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Environ Biol Fish (2009) 86:325–336 DOI 10.1007/s10641-009-9521-4 Effects of damming on population sustainability of Chinese sturgeon, Acipenser sinensis: evaluation of optimal conservation measures Xin Gao & Sebastien Brosse & Yongbo Chen & Sovan Lek & Jianbo Chang Received: 16 April 2008 /Accepted: 27 July 2009 /Published online: 25 August 2009 # Springer Science + Business Media B.V. 2009 Abstract The numbers of spawning sites for Chinese predation on sturgeon eggs. The simulations also sturgeon have been drastically reduced since the demonstrated that the actual restocking program is not construction of the Gezhouba Dam across the Yangtze sufficient to sustain sturgeon population as the artificial River. This dam has blocked migration of Chinese reproduction program induce the loss of more wild sturgeon to their historic spawning ground causing a mature adults that the recruitment expected by the significant decline of the Chinese sturgeon population. artificial reproduction. We conducted a VORTEX population viability analysis to estimate the sustainability of the population and to Keywords Population viability analysis . VORTEX . quantify the efficiency of current and alternative Yangtze river . Gezhouba Dam . Three Gorges Dam . conservation procedures. The model predicted the Spawning ground loss observed decline of Chinese sturgeon, resulting from the effect of the Gezhouba Dam. These simulations demonstrated the potential interest of two conservation Introduction measures: increasing spawning area and reducing Dams are known as one of the most negative human Note: Since 2006, Jianbo Chang has been transfered from impacts on river ecosystems, as they modify physical Institute of Hydrobiology, Chinese Academy of Sciences to environment and regulate flow (Allan 1996). This has Institute of Hydroecology, Ministry of Water Resources and significant consequences for fragmentation of habitats, Chinese Academy of Sciences. : : blocking migration routes, and destroying spawning X. Gao (*) Y. Chen J. Chang grounds, causing loss of biodiversity (Baxter 1977; Institute of Hydrobiology, Chinese Academy of Sciences, Dudgeon 2000), as experienced on a large variety of 7th southern road of East Lake, Wuhan, Hubei Province 430072, reservoirs all around the world (World Commission on People’s Republic of China Dams 2000). Despite the negative impact of these e-mail: [email protected] constructions, the amount of damming projects is still : increasing and dams are bigger and bigger, like the X. Gao Y. Chen – Graduate University of Chinese Academy of Sciences, Three Gorges Dam (TGD). This dam, is the largest Beijing 100039, China dam ever built, it is 193 m high and the resulting : reservoir floods over 600 km of the Yangtze course. It S. Brosse S. Lek deeply modify the Yangtze ecosystem and will EDB, UMR 5174, CNRS – 118, University of Toulouse 3, route de Narbonne, probably strongly affect both animal and vegetal 31 062 Toulouse Cedex, France communities (Wu et al. 2003). Indeed, Park et al. 326 Environ Biol Fish (2009) 86:325–336 (2003) predicted a biodiversity decline of endemic aim was therefore to estimate the status of the species fishes of the upper Yangtze River caused by the TGD. using a population viability analysis (PVA). In addition, Xie (2003) pointed out the potential PVA methods are mathematical simulations of the negative impact of TGD, combined with the Gezhouba dynamics of a population. These models integrate the Dam (located 38 km downstream from TGD) on the biological characteristics of the considered population ancient endemic fish, such as Chinese sturgeon and permit us to estimate the impact of environmental or (Acipencer sinensis), Yangtze sturgeon (A. dabryanus), human disturbances on the sustainability of the and Chinese paddlefish (Psephurus gladius). population, expressed for example as a population Biological information on Chinese paddlefish and growth rate. PVA methods are now extensively used to Yangtze sturgeon are too meager to forecast the estimate extinction risk of endangered species and sustainability of these species. On the contrary, Chinese provide effective guidelines for establishing conserva- sturgeon population biology was intensively studied tion measures (Lindenmayer and Possingham 1995; since the 1970s (Anonymous 1988). This species, due Miller and Lacy 2005). However, the precision of to its large size (more than 4 meters long and 450 kg extinction risk prediction has been the subject of some weight, Chang and Cao 1999) but also to its ancient debate (Ludwig 1999; Fieberg and Ellner 2000; history (paintings representing Chinese sturgeons made Coulson et al. 2001; Brook et al. 2002;Ellneretal. more than 2000 years ago have been found in China) is 2002;Reedetal.2002;McCarthyetal.2003). Despite considered as one of the three most emblematic fish uncertainties on the accuracy of the predictions, due species in the Yangtze River together with the Chinese to incomplete biological information, stochastic paddlefish and the Yangtze sturgeon. This is also a environmental events and the complexity of feedback vulnerable species, like most of the sturgeons, due to mechanisms, PVA are recognized as reliable methods its late maturity (Waldman and Wirgin 1997;Ludwig to estimate species sustainability (Brook et al. 2000) 2008). Prior to construction of the Gezhouba Dam, the and useful tools to manage threatened species original spawning area was located in the upstream (Mathews and Macdonald 2001; Lunney et al. 2002). part of the Yangtze River, The 16 known natural Based on previous studies on the population spawning grounds were dispersed in a 800 km length biology of the Chinese sturgeon, our aim was to reach, from upstream of Xinshi to downstream of build a population viability analysis (PVA) model to Fuling (Fig. 1)(Anonymous1988; Wei et al. 1997). estimate the sustainability of this species in the The construction of the Gezhouba Dam, in 1981, Yangtze River. Then, we used this model to quantify blocked the migration route and all the natural the efficiency of actual and alternative management spawning grounds became unavailable. Only one new procedures, leading to discuss their interest for spawning ground which has been recorded since 1981 Chinese sturgeon conservation. is located just downstream the Gezhouba Dam and represented by a 3 km long area (Fig. 1). The area of this alternative spawning site represents less than 1% Material and methods of the ancient spawning area (around 800 km), as well as the carrying capacity of this alternative spawning Chinese sturgeon site is about 10% of the ancient one, leading to a decline of the population (Wei et al. 1997;Chang Chinese sturgeon is an anadromous species, which 1999;Yietal.1999). Aiming to conserve this historically reproduced in the upstream parts of two emblematic species, the Chinese government estab- large rivers: Yangtze and Pearl rivers (Fig. 1). However, lished a series of protection measures, such as prohibit- due to human impact, the Chinese sturgeon is now ing commercial fishing since 1983, setting up an rarely found in the Pearl River, and the Yangtze River artificial propagation program (leading to release larvae is probably its last refuge (Wei et al. 1997). Spawning and juveniles since 1984), protecting actual spawning stocks were estimated as well as biological character- ground, and initiating studies on the biology and the life istics of the species were recorded since 1981 by the history of Chinese sturgeon (Fu et al. 1985; Chang and Hydrobiology Institute of the Chinese Academy of Cao 1999). However the sustainability of the last Sciences in Wuhan, the Chinese Sturgeon Institute in population of Chinese sturgeon is still unknown. Our Yichang and Yangtze River Fisheries Research Environ Biol Fish (2009) 86:325–336 327 Fig. 1 Map of China showing the location of historical and actual Chinese sturgeon (A. sinensis) spawning area. The two dams, Three-Gorges Dam (TGD) and Gezhouba Dam are indicated on the map Institute in Shashi. Since 1981, sampling has been of deterministic forces as well as demographic, done each year during the reproduction period. Fish environmental and genetic stochasticity on the dynam- spawning stock were estimated using hydroacoustic ics of a population (Lacy 2000; Miller and Lacy 2005). methods and biological characteristics (see Table 1) This program models population processes as discrete were measured by fish captures. Indeed, each year, sequential events with probabilistic outcomes. It is an mature adults were captured for artificial reproduction individual-based system that keeps track of each purposes. For more detail on the biological character- member of a population. Life history processes are istics and population structure of Chinese sturgeon, see therefore simulated by generating random numbers to Deng et al. (1985), Chang (1999)andWei(2003). determine whether each individual live or dies and to determine the reproductive output of each female PVA model and scenarios at each reproduction. Full details of VORTEX functioning are given by Lacy (1993). Population sustainability of Chinese sturgeon was The VORTEX model of Chinese sturgeon population estimated using the VORTEX (Lacy 1993)PVA dynamics was built using actual knowledge on the simulation method. The choice of VORTEX was species and these parameters are given in Table 1. guided by the ability of this model to incorporate Although the VORTEX model can be used on any available details on sturgeon life history. Moreover, this kind of

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