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SPECIAL REPORT, PART 1 OF 3

PHL study finds increasing number of marine mammal strandings


There has been an increase in marine mammal-strandings in the country the last 12 years, a study conducted by marine scientists from the University of the Philippines-Diliman found.

These strandings involved dolphins, baleen whales, and dugongs that had been found beached along coastal barangays in different parts of the country.

These beached animals were weakened after they get entangled in fish nets, wounded after colliding with vessels, while others had serious blast injuries. Some of these marine mammals were also on the brink of death, if not already dead, because they had ingested debris or trash from the ocean.

UP Professor Lemnuel Aragones, biophysicist Honey Leen Laggui, and marine biologist Apple Kristine Amor of the Marine Mammal Research and Stranding Laboratory-Institute of Environmental Science and Meteorology warned that the rate of strandings could put further stress on already vulnerable species.

Their study found that the annual frequency of recorded stranding events ranged from 24 in 2005 to 111 incidents in 2015, with an average of 59 events per year.

 

A spinner dolphin was rescued by the local community in Barangay Pantao, Libon in Albay province last March 4, 2017. PHOTO BY ELMER CAÑETA

 

The experts noted that a total of 713 stranding events had been recorded from 2005 to 2016, or around 59 marine mammals strandings in coastal barangays in the Philippines per year. This translates to five strandings per month or to at least one mammal per week.

Sixty percent of these incidents were recorded in Luzon, and only 20 percent each in the Visayas and Mindanao.

The most commonly stranded mammal in the country are spinner dolphins, but other marine mammals common to Philippine waters, such as other dolphin species, dugongs, and dwarf sperm whales, were also stranded.

Aragones underscored in the study that dugongs, which are listed by the International Union for Conservation of Nature (IUCN) as a vulnerable species, should be closely monitored.

Hotspots

By definition, marine mammals are considered stranded when an individual or group is beached, or if they run aground and are helpless and are not able to return to their natural habitats.

A stranded marine mammal can be categorized as live or dead, single or mass, and out-of-habitat depending on its initial state when it was discovered.

Records show that within the 12-year period of the study, there were 638 single stranders and 31 instances of mass strandings, while 15 mammals were stranded out of their habitat.

Unique to Region I is a record of 29 UMEs or unusual mortality events.

The top five regions that are considered hotspots for marine mammal stranding, are Regions I with 158 incidents, Region V with 92 incidents, 68 incidents were recorded in the Central Visayas, while 53 were listed in Region III, and 48 for Region II.

These hotspot areas, Aragones said, could mean that there was a combination of high fishing effort and abundant marine mammals in these areas, resulting in a conflict in resource use.

The use and prevalence of illegal fishing methods could also be making the situation worse.

Observed stranding patterns

The strandings were observed to follow the country's weather patterns.

During the northeast monsoon season, there was a higher frequency of recorded stranding events compared to the southwest monsoon season.

Aragones said that most upwellings in strandings, particularly those in the western sections of large islands like Luzon, are at their maximum during the northeast monsoon.

The implication is that during these seasons, coastal areas experience an abundance in prey thus attracting some cetaceans (dolphins, porpoises, whales) closer to shore.

Though stranding events in Luzon peak in the month of April, this was most likely due to the impact of lag effect of the northeast monsoon on prey movement, and eventually, strandings.

Further study of environmental parameters, such as bathymetry, chlorophyll-a, and sea surface temperatures, will allow the scientist to co-relate these parameters to strandings in the Philippines.

Explanation for stranding incidents

The marine scientists admitted that more research was needed to accurately explain the reasons behind the strandings.

However, their 12-year study had provided them with some clues.

In 2015, scientists found 25 types of bacteria from samples taken from 30 cetaceans that were stranded from January 2012 to March 2013.

It was found that some of these microorganisms had the potential to cause new infections in marine mammals worldwide. This particular finding could have a huge implication on the potential movement of pathogens or disease-causing microorganisms in the marine environment.

The recorded stranding events of marine mammals in the country were also being analyzed in relation to different environmental factors and contaminants, such as polychlorinated biphenyls - a chemical byproduct from manufacturing industries.

A recent report also highlighted the impact of dynamite blasts on rough-toothed and spinner dolphins that were found in the west coast of Luzon.

Aragones pointed out that there was a need to continue to comprehensively report and record strandings, and further examine the possible causes of this seemingly increasing trend.

A well-maintained marine mammal stranding database could serve as a vital tool in understanding, not only strandings, but also the changing marine environment. — DVM, GMA News



Part 2: Strandings confirm diversity in the country's marine mammals

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