DOI: 10.5061/dryad.h18931zjx
title: Dolphin behavior vessel regulations

description: Vessels cause considerable disturbance to cetaceans world-wide, with
 potential long-term impacts to population viability. Here we present a
 comprehensive review of vessel impacts to cetacean behavior in Australian
 waters (2003-2015), finding inadequate protections to be in place. The
 majority of these studies found trends of decreased animal travel and
 resting behavioral states as well as low compliance to regulations, and
 they recommended further regulatory action such as greater enforcement or
 monitoring, or passive management strategies. As a case study, we
 conducted the first field assessment of vessel compliance with the
 Wildlife (Marine Mammal) Regulations 2009 in Gippsland Lakes, Australia,
 and provide the first assessment of the endangered Gippsland Lakes
 Burrunan dolphin (Tursiops australis) population’s behavioral ecology.
 Dolphin behavior and vessel regulation compliance data were collected
 during boat-based surveys of Gippsland Lakes from July 2017 to January
 2018, with a total of 22 dolphin group sightings resulting in 477
 five-minute point samples. 77% of dolphin sightings involved vessel
 interactions (within 400 m), and 56 regulation breaches were observed.
 These breaches were most severe in summer (mean = 4.54 breaches/hour).
 Vessels were found to alter dolphin behavior before, during, and after
 interactions and regulation breaches, including increased mating (mate
 guarding) and milling behavioral states, and increased ‘fish catch’, ‘high
 leap’ and ‘tail slap’ behavioral events. These behavioral changes may
 indicate masking of the dolphins' acoustic communication, disturbance
 of prey, increased dolphin transition behaviors, and/or induced stress and
 changes to group structure (including increased mate guarding). While our
 results provide evidence of short-term altered behavior, the potential for
 long-term effects on population dynamics for this threatened species is
 high. In the context of reported inadequate cetacean protection
 Australia-wide, our management recommendations include greater monitoring
 and enforcement, and the utilisation of adaptive management.
description: Boat-based surveys were
 conducted across the Gippsland Lakes, Australia, in daylight hours during
 Austral Winter (July) and Spring (September) 2017, and Summer
 (December-January) 2017-2018. Survey periods were chosen to capture
 seasonal differences and peak (summer) and off-peak tourism periods.
 Surveys were only conducted on days of low wind (&lt; 15 knots) and
 good visibility, enabling a 600 metre ‘survey-zone’. A 2C research vessel,
 5.7m Ensign 570 powered by 90 hp Mercury engine, was driven along
 pre-determined line and zig-zag transects across the Gippsland Lakes
 system at depths ≥2 m, at ≥10 m from shore. Continuous horizon scans were
 conducted to sight Burrunan dolphins, with two to four researchers on
 board. The study utilised opportunistic observations of vessel-dolphin
 interaction rather than controlled experimental vessel approaches.
 Methodologies were approved by the Victorian State Government’s
 (Agriculture Victoria) Wildlife and Small Institutions Animal Ethics
 Committee (WSIAEC 33.14) and RMIT University Animal Ethics Committee, and
 conducted under Victoria State Government Wildlife Act 1975 Research
 Permit (Permit number 10008600). Once dolphins were sighted,
 observers recorded dolphin group behavioral state and vessel interaction
 period through point sampling every five minutes. Dolphin behavioral
 events and vessel violation category were recorded through continuous
 sampling. Vessel observation included 11 vessel types to provide an
 assessment of vessel impacts across industries (fishing, tourism, and
 recreational). Focal study was conducted on whole dolphin groups rather
 than individual dolphins to maximise sample size. A group was defined as
 more than one dolphin within 800 m of each other engaging in the same
 behavioral state and, if travelling, travelling with the same heading. The
 primary behavioral state was defined as the behavior in which &gt; 50%
 of the group was engaged. In the final survey period, vessel behavior was
 observed continuously to account for the high vessel traffic during this
 period. The minimum observation period for vessel violation category
 (before, during or after vessel interaction or violation) was five
 minutes. Data
 underwent a series of processes to ensure accuracy but maintain optimal
 sample size. All behavioral data were collected by one trained observer to
 minimise observer error, and were validated by the senior observer. An
 adapted ‘before-during-after’ analytical design was used in this study.
 The data were divided into a single-exposure dataset (only including data
 from the first vessel interaction and first vessel violation observed in
 the sighting), and a repeated-exposure dataset (including data from the
 whole sighting). Mean vessel interactions (and violations) per hour of
 sighting were calculated by dividing the total recorded number of
 interactions (and violations) from unique vessels by the total dolphin
 sighting hours. The objective for this case study was to assess if the
 variation in Burrunan dolphin surface behavior in Gippsland Lakes is
 driven by both seasonal differences and/or vessel disturbance. To test
 this, multivariate analyses of variance (MANOVAs) were run in SPSS (IBM
 SPSS Statistics 25). The Tukey Honestly Significant Difference test (Tukey
 HSD) was applied as a post-hoc test to identify significant differences
 between means.
description: There are no missing values. Raw data contains five-minute
 observations with presence/absence and count data (where
 applicable).