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For two decades, the U.S. hasn't imported wild-caught whales or dolphins. Now the Georgia Aquarium wants to bring in 18 belugas from Russia.
Common Dolphin (Delphinus delphis) Bycatch in New Zealand Commercial Trawl Fisheries.
PLoS One. 2013;8(5):e64438
Authors: Thompson FN, Abraham ER, Berkenbusch K
Abstract Marine mammals are regularly reported as bycatch in commercial and artisanal fisheries, but data are often insufficient to allow assessment of these incidental mortalities. Observer coverage of the mackerel trawl fishery in New Zealand waters between 1995 and 2011 allowed evaluation of common dolphin Delphinus delphis bycatch on the North Island west coast, where this species is the most frequently caught cetacean. Observer data were used to develop a statistical model to estimate total captures and explore covariates related to captures. A two-stage Bayesian hurdle model was used, with a logistic generalised linear model predicting whether any common dolphin captures occurred on a given tow of the net, and a zero-truncated Poisson distribution to estimate the number of dolphin captures, given that there was a capture event. Over the 16-year study period, there were 119 common dolphin captures reported on 4299 observed tows. Capture events frequently involved more than one individual, with a maximum of nine common dolphin observed caught in a single tow. There was a peak of 141 estimated common dolphin captures (95% c.i.: 56 to 276; 6.27 captures per 100 tows) in 2002-03, following the marked expansion in annual effort in this fishery to over 2000 tows. Subsequently, the number of captures fluctuated although fishing effort remained relatively high. Of the observed capture events, 60% were during trawls where the top of the net (headline) was <40 m below the surface, and the model determined that this covariate best explained common dolphin captures. Increasing headline depth by 21 m would halve the probability of a dolphin capture event on a tow. While lack of abundance data prevents assessment of the impact of these mortalities on the local common dolphin population, a clear recommendation from this study is the increasing of headline depth to reduce common dolphin captures.
PMID: 23717614 [PubMed - as supplied by publisher]
Complexity index and proportional variability to study dolphin whistles.
J Acoust Soc Am. 2013 May;133(5):3312
Authors: Bazúa Durán C, Sarmiento Ponce EJ, González Leal BP, Rodríguez Bohorquez C
Abstract Dolphin whistles are emitted especially during social interactions and feeding activities involving group cohesion, individual recognition, and recruitment. This paper presents a new methodology to describe and compare the whistle repertoire of dolphins. It consists on first extracting the whistle contour using Matlab BELUGA, then classifying whistles into whistle types using Matlab ArtWARP, next classifying whistle types into four general categories (high complexity, low complexity, linear long, and linear short), and finally computing a complexity index and a proportional variability of the whistle repertoire. The method was tested with whistles from captive and wild bottlenose dolphins, Tursiops truncatus, and from wild Guyana dolphins, Sotalia guianensis. Results obtained showed that this very simple method is useful to describe the whistle repertoire and to compare it according to the general behavioral state of dolphins, and between species. It is necessary to implement new methodologies like this one to better understand how dolphins are using whistles, since acoustic communication is the most important sense in dolphin species. This is specially important in areas where dolphins are exposed to humans, and where underwater visibility is limited, like Laguna de Términos, a Marine Protected Area in Mexico. [Work supported by PAPIIT-UNAM.].
PMID: 23654849 [PubMed - as supplied by publisher]
Rod monochromacy and the coevolution of cetacean retinal opsins.
PLoS Genet. 2013 Apr;9(4):e1003432
Authors: Meredith RW, Gatesy J, Emerling CA, York VM, Springer MS
Abstract Cetaceans have a long history of commitment to a fully aquatic lifestyle that extends back to the Eocene. Extant species have evolved a spectacular array of adaptations in conjunction with their deployment into a diverse array of aquatic habitats. Sensory systems are among those that have experienced radical transformations in the evolutionary history of this clade. In the case of vision, previous studies have demonstrated important changes in the genes encoding rod opsin (RH1), short-wavelength sensitive opsin 1 (SWS1), and long-wavelength sensitive opsin (LWS) in selected cetaceans, but have not examined the full complement of opsin genes across the complete range of cetacean families. Here, we report protein-coding sequences for RH1 and both color opsin genes (SWS1, LWS) from representatives of all extant cetacean families. We examine competing hypotheses pertaining to the timing of blue shifts in RH1 relative to SWS1 inactivation in the early history of Cetacea, and we test the hypothesis that some cetaceans are rod monochomats. Molecular evolutionary analyses contradict the "coastal" hypothesis, wherein SWS1 was pseudogenized in the common ancestor of Cetacea, and instead suggest that RH1 was blue-shifted in the common ancestor of Cetacea before SWS1 was independently knocked out in baleen whales (Mysticeti) and in toothed whales (Odontoceti). Further, molecular evidence implies that LWS was inactivated convergently on at least five occasions in Cetacea: (1) Balaenidae (bowhead and right whales), (2) Balaenopteroidea (rorquals plus gray whale), (3) Mesoplodon bidens (Sowerby's beaked whale), (4) Physeter macrocephalus (giant sperm whale), and (5) Kogia breviceps (pygmy sperm whale). All of these cetaceans are known to dive to depths of at least 100 m where the underwater light field is dim and dominated by blue light. The knockout of both SWS1 and LWS in multiple cetacean lineages renders these taxa rod monochromats, a condition previously unknown among mammalian species.
PMID: 23637615 [PubMed - in process]
Birds of a feather may flock together, but do birds that flock together develop distinct cultures? Two studies published today in Science find strong evidence that, at the very least, monkeys that troop together and whales that pod together do just that. And they manage it in the same way that humans do: by copying and learning from each other.
New feeding strategy spreads among whales gathered to gorge on fish, says a new studyâ€”but is it culture?
Morphology and Variation in Porpoise (Cetacea: Phocoenidae) Cranial Endocasts.
Anat Rec (Hoboken). 2013 Apr 24;
Authors: Racicot RA, Colbert MW
Abstract Evolution of endocranial anatomy in cetaceans is important from the perspective of echolocation ability, intelligence, social structure, and alternate pathways for circulation to the brain. Apart from the importance of studying brain shape and asymmetries as they relate to aspects of behavior and intelligence, cranial endocasts can show a close correspondence to the hydrostatic shape of the brain in life, and canals and grooves can preserve features of the circulatory system. Multiple samples are rarely available for studies of individual variation, especially in fossils, thus a first step in quantifying variation and making comparisons with fossils is made possible with CT scans of osteological specimens. This study presents a series of high-resolution X-ray CT-derived cranial endocasts of six extant species of Phocoenidae, a clade including some of the smallest and one of the rarest cetaceans. Degree of gyrification varies interspecifically and intraspecifically, possibly resulting from variation in preservation of the ossified meninges. Computed tomographic data show that visually assessed asymmetry in the cranial endocasts is not correlated with volumetric measurements, but nonetheless may reflect torsion in the skull's shape such that the right cerebral and cerebellar hemispheres extend rostrally and laterally more than the left. Vasculature and canals are similar to other described cetacean species, but the hypophyseal casts are unusual. Similarities between brain shape and volume measurements in the different species can be attributed to paedomorphism and concomitant variation in ecological preferences. This may explain similarities Neophocaena phocaenoides and Phocoena sinus share with the juvenile Phocoena phocoena specimen studied. Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.
PMID: 23613315 [PubMed - as supplied by publisher]
New research, led by WHOI postdoctoral fellow Frants Havmand Jensen, shows that freshwater dolphins produce echolocation sounds at very low sound intensities compared to marine dolphins, and that the endangered Ganges river dolphins echolocate at surprisingly low sound frequencies.
Ancient invasion of an extinct gammaretrovirus in cetaceans.
Virology. 2013 Mar 29;
Authors: Wang L, Yin Q, He G, Rossiter SJ, Holmes EC, Cui J
Abstract Endogenous gammaretroviruses (EGVs) have been widely studied in terrestrial mammals but seldom so in marine species. A genomic mining of the bottlenose dolphin (Tursiops truncatus) genome revealed a new EGV, termed Tursiops truncatus endogenous retrovirus (TTEV), which is divergent from extant mammalian EGVs. Molecular clock dating estimated the invasion time of TTEV into the host genome to be approximately 10-19 million years ago (MYA), while a previously identified killer whale endogenous gammaretrovirus (KWERV) was estimated to have invaded the host genome approximately 3-5 MYA. Using a PCR-based technique, we then verified that similar endogenous viruses exist in nine cetacean genomes. Phylogenetic analysis revealed that these cetacean EGVs are highly divergent from their counterparts in other mammals, including KWERV from the killer whale. In sum, we conclude that there have been at least two invasion episodes of EGVs into cetaceans during their evolutionary history.
PMID: 23545142 [PubMed - as supplied by publisher]
"Snotworms" and carcass-hopping limpets are some of the creatures inhabiting the whale's skeleton.
Genetic Evidence of Multiple Matrilines and Spatial Disruption of Kinship Bonds in Mass Strandings of Long-finned Pilot Whales, Globicephala melas.
J Hered. 2013 Mar 13;
Authors: Oremus M, Gales R, Kettles H, Baker CS
Abstract Mass strandings of whales and dolphins have puzzled biologists since Aristotle. Although environmental factors are often assumed to initiate strandings, social forces must also influence the dynamics of many of these events, particularly for the primary species involved in mass strandings, the long-finned pilot whales (Globicephala melas). Here, we test two hypotheses derived from common assumptions about the social dynamics of long-finned pilot whales by identifying maternal lineages from mtDNA haplotypes and inferring kinship from microsatellite genotypes of 490 individuals from 12 stranding events. Contrary to the "extended matriline" hypothesis, we found that multiple maternal lineages were present in at least 9 of the 12 mass strandings. Contrary to the "kinship cohesion" hypothesis, we found no correlation between spatial distribution and kinship along the stranding beach. Most notably, we documented the spatial disruption of the expected proximity between mothers and their dependent calves. These results challenge the common assumption that kinship-based behavior, such as care-giving, are a primary factor in these mass strandings. We suggest instead that disruption of kinship bonds could result from interactions among unrelated social groups during feeding or mating aggregations, perhaps playing a causal role in these events. Our finding that dependent calves were often spatially separated or absent from their mothers has important implications for humane management of rescue efforts. To improve our understanding of the social causes and consequences of mass strandings, future documentation of strandings should include exhaustive DNA sampling, with accompanying spatial and temporal records.
PMID: 23493607 [PubMed - as supplied by publisher]