Movements of sharks at seamounts and island, biotic “hot spots”, relative to marine protected areas in the eastern Pacific Ocean Corridor
Klimley, Pete1, Randall Arauz2, Sandra Bessudo3, Alex Hearn4, Hector Guzman5, Scott Henderson6, James Ketchum1, George Schillinger7, and German Soler3 1
Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, California, U.S.A. 2 Programa Restauración Tortugas Marina, San José, Costa Rica 3 Fundación Malpelo/MarViva, Bogotá, Colombia 4 Department of Marine Research and Conservation, Charles Darwin Foundation, Puerto Ayora, Galapagos Islands, Ecuador 5 Conservation International, Puerto yora, Galapagos Islands, Ecuador 6 Instituto Smithsonian de Investigaciones Tropicales, Balboa, Panama 7 Hopkins Marine Station, Stanford University, Pacific Grove, Monterrey, California, U.S.A.
Pelagic Sharks are Attracted to Seamounts
• Seamounts are volcanos, that rise above the seafloor due to the deposition of basalts from eruptions over geological time. • They often occur in chains, natural migratory corridors for fish.
Distribution of Pelagic Fishes •Are all oceanic species nomadic, constantly moving? •Do they remain at seamounts and islands during migrations? Some species reside at trophic “hot spots” such as the Espiritu Santo Seamount in the Gulf of California.
Why do they aggregate at these locations?
These sites are more productive than surrounding waters.
Remote Sensing of Biota • We need to use multiple methods of observation. • One useful for recording movements and distribution of fishes is ultrasonic telemetry.
• Tagged individuals can be followed continuously in a ship. • Many fish with coded, “signature”, beacons can be detected by monitors moored at a site. • Their appearance at the site over a 24 hr day can be plotted on a “clock” diagram.
Pelagic Fishes Adapted to Pacific Plate? Hammerheads have been shown to exhibit geomagnetic topotaxis, moving along magnetic maxima (ridges) and minima (valleys) associated with lava flows.
The oceanic plate is sub-ducting below the continental plate, and basalt rises through fractures in volcanic eruptions to produce seamounts and islands, which exhibit magnetic dipoles.
Residence and Migratory Pathways Between Islands in the Eastern Pacific Gulf of California
Revillagigedo
Clipperton Cocos Malpelo
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Galapagos
We are setting up arrays of tag-detecting monitors to determine the degree of residency and movement between islands and seamounts
Insular Studies with Monitor Arrays
Mapelo Island (Colombia)
Cocos Island (Costa Rica) El Monstruo
David Rock
Sandra Bessudo and German Soler Randal Arauz
Darwin Island Wolf Island
Installation 2006 Installation 2007
Wolf and Darwin Islands of the Galapagos (Ecuador)
Roca Redonda
Cousins Rock Gordon Rocks
Nameless Rock
Floreana Seamount
Alex Hearn, James Ketchum, George Shillinger
Site Specificity at Islands WolfWestBay_HH_Aug07 0000 2200
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Only six of these sharks visited site on other side 2.5 km away, and for only brief times during month of August.
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Eight monitors deployed at Wolf Island.
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WolfWhaleRock_HH_Aug07 0000 2200
Fifteen hammerhead sharks tagged during August 2007 at Whale Rock return repeatedly to the site.
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Further Evidence of Site Specificity at Islands Galapagos shark tagged and tracked for two days by boat spent a disproportionate amount of time at the Rockfall and eastern side of crater.
Hammerhead shark tagged and tracked by boat spent majority of time at the Rockfall.
Darwin
38 km
Wolf
Residency and Movements between Hot Spots in Galapagos Islands • Hammerhead sharks stay at Darwin and Wolf Islands for periods ranging from a week to 12 months, yet frequently move between the islands. • Note detections at Wolf (clear circles) interspersed with detections at Darwin (solid circles.
Movements between: “Stepping Stones”, Islands off South and Central America
Darwin
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Malpelo
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Cocos
• Ninety two coded tags are deployed at the Galapagos, 30 at Isla Malpelo, and 24 at Cocos Island. • Of first 15 tags at Galapagos, two were later detected at Cocos, one returned to the Galapagos Islands. Sex: female Size: 200 cm
Total distance = 693 km Time = 15 days, 23 days
Mean swimming speed = 0.54 m/s, 0.33 m/s
Satellite Tracking Insular versus Oceanic Movements Placing SPOT (position) and SPLASH (position + depth) satellite tags on Hammerhead and Galapagos sharks in the Galapagos Archipelago off Ecuador – high accuracy, +1 km Hammerhead sharks are caught by hook and line, placed in sling, lifted aboard vessel, and satellite tag applied while water is passed over gills
Hammerhead Sharks: Insular versus Oceanic Movements v=0.59, n=15
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Perhaps, even here
SPOT-tagged hammerhead shark remains close to Wolf Island until it makes directed migratory movement in southeastern direction to a second “hot spot”.
Make reserve here /s m
v=0.26 m/sec, n =33
SPLASH-tagged hammerhead shark remains close to Wolf Island until it makes a rapid, directed movement in northwesterly direction to a second “hot spot”.
Make reserve here
Galapagos Sharks: Insular versus Oceanic Movements Shark 1 (ID 6109) migrates at rate of 0.8 m/s in ocean, while other sharks swim at from 0.10-0.25 m/s while observed patrolling near island.
Note Galapagos sharks remain near Wolf and Darwin Islands, yet one makes directional, long distance migration.
Home range kernals of Galapagos Sharks centered at Wolf and Darwin as well as Isabella Island
Perhaps, even here
Make reserve here
“Yo-yo� Swimming
Out of range of surface gill net and long line fisheries, and hence risk of capture negligible during oceanic movements.
Conclusions
• Seamounts and islands are biotic “hot spots” • Sharks remain at these sites for long periods of time, and then move to other hotspots. • The movements between these sites are continuous and directed. • The site attachment to seamounts and islands indicates that we should concentrate our management efforts, and perhaps create zones of no fishing at certain sites and times of the year. • Certain sites might be deemed marine reserves because the advantages of ecotourism exceeds those of fishing.