#population monitoring

The “Hong Kong population” of Chinese white dolphins re-defined: The latest HKU study clarifies how many dolphins there are in Hong Kong waters

The latest study by researchers at the University of Hong Kong (HKU) delivered the first-ever comprehensive population assessment of the Chinese white dolphins that inhabit Hong Kong waters, and what they found differs from the common public belief.  In fact “it differs very substantially from the estimates reported in Hong Kong for the past many years,” said Dr. Leszek Karczmarski, Associate Professor at the Swire Institute of Marine Science and School of Biological Sciences, HKU, who has instigated and supervised this study.  “Contrary to statements frequently repeated by various Hong Kong media, there is no such thing as ‘Hong Kong dolphin population’ ” he added. “The dolphins seen in Hong Kong waters represent an integral part of the Pearl River Estuary (PRE) population; they are not aware of the administrative border between Hong Kong and Mainland waters, frequently traverse these waters, and there are at least 368 dolphins that rely on Hong Kong waters as part of their home range,” said Mr. Stephen Chan, a Ph.D. student in Dr. Karczmarski's Lab and the lead author of the study that was published on Wednesday (March 29) in the peer-reviewed journal PLOS ONE.

How does it compare to the frequently advocated estimates of the apparently last remaining 60-something Hong Kong dolphins, reported by the dolphin monitoring program contracted annually by Hong Kong’s Agriculture, Fisheries and Conservation Department (AFCD)?

Dr. Karczmarski explained:  “There are several reasons for these considerable differences.  The AFCD-funded monitoring program applies a sampling technique called line transect sampling which differs from photographic mark-recapture technique applied by the HKU team.  These two techniques address a different albeit mutually relevant research question, and therefore the estimates they generate have different meanings, each with their own merits.  While the line-transect approach estimates the number of animals that are present in the area at a given time, the mark-recapture analyses estimate the overall number of animals that use Hong Kong waters during the study period.  The heart of the matter is how one interprets the results, and this is the part that has been highly problematic with the AFCD’s data over past years.”

[...]

Dr. Karczmarski emphasizes that the higher number of dolphins indicated by the HKU study “does not imply that the dolphins are better off than what the AFCD reports (just over 60 individuals) suggest.  It simply shows the critical importance of Hong Kong coastal habitats to the entire PRE dolphin population; yet another indication that these habitats, especially of west-southwest Lantau Island, should be given the highest conservation priority.”

Read more here.

केप टाउन, शिकार के पक्षी और गिद्ध शीर्ष शिकारियों और प्रमुख सफाईकर्मी दोनों के रूप में पारिस्थितिक तंत्र में महत्वपूर्ण भूमिका निभाते हैं। हालाँकि, कई अन्य पक्षी प्रजातियों की तुलना में, रैप्टर की आबादी तेजी से घट रही है। दक्षिण अफ़्रीका में शिकारी पक्षी संकट में हैं – अध्ययन में 16 वर्षों की सड़क गणना के आंकड़ों का विश्लेषण किया गया है ऐसा इसलिए है क्योंकि उन्हें रहने के लिए बड़े क्षेत्रों, कम…

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Historically Amur leopards and other wildlife in Russia have been surveyed in winter by counting tracks in the snow along an extensive series of designated routes. The track data are used to estimate relative abundance (tracks/km) and, with standardised approaches, population size. The first “snow-track leopard counts” were conducted in the 1970s by Dimitri Pikunov and Vladimir Abramov, and Pikunov and others have continued these counts to the present. These counts provide important information on the distribution and status of the entire Amur leopard population in Russia. Currently we attempt to repeat snow track counts every 3 years. The results of the most recent count in February-March 2007, financed by WWF-Russia and WCS, resulted in an estimated population of 27 to 32 leopards in SW Russia.

Traditional snow counts, while extremely useful, do not give precise information on densities of leopards, and cannot provide us other pieces of information vital to assessing viability of this subspecies, such as survival and recruitment rates. To obtain these data, we conduct camera-trap surveys. Camera trapping allows us to identify individual leopards by their unique spot patterns, and therefore we are able to monitor individual animals over many years. For instance, one leopard, captured in 1996 as part of a telemetry study, showed up in our camera traps in 2002 and 2003, but then disappeared.  Because we know that this leopard was an adult when first captured in 1996, we were able to determine that he lived a minimum of 10 years. Before WCS began camera-trapping in 2002, camera traps had never before been used for population monitoring in Russia. The method turned out to be very effective, and more than 300 photos of leopards have been taken since our first efforts in 2002.

Photo

[photo taken by a camera trap]

An important part of Amur Leopard conservation is monitoring of the population.  This allows researchers to better understand population numbers and trends.  Only through intensive monitoring can it be determined whether conservation efforts are having a positive impact.

ALTA partner WCS has been engaged in monitoring the Amur leopard population since 1997, using two approaches – a traditional Russian methodology based on tracks in the snow, and more recently, more precise estimates using camera traps.