Last updated June 2021
Taiwanese white dolphin (Sousa chinensis taiwanensis)
Background and Status
Although white dolphins had been observed by local fishers for some time, the Taiwanese white dolphin (Sousa chinensis taiwanensis) was not scientifically documented until 2002 (Wang et al. 2004), and formally described as a subspecies of the Indo-Pacific humpback dolphin (Sousa chinensis) in 2015 (Wang et al. 2015). The primary distribution of this subspecies is a narrow band of waters extending from shore to about three kilometers from the coast of western Taiwan (= eastern Taiwan Strait) (Wang et al., 2016). Taiwanese white dolphins are found in highest densities in and adjacent to major estuaries and in waters 5 to 8 m deep; they have been seen in waters less than 1 m deep, but are rarely seen in waters deeper than 20 m, except in shipping channels that have been artificially deepened (Dares et al., 2014). Recent video evidence of Taiwanese white dolphins in waters about 50 km north of their known distributional limit confirmed earlier suspicions that they also inhabit waters farther north of their confirmed habitat and in the suitable habitat identified by Ross et al. (2010).
Mark-recapture analysis of photo-identification data collected from 2007 to 2010 resulted in the highest annual total population abundance estimate of 74 in 2010 with a CV of 4% (95% CI=68–80) (Wang et al., 2012). Annual abundance estimates for 2011, 2012 and 2013, using the same photo-identification mark-recapture method, varied from 71 (2011) to 67 (2012 and 2013), with CVs varying from 3 to 4% (J.Y. Wang, unpublished data), which suggests the population was slowly declining. Initial results from a demographic analysis using a Bayesian mark-recapture model that accommodates more realistic scenarios (than the model used by Wang et al., 2012) also showed the population to be declining from 2010 to 2018 (C. Araújo-Wang, unpublished data).
Two independent Population Viability Analyses simulating population dynamics under different impact scenarios including bycatch mortality and habitat loss/degradation, also indicated the population was highly likely on a declining trajectory (Araújo et al., 2014; Huang et al., 2014). With no more than 75 individuals (and fewer than 50 mature individuals) remaining in this declining population and no reductions in the existing known threats (while new threats are being added), the subspecies has long been red-listed as Critically Endangered (Reeves et al., 2008; Wang et al., 2017; Wang and Araújo-Wang 2018).
Threats to the Taiwanese White Dolphin
In 2007 a panel of experts thoroughly reviewed a long list of potential threats and identified five main categories of existing human-caused threats facing Taiwanese white dolphins (Wang et al., 2007). These include:
Fishing is the most direct and immediate threat to these dolphins (Ross et al., 2010; Dungan et al., 2011; Slooten et al., 2013; Araújo et al., 2014; Wang and Araújo-Wang 2017; Wang et al., 2007a,b; 2017). Almost 60% of the Taiwanese white dolphins bear evidence of serious injuries due to human activities (Wang et al., 2017) and more than 31% of the animals have been photographed carrying fishing gear or with injuries that were likely caused by fishing gear (Slooten et al., 2013; Wang and Araújo-Wang 2017). Gill and trammel nets are the predominant gear involved, with thousands of such nets being used throughout dolphin habitat (Dungan et al., 2011; Slooten et al., 2013).
Habitat degradation and loss due to development
The west coast of Taiwan has high human densities and was rapidly industrialised over the past century (Williams and Chang, 2008). Between just 1995 and 2007, 20% of white dolphin habitat was lost as the coastline was altered by flood and erosion control measures, fishing ports, industrial development, power plants and other human activities. In response to the demand for agricultural and residential land, multi-purpose industrial areas were built over coastal waters (i.e. through terraforming, which is better known as “land reclamation”), directly reducing and degrading dolphin habitat (Wang et al., 2004b, 2007b).
Reduction of freshwater flow into estuaries
Most major rivers along the west coast of Taiwan have been diverted in the upstream sections to provide water for agriculture, industry, power generation and household use (Taiwan Water Resources Agency, 2015; Wang et al., 2004b; Williams and Chang, 2008). Such reductions in freshwater flow to major estuaries likely affect Taiwanese white dolphins through decline in prey resources.
Chemical pollutants (air, water, soil)
The coast bordering Taiwanese white dolphin habitat has a wide variety of industrial complexes, including petroleum oil storage facilities, petrochemical plants, refineries, fueling stations and thermal (coal) power plants (Wang et al., 2007b). Such facilities discharge pollutants into the local air, water and soil. The results of a study that modelled the burden of polychlorinated biphenyls (PCBs) in Taiwanese white dolphins showed that a large proportion of the dolphins have burdens above the PCB threshold for effects on immune function in other marine mammals (Riehl, 2012). Possible suppression of the immune system in these dolphins is of great concern given the many other threats (Riehl, 2012). Yang et al. (2013) reported at least 37% of the Taiwanese white dolphins exhibited unusual skin lesions and conditions, which suggests that they may already be showing signs of immune deficiency. Furthermore, an unusually large proportion of the dolphins have severe spinal anomalies (lordosis and scoliosis) (Weir and Wang, 2016).
Underwater noise has been steadily increasing over the last few decades, which has led to growing concerns for marine life throughout the world (e.g., see Cato et al., 2004; Nowacek et al., 2007; Hildebrand 2009; McCauley et al., 2017). This is particularly true for the Taiwanese white dolphin, which is subjected to many human-generated sounds in the busy waters off western Taiwan, including those from vessels, military exercises, seismic research and percussive pile driving (Wang et al. 2007; Ross et al., 2010; Dungan et al. 2011). Some of these sources produce sounds that are extremely loud and potentially injurious (Würsig et al., 2000). However, a study on the underwater soundscape at two sites within Taiwanese white dolphins’ habitat suggested that even though shipping intensity along western Taiwan is relatively high, the noise produced by large vessels at these two sites did not appear to overlap much with the dolphins’ whistle frequency range up to 6 kHz and vessels that generated higher frequency noise did not contribute much to the soundscape (Guan et al., 2015).
Other Developments Threatening the Taiwanese white dolphin
Probably the most significant development is the so called “1000 turbines” project, which proposes over 1000 new wind turbines (approximately 20 Gigawatts) to be installed in the shallow coastal waters of western Taiwan before 2035. The aim of this massive wind-farm complex (one of the largest in the world, led and funded mainly by European developers, governments and financial institutions) is to reduce Taiwan’s dependence on fossil fuels. Ironically, the project is sited in and near the habitat of one of the world’s most endangered cetacean populations (Brownell et al., 2019).
The development brings substantial construction noise, increased boat traffic associated with erecting and servicing turbines, disturbance to local fishing activities and further reduces the already restricted Taiwanese white dolphin habitat. The vast extent of the windfarms will also likely result in increased gillnet fishing in the dolphins’ nearshore habitat as the fishermen are displaced inshore by wind turbines sited in the offshore fishing grounds. This will magnify existing threats from fisheries and will likely accelerate the population’s decline (see Ross et al., 2018; Taylor et al., 2019). As of July 2021, even the meager legal environmental mitigation obligations have not been met by the developers and government agencies have shown little will and capacity for enforcement.
Plans to expand existing petrochemical facilities and power plants continue unabated and with little to no consideration for the dolphins. This is similar to the planning for further major water diversion projects, new power plants, and commercial port development. Taiwan’s energy goals include converting much of its coal-fueled energy generation to liquified natural gas (LNG). This means expanding existing plants as well as embarking on two major new projects:
(1) expanding Taichung Harbor to accommodate a new LNG plant and receiving terminal, which will affect the already greatly reduced size of the Dadu Estuary where the highest densities of Taiwanese white dolphins have been observed (Dares et al., 2017), and
(2) constructing a massive LNG receiving station (projected to supply 6-8% of Taiwan’s energy needs) in coastal waters of Taoyuan County, next to a unique and sensitive algal reef where Taiwanese white dolphins were recently observed.
Taiwanese White Dolphin Advisory Panel
In December 2007 at the Society for Marine Mammalogy’s biennial conference in Cape Town an international working group was formed to identify, characterize, and help address threats to Taiwanese white dolphins. A decade later at the biennial conference in Halifax, the Taiwanese White Dolphin Advisory Panel (TWDAP) was established, comprised of around 20 international and Taiwanese marine science and conservation experts. The TWDAP has convened several scientific workshops, met with various Taiwanese government agencies, supported and advised Taiwanese conservation groups, and reported on the state of Taiwanese white dolphins to other organizations and at international meetings.
Although the government has given occasional signs of interest and concern by making decisions that should have benefited the dolphins, any such benefits have been forfeited or offset in some way. Examples include:
Taiwanese White Dolphin Recovery Plan
In August 2019, Wild at Heart Legal Defense Association (Wild at Heart) and Matsu Fish Conservation Union (MCFU), both based in Taiwan, organized and sponsored an international workshop for the purpose of producing a recovery plan to identify actions needed to stop the decline of Taiwanese white dolphins and promote their recovery. Sixteen participants, including experts in science and conservation policy and representatives of Taiwanese NGOs and the OCA, gathered at the University of Western Ontario in London, Ontario, Canada for a 4-day workshop to produce a science-based recovery plan.
Immediate Actions Recommended
Available knowledge was considered to be sufficient to justify moving forward with six immediate actions:
The Recovery Plan clearly identified banning of gill and trammel nets as the single most urgently needed action. If effectively enforced, such a ban would be highly effective in helping to halt the dolphins’ decline. The workshop proposed a solution: Companies and financial institutions involved in ongoing offshore windfarm development should help finance government programs to eliminate gill and trammel nets from dolphin habitat.
This was seen as a ‘win-win-win’ solution given that the developers are already disbursing massive sums to ‘compensate’ fishers and fishing communities but all on an ad hoc basis and with no requirement to stop fishing with gillnets. Such compensation contributes nothing to an overall reduction in the cumulative impacts on dolphins. Much better collaboration and coordination between government agencies and developers is needed to fairly compensate fishers to stop using gillnets.
The Recovery Plan is available here.
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