345 research outputs found
False killer whale dorsal fin disfigurements as a possible indicator of long-line fishery interactions in Hawaiian Waters
Scarring resulting from entanglement in fishing gear can be used to examine cetacean fishery interactions. False killer whales (Pseudorca crassidens) are known to interact with the Hawai'i-based tuna and swordfish long-line fishery in offshore Hawaiian waters. We examined the rate of major dorsal fin disfigurements of false killer whales from nearshore waters around the main Hawaiian Islands to assess the likelihood that individuals around the main islands are part of the same population that interacts with the fishery. False killer whales were encountered on 11 occasions between 2000 and 2004, and 80 distinctive individuals were photographically documented. Three of these (3.75%) had major dorsal fin disfigurements (two with the fins completely bent over and one missing the fin). Information from other research suggests that the rate of such disfigurements for our study population may be more than four times greater than for other odontocete populations. We suggest that the most likely cause of such disfigurements is interactions with longlines and that false killer whales found in nearshore waters around the main Hawaiian Islands are part of the same population that interacts with the fishery. Two of the animals documented with disfigurements had infants in close attendance and were thought to be adult females. This implies that even with such injuries, at least some females may be able to produce offspring, despite the importance of the dorsal fin in reproductive thermoregulation
The arctic circle boundary and the Airy process
We prove that the, appropriately rescaled, boundary of the north polar region
in the Aztec diamond converges to the Airy process. The proof uses certain
determinantal point processes given by the extended Krawtchouk kernel. We also
prove a version of Propp's conjecture concerning the structure of the tiling at
the center of the Aztec diamond.Comment: Published at http://dx.doi.org/10.1214/009117904000000937 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Repeated call types in Hawaiian melon-headed whales (Peponocephala electra)
Author Posting. © Acoustical Society of America, 2014. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 136 (2014): 1394, doi:10.1121/1.4892759.Melon-headed whales are pantropical odontocetes that are often found near oceanic islands. While considered sound-sensitive, their bioacoustic characteristics are relatively poorly studied. The goal of this study was to characterize the vocal repertoire of melon-headed whales to determine whether they produce repeated calls that could assist in recognition of conspecifics. The first tag-based acoustic recordings of three melon-headed whales were analyzed. Tag records were visually and aurally inspected and all calls were individually extracted. Non-overlapping calls with sufficient signal-to-noise were then parameterized and visually grouped into categories of repeated call types. Thirty-six call categories emerged. Categories differed significantly in duration, peak and centroid frequency, and â3 dB bandwidth. Calls of a given type were more likely to follow each other than expected. These data suggest that repeated calls may function in individual, subgroup, or group recognition. Repeated call production could also serve to enhance signal detection in large groups with many individuals producing simultaneous calls. Results suggest that caution should be used in developing automatic classification algorithms for this species based on small sample sizes, as they may be dominated by repeated calls from a few individuals, and thus not representative of species- or population-specific acoustic parameters.This project was funded by the Office of Naval Research
(award number: N000141110612; Program Manager Michael
J. Weise), WHOI Marine Mammal Center, and the Sawyer
and Penzance Endowed Funds, with additional field time
funded by grants through Cascadia Research Collective by
the National Oceanographic Partnership Program (through
the Alaska SeaLife Center) and the Pacific Islands Fisheries
Science Center
Acoustic differentiation of Shiho- and Naisa-type short-finned pilot whales in the Pacific Ocean
Author Posting. © Acoustical Society of America, 2017. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 114 (2017): 737â748, doi: 10.1121/1.4974858.Divergence in acoustic signals used by different populations of marine mammals can be caused by a variety of environmental, hereditary, or social factors, and can indicate isolation between those populations. Two types of genetically and morphologically distinct short-finned pilot whales, called the Naisa- and Shiho-types when first described off Japan, have been identified in the Pacific Ocean. Acoustic differentiation between these types would support their designation as sub-species or species, and improve the understanding of their distribution in areas where genetic samples are difficult to obtain. Calls from two regions representing the two types were analyzed using 24 recordings from Hawaiâi (Naisa-type) and 12 recordings from the eastern Pacific Ocean (Shiho-type). Calls from the two types were significantly differentiated in median start frequency, frequency range, and duration, and were significantly differentiated in the cumulative distribution of start frequency, frequency range, and duration. Gaussian mixture models were used to classify calls from the two different regions with 74% accuracy, which was significantly greater than chance. The results of these analyses indicate that the two types are acoustically distinct, which supports the hypothesis that the two types may be separate sub-species.Funding for
Hawaiian data collection was provided by grants from the
Pacific Islands Fisheries Science Center and Office of Naval
Research, as well as Commander, Pacific Fleet. The
SoundTrap was purchased with funding from the Scripps
Institution of Oceanography/National Science Foundation
Interdisciplinary Graduate Education in Research
Techniques fellowship program. DMON data collection and
portions of the analysis were funded by the Office of Naval
Research [Grant Nos. N000141110612 (T.A.M. and R.W.B.)
and N00014-15-1-2299 (M.A.R.); Program Manager
Michael J. Weise], and WHOI Marine Mammal Center and
the Sawyer and Penzance Endowed Funds to T.A.M
Patterns of depredation in the Hawaiâi deep-set longline fishery informed by fishery and false killer whale behavior
False killer whales (Pseudorca crassidens) depredate bait and catch in the Hawaiâi-based deep-set longline fishery, and as a result, this species is hooked or entangled more than any other cetacean in this fishery. We analyzed data collected by fisheries observers and from satellite-linked transmitters deployed on false killer whales to identify patterns of odontocete depredation that could help fishermen avoid overlap with whales. Odontocete depredation was observed on Ë6% of deep-set hauls across the fleet from 2004 to 2018. Model outcomes from binomial GAMMs suggested coarse patterns, for example, higher rates of depredation in winter, at lower latitudes, and with higher fishing effort. However, explanatory power was low, and no covariates were identified that could be used in a predictive context. The best indicator of depredation was the occurrence of depredation on a previous set of the same vessel. We identified spatiotemporal scales of this repeat depredation to provide guidance to fishermen on how far to move or how long to wait to reduce the probability of repeated interactions. The risk of depredation decreased with both space and time from a previous occurrence, with the greatest benefits achieved by moving Ë400 km or waiting Ë9 d, which reduced the occurrence of depredation from 18% to 9% (a 50% reduction). Fishermen moved a median 46 km and waited 4.7 h following an observed depredation interaction, which our analysis suggests is unlikely to lead to large reductions in risk. Satellite-tagged pelagic false killer whales moved up to 75 km in 4 h and 335 km in 24 h, suggesting that they can likely keep pace with longline vessels for at least four hours and likely longer. We recommend fishermen avoid areas of known depredation or bycatch by moving as far and as quickly as practical, especially within a day or two of the depredation or bycatch event. We also encourage captains to communicate depredation and bycatch occurrence to enable other vessels to similarly avoid high-risk areas
Whistle characteristics and daytime dive behavior in pantropical spotted dolphins (Stenella attenuata) in Hawaiâi measured using digital acoustic recording tags (DTAGs)
Funding to support P.L.T. was received from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.This study characterizes daytime acoustic and dive behavior of pantropical spotted dolphins (Stenella attenuata) in Hawaiâi using 14.58âh of data collected from five deployments of digital acoustic recording tags (DTAG3) in 2013. For each tagged animal, the number of whistles, foraging buzzes, dive profiles, and dive statistics were calculated. Start, end, minimum, and maximum frequencies, number of inflection points and duration were measured from 746 whistles. Whistles ranged in frequency from 9.7â±â2.8 to 19.8â±â4.2âkHz, had a mean duration of 0.7â±â0.5âs and a mean of 1.2â±â1.2 inflection points. Thirteen foraging buzzes were recorded across all tags. Mean dive depth and duration were 16â±â9âm and 1.9â±â1.0âmin, respectively. Tagged animals spent the majority of time in the upper 10âm (76.9%â±â16.1%) of the water column. Both whistle frequency characteristics and dive statistics measured here were similar to previously reported values for spotted dolphins in Hawaiâi. Shallow, short dive profiles combined with few foraging buzzes provide evidence that little spotted dolphin feeding behavior occurs during daytime hours. This work represents one of the first successful DTAG3 studies of small pelagic delphinids, providing rare insights into baseline bioacoustics and dive behavior.Publisher PDFPeer reviewe
A SURVEY FOR ODONTOCETE CETACEANS OFF KAUAâI AND NIâIHAU, HAWAIâI, DURING OCTOBER AND NOVEMBER 2005: EVIDENCE FOR POPULATION STRUCTURE AND SITE FIDELITY
Considerable uncertainty exists regarding population structure and population sizes of most species of odontocetes in the Hawaiian Islands. A small-boat based survey for odontocetes was undertaken off the islands of Kauaâi and Niâihau in October and November 2005 to photoidentify individuals and collect genetic samples for examining stock structure. Field effort on 24 days covered 2,194 km of trackline. Survey coverage was from shallow coastal waters out to over 3,000 m depth, though almost half (47%) was in waters less than 500 m in depth. There were 56 sightings of five species of odontocetes: spinner dolphins (30 sightings); bottlenose dolphins (14 sightings); short-finned pilot whales (6 sightings); rough-toothed dolphins (5 sightings); and pantropical spotted dolphins (1 sighting). One hundred and five biopsy samples were collected and 14,960 photographs were taken to document morphology and for individual photo-identification. Photographs of distinctive individuals of three species (bottlenose dolphins, 76 identifications; rough-toothed dolphins, 157 identifications; short-finned pilot whales, 68 identifications) were compared to catalogs of these species from a survey off Kauaâi and Niâihau in 2003, as well as from efforts off Oâahu, Maui/Lanaâi and the island of Hawaiâi. Within- and between-year matches were found for all three species with individuals previously identified off Kauaâi and Niâihau, though no matches were found with individuals off any of the other islands. This suggests site fidelity to specific island areas, and population structure among island areas for all three species. Movements of photographically identified bottlenose dolphins were documented between deep water areas off the islands of Kauaâi and Niâihau, as well as between shallow (\u3c350 m) and deep (\u3e350 m) waters. A lack of sightings or reports of false killer whales off Kauaâi or Niâihau during our study, combined with documented movements among the other main Hawaiian Islands, suggest that there is no âresidentâ population of false killer whales that inhabits waters only off Kauaâi or Niâiha
Unexpected patterns of global population structure in melon-headed whales Peponocephala electra
Foraging specialization, environmental barriers, and social structure have driven the development of strong genetic differentiation within many marine species, including most of the large dolphin species commonly referred to as âblackfishâ (subfamily Globicephalinae). We used mitochondrial sequence data (mtDNA) and genotypes from 14 nuclear microsatellite loci (nDNA) to examine patterns of genetic population structure in melon-headed whales Peponocephala electra (MHWs), poorly known members of the blackfish family for which genetic structuring is unknown. MHWs are globally distributed in tropical and subtropical waters, and have formed resident populations around oceanic islands. They frequently mass strand, suggesting strong social cohesion within groups. Based on these characteristics, we hypothesized that MHWs would exhibit strong regional genetic differentiation, similar to that observed in other members of the Globicephalinae subfamily. Instead we found only moderate differentiation (median mtDNA ΊST = 0.204, median nDNA FST = 0.012) among populations both within and between ocean basins. Our results suggest that populations of MHWs that are resident to oceanic islands maintain a higher level of genetic connectivity than is seen in most other blackfish. MHWs may be more behaviorally similar to delphinids from the Delphininae subfamily (particularly the spinner dolphin Stenella longirostris), which are known to form coastal and island-associated resident populations that maintain genetic connectivity either through occasional long-distance dispersal or gene flow with larger pelagic populations. Our results suggest that differences in social organization may drive different patterns of population structure in social odontocete
Impact of catchment-derived nutrients and sediments on marine water quality on the Great Barrier Reef: an application of the eReefs marine modelling system
Water quality of the Great Barrier Reef (GBR) is determined by a range of natural and anthropogenic drivers that are resolved in the eReefs coupled hydrodynamic - biogeochemical marine model forced by a process-based catchment model, GBR Dynamic SedNet. Model simulations presented here quantify the impact of anthropogenic catchment loads of sediments and nutrients on a range of marine water quality variables. Simulations of 2011â2018 show that reduction of anthropogenic catchment loads results in improved water quality, especially within river plumes. Within the 16 resolved river plumes, anthropogenic loads increased chlorophyll concentration by 0.10 (0.02â0.25) mg Chl mâ3. Reductions of anthropogenic loads following proposed Reef 2050 Water Quality Improvement Plan targets reduced chlorophyll concentration in the plumes by 0.04 (0.01â0.10) mg Chl mâ3. Our simulations demonstrate the impact of anthropogenic loads on GBR water quality and quantify the benefits of improved catchment management
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