| Identifying the life-history characteristics of fish and their response to environmental heterogeneity is the basis for the protection of fish species diversity and for the sustainable exploitation of fishery resources. In this study, using 384 speciemens collected monthly from May 2009 to April 2010, age, growth, and reproduction of Acrossocheilus fasciatus in the Huishui Stream were investigated. By comparing the life history revealed in this study with those of other populations of this species discovered by other researchers, especially that of the Puxi Stream by Yan et al. (2009, 2010), the influence of environmental stability on the life-history strategies of this species was discussed. The aims of this study were to: 1) further reveal the basic biological characteristics of this species, and 2) identify the response of the life-history strategies of A. fasciatus to the variation in habitat features along the longitudinal gradient of streams. The main results were as follows:1. Age: Based on the determined ages on the scales, the longevities of the females and females were 5 and 4 years, respectively. The relative abundance of the specimens at each aging group was 20.7% (age 1), 31.3% (age 2), 24.0% (age 3), 18.0% (age 4), and 6.0% (age 5) for the females, and 28.6% (age 1), 34.7% (age 2), 21.9% (age 3), and 14.8% (age 4) for the males, respectively. Based on the monthly changes in MIR on the scales, the annuli were formed during the period from March to May, which was believed to be associated with the relatively low water temperature in winter when fish often stopped their somatic growth.2. Growth: L–W equations for females and males were WF = 5.0×10-6L3.20(R 2 = 0.94, N = 150) and WM = 8.0×10-6L3.09 (R 2 = 0.92, N = 196), respectively. Females and males were not significantly different in the above functions (ANCOVA, F = 2.51, P > 0.05), therefore, they could be combined as W = 5.0×10-6L3.19 (R2 = 0.94, N = 346). L–R relationships for females and males were both linear and were described as follows: LF = 0.04R + 16.04 (R2 = 0.89, N = 150) and LM = 0.03R + 19.63(R 2 = 0.84, N = 196). Since the two sexes were significantly different in the above functions (ANCOVA, F = 8.96, P < 0.05), a combined L–R equation would not be acceptable for A. fasciatus. Significant difference was observed in total length back-calculated among each age for both sexes (One-way ANOVA, df = 3, F = 182.36, P < 0.001 (females); df = 2, F = 148.85, P < 0.001 (males)). In addition, females were larger than males at each age(t-test, t = 2.29, P < 0.05 (L1); t = 3.19, P < 0.01 (L2); t = 3.01, P < 0.01 (L3)), which suggested that A. fasciatus presented the sexual size dimorphism between the females and males. Parameters of von Bertalanffy growth function were estimated as: L∞= 293.70 mm, k = 0.14 year-1, t0 = -1.13 year, W∞= 372.89 g (♀); L∞= 233.40 mm, k = 0.16 year-1, t0 = -0.57year, W∞= 179.15 g (♂). Inflection point was observed in the growth curves of von Bertalanffy growth functions in total weight were aged at 6.4 (female) and 5.6 (male) years, respectively.3. Reproduction: Based on the monthly changes in GSI, the developmental process of eggs and gonads, the breeding activities of A. fasciatus were carried out during April through August. Females and males both got 50% maturity at age 3, with total length of 105.27 mm and 112.11 mm, respectively. While the minimal maturity individuals were at age 2 for both sexes, with total length of 69.63 mm (female) and 67.50 mm (male) respectively. Absolute fecundity, 858±642 eggs, significantly increased following with the increase in age (One-way ANOVA, F = 21.34, P < 0.001). But relative fecundity, 30.80±20.31 eggs/g, was not significantly different among each age group (One-way ANOVA, F = 0.74, P > 0.05). Under light microscope, the developmental process of spermary and ovaries were revealed, and the morphological structures were systemically described.Compared with the life history of A. fasciatus in the Puxi Stream revealed by Yan et al. (2009, 2010), this species presented some marked changes in its life-history strategy in the Huishui Stream, involving longer life-span, larger body size, faster growth, later maturity, and lower reproductive investment. These life-history changes could be a plasticity or adaptation to their surrounding environment of A. fasciatus in the Huishui Stream. |
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