Real and perceived impacts of coastal bottlenose dolphins (Tursiops truncatus) on artisanal fisheries in the southwestern Gulf of Mexico

Abstract

Dolphin-fisheries interactions are increasing worldwide, but direct assessment on their reciprocal impacts are uncommon. Fishers in the Alvarado coast consider dolphins as a plague, and every year they injure or kill these animals incidentally or on purpose. In order to compare perceived and real impacts in fisheries, we applied open questionnaires (twice for validation) from August 2009 to May 2010, in four localities where artisanal fishery is the main economic activity. We also measured actual impacts in situ, on fishing boats; for each operation assessed, temporal-spatial data was recorded along with setting type. All fish caught in the nets was identified to species level and weighted. Interactions with dolphins were classified as neutral (no indication of feeding upon gears) or antagonistic (damage on gear or captures). In total, 100 fishers answered both questionnaires; the most commonly used gear were gillnets (48.0%), hook lines (13.2%) and casting nets (10.1%); and only two genus composed nearly half of their captures, Scomberomorus sp. (40.3%) and Centropomus sp. (8.55%). Gillnetters perceived a wide range of damage: 73% reported losses of $20-100 USD day-1, 80% claimed destruction of 40-100% of their fishing gear, and 70% of them blamed the dolphins; thus they used several methods (80% non-lethal) to divert them from their activities. Conversely, from 19 field trips conducted, we analyzed 48 fishing settings (67.4% gillnets, 21.7% hook lines and 10.9% shrimp nets), resulting in 32 dolphin interaction events (all gillnets). From 136 records of fish captures (51% Scomberomorus sp. and 16% Centropomus sp.), only in 11.0% dolphins damaged the fish (73%) or the gear (27%); thus actual loss was calculated in $7 day-1. Preliminary data suggests this dolphin population may be already declining. Discordances between real and perceived impacts urge the implementation of management strategies and awareness programs to reduce impacts on this species.

Full text

20th Biennial Conference on the Biology of Marine Mammals Dunedin, New Zealand, 9-13 December 2012
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and behavior (acoustics and foraging). Prior to the advent of
Next Generation Sequencing (NGS) technologies, genetic
evidence of diversity was weak because traditional sequencing
methods used only a small portion of mitochondrial DNA and
revealed extremely low worldwide genetic variation and little or
no phylogeographic pattern. In contrast, initial analysis of 139
whole mitochondrial genomes indicated that all of the
recognized ecotypes in the North Pacific and Antarctic
comprised reciprocally monophyletic clades with divergence
times ranging from 150,000 to 700,000 years. Relationships
between ecology and phylogeny in the North Atlantic were less
well resolved, and suggested periodic connections to the North
Pacific and Antarctic. Here we report new NGS analyses of
globally distributed samples that yielded >400 mitogenomes
and nuclear genotypes from 91 SNPs from 128 individuals. The
mitogenome phylogeography still indicates reciprocal
monophyly for some named ecotypes, but greater variability at
low latitudes consistent with larger populations and multiple
dispersal events from the high latitudes to low-latitudes.
Nuclear data also strongly support genetic isolation of
sympatric ecotypes (e.g., North Pacific Transients and
Residents; Antarctic Types B and C) and regional populations
(e.g., the Eastern Tropical Pacific, New Zealand). Concordance
of nuclear and mitochondrial data further support taxonomic
revision to include several species and subspecies of killer
whales. Accurate taxonomy is critical to development of
appropriate management plans at the species or populations
level.
Prey availability and fine-scale ocean structure
shape foraging choices in pygmy blue whales
Morrice, Margie 1, 2; Bellgrove, Alecia 1; Jarvis, Toby 3; Garcia,
Maria 1; Gill, Peter 2; van Ruth, Paul 4
(1) Deakin University, PO Box 423, Warrnambool, Victoria, 3280, Australia
(2) Blue Whale Study, c/- Post Office, Narrawong, Victoria, 3285, Australia
(3) Myriax Pty Ltd, GPO Box 1387, Hobart, Tasmania, 7001, Australia
(4) South Australian Research and Development Institute (Aquatic Sciences),
PO Box 120, Henley Beach, South Australia, 5022, Australia
Corresponding author: margie@bluewhalestudy.org
Pygmy blue whales that migrate to upwelling-influenced coastal
waters off southern Australia are endangered and showing no
signs of recovery. The availability of prey is arguably the most
important factor determining their fitness and movement
patterns. To date, few studies have quantified prey availability
and habitat factors influencing prey at the temporal and spatial
scales relevant to fine-scale foraging of baleen whales. We
predicted that blue-whale prey would be significantly more
abundant in more productive areas of the mid-water depths
across the mid-shelf, and that blue-whale distribution and
foraging behaviour would closely match prey availability. We
used PERMANOVA analyses of prey aggregation descriptors
(derived from high resolution acoustic data) to characterise the
blue-whale prey field in a representative area of the Bonney
Upwelling. These observed patterns of prey were explained
through conceptual and empirical models of their relationships
to habitat features. Blue whales were tracked and their
behavioural responses to prey and other habitat factors were
measured and compared to available habitat elsewhere on the
shelf. The study area was found to be a rich and dynamic
region, with heterogeneity in prey distribution and abundance
over time (years) and space (shelf and water column). The areas
occupied by blue whales were also areas of highest prey
abundance, with the position of upwelled water, and access to
nutrients and surface phytoplankton important explaining
factors. While gross patterns in blue-whale abundance from
aerial surveys didn’t reflect inter-annual patterns in prey
abundance, individual whale-movements are envisaged to
reflect spatial changes in prey distribution and abundance. The
specific habitat context provided here to help explain individual
whale behaviour contributes to the field-based knowledge
needed to build robust state-dependent foraging and fitness
models, and to provide better resolution and predictive power
for population estimates and the critical habitat needs of these
vulnerable whales.
Identification of key seal haul-out areas using
virtual observers
Morris, Chris 1; Lonergan, Mike 1; Duck, Callan 1
(1) Sea Mammal Research Unit, University of St Andrews, East Sands, St
Andrews, UK
Corresponding author: cdm21@st-andrews.ac.uk
Identifying onshore sites that are of key importance to seals can
be useful for conservation and animal welfare reasons as well as
for seal population and/or fisheries management. Delineating
such sites can be difficult in large areas of generally suitable
habitat where the precise locations occupied vary depending on
factors such as tide and weather. We describe a method used to
produce lists of key haul-out areas for harbour seals (Phoca
vitulina) and grey seals (Halichoerus grypus) in Scotland. This
has been developed after new legislation provided seals at
designated sites with additional protection from harassment.
Count data collected during aerial surveys in the summers of
1996-2010 were analysed to identify and define sites used
frequently by high numbers of seals. The entire Scottish coast
was surveyed multiple times during this period. Using a
geographical information system (GIS), ‘virtual observation
points’ with fixed ‘detection’ radii were placed along a
simplified coastline at 100m intervals. These were used to
create a continuous series of count histories and time-weighted
average counts (TWAs) along the coast. Starting with the
highest TWA, important haul-out sites were identified and
combined into polygons. Continuing with the next highest
TWA, this process could then be repeated either until all
recorded sightings lie within a defined polygon or until a certain
percentage of a given population is contained within the defined
areas. The method is very flexible and could be adapted for
various different species, such as seabirds during their breeding
season, by selecting appropriate detection radii and weightings.
Real and perceived impacts of coastal bottlenose
dolphins (Tursiops truncatus) on artisanal fisheries
in the southwestern Gulf of Mexico
Morteo, Eduardo 1, 2, 3; Martínez-Serrano, Ibiza 4, 3
(1) Universidad Veracruzana, Instituto de Ciencias Marinas y Pesquerías,
Boca del Río, Veracruz, 94290, Mexico
(2) Universidad Veracruzana, Instituto de Investigaciones Biológicas,
Xalapa, Veracruz, 91190, Mexico
(3) Laboratorio Veracruzano de Mamíferos Marinos, Acuario de Veracruz,
A.C., Veracruz, Veracruz, 91900, Mexico
(4) Universidad Veracruzana, Museo de Zoología, Facultad de Biología,
Xalapa, Veracruz, 91000, Mexico
Corresponding author: eduardo.morteo@gmail.com
Dolphin-fisheries interactions are increasing worldwide, but
direct assessment on their reciprocal impacts are uncommon.
Fishers in the Alvarado coast consider dolphins as a plague, and
every year they injure or kill these animals incidentally or on
purpose. In order to compare perceived and real impacts in
fisheries, we applied open questionnaires (twice for validation)
from August 2009 to May 2010, in four localities where
artisanal fishery is the main economic activity. We also
measured actual impacts in situ, on fishing boats; for each
operation assessed, temporal-spatial data was recorded along
with setting type. All fish caught in the nets was identified to
species level and weighted. Interactions with dolphins were
classified as neutral (no indication of feeding upon gears) or
antagonistic (damage on gear or captures). In total, 100 fishers
answered both questionnaires; the most commonly used gear
were gillnets (48.0%), hook lines (13.2%) and casting nets
(10.1%); and only two genus composed nearly half of their
captures, Scomberomorus sp. (40.3%)
and Centropomus sp. (8.55%). Gillnetters perceived a wide
range of damage: 73% reported losses of $20-100 USD day-1,
80% claimed destruction of 40-100% of their fishing gear, and
70% of them blamed the dolphins; thus they used several
methods (80% non-lethal) to divert them from their activities.
Conversely, from 19 field trips conducted, we analyzed 48
fishing settings (67.4% gillnets, 21.7% hook lines and 10.9%
shrimp nets), resulting in 32 dolphin interaction events (all

20th Biennial Conference on the Biology of Marine Mammals Dunedin, New Zealand, 9-13 December 2012
!
151!
gillnets). From 136 records of fish captures
(51% Scomberomorus sp. and 16% Centropomus sp.), only in
11.0% dolphins damaged the fish (73%) or the gear (27%); thus
actual loss was calculated in $7 day-1. Preliminary data suggests
this dolphin population may be already declining. Discordances
between real and perceived impacts urge the implementation of
management strategies and awareness programs to reduce
impacts on this species.
Acoustic monitoring of Harbour and Dall’s
porpoises in northern British Columbia, Canada.
Mouy, Xavier 1; Frouin-Mouy, Heloise 1; Martin, Bruce 2; Hall,
Anna 3
(1) JASCO Applied Sciences, Suite 2101 - 4464 Markham Street, Victoria,
British Columbia, V8Z 7X8, Canada
(2) JASCO Applied Sciences, Suite 301 – 32 Troop Avenue, Dartmouth, Nova
Scotia, B3B 1Z1, Canada
(3) AECOM, 415 Gorge Road East, Victoria, British Columbia, V8T 2W1,
Canada
Corresponding author: xavier.mouy@jasco.com
Harbour (Phocoena phocoena) and Dall’s (Phocoenoides dalli)
porpoises frequent the waters of British Columbia, Canada.
Both species produce high frequency clicks in the frequency
band 100-170 kHz, making acoustic discrimination difficult.
While several studies have described harbour porpoise clicks,
very little is known about Dall’s porpoise clicks. The objectives
of our study were to: 1) characterize and discriminate clicks
from harbour and Dall’s porpoise using acoustic and visual
records, and 2) describe effective techniques to automatically
detect and classify these porpoises’ clicks in large
datasets.Three autonomous acoustic recorders (AMAR G3,
JASCO Applied Sciences) were deployed in Chatham Sound
(British Columbia) from September 2012 to March 2013 at 2 to
40 km from Prince Rupert. The recorder’s duty cycle was 428
seconds sampling at 64 ksps, 131 seconds sampling at 375 ksps,
and 1241 seconds sleep for a total cycle time of 1800 seconds.
Porpoise clicks were detected day and night, at all three
recorders. Visually both species were detected in Beaufort 0 - 2,
in the vicinity of at least one hydrophone. Automated detection
of porpoise clicks involved the creation of spectrograms of each
375 kHz recording that was normalized and binarized with a
split window normalizer. Potential porpoise clicks were defined
as time slices in the 100-170 kHz band with an average energy
exceeding an empirical threshold. Porpoise detections were
confirmed only if the ratios of energy in the 100–170 and 30–
100 kHz frequency bands exceeded a second empirical
threshold. Click trains were identified and characterized by a set
of features describing the temporal evolution of click peak
frequencies and inter-clicks intervals. Statistical and clustering
analyses were used to identify groups of click trains with
similar properties. These acoustic groups were then correlated
with visual sightings and known habitat preferences.
Google Haulout: The first synoptic all-digital aerial
survey of gray seals (Halichoerus grypus) in Cape
Cod region of the US Northeast.
Moxley, Jerry 1, 2; Machernis, Abigail 3; Utley, Lydia 4; Stanton,
Sean 1; Halpin, Patrick 2; Johnston, David 1
(1) Duke University, 135 Duke Marine Lab Road, Durham, North Carolina,
28516, USA
(2) Marine Geospatial Ecology Lab, A328 LSRC, Duke University, Durham,
North Carolina, 27705, USA
(3) Duke University Marine Lab, 135 Duke Marine Lab Road, Beaufort,
North Carolina, 28516, USA
(4) Marine Geospatial Ecology Lab, A328 LSRC, Duke University, Durham,
North Carolina, 27708, USA
Corresponding author: jerry.moxley@duke.edu
Gray seal (Halichoerus grypus) populations in the US Northeast
are recovering from near extirpation. Despite 20 years of
expanding haulout locations, growing breeding colonies, and
increasing human interactions, there are no robust population
estimates for this species in U.S waters. To aid management in
understanding the size of recovering seal populations, we
present a synoptic digital aerial survey of all haulout sites
around the Cape Cod region that employs freely-available
imagery and a generalizable method for scaling haulout counts
to estimate total population size. Using imagery with
remarkable resolution available from Google Earth, all haulout
sites in the region were identified, surveyed, and counted for
individual seals (n = 15,321). Survey counts were adjusted for
observer bias derived from comparative estimates of dense
haulouts. Counts were corrected for interspecies mixing with
harbor seals (Phoca vitulina) from existing surveys of common
and accessible haulout sites. Finally, corrected counts of gray
seals (n = 13,818) were then scaled to estimate a regional
population size using a Bayesian hierarchical model that
estimates the probability of observing individuals hauled out
given haulout rates from telemetry data. Using this approach,
we estimate that approximately 68,793 gray seals inhabit the
Cape Cod region during March 2012. This method provides an
inexpensive alternative to effort-intensive field surveys that are
often be limited in both space and time. As the resolution and
availability of global imagery databases like Google Earth
continue to increase worldwide, it may be possible to monitor
other pinniped populations inexpensively using digital surveys
and these methods. Though proven here with a comparatively
data rich population, we see this model as incipient of
inexpensive population survey methods based on freely-
available Google Earth data that revolutionizes monitoring of
remote, inaccessible, or data-poor pinniped communities.
Western Gray Whale Distribution and Abundance
during a 4-D Seismic Survey off Sakhalin Island,
Russia
Muir, Judy E 1; Ainsworth, Laurie 2; Joy, Ruth 3; Racca, Roberto 4;
Bychkov, Yury 1; Gailey, Glenn 5; Vladimirov, Valeriy 6 ;
Starodymov, Sergei 6; Bröker, Koen 7
(1) LGL Limited, 9768 Second St, Sidney, British Columbia, V8L 3Y8,
Canada
(2) PhiStat Research & Consulting, 2733 Kilmarnock Crescent, North
Vancouver, British Columbia, V7J 2Z3, Canada
(3) Department of Statistics & Actuarial Science, Simon Fraser University,
Burnaby, British Columbia, V5A 1S6, Canada
(4) JASCO Applied Sciences (Canada) Ltd, Markham Rd, Victoria, British
Columbia, V8Z 7X8, Canada
(5) Marine Mammal Research Program, Texas A&M University at Galveston,
Galveston, Texas, 77553, USA
(6) Russian Federal Research Institute of Fisheries and Oceanography
(VNIRO), V. Krasnoselskaya St, Moscow, Russia, 107140, Russia
(7) Shell Global Solutions, GK Rijswijk, Den Haag, Netherlands, 2288,
Netherlands
Corresponding author: jmuir@lgl.com
Displacement of marine mammals in response to seismic survey
sound exposure has been reported by several researchers. This
study assessed effects of sound exposure from a 4-D seismic
survey conducted adjacent to the nearshore feeding ground used
by the Western Gray Whale (Eschrichtius robustus) population,
presently listed as critically endangered by the IUCN. Multiple
scan surveys were conducted daily, weather permitting, by four
observation teams at each of seven onshore stations pre, during
and post seismic survey activity. Linear mixed effects modeling
that included fixed effects for detection, state and seismic
covariates, and random effects for station and heterogeneity
among stations assessed changes in mean gray whale sighting
distance from shore. Two-part and mixture Bayesian zero-
inflated hierarchical models with detection, environmental and
space-time effects examined changes in mean daily gray whale
densities in 1 km by 1 km grid cell surfaces. Analyses were
limited by low sample sizes during the pre and post seismic
activity monitoring that made it difficult to distinguish between
normal variation in the distribution and abundance of gray
whales and effects of sound exposure from the seismic survey.
To minimize impacts on WGWs, the survey occurred early in
their feeding season when whales were migrating into the
feeding area and numbers were low. Little survey effort was
possible during the post-seismic monitoring due to unsuitable
visibility conditions in bad weather and fog. The need to
address the increasing numbers of migrating gray whales in the
monitored area also complicated the analyses. No significant