Are Environmental Factors Causing the Decline in Returning Salmon?
By David Mondok
Academic Writing Social and Natural Sciences
After years of discussions about the decline in returning salmon, I have begun to contemplate about the reason for the decline in returning population of salmon. With all the research that has been done on the harvesting numbers and trending the decline of returning fish, we have seen poor numbers in the returns; even with the Emergency Closures on harvesting seasons. Being a fisherman, I have seen and experienced some of the environmental factors that may be impacting fisheries. How do these factors impact the fisheries? Although salmon harvests maybe contributing to the decline of returning numbers, environmental factors having a larger effect on the salmon fisheries, because with the increased human activity and the introduction of invasive species of predators the number of returning salmon continue to decline.
While there is no way to have exact numbers in the salmon populations, we can provide rough estimates of population numbers and annual averages allowing us to make informed decisions on the management of our natural resources. To narrow down this topic I am going to focus on three rivers across Alaska; Kenai River, Copper River, and Deshka River. These rivers receive steady pressure throughout Alaska’s salmon fishing season and also have commercial fleets that fish the ocean near the mouth of these rivers. They have also been monitored for several years with fish counters to provide biologist with relatively accurate information on the types of fish as well as the numbers.
All of the following salmon run calculations were gathered from the Alaska Fish and Games website.
On the Deshka River, fish biologists have been counting the returns of salmon to determine a 15 year average of 26,170 Chinook salmon and a 14 year average of 27,846 Coho salmon. Over the last 5 years the Chinook population has fluctuated from 18,800 in 2007 to 19,100 in 2011, but dipped as low as 7,550 in 2008. Chinook salmon’s life cycles usually run 4-5 years which likely means that the Chinook run in 2012 will have a very poor outlook. The Coho runs over the last 5 years have seen similar fluctuation from 10,600 in 2007 to 7,550 in 2011, but had a spike in 2009 at 27,400. Coho salmon’s life cycle usually span 3-4, so with the 5 year average being below 15,000 the Coho salmon has lost nearly 50 percent of its’ population in the last 10 years.
The Kenai River has been monitored very similar to the Deshka River, however due to receiving multiple runs of the same species the data is more difficult to keep concise, so I am going to convert the data into an overall sums of the species runs. The 23 year average of Kenai River Chinook salmon for the early and late run combined is 57,935. Between 2007 and 2010 the Chinook runs average was 37,950 but due to no longer having an early run count I cannot accurately provide an average for 2011, the late Chinook run count for 2011 was approximately 35,000 fish. The Sockeye salmon 21 year average is estimated to be 1,273,388. Over the last 5 years Sockeye salmon runs have been remaining fairly steady ranging from 1,230,000 in 2007 to 1,599,300 in 2011, with 2008’s run being the lowest at 917,200. The Kenai River also receives runs of Coho salmon but their numbers are not monitored as extensively as the Chinooks and Sockeyes.
The Sockeye run is the only run that is counted on the Copper River. The 11 year average for the Copper River Sockeye salmon run is 786,825. Over the last 5 years 3 of the runs have stayed fairly steady from 926,500 in 2007 to 914,300 in 2011, but in 2008 and 2009 the salmon numbers were poorly recorded to sonar counter operations. With the 3 of the last 5 years runs being over the 11 year average, it appears that the Copper River Sockeye population is doing well or is at least able to sustain steady numbers.
Out of the 3 different rivers across the Alaska and 3 species of salmon, it appears that the Deshka River Coho salmon have seen the most drastic decline in numbers. There may be several reasons for this ranging from harvesting to invasive species of fish in the water ways. Throughout Alaska salmon are harvested for personal and commercial use, both of which are regulated by Alaska Fish and Game by maintaining an open season, however of the 3 species of salmon on two of the species have set date for an open and a close of season and those species are Chinook and Sockeye salmon. Across most of the state it is legal to harvest Coho salmon during the entire year, leaving high harvest numbers by sports fisherman. Commercial fishing is regulated by the length of fishing season, hours during the day, and days of the week that salmon can be caught.
There are also factors other harvesting that may be causing the decline in salmon populations from human activities and predators. Humans have been utilizing the same streams and rivers that the salmon spawn in for rafting, boating, fishing, gold mining and even off-roading. These activities disturb the stream beds kicking up rocks, silt, and even salmon eggs, which are either covered by the dislodged debris or eaten by the native fish that live in the waterways all year long. If even one salmon redd is destroyed nearly a 1,000 eggs could be lost, lowering the returning population even more.
In the river salmon fry or smolt’s natural predators in most of Alaska have been trout, birds, and some mammals like river otters. In some areas of Alaska they face a new predator in the ecosystem and that is the Northern Pike, a very aggressive predatory fish that can consume over half a dozen smolts in one day. In areas where pike have started to show up salmon numbers have begun to decline, the Deshka River is one such area. Pike tend to prefer slower more vegetated waterways that also happen to be the habitat for the salmon fry. Pike have very few natural predators, the largest threat to pike are other larger pike. With pike consuming large numbers of smolt in the rivers it reduce the number of salmon that will face the open ocean and reach mature spawning age.
While it is an ever revolving cycle of life, the age old adage holds true “which came first the chicken or the egg”. As harvesting salmon target the mature spawning fish reduces the number of eggs that turn into smolt, the factors that reduce the number of smolt that make it to the ocean reduces the return of spawning fish. While it is important to have a healthy escapement of adult salmon, it may be even more important to reduce the disruption of the salmon redds were large numbers of eggs are vulnerable.
Over the last decade the amount of salmon that is harvest of the coast of Alaska has grown drastically. With the entire world looking to have a piece of this nutrient rich food the demand for salmon has increased. Commercial companies are not just harvesting salmon by the ton but by thousands of tons a year. By placing a limit on the amount of fish one company can harvest and have processed or shipped from Alaska the massive quantities of fish that are caught and sent around the world would be reduced. It may seem to be a selfish act, but these companies are taking away from the resources of Alaska and reducing the population of salmon across the board. In order to enforce this would cost Alaska millions of dollars in enforcement but would also create more jobs along the coast, bringing more stability to Alaska’s economy.
While reducing the number of salmon harvested may be important, the state would have to impose seasonal catch limits on salmon species similar to those that regulate Chinook salmon harvests. By putting a seasonal limit on sportsman harvest instead of just a daily limit, the state could regulate the number of salmon each individual harvests during the year. In subsistence areas of Alaska this would be difficult to implement without allowing for an additional supplement. The other factors that would arise from a seasonal limit is determining the number of fish that would be allowed by one individual to harvest and how to enforce the recording of the harvests, which would cost the state more money supporting wildlife enforcement.
The most important aspect of preserving any species is allowing for a large number of the population to breed. By placing restriction on the use of the waterways that are used by the salmon to build their redds, the species receives the greatest chance for their numbers to rebound. It will be difficult to get the approval of Alaskans in order to put restrictions on the waterways, but the easiest way to gain approval is by doing a trial phase on rivers across the state; were the activities that cause the most disruption to the river bed are restricted to certain parts of the river and times of the year. By running a trial phase of around 5 years on the selected river it would be possible to see how the restrictions have benefited the population of salmon in the area over 2 or possibly 3 life cycles of salmon.
The only ways to begin controlling the outbreak of northern pike in Alaska’s salmon streams is by offering a bounty on the fish or encourage kill-or-capture movement in those areas. By enlisting the help of the anglers in the state and offering an incentive, the state may be able to reduce the number of pike affecting the salmon population. With pikes aggressive nature, they are a very entertaining fish to seek because of their explosive power on top-water lures and their fighting strength. By drastically reducing the number of pike that live in the salmon streams, the prey on which they feed will begin to rebound. Unfortunately, the only way to completely remove pike from these waters would be to conduct a fish kill which would decimate ecosystem along the rivers and even in to the ocean, of course removing this as a viable option.
The regulations that we have in place to protect the salmon population have been enough to prevent a complete failure of the ecosystem but have not been as effect as they need to be. Through having harvest regulations for the entire state of Alaska and utilizing Emergency Orders to either close areas that salmon runs have been weak or encourage more harvesting in areas with high salmon returns, the state has been able to slow the downward spiral of one of its vital resources. However, I do not feel that it has been successful enough to sustain the population and the resource indefinitely. The Alaskan government needs to do more to ensure the survival of its greatest renewable resource.
The key may be the implementation of waterway restrictions of human activities and encouraging the killing and/or harvesting of pike. With restricting the activities that humans can do around salmon spawning streams comes few redds that will be disturbed and fewer eggs that may be compromised or consumed by the native fish. With pike being a species of fish that has been introduced in the most of the salmon streams that they are affecting, their removal only seems to be in the better interest of the salmon. By the changing human activities and trying to reduce the effects of human mistakes in the past we may give salmon a fighting chance.
Abrahams, M. V., & Healey, M. C. (1993, April). A Comparison of the Willingness of Four Species of Pacific Salmon to Risk Exposure to a Predator. Nordic Society Okios, 66(3), 439-446. Retrieved from http://www.jstor.org/stable/3544938
Alaska Salmon Project. 1 Oct. 2011. http://fish.washington.edu/research/alaska/index.html
Dalton, R. (2002). Pike pests ravage Alaska’s salmon. Nature, 418(6901), 907. Retrieved from http://www.ebscohost.com
Fore, L. S., Karr, J. R., & Wisseman, R. W. (1996, June). Assessing Invertebrate Responses to Human Activities: Evaluating Alternative Approaches. Journal of the North American Benthological Society, 15(2), 212-231. Retrieved from http://www.jstor.org/stable/1467949
Irvine, J. R., & Fukuwaka, M. (2011). Pacific salmon abundance trends and climate change. ICES Journal of Marine Science / Journal du Conseil, 68(6), 1122-1130. doi:10.1093/icesjms/fsq199
Kekäläinen, J. J., Niva, T. T., & Huuskonen, H. H. (2008). Pike predation on hatchery-reared Atlantic salmon smolts in a northern Baltic river. Ecology of Freshwater Fish, 17(1), 100-109. doi:10.1111/j.1600-0633.2007.00263.x
Lawson, P. W., Logerwell, E. A., Mantua, N. J., Francis, R. C., & Agostini, V. N. (2004). Environmental factors influencing freshwater survival and smolt production in Pacific Northwest coho salmon (Oncorhynchuskisutch). Canadian Journal of Fisheries & Aquatic Sciences, 61(3), 360-373. doi:10.1139/F04-003
Levasseur, M., Bergeron, N. E., Lapointe, M. F., & Bérubé, F. (2006). Effects of silt and very fine sand dynamics in Atlantic salmon (Salmo salar) redds on embryo hatching success. Canadian Journal of Fisheries & Aquatic Sciences, 63(7), 1450-1459. doi:10.1139/F06-050
Pacific Fishery Management Council (2008, February 4). Salmon Population Declines In California, West Coast. ScienceDaily. Retrieved from http://www.sciencedaily.com/releases/2008/01/080129210349.htm
Ward, D. M., Nislow, K. H., Folt, C. L., & Osenberg, C. (2008). Predators reverse the direction of density dependence for juvenile salmon mortality. Oecologia, 156(3), 515-522. doi:10.1007/s00442-008-1011-4
Willette, T., Cooney, R., Patrick, V., Mason, D., Thomas, G., & Scheel, D. (2001). Ecological processes influencing mortality of juvenile pink salmon (Oncorhynchus gorbuscha ) in Prince William Sound, Alaska. Fisheries Oceanography, 1014. Retrieved from http://www.ebscohost.com
(1992, March 20). SALMON IN DECLINE OFF WEST COAST. New York Times. p. 6. Retrieved from http://www.ebscohost.com
Filed under: Conservation, Fall 2011, Part 3 - 1st Rough Draft, Population, Sustainability, Wildlife | Leave a Comment »