shark tagging in the galapagos islands 2012
Post on 16-Apr-2017
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The Eastern Tropical Pacific Ocean Seascape
Cocos Island (Costa Rica)
Malpelo Island (Colombia)
Galapagos Islands (Ecuador)
Also Coiba & Las Perlas (Panama)Gorgona (Colombia)Isla de la Plata, Machalilla (Ecuador)
2.1 million km2
Why sharks?•Sharks are a key group in the marine ecosystem•Apex predators, drive natural selection processes•Distinct evolutionary group from bony fishes•Slow growth, late onset of sexual maturity, low fecundity – intrinsic characteristics which make sharks vulnerable.
•Recent studies have shown declines in shark populations in almost every single population studied
Internal reproduction and live young (mostly).
Threats to shark populations
Focus: Research Species
Rhincodon typusCarcharhinus galapagensis
Sphyrna lewini
Focus: Research QuestionsNations encouraged to develop Shark Plans of Action to manage and conserve their shark populations• How to delimit stocks?• No baseline from which to follow trends
Do hammerheads display residency at particular sites?Do hammerheads move between sites?Do they display synchronous behavior?Is their connectivity between MPAs on a regional scale?
What are the mechanisms behind site preference and migrations?
Shark Tagging: ultrasonic coded tags
VEMCO V16 coded tags. Emit train of pulses at 69 KHz.
VEMCO VR2 listening stations (and temp logger), deployed on subsurface moorings
Tags are attached to darts and placed on pole spears. Free divers descend onto sharks and insert tag behind the dorsal fin, at a distance not greater than 50 cm from the shark.
Shark tagging: Manual tracking
Shark tagging: Satellite tags
Shark tagging: Visual Census
Ultrasonic listening array in Galapagos
Darwin
Wolf
Roca Redonda
Seamount 90
Leon Dormido
Marshall PointCousins
Academy BayNameless
Gordon
Overall animals tagged in Darwin & Wolf
Species Ultrasonic SPOT/SPLASH PAT Tracking
Hammerhead 149 14 - 7
Galapagos 23 4 12 1
Whale Shark 5 24 1 0
Silky 7 5
Blacktips 7 6
What have we learned so far?
•Hotspots and site fidelity
•Seasonal changes in abundance
•Nocturnal foraging behavior
•Movements between islands
•Long distance migrations
Hotspots and site fidelity
Census data showed greatest abundance in January, and always on eastern side of Wolf
Tagging data showed the same preference for east coast
Hotspots and site fidelity
The largest abundances of species were along the eastern coast of the island.
Scalloped hammerhead shark
Crevelle and green jacks
Steel pompano
Galapagos shark
Bottlenose dolphin
Snappers
Yellowfin tuna
Manual Tracking
The Galapagos shark patrols the entire island each day, never more than 200 m offshore, but it prefers the area between Shark Point and Rockfall
The hammerhead hangs around Shark Point during the day, but heads out to sea at night, making deep dives (foraging?)… similar pathways each night… how does it navigate?
Hotspots and site fidelity
Proposed predominant current direction
The Arch “hotspot”
N
Female hammerhead left Darwin Island 4 and arrived at Wolf 7 Dec 2008.
Detected at Elephant Rock (ER) at 1312 hrs and stayed within range of monitor for only 24 min
Spent next three weeks between Rockfall, Shark Point, and East Bay
Inter-island movements
02-Jul-06 10-Oct-06 18-Jan-07 28-Apr-07 06-Aug-07 14-Nov-07 22-Feb-08 01-Jun-08 09-Sep-08 18-Dec-08 28-Mar-09159
13172125293337414549535761656973778185899397
101105109
Wolf
Cocos
Darwin
Roca Redonda
Malpelo
Date
Shar
k N
umbe
r
Loss of Darwin Arch Monitors
Regional Connectivity
•Three sharks from Galapagos migrated to Cocos (one also returned)•Three sharks from Malpelo migrated to Cocos (one continued to Galapagos)•No apparent connection Galapagos north vs. Galapagos centre•Connectivity with coastal areas?
The next step – ontogenetic migration?Cocos ?
Ecuador ?
Mangrove bays?
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