There are about 11,000 Northern Fur Seals on San Miguel Island. The adult sea lions go to northern California and British Columbia after they breed, while the pups are left behind around the central coast. In one of the most physical demonstrations of El Nino, oceanic warming drove away much of their food supply: squid, anchovies, herring, and sardines. The pups are spending most of their energy in search of colder waters for their daily intake of 30 pounds of food.
Experts in marine biology are strictly observing and documenting the famine, not attempting to rescue the dying animals. They have been conducting studies on this island since the 1960s. Several rescue groups, such as Sea World located in San Diego, were ready to bring back the starving pups. However, the 1972 Marine Mammal Protection Act prohibits them from going to the remote island and disturbing their natural habitat. Experts would rather wait for the mammals to get washed up ashore than to separate a pup from its mother. The goal is to minimize human impacts.
Scientists are now trying to learn from the mistakes they made when studying the effects of the 1983 El Nino. There was a research project conducted on the marine ecosystem at the Punta San Juan de Marcona sea lion reserve, a remote point of land on the coast about three hundred miles south of Lima, Peru. The project consisted of an in-depth study of the sea lion and the ecosystem it inhabits; it focused primarily on the behavior of more than fifteen thousand sea lions, the largest sea lion colony in the South American Pacific. Documenting the sea lions living traits for over 10 years, the biologists are also observing behavioral changes produced by El Nino, the same Pacific current that altered oceanic conditions. When El Nino dampens the point in warmer water, the sea lions' prey swims deeper. Consequently, the pups remain with their mothers longer, until they are able to dive themselves to hunt for food.
Another long term study (1983-1991) of marine mammals at Santa Catalina Island, California supplied information on the ecological relationships among three pinniped and nine cetacean species. A significant cutback in the number of California sea lions occurred during and following the winter with the most severe effects from the 1983 El Nino, one of the strongest in over four centuries (Quinn et al.1987) Thus, El Nino served as a natural experiment with the potential for exerting a profound influence on oceanographic conditions off southern California. This storm clearly had the strongest effect on sea surface temperatures at Catalina in 1983-1984.
The annual study period coincided with different periods in the reproductive cycles of the three pinniped species encountered. It was the non-breeding period for California sea lions, whereas it was the breeding time for harbor seals and northern elephant seals (Bartholomew and Boolootian 1960; Odell 1971).
Counts of over 800 sea lions dropped to about 200 in the following years. Interestingly enough, the California sea lions do not reproduce on Catalina's beaches to produce pups each year.
At San Miguel Island, one of the four most important and abundant prey items for sea lions is the market squid. In 1984, El Nino had such severe effects on market squid catches around Catalina that they temporarily vanished. This is a good example of why the 1972 Marine Mammal Protection Act was enacted. This law should have limited the squid fishing, at least for the season when the pups needed it most.
A longer study by Lowry et al. (1992) registered a constant growth in California sea lion pups at several Channel Islands from 1984-1992. The fact that the count of sea lions at Catalina in 1991 were still at one-quarter of their 1983 levels implies that either there was an uncommon influx of sea lions to Catalina in 1983 or that El Nino caused a long-term shift in winter distribution away form Catalina. The last hypothesis seems more likely in light of the fact that "the biological response {to El Nino} was quite modest" despite increased sea surface temperatures (McGowan 1985).
Whole island harbor seal counts varied from 53 (1991) to 267 (1990). The counts were made prior to peak breeding in 1988, 1989, 1991, possible accounting for lower counts in those years. Spawning apparently occurred quite early in 1990 and the 1984 and 1985 counts may have been lower than the 1990 total as a consequence of El Nino.
Returning to the present day El Nino, rescue groups are aware that they are not allowed to embark on the islands and save every creature. The federal law is there for a reason otherwise many well-intentioned people would go out to the island and recover healthy pups that simply were waiting for their others to come back. The concerned public wrote to their congressmen to change this law so they can go out to the islands. Although the sight of sea lions and fur seals perishing is depressing, researchers say that the mortality rate is part of natural selection. Their opinion is that society can only manage humans, not the environment.
Some positive measures have been taken. The Marine Mammal Center in Suasalito, California spent almost $2 million of its annual budget to recover sick pinnipeds, feeding them, and nurturing them and then sending them back into the wild. Back in 1982, during the smaller El Nino, they brought in about 800 sea lions; this year they took in 480.