While the trash problem has existed since the fishing industry began using plastics in the 1950's, it is receiving new attention largely because of the cleanup effort, begun with a goal of stabilizing the monk seal population. The population has dwindled to about 1,300 or 1,400, about half the total in 1958. No one knows how many seals are lost to entanglements in floating trash. Since 1982, the fisheries service has documented 196, but many more animals are believed to have perished, their bodies caught below sea level and scavenged by sharks. While it is difficult to isolate what role entanglement plays in the overall decline of the species, said Jason Baker, the leader of the agency's seal population survey, it is one of the few factors that can be addressed.
Seals also suffer starvation, as do the fish on which they prey.
Another factor is male aggression, which occurs when the sex ratio of a given population shifts. In these populations, scientists have observed sexually aggressive behaviors in males resulting in the deaths of females and younger animals. That's the kind of situation that can really wipe a population out. In the second effort, in October 1999, workers on two ships supplied by the National Oceanic and Atmospheric Administration and the United States Coast Guard picked up 25 tons. So far, just 5 percent of the reefs have been surveyed.