Local Cetacean Stranding Investigation

Background

Since May 2006, OPCFHK has been collaborating with Agriculture, Fisheries and Conservation Department (AFCD) to investigate the cetacean stranding cases in Hong Kong. Ocean Park also supports the Cetacean Stranding Response Team with technical expertise through their veterinary team and the Marine Mammal Department. The Response Team will attend the site timely after receiving a stranding report, to conduct necropsy on site or at Ocean Park, depending on the carcass condition, and collect samples for further examination.  In case of live stranding, OPCFHK will work with AFCD and Ocean Park to explore options of rescue.

In addition to establishing and managing the only Cetacean Stranding Response Team, OPCFHK has long participated in the work of the Marine Mammal Conservation Working Group (MMCWG), of which dolphin researchers, scientists, fishermen leaders and representatives from different government department also participate. OPCFHK shares findings from the stranding cases and provide group members with the latest conservation status of local cetaceans. OPCFHK makes recommendation to the Hong Kong SAR Government and helps AFCD to review and refine the Chinese white dolphin and finless porpoise conservation programmes.

Though most cases refer to carcass retrieval, we shall not undermine the importance of the bodies.  Necropsy and analysis on samples collected help us obtain important information:

In order to better understand the cause of death of stranded cetaceans in Hong Kong waters, and enhance the accuracy on such diagnosis, the Foundation has started a project jointly with Dr. Brian Kot, Assistant Professor from the Hong Kong Polytechnic University (PolyU) and Tung Wah College in April 2014 to perform virtopsy (i.e. is a virtual alternative or supplement to a traditional necropsy, conducted with computed tomography (CT) scanning and magnetic resonance imaging (MRI)) on stranded Chinese white dolphins and finless porpoises prior to conventional necropsy according to the status and condition of the stranded animal. We hope to generate invaluable initial or additional information which supplements the conventional necropsy practice.

Procedures

The members of “Stranding Response Team” (the Team) include the Foundation’s Scientific Team, Consulting Veterinarians and Conservation Assistants .  The Team is always ready to different places in HK to follow-up the case.  On the other hand, the Marine Mammal and Veterinary Teams of Ocean Park will provide assistance in fresh carcass necropsy and live stranding rescue when needed.

Stranding Cases

There are around 2,500 Chinese white dolphins in the Pearl River Estuary, including Hong Kong; and about 200 finless porpoises in Hong Kong and adjacent waters. The average number of cetacean stranding cases in Hong Kong ranged from 20 to 50 per annum over the years, with the two resident species Chinese white dolphin and finless porpoise as majority; and only a few cases of other species. However, we would only confirm the cause of death in around 10% of the cases, mainly because most of the carcasses were badly decomposed when discovered.

Stranding cases in 2018 (updated on June 30, 2018):

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 6 7 3 2 3 1             22
Chinese white dolphin 0 2 0 0 2 0             4
Others 0 0 0 0 2 1             3

Case number
(monthly)

6 9 3 2 7 2             29


Stranding cases in 2017:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 1 1 6 2 2 0 0 0 1 2 0 3 18
Chinese white dolphin 1 0 0 0 0 1 1 1 1 0 0 0 5
Others 0 0 0 1 0 0 0 0 0 1 0 1 3

Case number
(monthly)

2 1 6 3 2 1 1 1 2 3 0 4 26

 

Stranding cases in 2016:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 2 1 2 3 0 3 1 0 2 1 2 0 17
Chinese white dolphin 0 0 0 1 0 2 1 0 0 0 0 1 5
Others 1 0 0 0 1 0 0 1 0 0 0 0 3

Case number
(monthly)

3 1 2 4 1 5 2 1 2 1 2 1 25

 

Stranding cases in 2015:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 1 0 2 6 3 2 0 2 0 0 3 2 21
Chinese white dolphin 2 0 1 0 3 5 1 1 2 0 0 0 15
Others 1 0 0 0 0 0 0 0 0 0 0 0 1

Case number
(monthly)

4 0 3 6 6 7 1 3 2 0 3 2 37

 

Stranding cases in 2014:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 4 2 1 6 2 4 1 3 1 3 5 1 33
Chinese white dolphin 0 1 0 2 1 2 3 2 1 0 0 0 12
Others 0 0 1 0 1 0 0 0 2 1 0 0 5

Case number
(monthly)

4 3 2 8 4 6 4 5 4 4 5 1 50

 

Stranding cases in 2013:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 2 2 0 1 0 1 2 1 0 2 5 3 19
Chinese white dolphin 0 0 2 0 2 2 1 1 0 1 0 0 9
Others 0 0 0 0 0 0 0 0 0 0 0 0 0

Case number
(monthly)

2 2 2 1 2 3 3 2 0 3 5 3 28

 

Stranding cases in 2012:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 3 4 1 10 1 0 0 0 0 6 0 4 29
Chinese white dolphin 0 0 0 0 1 0 3 1 1 1 0 0 7
Others 0 0 0 0 0 0 0 0 0 0 0 0 0

Case number
(monthly)

3 4 1 10 2 0 3 1 1 7 0 4 36

 

Stranding cases in 2011:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 0 1 3 5 2 1 2 1 1 1 5 3 25
Chinese white dolphin 1 1 0 0 1 3 2 1 0 0 0 1 10
Others 0 0 0 1 0 0 0 0 0 0 0 0 1

Case number
(monthly)

1 2 3 6 3 4 4 2 1 1 5 4 36

 

Stranding cases in 2010:

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
Finless porpoise 3 1 0 2 2 3 2 3 0 0 1 3 20
Chinese white dolphin 0 0 0 0 0 2 0 1 2 0 0 2 7
Others 0 0 0 0 0 0 0 0 0 0 0 0 0

Case number
(monthly)

3 1 0 2 2 5 2 4 2 0 1 5 27

Click the link at each month to see the past stranding record.

the cases in December 2015 (last update: January, 2016): 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Stranding Numbers

Cetacean Stranding Cases in Hong Kong from 2006 to 2016:

  2006
*since May
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Total
Chinese white dolphin 4 17 8 7 7 10 7 9 12 15 5 5 106
Finless porpoise 6 23 14 19 20 25 29 19 33 21 17 18 244
Others # 0 0 2 2 0 1 0 0 5 1 3 3 17
Total stranding number
(by year)
10 40 24 28 27 36 36 28 50 37 25 26 367

* OPCFHK started handling cetacean stranding cases in Hong Kong since May 2006. There were total 22 cases in 2006, in which 5 cases were Chinese white dolphins and 17 cases were finless porpoises.


# Other stranded cetaceans recorded in Hong Kong waters (from 1955 to 2016) including fin whale (Balaenoptera physalus), Bryde's whale (Balaenoptera brydei), sperm whale (Physeter macrocephalus), pygmy sperm whales (Kogia breviceps), dwarf sperm whale (Kogia sima), Omura's whale (Balaenoptera omurai), false killer whale (Pseudorca crassidens), rough-toothed dolphin (Steno bredanensis), Risso's dolphin (Grampus griseus), Indo-Pacific bottlenose dolphin (Tursiops aduncus), common bottlenose dolphin (Tursiops truncatus), pantropical spotted dolphin (Stenella attenuata), spinner dolphin (Stenella longirostris), striped dolphin (Stenella coeruleoalba), short-finned pilot whale (Globicephala macrorhynchus), long-beaked common dolphin (Delphinus capensis) and Fraser's Dolphin (Lagenodelphis hosei).  

Local Threats to Cetacean

As most of the carcasses were found highly decomposed, the cause of death for only 10% of the cases could be determined.  With previous data, the Foundation concluded the 3 major causes of death:

 

Fishing net entanglement

Cetacean can be entangled and killed by fishing nets or gears abandoned in the sea.  A Chinese white dolphin was suspiciously killed by 5 abandoned fishing gears of 3.5 kg entangling its head and fluke; a young finless porpoise was drown by entanglement in fishing net.  We also found fishing hooks in their stomach, which demonstrated the adverse impacts of abandoning fishing gears in the sea on dolphins' well-being.

Trauma by boat

Some carcasses were found with bruises and serious trauma which may be resulted from boat strike.  A few finless porpoise carcasses were found without head or body, which may be caused by propeller or other forms of human activities.  Besides, we have found undigested fishes in the stomach sample, proving they still had foraging ability before death.  The death is possibly related more to trauma than sickness.

Infection

Pneumonia, parasitism and bacterial infection are common causes of death.  Although we cannot determine the cause of death for most cases, we can still conduct further analysis on the samples we took from the carcass, which could help the Foundation, the government and other research institutes to understand more on the condition of nearby waters.  OPCFHK has been collaborating with several institutes on different topics: aiding Li Ka Shing Faculty of Medicine, The University of Hong Kong to study diseases affecting stranded cetaceans; facilitating City University of Hong Kong to study recent and historic food sources, habitats and pollutant exposures of Chinese white dolphins and finless porpoises in Pearl River Estuary; and supporting Sun Yat-sen University on the research on feeding habits, genetic relationships and the age of Chinese white dolphins and finless porpoises.

 

Get Involved

 

Report stranding cases
If you encounter a stranding cetacean, regardless of whether the animal is dead or alive, please call 1823 to inform AFCD and provide your name, contact number and the following information:

  1. Date and time of discovery and the location
  2. Status of the stranded cetacean (alive, slightly or badly decomposed, etc.)
  3. Length of stranded cetacean and characteristics (e.g. any dorsal fins/ obvious rostrum, etc.)

 

Join Friends of the Foundation
Other than establishing the Cetacean Stranding Response Team, we strive to promote Asian cetacean conservation through scientific research, community education, as well as symposium and workshops. As a charitable trust, the Foundation needs your support. Ekin Cheng has joined the Friends of the Foundation, and so can you! Please support our conservation work by making a monthly or one-off donation. Join now!

Be a responsible dolphin watcher
Irresponsible or unregulated dolphin watching activities may cause disturbances and harassment to the animals in the wild. For example, some vessels would chase dolphins with high speed or intercept the course of dolphins, which increases the chance of collision or separating groups or mother and child. Please choose responsible and experienced dolphin-watching agencies and read and follow the code of conduct for dolphin watching before the tours.

AFCD's Code of Conduct for Dolphin Watching Activities

 

Cherish our ocean
To protect cetaceans, we must protect their habitat as well so that they can live in a safe and healthy environment. When you engage in coastal or water sports and activities, like boat trips, sunbathing and scuba diving, please avoid using shampoo and shower gels on the boat, to avoid untreated chemicals entering the sea and polluting the marine environment. More importantly, please do not litter on the beach and in the sea. As for fishermen and fishing enthusiasts, please dispose used fishnets and other fishery gears properly and do not abandon them in the sea.