Abstract:Elongate Loach (Leptobotia elongate) is endemic to the upper Yangtze River. It has been threatened by overfishing and dam construction, and evaluated as being endangered in China Species Red List. To understand its population dynamics after the Three Gorges Reservoir was impounded, the catch and time series length-frequency data were used to estimate growth and mortality parameters, population abundance and resources utilization of Elongate Loach based on surveys in the Jiangjin section of the upper Yangtze River conducted in 2007﹣2009 (Fig. 1). Elongate Loach ranged from 76 to 480 mm in length and 5 to 2002 g in weight, with an average length of 158.7 ± 54.8 mm and an average weight of 72.4 ± 148.8 g (n = 277). The length group of 90﹣210 mm dominated the catches (77.9% of the total number) (Fig. 2). The length (L, mm)-weight (W, g) relationship of Elongate Loach was well-fit with a power function, W = 7.28 × 10﹣6 L3.09 (R2 = 0.95, P < 0.01, n = 277) (Fig. 3). Asymptotic length (L∞) and growth constant (k) were estimated using length frequency data as 555 mm and 0.17/a, respectively. Natural mortality was estimated as 0.37 using the empirical formula proposed by Pauly. The total mortality was estimated using a length-converted catch curve analysis as 1.23 (Table 1). The exploitation rate observed in the Jiangjin section was 0.70, higher than the estimated maximum exploitation rate (0.43), which indicated that it was overfished for Elongate Loach (Fig. 4). Population abundance of Elongate Loach in the Jiangjin section estimated by length-structured virtual population analysis was 2 544 ind/km (0.75 t/km) in 2007, 2 405 ind/km (0.42 t/km) in 2008, and 7 245 ind/km (1.63 t/km) in 2009, respectively, with an average of 4 065 ind/km (0.93 t/km) (Fig. 5). Compared with the earlier studies (Table 2), a new maximum length (480 mm) of Elongate Loach was recorded; the estimated total mortality and exploitation rate of Elongate Loach in this study were higher, which was likely caused by the higher fishing effort in the Jiangjin section. Long-term population dynamics monitoring, closed fishing, and artificial enhancement and releasing were suggested to improve the resources.