Giacomo Giorli

Presence and seasonal variation of deep diving foraging odontocetes around Kauai, Hawaii using remote autonomous acoustic recorders

Ecological acoustic recorders (EARs) were moored off the bottom in relatively deep depths (609-710 m) at five locations around the island of Kauai. Initially, the EARs had an analog-to-digital sample rate of 64 kHz with 30-s recordings every 5 min. After the second deployment the sampling rate was increased to 80 kHz in order to better record beaked whale biosonar signals. The results of the 80 kHz recording are discussed in this manuscript and are the results of three deployments over a years period (January 2010 to January 2011). Five categories of the biosonar signal detection of deep diving odontocetes were created, short-finned pilot whales, sperm whales, beaked whales, Rissos dolphins, and unknown dolphins. During any given day, at least one species of these deep diving odontocetes were detected. On many days, several species were detected. The biosonar signals of short-finned pilot whales were detected the most often with approximately 30% of all the signals, followed by beaked and sperm whales approximately 22% and 21% of all clicks, respectively. The seasonal patterns were not very strong except in the SW location with distinct peak in detection during the months of April-June 2010 period.

Unknown beaked whale echolocation signals recorded off eastern New Zealand

The echolocation signals of most beaked whale species are still unknown. In fact, out of the 22 species comprising the family Ziphiidae, only the echolocation pulses for 7 species have been clearly described. This study describes two distinct beaked whale echolocation signals recorded in the Cook Strait region using passive acoustic technology. These signals differ from previously described Ziphiid species clicks. A description of the time-frequency characteristics of the two signals is provided. Understanding the characteristics of these signals is necessary to correctly identify species from their echolocation signals and enables future monitoring of beaked whales using passive acoustics techniques.

Studying deep diving odontocetes potential prey fields' densities and size structure in Hawaii using a DIDSON imaging sonar

Deep diving odontocetesodontocetes feed in the deep ocean on mesopelagic squid and fish. The distribution of these prey are poorly known but does affect the distribution of deep diving odontocete predators. Hence, it is important to collect data on the density and composition of potential prey to identify deep sea habitats that attract deep diving odontocetes. We used a DIDSON imaging sonar to investigate the density and size structure of mesopelagic animals along the Kona coast of Hawaii, where beaked, sperm and pilot whales are regularly seen. Data were collected at multiple stations during three research cruises by lowering the sonar in the water column to sample at different depths and monitoring the mesopelagic biomass with an EK60 38 kHz echosounder. Foraging activity of whales was monitored at few stations using passive acoustic recorders and a towed array of hydrophones. We were able to count and size 7068 pelagic animals. Density and size varied in space, with higher densities and bigger animals ...

Investigating the relationship between foraging odontocetes and ocean acoustic biomass off the Kona coast of the Island of Hawaii

To understand the distribution of deep diving odontocetes, it is important to investigate the relationship between foraging whales and their prey. Tagged sperm whales have been documented to dive as deep as 1202 m. Short-finned pilot whales in Hawaii dive deeper during the day down to 600–800 m and shallower dives at night, driven possibly by the migration of organisms at night. Foraging sperm and pilot whales off the Island of Hawaii were located using a hydrophone array detecting echolocation clicks. A 500 m by 500 m active acoustics survey box was set up over two foraging sites: one during the night above foraging sperm whales and one during the day over foraging pilot whales. A four-frequency (38, 70, 120, and 200 kHz) split-beam echosounder collected acoustic data over foraging populations and non-foraging control sites of a similar bottom depth and time. The Nautical Acoustic Scattering Coefficient (NASC) or acoustic biomass (m2nmi−2) profile over the complete water column was statically compared ov...

Deep sea organisms density estimation using a Dual Frequency Identification Sonar (DIDSON)

Estimating the density of organism living in deep sea scatting layers is of key importance for understanding the biomass in the mesopelagic layers. Scientific echosounders are routinely used for this task; however, new imaging sonar technologies pose the opportunity for estimating density of organism, as well as identification at smaller scales. During the 2013 NOAA KONA Integrated Ecosystem, a Dual Frequency Identification Sonar (DIDSON) (SoundMetrics Inc.) was used to estimate the density, length of organisms in the deep sea scattering layers during nighttime and daytime along the KONA coast of the island of Hawaii. At each station, an EK60 38 kHz echosounder was used to find the depth of the deep sea scattering layers, and the DIDSON was lower into the layer (or layers if two were present) (about 500 and 600 m), and underneath the deeper layer (about 800 m). A total of 4621 organisms were counted and sized. We estimated densities ranging from 6 to 1 organism/m3. Density shows some variation between loc...

Long term passive acoustics monitoring reveals differences in deep diving Odontocetes foraging strategies

Beaked whales, sperm whales, pilot whales, and Rissos dolphins perform deep dives to feed on prey in the deep sea. They use echolocation to detect prey, and echolocation can be monitor as a proxy of their foraging activities. Ecological acoustic recorders were deployed to monitor in time the echolocation signals of pilot whales, Rissos dolphins, beaked whales, and sperm whales near Josephine Seamount (Portugal), in the Ligurian Sea (Italy), and along the Kona coast of the island of Hawaii. Data analysis was performed using two automatic detector/classification systems: Marine Mammal Monitoring on Navy Ranges (M3R), developed at the Naval Undersea Warfare Center Division in Newport, USA, and a custom MATLAB program. An operator-supervised custom MATLAB program was used to validate the classification performance, which was higher than 85% for each category. Results show that pilot whales and Rissos dolphins concentrate their feeding effort mainly during the night. The foraging activity of beaked and sperm whales is variable, and different patterns are observed at different locations. Prey behavior might play a central role in driving the foraging activity of deep divers, but to date, the reasons why such activity varies between species that might feed on similar food resources remains unknown.

Simultaneously monitoring noise and cetaceans in the Ligurian Sea

The interest in the effect of anthropogenic noise on marine life increasing rapidly, this is driven primarily by legislations in many countries that noise can be considered to be a pollutant, as for the European Marine Strategy Framework Directive. One particular area of concern has been in the interaction of military tactical sonar and the acoustically more sensitive species of cetacean, in particular the effect on beaked whales. Five ecological acoustics recorders (EAR) buoy having a sampling frequency of 80 kHz and a hydrophone with a flat sensitivity of -193.5 ± 1dB re 1 μPa up to 40 kHz have been deployed in the Northern Mediterranean at a depth of about 850 m in a canyon region known to host a population of Cuvier beaked whales (Ziphius cavirostris). The area is also located in the nearby of different shipping harbors and ferries routes. The utility of the EAR systems is that they simultaneously allow monitoring of noise levels across a wide frequency range while simultaneously allowing assessment o...

Passive acoustic monitoring of cetacean at Josephine Seamount, Portugal.

In the past years, the development of a variety of passive acoustics recorders has provided a unique way of acquiring information about marine mammal species in remote regions of the ocean. During the NATO Undersea Research Centre Sirena 10 cruise an ecological acoustic recorder (EAR) was deployed to monitor the presence of marine mammal. The EAR was deployed on May 13, 2010 at a depth of 944 m in the vicinity of Josephine seamount (37 deg; 02.087’N, 013¢a 51.733W, south west Portugal) and programed for a recording time of 40 s every 2 min. For the detection and classification of echolocation clicks we integrated the visual analysis of spectrograms with the analysis performed by an automatic detector/classification system called M3R, developed by the Naval Undersea Warfare Center Division. M3R has been successfully operated for the analysis of recording from different US Navy ranges. Cetaceans detected include beaked whales, sperm whales, pilot whales, risso’s dolphins, and dolphins. Hourly and daily dist...