scholarly journals Trends in the distribution and abundance of cetaceans from aerial surveys in Icelandic coastal waters, 1986-2001

2009 ◽  
Vol 7 ◽  
pp. 117 ◽  
Author(s):  
Daniel G Pike ◽  
Charles GM Paxton ◽  
Thorvaldur Gunnlaugsson ◽  
Gísli A Víkingsson
Keyword(s):  
Relative Abundance ◽  
Minke Whale ◽  
Humpback Whales ◽  
Line Transect ◽  
Survey Area ◽  
Balaenoptera Acutorostrata ◽  
The North ◽  
Aerial Surveys ◽  
Minke Whales ◽  
Abundance Estimates

Aerial surveys were carried out in coastal Icelandic waters 4 times between 1986 and 2001 as part of the North Atlantic Sightings Surveys. The surveys had nearly identical designs in 3 of the 4 years. The target species was the minke whale (Balaenoptera acutorostrata) but all species encountered were recorded. Sighting rate and density from line transect analysis were used as indices of relative abundance to monitor trends over the period, and abundance estimates corrected for perception biases were calculated for some species from the 2001 survey. More than 11 species were sighted, of which the most common were the minke whale, humpback whale (Megaptera novaeangliae), dolphins of genus Lagenorhychus, and the harbour porpoise (Phocoena phocoena). Minke whales anddolphins showed little change in distribution or abundance over the period. There were an estimated 31,653 (cv 0.30) dolphins in the survey area in 2001. Humpback whales increased rapidly at a rate of about 12%, with much of the increase occurring off eastern and northeastern Iceland. In 2001 there were an estimated 4,928 (cv 0.463) humpback whales in the survey area. The relative abundance of harbour porpoises decreased over the period, but estimates for this species were compromised by uncorrected perception biases and poor coverage. The ecological and historical significance of these findings with respect to previous whaling activities and present-day fisheries is discussed.

scholarly journals Distribution and Abundance of Cetaceans in Icelandic Waters over 30 Years of Aerial Surveys

2020 ◽  
Vol 11 ◽  
Author(s):  
Daniel Pike ◽  
Thorvaldur Gunnlaugsson ◽  
Johann Sigurjonsson ◽  
Gisli Vikingsson
Keyword(s):  
Relative Abundance ◽  
Humpback Whales ◽  
Line Transect ◽  
Balaenoptera Acutorostrata ◽  
Aerial Surveys ◽  
Minke Whales ◽  
Abundance Estimates ◽  
Ecosystem Changes ◽  
Common Minke Whale ◽  
Icelandic Waters

Beginning in 1986, 7 aerial surveys covering the coastal waters of Iceland have been conducted up to 2016. In addition, several partial surveys covering portions of the same area and at different times of the year have been flown in the same 30 year time span. We present previously unpublished abundance estimates, corrected to the extent feasible for known biases, for common minke whales (Balaenoptera acutorostrata), humpback whales (Megaptera novaeangliae), white-beaked dolphins (Lagenorhynchus albirostris) and harbour porpoises (Phocoena phocoena) from some or all of the 2007, 2009 and 2016 surveys. The relative abundance of most species was comparatively low in the spring and fall, and peaked June and July when all of the main surveys have been carried out. An analysis of changes in line transect density as an index of relative abundance from all surveys indicates that common minke whale abundance decreased by 75% after 2001 and has remained at a relatively low level since then. Relative abundance of humpback whales and white-beaked dolphins has increased over the period 1986-2016. We place these observed changes in context with oceanographic and ecosystem changes documented over the same period.

Aerial surveys of cetaceans in the Gulf of St. Lawrence in 1995 and 1996

1998 ◽  
Vol 76 (8) ◽  
pp. 1529-1550 ◽  
Author(s):  
MCS Kingsley ◽  
R R Reeves
Keyword(s):  
Humpback Whales ◽  
Delphinapterus Leucas ◽  
Line Transect ◽  
Balaenoptera Acutorostrata ◽  
North Shore ◽  
The North ◽  
Minke Whales ◽  
Fin Whales ◽  
Pilot Whales ◽  
Blue Whales

Aerial line-transect surveys of cetaceans were flown in the Gulf of St. Lawrence in late August and early September of 1995 and in late July and early August of 1996. Systematic north-south transects were spaced 15prime of longitude apart. In 1995, the study area comprised the entire Gulf, divided into three strata for analysis; 69% was flown. In 1996, a single stratum covered only the north shore shelf; 75% of the design was flown. The survey platform was a light high-winged aircraft with bubble windows flown at 213 m (700 ft). Ten species were seen. Minke whales (Balaenoptera acutorostrata), Atlantic white-sided dolphins (Lagenorhynchus acutus), and harbour porpoises (Phocoena phocoena) yielded enough sightings to support good estimates, while fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), white-beaked dolphins (Lagenorhynchus albirostris), and long-finned pilot whales (Globicephala melas) yielded few sightings and unreliable estimates. Blue whales (Balaenoptera musculus) and belugas (Delphinapterus leucas) were seen too rarely to support any analysis. The tenth species was a small delphinid, not positively identified. Minke whales were ubiquitous, but more common in the northern strata. We estimated about 1000 in the whole Gulf in 1995 and about 600 in the northernmost stratum in 1996 (these numbers, and those following, are uncorrected for visibility bias). We estimated about 12 000 Atlantic white-sided dolphins in the Gulf in 1995, but in 1996 saw hardly any, perhaps because we flew the survey earlier. Harbour porpoises (12 000 in 1995 and 21 000 in 1996) were most numerous in the northern stratum, but were also widely distributed at lower densities in the central and southern Gulf. White-beaked dolphins (2500 in 1995 and 2500 in 1996) occurred only in the Strait of Belle Isle and the extreme northeastern Gulf. We estimated a few hundred fin whales in the northern and central strata and about 100 humpbacks, mostly in the northeast. Long-finned pilot whales were only seen in the southeastern Gulf, surveyed only in 1995 (about 1500).

scholarly journals Changes in blood testosterone and progesterone concentrations of the North Atlantic minke whale (Balaenoptera acutorostrata) during the feeding season

2004 ◽  
Vol 61 (2) ◽  
pp. 230-237 ◽  
Author(s):  
Matthías Kjeld ◽  
Árni Alfredsson ◽  
Örn Ólafsson ◽  
Morten Tryland ◽  
Ivar Christensen ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
North Atlantic ◽  
Minke Whale ◽  
Balaenoptera Acutorostrata ◽  
Hunting Season ◽  
P Values ◽  
The North ◽  
Minke Whales ◽  
The North Atlantic ◽  
Cyclic Changes

An opportunity to study seasonal changes of sex hormones in the North Atlantic minke whale (common minke whale, Balaenoptera acutorostrata) arose when we obtained access to fresh postmortem blood samples from 104 females and 83 males. The whales were caught in the North Atlantic during May–September 1992–1995. Serum progesterone (P) and testosterone (T) concentrations were measured and compared with anatomical data. The frequency distribution of female serum P values showed two clusters, one consisting mainly of immature animals and the second of pregnant ones, with mean serum values of about 0.49 ± 0.04 (SE) and 44.2 ± 2.84 nmol·L–1, respectively. The frequency distribution of male serum T did not show any group-specific distribution during the hunting season. The mean serum T value for the males was 0.63 ± 0.13 nmol·L–1. Contrary to earlier reports on the Antarctic minke whale (Balaenoptera bonaerensis), serum T values rose during the hunting season in mature males (p < 0.0001). Serum P values in immature females increased during the season (p = 0.015). This increase agrees with the predominantly annual reproduction cycle of minke whales. Blood sex hormone measurements seem to be useful for detecting cyclic changes and pregnancy of minke whales.

Marine megavertebrates of Cornwall and the Isles of Scilly: relative abundance and distribution

2011 ◽  
Vol 92 (8) ◽  
pp. 1823-1833 ◽  
Author(s):  
Ruth H. Leeney ◽  
Matthew J. Witt ◽  
Annette C. Broderick ◽  
John Buchanan ◽  
Daniel S. Jarvis ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Bottlenose Dolphins ◽  
Marine Biodiversity ◽  
Balaenoptera Acutorostrata ◽  
Delphinus Delphis ◽  
Mola Mola ◽  
Aerial Surveys ◽  
Minke Whales ◽  
Pilot Whales ◽  
Common Dolphins

We document patterns of distribution and relative abundance of marine megavertebrate fauna around Cornwall and the Isles of Scilly from a combination of aerial and boat-based surveying. Between January 2006 and November 2007, 20 aerial surveys were undertaken, comprising over 40 hours of on-effort flying time. In April to October of these years, 27 effort-corrected ferry surveys were also conducted from a passenger ferry travelling between Cornwall and the Isles of Scilly. Opportunistic sightings were also logged by the crew members of the ferry and another vessel travelling regularly along the same route on 155 days. Ten megavertebrate species were sighted: basking sharks Cetorhinus maximus, sunfish Mola mola, common dolphins Delphinus delphis, harbour porpoise Phocoena phocoena, grey seals Halichoerus grypus, Risso's dolphins Grampus griseus, bottlenose dolphins Tursiops truncatus, minke whales Balaenoptera acutorostrata, long-finned pilot whales Globicephala melas and killer whale Orcinus orca. During aerial surveys, 206 sighting events of seven species were made, compared with 145 sighting events of eight species during ferry surveys and 293 sighting events of 10 species from opportunistic ship-board data collection efforts. Seasonal and spatial patterns in species occurrence were evident. Basking sharks were the most commonly-sighted species in the region and were relatively abundant throughout the estimated 5 km-wide strip of coastal waters covered by the aerial surveys, during spring and summer. Ferry surveys and opportunistic vessel-based sightings data confirmed that the distribution of surface-feeding aggregations of this species was largely around the coasts. Despite the limited scope of this study, it has provided valuable baseline data, and possible insights into the marine biodiversity of the region.

Accounting for responsive movement in line transect estimates of abundance

2001 ◽  
Vol 58 (4) ◽  
pp. 777-787 ◽  
Author(s):  
D L Palka ◽  
P S Hammond
Keyword(s):  
Animal Movement ◽  
Generalized Additive Models ◽  
Radial Distance ◽  
Additive Models ◽  
Line Transect ◽  
The North ◽  
Minke Whales ◽  
Orientation Density ◽  
Using Data ◽  
Animal Orientation

A method is developed to account for effects of animal movement in response to sighting platforms in line transect density estimates using data on animal orientation. Models of expected distributions of animal orientation show that presence of responsive movement is determined by the ratio of animal sightings with angles of orientation in the third quadrant relative to the first quadrant. The distance at which response began is estimated using logistic generalized additive models of the relationship between radial distance and orientation. Density corrected for responsive movement is estimated by applying the Buckland and Turnock two-team analysis method to data poststratified into regions "close" to and "far" from (beyond the distance that responsive movement began) the observation platform instead of the original stratification by observation team. For data collected in the North Atlantic, white-sided dolphins, harbor porpoises, and minke whales responded by avoiding the survey ship, and white-beaked dolphins were attracted to the ship. For these populations, our method to correct for responsive movement gave significantly higher estimates, from 1.4 to 2.7 times the uncorrected estimates.

Errors in identification using natural markings: rates, sources, and effects on capture–recapture estimates of abundance

2001 ◽  
Vol 58 (9) ◽  
pp. 1861-1870 ◽  
Author(s):  
Peter T Stevick ◽  
Per J Palsbøll ◽  
Tim D Smith ◽  
Mark V Bravington ◽  
Philip S Hammond
Keyword(s):  
Error Rate ◽  
Large Scale ◽  
False Negative ◽  
Parametric Bootstrap ◽  
Humpback Whales ◽  
The North ◽  
Abundance Estimates ◽  
Capture Recapture ◽  
Quality Rating ◽  
Estimation Of Variance

The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision.

Interspecific cetacean interactions during the breeding season of humpback whale (Megaptera novaeangliae) on the north coast of Bahia State, Brazil

2009 ◽  
Vol 89 (5) ◽  
pp. 961-966 ◽  
Author(s):  
Marcos R. Rossi-Santos ◽  
Elitieri Santos-Neto ◽  
Clarêncio G. Baracho
Keyword(s):  
Breeding Season ◽  
Megaptera Novaeangliae ◽  
Humpback Whales ◽  
North Coast ◽  
Balaenoptera Acutorostrata ◽  
Cetacean Species ◽  
The North ◽  
Eastern Brazil ◽  
North Eastern ◽  
Stenella Attenuata

The large majority of cetacean interspecific studies report only on dolphin interactions, while studies on interactions between odontocete and mysticete are less common. The present work aims to report on sightings of cetacean interactions, during the breeding season of humpback whales(Megaptera novaeangliae), along 370 km of the Bahia State, north-eastern Brazil, addressing aspects of cetacean distribution and behaviour. During 7 seasons (2000–2006), a total of 230 research cruises were performed, in which 38 events of interactions among humpback whales and other cetaceans(Tursiops truncatus, Steno bredanensis, Peponocephala electraandBalaenoptera acutorostrata)were observed, plus another 5 encounters without the whale's presence, includingT. truncatus, S. bredanensis, P. electra, Stenella clymeneandStenella attenuata. Our results confirm the occurrence of multiple cetacean species in the Bahia State, being the first study in the world to report on a large range of interactions involving another 4 cetacean species, grouped with up to 3 mixed species per sighting, with humpback whales in their annual breeding ground.

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