ENDANGERED AND THREATENED SPECIES

The list on the right represents threatened or endangered species or subspecies that can be found in or near the boundaries of the Monterey Bay National Marine Sanctuary. Ranking codes for the California Department of Fish and Game's "California Natural Diversity Database" (June 1999) indicate that the Guadalupe fur seal and the salt marsh harvest mouse are extremely endangered within California and throughout their worldwide ranges. Several other species are ranked as "extremely endangered" in California, including the southern sea otter, the California Clapper Rail, the Marbled Murrelet, and three Chinook salmon runs. The winter-run Chinook salmon is ranked as "extirpated" (destroyed or exterminated) in California. All other threatened or endangered species listed here are ranked as "endangered" in California. (The Database does not have ranks for any of the cetaceans or marine turtles.) About 19 percent (26 of 139 species) of the threatened or endangered animals in California can be found living in or near the Sanctuary.

Occasionally a dead sea turtle will wash ashore, giving researchers the opportunity to measure and autopsy its carcass. Sea turtle strandings have been reported by the California Marine Mammal Stranding Network since 1982. In 1999 six leatherback turtles washed ashore in the Sanctuary—a few more than in the last few years, but not an unusually high number. Cause of death is almost always indeterminable due to carcass decomposition, but some scientists suspect that the leading cause of death to turtles at sea is accidental entanglement in fishing gillnets in waters offshore of North and South America.

Despite having been listed as a federal Endangered Species in 1970, leatherback populations have continued to decline in recent years, with extremely fast and alarming declines in the Pacific breeding populations. The nesting colony along the Mexican coast, which in the 1970s hosted tens of thousands of nesting female leatherbacks, has declined at an annual rate of 22 percent for the last fifteen years and is now reduced to 250 nesting females. DNA studies have shown that the leatherbacks that visit the Sanctuary are males and juveniles, mostly from Indonesian nesting grounds. Very little is known about males or juveniles, since only adult females make themselves available for study by hauling out on land to lay eggs. The migration patterns that bring leatherback turtles from far-off nesting sites to Monterey Bay are also unknown. The Sanctuary intends to participate in upcoming leatherback tagging and tracking projects that will provide necessary information about this critically endangered species.

--Jen Jolly
Monterey Bay National Marine Sanctuary

For the last three years southern sea otter numbers have been declining consistently. From a population peak of 2,377 total otters in 1995, the population was last estimated to number just over 2,000. The carcass count remains high, giving no hint that the population will miraculously recover any time soon.

A single reason for the decline cannot be pinpointed. Forty percent of the beachcast carcasses indicate the animal died of infectious disease—an extremely unusual number in nature. Another 20 percent die of trauma: either boat strike, gunshot, or shark bite. For the rest, the cause of death cannot be determined.

A variety of agencies are at work trying to unravel this endangered species mystery. Research funding—although never enough--is being provided by the World Wildlife Fund, The Otter Project, the David and Lucile Packard Foundation, National Fish and Wildlife Foundation, The Goldman Fund, and the Monterey Bay National Marine Sanctuary.

Researchers from the Biological Resources Division of the U.S. Geological Survey (USGS) are studying population dynamics and fisheries interactions. Veterinarians and pathologists from the California Department of Fish and Game (CDFG) Marine Wildlife Veterinary Care and Research Center, U.C. Davis, and USGS's National Wildlife Health Center are studying cause of death and the effects of disease on the sea otter population. Researchers from Michigan State University are studying the relationship between the very high levels of certain pollutants (such as DDT, PCB, and tributyltin) found in sea otter tissues and disease in sea otters. Still other researchers from CDFG are tracing the pollutants to sea otter prey. On-board observers from the National Marine Fisheries Service are determining the impact of gillnet fisheries on the sea otter as well as other marine mammals and birds. The Monterey Bay Aquarium takes in stranded otters -- often pups—and tremendous efforts are made to learn better rehabilitation techniques and return healthy otters to the wild.

The recent declines in the California sea otter population are apparently related to a variety of causes. Only careful research, the sharing of data and expertise, and a broad team approach will help this critical species recover.

--Steve Shimek
The Otter Project, Inc.

In 1999 a total of 282 chicks hatched from 138 nests in the Monterey Bay area, including Wilder, Laguna, and Scott Creeks. Seventy-eight percent of all the nests hatched at least one chick. That was a pretty good start, but in most areas things went downhill from there. On the outer beaches of Monterey Bay only 17 of the 123 chicks that hatched fledged (0.26 juveniles per nest)—far too few to replace adult losses. This shortfall could not be made up by relative success in other areas. For instance, in the pocket beaches north of Santa Cruz (Wilder, Laguna, and Scott Creeks) 15 of 28 chicks fledged (1.07 juveniles/nest). In the Moss Landing salt ponds 68 of 131 hatched, for a fledge rate of 1.17.

Aerial predators were almost surely the cause of poor fledgling success on Monterey Bay beaches. American Kestrels, known to prey on Snowy Plover chicks, were frequently seen on Marina beaches during the nesting season. Northern Harriers were present at the Salinas National Wildlife Refuge during the time that six of seven broods failed. In addition, the number of nesting Killdeers in the refuge was two to three times normal. It is possible that Snowy Plover brood loss might have been affected by competition with nesting Killdeers. At Zmudowski State Beach the culprit was almost certainly the Loggerhead Shrike, another well-known predator of Snowy Plover chicks. The shrikes were seen on the beach constantly during the breeding season and, in fact, were known to take one brood as it hatched. Even though the Moss Landing salt ponds rated as a success, it could have been greater had not harriers preyed on the chicks in the latter part of the season.

At least a couple of successful years are necessary to recover from this bad one. Also, better control of native predators may be needed to increase reproductive success. We hope to live trap and relocate some of these predators in 2000.

--John S. Warriner
Point Reyes Bird Observatory

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