Huiyun FU, Haihua WANG*, Yanping ZHANG, Bin WU, Wenjing CHEN, Binhua ZHANG, Zhixiang LI

1. Institute of Fishery in Jiangxi Province, Nanchang 330039, China;

2. Dongxiang Henjia Aquaculture Co. Ltd., Dongxiang 331800, China

Misgurnus anguillicaudatus and Paramisgurnus dabryanus are in Misgurnus lacpde of Cobitinae in Cobitidae of Cypriniformes, and widely distributed in Yangtze and Pearl river valleys[1-2].The loach with fat and delicious taste is a kind of freshwater commercial fish. It has quite high nutritional value and medicinal value[3-8]. The loach has a reputation of "turtledove in the sky,loach on the ground", and a good name of"ginseng in the water"[2],and it is considered as a kinds of high grade heath-protection food with high protein and low fat having comprehensive nutrition in Japan and Korea. Therefore,its breeding industry has a broad prospect.

The loach is a kind of fish who lays eggs in batches. Under natural conditions,the loach enters the reproduction period since early April,reaches egg production peak time in May-June, and continues to September[9].There have been a lot of reports about the loach, while no research about the autumn propagation (also known as "Qiufan") of the loach has been reported. In this study, we conducted comparison between the autumn propagation performances of Paramisgurnus dabryanus and Misgurnus anguillicaudatus in Poyang Lake, aiming at providing theoretical basis for the selection of improved varieties in Poyang Lake.

Materials and Methods

Materials

Paramisgurnus dabryanus and Misgurnus anguillicaudatus were obtained from Dongxiang Henjia Aquaculture Co. Ltd. in Jiangxi province.Healthy and strong individuals of Paramisgurnus dabryanus and Misgurnus anguillicaudatus with well-developed gonads and intact fins were selected as parent fish.

Methods

Compound gonadotrophin releasing hormone analogue (batch number:140107) was injected according to 0.3 ml HCG+domperidone solution into pelvic fin muscles of female loaches,and a half amount was injected to male ones. Injected parent fish was put into 80 mesh 2.5 m ×1.0 m ×1.0 m net cages with a rate of female to male of 1.5∶1 at a water temperature of(29±1)℃.A layer of bolting silk was covered on each net cage. The fatness coefficient was calculated according to the Clark formula, and the fertilized and hatching rates of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were determined.

Fatness coefficient= Body weight(g)/Body length(mm)3×100%

Mature coefficient=Gonad weight(g)/Body weight(g)×100%

Relative fecundity (egg/g) = Egg number(egg)/Somatic weight(g)

Liver index=Liver weight(g)/Body weight(g)×100%

Statistic method

Measurement of countable properties Fifty loaches were randomly selected from classified parent fish of Paramisgurnus dabryanus and Misgurnus anguillicaudatus, respectively,to determine the countable properties,and the biological determination was performed according to Inland waters fisheries resources investigation handbook[10].

Relationship between body length and body weight The function relationship between body length and body weight was fitted adopting power function, and the expression was as follows:W=aLb,Where W:body weight(g);L:body length(mm);a:conditional factor; and b: power exponent. The growth equations of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were obtained according to the measured data,respectively.

Results and Analysis

Countable properties of Paramisgurnus dabryanus and Misgurnus anguillicaudatus

T test was performed on the morphological characteristics of 50 individuals of each of Paramisgurnus dabryanus and Misgurnus anguillicaudatus, to get arithmetic mean values,standard deviations and P values,which were shown in Table 1. The results showed that, no significant difference was found between the values of body length/caudal-peduncle length of Paramisgurnus dabryanus and Misgurnus anguillicaudatus as well as between the values of length/caudal-peduncle depth(P＞0.05).

Fatness

Fatness is an important biological basis for judging productive period of fishes and the most common aggregative indicator frequently used for fish status, which changes in fish growth process with gender and age. Difference analysis was performed between Paramisgurnus dabryanus and Misgurnus anguillicaudatus about fatness,and the result showed that the difference was not significant (P ＞0.05);while by t test between female and male individuals of the same species,it was found that, the difference between female and male individuals of Paramisgurnus dabryanus was not significant (P ＞0.05), and the female and male individuals of Misgurnus anguillicaudatus were significantly different (0.01 ＜P ＜0.05), as shown in Table 2.

Relative fecundity

According to the determination by dissection, the relative fecundity increased with increasing body weight and body length of female individual,the gonad weights,mature coefficients and relative fecundities of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were different, and the gonad weight, mature coefficient and relative fecundity of Misgurnus anguillicaudatus were significantly higher than those of Paramisgurnus dabryanus (P＜0.01). The results were shown in Table 3.

Table 2 Fatness of Paramisgurnus dabryanus and Misgurnus anguillicaudatus

Propagation

Propagation is an important link in fish culture and genetic breeding, and indicators including induced spawning rate, fertilized rate and hatching rate are important reference coefficients for propagation. The induced spawning rates of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were of (94.36±3.79) and (98.72±0.58), respectively; the fertilized rate of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were of(90.62±4.72) and (97.52±0.58), respectively; and the hatching rate of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were of(92.45±1.15) and (97.16±1.02), re-spectively. The propagation states of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were shown in Fig.1.

Table 3 Relative fecundities of Paramisgurnus dabryanus and Misgurnus anguillicaudatus

Relationship between body length and body weight

Curve fitting was performed on body lengths (L, mm) and body weights (W, g) of Paramisgurnus dabryanus and Misgurnus anguillicaudatus adopting power exponent. The results showed that the optimal regression equations for the relationships between body lengths and body weights of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were as follows:

WParamisgurnusdabryanus=0.016L2.738(R2=0.915, n=124) and WMisgurnusanguillicaudatus=0.012L2.828(R2=0.956, n=119 ) (Fig.2 and Fig.3).

Discussion

Fatness serves as an aggregative indicator for judging the physiological status and nutritional status of animals in adapting the environment, and is widely used for studying the relationships between animal growth status with age, gender, environment, season and population density, and intraspecific and interspecific rela ionships. The fatness is influenced by food. It could reflect the intake of the two loach species to fodder as they were raised in the same environment.Variance analysis was performed on male and female individuals of Paramisgurnus dabryanus and Misgurnus anguillicaudatus according to obtained data, which showed the difference between the two species was not significant(P＞0.05).However,by t test between male and female individuals of the same species, Paramisgurnus dabryanus showed a non-significant difference (P＞0.05),while the male and female individuals of Misgurnus anguillicaudatus were significantly different (0.01 ＜P ＜0.05). The fatness of female Misgurnus anguillicaudatus was remarkably bigger than that of male ones, which might because the gonads of female Misgurnus anguillicaudatus were well developed in breeding season and carried a lot of eggs.By comparison of mature coefficients and relative fecundities of Paramisgurnus dabryanus and Misgurnus anguillicaudatus, it was found that both the mature coefficient(11.36%)and relative fecundity(147.69 eggs/g) of Misgurnus anguillicaudatus were greater than those (6.56% and 115.70 eggs/g) of Paramisgurnus dabryanus, with significant differences(P＜0.01).

The relationship between body length and body weight is described as W=aLbgenerally according to researches in Biology of Fishes,where a represents the body weight of fish body per unit of body length; and the value of b reflects body shape and body weight: when b is equal to 3, it represents isometric growth, i.e., body shape and volume weight keep constant in growth process,and when b is greater or less than 3, it represents allometric growth[10],i.e.,it shows relative rapider body weight increase at a value greater than 3,while on the contrary at a value less than 3.The fluctuation of b value mainly reflects the variation of body shapes of fishes,while fish growth is closely related to environment and changes frequently.The change is related to characteristics of various fishes in different environments, and the isometric growth is most ideal when b= 3. It could been seen from Fig.2 and Fig.3, the b value of Misgurnus anguillicaudatus was of 2.828 and that of Paramisgurnus dabryanus was of 2.738, both were close to 3,indicating that the growth of the two kinds of fishes was well balanced,which accorded with the growth characteristics of Paramisgurnus dabryanus and Misgurnus anguillicaudatus in Suzhou studied by Wang[12].

The ratios of female loaches to male loaches are different in artificialreproduction of the loach.Because the number of male loaches was obviously less than that of female loaches during autumn propagation, a ratio of female loaches to male loaches at 1.5∶1 was adopted to proceed the natural propagation assisted by artificial spawning.The results showed that the induced spawning rates of Paramisgurnus dabryanus and Misgurnus anguillicaudatus were of 94.36% and 90.6%,respectively, and the fertilized rate were of 98.72% and 97.52%, respectively. In conclusion, the propagation performances of Misgurnus anguillicaudatus was better than that of Paramisgurnus dabryanus during autumn propagation period.

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