Title;
Long-term population and distribution dynamics of an endangered Irrawaddy dolphin population in Balikpapan Bay, Indonesia in response to coastal development
Authors:
Danielle Kreb, Stanislav Lhota, Lindsay Porter, Alexandra Redman, Imelda Susanti, Milan Lazecky
Citation: Kreb D, Lhota S, Porter L, Redman A, Susanti I and Lazecky M (2020) Long-Term Population and Distribution Dynamics of an Endangered Irrawaddy Dolphin Population in Balikpapan Bay, Indonesia in Response to Coastal Development.
Front. Mar. Sci. 7: 533197.doi:10.3389/fmars.2020.533197.
Summary:
Worldwide, cetaceans are
impacted by human activities, and those populations that occur in
shallow-nearshore habitats are particularly vulnerable. We present the results of
the first long-term study on the responses of a coastal population of endangered Irrawaddy
dolphins to widespread habitat changes. We particularly investigated their responses
in terms of distribution and abundance. Boat-based, line-transect surveys were
conducted during 12 discrete survey periods in 7 survey years spanning a
15-year period (totaling 78 days and 4,630 km of effort) in
Balikpapan Bay, East Kalimantan, Indonesia. Irrawaddy dolphins were sighted on
136 occasions. Through DISTANCE analysis, a decrease in population density in
the inner Bay area was observed from 0.45 dolphins/km in 2000–2001 (CV = 24%) to 0.34 and 0.32 dolphins/km in 2008 and
2015 (CV = 31%
and 25%). A shift in distribution was noted between the periods 2000– 2002 and 2008–2015 with significantly lower occurrence in
the lower Bay segment
compared to upper
Bay segments. No sightings were made in the outer Bay area in later years, which coincided with increased shipping traffic in
these areas. A peak in stranding
events in 2016
and 2018 followed extremely high phenol levels within Bay waters in 2015 and a
large-scale oil spill in 2018. The mean annual mortality rates of 0.67
Irrawaddy dolphins/year is unsustainable based on the lower potential
biological removal (PBR) values for best abundance estimates of 2015 (N distance
= 45 and N = 73). Other threats to local dolphins include unsustainable fishing,
underwater noise caused by construction, particularly piling activities. The
research helped to identify Balikpapan Bay as an Important Marine Mammal Area
by the IUCN MMPA Taskforce. Serious concerns remain for the concrete plans to
move Indonesia’s capital city to the area north of the Bay, in terms of
increased shipping traffic and harbor construction in the upper Bay segments
that represent primary dolphin habitat. We recommend that protected areas be
assigned for marine mammals and artisanal fisheries and shipping traffic and
piling activities be excluded from these areas. We also recommend a legislated
requirement of a mitigation protocol compulsory for piling and seismic
activities within Indonesia.
Keywords: Irrawaddy dolphin, abundance, distribution,
photo-identification, conservation management, oil spill, Balikpapan Bay,
Indonesia
To view the online publication or download a PDF (open access), please click here:
http://journal.frontiersin.org/article/10.3389/fmars.2020.533197/full?&utm_source=Email_to_authors_&utm_medium=Email&utm_content=T1_11.5e1_author&utm_campaign=Email_publication&field=&journalName=Frontiers_in_Marine_Science&id=533197
Thanks for your attention,
KInd regards,
--------------------------
Danielle Kreb (Ph.D.)
Scientific Program Leader Yayasan Konservasi RASI (Rare Aquatic Species of Indonesia)
Honorary Lecturer Laboratory of Hydro-Oceanography, Faculty of Fisheries, Mulawarman University,
Samarinda Kalimantan Timur, Indonesia
Tel/ fax: + 62.541.4113510
Mobile: 081346489515
instagram: yayasan_rasi
Facebook group/page: Rare Aquatic Species of Indonesia
Member of IUCN/SSC Cetacean Specialist Group
“To the dolphin alone, nature has given that which the best
philosophers seek: friendship for no advantage. Though it has no
need of help from any man, it is a genial friend to all and has helped mankind.”
–Plutarch