report’of’ eiobws2015’...
TRANSCRIPT
Report of EIOBWS2015
(Eastern Indian Ocean Blue Whale Survey 2015)
Centre for Whale Research Crew Members Carrying
TEM Pennant 2 (written by Micheline & Curt Jenner)
1. Introduction This report covers a recent exploration expedition, the Eastern Indian Ocean Blue Whale Survey 2015 (EIOBWS2015), in the Eastern Indian Ocean on board RV Whale Song. The authors sought to investigate the presence of cetaceans, in particular blue whales, in a near box-‐shaped survey positioned in deep, offshore waters. The purpose of this journey was to document the spatial and temporal distribution, if possible, of blue whales, a largely oceanic species in the ocean basin of the eastern sector of the Indian Ocean. The Centre for Whale Research (Western Australia) Inc., crew aboard RV Whale Song, namely Curt and Micheline Jenner proudly carried TEM (The Explorers Museum) Pennant 2 on this exploratory voyage and are deeply honoured to report the findings. 2. Materials and Methods 2.1 Background Shipboard surveys of cetaceans have been routinely conducted by scientists utilising line transect surveys (Buckland et al. 2001) with visual searching (Holt, 1987; Buckland et al, 1992; Wade & Gerrodette, 1993; Barlow, 1995; Schweder et al. 1996) as undertaken on this voyage. Passive acoustic monitoring simultaneously, offers the advantage of an elevated chance of animal detection (Gordon & Steiner, 1992; Leaper et al. 1992) and with the possibility of a 75% higher chance of detecting acoustically than visually (Payne, 1994) both aspects of detecting cetaceans were employed on this exploration expedition. Cetaceans undertake extremely long migrations between feeding and breeding grounds. These annual migratory paths employed by humpback whales outlined in several papers Chittleborough (1965), Dawbin (1966) in the Southern Hemisphere waters of Australia and Katona & Beard (1990) and Perry et al. (1990) across Northern Hemisphere regions, are well documented. Fin whales, a large baleen whale also migrates across open oceans (Mackintosh & Wheeler 1929, Mackintosh 1966). Evidence that blue whales must also undertake these extensive movements came from year-‐round surveys in the Antarctic (Mackintosh 1966) indicating a rise and fall of baleen
whales consistent with migration. The extent of migrations by Antarctic blue whales in the Indian Ocean has been of interest to the authors for many years. From recent work by the authors on pygmy blue whales, a sub-‐species of blue whales, new understanding of their migrations from summer feeding grounds in the Perth Canyon in Western Australia to winter breeding grounds in the Banda Sea of Indonesia has been shown by satellite tag data (Double et al, 2014). Commercial whaling decimated Southern Hemisphere blue whale populations between 1904 and 1973 with whaling catches numbering 303, 239 animals (Branch et al. 2007). Two sub-‐species of blue whales are recognised in the Indian Ocean, the Antarctic blue whale (Balaenoptera musculus intermedia) of >30 m maximum size and the pygmy blue whale (Balaeanoptera musculus brevicauda), slightly smaller at 24 m maximum size. Current research indicates Antarctic blue whales, which once numbered 239,000 (95% Bayesan interval 202,000-‐311,000) (Branch et al. 2004) dropped to very low levels before increasing to an estimated number in 1998 of 2,280 (95% Bayesan interval 1,160-‐4,500), still only 1% of their pre-‐whaling population (Branch et al, 2004). Pygmy blue whales, generally encountered north of 540 South in summer were not targeted as heavily by the whalers due to their location north of the ice-‐edge and slightly smaller size. However, even given these factors, 13,000 pygmy blue whales were taken (Double et al. 2014). Recently, the Western Australian population has been estimated using photo-‐mark recapture as 712-‐1,754 individuals (Jenner et al. 2008) and from acoustic recordings 662-‐1,559 individuals (McCauley & Jenner 2010). These cetaceans, the Antarctic blue whale and the pygmy blue whale are the largest mammals, the largest marine mammals and the largest animals on earth. Despite their enormous size and presence, much remains a mystery surrounding the winter breeding locations of these two species. By traversing a large area of the Indian Ocean the authors hoped to address several of these issues by searching for Antarctic blue whales in one continuous track-‐line through areas not frequently surveyed and across regions of interesting bathymetry perhaps supporting dynamic upwelling and or, down-‐welling and possibly whale congregations. The region explored on this journey encompassed a variety of oceanic habitats including seamounts, abyssal plains, and deep sea ridges. In particular seamounts and ridges are focusses for the prey species of whales, mostly due to upwelled nutrients that drive food chains on seasonal or even perpetual cycles. The study vessel, RV Whale Song, is an ocean-‐going vessel, fully equipped for offshore, deep water research with long-‐range fuel capability, ample victual storage and comfortable accommodations. It is ideal for exploring the most remote open ocean habitats. This journey, EIOBWS2015 carrying TEM Pennant 2, commenced at Cocos Keeling Islands (Australia) in the Eastern Indian Ocean and proceeded westwards towards Ninety East Ridge and then south-‐south-‐east towards Broken Ridge and eastward along The Naturaliste Plateau to Fremantle, Western Australia (Figure 1). This voyage took place from November 15, 2015-‐December 02, 2015, being 18 days covering 2588 nautical miles.
Figure 1. EIOBWS2015 from Cocos Keeling Islands to Fremantle, Western Australia. 2.2 Visual Observations 2.2.1 Cetacean Observations On a daily basis, visual observations for cetaceans were made by at least two crew personnel, commencing at 0700 (within one hour after sunrise) and concluding at 1800 (within one hour before sunset). A variety of variables were recorded at each cetacean sighting including latitude/longitude, species, behaviour, number of animals in the pod and direction of movement as well as weather details including Beaufort Wind Scale, wind direction, swell height, swell direction and SST (sea surface temperature). Visual observations were made daily, even during weather creating poor sighting conditions (generally deemed unsuitable for sighting cetaceans), since there was still the chance of seeing an animal passing the bow and being able to be identified. 2.2.2 Seabird Observations During the visual observations for cetaceans, seabird observations were recorded simultaneously. Eleven species of seabirds were encountered, identified with high-‐resolution photographs. 2.3 Acoustic Observations Acoustic observations were made for the entire survey, therefore continuously across each 24 hour period using a deployed towed array. The array used was 450m in length and consisted of 4 elements. Acoustic signals were recorded and interpreted using PAMGUARD with a standard spectrogram display of time versus frequency in the 1-‐35kHz acoustic range to account for identifying blue whale calls below 100Hz. Screen shots were recorded of detections of interest and the location of all acoustic detections were marked on the nautical chart. The details of each acoustic detection were recorded
in two formats, manually and in a computer database. All acoustic detections will be subject to further analysis using the PAMGUARD software. 3. Results 3.1 Visual Observations A surprisingly small number of visual sightings of cetaceans were made over the course of the 18 days and the 2588 nautical miles of the survey, as listed in Table 1. _____________________________________________________________________________________________________ Date Species Lat/ # Pods # Anis Photo-‐id Ac. Detect.
Long (Y/N) (Y/N) 19/11/15 Pygmy Killer whale 170 44.8S 1 1 N Y 0890 23.1E 25/11/15 Common dolphin 290 46.8S 1 30 N Y 0970 02.7E 28/11/15 Fin whale 330 13.6S 3 3 Y N 1030 12.0E 30/11/15 Killer whale 320 52.2S 1 1 N Y 1090 23.9E 02/12/15 Humpback whale 310 58.2S 1 2 Y N 1150 29.5 _____________________________________________________________________________________________________ TOTAL 7 37 2 3 _____________________________________________________________________________________________________ Table 1. Cetaceans encountered on EIOBWS2015 from Cocos Keeling Islands to Ninety East Ridge to Fremantle, Western Australia.
3.1.2 Seabird Observations Seabird species were represented by eleven species. High quality photographs were taken to identify each seabird to species level as listed in Table 2. _____________________________________________________________________________________________ Seabird Species # in Flock Distance (nm) from land _____________________________________________________________________________________________ Abbott’s Booby 15 54 from CKI Great Frigatebird 2 250 from CKI Sooty Terns 20 250 from CKI White-‐tailed Tropicbird 1 395 from CKI Wilson Storm Petrel 1 1218 from Carnarvon, WA
1 1201 from Carnarvon, WA 1 1024 from Murch. River, WA 1 743 from Perth, WA
Great-‐winged Petrel 1 1212 from Carnarvon, WA Wedge-‐Tailed Shearwater 1 1201 from Perth, WA
1 1136 from Perth, WA 1 1127 from Perth, WA 1 1123 from Perth, WA 1 1044 from Perth, WA 1 1025 from Perth, WA 1 743 from Perth, WA 1 733 from Perth, WA 1 730 from Perth, WA
Barau’s Petrel 2 -‐ Bulwer’s Petrel 1 1046 from Murch. River, WA
Shy Albatross 1 480 from Perth, WA 1 460 from Perth, WA Wandering Albatross 1 300 from Perth, WA Petrel spp 2 -‐ _____________________________________________________________________________________ Total Birds Obs 60 _____________________________________________________________________________________ Table 2. Seabird species in order encountered on EIOBWS2015 from Cocos Keeling Islands to Ninety East Ridge to Fremantle, Western Australia.
3.2 Acoustic Detections Overall 95 acoustic detections were made. Of these, three sources were identified, being recordings listed as Natural, Man-‐Made or Biological as listed in Table 3. _____________________________________________________________________________________________________ Type of Acoustic Source # Detections Detection _____________________________________________________________________________________________________ Natural Rain 2 Man-‐made Ship 3 Biological Cetacean 90
Total 95 _____________________________________________________________________________________________________ Table 3. Acoustic detections made on EIOBWS2015 from Cocos Keeling Islands to Fremantle, Western Australia.
Figure 2. Acoustic detections of cetaceans (black crosses) between Cocos Keeling Islands and Fremantle, Western Australia. Of the Biological detections, being cetaceans (whales and dolphins), the majority were attributed to dolphins (55), sperm whales (23), beaked whales (8), pygmy killer whale (1), killer whale (1), common dolphins (1) and fin whale (1). Many of the biological detections, particularly the possible beaked whale detections still require confirmation of species. The most abundant detections were biological, comprising 91% and of these, over half of the recordings were dolphin whistles. Sperm whale clicks contributed to 25% of the acoustic detections. On several occasions, sperm whale “locating”/”hunting” clicks were heard and seen on the acoustic screens, (10 per 14 seconds) as the whale searched for their squid prey. Next, “seeking” clicks (20 per 14 seconds) were engaged as a prey item appeared to have been detected and then accelerated “killing” clicks (30 per 14 seconds) whereby, prey was being sonically bombed with clicks. Two-‐3-‐5 minutes of silence then occurred during which time the whale was assumed to consuming the conquered prey. On one occasion in the evening, 7 hours and 25minutes of continuous “hunting”/”seeking”/”killing” clicks were detected from 1800 until 0225, the following
morning. Due to the continuous nature of the clicks, it was apparent that this sperm whale pod was most likely a nursery pod comprised of females and juveniles, the juveniles being cared for at the surface during feeding bouts on a rotating basis by related and unrelated female adults. Unfortunately, we did not stay in the area as the ship was travelling away from bad weather, but if we had remained we may well have encountered a pod of between 20-‐30 individuals (Whitehead & Rendell, 2015). A single sighting of a single pygmy killer whale observed (Jenner pers. comm.) racing across the bow of Whale Song at close range (<10 m), allowed for identification of the extremely unique acoustic call that was recorded on towed array. Given the volume and variety of different signals recorded simultaneously, it was evident that at least 4-‐5 or more individuals were calling in this particular instance. Another unique sighting was a killer whale, (possibly 2 animals) as we approached Rottnest Island. A splash was observed (Jenner pers. comm.) followed by a small round blow, and then a killer whale was sighted swimming at great speed (est. > 39 km/hr) northward towards another blow, which was tall and columnar – possibly a baleen whale. The two whales continued to move north rapidly much faster than the RV Whale Song could follow. 4. Conclusions Open ocean surveys reveal new and interesting data. The compliment of cetacean species encountered was certainly within the expected suite of cetaceans but the lack of Antarctic blue whales, remains an ongoing puzzle for the authors. It may be that blue whales were present in the region surveyed, but due to the vast distances involved, were simply not detected in the temporal and spatial window we searched. The bathymetry, particularly of Broken Ridge and the Naturaliste Plateau are suitable upwelling habitats that likely support krill, the prey for baleen whales, and indeed they are within the region of blue whale whaling fleets up until 1973. The expectation of finding Antarctic blue whales (undertaking an austral autumn migration) or even pygmy blue whales (north of 540 S) was reasonable and worthy of an exploratory venture. With the extreme reduction of Antarctic blue whales by commercial whaling, and the resulting low population being around 1% of the pre-‐whaling population, the small number of individuals in the Southern Hemisphere means that finding “pocket populations” across open ocean basins is extremely difficult. Prey concentrations are likely to be patchy and clumped and therefore similarly affect blue whale distribution. Few documented records of feeding blue whales have been collected recently, but one included a large congregation of Antarctic blue whales encountered in east Antarctica during March (Double et al., 2013) feeding against the ice-‐edge. Also New Zealand blue whales (likely pygmy blue whales) have been photo-‐identified year-‐round in the southern Taranaki Bight (Olson et al., 2015). Locational conditions (involving particular bathymetry, specific oceanography variables and high chlorophyll-‐a levels) appear to be the optimal conditions for foraging blue whales. These examples of seasonal and perpetual feeding areas give us hope that similar locations will eventually be found in the Southern Indian Ocean. The desire to find wintering Antarctic blue breeding grounds and autumn migratory paths remains of great interest to the authors and as such, research on all open ocean journeys will continue during any subsequent voyages.
5. References Barlow, J (1995) The abundance of cetaceans in California waters. Part 1: Ship surveys in summer and fall of 1991. Fishery Bulletin, U.S. 93:1-‐14. Branch, T.A., Matsuoka, K. & Miyashita, T. (2004) Evidence for increases in Antarctic blue whales based on Bayesian modelling. Marine Mammal Science, 20, 726–754. Branch, T.A., Stafford, K.M., Palacios, D.M., Allison, C., Bannister, J.L., Burton, C.L.K., Cabrera, E., Carlson, C.A., Galletti Vernazzani, B., Gill, P.C., Hucke-‐Gaete, R., Jenner, K.C.S., Jenner, M.N.M., Matsuoka, 4 SC/65/XXX 5 K., Mikhalev, Y.A., Miyashita, T., Morrice, M.G., Nishiwaki, S., Sturrock, V.J., Tormosov, D., Anderson, R.C., Baker, A.N., Best, P.B., Borsa, P., Brownell Jr, R.L., Childerhouse, S., Findlay, K.P., Gerrodette, T., Ilangakoon, A.D., Joergensen, M., Kahn, B., Ljungblad, D.K., Maughan, B., McCauley, R.D., McKay, S., Norris & T.F., Rankin, S., (2007) Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean. Mammal Rev. 37, 116-‐175. Buckland, S.T., K.L. Cattanack & T. Gunnlaugsson (1992) Fin whale abundance in the North Atlantic, estimated from Icelandic and Faroese NASS-‐87 and NASS-‐89 data. Rep Int Whal Commn 42:645-‐651. Buckland, S.T., D.R. Anderson, K.P. Burnham, J.L. Laake, D.L. Burchers & L. Thomas (2001) Introduction to distance sampling: Estimating abundance of biological populations. Oxford University Press, Oxford, UK. Chittleborough, R.G. (1965) Dynamics of two populations of the humpback whale, Megaptera novaeangliae (Borowski). Aust J Freshwat Res 16:33-‐128. Dawbin, W.H. (1966) The seasonal migratory cycle of humpback whales. In: KS Norris (ed) Whales, Dolphins and Porpoises. University of California Press, Berkeley, p145-‐170. Double, M.C., Barlow, J., Miller, B.S., Olson, P., Andrews-‐Goff, V., Leaper, R., Ensor, P., Kelly, N., Lindsay, M., Peel, D., Calderan, S., Collins, K., Davidson, M., Deacon, C., Donnelly, D., Olavarria, C., Owen, K., Rekdahl, M., Schmitt, N., Wadley, V. & Gales, N. (2013) Cruise report of the 2013 Antarctic blue whale voyage of the Southern Ocean Research Partnership. Paper SC/65/XX presented to the IWC Scientific Committee. Galletti Vernazzani, B., Carlson, C.A Double, M.C., V. Andrews-‐Goff, K.C.S. Jenner, M.-‐N. M. Jenner, S.M. Laverick, T.A. Branch & N. Gales (2014) Migratory movements of pygmy blue whales (Balaeanoptera musculus brevicauda) between Australia and Indonesia as revealed by satellite telemetry. PLOS ONE 9(4):e93578. Gordon, J. & L. Steiner (1992) Ventilation and dive patterns in sperm whales, Physeter macrocephalus, in the Azores. Rep Int Whal Commn 42:561-‐565. Holt RS (1987) Estimating density of dolphin schools in the eastern tropical Pacific Ocean using line transect methods. Fishery Bulletin, U.S. 85:419-‐434. Jenner, K.C.S, M.-‐N. M. Jenner & C.L.K. Burton (2008) Mark-‐recapture analysis of pygmy blue whales from the Perth Canyon, WA 2000-‐2005. Paper SC/60/SH16
submitted to IWC Sci Comm (unpublished). Available from the Int Whal Commn Secretariat Cambridge, UK. Katona, S.K. & J.A. Beard (1990) Population size, migrations and feeding aggregations of the humpback whale (Megaptera novaeangliae) in the western North Atlantic Ocean. Rep Int Whal Commn (Spec Issue 12): 295-‐305. Leaper, R., O. Chappell & J. Gordon (1992) The development of practical techniques for surveying sperm whale populations acoustically. Rep Int Whal Commn 42:549-‐560. Mackintosh, N.A. & J.F.G. Wheeler (1929) Southern blue and fin whales. Discovery Reports, 1, 257-‐540. Mackintosh, N.A. (1966) Distribution of southern blue and fin whales. In: Whales, Dolphins and Porpoises (Ed by KS Norris), pp125-‐144. University of California Press, Berkeley, CA. McCauley, R.D., K.C.S. Jenner, J.L. Bannister, C.L.K. Burton, D.H. Cato & A. Duncan (2001) Blue whale calling in the Rottnest Trench-‐2000, Western Australia. Report CMST R2001-‐6, Project-‐WA Museum/CMST241. Available at: http://www.curtin.edu.au/curtin/centre/cmst/publicat/2001-‐06.pdf. McCauley, R.D., J.L. Bannister, C.L.K. Burton, K.C.S. Jenner, S. Rennie & C.S. Kent (2004) Western Australian Exercise Area Blue Whale Project. Final Summary Report. Milestone 6. For Australian Defence. CMST Report R2004-‐29, Project-‐350. McCauley, R.D. & K.C.S. Jenner (2010) Migratory patterns and estimated population size of pygmy blue whales (Balaeanoptera musculus brevicauda) traversing the Western Australian coast based on passive acoustics. Paper SC/62/SH26 submitted to the IWC Sci Comm (unpublished). Available from the Int Whal Commn Secretariat Cambridge, UK. Olson, P.A., P. Ensor, Olavarria, C., Schmitt, N., Childerhouse, S., Constantine, R., Miller, B. S. & M.C. Double ( 2015) New Zealand blue whales: initial photo-‐identification of a little-‐known population. Rep Int Whal Comm SC/65a/SH12. Payne, R. (1994) Among Whales Schribner. 431pp. Perry, A., C.S. Baker & L.M. Herman (1990) Population characteristics of individuality identified humpback whales in the central and eastern North Pacific: a summary and critique. Rep Int Whal Commn (Spec Issue 12): 307-‐317. Schweder, T., G. Hagen, J. Helgeland & I. Koppervik (1996) Abundance estimation of northeastern Atlantic minke whales. Rep Int Whal Commn 43:391-‐405. Wade, P.R. & T. Gerrodette (1993) Estimates of abundance and distribution in the eastern tropical Pacific. Rep Int Whal Commn 43:477-‐493. Whitehead, H. & L. Rendall (2015) The Cultural Lives of Whales and Dolphins. University of Chicago Press. 417pp.