The number of finless porpoises washing up dead or becoming stranded on Hong Kong’s shores has increased constantly during the past decades, as OceanAsia reports. The average of 11 stranded animals per year had increased to 24 in the last decade with an all-time high of 43 stranded porpoises in 2019. Alarmingly, the mortality numbers are likely much higher as the Marine Mammal Stranding program only counts animals that are found.
An annual mortality rate of more than four to five per cent is considered as unsustainable for the porpoise population. However, the actual impact of the increasing death toll cannot be understood without a clear population estimate. Yet, the population’s actual number is still elusive as the last comprehensive study of the population was carried out 18 years ago and there is no way of knowing whether the estimated population of 220 animals is still reflective of the current numbers.
The insight is further limited by a lack of clearly identified causes of death. Deaths could only be clearly related to a cause in ten per cent of the stranded cases, with the rest either being too decomposed for examination or the reports simply lacking in detail. The team of OceanAsia therefore calls for consistent and detailed stranding reports that are comparable.
As long-term observation suggest bycatch, entanglement, ship strikes and pollution as the main reasons for the animals’ deaths, OceanAsia is recommending to improve fishery practices. Puzzlingly, the official entanglement tally in Hong Kong’s inshore fisheries is unusually low. OceanAsia assumes that this might be due to the Wild Animal Protection Ordinance requirements in which fishers have to prove that they caught the porpoise by accident – a very difficult task which might deter them from reporting entanglements. Amending the law is listed as a first step to improve the reporting, as well as fitting the vessels with CCTV cameras that would record entanglements with minimal disruption.
Besides calling for the establishment of a marine park, OceanAsia also points out the importance of a comprehensive finless porpoise survey. The animals have proven elusive for years, with the first footage of finless porpoises in Hong Kong only being released recently. Due to their cryptic behavior, the shy animals cannot be observed efficiently in the usual boat survey. However, the marine biologist Dr. Lindsay Porter hopes that new tools such as drones and acoustic devices could aid them in their survey. She is worried that while “we slowly learn more of this population’s habits and lifestyle, we will be too late to save them, as the number of dead porpoise is increasing dramatically every year.” But with the footage released, more people might be willing to take efforts in protecting the finless porpoise population “before it is too late.”
Articles on the report can be found here: https://chinadialogueocean.net/14087-why-are-porpoise-deaths-on-the-rise-in-hong-kong/
And here, including the first footage of the finless porpoise in Hongkong: http://oceansasia.org/finless -porpoise-hongkong/
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