An example of a spectrogram of a vessel closely approaching the recording device. In this example, the vessel is the closest to the device just after 80 seconds. This is an example of behavioral category CPA, the closest point of approach, with a characteristic "bath tub" shape indicative of a Doppler Effect. CPAs are very likely inside of the marine park.
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An example of a CPA with a maneuver (CPA+M) vessel signature where the CPA is beginning but incomplete and there are breaks in the spectrogram as the vessel approaches (indicating a change in gears).
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An example of a spectrogram of a transiting vessel. This is an example of behavioral category TA, transit level A, which are further than a CPA but still produce broadband energy. TAs can be inside or outside of the marine park.
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An example of a TA with a maneuver (TA+M) where a vessel reduces speed, idles, then shifts back into gear. These take place inside or outside of the marine park.
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An example of a spectrogram of a distant vessel with a peak frequency at 1.25 kHz. This is an example of behavioral category TB, transit level B, which are more distant and are unlikely to be inside of the park.
The NEFSC Passive Acoustics group is collaborating with the Australian government at Parks Australia to assess the presence of vessels in protected Australian Marine Parks. Parks Australia is currently developing an acoustic monitoring program using SoundTraps (Ocean Instruments). The main goals for this program are to improve our understanding of vessel use of Australian Marine Parks by small vessels and to inform compliance risk planning and management. Australian Marine Parks offer protection for hundreds of species, ranging from blue whales to critically endangered grey nurse sharks and thousands of fishes. In National Park Zones of Australian Marine Parks, fishing and many other commercial activities are prohibited in order to preserve habitats and protect species. Passive acoustics can be used to differentiate vessel behavior such as transiting and maneuvering in the marine soundscape.
A map of the current and potential future sites off the eastern coast of Australia where acoustic recorders were and will be deployed. The marine park boundaries of A) Solitary Islands [Pimpernel Rock], B) Cod Grounds, and C) Lord Howe (Middleton Reef and Elizabeth Reef) Marine Parks are outlined in the insets. Solitary Islands Marine Park currently has two acoustic recorders deployed; Cod Grounds Marine Park has one. An oceanic feature, Pimpernel Rock, is denoted between the recorders at Solitary Islands Marine Park. Given the success of the pilot project, SoundTraps will be deployed in Lord Howe Marine Park at Middleton and Elizabeth reefs.
Combining data collected through passive acoustics with environmental variables, such as lunar phase or wind speed, or human constructs, such as weekends versus weekdays, helps us to identify factors that may influence when illegal vessel activities occur.
From the pilot data alone, we detected 240-364 discrete vessels transiting near the three recording sites. Using sound propagation modeling, we determined that 43 discrete vessels were present within the boundaries of Solitary Islands Marine Park at Pimpernel Rock during the months of August and September, 2018. We were further able to inform Parks Australia of conditions that may lead to more illegal activity in these sites. Vessels found to be within Solitary Islands Marine Park at Pimpernel Rock were most common on weekdays (Tuesday-Thursday) and were most commonly within park boundaries between 05:00 and 18:00 AEST (peak times occurred between 15:00 and 18:00 AEST). Vessels were also more likely to be within the park when wind speed averaged less than 20 km/hr across consecutive days.
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Total daily acoustic vessel presence derived from the pilot recording sites, one in Cod Grounds Marine Park and two in Solitary Islands Marine Park (East and West Pimpernel). The total number of hours that a vessel was present is plotted against recording date, with weekends shown in light blue and weekdays in dark blue. Average wind speed (km/hr) for each day of the pilot study period is shown and days with full moon and new moon are denoted in the legend. Partial recording days are denoted with asterisks beneath the bars.
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Daily acoustic vessel presence of vessels determined to be within the boundaries of Solitary Islands Marine Park at Pimpernel Rock. The total number of hours that a vessel was present is plotted against recording date, with weekends shown in light blue and weekdays in dark blue. Average wind speed (km/hr) for each day of the pilot study period is shown. Partial recording days are denoted with asterisks beneath the bars.
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The number of discrete acoustic vessels recorded by the Solitary Islands Marine Park acoustic recorders (East and West Pimpernel) plotted against day of the week. Vessel presence is subdivided into each vessel behavioral category defined as closest point of approach (CPA), CPA with a maneuver (CPA+M), transit level A (TA), TA with a maneuver (TA+M), and transit level B (TB).
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The number of discrete acoustic vessels recorded by the Solitary Islands Marine Park acoustic recorders (East and West Pimpernel) plotted against hour of day to reveal diel patterns. Vessel presence is subdivided into each vessel behavioral category defined as closest point of approach (CPA), CPA with a maneuver (CPA+M), transit level A (TA), TA with a maneuver (TA+M), and transit level B (TB).
Identifying vessel activity trends allows Parks Australia to better allocate limited compliance resources to marine parks where and when compliance risk is likely to be high. Furthermore, using remotely sensed acoustic data for monitoring enhances our understanding about the Australian marine soundscape without needing daily human presence at each site. Through this internationally collaborative project, we hope to help Parks Australia monitor their ecologically important ocean resources in an efficient manner.
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An example of a spectrogram with humpback whale song and sounds of breaching or tail slapping.
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An example of a spectrogram containing dolphin whistles and snapping shrimp.
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An example of a spectrogram containing the beginning of a fish chorus.
Concurrent to monitoring vessel activities, we are also assessing principle biological factors that comprise the acoustic scene at each of the marine parks. So far, we have found evidence of humpback whales (Megaptera novaeangliae), dolphins (Delphinid spp.), snapping shrimp (Alpheidae spp.), and fish chorusing. We can also evaluate diel and daily presence of these species at the recording sites. Assessing diel and daily sound composition allows us to note trends in biological presence; for instance, we can note two distinct fish choruses (one in the morning and one in the evening) at the East Pimpernel and West Pimpernel sites of Solitary Islands Marine Park.
With this analysis we can provide Parks Australia with a snapshot of their marine acoustic scene and offer insight as to which species may be transiting through or near Australian Marine Parks and thus are at risk of interacting with illegally present vessels.
Daily and diel presence of humpback whale sounds, Delphinid spp. clicks, burst pulses, and whistles, fish chorusing, and snapping shrimp sounds in A) Cod Grounds Marine Park; and B) East Pimpernel and C) West Pimpernel recording sites in Solitary Islands Marine Park. A malfunction in the Cod Grounds Marine Park recording device eliminated the hours of 07:00 and 08:00 AEST from analysis on 18 July 2018.