10.5061/DRYAD.G98B456
Jacoby, David
Zoological Society of London
Ferretti, Francesco
Virginia Tech
Freeman, Robin
Zoological Society of London
Carlisle, Aaron
University of Delaware
Chapple, Taylor
Oregon State University
Curnick, David
Zoological Society of London
Dale, Jonathan
Stanford University
Schallert, Robert
Stanford University
Tickler, David
University of Western Australia
Block, Barbara
Stanford University
Data from: Shark movement strategies influence poaching risk and can guide
enforcement decisions in a large, remote Marine Protected Area
Dryad
dataset
2019
Spatial networks
Carcharhinus albimarginatus
illegal fisheries
telemetry
elasmobranch
Carcharhinus amblyrhynchos
mobility patterns
MPA
Fondation Bertarelli
https://ror.org/04h7fev25
2020-05-12T00:00:00Z
2020-05-12T00:00:00Z
en
https://doi.org/10.1111/1365-2664.13654
36199838 bytes
5
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Large, remote marine protected areas (MPAs) containing both reef and
pelagic habitats, have been shown to offer considerable refuge to
populations of reef-associated sharks. Many large MPAs are, however,
impacted by illegal fishing activity conducted by unlicensed vessels.
While enforcement of these reserves is often expensive, it would likely
benefit from the integration of ecological data on the mobile animals they
are designed to protect. Consequently, shark populations in some protected
areas continue to decline, as they remain a prime target for illegal
fishers. To understand shark movements and their vulnerability to illegal
fishing, three years of acoustic tracking data, from 101 reef-associated
sharks, were analysed as movement networks to explore the predictability
of movement patterns and identify key movement corridors within the
British Indian Ocean Territory (BIOT) MPA. We examined how space use and
connectivity overlap with spatially-explicit risk of illegal fishing,
through data obtained from the management consultancy enforcing the MPA.
Using individual-based models, the movement networks of two sympatric
shark species were efficiently predicted with distance-decay functions
(>95% movements accurately predicted). Model outliers were used to
highlight the locations with unexpectedly high movement rates where MPA
enforcement patrols might most efficiently mitigate predator removal.
Activity space estimates and network metrics illustrate that silvertip
sharks were more dynamic, less resident and link larger components of the
MPA than grey reef sharks. However, we show that this behaviour
potentially enhances their exposure to illegal fishing activity. Synthesis
and applications. Marine protected area (MPA) enforcement strategies are
often limited by resources. The British Indian Ocean Territory MPA, one of
the world’s largest ‘no take’ MPAs, has a single patrol vessel to enforce
640,000 km2 of open ocean, atoll and reef ecosystems. We argue that to
optimise the patrol vessel search strategy and thus enhance their
protective capacity, ecological data on the space use and movements of
desirable species, such as large-bodied reef predators, must be
incorporated into management plans. Here, we use electronic tracking data
to evaluate how shark movement dynamics influence species mortality
trajectories in exploited reef ecosystems. In doing so we discuss how
network analyses of such data might be applied for protected area
enforcement.
Acoustic detection data 2013-2016All acoustic detection data used for
analysis of silvertip and grey reef sharks in the British Indian Ocean
Territory between 2013 and 2016. Receiver locations have been removed from
the data and are referred to by station name.Acoustic Data DJacoby.csv
Acoustic tags were surgically implanted in 101 sharks reef sharks during
February-April between 2013 and 2016. Sharks were tracked for three years
across five isolated atoll systems in the north of the British Indian
Ocean Territory Marine Protected Area. The study array consisted of a
total of 52 Vemco acoustic receivers (Vemco, Nova Scotia, Canada, 46
VR2Ws, plus four VR2W-UWM and two VR4Gs) with additional receivers placed
further afield in the archipelago excluded from the analyses due to later
deployment dates or lack of data from this cohort of animals. Sharks were
caught at various locations around the northern atolls using hand-lines
with barbless circle hooks and brought alongside or into the boat. Vemco
V16 acoustic tags were surgically implanted into the shark and had a
expected duration of up to 10 years. Data were downloaded on an annual
basis and filtered for false detections prior to finalising the data for
analysis.
British Indian Ocean Territory (BIOT)