by Zackery Good, RJD Intern
Imagine you are a Yangtze finless porpoise, swimming through the Yangtze River in China (Figure 1). As you go about your daily business of finding food, you must navigate your way through heavy boat traffic, fishing gear, and water construction projects. The water you swim in is likely polluted and filled with debris. However, there are some relatively safe areas in which you can seek refuge from these dangers. The usefulness of these safe areas is evaluated in Zhao et al.’s 2013 publication Distribution patterns of Yangtze finless porpoises in the Yangtze River: implications for reserve management.
The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is a freshwater subspecies of the narrow-ridged finless porpoise endemic to the Yangtze River as well as two lakes connected to the river, Dongting Lake and Poyang Lake (Gao & Zhou 1995, Chen et al. 2010). The subspecies is now considered to meet the IUCN Red List criteria for critically endangered (Mei et al. 2012), with the population declining from approximately 2550 animals in the early 1990s (Zhang et al. 1993) to approximately 1200 animals in 2006 (Zhao et al. 2008). The recent extinction of the Yangtze River dolphin (Lipotes vexillifer) underscores the importance and immediacy of protecting this subspecies from further decline (Figure 2).
Currently, there are five cetacean reserves in the Yangtze River: three national-level reserves at Shishou, Honghu, and Tongling; one provincial reserve at Zhenjiang; and one municipal reserve at Anqing. The three different types of reserves receive different levels of funding and attention. National reserves receive the highest level of funding and attention.
The three national-level reserves were originally set up to conserve the Yangtze River dolphin, but are still in effect to protect the Yangtze finless porpoise (Zhao et al. 2013). The location of these reserves as well as the locations of major cities along the Yangtze River can be seen in Figure 3.
Zhao et al. conducted survey work from November 6 to December 13, 2006 to estimate the abundance and distribution of the Yangtze finless porpoise in the Yangtze River. Zhao et al. chose these dates because the porpoises tend to concentrate in the narrow river channel during the low-water season, which increases the chance of detecting the porpoises (Zhao et al.2013).
Two vessels conducted transect surveys. One vessel in “closing mode” could approach groups of porpoises to further confirm group size, while the other vessel in “passing mode” did not have this option of approaching groups. The porpoises were detected by both visual observation and acoustic detection by towed acoustic arrays similar to SONAR (Zhao et al. 2013).
The number of porpoises detected did not vary significantly between the two vessels, so the visual data was pooled together for analysis. The acoustic data was incomplete for both vessels, so it was also combined for analysis. Since both methods of observation will miss animals, Zhao et al. (2013) combined these data and analyzed them to get the combined encounter rate (Figure 4). The combined encounter rate for each section of the survey transects were then ranked to indicate which areas are highest priority for conservation of the Yangtze finless porpoise.
From the combined encounter rates, Zhao et al. (2013) were able to determine whether or not the current reserve system in the Yangtze River is effective for conserving the Yangtze finless porpoise. They found that the current reserve area does not fully cover the area of highest porpoise abundance. Therefore, they make four recommendations to improve the reserve system assuming that the current commitment of resources is all that is possible.
Zhao et al. (2013) first recommend modifying the Shishou reserve to include a 50 km area upstream with high porpoise density. They also recommend strengthening monitoring and management at the Honghu reserve since it contains the highest porpoise density upstream of Wuhan (Figure 3). Their third recommendation is to dissolve the reserves at Honghu and Anqing to create a new reserve covering the area of highest porpoise density located between the two. Fourthly, Zhao et al. (2013) recommend moving the Tongling and Zhenjiang reserve areas to include two areas of high porpoise density located between the two.
Zhao et al. (2013) make excellent recommendations for the conservation of the Yangtze finless porpoise without a commitment of resources greater than those available now. However, it is important to note that, “effective porpoise conservation […] will require knowing whether porpoises move out of or between reserves” (Zhao et al. 2013) as well as whether porpoises move seasonally. These kinds of data will allow for more complete protection of the most important areas for the Yangtze finless porpoise.
However, Zhao et al. (2013) point out that “it is unfortunately unrealistic to expect that all threatening anthropogenic activities within the Yangtze system will be regulated or prohibited even in cetacean reserves.” In my opinion this is simply unacceptable. Considering the tragedy of the Yangtze River dolphin it would be outrageous for us to allow another preventable tragedy to occur.
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