Clicks of dwarf sperm whales (Kogia sima)

Captive acoustic recordings were approved by the Institutional Animal Care and Use Committee of the University of South Florida. Research in The Bahamas was conducted under the Department of Fisheries research permit 12A and was supported by a Royal Society University Research Fellowship to VMJ. Recordings in Guam were made under NMFS permit 15240 and were supported with funding provided by the NOAA/NMFS Pacific Islands Fisheries Science Center, and the U.S. Navy Pacific Fleet.The two species of the genus Kogia are widely distributed throughout the world's temperate and tropical oceans, but because they are small and highly cryptic, they are difficult to monitor. The acoustic signals of K. breviceps have been described previously, but the signals of K. sima have remained unknown. Here we present three recordings of K. sima, two from free-ranging animals and one from a captive setting, representing both the Atlantic Ocean and Pacific Ocean. The acoustic signals of K. sima are very similar to the signals of K. breviceps and other species that have narrow-band, high-frequency (NBHF) clicks. Free-ranging K. sima produce “usual” clicks that have mean peak and centroid frequencies of 127–129 kHz, mean −3 dB bandwidth of 10 kHz, mean −10 dB bandwidth of 16–17 kHz, and mean interclick interval of 110–164 ms. Although K. sima clicks cannot yet be distinguished from those of K. breviceps or other NBHF clicking species, our detailed description of this species' signals reveals the similarities between the two Kogia species, and thus allows for passive acoustic monitoring of the genus Kogia in regions where other NBHF species are not present.PostprintPeer reviewe

Deep-Diving Cetaceans of the Gulf of Mexico : : Acoustic Ecology and Response to Natural and Anthropogenic Forces Including the Deepwater Horizon Oil Spill

Characterization of the spatiotemporal patterns of marine mammal populations is challenging yet critical for understanding their role in the ecosystem and how they are affected by ecological disturbance, such as anthropogenic activity. Gathering information about deep-diving cetaceans is particularly difficult because they spend so much of their lives well below the ocean's surface, however they can be detected using passive acoustic monitoring. The Gulf of Mexico is home to at least six species of deep-diving cetaceans, and we recorded signals from Ziphius cavirostris, Mesoplodon europaeus, M. densirostris, Physeter macrocephalus and Kogia spp., as well as an unknown beaked whale-like signal. Using seafloor High Frequency Acoustic Recording Packages (HARPs) we monitored nearly-continuously at three deep- water sites (>900m depth) using a 200 kHz sampling rate, from May 2010 until February 2012, accumulating more than 1350 cumulative days of data. Here I describe the species present, their detection trends over time and their relationships with the environment, including the Deepwater Horizon oil spill. This major environmental event took place in the northern Gulf of Mexico for roughly three months in the summer of 2010, and released approximately 210 billion gallons of oil and unmeasured amounts of natural gas mixed with chemical dispersants into the deep water along the continental slope. The number of detections for each species fluctuated across sites on diel and seasonal time scales. Beaked whales were detected at a remarkably high rate at one site. Sperm whales were detected almost daily at another site. Kogia spp., which are very difficult to monitor visually, were easily detected acoustically and were present at all three sites. I used mathematical models to relate acoustic detections of the different species to their environment. The models included both natural and anthropogenic factors, with data collected both in situ and remotely. Most models include mean sea surface temperature, indicating the importance of seasonal variations and the resulting ecological fluctuations. The results vary by species and location, and help us understand the ecology of these rare species as well as the potential impact of the oil spill on the regio

Click detection rate variability of central North Pacific sperm whales from passive acoustic towed arrays

Passive acoustic monitoring (PAM) is an optimal method for detecting and monitoring cetaceans as they frequently produce sound while underwater. Cue counting, counting acoustic cues of deep-diving cetaceans instead of animals, is an alternative method for density estimation, but requires an average cue production rate to convert cue density to animal density. Limited information about click rates exists for sperm whales in the central North Pacific Ocean. In the absence of acoustic tag data, we used towed hydrophone array data to calculate the first sperm whale click rates from this region and examined their variability based on click type, location, distance of whales from the array, and group size estimated by visual observers. Our findings show click type to be the most important variable, with groups that include codas yielding the highest click rates. We also found a positive relationship between group size and click detection rates that may be useful for acoustic predictions of group size in future studies. Echolocation clicks detected using PAM methods are often the only indicator of deep-diving cetacean presence. Understanding the factors affecting their click rates provides important information for acoustic density estimation.</p

Assessing Seasonality and Density From Passive Acoustic Monitoring of Signals Presumed to be From Pygmy and Dwarf Sperm Whales in the Gulf of Mexico

Pygmy sperm whales (Kogia breviceps) and dwarf sperm whales (Kogia sima) are deep diving cetaceans that commonly strand along the coast of the southeast US, but that are difficult to study visually at sea because of their elusive behavior. Conventional visual surveys are thought to significantly underestimate the presence of Kogia and they have proven difficult to approach for tracking and tagging. An approach is presented for density estimation of signals presumed to be from Kogia spp. based on passive acoustic monitoring data collected at sites in the Gulf of Mexico (GOM) from the period following the Deepwater Horizon oil spill (2010-2013). Both species of Kogia are known to inhabit the GOM, although it is not possible to acoustically separate the two based on available knowledge of their echolocation clicks. An increasing interannual density trend is suggested for animals near the primary zone of impact of the oil spill, and to the southeast of the spill. Densities were estimated based on both counting individual echolocation clicks and counting the presence of groups of animals during one-min time windows. Densities derived from acoustic monitoring at three sites are all substantially higher (4–16 animals/1000 km2) than those that have been derived for Kogia from line transect visual surveys in the same region (0.5 animals/1000 km2). The most likely explanation for the observed discrepancy is that the visual surveys are underestimating Kogia spp. density, due to the assumption of perfect detectability on the survey trackline. We present an alternative approach for density estimation, one that derives echolocation and behavioral parameters based on comparison of modeled and observed sound received levels at sites of varying depth

Passive Acoustic Monitoring of Beaked Whale Densities in the Gulf of Mexico

Beaked whales are deep diving elusive animals, difficult to census with conventional visual surveys. Methods are presented for the density estimation of beaked whales, using passive acoustic monitoring data collected at sites in the Gulf of Mexico (GOM) from the period during and following the Deepwater Horizon oil spill (2010-2013). Beaked whale species detected include: Gervais\u27 (Mesoplodon europaeus), Cuvier\u27s (Ziphius cavirostris), Blainville\u27s (Mesoplodon densirostris) and an unknown species of Mesoplodon sp. (designated as Beaked Whale Gulf - BWG). For Gervais\u27 and Cuvier\u27s beaked whales, we estimated weekly animal density using two methods, one based on the number of echolocation clicks, and another based on the detection of animal groups during 5 min time-bins. Density estimates derived from these two methods were in good general agreement. At two sites in the western GOM, Gervais\u27 beaked whales were present throughout the monitoring period, but Cuvier\u27s beaked whales were present only seasonally, with periods of low density during the summer and higher density in the winter. At an eastern GOM site, both Gervais\u27 and Cuvier\u27s beaked whales had a high density throughout the monitoring period

Species-specific beaked whale echolocation signals.

Beaked whale echolocation signals are mostly frequency-modulated (FM) upsweep pulses and appear to be species specific. Evolutionary processes of niche separation may have driven differentiation of beaked whale signals used for spatial orientation and foraging. FM pulses of eight species of beaked whales were identified, as well as five distinct pulse types of unknown species, but presumed to be from beaked whales. Current evidence suggests these five distinct but unidentified FM pulse types are also species-specific and are each produced by a separate species. There may be a relationship between adult body length and center frequency with smaller whales producing higher frequency signals. This could be due to anatomical and physiological restraints or it could be an evolutionary adaption for detection of smaller prey for smaller whales with higher resolution using higher frequencies. The disadvantage of higher frequencies is a shorter detection range. Whales echolocating with the highest frequencies, or broadband, likely lower source level signals also use a higher repetition rate, which might compensate for the shorter detection range. Habitat modeling with acoustic detections should give further insights into how niches and prey may have shaped species-specific FM pulse types

State of the California Current, Spring 2008-2009: cold conditions drive regional differences in coastal production

This report describes the state of the California Surrent system (CCS) between the springs of 2008 and 2009 based on observations taken along the west coast of North America. the dominant forcing on the CCS during this time period were La Nina type conditions that prevailed from the summer of 2007 through early 2009, transitioning to neutral El Nino-Southern Oscillation conditions in the spring of 2009. The Pacific Decadal Oscillation index was negative during this time period and its values had not returned to normal by the spring of 2009. The general effects on the California Current system were stronger than normal southward winds and upselling as well as generally colder that normal SST and shallow nitraclines; however, there were regional differences. Off Baja California sea surface temperatures did not respond to the La Nina conditions; however, concentrations of chorophyll a (Chl a) were significantly above normal, probably due to the anomolously high upwelling off Baja during most of the year. Off southern California there was no clear evidence of increased promary or secondary production, despite observations that previous La Nina conditions affected mixed layer depth, temperatures, nutrients, and nitracline depths. In both central and northern California and Oregon, stronger than normal upwelling increased primary production and prevented potential spawning of sardine north of San Francisco. In central California the midwater fish community resembled that of recent cool years, and cover by kelp was much reduced along the coast. Off Oregon there was evidence of increased abundance of boreal copepods, although the neritic boreal species did not appear to extend as far south as central California. Current predictions are for cooler conditions to change to El Nino conditions by the end of 2009; these are expected to last through the Northern Hemisphere winter of 2009-10

Understanding vessel noise across a network of marine protected areas.

Protected areas are typically managed as a network of sites exposed to varying anthropogenic conditions. Managing these networks benefits from monitoring of conditions across sites to help prioritize coordinated efforts. Monitoring marine vessel activity and related underwater radiated noise impacts across a network of protected areas, like the U.S. National Marine Sanctuary system, helps managers ensure the quality of habitats used by a wide range of marine species. Here, we use underwater acoustic detections of vessels to quantify different characteristics of vessel noise at 25 locations within eight marine sanctuaries including the Hawaiian Archipelago and the U.S. east and west coasts. Vessel noise metrics, including temporal presence and sound levels, were paired with Automatic Identification System (AIS) vessel tracking data to derive a suite of robust vessel noise indicators for use across the network of marine protected areas. Network-wide comparisons revealed a spectrum of vessel noise conditions that closely matched AIS vessel traffic composition. Shifts in vessel noise were correlated with the decrease in vessel activity early in the COVID-19 pandemic, and vessel speed reduction management initiatives. Improving our understanding of vessel noise conditions in these protected areas can help direct opportunities for reducing vessel noise, such as establishing and maintaining noise-free periods, enhancing port efficiency, engaging with regional and international vessel quieting initiatives, and leveraging co-benefits of management actions for reducing ocean noise