Inter-Annual Variability in Blue Whale Distribution off Southern Sri Lanka between 2011 and 2012

Vos, Asha de; Pattiaratchi, Charitha; Harcourt, Robert; Mawatha, Ramanayake; Lanka, Sri

doi:10.3390/jmse2030534

Cited by 23 publications

(35 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observation that blue whales (Balaenoptera musculus) feed off the southern coast of Sri Lanka during the NE monsoon period (de Vos et al, 2014) provided the motivation for this study. The NE winds, under Ekman dynamics, would generate a downwelling system (onshore Ekman flow) along the southern coast of Sri Lanka, resulting in a low primary productive system.…”

Section: Discussionmentioning

confidence: 99%

“…During the SW monsoon, where the winds blow parallel to the coast, winds are upwelling favourable in terms of Ekman dynamics. Chlorophyll concentrations during the NE monsoon appear to be low, but there is evidence of high productivity through the documented feeding aggregations of blue whales (Balaenoptera musculus) along the southern coast of Sri Lanka (de Vos et al, 2014). Field observations have shown that ∼ 6-10 whales are sighted per day along the southern coast of Sri Lanka (data from 2009 to 2011).…”

mentioning

confidence: 99%

“…The motivation for the paper is the observation of blue whale (Balaenoptera musculus) feeding aggregations off the southern coast of Sri Lanka during the NE monsoon period (de Vos et al, 2014), despite satellite imagery indicating lower productivity in the surface waters. This paper is organised as follows: in Sect.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Surface circulation and upwelling patterns around Sri Lanka

2014

View full text Add to dashboard Cite

Abstract. Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean, with the Arabian Sea on its western side and the Bay of Bengal on its eastern side, and experiences bi-annually reversing monsoon winds. Aggregations of blue whale (Balaenoptera musculus) have been observed along the southern coast of Sri Lanka during the northeast (NE) monsoon, when satellite imagery indicates lower productivity in the surface waters. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 3 years to examine the seasonal and shorter-term (∼ 10 days) variability. The results reproduced correctly the reversing current system, between the Equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the southwest (SW) monsoon transporting 11.5 Sv (mean over [2010][2011][2012] and the westward flowing Northeast Monsoon Current (NMC) transporting 9.6 Sv during the NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the southern coast. During the SW monsoon, the island deflects the eastward flowing SMC southward, whilst along the eastern coast, the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the southern coast, resulting from southward flow converging along the southern coast and subsequent divergence associated with the offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind-driven flow along the eastern and western coasts: during the SW (NE) monsoon, the flow along the western (eastern) coast was stronger, migrating the upwelling centre to the east (west).

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Surface circulation and upwelling patterns around Sri Lanka

2014

View full text Add to dashboard Cite

show abstract

“…Furthermore, it has been established that there is a year-round resident population of Northern Indian Ocean blue whales B. m. indica in Sri Lanka (e.g. de Vos et al 2014) based only on observations of blue whales in the waters surrounding Sri Lanka during every month of the year (Ilangakoon & Sathasivam 2012). We similarly present evidence of blue whale sighting reports in New Zealand waters during every month of the year, which is corroborated by acoustic detections of the New Zealand blue whale call on 99.7% of recording days by at least 1 hydrophone during 2016.…”

Section: Discussionmentioning

confidence: 99%

Documentation of a New Zealand blue whale population based on multiple lines of evidence

Barlow¹,

Torres²,

Hodge³

et al. 2018

Endang. Species. Res.

View full text Add to dashboard Cite

Species conservation depends on robust population assessment. Data on population abundance, distribution, and connectivity are critical for effective management, especially as baseline information for newly documented populations. We describe a pygmy blue whale Balaenoptera musculus brevicauda population in New Zealand waters with year-round presence that overlaps with industrial activities. This population was investigated using a multidisciplinary approach, including analysis of survey data, sighting records, acoustic data, identification photographs, and genetic samples. Blue whales were reported during every month of the year in the New Zealand Exclusive Economic Zone, with reports concentrated in the South Taranaki Bight (STB) region, where foraging behavior was frequently observed. Five hydrophones in the STB recorded the New Zealand blue whale call type on 99.7% of recording days (January to December 2016). A total of 151 individuals were photo-identified between 2004 and 2017. Nine individuals were resighted across multiple years. No matches were made to individuals identified in Australian or Antarctic waters. Mitochondrial DNA haplotype frequencies differed significantly between New Zealand (n = 53 individuals) and all other Southern Hemisphere blue whale populations, and haplotype diversity was significantly lower than all other populations. These results suggest a high degree of isolation of this New Zealand population. Using a closed capturerecapture population model, our conservative abundance estimate of blue whales in New Zealand is 718 (SD = 433, 95% CI = 279−1926). Our results fill critical knowledge gaps to improve management of blue whale populations in New Zealand and surrounding regions.

show abstract

“…Line-transect surveys were conducted in both ecosystems using large research vessels (i.e. Black crosses represent Soviet whaling data (1963)(1964)(1965)(1966) collected during the November inter-monsoon and black circles represent Soviet whaling data (1963)(1964)(1965)(1966) and more recent sightings (1995, 1998, and 2012) collected within the monsoon seasons Mikhalev 2000;Ballance et al, 2001;de Vos et al, 2014b). Survey effort consisted of two observers using pedestal-mounted 25 9 150 binoculars to search for marine mammals during daylight hours; a third observer searched by eye or with 79 handheld binoculars and recorded both sightings data and survey conditions.…”

Section: Blue Whale Ecology and Datamentioning

confidence: 99%

Predicting cetacean distributions in data‐poor marine ecosystems

Redfern

Moore

Fiedler

et al. 2017

Diversity and Distributions

Self Cite

View full text Add to dashboard Cite

Aim Human activities are creating conservation challenges for cetaceans. Spatially explicit risk assessments can be used to address these challenges, but require species distribution data, which are limited for many cetacean species. This study explores methods to overcome this limitation. Blue whales (Balaenoptera musculus) are used as a case study because they are an example of a species that have well-defined habitat and are subject to anthropogenic threats.Location Eastern Pacific Ocean, including the California Current (CC) and eastern tropical Pacific (ETP), and northern Indian Ocean (NIO).Methods We used 12 years of survey data (377 blue whale sightings and c. 225,400 km of effort) collected in the CC and ETP to assess the transferability of blue whale habitat models. We used the models built with CC and ETP data to create predictions of blue whale distributions in the data-poor NIO because key aspects of blue whale ecology are expected to be similar in these ecosystems. Results We found that the ecosystem-specific blue whale models performed well in their respective ecosystems, but were not transferable. For example, models built with CC data could accurately predict distributions in the CC, but could not accurately predict distributions in the ETP. However, the accuracy of models built with combined CC and ETP data was similar to the accuracy of the ecosystem-specific models in both ecosystems. Our predictions of blue whale habitat in the NIO from the models built with combined CC and ETP data compare favourably to hypotheses about NIO blue whale distributions, provide new insights into blue whale habitat, and can be used to prioritize research and monitoring efforts.Main conclusions Predicting cetacean distributions in data-poor ecosystems using habitat models built with data from multiple ecosystems is potentially a powerful marine conservation tool and should be examined for other species and regions.

show abstract

Inter-Annual Variability in Blue Whale Distribution off Southern Sri Lanka between 2011 and 2012

Cited by 23 publications

References 43 publications

Surface circulation and upwelling patterns around Sri Lanka

Surface circulation and upwelling patterns around Sri Lanka

Documentation of a New Zealand blue whale population based on multiple lines of evidence

Predicting cetacean distributions in data‐poor marine ecosystems

Contact Info

Product

Resources

About