Little information exists on the current status of Southern Hemisphere sei whales (Balaenoptera borealis). We assessed their distribution and abundance along the west coast of the Falkland Islands ...(southwest Atlantic) during February and March 2018, using line transect and nonsystematic surveys. Abundance estimates were generated for a single survey stratum using design‐ and model‐based approaches. Sightings of sei whales and unidentified baleen whales (most, if not all, likely to be sei whales) occurred from the coast to the 100 m depth isobath that marked the offshore boundary of the stratum. The modeled distribution predicted highest whale densities in King George Bay and in the waters between Weddell Island and the Passage Islands. Sei whale abundance was estimated as 716 animals (CV = 0.22; 95% CI 448, 1,144; density = 0.20 whales/km2) using the design‐based approach, and 707 animals (CV = 0.11; 95% CI 566, 877; density = 0.20 whales/km2) using the model‐based approach. For sei whales and unidentified baleen whales combined, the equivalent estimates were 916 animals (CV = 0.19; 95% CI 606, 1,384; density = 0.26 whales/km2) and 895 animals (CV = 0.074; 95% CI 777, 1,032; density = 0.25 whales/km2). The data indicate that the Falkland Islands inner shelf region may support globally important seasonal feeding aggregations of sei whales, and potentially qualify as a Key Biodiversity Area.
Abstract
The Burmeister’s porpoise
Phocoena spinipinnis
is a small, poorly-studied, and Near Threatened cetacean species, with a limited geographic range comprising the Pacific and Atlantic coastal ...temperate waters of five South American countries. Here we describe a stranding of a freshly-dead adult male Burmeister’s porpoise that was discovered opportunistically on the eastern coast of the Falkland Islands (51°40.9′S, 57°43.2′W) on 29 June 2019. Unfortunately the carcass was removed by an unknown source prior to any scientific sampling, but the morphological features revealed in photographs taken of the dead animal were sufficient to verify the species identification. This is the first known record of Burmeister’s porpoise in the Falklands, confirming a sixth range state for the species and expanding its known distribution range eastwards from the previous nearest documented occurrence in Tierra del Fuego by at least 600 km across the Patagonian Shelf.
Despite their enormous size, whales make their living as voracious predators. To catch their much smaller, more maneuverable prey, they have developed several unique locomotor strategies that require ...high energetic input, high mechanical power output and a surprising degree of agility. To better understand how body size affects maneuverability at the largest scale, we used bio-logging data, aerial photogrammetry and a high-throughput approach to quantify the maneuvering performance of seven species of free-swimming baleen whale. We found that as body size increases, absolute maneuvering performance decreases: larger whales use lower accelerations and perform slower pitch-changes, rolls and turns than smaller species. We also found that baleen whales exhibit positive allometry of maneuvering performance: relative to their body size, larger whales use higher accelerations, and perform faster pitch-changes, rolls and certain types of turns than smaller species. However, not all maneuvers were impacted by body size in the same way, and we found that larger whales behaviorally adjust for their decreased agility by using turns that they can perform more effectively. The positive allometry of maneuvering performance suggests that large whales have compensated for their increased body size by evolving more effective control surfaces and by preferentially selecting maneuvers that play to their strengths.
The false killer whale (
Pseudorca crassidens
) is primarily distributed across tropical, subtropical and warm temperate waters, with few records originating above 50° latitude in each hemisphere. In ...February 2013, a mass stranding of 22 false killer whales occurred on the east coast of the Falkland Islands (Malvinas; 51.83°S, 58.24°W). Of the 20 sexed animals, 11 were male and 9 were female. Total body lengths ranged from 396 to 581 cm, and the stranded animals likely consisted entirely of mature adults. There were no significant differences between the sexes in proportional body measurements, with the exception of proportional dorsal fin height which was significantly higher in males. Tooth counts ranged from 14 to 18 in the upper jaws, and from 14 to 20 in the lower jaws. Four stomachs were investigated, of which three were empty and one contained a single Onychoteuthidae squid (
Onykia ingens)
beak. Mitochondrial control region sequences from the stranded animals indicated greater genetic connectivity between the south Pacific and south Atlantic than between the south and north Atlantic ocean basins. Given the absence of full necropsies, the underlying reasons for the stranding could not be ascertained. This mass stranding represents the first confirmed record of false killer whales in the Falkland Islands, and provides new information on the species in the southernmost part of its distributional range.
Fin whales
were hunted unsustainably across the globe in the 19th and 20th centuries, leading to vast reductions in population size. Whaling catch records indicate the importance of the Southern ...Ocean for this species; approximately 730,000 fin whales were harvested during the 20th century in the Southern Hemisphere (SH) alone, 94% of which were at high latitudes. Genetic samples from contemporary whales can provide a window to past population size changes, but the challenges of sampling in remote Antarctic waters limit the availability of data. Here, we take advantage of historical samples in the form of bones and baleen available from ex-whaling stations and museums to assess the pre-whaling diversity of this once abundant species. We sequenced 27 historical mitogenomes and 50 historical mitochondrial control region sequences of fin whales to gain insight into the population structure and genetic diversity of Southern Hemisphere fin whales (SHFWs) before and after the whaling. Our data, both independently and when combined with mitogenomes from the literature, suggest SHFWs are highly diverse and may represent a single panmictic population that is genetically differentiated from Northern Hemisphere populations. These are the first historic mitogenomes available for SHFWs, providing a unique time series of genetic data for this species.
BackgroundThe status of the dusky dolphin (Lagenorhynchus obscurus) around the Falkland Islands (south-west Atlantic) has been long debated, since most records published to date lack supporting ...information. There is also considerable scope for confusion with the sympatric Peale’s dolphin (L. australis), which has a similar external appearance.ResultsA literature review confirmed one previously-published record as dusky dolphin; a skull that apparently originated from the Falklands in 1955. Four new photographically-supported records of dusky dolphin are described, comprising three sightings and one live stranding. Two sightings consisted of the same dusky dolphin individual in a mixed-species association with Peale’s dolphins in coastal waters. An additional sighting established their use of deep, offshore waters around the Falklands.ConclusionThe dusky dolphin is a confirmed component of the Falkland Islands cetacean community, but appears to be relatively uncommon. The first documented occurrences of an association between dusky and Peale’s dolphins emphasises the need for vigilance when identifying dolphins during cetacean surveys in the wider South American region.
Large-scale offshore renewable energy infrastructure construction in Scottish waters is anticipated in coming decades. An approach being pursued, with a view to preventing short-range marine mammal ...injury, is the introduction of additional noise sources to intentionally disturb and displace animals from renewable sites over the construction period. To date, no full and transparent consideration has been given to the long-term cost benefits of noise reduction compared with noise-inducing mitigation techniques. It has yet to be determined if the introduction of additional noise is consistent with the objectives of the EU Habitats Directive and the Marine Strategy Framework Directive.
Abstract
Researchers can investigate many aspects of animal ecology through noninvasive photo–identification. Photo–identification is becoming more efficient as matching individuals between photos is ...increasingly automated. However, the convolutional neural network models that have facilitated this change need many training images to generalize well. As a result, they have often been developed for individual species that meet this threshold. These single‐species methods might underperform, as they ignore potential similarities in identifying characteristics and the photo–identification process among species.
In this paper, we introduce a multi‐species photo–identification model based on a state‐of‐the‐art method in human facial recognition, the ArcFace classification head. Our model uses two such heads to jointly classify species and identities, allowing species to share information and parameters within the network. As a demonstration, we trained this model with 50,796 images from 39 catalogues of 24 cetacean species, evaluating its predictive performance on 21,192 test images from the same catalogues. We further evaluated its predictive performance with two external catalogues entirely composed of identities that the model did not see during training.
The model achieved a mean average precision (MAP) of 0.869 on the test set. Of these, 10 catalogues representing seven species achieved a MAP score over 0.95. For some species, there was notable variation in performance among catalogues, largely explained by variation in photo quality. Finally, the model appeared to generalize well, with the two external catalogues scoring similarly to their species' counterparts in the larger test set.
From our cetacean application, we provide a list of recommendations for potential users of this model, focusing on those with cetacean photo–identification catalogues. For example, users with high quality images of animals identified by dorsal nicks and notches should expect near optimal performance. Users can expect decreasing performance for catalogues with higher proportions of indistinct individuals or poor quality photos. Finally, we note that this model is currently freely available as code in a GitHub repository and as a graphical user interface, with additional functionality for collaborative data management, via Happywhale.com.
The global range of Risso's dolphin Grampus griseus is not well known, and there has been confusion in the literature as to whether the species has a broad, circumglobal range or only occurs along ...continental margins.
To clarify the species' distribution and habitat preferences, we compiled and reviewed all available (published and unpublished) records of sightings and captures of this species for the past 62 years (1950–2012, n = 8068 records). Stranding records were not included.
The results showed that the species has a range that extends across ocean basins and spans between at least 64°N and 46°S, and is apparently absent from high‐latitude polar waters. Although Risso's dolphins occur in all habitats from coastal to oceanic, they show a strong range‐wide preference for mid‐temperate waters of the continental shelf and slope between 30° and 45° latitude.
Although a number of misconceptions about the distributional ecology of Risso's dolphin have existed, this analysis showed that it is a widespread species. It strongly favours temperate waters and prefers continental shelf and slope waters to oceanic depths. These habitat preferences appear to hold throughout much or all of the species' range.
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