¹Alaska Department of Fish and Game
Fisheries Rehabilitation, Enhancement and Development, and Sport Fish Divisions
3298 Douglas Street, Homer, Alaska 99603
²Alaska Department of Fish and Game
Fisheries Rehabilitation, Enhancement and Development Division
333 Raspberry Road, Anchorage, Alaska 99518-1599
ABSTRACT Supplemental production of hatchery-produced chinook (Oncorhynchus tshawytscha), coho (O. kisutch), and pink salmon (O. gorbuscha) offers additional opportunities for increasing numbers of anglers who utilize Kenai Peninsula fisheries. Although the Homer Spit was selected for release of smolts because of high accessibility to anglers, the site lacked an adequate freshwater imprinting source. Therefore, we assumed an artificial imprinting cue would be required to imprint salmon smolts and provide a homing stimulus for returning adults. The goal was to attract them to a general offshore area to minimize the potential for a congested fishery. Since 1984, nearly 1.5 million chinook salmon smolts have been imprinted and released into a small saltwater inlet near Homer, Alaska. Over 18,700 chinook salmon adults have returned since 1985, providing over 43,500 angler-days of effort in this roadside fishery. Returning adult chinook salmon homed back to the inlet where they were released, rather than to the imprinting station anchored offshore. Short-term saltwater rearing and release of later run chinook, pink, and coho salmon have also been conducted to extend sport fishing opportunities on the Homer Spit throughout the summer. The Alaska Department of Fish and Game, in cooperation with the City of Homer and South Peninsula Sportsmans Association, were co-recipients of the Sportfish Management Award of 1990. The award was presented by the American League of Anglers and Boaters for the best enhancement project in the Nation. These positive results demonstrate that biologists may have more options for creating new salmon fisheries in marine locations that lack freshwater for imprinting than previously believed.
INTRODUCTION Many of Alaskas sport fishing opportunities exist in remote locations that are accessible to few anglers, while readily accessible fisheries have become overcrowded. Angling opportunities can be created by developing new fish populations for existing access. Large numbers of anglers, comprising approximately 40% of the state total, are concentrated along the limited highway system on the Kenai Peninsula in Southcentral Alaska. In response to this large angling effort, the Alaska Department of Fish and Game (ADF&G), Division of Fisheries Rehabilitation, Enhancement and Development (FRED) Division, and the Sport Fish Division have attempted to create new fisheries for these anglers. The Homer Spit was selected for sport fisheries enhancement because it is highly accessible to the large numbers of residents and tourists who are already attracted to the area. Unfortunately, no adequate freshwater discharge for salmon imprinting is available on Homer Spit, so this project was originally designed to use the synthetic organic chemical, morpholine,¹ as an imprinting agent during the smolt stage and as a homing stimulus for returning adults. The original goal of this project was to subsequently use a morpholine "drip station" to create an adult chinook salmon return adjacent to Homer Spit, providing a shallow water troll fishery.
This imprinting technique has been used on salmonids in Lake Michigan (Cooper et al. 1976; Cooper and Scholz 1976; Scholz et al. 1975, 1978) and summarized by Hasler and Scholz (1983). Other experiments have been done with chinook and coho salmon in California (Hassler and Kucas 1982). These studies have demonstrated success in imprinting salmonids with morpholine in freshwater systems. To our knowledge, however, the Homer Spit experiment may be the first report of using this chemical as an artificial imprinting agent in saltwater for chinook salmon and the first to attempt to decoy returning fish to a more favorable marine sport harvest location. Subsequently, short-term saltwater rearing and release of hatchery-produced pink salmon fry and coho salmon smolts were also conducted without artificial imprinting to extend sport fishing opportunities throughout the summer.
STUDY AREA
The Homer Spit salmon enhancement site is located in the fishing and tourism community of Homer, on the southern tip of the Kenai Peninsula, in Southcentral Alaska (Fig. 1). The Homer Spit is a naturally occurring 7.2 km long gravel bar or "spit" that extends into Kachemak Bay in lower Cook Inlet. The project site is a small saltwater, intertidal inlet located approximately 5.8 km from the base of the Homer Spit (Fig. 1). This inlet is approximately 100 x 60 m in size, with a maximal depth of approximately 3 m at mean-low tide. There is no freshwater discharge into this inlet except limited surface runoff during rainfall.
METHODS AND MATERIALS
The chinook salmon spawning operation was conducted at the Crooked Creek Hatchery, and the eggs were transported to the Elmendorf Hatchery in Anchorage where heated water was available to accelerate development in order to produce smolts in less than a year. The smolts in one raceway were exposed to morpholine for 30-38 days each year from 1984 to 1988. Concentration in the raceways was adjusted to 5 x 10-5 mg/liter of morpholine following the calculation of Scholz et al. (1975).
After imprinting, smolts were transported by tanker truck to the Homer Spit and released into the small saltwater, intertidal inlet. Floating 3.7 x 3.7 x 3.7 m net pens have been anchored in the inlet to hold a portion of the smolts released in 1985 through 1992. The penned smolts are held for 5-7 days and fed 3.5-mm Oregon Moist Pellet¹ frozen fish food.
Coho salmon smolts are handled similarly to the chinook salmon smolts; however, it required an additional year to produce coho smolts at Elmendorf Hatchery. Coho salmon smolts were not imprinted with an artificial agent prior to release. Late run chinook salmon broodstock originated from the Kasilof River, which is also located approximately 96 km north of Homer. Spawning, incubation, and rearing to the smolt stage is conducted at the Crooked Creek Hatchery as a 2-year cycle. Late run chinook salmon also had not been imprinted with an artificial agent prior to release at the Homer Spit.
Pink salmon fry were also released at the Homer Spit site to diversify species return and timing. Fry were transported by skiff-mounted transport tanks from Tutka Lagoon Hatchery, which is located in Tutka Bay approximately 19 km southwest of the Homer Spit. These emergent fry were held for approximately 20-30 days in floating net pens and fed Alaska Dry Pellet¹ fish food by volunteers. The pink salmon fry were not artificially imprinted prior to release.
A floating morpholine "drip station" was anchored just offshore of the Spit (Fig. 1) to provide attractant for returning adult chinook salmon. The concentration of morpholine and the drip rate were gradually increased during the 1985-1988 adult returns. The decoy station was discontinued after 1988.
The number of fish returning to the inlet was estimated periodically by aerial surveys when water conditions allowed. On several occasions, an instantaneous population estimate was made by seining, marking, and recapturing fish in the inlet. The sport harvest was estimated by multiplying the number of anglers by the average catch per angler.
RESULTS
Juvenile ReleasesSince 1984, over 1,498,600 chinook salmon smolts have been imprinted and released (Table 1). The project began in 1984 with an initial release of 80,000 smolts and has expanded to a release of over 190,000-226,000 smolts in 1988-1992. In 1985, 1986, and 1987, approximately 50% of the smolts were held in net pens for 5-6 days prior to release, and in 1988 and 1989, over 80% of the smolts were held in pens before release (Table 1). Since then, between 80and 100% of the smolts have been held annually in pens (Table 1). The mortality rate of chinook salmon smolts during the short-term rearing period was less than 1% except in 1989, when the smolts had unusually high sodium-ion blood plasma levels prior to release. Mortality of the 1989 release was estimated to be 20%. The average sizes of the smolts ranged from 16.5 to 20.3 g except in 1986 and 1990 when they averaged 13.8 g and 14.8 g, respectively (Table 1).
Since 1988, over 539,930 coho salmon smolts have been released into the inlet on Homer Spit after a 5-7 day short-term rearing program (Table 2). Over 1,849,000 pink salmon fry were also released from the Homer Spit since 1987 (Table 3). In most years, fry nearly doubled their size, exceeding the 0.45 g size during the 20- to 30-day short-term rearing period.
Adult Returns
Over 18,700 adult chinook salmon have returned to the Homer Spit since 1985. These have provided more than 43,500 angler-days of effort (Table 4). An estimated 3,300 chinook salmon returned to the Homer Spit in 1988, the first year that all four age classes of chinook salmon returned since the initial release in 1984. The percent composition of the year classes of the 1988 return was 3% for age 0.1, 25% for age 0.2, 57% for age 0.3, and 15% for age 0.4. Similar results were observed through 1992. The highest return was 3,500 chinook in 1991. The mean smolt-to-adult ocean survival for 5 years data was 2.5%.
The chinook salmon returns have created a very popular sport fishery. Since 1988, sport fishermen have annually expended approximately 7,500 angler-days of effort to harvest an average of 3,000 chinook salmon, with an average catch rate of 0.40 fish per angler-day. Successful angling techniques included light to medium tackle with small artificial lures, flies, salmon egg clusters, herring, or shrimp. Current regulations by "emergency order" allow limited periodic snagging as a legal angling method after June 23. This provides an effective means of harvesting the remaining chinook, pink, and coho salmon when they quit biting during the last third of each species run.
Although the adult return station using morpholine drip was in position and operating during the 1986-1988 chinook salmon returns, there was no conclusive evidence that the chinook salmon were orienting to it. Only twice, during 1987 and 1988, were small schools of fish observed briefly down-current from the drip station. Therefore, the drip station was discontinued in 1989.
An estimated 18,600 adult coho salmon returned in August through September of 1989-1991 from over 339,330 smolts released in 1988-1990, yielding an average ocean survival rate of 5.3% (Table 2). The highest survival rate (8.1%) occurred in the 1991 return from the 1990 release of nearly 123,000 coho smolts (Table 2). This is encouraging data from the initial releases of the coho salmon smolts portion of the project. These smolts returned and homed to the small saltwater inlet where they previously had been reared and released, without exposure to morpholine imprinting.
Since 1988, over 17,600 adult pink salon have returned to the Homer Spit from releases of 1,849,000 fry. In 1988, over 4,500 adult pink salmon returned, yielding an ocean survival rate of 1.5% (Table 3). In 1989, the survival rate was over 3.3% with an estimated adult pink salmon return of 10,000 fish (Table 3). This was the highest return rate of pink salmon in the history of this project. Similar to most local area pink salmon stocks, recent returns to the Homer Spit have been low at 0.1 to 1.1% survival. The pink salmon adults also homed to the small saltwater inlet where they had been previously reared and released, without artificial imprinting.
DISCUSSION
The highly visible, roadside fishery created by this experimental salmon smolt and fry release program on the Homer Spit has generated intensive fishing effort, successful results, and very positive public response. To date, over 86,000 angler-days of effort have been expended in this road accessible fishery (Table 4). Local residents, as well as tourists from other parts of Alaska, other states, and many foreign countries, have participated in this fishery. The City of Homer, Homer Harbormaster Office, Port and Harbor Commission, South Peninsula Sportsmans Association, and Cook Inlet Seiners Association have been very cooperative and supportive of this project. Many local merchants have described a significant increase in seasonal business that is directly related to this and the other enhanced fisheries around Kachemak Bay. The sequential returns of chinook, pink, and coho salmon have provided angling opportunities throughout the entire sport fishing season (Table 5) in a location where only minimal angling opportunities previously existed.
The Homer Spit Sportfish Enhancement Project is funded by the Dingell-Johnson/Wallop-Breaux federal funding system and has received national recognition and an award from the American League of Anglers and Boaters. The Alaska Department of Fish and Game, the City of Homer, and the South Peninsula Sportsmans Association were co-recipients of the Sportfish Management Award for 1990 for the best fishery enhancement project in the Nation. As a result of national recognition and because of the economic benefits to the local community, the City of Homer expanded the small lagoon to provide for increased angling opportunities.
Although there is no freshwater available in the small inlet for imprinting, returning adult chinook, pink, and coho salmon homed to the small inlet where they were released, rather than to the morpholine drip station. Most of these fish are harvested either in the small inlet, the intertidal channel, or the adjacent shoreline during flooding tides. Unfortunately, relatively few chinook salmon are taken by trolling in spite of our attempt to imprint them to the drip station in an effort to spread the fishery over a larger area, rather than just to the confined area of the small inlet on the Homer Spit.
We are uncertain if the fish were adequately imprinted to morpholine as smolts. We believe, however, that the adults did not home to the morpholine drip station because the concentration rate was not high enough. The large tidal exchange (+6.6 to -1.5 m) probably dilutes and exports the morpholine so that it cannot be readily detected by the returning salmon. Also, it is likely that unique chemical characteristics associated with the intertidal inlet (e.g., organic matter, metal scraps on the bottom, chemical preservatives from wood in an ol barge and pilings, sand and gravel, etc.) impart a stronger influence on imprinting and homing than the exposure to morpholine.
It is most important, however, to note that chinook, coho, and pink salmon fisheries can be created by releasing the juvenile fish in highly saline waters without the influence of a freshwater imprinting source. Another aspect of the imprinting and homing mechanism that we have been particularly impressed with is the apparently brief imprinting period required. All of the chinook salmon smolts released in 1984, and more than half of those released in 1985-1987, were released directly into the inlet. Some were observed migrating out of the inlet within several hours. None of these treatment lots was marked, so there is no estimate of differential survival; however, at another project site, Halibut Cove Lagoon, where treatment lots were differentially marked, the survival of chinook salmon reared in pens for 14 days was approximately 30% greater than those released directly into a large lagoon with freshwater discharge (Dudiak et al. 1987). The increased survival advantage may result from better imprinting, better recovery from transport stress, or both.
Although the effectiveness of morpholine imprinting in saltwater appears to be low, the overall success of the Homer Spit Project is evident with the estimated mean survival rate of 2.5% for the chinook salmon smolts released from 1984 to 1988. This is comparable to the 2.4% average survival rate for chinook salmon smolts released and imprinted to freshwater at Halibut Cove Lagoon. As many as 5,000 adult chinook salmon are expected to return in 1993. Survival rates for pink and coho salmon have also been encouraging, and as many as 10,000 adult pink salmon and 10,000 adult coho salmon could also return in 1993.
These results demonstrate that management biologists may have many more options available to create new salmon fisheries in locations previously believed unacceptable because of the lack of freshwater for imprinting. If the chinook salmon had imprinted to morpholine as we had previously thought necessary, we may have been able to decoy them to another harvest location or alter their behavior pattern to create a new troll fishery in the vicinity of Homer Spit that would have been unique in this area. Nevertheless, a fishery that has yielded over 15,500 salmon in 1989 has been developed in a highly accessible location that extends from mid-May to October where none previously existed or was believed possible.
ACKNOWLEDGMENTS
This project was primarily supported by funding provided by the Dingell-Johnson/Wallop-Breaux Federal Aid in Sport Fish Restoration Program, Contract No. F-27-R, R-5. It was recognized by the American League of Anglers and Boaters as the foremost fisheries management project in the Nation in 1990.
The authors wish to thank Darrell Keifer and his staff at the Elmendorf Hatchery complex for producing and transporting the salmon smolts; Tutka Lagoon Hatchery staff for the pink salmon production for the area fisheries; and the Crooked Creek Hatchery staff, managed by Bob Och, who provided the chinook and the coho salmon eggs for the project. Mark Dickson, Fishery Technician III, played a major role in assisting all transports and pen rearing logistics. Dr. Allen Scholz, Eastern Washington University, provided technical comments about the use of morpholine as an imprinting agent. The City of Homer, Homr Harbormaster Office, and the Homer Port and Harbor Commission continue to be very cooperative and supportive of this project. The Cook Inlet Seiners Association has provided financial assistance, while the South Peninsula Sportsmans and Homer Charter Boat Associations provided volunteers to help feed and release the smolts.
LITERATURE CITED
Cooper, J. and A. Scholz, 1976. Homing of artificially imprinted steelhead (rainbow trout), Salmo gairdneri. J. Fish. Res. Board Can. 33: 826-829.
Cooper, J., A. Scholz, R. Horrall, A. Hasler, and D. Madison, 1976. Experimental confirmation of the olfactory hypothesis with homing, artificially imprinted coho salmon (Oncorhynchus kisutch). J. Fish. Res. Board Can. 33:703-710.
Dudiak, N., M. Dickson, and W. Hauser, 1987. Halibut Cove Lagoon Chinook Salmon Enhancement Project. 1973-1984. Alaska Department of Fish and Game. FRED Report Series No. 78.
Hasler, A. and A. Scholz, 1983. Olfactory Imprinting and Homing in Salmon. Springer-Verlag, Berlin. 134 pp.
Hassler, T. and S. Kucas, 1982. Artificial imprinting of salmon in an anadromous fish hatchery. Proc. of the 62nd Annual Conference of the Western Assoc. Fish and Wildlife Agencies, July 19-22, 1982, Las Vegas, NV, pp. 448-456. California Cooperative Fishery Research Unit, Humboldt State University, Arcata, CA 95521.
Scholz, A., C. Gosse, J. Cooper, R. Horrall, A. Hasler, R. Daly, and R. Poff, 1978. Homing of rainbow trout transplanted in Lake Michigan: A comparison of three procedures used for imprinting and stocking. Trans. Am. Fish. Soc. 107(3):439-443.
Scholz, A., R. Horrall, J. Cooper, A. Hasler, D. Madison, R. Poff, and R. Daly, 1975. Artificial imprinting of salmon and trout in Lake Michigan. Fish Manage. Rep. 80. Wisconsin Dep. Natur. Res. 45 pp.
¹Statement of brand names, model numbers, or sources of materials does not represent endorsement of the product by the Alaska Department of Fish and Game or NOAA.
