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.
Ecosystem Management of Pacific Halibut in Prince William Sound
Team Cordova Flatfish
This paper looks at Pacific halibut (Hippoglossus stenolepis) and explores the management practices for this species in the Gulf of Alaska, Prince William Sound, and Cordova. The Gulf of Alaska and Prince William Sound are diverse ecosystems with circulation systems driven mostly by freshwater and wind. Pacific halibut are the largest flatfish in the world. They are carnivorous and will eat any food available. In their juvenile stage they feed mostly on plankton, but as they grow bigger they will eat anything. Halibut are harvested commercially, for subsistence, and sport use. Many agencies play a role in the management of halibut. The International Pacific Halibut Commission (IPHC) is responsible for biological assessment and the National Marine Fisheries Service (NMFS) teams up with the North Pacific Fisheries Management Council (NPFMC) and uses the biological assessment to set halibut fishing regulations. Increases in productivity are good for halibut because it increases plankton abundance. Unfavorable water temperatures can cause stress on juvenile halibut and changes in ocean circulation as a result of climate change can push planktonic halibut into harsh living environments. Therefore, water temperature is important to track. Our recommendations for ecosystem management of Pacific halibut in Prince William Sound include new management of the sport halibut fishery, minimizing halibut bycatch in other fisheries and establishing a Local Area Management Plan.
Introduction to the Ecosystem
The Gulf of Alaska is a diverse ecosystem, defined by many different physical and biological features. The large scale ocean circulation is generally counterclockwise, driven by the low pressure systems that move in the Gulf. The high input from freshwater into the Gulf of Alaska from the Copper River and precipitation drive the westward flowing Alaska Coastal Current (ACC) (Figure 1).The ACC is ecologically important because it distributes nutrients along the coast. The weather in the Gulf of Alaska is dominated by extratropical cyclones, warm low pressure systems that result in high winds and precipitation (Mundy 2005). These storms move northwestward until the mountain ranges along the Gulf Coast stop their advance. These low pressure systems cause frequent rain and winds in the Gulf. The Gulf of Alaska encompasses the deep ocean floor of the Pacific and the continental shelf of Alaska and is home to many marine animals and seabirds.
Prince William Sound (PWS) is located off of the Gulf of Alaska, and is mainly an estuarine environment because of the large freshwater input from precipitation, rivers and glaciers. Part of PWS's circulation is driven by the ACC. There is also a counterclockwise circulation in PWS that is also driven by freshwater input. Both of these currents are strongest in the summer because of the runoff form melting glaciers. There is also wind driven circulation that is typically stronger in the winter when there is less glacial input and more winter storms with strong winds. PWS supports many different kinds of commercial and subsistence fisheries including one of Alaska's largest salmon runs and Pacific halibut.
Pacific halibut (Hippoglossus stenolepis) are the largest flatfish in the world. The average commercially caught halibut in 1995 was about 42 in long and 30 lb, but they can reach sizes up to eight feet long, and weigh up to 500 lb. Male halibut don't get as large as the females, most are within 10-80 lb, while any halibut over 100 lb is most likely a female (IPHC 2005). Halibut typically live to be 25 years old, but the oldest recorded age for both male and female halibut is 55 years. The Pacific halibut has a very flat body, and both of its eyes are located on the "colored" side, the side facing up. The colored side is brown, and the underside is a pale white color, so that it blends in to its environment (PICES 2004).
Halibut are carnivorous and eat anything they can get. Juvenile halibut eat small plankton, and between the ages of 1 and 3, halibut primarily eat small fish and other living things that aren't too big for them to consume. After that, they start to eat bigger organisms, such as cod, sablefish, pollock, rockfish, sculpins, turbot, other flatfish, octopus, crabs, clams, sand lance and herring. They often leave the bottom to search for other fish they can eat (Coughenower and Blood 1997).
In 1999, the exploitable biomass, or biomass available to fishing, of Pacific halibut was estimated to be about 258,000 t by the North Pacific Fishery Management Council (NPFMC). These halibut are found on the continental shelf of the North Pacific Ocean. They are distributed pretty widely, and can be found from California to the extreme north of Alaska; and from Russian to Japan (Figure 2). The most concentrated area of halibut, however, is located in the Gulf of Alaska, specifically the area around Kodiak Island (Mundy 2005).
Halibut generally live on the bottom and prefer cold temperatures ranging from 37° to 46°F. They occupy a wide range of depths in the summer, from as deep as 3,600 feet, to as shallow as 20 feet, however, most of the time they occupy depths from 90—900 feet so they can feed. In the winter, they are at depths from 600—1,500 feet for their breeding. Because of winter spawning and summer feeding, they migrate from the deep water on the edge of the continental shelf in the winter, to shallower areas in the summer where more of their food source can be found. Some of these migrations aren't long while some have reached 2,500 miles in length (Coughenower and Blood 1997).
The Pacific halibut's spawning season is from November to March. Males are able to reproduce after they reach about 8 years of age, while females take longer to mature and are able to reproduce at 12 years. Halibut are broadcast spawners, meaning fertilization occurs by random external contact. The eggs then hatch after a couple weeks, releasing the larvae. The larvae floats along the surface currents for 6—7 months, eventually settling to the bottom of shallower waters, and take on the halibut shape. After this, they begin to migrate with the older population of halibut, and in several years, begin to reproduce (PICES 2004).
Current Fishing and Management Practices
Pacific halibut are an important resource to Alaska and are harvested for commercial, sport and subsistence use, and provide income to those involved. Commercial halibut fishermen use a longline method and are called longliners. To fish this way a long line is laid along the sea bottom that has a series of leaders or gangions with baited hooks attached to them. The longline is anchored on both ends and lines run to the surface with buoys attached, so the longliner can leave and set several longlines. Longliners can lay miles in length of longline with thousands of baited hooks on it. It is common for several lines to be set for a 24 hour period (ADF&G 2005a).
There are many organizations that contribute to the management and regulation of Prince William Sound halibut populations. The International Pacific Halibut Commission (IPHC) is responsible for the biological resource assessment. Each year, they conduct a series of research cruises to determine groundfish and halibut abundance from Washington to the end of the Aleutians. They use a trawler or a long-liner to gather the selected species to collect data on the length, gender, maturity and visibility of hook marks on the catch (IPHC 2001).The results from this annual study are what determine the optimal sustainable yield, and from this the Total Allowable Catch is calculated. The optimal sustainable yield is the amount of halibut that can be taken in one year while leaving enough fish to sustain the population and fisheries. After estimates of sport/recreational catches, subsistence and bycatch are subtracted from the optimal sustainable yield, the remainder is the Total Allowable Catch for commercial fisherman, and this number is divided amongst all fishermen who own individual fishing quotas (Lindow pers. comm. 10-25-05).
National Marine Fishery Service (NMFS) is a federal organization that manages the commercial halibut fishery in the United States using the biological assessment information from the IPHC. The NPFMC with NMFS have the main responsibility for the groundfish and halibut management for the Gulf of Alaska (Witherell et al. 2000). Prince William Sound's system follows the national regulations without exceptions directed to the region (IPHC 2001).
Individual Fishing Quotas (IFQ) have been in Alaska since 1995 and are considered an innovative approach to managing commercial fisheries. Each fisherman is given their own quota or limit to meet each year taken as a percentage of the TAC after subsistence, sport, and bycatch estimates are subtracted from it. This means that there are no commercial "openings" like in salmon fisheries. Common management practice is to reduce harvest amount (TAC), when species abundance is low. When the abundance is high the TAC is raised. If the abundance gets too low then it would result in a fishery closure (Bechtol pers. comm. 10-27-05 ). In Alaska, specifically, it is required that the total weight of catch be recorded on the IFQ records (IPHC 2001).
Cordova is located on the Prince William Sound, and is part of area 3A of the IPHC regulatory areas. Area 3A is the largest in Alaska (Figure 3). In 2004, area 3A was allocated 25 million pounds of halibut for the commercial allowable catch. This was delivered to 19 Alaskan communities. Some major ports for halibut deliveries for area 3A include Homer with 24%, Seward with 24% and Kodiak with 17% (IPHC 2001). The commercial catch delivered to Cordova by 215 vessels was 1,492,924 lbs, or 6% of the total catch (NMFS), worth $4.4 million.
The total value of all commercial fisheries in Alaska was in 2004 was $1.2 billion (Figure 4) (ADF&G 2005a). For halibut, the 2004 season started February 29 and ended December 31. There was a total catch of 58,942,000 lb, generating an estimated $170 million (NMFS), or 14% of the total worth of all seafood from Alaska. Alaska salmon, in comparison made up $270 million or 22% of total catch.
Sport or recreational catches are monitored by a statewide survey that is then sent to both NPFMC and IPHC. Since sport or charter halibut are caught using a rod and pole, there are minimal regulations made because of the perceived low impact on the fishery (ADF&G 2005b). Instead of setting up a TAC, there is a bag limit of two halibut of any size per day and vessels are allowed to have four halibut on board total (Marston pers. comm. 12-12-05).
Longlines can also be used for subsistence harvest, with a maximum of 30 hooks set. Fishermen must obtain a subsistence halibut registration certificate (SHARC) to participate in the subsistence fishery. The daily limit for subsistence fishing is twenty halibut, except for areas 4C, 4D and 4E, which have no limit. In 2004, Cordova had 526 SHARC holders, an estimated 325 of them participated in the subsistence and sport fishery (Fall et al. 2004). Subsistence catch is also logged by a voluntary survey and they are not required to report weight or size only the amount caught. The boat is permitted to have more than 1 license holder on board, allowing for a larger amount of catch per boat.
Recruitment is the number of halibut being added to the population each year, and without a healthy recruitment the halibut populations will decline. Productivity is based on the recruitment of the stock which, with the halibut stock has varied throughout the century. The changes in the recruitment have shown a correlation to changes in the climate.
Scientists use what is called the Pacific Decadal Oscillation (PDO) index for measuring long term weather patterns. It is a long lived pattern resembling the El Niño pattern of climate change in the Pacific Ocean. The PDO has two different regimes which are referred to as positive and negative. These are determined by both biological and physical variables; including air/sea temperature, tree rings, and salmon catches. The positive regime includes a strong Aleutian Low, warm coastal currents, high productivity in the Gulf of Alaska, and low productivity around California (Clark and Hare 2002). The negative regimes are the opposite.
Scientists have found a correlation/relationship between these various climate patterns and halibut productivity. Positive regimes have led to an increase in productivity for halibut because of increases in the plankton population (Figure 5). Negative regimes can lead to unfavorable water temperatures causing stress on the juvenile halibut; changes in currents which would push larval halibut into harsh living environments which they cannot survive and will influence the plankton populations upon which larval halibut feed (Williams pers. comm. 12/14/05).
Since the 1960's bycatch has been one of the primary killers of halibut reaching a high of 80% of the total halibut catch in the mid 1980's. This can be accredited to the introduction of other fisheries such as pot crabbing and bottom trawling. In recent years bycatch has dropped down to 15% where it seems to have leveled off (Figure 6). Though bycatch made up a substantial percentage of the catch, it was not factored into the halibut season catch models until 1996. Reasons for this are many but, the most important factor is that information was incomplete and intermittent. Today bycatch data is tracked by NMFS which runs the Foreign and Domestic Observer programs. These programs require an observer to be on board the fishing vessel for 100% of its fishing season for vessels longer than 49 m, while observer coverage of smaller vessels is less restrictive (Witherell et al. 2000). The data that is returned from these observers is entered into the model to estimate halibut populations. When a bycatch limit is reached, which is predetermined based upon halibut populations, the affected fisheries are shutdown.
Proposed Ecosystem Management of Pacific halibut in Prince William Sound
Halibut are an important resource for Cordova as food and a source of income. Approaching halibut with ecosystem based management is critical to preserve the ecosystem that halibut rely on, managers need to be able to assess ecosystem health and monitor changes, so accurate predictions can be made for future management. We have brought forth several changes that could be made to the management of halibut. The changes address many different aspects of the halibut fishery.
Sport Fishing Management
Halibut charter fishing boats in Alaska is a growing industry, and sport fishing for halibut on charter boats has risen in popularity and the catches have increased. The charter fishing industry is also under much less management than the commercial fishery. Charter boat captains are given the option of filling out a survey were they can state their catch numbers. Since not all the boats participate in the survey, this data is not as accurate as possible. Currently the fishery is managed with Guideline Harvest Levels (GHL). The GHL is a limit set on how many halibut can be caught in an area. Currently there is no penalty for exceeding the GHL.
In 2004, the charter catch for area 2C was 1.8 million pounds, 22% over the GHL. For area 3A, the catch was 3.7 million pounds, 1% over the GHL. The charter catch for these areas combined was 13.6% of the commercial catch (Loy 2005). As the charter industry grows, stronger management practices must be put in place. The current management practice is becoming ineffective as the fishery grows.
Recently a proposal to put the charter industry under the IFQ program was submitted and considered by the North Pacific Fishery Management Council. The program would put charter boats under the same quota system as the commercial fishery. The proposal did not pass and left the charter industry with the current management.
Another alternative for management could be to put more restrictions on GHL's, such as penalties for exceeding the limit. We recommend using the same data that is used to set commercial fishery limits to set the GHL and adjust it as necessary with halibut abundance.
Because of the growing evidence of climate change/global warming, halibut also face a large threat from the climate's influence on their ecosystem. The recruitment of halibut depends a lot on the weather and climate that occurred in the year when they spawn. This larval stage is crucial to the survival, and because they are so vulnerable, even minor changes in the climate or weather, could harm thousands of halibut larvae. Since the larvae just float on the surface of the water, that leaves them very vulnerable to the possible negative climatic effects. These effects could range from undesirable temperature changes to surface current changes. The primary source of food for the young halibut is the zooplankton, which could also be negatively affected by climate change.
A good physical indicator of these ecosystem changes are water temperature and current changes. Also, if surface temperatures change in areas where the halibut larvae are known to be located, we could predict that they would be negatively influenced. Additionally, if the currents change in areas where halibut larvae or eggs are, they might be moved to a less desirable location than they previously were. If any of these three indicators (temperature fluctuations, change in current patterns, or decrease in zooplankton abundances) are observed, then a management plan should decrease allowable harvests.
Local Area Management Plan
In some Alaskan communities such as Sitka, they have set up Local Area Management Plans (LAMP). This is a specific guideline that applies only to that area so that the rules fit the surrounding ecosystem, and local economy. This would be a good management structure for the Prince William Sound area due to its ecological difference. PWS is an estuarine environment and is ecologically diverse. PWS is also very large, but good fishing spots are limited. If there were more guidelines for which kind of fishermen (commercial, sport, subsistence) could go in what zone, bycatch and overfishing could be prevented. This would require a meeting of community task forces to come up with a proposal to then pass through the fish and game advisory committee. From that point it would be passed on to NPFMC, Board of Fisheries, and eventually to the IPHC. The proposal would have a balanced approach to managing the whole range of different fisheries from sport/recreational and subsistence to commercial.
Scientists have experimented with different methods of trying to reduce the mortality of halibut recovered as bycatch in other fisheries. The first method was to sort the halibut on deck then put them into tanks on deck for further study before transferring the targeted species to the hold (IPHC 1993). In the second method, they put a screen over the hold before the entire catch was placed in the hold. This would filter out some of the larger halibut while letting the cod passed through. Later, they removed halibut that passed through the holes to categorize them by condition (excellent, poor, and dead). The first set of halibut being examined on deck was mostly in excellent condition with few dead or poor halibut. The second set of bycatch halibut collected in small tanks were difficult to maintain because bad weather would stress the halibut because of waves that formed in the rectangular tanks. The third set in the hold found mostly dead halibut and very few excellent condition halibut. After review of this experiment, it shows that halibut need to be sorted out as soon as possible to increase chance of survival. Extended periods of time in the fish hold and at the processor are shown to cause stress and an extreme increase in mortality. To increase survival, one primary step would be to increase sorting capacity during processing. If processors could reduce the time it takes to remove halibut from other fish, mortality would drop significantly. Educating fishermen on alternative methods of sorting onboard fishing vessels could also help reduce bycatch mortality.
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