The article claims that the main reason of declining sea otter population along the western coast in the U.S. should be environmental pollution rather than attacking by predators. More specifically, the writer discusses three possible explanation to rationalize the pollution hypothesis. The lecturer in the listening passage disagrees. She believes that those reasons the author cites are misleading and attacks each of the claims mentioned in the reading.
In the reading, the author begins by stating that there are several industrial chemical sources of pollution along the coast, and the water samples around the area was proved to be life-threatening to sea otters. The speaker, however, disagrees. She states that this argument cannot be true since there is no dead body of sea otter washed upon the shore. She goes on to say that the fact actually supports the predator hypothesis because the dead otters might be already eaten thus will not appear on the shore.
The author also claims that not only sea otters but other species of sea mammals such as sea lions and seals were in decline, and this fact suggests the pollutional damage is caused to all marine animal as a whole rather than solely sea otters. Again, the lecturer believes there are flaws in the writer's argument. The speaker holds instead that the declining populations of overall sea mammals regardless of species is due to the fact that whales have been hunted by human for a long period. She goes on to say that since the main predators of the ocean-- the orcas have no whale to prey on, they turn to hunt smaller marine animals such as sea lions and otters.
Another reason why the author feels that the uneven pattern of declining otter is that some experts suggested that ocean currents and other factors might cause the phenomenon. The professor in the lecture is doubtful that this is accurate. She holds that the location inhibited by otters have geographical traits such as to prevent big predators from entering. For instance, shallow and rocky locations will have a slower decline in comparison to locations that relatively accessible to orca.