Analysis on Growth of Released Black Carp and Annual Benefits from Released Fish in Yantan Reservoir

Yaoquan HAN,Anyou HE,Li HUANG,Jun SHI,Dapeng WANG,Weijun WU

1.Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture,Guangxi Academy of Fishery Sciences,Nanning 530021,China;2.Guangxi International Business Vocational College,Nanning 530007,China

Enhancement and releasing of aquatic organism is a kind of resource conservation measure for increasing the number of biotic population,purifying water and renovating water eco-condition by releasing live aquatic organisms in natural water.Currently,it is of great significance for China to reinforce enhancement and releasing of fisheries and improve fishery quality and quantity in the context of declined fish resources worldwide[1].The Hongshui River is one of the main tributaries of the Pearl River,as well as a key fish-releasing river according to National Aquatic Organism Enhancement and Releas ing Planning[2].Because of dam constructions,eco-environment of the Hongshui River has changed,resulting in frequent fishery ecological accidents.Recently,fishery department has carried out the activity of enhancement and releasing in Yantan Reservoir in order to protect and renovate fishery eco-environment.

The research designed 4 survey sections,including Yantan hydrojunction,Panyang River Reservoir in Dahua County,Anlou Bridge in Donglan County,and water area in Tian’e County along the upper,middle and lower reaches of Yantan Reservoir and major tributaries and collected aquatic organism samples,such as phytoplankton,zooplankter,benthonic animal and fish.Meanwhile,the data on fished species and black carp were recorded every day based on fisherman’s work in upper,middle and lower reaches of the Yantan Reservoir.With sampled data and statistics from fishery department,the research made evaluation on enhancement and releasing effects in Yantan Reservoir in terms of contribution by released black carp to the Reservoir,growth and development,ecological and social benefits,providing references for assessment on work of fishery department in black carp releasing and improvement of enhancement and releasing work in reservoirs.

Materials and Methods

Data source

Survey of fished speciesProfessional fishermen were employed to record the fished species data and biological information in upper,middle and lower reaches of the Reservoir every day[3].Subsequently,2-5 scales below lateral line and dorsal fin of black carp were collected[4]and the age of black carp was estimated on basis of scale sample and fish weight and length[5-6].The fishermen were engaged in fishing with net and hook and seldom with fish cage.In general,nets were cast from 18:00-03:00 of the following day and drawn in at 07:00 of following day.In conclusion,fishing net is 400-500 m,and net specification is 4-10 cm.The research included 4-6 fish cages and 300-400 hooks.

Releasing and fishing ofblack carpsThe information on multiplied and released fish in the Reservoir was obtained by local fishery department to be compared with the sampled black carp in terms of the number and age of fished ones.Comparisons were then performed on the number of fished species in the Reservoir and fish collected by professional fishermen.

Survey on growth and fishing of black carp released in the ReservoirThe released black carp and growth were investigated based on sampled water areas in the Reservoir and the collected data were testified with the data from professional fishermen.

Survey on the quantity of fished species from fish collection sitesThe fished quantity was surveyed and compared with the data provided by local department and by professional fishermen.

Survey on black carp in mature stageThe development of gonad was investigated to evaluate development and proliferation of black carp.

Data analysis

The proliferation of released black carp was surveyed from the perspectives of fishery resource contribution,growth,economic benefits and ecological benefits by statistical method,comparison method,Shannon-Weiner index,Wilhm improved index and DGF species diversity index[7-8].The data were then processed with Excel and biological survey of black carp was conducted with references of The Survey Manual of Fishery Natural Resources in Landlocked Waters[3].Besides,black carp population parameters in Guangxi waters were used for biological parameters of black carp in the research,including growth coefficient of k=0.167 8 and population survival rate of S=0.376.The growth curve of black carp was according to von Bertalanff equations,as follows:

whereWrefers to quality (g);Lrefers to length (cm);erepresents a natural constant;trepresents fish age[6].

Results and Analysis

Distribution of fished fish

During June-November,all fished fish were recorded at 1 409.55 kg,containing 52 365 fish.According to retrieval,the fished fishes included 17 species in 17 genera in 6 families of 3 orders[9].The weight sequence from high to low was as follows:48382%Squalidus argentatus＞14.09%Cyprinus carpio,10.26%Oreochromis mossambicus,6.12%Hypophthalmichthys molitrix,3.93% black carp,3.69%Pelteobagrus fulvidraco,and 3.55%Aristichthys nobilis.

To release black carp in the Reservoir

During the survey period,totaling 18 black carps were caught from upper,middle and lower reaches and the biological data were divided into 18 groups.Besides,18 fish scale samples were preserved,including 4 black carps at the age of 1+,representing 22.22%,6 black carps at the age of 2+,representing 33.33%,black carps at the age of 3+,taking up to 27.78%,and 3 black carps at the ages of 4+and 5+,taking up to 16.67% (Table 2).

To release black carp in an enclosed area

The large-scale enclosed fish farming water in Bama section was investigated and the farming water has an area of 800 000 m2,with an depth of 18 m.It is notable that the farming area communicates with the Reservoir,so that water environment is the same as natural water.In May 2009,many fishes were released,involving 10 000 black carps,5 000 grass carps,20 000 silver carps,30 000 bigheadcarps and 30 000 daces.Since November 2012,3 600 black carps,with a weight of 9 000 kg were caught and 509 black carps with a weight of 3 000 kg were caught since October 2013.It can be concluded that the recapture rate of black carp reached 41.09%.It is notable that biological data should be measured randomly at fishing.

Table 1 Distribution of fished fishes

The growth and development of released black carps

The age and growth indices of released black carpsThe ages of caught samples of black carps were in the range of 1+-5+.It can be concluded that the body-length of 94.44% released black carps is located in the range of Measured Fish Size upon Ages in Natural Rivers and Lakes in Guangxi Province[6]and only one fish(5+)exceeded the range(Table 4 and Fig.1).These indicated thatbodylength and age of released black carps are much normal.

The size and body-length of black carpsIn accordance with GB 17716-1999 Black Carps,the bodylength to size ratio tends to be volatile in the range from 1.127 to 1.191[5].In the Reservoir,the ratio averaged 1.185,within the standard,which indicated that black carps grow healthy in Yantan Reservoir.

The body mass of released black carpsIt can be concluded from growth curve of black carps[6]that 88.89% caught black carps exceeded the theoretical mass,with an average of 25.15% (Table 5 and Fig.2).In the enclosed area,the body mass of 100% black carps exceeded the standard,with an average of 58.21% (Table 6).These suggested that body mass of black carps weighed more than that in natural rivers or lakes.

None natural proliferated fish in the ReservoirBlack carp samples were dissected upon collecting time randomly and gonad maturity was not found at theⅡterm.What’s more,either the black carps with mature gonad or the fish reproducing by spawning was found by multiple surveys.Based on spawning and inhabiting characters and biological environment of the Reservoir,it is hard for black carps available in Yantan Reservoir to grow mature and reproduce naturally.

Table 2 Biological characters of released black carps

Table 3 Biological data of black carps in the enclosed area

Economic benefits ofreleased black carps

Direct economic benefitsIn 2013,totaling 310 000 black carps were released in Yantan waters and the survival rate of the fish in natural riversand lakes in Jiangxi reaches 37.6%[6].According to the growth curve of black carp[6],11 6 560 black carps at the age of 1+can be produced,with a weight of 83 t;43 830 black carps at the age of 2+can be produced,with a weight of 98 t;16 480 black carps at the age of 3+can be produced,with a weight of 76 t;6 190 black carps at the age of 4+can be produced,with a weight of 47 t;2 330 black carps at the age of 5+can be produced,with a weight of 25 t;fewer black carps at the age of 7+can be found[6].It is obvious that the black carps at the age of 2)dominated and the body mass was 25.15% than theoretical mass.For example,the black carp at the age of 2+was the heaviest at 123 t.

Table 4 The age and body-length of released black carps

Table 5 The weight of black carp released in the Reservoir

Table 6 The weight of black carp in the enclosed area

The price of fish fry is 0.15 yuan per fish and the commercial black carp is 20 yuan/kg according to Black carp Enhancement and Releasing in Guangxi in 2013.It can be concluded that the direct economic value can be as high as 2.46 million yuan and the input/output ratio is 1:53.

Indirect economic benefitsIn accordance with Annual Aquatic Statistical Report of Guangxi in 2010,the output value ratios of fishing with the secondary and tertiary industries were 1.43:1 and 1.16:1.In 2013,the indirect economic value to the secondary and tertiary industries by releasing 310 000 black carps reached 3.84 million yuan.

Economic benefits from releasing black carpRecently,Limnoprna lacustris has been widespread and uncurbed in Yantan Reservoir,so that black carp is released to resolve the ecological issue.It can be concluded by transformation of biomass of benthonic animal and fish productivity and P/B transformation coefficient,use rate,and feed coefficient[6]that the output of released black carp totaled 123 tons and 1 230 tons benthonic animal can be removed dominated byLimnoprna lacustris.

It is an effective way to remove nitrogen and phosphorous from water.In general,fish contains 2.5% -3.5% nitrogen and 0.3% -0.9% phosphorus[10-11].It can be concluded based on averages that 123 tons black carps can be produced in 2013 and 3 690 kg nitrogen and 740 kg phosphorus can be removed.

Conclusion and Discussion

According to survey and assessment,it is difficult for natural reproduc-tion for released black carps due to waterenvironment.However,such practice improves fish resource structure in Yantan Reservoir,with economic,ecological and social benefits.

InYantanReservoir,common carp,silver carp,black carp,Pelteobagrus fulvidraco and bighead carp are all fish for releasing.However,except of common carp and Pelteobagrus fulvidraco,the rest are hardly to reproduce in Yantan Reservoir if not by artificial propagation.The survey is of great significance for increasing fish resources and improving fish structure in Yantan Reservoir.

Although artificial propagation brings economic,ecological and social benefits,it is surveyed fish species are few,and the resource is far lower than that of the Red River.For instance,Shannon-Weiner index of the Reservoir is 0.162 and Wilhm improved index is 1.814,suggesting species diversity index is lower than that of other waters[10-13]and fish diversity is in short[14-16].It is the irrational fish structure in the Reservoir that results in irrational components of aquatic organism and poor fishery eco-environment.

The survey results has shown that the number of black carp represents 3.93% of total fished species by fishermen,and just 1.25% provided by fishery department of Yantan Reservoir.It is obvious that the number is lower than the range of 5% -10% in natural rivers and lakes in Guangxi[6].Hence,there is much more room for black carp to increase in the Reservoir.As per Survey on Damages of Limnoprna lacustris in Yantan Reservoir,the sharp drop of black carp is a major cause of the outbreak of Limnoprna lacustris explosion.Currently,more black carps are recommended to be released,for the outbreak is much serious and natural reproduction is difficult in the Reservoir.

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