Abstract:The First Fishery Production Squad of the He-luo Commune,in the culture of edible fishes,has for quite some time been making full use of its rich reso- urces of natural food and plentiful clear-water supply,and paying particular attention to"stocking fish","mixed culture","dense stocking"and"good ma- nagement",and got steady high yield.The important experiences are as foll- ows: 1.Individual fishes at the time of stocking should be of pretty large sizes,e.g.,grass carps of 0.8～1.7 catty/tail and black carps of 1～3 catty/tail. 2.Taking into consideration the food available,ponds are chiefly stocked with grass and black carps.Silver and bighead carps,common carps,breams and crucian carps are to be mixed with the former. 3.Plentiful food,deep water,suitable pond size,mixed culture of some species of fish have made dense stocking possible,which contribute much to the increased yield. 4.Steady high yield can never be materialized without subjective initia- tive and enthusiasm.Careful stocking and good management are also keys to steady high yield. (1)early cleaning and early repairing of ponds benefit the growth of fish. (2)in feeding attention should be directed to"evenness,quality and sufficiency",i.e.,fishes are fed according to weather and climate,water colour and fish appetite. (3)sufficient feeding and suitable dense stocking may cause lack of oxygen and adversely affect growth or even cause death of fish.Through controlling of feeding,adding of fresh water to improve water quality and water colour, suffocation can be prevented. Some problems remain to be solved.(1)The present 4-year culture-cycle for black and grass carps,and 3-year culture-cycle for breams have to be shortened.(2)The gaps in yield between one pond and another have to be narrowed down.(3)The use of fertilizers and the planting of food crops should be promoted.(4)Technique in the culture of yearlings and 2-year olds should be improved.(5)The marketing size of silver and bighead carps should be increased.(6)Disease and high mortality of yearlings and the 2-year-olds of the grass and black carps are to be prevented.

Abstract:Human chorionic gonodotrophin(HCG)has been used in the study of artificial spawning of fishes by many authors 1937;Sneed and Clemens,1959;Tchou and Wang,1962;Anwand,1963;etc). Ovulation and maturation in vivo has also been successfully achieved in the common freshwater cyprinids,Hypophthalmichthys molitrix Cuv.and Val.and Aristichthys nobilis Rich.,by the same hormone during 1958～1963(Tchou et al, 1962)Following a series of works on the culture of female and adult fishes, the induction of spawning of the sexually mature adults and the breeding of young fry,a method for the artificial propagation of these two kinds of fres- hwater fishes was firmly established.This method of artificial propagation was soon popularized throughout our country and the yield of freshwater fishery was greatly promoted.However,the effect of HCG on Ctenopharyngodon idell- us Cur.and Val.,another important freshwater fish of China,was found to be negative by Liu et al(unpublished)and Wu and Chung(1964).The present work was undertaken to reinvestigate the action of HCG on this species of fre- shwater fish. Healthy and sexually mature Ctenopharyngodon with a body weight of ab- out 10.0～15.5 kg.reared in small ponds was used.The chorionic gonadotro- phin was extracted from the urine of pregnant women after the modified Cla- esson's method(Tseng et al,1962)and Got's method(1960).Two HCG preparati- ons with different potency expressed in Bufo unit(Tchou and Wang,1958~ Wang,Tso et al,unpublished)were used for intraperitoneal injection.Artific- ial insemination was performed at about the time of proper maturation and the fertilized eggs were reared in open rectangular containers made of hemp, which were placed in running river on a large scale.The experiments were car- ried out at 22～27℃,and the results obtained can be summarized as follows: 1.Human chorionic gonadotrophin can likewise induce ovulation and ma- turation of oocytes of C.idellus. 2.Within a certain limit,the effect of HCG depends on its purity and the amount injected.Better results can be obtained with purer preparation and in- tensified injection.Thus,the HCG preparation at a concentration of 4.0 mg. in 30cc.Ringer's solution,can induce normal ovulation and maturation of the ovarian fragment of the common toad(Bufo bufo asiaticus),but can not induce ovulation of C.idellus even at a dosage of 80rag.per kilogram.Whereas,anot- her prepartion of HCG at a concentration of 0.5～1.0mg.in 30cc.Ringer's solu- tion can induce ovulation and maturation of the toad oocytes as well as the present fish at a dosage of 10～20mg.per kilogram,obviusly,the failure of so- me authors to affect artificial spawning of C.idellus is probably due either to the non-availability of male and female adult fishes at proper sexual maturity or to the insufficiency in purity and amount of the hormone used,or due to both of these causes. 3.Ovulation takes place 12～15 hours after HCG injection(22～27℃).Incr- ease in the amount of hormone injected will somehow shorten the latent period repuired to initiate ovulation. 4.Cytological study indicates that maturtion division is initiated by human chorionic gonadotrophin.All of the ovulated eggs and sometimes a portion of ov- arian eggs were found to be at the stage of metaphase of the second maturation division upon injecting the hormone(Plate Ⅰ:1～3.Ⅱ:5～8)just like those found in other fishes and vertebrates. 5.The ovulated eggs are mature in the physiological sense,since they can develop normally upon artificial insemination(Plate Ⅰ:4.Ⅱ:9).The percentage of hatchability reached 80% in large-scale experiment,and healthy fries full of vitality were obtained.

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Abstract:1.A comparative study of the species composition of zoobenthos on diffe- rent substrata in the Northern part of Yellow Sea indicates that there exists a great similarity in the eastern fine sand and very fine sand areas in the nor- them extremely fine sand area,and in the southern extremely fine sand and very fine sand areas;but there is a certain difference in the western fine sand area,the northern extremely fine sand and the southern extremely fine sand and mud-sand areas. 2.The main peculiarities of the total biomass distribution of zoobenthos in the northern part of Yellow Sea are as follows:an uneven distribution of biomasses is found in the coastal waters The biomass off the eastern coast of the Liao-tung Peninsula is higher at the depth of less than 40m.than at the depth of 30 m.or than at the depth 30 m.off the northern coast of the Shangtung Peninsula.The biomass distribution is relatively even in the central region of the northern part of Yellow Sea.The biomass is highest in the south of Dairen and Hai-yang Island,north-east of Chenshantou and off the mouth of Yalu River. 3.As for seasonal variations,the total biomass is highest in the spring, moderate in summer and autumn,and lowest in winter.Seasonal variations of the biomass composition of the four main groups of zoobenthos are as follows: The biomass of the Crustacea is higher in the spring and lower in the summer and winter;that of the Annelida is higher in the summer and lower in the spring,autumn and winter;that of the Mollusca is higher in the winter and very low in the summer;that of the Echinodermata is higher in the spring and autumn,and lower in the winter. 4.The peculiarities of the seasonal distribution of the main species of zoobenthos are as follows:(1)The cold-water species(such as Ophiura sarsii,Oregonia gracilis,Pagurus ochotensis,Crangoo affinis etc.)are absolutily dominant in quantity,and distribute mainly in the region of high salinities and low temperatures,at a depth of more than 50 m.(especially in the region within the sphere of influence of cold water masses).(2)The warm-water species(such as Metapenaeopsis dalei,Palaemon graveri,Yrachypenaeus curvirostris,Ophiura kinsbergi etc.)are less in number,and distribute mainly in the shallow waters of lower salinities and higher temperatures along the eastern cosat of Liao-tung Peninsula and the northern coast of Shangtung Peninsula. 5.Yearly variations of total biomass and biomass composition of zooben- thos in March during the four years(1960～1963)have shown that file total biomass is highest in 1963,next in abundance in 1960 and 1961,and lowest in 1962;and that in the composition of biomass,the annelida and Crustacea are more in 1960～1961 than in 1962～1963,while the Echinodermata has the highest and the Mollusca the lowest biomass in 1963.

Abstract:1.Lernaea cyprinacea Linné is parasitic on the skin of bullfrog tadpoles. It is hitherto not known in our country.The parasitic site is at the boundary between the trunk and the tail,where the body is somewhat depressed.The head of the parasite penetrates deeply into the tissue of the host and causes inflammation around the penetration point.This opens the way for bacteria to attack and kill tadpoles. 2.Lernaea cyprinacea Linné living oh the skin of the bullfrog tadpoles is fundamentally identical with that living on the freshwater fishes,except that the body length is shorter than that of the latter(5.2～9.2 mm vs.6.5～22.5 mm). 3.The usual effective concentration of potassium permanganate and the immersion period used to kill the parasites of fishes are unberable to the tad- poles.Spraying the whole pond with low concentration(4～5 PPM)or dipping in higher concentration(10～20 PPM)for alternate short periods has certain curing effect,but the way to total annihilation remains to be found. In order to prevent the dispersion of the disease,it is important to exter- minate the source of the parasites.Spraying the whole pond with 1～2 PPM bleaching powder and potassium permanganate to kill the eggs and larvae of the parasite,isolating the diseased tadpoles and preventing the introduction of infected river water,pond water or water weeds may serve this purpose.

Abstract:The trawl winch is an important equipment for trawlers.Data for theortical ana-lysis for its pull load have not been published as yet.In this paper, various fact-ors affecting pull load of trawl winch are being analysed completely. Derived calcu-lation method of pull load for various steps of hauling the trawl net was based onstatic balance and D'Alembert's principle in calm water and rough-sed. Finally, re-sult of actual ship experiment had been re-calculated by this method. The result ofthis paper was confirmed and may be designed for practical use and for productionof trawl winch.

Abstract:The spawning of Sinonovacula constricta can be induced by lowering the temperature ofsea water from about 20℃ to 10℃--1℃ for 1--36 hours and then raising the temperatureto about 20℃. This method gave positive results in efficiency of 15-70.9 per cent. Withinthe limits of these conditions (10--1℃ and 1--36 h.), the lower the temperature ofthe water and the longer the time treated the higher will be the efficiency. The spawning is also dependent on the presence of certain amounts of oxygen in thewater. When the animals are spawning, there are not any motions of the shells.