|This paper was written as part of the 1999 Alaska Ocean Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.|
in part by each of the following:
White Mountain High School
AbstractSteller sea lion(SSL) populations have declined sharply in recent years. Some researches claim population drop is as great as eighty-five percent. Present rates of decline indicate possible extinction of at least the western stock within the first century of the new millennium. Many factors are blamed by various groups, and available data are not sufficient to make absolute determinations. Since several factors are placing stress on the SSL, a reasonable assumption was made that more than one force is at work harming this marine mammal. Such factors as: overfishing, predation, warming of ocean currents, pesticides, or even over abundance of non-traditional, low in food value species such as pollock. Attention was also given to the effects of substantially reduced SSL populations on the environment and on Alaskan Natives. Solutions offered tended to mitigate the above listed factors while minimizing negative impact on human enterprises such as agriculture and fishing.
There has been a considerable amount of decline in the Steller sea lion, Eumetopias jubatus (Pinnipedia: Otariidae), population in the past 35 years. Two populations of Steller sea lions exist. They are the western stock and the eastern stock. Many people, particularly those who derive their livelihood competing with the Steller sea lion for fish, believe either the decline is not serious or that their fishing activities is not a factor; therefore, I believe that the population decline is, indeed, related to overfishing and many other factors. Such factors include the natural rise and fall of the population, disease, over hunting, El Nino, and pollution.
The western population of Steller sea lionswas recently put on the "endangered" species list by the National Marine Fisheries Service in 1997. Population in this stock has clearly been declining. According to P.S. Hill, D. P. DeMaster, and R. J. Small, the population has dropped from approximately 225,000 animals in 1965 to about 45,000 in 1994, which is a drop of 80% in 29 years. On the other hand, George Owletuck proclaims that the populations have declined 82.5% in just ten years from around 200,000 to 35,000 between the years of 1988 and 1998. Another source conveys that the population has dropped 81% in the past 30 years(I. L. Boyd, 1995). Subsequently, Loughlin et al. (1992) claim that the population was 227,600 in the 1960's and has dropped to 43,200 in 1994. This is about a 81% decline in 29 years.
Unlike the western stock, the eastern stock of Steller sea lions are classified as "threatened." Populations of this stock have remained stable and even have been increasing. In the 1960's, the population of the eastern stock was about 19,300(Small et. al, 1995). By the 1970's, the population had dropped to 16,700 animals(Small et. al, 1995). Since then the populations have gradually been climbing. According to R.J. Small and D.P. DeMaster, the population for the eastern stock in 1994 was close to 23,900 animals.
There are many different theories as to why the population of the Steller sea lion has been declining. The leading hypothesis is that the prey of the sea lions has either decreased or changed (Marine Mammal Commission, 1997). Meaning that there is less food, or that the food is like twinkies and doesn't contain enough nutrients or fat (Blackburn, 1999). Take pollock fisheries for example. They take a whole lot of pollock in, and that is food that sea lions and other animals can use. On the other hand, the pollock might not be nutritious and so the fishermen might actually be helping by making them less available.
Another theory, that is actually just an extension of the first one, is that juveniles don't get enough food (http://www.wri.com/discovery/probes.html). El Nino and other warm water phenomena have forced some fish to swim deeper. Since a young sea lion can only dive one fourth as deep as an adult, it is much harder for young ones to get food. Without food, the sea lions cannot grow or prosper (Anonymous, 1994).
Pollution can affect the sea lions in a number of ways, such as birth defects and growth. An example of one of the pollutants is a chemical called DDT. It is mostly used in China, and it can be carried over by the wind. There isn't much evidence to prove that pollution is major factor. Parasites and diseases may also be causing death among the sea lions (http:www.vancouver-aquarium.org/conserv/Stellers/problems.htm). But they are not thought to be a major factor in the population change (NMFS, 1992) because they have always existed, and haven't increased.
Increased predation is unlikely to be the cause of the widespread declines in Steller sea lions (NMFS, 1992). Killer whales and sharks are probably the only significant predators they have besides humans (The Bering Sea Ecosystem, 1996), and they aren't doing much damage. However, it could have some effect on the recovery of the population.
Other people believe that there is nothing we can do to help the sea lions. These people believe that the population change is just a natural occurrence. It wasn't caused by anything. Things just change by themselves, and this time it was something that had some effects on the Steller sea lion.
The Steller Sea Lion Research done by I.L.Boyd (1995), suggests that no single factor has been responsible for the decline in the population of Steller sea lions. The factors that started the decline may not be the same as the ones that are sustaining the low population.
No matter what theory or theories you choose to believe, the problem is still the same. The Steller sea lion's population is declining. Things need to be done to stop this, or there will be some major effects.
Outline on EffectsTitle: Bad Things caused by extinction of Steller sea lions
I. Effects on Natives
II. Effects on Environment
A. Population control of pollockAs time goes by, the Steller sea lion death count is getting higher. In the last 30 years, their population has declined by 85 percent. (http://www.yoto.com/daily news/Steller.asp) If this rate of decline were to continue, we might say that the Steller sea lion will be extinct in about 100 years(Stinson,1999). And if extinction should occur many people, including the natives, will be negatively effected.
Natives will start to lose a lot of their culture, if the Steller sea lion goes extinct. They will lose some of their food supply, and have to use their own money to buy store bought foods. Many will also feel that their nutrition will decrease. They might think that they can't get the nutrients they get out of the Steller sea lion anywhere else. Many natives use the furs and other portions of the Steller sea lion to make stuff that they can sell. So if the Steller sea lion goes extinct, many will start lose some of their money. Not only that, people would most like starve. Most natives would prefer to eating what they have been eating their whole life. That includes the Steller sea lion. They wouldn't want to change that. They want to eat native foods and not store bought cardboard.
If people were to limit the amount of hunting on the Steller sea lion, again natives would lose some of their culture. The stuff they get out of killing the Steller sea lion would decrease. They will lose money, tradition, and ways of living. Limiting hunting is not such a good idea. There might be some positive out of it and lots of negative. Either way hardly anything is solved.
Many cultures would like to see there little boy catch a Steller sea lion. By catching a Steller sea lion, it indicates that the boy might be a man after he hunts down his first Steller sea lion. If they go extinct, many little boys have to shoot something less worth catching. A lot of thier pride will be taken away from them.
Many environmental problems will occur if extinction happens. If extinction does happen, the number of pollock will start to increase. More will inhabit the oceans and start to munch away on what they eat. They will eat so much that one day thier food will get exhausted. The pollock's food source will almost be gone and their population will crash because of starvation. Diseased and small pollock will started to increase in number if extinction occur. If the Steller sea lion isn't around to eat the easiest catches in the ocean, diseases will be past down genetically. More lame ones will be born and fisheries will be catching lame fish.
Extinction might cause damage to the sea and sea life. Lets say that Steller sea lions might keep the number of some organism under control. If there were no more Steller sea lions this organism might have a poplulation explotion and damage the ecosystem. This happened when the California sea lion population was greatly reduced allowing sea urchin poplulations to explode and subsequently negatively impact the kelp beds. Anytime you remove a major predator there is a danger of prey species rapidly increasing in number and harming the environment.
Causes of SSL Decline & SolutionsI. Cause: Overfishing of Pollock
Solution 1: Limiting Pollock FishingII. Cause: Too much Pollock
Solution: Fishing Extra PollockIII. Cause: DDT and Insecticides
Solution 1: Using Environment Friendly InsecticidesIV. Cause: Natural Cycle
So what can be done? With so many different possibilities for the cause of the decline, how can we figure out the proper solution. Since the exact cause is unknown, I think the best solution would be to experiment different solutions or combination of solutions. I will explain what I mean in the following paragraphs.
The most agreed on reason for decline seems to be overfishing of pollock. Population of the Steller sea lion has gone down by eight-five percent during the same time pollock fishing doubled. (1998 http://www.enn.com/news/ennstories/1998/04/0421/Steller.asp) It would probably be most reasonable to test the overfishing theory out first. The first thing that probably comes to mind is limiting the amount of pollock fishermen catch. By the way, the fishermen claim that we would be wasting time and money by carrying out this plan because they argue "their harvests target adult pollock, not the juveniles eaten by sea lions". (Rosen http://members.aol.com/cmwwrc/marmamnews/97050101.html) Also, some scientists say the fisheries are not overfished and that only eighteen percent of the pollock is harvested each year. (Weaver 1998) Do sea lions really target only the young fish, and ignore the adult fish? Still, we must keep the fishermen's opinions in mind. So maybe it's possible to have pollock nurseries. There are already salmon fisheries so I think this could work. If this doesn't seem to be working maybe it's because there are too many fish.
Let us go back to the "Pollock Overwhelmed the Ecosystem" theory and the "Pollock is Like Twinkies" theory. (Blackburn, Chris 1999) The only way to know if an overabundance of these fish is the problem, is to get rid of the extra fish. This would certainly make the pollock fishermen happy. Also, we all know twinkies aren't very good for you and so, if there were only enough pollock for a treat every now and then and not for a full meal, then maybe the sea lions would be forced to stop eating only sweets. If that sounded a little confusing try to see it like this: If you drink a can of pop and eat a bag of chips before dinner, what is the probability of you finishing your food? Not likely. Most of it would end up Thursday leftovers. What if the store was closed and you couldn't get a can of pop or chips. You wouldn't be able to snack and would be more likely to eat your dinner. The same principle would apply to the Steller sea lions. If they weren't able to eat too many nonnutritious foods, such as the pollock, they would be forced to return to their previous and more healthful diet. In other words, they would go back to hunting what they're supposed to and get nice, fat, and healthy.
Increasing levels of DDT and related insecticides are showing up in sea birds, sea mammals, and other tertiary consumers. It is suspected and likely that these man-made toxins are interfering with the Steller sea lion's ability to reproduce and shortening it's life span. We, in the US, have found ways in which harmful bugs can be killed by biodegradable bug sprays. These sprays kill the bad bugs and subsequently degrade into relatively benign substances. A team of US agricultural experts should be sent overseas to teach farmers how to use these insecticides. The Asian farmers should be willing to learn to use them because they are less harmful to their family and animals.
Another way of killing harmful bugs is by using other bugs. Take ladybugs for example. They love to eat aphids. If you take an area full of aphids and introduce ladybugs there, guess what will happen to the aphids. They're history. So, if we could put bugs, such as dragonflies and certain types of wasps, into the relevant agriculture environment, perhaps this would exterminate the bad bugs.
There's always the possibility that the Steller sea lion decline is just a natural cycle. Still, it's better to be safe than sorry. So until the real reason is know, I think we should keep on experimenting and hope that the decline of the Steller sea lion will be over soon.
Works CitedAnonymous. 1994. Is it Food? Addressing Marine Mammal and Sea bird Declines: Workshop Summary. Fairbanks, AK
Blackburn, Chris. 1999. CBLACKBURN/0007353974@MCIMAIL.COM
Boyd, I.L. 1995. Steller sea lion research. Cambridge, UK. British Antarctic Survey Natural Environment Research Council. 90 pages
Hill, P.S., D.P. DeMaster, and R.J. Small. 1996. Alaska marine mammal stock assessments 1996. U.S. Dep. Commer., NOAA Teck. Memo. NMFS-AFSC-78, 2pp.
Loughlin, T.R., Perlov, A.S., and V.A. Vladmirov. 1992. Range-wide survey and estimation of total number of Steller sea lions in 1989. Marine Mammal Sci. 8:220-239.
Marine Mammal Commission. 1997. Annual Report to Congress.
National Research Council. 1996. The Bering Sea Ecosystem. Washington D.C. National Academy Press. 303 pages
NMFS. 1992. Our Living Oceans. Report on the Status of U.S. Living Resources.
Oweletuck, George. 1998. Tribes Defend Sea Lions from Trawlers. "http://www.arctic.net/~theblade/WEEK1.HTM"
Rosen, Yereth; Agency lists Steller sea lion as endangered. http://members.aol.com/cmwwrc/marmamnews/97050101.html. 1/26/1999.
Small, R.J. and D.P. DeMaster. 1995. Alaska marine mammal stock assessments 1995. U.S. Dep. Commer.., NOAA Tech. Memo. NMFS-AFSC-57,, 93pp.
Stinson, Jay; Changing Sea Lion Populations in the Gulf of Alaska; January 15, 1999
Weaver, Susan A.; Feds Use Several Council Initiatives to Better Protect Steller Sea Lions in Alaska's Pollock Fisheries. http://www2.nas.edu/prb/224e.html. 1/26/1999
"http://www.yoto.com/dailynews/stellar.asp" December 18, 1998