Life-history Characteristics Of Two Species Of Sarcocheilichthys In The Qingyi Stream

Identifying the life history （e.g., age, growth, and reproduction） of fishes andrevealing their response to environmental conditions are basic for the scientificconservation of fish species diversity and the sustainable use of fishery resources. Inthis study, the life history of two species of Sarcocheilichthys fishes （i.e., S.nigripinnis and S. parvus） were examined using the specimens monthly collected inthe Qingyi Stream from May2009to April2010. The charatersitics in age, growth,and reproduction of the two species were revealed and how these charatersticsrelated to local and regional environmental conditions is analyzed. Our results willnot only pile the information on the basic biological traits for the twoSarcocheilichthys fishes, but also will bring forward some scientific basis for theconservation and management of the fishery resources in the Qingyi Stream. Ourmain results were as follows:1. Age Scales were used for age determination for S. nigripinnis and S.parvus, respectively. The annuli on the scales of S. nigripinnis was easily identifiedbecause of their characteristics of spacing, incising, and spacing-incising. The resultof the monthly changes in marginal increment ratio on scales showed that theirannuli were formed during March. Both female and male S. nigripinnis had four agegroups. The relative abundance of each age group was31.0%（age1）,47.3%（age2）,17.8%（age3）, and3.9%（age4） for the females and23.8%（age1）,51.1%（age2）,21.5%（age3）, and3.6%（age4） for the males, respectively. The annuli on thescales of S. parvus showed the characteristic of incising, which was formed duringMarch based on their monthly changes in marginal increment ratio. Female andmale S. parvus had five and four age groups, respectively. The relative abundance ofeach age groups was24.2%（age1）,43.7%（age2）,30.1%（age3）,1.0%（age4）,and1.0%（age5） for the females and29.1%（age1）,54.6%（age2）,13.7%（age3）,and2.6%（age4） for the males, respectively.2. Growth For S. nigripinnis in the Qingyi Stream, their L–W equationswere W=2×10^–5L^2.89（R²=0.87, N=129） for females and W=3×10^–5L^2.83（R²=0.79, N=223） for males, respectively. They could be combined as W=2×10^–5L^2.85（R²=0.82, N=352） because no significant difference was observed between sexes（ANCOVA, F=1.70, P>0.05）. Their L–R equations were L_♀=0.02R+26.35（R²=0.56, N=129） and L_♂=0.02R+34.94（R²=0.60, N=223）. They could also becombined as L=0.02R+32.36（R²=0.58, N=352） because no significantdifference was observed between sexes （ANCOVA, F=0.50, P>0.05）. The vonBertalanffy growth functions were Lt=238.23(1–e^{-0.09（t+3.39）} for females and Lt=166.01(1–e^{-0.16（t+2.83）}) for males, respectively; and their combined function was Lt=172.26(1–e^{-0.14（t+3.53）}). The age at inflection point occurring at the weight-growthcurves was8.40years for females,3.67years for males, and3.95years whencombining both sexes, respectively. For S. parvus in the Qingyi Stream, their L–Wequations were W=3×10^–5L^2.80（R²=0.90, N=103） for females and W=6×10^–5L^2.65（R²=0.82, N=117） for males, respectively. They could be combined asW=4×10^–5L^2.71（R²=0.85, N=220） because no significant difference wasobserved between sexes （ANCOVA, F=0.04, P>0.05）. Their L–R equations wereL=0.02R+54.04（R²=0.11, N=103） for females and L=0.005R+76.40（R²=0.01, N=117） for males, respectively. They could also be combined as L=0.004R+32.36（R²=0.01, N=220） because no significant difference was observedbetween sexes （ANCOVA, F=1.22, P>0.05）. The von Bertalanffy growthfunctions were L_t=113.80(1–e^{-0.3（t+0.27）}) for females and L_t=166.01(1–e^{-0.13（t+2.25）}for males, with their combined function being Lt=115.16(1–e^{-0.24（t+1.29）}). The ageat inflection point occurring at the weight-growth curves was2.67years for females,5.25years for males, and2.86years when combining both sexes, respectively.3. Reproduction Sex ratio （female: male） was0.58:1for S. nigripinnis,significantly different from1:1（χ²=12.78，P <0.001）, and0.88:1for S. parvus,not significantly different from1:1（χ²=0.43，P>0.05）. Based on the monthlychanges in gonado-somatic index, S. nigripinnis spawned during the period fromApril to July and S. parvus was from March to August. Fifty percentages ofindividual S. nigripinnis got the first sexual maturity at age2, with the total lengthof94.67mm for females and103.00mm for males, respectively. For S. parvus, theygot their50%maturity at age2too, with the total length of80.67mm for femalesand84.79mm for males, respectively. The absolute fecundities were411±294eggsfor S. nigripinnis and391±147eggs for S. parvus. In addition, their relativefecundities were72.53±42.85eggs/g for S. nigripinnis and141.85±21.82eggs/g for S. parvus, respectively. The egg diameters did not significantly differ across theovaries for female S. nigripinnis and S. parvus collected during their spawningseasons, respectively （One-way ANOVA, F=0.12, P>0.05, S. nigripinnis; F=1.15, P>0.05, S. parvus）. However, for each ovary of the two species, two obviouspeaks were observed in the frequency distribution of egg diameter. Egg diametersranged from1200μm to2600μm for the first peak and from2600μm to4000μmfor the second peak for S. nigripinnis; and from850μm to1700μm for the firstpeak and from1700μm to2450μm for the second peak for S. parvus,respectively.This suggested that both S. nigripinnis and S. parvus in the QingyiStream were batch spawners.