• From Monterey Bay to Papua, Indonesia
in Leatherback Conservation Inspire Hope
• Jellyfish Population Trends in Southern Monterey Bay from 2000 to 2005
|From Monterey Bay to Papua, Indonesia
in Leatherback Conservation Inspire Hope
The Pacific leatherback turtle, Dermochelys coriacea, a seasonal visitor to the Monterey Bay National Marine Sanctuary, is listed as a critically endangered species on the World Conservation Union (IUCN) Red List. Leatherback sightings occur within the sanctuary primarily during late summer and fall, when these sea turtles arrive at our coastal waters to exploit large aggregations of their jellyfish (Scyphomedusae) prey. Although the leatherback is the largest living reptile, it is cryptic at sea and sighted mainly by those who work on the water (fishermen, marine scientists and whale-watch operators).
Leatherbacks nest at beaches in tropical latitudes, and it was long thought that the local visitors originated from nearby colonies in Mexico and Costa Rica. In the late 1990s, however, DNA
analysis of skin samples from stranded turtles and those caught incidentally in U.S. fisheries revealed that West Coast leatherbacks were in fact nesting at beaches in the western Pacific (Indonesia, Papua New Guinea [PNG] and Solomon Islands). In September 2000, collaborating with Dr. Scott Eckert, who pioneered satellite-tag attachment methods, we successfully captured two free-swimming leatherbacks in Monterey Bay and released them with
satellite-linked transmitters. The telemetry data confirmed the results of our genetic studies: leatherbacks encountered off central California originate from western Pacific nesting beaches. (See Figure 1.)
|World Wildlife Fund-Indonesia partners Julius Lawalata, Creusa Hitipeuw and Yulianus Thebu prepare to release a leatherback outfitted with a satellite transmitter in Monterey Bay. (Photo courtesy of John Douglas, Moss Landing Marine Laboratories)
Since 2000, we have tagged 29 additional leatherbacks within the Monterey Bay and Gulf of the Farallones National Marine Sanctuaries and 43 at western Pacific nesting beaches. The results of these efforts have revealed that leatherbacks in the western Pacific region, although considered a single genetic stock, comprise multiple foraging populations. Turtles that nest during the winter months undertake migrations to the south, while those that nest during summer months move to northern foraging grounds, including the North American West Coast. The combined results have fundamentally changed the scope of conservation efforts for leatherback turtles found off the U.S. West Coast.
The Recovery Plan (by NOAA Fisheries and the U.S. Fish and Wildlife Service) for the Pacific leatherback identifies key areas
of research and conservation that will be necessary to ensure its survival, including 1) identifying stock ranges, 2) determining movement patterns and foraging habitat and 3) censusing and protecting nesting populations. In particular, protecting nesting beaches has been proven to work well in restoring sea turtle populations. In the Gulf of Mexico, this tactic was effective at halting the extinction of the Kemp's ridley, one of
the most critically endangered sea turtles in
the world during the 1970s. The huge effort, combined with additional measures to protect ridleys from coastal fishery mortality, resulted in the gradual recovery of the species during the 1990s. Long-term nesting beach protection has also resulted in increases of once-depleted leatherback populations in the Caribbean. However, egg protection alone may be insuf-ficient to reverse the severe declines in the
eastern Pacific leatherback rookeries in Mexico and Costa Rica, and it did not prevent the extinction of the Malaysian rookery at Terengganu. It is clear
that a holistic approach will be required that also addresses at-sea threats.
In 2003, a landmark meeting in Bellagio, Italy brought together a group of biologists, economists, legal scholars, conservationists and fishermen from around the Pacific to develop a new multidisciplinary approach to dealing with declining sea turtle populations. The Bellagio Blueprint for Action on Pacific Sea Turtles (see www.worldfishcenter.org/news/Press/Jan04/seaturtles_6Jan04.htm) calls for a massive mobilization to protect all remaining nesting sites around the Pacific from unsustainable human harvest,
predation and habitat destruction. In addition, threats at sea must be reduced by strengthening and coordinating existing Pacific conservation and fisheries treaties as well as facilitating transfer of new turtle-friendly fishing technologies to multinational fishing fleets.
To meet these goals, we have expanded our work to include not only local research on leatherbacks off central California but also
a variety of conservation and research initiatives in western Pacific island nations. We recently conducted aerial surveys in Papua
(eastern Indonesia) and PNG that showed large numbers of nesting leatherbacks remaining only on a few beaches in Papua. This underscores the need to protect these last remaining rookeries in the Pacific before it is too late. Efforts to establish coordinated
and sustained nesting beach conservation are now getting underway in Papua and throughout the western Pacific. With the help of
local community-based organizations, government and university biologists, and Word Wildlife Fund researchers, we are training local villagers to monitor the nesting beaches, evaluate hatching success and attach satellite-linked transmitters to nesting turtles.
A cooperative international program involving local villages and non-governmental, governmental and fishery management organizations has recently been established and is gaining momentum. These new developments have inspired cautious optimism about the future of the western Pacific leatherback.
|Figure 1. Satellite-tracked leatherback movements from nesting beaches in Papua, Indonesia and from foraging areas off the California coast in 2003-2004 (Dutton et al., unpublished) GMT map by Denise Parker
Known by different names throughout beaches in the western Pacific -- trousel, penyu-belimbing, leddebak, tabob -- the leatherback has long been an important part of local cultures and traditions. With new awareness that 'their' turtles travel to other locations
near and far across the Pacific, our colleagues in PNG and Papua are now working with a broad international community to ensure the survival of the leatherback for future generations.
Within the coastal central California ecosystem, including the sanctuary, foraging populations of leatherback turtles are relatively safe; however, 'our' turtles will remain at risk unless we are able
to expand our understanding of the entire ecosystem inhabited
by these highly mobile marine reptiles. Leatherbacks inhabit an ecosystem that includes not only the sanctuary but extends across the Pacific Ocean, nearly one third of the way around the globe.
In this case, ecosystem-based management requires a broad scope to achieve successful conservation of this species at all foraging grounds, nesting beaches and on the migratory routes that connect them.
As they say in Papua New Guinea, Yumi mas lukautimi gud, trousel blong ol pikinini i kam behain: "We must take care of the turtles, for they belong to the children of the future."
Scott R. Benson and Peter H. Dutton
NOAA Fisheries -- Southwest Fisheries Science Center
|Jellyfish Population Trends in Southern Monterey Bay from 2000 to 2005 |
Jellyfish are important in their ecosystems as predators, prey and hosts of symbiotic organisms. Most jellies eat small animals, including copepods, larval invertebrates and fish eggs. In turn, they are preyed upon by ocean sunfish, Mola mola, and leatherback sea turtles, Dermochelys coriacea. Moribund jellies are eaten by a
benthic army of crabs, sea stars and anemones. Jellies are also hosts of symbiotic fishes and crabs. Young fishes use jellies as safe havens from predators, darting under jellyfish bells when danger approaches. Swimming larvae of slender crabs, Cancer gracilis, land on jellies and eat some of their parasites while the crabs are transported to new habitats.
Factors affecting seasonal abundance of northeast Pacific jellies are poorly understood. The animals tend to aggregate in locations with particular physical properties. For example, jellies may often be found at the boundary between two different water masses. They may also be found at the surface in the "slicks," or calm water trails, seen on the surface of the bay on flat days. Annual seasonal population abundance patterns for local jellyfish species have been clearly observed by Monterey Bay Aquarium (MBA) staff while collecting animals for display and research. (See Figure 1.)
|Figure 1. Seasonal population abundance of studied Monterey Bay jellies for the years 2000-2004 versus 2005. The
number of Xs indicates relative abundance.
From 2000 to 2004, jellies were
abundant in Monterey Bay. Pacific sea nettles, Chrysaora fuscescens (Figure 2A), typically arrived during summer
and fall. Purple stripe jellies, Chrysaora
colorata (Figure 2B), were usually
present in large numbers during the
summer and sporadically throughout the year. Egg yolk jellies, Phacellophora camtschatica (Figure 2C), were typically present for only the summer months. Moon jellies, Aurelia labiata (Figure 2D), were common year-round from 2000 to 2004. Moon jellies
are food for C. fuscescens, C. colorata and P. camtschatica. There were also a number of other smaller jellies, ordinarily arriving in the spring and carrying on through the summer.
In contrast, 2005 was a barren jelly-hunting season, with two exceptions. Egg yolk jellies arrived two months early, stayed three months late and were exceedingly abundant. (See Figure 1.) Purple stripe jellies were punctual and more abundant than in years past. However, moon jellies, Pacific sea nettles and the smaller jellies were not present at survey sites from January through September. One possible explanation for the lack of smaller jellies was the early arrival of large numbers of jellyfish-eating egg yolk jellies, capable of clearing most gelatinous prey from large volumes of water. Purple stripe jellies may have survived the onslaught because they are strong, active swimmers and are large enough to escape predation from egg yolk jellies.
In October 2005, the number of egg yolk jellies gradually decreased, and in the last week of the month, large moon jellies (that were record-breaking in size) appeared. In the late 1990s,
the largest Pacific moon jellies collected by the aquarium had
maximum bell diameters of about 40 centimeters. In 2002, MBA staff collected moon jellies measuring 44 centimeters in diameter, in 2004 some were 44.5 centimeters wide and in October 2005,
we collected specimens with bell diameters of 45 centimeters. Within physiological tolerances, growth of Pacific moon jellies increases with temperature. In 2005, unusual summer jelly population patterns were also observed in southern California. Countless egg yolk jellies and black sea nettles, Chrysaora achlyos, arrived
unexpectedly in southern California waters. Black sea nettles live in warmer water and do not normally occur in Monterey Bay. However, this summer a large black sea nettle was observed under the floating fuel dock in Monterey Harbor.
|Figure 2. (A) Pacific sea nettle, Chrysaora fuscescens; (B) purple stripe jelly, Chrysaora colorata; (C) egg yolk jelly, Phacellophora camtschatica; (D) Pacific moon jelly, Aurelia labiata (Photo Chad Widmer)
This year was an unusual one all around the United States. In Monterey Bay the squid, salmon and jelly fishing seasons were lackluster. Southern California saw huge red tides and unusual
jelly blooms. Midwest states reported more summer rain than
normal, and there were two category-five hurricanes in the Gulf
of Mexico. It leaves one to wonder if a poor jelly-hunting season and the rest are linked to global warming or part of normal,
large-scale temperature oscillations. Population studies for jellies of southern Monterey Bay will continue at MBA in order to
understand better how global climate change and local jellyfish abundance patterns may be related.
Chad L. Widmer
Monterey Bay Aquarium