Listening to Echolocation Clicks with PODs

Tregenza, Nick; Dawson, Steve; Rayment, William; Verfuß, Ursula K.

doi:10.1007/978-1-4939-3176-7_7

Cited by 14 publications

(11 citation statements)

References 59 publications

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“…Two strata were defined (visual and shallow), with higher visual survey effort in a core sub-stratum ( Figure 1). The ship could not survey in depths <20 m (Figure 1, shallow stratum); vaquitas were detected there using an array of C-POD passive acoustic detectors (Tregenza et al 2016). Abundance cannot be estimated directly using acoustic detections because we lack information on vaquita acoustic behavior and sound propagation.…”

Section: Methodsmentioning

confidence: 99%

Extinction is Imminent for Mexico's Endemic Porpoise Unless Fishery Bycatch is Eliminated

Taylor

Rojas‐Bracho

Moore

et al. 2016

CONSERVATION LETTERS

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The number of Mexico's endemic porpoise, the vaquita (Phocoena sinus), is collapsing primarily due to bycatch in illegal gillnets set for totoaba (Totoaba macdonaldi), an endangered fish whose swim bladders are exported to China. Previous research estimated that vaquitas declined from about 567 to 245 individuals between 1997 and 2008. Acoustic monitoring between 2011 and 2015 showed a decline of 34%/year. Here, we combine visual line transect and passive acoustic data collected simultaneously in a robust spatial analysis to estimate that only 59 (95% Bayesian Credible Interval [CRI] 22-145) vaquita remained as of autumn 2015, a decrease since 1997 of 92% (95% CRI 80-97%). Risk analysis suggests that if the current, temporary gillnet ban is maintained and effectively enforced, vaquitas could recover to 2008 population levels by 2050. Otherwise, the species is likely to be extinct within a decade.

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Section: Methodsmentioning

confidence: 99%

Extinction is Imminent for Mexico's Endemic Porpoise Unless Fishery Bycatch is Eliminated

Taylor

Rojas‐Bracho

Moore

et al. 2016

CONSERVATION LETTERS

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“…Results from 2008 indicated that, after testing several autonomous acoustic detectors, C‐PODs (Tregenza et al. ) had the best detection distance (approximately 200 m) and the necessary battery life to obtain the quantity of data needed to meet our objectives (Rojas‐Bracho et al. ).…”

Section: Methodsmentioning

confidence: 99%

“…; Roberts & Read ; Tregenza et al. ). This algorithm (KERNO in C‐POD software version 2.044) looks for coherent sequences of more or less regularly spaced clicks (i.e., click trains).…”

Section: Methodsmentioning

confidence: 99%

Passive acoustic monitoring of the decline of Mexico's critically endangered vaquita

Jaramillo-Legorreta

Cárdenas-Hinojosa

Nieto-García

et al. 2016

Conservation Biology

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The vaquita (Phocoena sinus) is the world's most endangered marine mammal with approximately 245 individuals remaining in 2008. This species of porpoise is endemic to the northern Gulf of California, Mexico, and historically the population has declined because of unsustainable bycatch in gillnets. An illegal gillnet fishery for an endangered fish, the totoaba (Totoaba macdonaldi), has recently resurged throughout the vaquita's range. The secretive but lucrative wildlife trade with China for totoaba swim bladders has probably increased vaquita bycatch mortality by an unknown amount. Precise population monitoring by visual surveys is difficult because vaquitas are inherently hard to see and have now become so rare that sighting rates are very low. However, their echolocation clicks can be identified readily on specialized acoustic detectors. Acoustic detections on an array of 46 moored detectors indicated vaquita acoustic activity declined by 80% between 2011 and 2015 in the central part of the species' range. Statistical models estimated an annual rate of decline of 34% (95% Bayesian credible interval -48% to -21%). Based on results from 2011 to 2014, the government of Mexico enacted and is enforcing an emergency 2-year ban on gillnets throughout the species' range to prevent extinction, at a cost of US$74 million to compensate fishers. Developing precise acoustic monitoring methods proved critical to exposing the severity of vaquitas' decline and emphasizes the need for continual monitoring to effectively manage critically endangered species.

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“…The C‐POD was used as the passive acoustic data collection instrument. This device contains an omni‐directional hydrophone that records the timing of zero‐crossings (accuracy to 200 ns) and the peak amplitude between zero crossings (Tregenza, Dawson, Rayment, & Verfuss, 2016). These data are then used to identify the narrow‐band high‐frequency (NBHF) clicks of harbor porpoises (Au, Kastelein, Rippe, & Schooneman, 1999; Macaulay, Malinka, Gillespie, & Madsen, 2020; Villadsgaard, Wahlberg, & Tougaard, 2007).…”

Section: Methodsmentioning

confidence: 99%

An increase in detection rates of the critically endangered Baltic Proper harbor porpoise in Swedish waters in recent years

Owen

Sköld

Carlström

2021

Conservat Sci and Prac

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The Baltic Proper harbor porpoise (Phocoena phocoena) is currently listed as critically endangered (CR), with the Static Acoustic Monitoring of the Baltic Sea Harbor Porpoise (SAMBAH) project concluding that only $500 individuals remain. This population has a distribution that spans the waters of nine countries, making regular abundance estimates and management action challenging. Given the continued decline of other depleted porpoises, namely the vaquita (Phocoena sinus), the question is often raised about whether management action would even have a positive impact, or whether it is too late for population recovery. When abundance estimates are sparse over time, monitoring programs at key sites are likely to serve as the best indication of population trends, and may provide an early indication of changes at the population level. We compared passive acoustic monitoring data from 12 stations that were utilized both in the SAMBAH project (2011)(2012)(2013) and as a part of the Swedish National Monitoring Program (2017-2020) to determine trends in detection rates. There was a 29% increase in mean daily detection rate during May-October (over the breeding season) between the two study periods. At the three stations with the highest number of detections, log linear regression revealed a yearly increase of 2.4% between 2011 and 2019 (À4.4-9.6, 95% CI). This may be indicative of the beginnings of population recovery, or simply an indication that the decline has stalled. The rate of increase is still well below what is likely to be possible for porpoise populations, and unlikely to buffer against any potential increase in pressures in the future. We therefore call for urgent management action to remove threats and protect this CR population, the only resident cetacean in the Baltic region, in order to give it the best chance of recovery.

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Listening to Echolocation Clicks with PODs

Cited by 14 publications

References 59 publications

Extinction is Imminent for Mexico's Endemic Porpoise Unless Fishery Bycatch is Eliminated

Extinction is Imminent for Mexico's Endemic Porpoise Unless Fishery Bycatch is Eliminated

Passive acoustic monitoring of the decline of Mexico's critically endangered vaquita

An increase in detection rates of the critically endangered Baltic Proper harbor porpoise in Swedish waters in recent years

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