affecting another. When addressing causes of shrimp population declines, potential actions we must consider impacts upon sustaining shrimp populations as well as other components of the ecosystem ranging from cods through seals. PDO and associated ecosystem regimes are natural cycles, and any steps we may take to support the favorable ecosystem cannot ignore these processes.

Figures

Map of Northwestern Fjord to Johnstone Bay

Figure 1.This is a map of the west side of Northwestern Fjord to the east side of Johnstone Bay. (Alaska Department of Fish and Game 2005)


chart of pandalid shrimp versus fish and non-shrimp

Figure 2.


Year

Pounds

1970

2,365

1971

13,024

1972

79,506

1973

138,999

1974

265,286

1975

1,293

1976

595

1977

26,437

1978

10,154

1979

confidential

1980

confidential

1981

confidential

1982

confidential

1983

36,927*

1984

552,136

1985

confidential

1986

confidential

1987

7,292*

1988

confidential

1989

17,482*

1990

confidential

1991

confidential

1992

confidential

1993

confidential

1994

confidential

1995

n.d.

Table 1.Harvests of Shrimp along the Kenai Peninsula (Cook and Norris 1998)
General Shrimp (960) in Area 23
1970–1975—Gore Point east to Cape Fairfield
1976–1995—Point Adam to Cape Fairfield


References