Photo identification is an essential method to identify cetaceans, by using natural marks over their body, and allows experts to acquire straightforward information on these animals. The importance of cetaceans lies in te fact that they play a crucial role in maintaining the healthiness of marine ecosystems, however they are exposed to several anthropogenic stressors, under which they could collapse with extreme consequences on the marine ecosystem functioning. Hence, obtaining new knowledge on their status is extremely urgent for the marine biodiversity conservation. The smart use of technology to automate the individual recognition can speed up the photo identification process, opening the door to large-scale studies that are manually unfeasible. We performed a systematic review on systems based on machine learning and statistical methods for cetacean photo identification, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. This review highlights that interest has been increasing in recent years and several intelligent systems have been presented. However, there are still some open questions, and further efforts to develop more effective automated systems for cetacean photo identification are recommended.

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Machine Learning and Image Processing Methods for Cetacean Photo Identification: A Systematic Review

Analysis of stranding data to support estimates of mortality and serious injury in common bottlenose dolphin (Tursiops truncatus truncatus) stock assessments for the Atlantic Ocean and Gulf of Mexico

Salinity and Water Temperature as Predictors of Bottlenose Dolphin (Tursiops truncatus) Encounter Rates in Upper Galveston Bay, Texas

Simple Summary The COVID-19 pandemic caused a decrease in human activity in many areas across the globe due to stay-at-home orders and the cessation of non-essential work activities. This dramatic decrease in human activity became known as an anthropause which created an opportunity for scientists to study the effects of decreased anthropogenic (human-made) noise. Bermuda did not host cruise ships or allow non-essential activities from early in the pandemic through to 20 May 2021. We presented three anthropogenic sound types (cruise ship, personal watercraft, and Navy low-frequency active sonar) to dolphins housed at Dolphin Quest Bermuda in 2018 and again during the COVID-19-related anthropause in 2021. We played each dolphin three anthropogenic sound types via an underwater speaker. The dolphins’ behavioral and acoustic responses were recorded. We found that decreased anthropogenic noise levels around Bermuda were associated with altered attention in the dolphins. The dolphins increased look durations and changed vocal response behaviors to playbacks during the anthropause and the dolphins responded to cruise ship playbacks up to fourfold more in 2021. These changes in response to this sound type may have implications on how dolphins habituate and dishabituate to sounds ever-present in their environment. Abstract The effects of anthropogenic noise continue to threaten marine fauna, yet the impacts of human-produced sound on the broad aspects of cognition in marine mammals remain relatively understudied. The shutdown of non-essential activities due to the COVID-19-related anthropause created an opportunity to determine if reducing levels of oceanic anthropogenic noise on cetaceans affected processes of sensitization and habituation for common human-made sounds in an experimental setting. Dolphins at Dolphin Quest Bermuda were presented with three noises related to human activities (cruise ship, personal watercraft, and Navy low-frequency active sonar) both in 2018 and again during the anthropause in 2021 via an underwater speaker. We found that decreased anthropogenic noise levels altered dolphin responses to noise playbacks. The dolphins spent significantly more time looking towards the playback source, but less time producing burst pulse and echolocation bouts in 2021. The dolphins looked towards the cruise ship sound source significantly more in 2021 than 2018. These data highlight that different sounds may incur different habituation and sensitization profiles and suggest that pauses in anthropogenic noise production may affect future responses to noise stimuli as dolphins dishabituate to sounds over time.

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A Quieter Ocean: Experimentally Derived Differences in Attentive Responses of Tursiops truncatus to Anthropogenic Noise Playbacks before and during the COVID-19-Related Anthropause

Exposure of common bottlenose dolphins (Tursiops truncatus) to brevetoxins (PbTx) produced by Karenia brevis blooms frequently results in large-scale mortality events, but data on relationships between bloom severity and corresponding PbTx concentrations in exposed live animals are lacking. Here we present results of PbTx analysis of samples from live, free-ranging dolphins (n=253) from Sarasota Bay, Florida during 2000-2018, and investigate the relationship between PbTx concentrations detected and corresponding K. brevis cell abundances associated with each individual. 28% of dolphins were associated with elevated K. brevis abundances (>10,000 cells/L), and 41% (n=104) of dolphins were PbTx-positive. The proportion of PbTx-positive animals was significantly greater in animals exposed to elevated cell abundances vs. those exposed to background cell abundances (<10,000 cells/L), with 60% and 34% testing positive, respectively. PbTx was detected most frequently in feces (57%), followed by gastric (35%), urine (32%), and blood (7%). PbTx concentrations were highest in feces (2-231 ng/g; mean 46), followed by urine (0.8-90 ng/g; mean 7.2), gastric (0.8-61 ng/g; mean 12), and blood (0.3-5 ng/g; mean 1.3). Analyses of K. brevis cell abundance as an index of exposure vs. corresponding PbTx concentration found no statistically significant relationship for feces, gastric, urine, or blood samples. PbTx concentrations typically did not scale with corresponding indices of exposure. Our results indicate that K. brevis cell abundance alone is a poor predictor of brevetoxin accumulation in bottlenose dolphins, and alternative biomarkers should be investigated as more appropriate methods for determining the severity of health impacts due to red tides.

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Utility of Red Tide (Karenia brevis) Monitoring Data as a Predictive Tool to Estimate Brevetoxin Accumulation in Live, Free-Ranging Marine Mammals

Recommended Citation Ronje, E., H. Whitehead, K. Barry, S. Piwetz, J. Struve, V. Lecours, L. Garrison, R. S. Wells and K. D. Mullin. 2020. Abundance and Occurrence of Common Bottlenose Dolphins (Tursiops truncatus) in Three Estuaries of the Northwestern Gulf of Mexico. Gulf and Caribbean Research 31 (1): 18-34. Retrieved from https://aquila.usm.edu/gcr/vol31/iss1/9 DOI: https://doi.org/10.18785/gcr.3101.09

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Abundance and Occurrence of Common Bottlenose Dolphins (Tursiops truncatus) in Three Estuaries of the Northwestern Gulf of Mexico

Dolphin teeth contain enamel, dentin, and cementum. In dentin, growth layer groups (GLGs), deposited at incremental rates (e.g., annually), are used for aging. Major, minor, and trace elements are incorporated within teeth; their distribution within teeth varies, reflecting tooth function and temporal changes in an individual’s exposure. This study used a scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) to determine the distribution of major (e.g., Ca, P), minor (e.g., Cl, Mg, Na), and trace elements (e.g., Cd, Hg, Pb, Zn) in teeth from 12 bottlenose dolphins (Tursiops truncatus). The objective was to compare elemental distributions between enamel and dentin and across GLGs. Across all dolphins and point analyses, the following elements were detected in descending weight percentage (wt %; mean ± SE): O (40.8 ± 0.236), Ca (24.3 ± 0.182), C (14.3 ± 0.409), P (14.0 ± 0.095), Al (4.28 ± 0.295), Mg (1.89 ± 0.047), Na (0.666 ± 0.008), Cl (0.083 ± 0.003). Chlorine and Mg differed between enamel and dentin; Mg increased from the enamel towards the dentin while Cl decreased. The wt % of elements did not vary significantly across the approximate location of the GLGs. Except for Al, which may be due to backscatter from the SEM stub, we did not detect trace elements. Other trace elements, if present, are below the detection limit. Technologies with lower detection limits (e.g., laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)) would be required to confirm the presence and distribution of trace elements in bottlenose dolphin teeth.

Exploring the Use of SEM-EDS Analysis to Measure the Distribution of Major, Minor, and Trace Elements in Bottlenose Dolphin (Tursiops truncatus) Teeth.

Association between red tide exposure and detection of corresponding neurotoxins in bottlenose dolphins from Texas waters during 2007-2017.

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Sarah Piwetz

Papers

Abundance and Occurrence of Common Bottlenose Dolphins (Tursiops truncatus) in Three Estuaries of the Northwestern Gulf of Mexico

Exploring the Use of SEM-EDS Analysis to Measure the Distribution of Major, Minor, and Trace Elements in Bottlenose Dolphin (Tursiops truncatus) Teeth.

Association between red tide exposure and detection of corresponding neurotoxins in bottlenose dolphins from Texas waters during 2007-2017.

Intraspecific Aggression Towards Common Bottlenose Dolphin Calves, Northern Gulf of Mexico