Tiger shark predation on large ocean sunfishes (Family Molidae) – two Australian observations

Nyegaard, Marianne; Andrzejaczek, Samantha; Jenner, Curt; Jenner, Micheline‐Nicole M.

doi:10.1007/s10641-019-00926-y

Cited by 3 publications

(3 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Little is published on M. tecta due to its relatively recent description in 2017 (see Caldera et al ., 2020; Forsgren et al ., 2020; Mangel et al ., 2019; Nyegaard et al ., 2018a,b, 2019; Nyegaard & Sawai, 2018; Sawai et al ., 2018a, 2020). The actually weighed maximum M B of this species was recently reported as 52 kg (Sawai et al ., 2020), but this was an oversight.…”

Section: Discussionmentioning

confidence: 99%

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae)

Sawai¹,

Nyegaard²

2022

Journal of Fish Biology

Self Cite

View full text Add to dashboard Cite

The world's heaviest extant bony fish has long been considered the ocean sunfish Mola mola (family Molidae). However, recent taxonomic research suggests the world record specimen (2300 kg) was actually a misidentified giant sunfish M. alexandrini. Moreover, the history of taxonomic confusion in the genus Mola, combined with anecdotal size information perpetuated in both media and literature, has resulted in uncertainty in regard to species identity and actual weights of very large Mola specimens. In this study, we searched for records of molid specimens with reported body mass over 2000 kg, with a focus on the north-west and south-west Pacific. For each specimen,

show abstract

Section: Discussionmentioning

confidence: 99%

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae)

Sawai¹,

Nyegaard²

2022

Journal of Fish Biology

Self Cite

View full text Add to dashboard Cite

show abstract

“…The world's heaviest bony fish, the elusive 'giant sunfish' (Mola alexandrini), can reach an impressive weight of more than two tons [1,2]. Globally, sunfish are rarely seen by divers, but are frequent seasonal visitors to the Bali area, Indonesia [3]. Here, they seek cleaner fish interaction for removal of skin parasites, and are a highly popular target of the local SCUBA tourism industry [4].…”

Section: Introductionmentioning

confidence: 99%

“…Little is known of this seasonal sunfish phenomenon, including if the tourism is reliant on a small, local sunfish population with high site fidelity, or transient sunfish with low re-visitation rates. Understanding this is critical for assessing the potential impacts (and any need for regulation) of diver crowding, which causes disruptions to sunfish-cleaner fish interactions [3].…”

Section: Introductionmentioning

confidence: 99%

Finding Nemo’s Giant Cousin: Keypoint Matching for Robust Re-Identification of Giant Sunfish

Pedersen

Nyegaard²,

Moeslund

2023

JMSE

View full text Add to dashboard Cite

The Giant Sunfish (Mola alexandrini) has unique patterns on its body, which allow for individual identification. By continuously gathering and matching images, it is possible to monitor and track individuals across location and time. However, matching images manually is a tedious and time-consuming task. To automate the process, we propose a pipeline based on finding and matching keypoints between image pairs. We evaluate our pipeline with four different keypoint descriptors, namely ORB, SIFT, RootSIFT, and SuperPoint, and demonstrate that the number of matching keypoints between a pair of images is a strong indicator for the likelihood that they contain the same individual. The best results are obtained with RootSIFT, which achieves an mAP of 75.91% on our test dataset (TinyMola+) without training or fine-tuning any parts of the pipeline. Furthermore, we show that the pipeline generalizes to other domains, such as re-identification of seals and cows. Lastly, we discuss the impracticality of a ranking-based output for real-life tasks and propose an alternative approach by viewing re-identification as a binary classification. We show that the pipeline can be easily modified with minimal fine-tuning to provide a binary output with a precision of 98% and recall of 44% on the TinyMola+ dataset, which basically eliminates the need for time-consuming manual verification on nearly half the dataset.

show abstract

Rapid physiological colouration change is a challenge - but not a hindrance - to successful photo identification of giant sunfish (Mola alexandrini, Molidae)

Nyegaard,

Karmy,

McBride

et al. 2023

Front. Mar. Sci.

Self Cite

View full text Add to dashboard Cite

Photo ID is a common tool in ecology, but has not previously been attempted for the ocean sunfishes (Mola spp., Molidae; ‘molids’). The technique, based on body patterns, could potentially be informative for studying the seasonal occurrence of giant sunfish (Mola alexandrini) on the Bali reefs (Indonesia), where this species is an important drawcard for the local SCUBA diving tourism. However, molids are capable of rapid physiological colouration change, which may complicate the application of the method. Our study aimed to determine if photo ID is nevertheless achievable and informative. To test this, we created the citizen-science platform ‘Match My Mola’ for crowd-sourcing imagery (photos and video) of M. alexandrini in Bali, and undertook trial matching (n=1,098 submissions). The submitted imagery revealed a wide range of pattern clarity, from fish with no pattern to bold displays. Video confirmed physiological colouration change can occur in seconds in this species from low to high contrast, and cause individuals to look very different between moments. However, individual patterns appear to be stable although at least some parts can become inconspicuous during low contrast displays. Despite of this, photo ID is possible, including in some instances, where only partial patterns are visible on one image compared with another. However, true negatives (confirming two fish are not the same) can be challenging. Most identified matches were of fish photographed by different divers on the same day. Only a small number (n=9) were found with resighting durations ≥1 day (1 – 2,652 days). These matches demonstrate that at least some individuals return to the same reefs both within and between seasons, with the resighting duration of 7.2 years constituting the longest known example of molid site fidelity. Comparing body morphology between resightings of > 1 year (n=6) revealed limited indications of growth, contradicting the current understanding of rapid growth in captive molids (Mola mola), and highlighting the knowledge gap regarding growth in the wild. Continued photo ID in the Bali area could provide valuable complementary information to future growth studies using other methods as well as provide further insights into molid site fidelity.

show abstract

Tiger shark predation on large ocean sunfishes (Family Molidae) – two Australian observations

Cited by 3 publications

References 55 publications

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae)

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae)

Finding Nemo’s Giant Cousin: Keypoint Matching for Robust Re-Identification of Giant Sunfish

Rapid physiological colouration change is a challenge - but not a hindrance - to successful photo identification of giant sunfish (Mola alexandrini, Molidae)

Contact Info

Product

Resources

About