A Gulf in lockdown: How an enforced ban on recreational vessels increased dolphin and fish communication ranges.

From midnight of 26 March 2020, New Zealand became one of the first countries to enter a strict lockdown to combat the spread of COVID-19. The lockdown banned all non-essential services and travel both on land and sea. Overnight, the country's busiest coastal waterway, the Hauraki Gulf Marine Park, became devoid of almost all recreational and non-essential commercial vessels. An almost instant change in the marine soundscape ensued, with ambient sound levels in busy channels dropping nearly threefold the first 12 h. This sudden drop led fish and dolphins to experience an immediate increase in their communication ranges by up to an estimated 65%. Very low vessel activity during the lockdown (indicated by the presence of vessel noise over the day) revealed new insights into cumulative noise effects from vessels on auditory masking. For example, at sites nearer Auckland City, communication ranges increased approximately 18 m (22%) or 50 m (11%) for every 10% decrease in vessel activity for fish and dolphins, respectively. However, further from the city and in deeper water, these communication ranges were increased by approximately 13 m (31%) or 510 m (20%). These new data demonstrate how noise from small vessels can impact underwater soundscapes and how marine animals will have to adapt to ever-growing noise pollution.

Not so silent spectators: How spectator vessels at international sailing regattas alter marine soundscapes.

International sailing regattas are major sporting events often held within coastal marine environments which overlap with the habitats of marine species. Although races are confined to courses, the popularity of these events can attract large spectator flotillas, sometimes composed of hundreds of motorized vessels. Underwater noise from these flotillas can potentially alter soundscapes experienced by marine species. To understand how these flotillas may alter soundscapes, acoustic recordings were taken around racecourses during the 36th America's Cup in the Hauraki Gulf, New Zealand in 2021. Sustained increases in broadband underwater sound levels during the regatta (up to 17 dB re 1 µPa rms; 0.01-24 kHz) that extended beyond racecourse boundaries (>8.5 km) and racing hours were observed; very likely attributable to the increase in regatta-related vessel activity. Underwater noise pollution from spectator flotillas attending larger regattas should be considered during event planning stages, particularly when events occur in ecologically significance areas.

Automated identification system for ships data as a proxy for marine vessel related stressors.

An increasing number of marine conservation initiatives rely on data from Automatic Identification System (AIS) to inform marine vessel traffic associated impact assessments and mitigation policy. However, a considerable proportion of vessel traffic is not captured by AIS in many regions of the world. Here we introduce two complementary techniques for collecting traffic data in the Canadian Salish Sea that rely on optical imagery. Vessel data pulled from imagery captured using a shore-based autonomous camera system ("Photobot") were used for temporal analyses, and data from imagery collected by the National Aerial Surveillance Program (NASP) were used for spatial analyses. The photobot imagery captured vessel passages through Boundary Pass every minute (Jan-Dec 2017), and NASP data collection occurred opportunistically across most of the Canadian Salish Sea (2017-2018). Based on photobot imagery data, we found that up to 72 % of total vessel passages through Boundary Pass were not broadcasting AIS, and in some vessel categories this proportion was much higher (i.e., 96 %). We fit negative binomial General Linearized Models to our photobot data and found a strong seasonal variation in non-AIS, and a weekend/weekday component that also varied by season (interaction term p < 0.0001). Non-AIS traffic was much higher during the summer (Apr-Sep) and during the weekend (Sat-Sun), reflecting patterns in recreational vessel traffic not obligated to broadcast AIS. Negative binomial General Additive Models based on the NASP data revealed strong spatial associations with distance from shore (up to 10 km) and non-AIS vessel traffic for both summer and winter seasons. There were also associations between non-AIS vessels and marina and anchorage densities, particularly during the winter, which again reflect seasonal recreational vessel traffic patterns. Overall, our GAMs explained 20-37 % of all vessel traffic during the summer and winter, and highlighted subregions where vessel traffic is under represented by AIS.

Noise exposure from commercial shipping for the southern resident killer whale population.

This study assesses vessel-noise exposure levels for Southern Resident Killer Whales (SRKW) in the Salish Sea. Kernel Density Estimation (KDE) was used to delineate SRKW summer core areas. Those areas were combined with the output of a regional cumulative noise model describing sound level variations generated by commercial vessels (1/3-octave-bands from 10 Hz to 63.1 kHz). Cumulative distribution functions were used to evaluate SRKW's noise exposure from 15 vessel categories over three zones located within the KDE. Median cumulative noise values were used to group categories based on the associated exposure levels. Ferries, Tugboats, Vehicle Carriers, Recreational Vessels, Containers, and Bulkers showed high levels of exposure (Leq-50th > 90 dB re 1 µPa) within SRKW core areas. Management actions aiming at reducing SRKW noise exposure during the summer should target the abovementioned categories and take into consideration the spatial distribution of their levels of exposure, their mechanical and their operational characteristics.