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Analyses of marine mammal stranding data in the Philippines
- Lemnuel Aragones
- Joseph Masangkay
- Maria A AUXILIA Siringan
Stranding of marine mammals is complex and understanding this phenomenon requires continuous surveillance, monitoring, data collection and research. The Philippine Marine Mammal Stranding Network (PMMSN) has collected 1178 records of stranding events nationwide from 2005 to 2020. This Technical Report is a follow-up to the second Report (i.e., Aragones and Laggui 2019). As stated in the second Technical Report the consequent series of Reports will cover two-year periods only. Thus, this third Report covers the stranding dataset from 2019 to 2020. However, as in the first (Aragones et al. 2017) and second Reports, updates on the general trends for the larger data set (2005 to 2020) will also be provided. This Report showcases analyses of the stranding records from 2019 to 2020 (n=220) for trends in stranding frequency by year, region, season, monsoon, species, sex, age class, original disposition, release and rehabilitation success. The spatial coverage presented in this report was specific to regions and provinces primarily for administrative purposes. Identification of more specific or smaller spatial areas (i.e., by municipality/city) for potential stranding hotspots was assessed using Fishnet Tools (using 15 x 15 km grids). Furthermore, seasonality of stranding events was categorized according to the prevailing monsoons. The Northeast (NE) monsoon months are November to February (NDJF), Southwest (SW monsoon) monsoon months are June to September (JJAS), and Spring Inter-monsoon (Spring IM) in October (or Lull before NE monsoon) and the Winter Inter-monsoon (Winter IM) from March to May (MAM, or Lull before SW monsoon). The stranding data was also presented in the more classic seasonal context of DJF, MAM, JJA, SON. As data analytics advances, future reports will be improved further.
The spinner dolphin (Stenella longirostris) is one of the smallest odontocetes that commonly strands in the Philippines. Despite its apparent abundance and cosmopolitan distribution, there is no published data on the haematological and serum chemical reference values for this species. This limitation greatly affects the ability of veterinarians and marine mammal rehabilitators to make informed decisions in the diagnosis and treatment of diseases, and the formulation of action plans when individuals of this species strand alive. This study used blood samples from two subadult female spinner dolphins that were successfully rehabilitated after stranding in 2014 to establish haematological and serum chemistry reference values for the species. The overall resulting values of the blood parameters recorded such as the WBC (5.01-10.45 10 3 /μL), RBC (4.23-6.18 10 6 /μL), and PCV (42-50%) generally demonstrated narrow ranges and were close to the published reference values for other similar conspeci c odontocetes. Although there were only two individuals of the species used in this study, the data gathered serves as a valuable reference tool for future cases of spinner dolphin strandings in the Philippines.
Stranding of marine mammals is complex and understanding it requires more data and studies. The Philippine Marine Mammal Stranding Network (PMMSN) has collected 952 records of stranding events nationwide from 2005 to 2018. This Technical Report is a follow-up to the first Report (i.e. Aragones et al. 2017), which analyzed strandings data from 2005 to 2016, and this second series covered two years (2017-2018). The next series of Reports will similarly cover two-year periods only. As in the first Report, this second Report will initially give the general trends for the larger data set (2005 to 2018). The bulk of this Report is about the analyses of the stranding records from 2017-2018 (n= 229) for trends in stranding frequency by year, region, season, species, gender, age class, original disposition, release and rehabilitation success. The spatial coverage presented in this report was specific to regions and provinces primarily for administrative purposes. Identification of more specific or smaller spatial areas (i.e. by municipality/ city) for potential stranding hotspots was assessed using Fishnet Tools (using 15 x 15 km grids). Furthermore, seasonality of stranding events was categorized according to the prevailing monsoons. The Northeast (NE) monsoon months are November to February (NDJF), Southwest (SW monsoon) monsoon months are June to September (JJAS), and Spring Inter-monsoon (Spring IM) in October (or Lull before NE monsoon) and the Winter Inter-monsoon (Winter IM) from March to May (MAM, or Lull before SW monsoon). As data analytics advances, future reports will be improved further.
Toothed whales possess a sophisticated biosonar system by which ultrasonic clicks are projected in a highly directional transmission beam. Beam directivity is an important biosonar characteristic that reduces acoustic clutter and increases the acoustic detection range. This study measured click characteristics and the transmission beam pattern from a small odontocete, the spinner dolphin (Stenella longirostis). A formerly stranded individual was rehabilitated and trained to station underwater in front of a 16-element hydrophone array. On-axis clicks showed a mean duration of 20.1 μs, with mean peak and centroid frequencies of 58 and 64 kHz [standard deviation (s.d.) ±30 and ±12 kHz], respectively. Clicks were projected in an oval, vertically compressed beam, with mean vertical and horizontal beamwidths of 14.5° (s.d. ± 3.9) and 16.3° (s.d. ± 4.6), respectively. Directivity indices ranged from 14.9 to 27.4 dB, with a mean of 21.7 dB, although this likely represents a broader beam than what is normally produced by wild individuals. A click subset with characteristics more similar to those described for wild individuals exhibited a mean directivity index of 23.3 dB. Although one of the broadest transmission beams described for a dolphin, it is similar to other small bodied odontocetes.
Blast fishing is an illegal and unsustainable practice that is often reported in Southeast Asia and Africa. Its impact on fish and reef-building corals is well documented, yet there is limited information on the effects on other larger species and near-shore predators. In recent years, several marine mammal strandings in the Philippines have coincided with underwater explosions associated with blast fishing. The goal of this study was to measure the hearing of stranded dolphins, including two spinner dolphins (Stenella longirostris) and two rough-toothed dolphins (Steno bredanensis), that were rehabilitated in Subic Bay at Ocean Adventure in cooperation with the Philippines Marine Mammal Stranding Network and Wildlife in Need. Hearing measurements were conducted using noninvasive auditory brain stem responses (ABRs). Test stimuli consisted of tone pips ranging from 8 to 128 kHz. The results indicated elevated thresholds and limited hearing range, including three individuals with no hearing response beyond 22.5 kHz. These results may indicate evidence of hearing loss associated with blast and related impulsive sound exposure.
A well-maintained marine mammal stranding data-base can be an invaluable tool in understanding not only strandings but also changes in the marine environment. This study aimed to examine the fol-lowing aspects of marine mammal strandings in the Philippines: species composition, temporal (i.e., frequency of stranding per year and seasonality) and spatial (i.e., frequency of stranding per region and province) variation, proportions of alive or dead specimens, and stranding hotspots. In 2008, a sys-tematic collection of data on strandings, including out-of-habitat incidents, resulted in an initial 12-year database—from 1998 to 2009. A total of 178 strand-ing events were recorded: 163 single, 10 mass, and 5 out-of-habitat strandings, with an average of 15 observed stranding events annually. Twenty-three of the 28 confirmed species of marine mammals in the Philippines were recorded to strand, including first-recorded specimens for the Indo-Pacific bot-tlenose dolphin (Tursiops aduncus), pygmy sperm whale (Kogia breviceps), and Longman's beaked whale (Indopacetus pacificus). The top five most frequent species to strand included spinner dol-phin (Stenella longirostris) (n = 26), short-finned pilot whale (Globicephala macrorhynchus) (n = 14), melon-headed whale (Peponocephala electra) (n = 13), Risso's dolphin (Grampus griseus) (n = 11), and common bottlenose dolphin (T. truncatus) (n = 10). Dugongs (Dugong dugon) stranded seven times since 2001. Strandings occurred through-out the year with frequency significantly peaking during the northeast (NE) monsoon (November to March) season. Overall, Regions III (Central Luzon) and VII (Central Visayas) had the highest number of strandings (both n = 27) followed by Regions I (Ilocos) (n = 22) and V (Bicol) (n = 18). The following provinces or local government units were considered hotspots based on high number of strandings observed at each area: Zambales, Cagayan, Zamboanga City, Negros Oriental, Bohol, Pangasinan, and Bataan. Sixty-five percent of all documented stranding events involved live (n = 116) animals. This high percentage might be linked to dynamite fishing (causing acoustic trauma), fish-eries interactions, or biotoxins from harmful algal blooms coupled to their foodweb. These strandings in general validate the diverse marine mammal assemblage in the Philippines and reveal the vari-ous environmental threats with which they deal.
EXECUTIVE SUMMARY Marine mammals strand for various reasons. The recorded Philippine marine mammal stranding events from 2005 to 2016 was analyzed for patterns on (1) species composition of stranded marine mammals, (2) spatial and temporal variation of stranding events, and (3) proportions of alive and dead specimens, to mention a few. A total of 713 stranding events have been recorded comprised mainly of single stranders (n=638), mass stranding events (n=31), out of habitat (n=15) and Unusual Mortality Events (n=29). The UMEs occurred in Region I only. The annual frequency of recorded stranding events ranged from 24 (2005) to 111 (2015), with an average of 59 events per year. Most of the strandings occurred in Luzon (60%) while Visayas and Mindanao had equal share (20% each). Strandings have been recorded in all regions with coastline and in 64 coastal provinces. The top five regions on a national level which have had the highest number of recorded stranding events (i.e. stranding hotspots) were: Regions I (n= 158), V (n=92), VII (n=68), III (n=53) and II (n=48). The regions with the least number of recorded stranding events were: NCR (n=3), ARMM (n=6), 13 (n=11). In the Visayas, Region VI (n=47) was also an area of concern, apart from Region VII. Similarly, in Mindanao Regions XII (n=44), XI (n=42), and IX (n=25) were hotspots. Region IX was considered as a hotspot primarily because it has the highest proportion of live stranders on record (84%, 21 of 25). Overall, 60% (n=430) of all recorded stranding events involved live animals. In terms of seasonality, strandings were relatively more frequent during the Northeast monsoon (NE) in most provinces than the Southwest monsoon or Inter-monsoon. The bulk of the recorded strandings (76%) came from the top 20 provinces of the 64 represented. The top six provinces in terms of frequency of recorded strandings were Pangasinan (n= 63), Ilocos Norte (n= 52), Cagayan (n= 40), Sarangani (n= 37), Sorsogon (n=30), and Zambales (n=29). A total of 29 species (28 cetaceans plus the dugong) of marine mammals have been recorded throughout the Philippines, mostly confirmed through stranding records. Of the 29 species, 27 have stranding records, with Regions III and V both having the highest number of marine mammal species recorded (n=17); followed by Regions I and II (n=16), and 3 (n=15). The most frequent species that stranded was the spinner dolphin (Stenella longirostris, n=115), followed by the Fraser’s dolphin (Lagenodelphis hosei, n=67), Risso’s dolphin (Grampus griseus, n=52), melon-headed whale (Peponocephala electra, n=45), Pantropical spotted dolphin (Stenella attenuate, n=37), dwarf sperm whale (Kogia sima, n=36), and the dugong (Dugong dugon, n=36). Another notable result was that the spinner dolphins was the most common stranded species and had been recorded to have stranded in 15 out of 16 regions. This implies that the spinner dolphin is most likely the most abundant and widely distributed marine mammal species in the Philippines. On the other hand, only 23 (3%) records of baleen whale strandings were documented. Majority of the stranding events involved adults (n=501, 70%). The ratio of stranded females to males was almost even (0.92). Furthermore, a total of 1561 individuals were recorded to have been involved in all (n=713) stranding events from 2005 to 2016: out of habitat = 745, single = 651, mass = 134, and UME = 31. All the out of habitat animals, except three (3), eventually made it back to open seas. Out of the single stranders, 395 (61%) stranded alive. Of these, 329 were released immediately or after a few hours of supportive care, including 5 baleen whales (i.e. adults to sub-adults). Sixty-six individuals were rehabilitated: 48 died (72%), 11 released (17%), 4 (6%) long-term care, and 3 euthanized (4%). The response to strandings has remarkably improved through time. This was mainly attributed to the significant increase in numbers of PMMSN Chapter chapters and trained volunteers nationwide. The PMMSN now have at least 12 collaborating BFAR Regional Offices, 11 with MOAs and 1 currently being worked out. In 2010, 5 years after the establishment of PMMSN, there were 1736 trained volunteers. To date, there are 3690 trained volunteers, including at least 75 veterinarians who underwent a special training on medical management for stranded marine mammals. The existence of active PMMSN Chapters in several regions through the initiatives of BFAR Regional Directors, and local chief executives of provinces and cities/municipalities has enabled better response than before. Further, BFAR Regional Offices in regions I, II, II, IVA, V, VII, VIII, XI, and XIII have either already organized or are planning to organize provincial chapters of PMMSN through their Provincial Fisheries Offices to further enhance their capacity to respond to strandings. Regions IX, X and XII are currently setting up their respective Chapters. However, there are still many challenges. For instance, the coordination between the individual(s) who initially discover stranded marine mammals and trained local personnel (responders) needs to improve. Most often the discovering parties do not know who to call. This is unfortunate because, to date, there are many trained locals, especially in strategic (hotspot) areas, who are knowledgeable about stranding first response protocols. Supposedly, the assistance of the pertinent personnel from BFAR Regional Office (e.g. veterinarian) and/or PMMSN, would be required or immediately pursued only if there was no local individual(s) trained or after the animal has been given first aid and stabilized. Another challenge is finding accessible pond or enclosures for possible use as holding pens for rehabilitation of stranded animals in remote areas. Another noteworthy finding was the significant number of live animals rescued and released back into their habitats. For the last 12 years, at least 329 individuals were released after providing supportive care. That was equivalent to 27 animals per year. Furthermore, the success rate of rehabilitation has increased from 12% in 2010 to 23%, to date. The 11 animals successfully rehabilitated was equivalent to almost 1 animal released per year. Furthermore, four dolphins, mostly victims of dynamite blasts, and therefore are acoustically challenged, and with almost nil chances of survival if released, are now under human care with their conspecifics. The PMMSN has also observed increasing cases of stranders (dead or dying) with compacted GIT by marine debris. A systematic collection of information regarding these sorts of cases and the like is now in place. These would not have been possible if there was no organized national stranding network (i.e. the PMMSN) that looked after their welfare as well as systematically collected data. Ultimately, the engagement of empowered communities (e.g. PMMSN Chapters), especially mandated agencies (i.e. BFAR, LGUs) and their respective leaders, made the difference for the Philippine marine mammal strandings.
The general consensus of a rapidly changing ocean ecosystem being affected by anthropogenic activities needs to be understood in relation to both wildlife and human health. The risks and challenges for the Philippines include lack of scientific information on waterborne diseases that are potentially zoo-notic. The present study fills in this knowledge gap by detecting the occurrence of bacteria, Giardia, and Toxoplasma gondii in locally found cetacean species. Cetaceans (n = 30) that stranded from January 2012 through March 2013 were appropriately responded to, and biological materials were taken whenever applicable. A total of 25 bacteria were isolated from nine stranders. Phenotypic and genotypic methods of isolate identification yielded 12 consensus genera: Acinetobacter, Aeromonas, Burkholderia, Enterococcus, Moraxella, Proteus, Providencia, Rhizobium, Serratia, Sphingomonas, Staphylococcus, and Vibrio. No screened strander was positive for Giardia. Serological assay detected antibodies for T. gondii in five stranders, while nested polymerase chain reaction positively amplified the B1 gene of the parasite in two stranders. This study provides the first report on bacteria and T. gondii in cetaceans found in the Philippines. Since the detected microorganisms include species recognized to cause new infections in marine mammals worldwide, the findings of the study underscore the potential of stranded cetaceans to serve as sentinels for studying the movement of emerging pathogens in marine habitats, provide clues on the health status of their free-ranging populations, and present the health risks available to humans who share the same water resource with them.