| Triplophysa yarkandensis (Day) belongs to subgenus Hedinichthys, genus Triplophysa, subfamily Nemachilinae, family Cobitidae, order Cypriniformes. T. Yarkandensis widely distribute in Tarim River, which is the species with faster growth and larger size.940T. Yarkandensis were collected in Alar section of the Tarim River from July2010to December2011. The aquatic organisms in Tarim River were also investigated. The water habits, population growth, reproductive biology, population dynamic, resource accessment, were analyzed to study the population ecology of T. Yarkandensis. The results are as follows:1. Water habits:The Tarim River is a seasonal river with changed depth, and it had sand beds with low water transparency. The watercourse also changes with time.12species,3phyla of phytoplankton (1species of Diatom,7species of Chlorella,4species of Cyanophytes) were observed in this investigation. Little protozoans, no Rotifers, cladocerans and copepods were found. The most item in zoobenthos was Chironomida larvae. The biomass of phytoplankton was0.553mg/L, it was speculated that the productivity of silver carp and bighead carp would be8.418kg/hm2.16species of fish, belonging to13genera,8families,3orders were collected.2. Age estimation:Otolith was chosen as main structure for age estimation of T. Yarkandensis, and vertebra and opercular bone were chosen as supporting structures. Annuli formed between March and May once a year in all of the three calcified structures. Annuli on the otoliths were clearer than others. Of940samples,891were successfully aged. The estimated age range varied from1to10, the majority of age compositon concentrated between2.5～6.5yr. The majority of females concentrated in4～6yr, males concentrated in5yr.3. Population growth:The standard length (L) of T. Yarkandensis ranged30.0～195.0mm, weight (W) ranged3.40-114.OOg. Length composition mainly concentrated in75.0～125.0mm, accounting for51.81%of the groups, especially for the individuals below100mm standard length. Length-weight relationship was described as W=0.0355×L2.5916(R2=0.8736, n=940). The von Bertalanffy growth function were:Lt=23.66(1-e-0.0900(t+0.1831)),Wt=129.16(1-e-0.0900(t+0.1831))2.5916(1-e-0.1026(t+1.0458)),Wt=68.08(1-e-0.1026(t+1.0458))2.5916for males.The inflexion point for the growth of female and male were10.39and8.24years, respectively. 4. Reproductive biology:The female and male ratio was0.85:1, which differed significantly from1:1. Standard length, weight and age of the females at minimum maturity were82.0mm,7.40g and3years, respectively, and those of the males were65.0mm,3.40g and2years, respectively. According to the size distribution of oocytes, T. Yarkandensis were single spawners.88females with Ⅳ～Ⅴ stages, ranging30.0～195.0mm standard length and3.59～114.04g weight, were chosen to estimate the fecundity. The fecundity ranged1101～56320(9944±5487) eggs, and the relative fecundity ranged824～1140(982±158)/g body weight. The fecundity of T. Yarkandensis population (Fp) was4034612eggs.5. Populatin dynamic:The total mortality was0.298/year for females and0.400/year for males in Alar section of the Tarim River. Natural mortality was0.257/year for females and0.286/year for males, and fishing mortality was0.041/year for females and0.114/year for males. Exploitation level of T. Yarkandensis was0.138/year for females and0.285/year for males, showing that the population was not developmented reasonably. The life history pattern of T. Yarkandensis belonged to r-selection. The maximum sustainable yield was0.000122, the fishing effort was0.00685. Therefore the fisheries administration and management departments should developed a certain degree of protection system to protect the elderly individual in order to protect the resources of T. Yarkandensis. |
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