| The paper deals with the biology of Rhinogobio cylindricus Günther.From April 2000 to May 2001,551 specimens of R. cylindricus Gunther were collected from Mudong town, Chongqing city, which is located in the mid-up stream of the Changjiang(Yangtze) River.551 specimens were aged by scale. It is showed that the new annuli in the scale of R. cylindricus are mostly formed yearly from March to April.The analysis of composition of the catches shows that those of dominant age groups from 2 to 3 years, body-length groups from 160 to 209 mm and body-weight groups from 40 to 99 gram constitute 93. 1%,76.4% and 83.8% respectively.With electronic computer, the correlative formula and the most fitted Von-Bertalanffy equation, for "radius" of the scale(R,mm)and body-length(L,mm), body-weight(W~g) are selected as follows:(1) L49.6l6R+56.628(r=0.7869n551)(2) W=0.0262L27316(r=0.9557n551) (L,cm)(3) L~=33 .5876 ( 1-e021171~'~'42249~)(L,cm)(4)W13 86.273 1(1 —e021 171(t+1.42249))3L..33.5876W..386.2731k0.21171to-l.42249The indices of growth and the amount of products on yearly increments of the length and weight depending on the growth equation indicate that,the faster growing period of the length and weight is from 2 to 5 years.The instantaneous growth rate equations depending on the growth equation are as follows:(5)dL/dt33 .5876e -O.2117I(t+I.42249)(6)dW/dt=386.273 1 e02' I7I(t.~~1.42249)( 1—e02' 171(t+1.42249) )I.73~6(7) d2L/dt2 -1 .50502eO2ll7I(t~l42249)30(8)d2VVIdt2~= 1055. 144e 021171(t*142249) (1—e'0 21 171(t-t1.42249) )0 7316(27316 e .021 l71(t~i.42249)l)The instananeous rate growth equation of the weight have an inflexion:tr3.324 yearsLr=212.916mmWr386.2731gThe fullness is different at different seasons and ages, which is related to feeding and reproductive action.According to the analysis of the food in the intestine, K cylindricus feeds mainly on shells and larvae of water insects.The absolute fecundity of R. cy/indricus varies from 2755 to 54375,with the average of 12446.The relative fecundity based on body-weight varies from 25.1 to 271 .9,with the average of 144.4. The relative fecundity based on body-length varies from 13.7 to 21 l.6,with the average of 50.1.R. cy/indricus reproduces yearly from May to June. The male fish can be differed from the female one with the pearl organ.The ratio of the whole population between the female and the male is 1 .056,while that of the breeding population is 0.72, The youngest maturity age of the male is 2 years old with a body-length of 154 mm and a body-weight of 54 gram, while that of the female is 2 years old with 168 mm and 73 gram respectively.The developing of sexual gland of male and female can be divided into six phases.Based on our observations, we discussed the following questions: the characteristic of the annuli, the difference of the growth, the life time growth, the changes of the yolk nucleus, the structure and physiological characteristic of the vitelline membrane, the nucleoli extended and the resource utilization of R. cy/indricus, etc. |
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