Mini Research Paper on Sea Otters - Paper Example

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Boston College
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Sea otters are small marine mammal species, yet they have a huge impact on the kelp forest ecosystem where they reside as top predators. They form a group of voracious carnivores with the ability to eat almost 25 percent of their body weight in a single day for purposes of keeping up with their high metabolic demands. In Alaska, the population of sea otters has recently declined precipitously because of increased killer whale predation, thus causing sea urchins to increase and the kelp forest to decline (Estes, James, and Daniel 881). The sea otter decline was the most recent event in a sequential megafaunal collapse which includes northern fur seal, harbor seals, and Steller sea lions.

Even though still speculative, there is increasing evidence that shows post-World War II industrial whaling caused killer whales, believed by some to be the greatest whales' foremost natural predator, to have expanded their diet to include pinnipeds and sea otters, hence driving populations of these smaller and less abundant species downward (Lubchenco 319). The sea otter's coastal marine food web thus seems to be interconnected with events that act on large spatial and temporal scales. Many of a similar kind of processes which structure the sea otter-kelp forest system, even though challenging to understand or observe, may very well take place anywhere in nature.

Species interaction in an ecosystem involving a direct correlation, especially between sea otters and urchin populations when sea there is a decline in sea otter population, sea urchin population increases owing to a lack of predation. When this occurs, several abundant sea urchins have the ability to eliminate kelp populations from specific habitats virtually. The alternate states of this community, kelp, or urchin barrens, can be persistent for a long time as shown in the exploration of Aleut middens in Alaska. Since kelp is structure-forming species, they form habitat for several invertebrates and fishes; when kelps are lost, their associates are also lost.

The balance between sea otters or sea urchin demonstrated system changes spatially and temporarily. After protections taking place from overhunting, the population of sea otters that was recovering changed nearshore ecosystems by minimizing the abundance of urchins and promoting kelp forest expansion. In an orca-dominated system, sea otters are suppressed, urchins recover, and kelp forests decline. Populations which involve large pinnipeds such as Steller sea lions, northern fur seal, and harbor seals, further collapsed in the western Pacific.


A part of the food web in the Gulf of Alaska is depicted above to include some of the connections amongst species associated trophically to harbor seals. The figure illustrates some of the main species that pass energy to harbor seals, and their main predator such as killer whales. It is apparent that the potential for shifting dynamics in such complex web of trophic relationships of different populations wax and wane and the changes reverberate in related populations as a function of shifted predation patterns. Taking into proper consideration such dynamic of complex web and predicting the results in the change for instance which result from a fishery for herring, is among the most challenging aspects for both aquatic ecology and ecosystem-associated supervision of large oceanic systems.

An interesting hypothesis suggests that the decline of marine mammals, which include otters, may be consistent with increased mortality, probably from orcas, and not reduced food or any other bottom-up effects. Stewart et al. attributed the sequential decline in this population of animals to whaling in the ecosystem (645). Killer whales have a likely hood of consuming great whales, and when the great whales were suppressed as a result of hunting, killer whales expanded their diet to include harbor seals, fur seals, sea lions and eventually sea otters. Despite the fact that these animals spend all or most of their lives in shallow water close to shore, something much more is necessary to protect sea otters. Almost certainly the successful effort of conserving sea otters must also consider the open sea.

These observations suggest that large, apex carnivores figure prominently in maintaining biodiversity and that conservation and management strategies aimed at preserving these species and system should be planned on large spatial as well as temporal scales. The observations on sea otters and kelp forests, therefore offer general lessons for conservative biology and management of resources. The first is that the minimum viable concept of population is flawed deeply as a strategy for carnivore conservation.

Even though a minimum viable population can be enough to prevent the target species from being biologically extinct, it will often be insufficient to prevent ecological extinction. The other lesson is that a temporal and spatial scale of effective conservation needs to be large to the extent that it can include connections across ecosystems and to redress the course of recent history. Finally, the scientific uncertainties surrounding the understanding of these secretive species and processes like scale and complexity is an issue of concern. Therefore, conservative measures must proceed in the face of these uncertainties, in regards to the available weight of evidence.


Works Cited

Estes, James A., Alexander Burdin, and Daniel F. Doak. "Sea otters, kelp forests, and the extinction of Stellers sea cow." Proceedings of the National Academy of Sciences 113.4 (2016): 880-885.

Lubchenco, Jane. "Ecology: The sea-otter whisperer." Nature533.7603 (2016): 318-319.

Stewart, Nathan L., Brenda Konar, and M. Tim Tinker. "Testing the nutritional-limitation, predator-avoidance, and storm-avoidance hypotheses for restricted sea otter habitat use in the Aleutian Islands, Alaska." Oecologia 177.3 (2015): 645-655.


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