2021 Vol. 17, No. 5
Taking Foshan and Taiwan populations of Micropterus salmoides as parents, we established four populations including Foshan inbreeding group (Foshan ♀×Foshan ♂), Taiwan inbreeding group (Taiwan ♀×Taiwan ♂), normal progeny (Foshan ♀×Taiwan ♂) and reciprocal progeny (Taiwan ♀×Foshan ♂) , and carried out a 6-month experiment, in order to compare their growth and morphological characteristics. Results show that the growth performance and coefficient of variation for body mass were significantly higher in the hybid groups than in the two inbred groups. The results of morphological analysis show that the morphological differences of the four populations were mainly in the middle part of trunk and tail. The contribution rate of the first three principal components was 92.9%, and that of the first principal component was 71.3%, mainly reflecting the morphological characteristics of the front and middle part of the body. The contribution rate of the second principal component was 16.6%, reflecting the characteristics of the tail region of fish body. In the scatter plot of the scores of the first two principal components, the four populations could be completely distinguished due to the low overlap area. The stepwise discriminant model constructed by combining measurable traits and frame traits showed the highest accuracy (86.7%–96.0%). The results provide references for the growth and morphological identification of hybrid families of M. salmoides from Foshan and Taiwan populations.
To explore the probiotic potential of Candida ethanolica GXU01 in tilapia culture and to find ecological and friendly feeding bacteria for tilapia sustainable cultivation, we used C. ethanolica GXU01 as feed-additive to feed tilapia. Then we determined the growth performance, intestinal digestive enzymes, serum non-specific immune indexes and intestinal microbial community structure, and challenged the tilapia with Streptococcus agalactiae, so as to comprehensively evaluate the effects of C. ethanolica GXU01 on the growth and immunity of tilapia. The results show that the growth performance, digestive enzyme activity, serum lysozyme activity and complement C3 content of tilapia could be significantly improved by feeding C. ethanolica GXU01 (P<0.05). The abundance of Fusobacteria, Cetobacterium and Akkermansia in the intestinal tract of tilapia increased significantly and those of Cyanobacteria decreased significantly after feed of C. ethanolica GXU01. In the challenge test, the survival rate of tilapia fed with diet containing C. ethanolica GXU01 increased by 26.66%. The study shows that C. ethanolica GXU01 promotes the intestinal digestive ability and immune resistance of tilapia.
In order to make use of interspecific competition to co-culture beneficial microalgae and build excellent algal forms in ponds, we designed different temperature gradients (10, 15, 20, 25, 30 and 35 ℃) and different initial density ratios (Navicula pelliculosa∶Chlorella vulgaris was 1∶10, 1∶1, 1∶0.1, respectively) for an experiment, and investigated the effects of temperature and initial density ratios of N. pelliculosa and C. vulgaris on their growth and competition. The results show that the cell density of N. pelliculosa in mono-culture group increased first and then decreased at 10−15 ℃, and increased gradually at 20−30 ℃ with a maximum value of 0.50×106 cells∙mL−1; 25−30 ℃ was the optimal growth temperature for N. pelliculosa which could not survive at 35 ℃. C. vulgaris grew slowly or even stopped at 10−15 ℃, but grew rapidly at 20−35 ℃ in mono-culture group. The maximum value of the cell density was 14.15×106 cells∙mL−1. The optimal growth temperature was 35 ℃. The growth rate of N. pelliculosa in mixed culture group was higher than that in mono-culture group, and increased gradually with increase of proportion of C. vulgaris. The maximum cell density of N. pelliculosa in mixed culture group was significantly higher than that in mono-culture group. The smaller the initial cell density was, the faster C. vulgaris grew in mixed culture group. The growth rate of 1∶0.1 group was significantly higher than that in mono-culture group, and the growth rate of 1∶10 group was significantly lower than that in mono-culture group. The competitive inhibition parameter shows that C. vulgaris had little competitive inhibition on N. pelliculosa. The competitive inhibition parameter of C.vulgaris against N. pelliculosa (α value) increased with increase of temperature and proportion of C. vulgaris, while that of N. pelliculosa against C. vulgaris (β value) increased with increase of temperature and proportion of N. pelliculosa. The two microalgae can coexist peacefully.
In this study, photosynthetic bacteria (PSB) were isolated and purified from marine environmental samples from different areas by double-layer plate coating method and scribing method. Vibrio parahaemolyticus, V. vulnificus and V. anguillarum were used as control. The inhibition of marine photosynthetic bacteria was determined by Oxford cup method, and the degradation of nitrite nitrogen (NO2 −-N) and ammonia nitrogen (NH4 +-N) by different strains was determined by naphthalene ethylenediamine hydrochloride spectrophotometry and indophenol blue spectrophotometry. The results show that three strains of photosynthetic bacteria were isolated from 30 sea water and mud samples, and the P-3 strain isolated from the seawater samples of Cheniushan Island in Lianyungang had strong inhibitory effect on three kinds of Vibrio, especially for V. anguillarum, with the inhibition zone diameter of 5.3 mm. The results show that all the three photosynthetic bacteria have certain ability to degrade NO2 −-N and NH4 +-N, and P-3 strain had the strongest ability. The degradation rates of P-3 strain were 89.68% and 94.98% respectively, when being cultured in the medium containing 50 mg·L−1 NH4 +-N and NO2 −-N for 4 d. P-3 strain was identified as Rhodopseudomonas palustris by morphological observation, physiological and biochemical tests and 16S rDNA sequence analysis.
To investigate the effects of desiccation on adult red swamp crayfish (Procambarus clarkii), we designed a desiccation stress for crayfish for 0, 3, 6, 12, 24, 36, 48, 60, 72, 96, 132 and 144 h under the conditions of (16±1) ℃ and (55±5) % relative humidity (RH). The results show that the half-lethal time (LT50) of male and female crayfish were 148.36 and 144.01 h, respectively. The mass consumption rate increased gradually with the extension of desiccation time; the weight consumption of male reached 16.09% of body mass after 144 h desiccation, while that of female reached 15.87% of body mass after 132 h desiccation. Besides, the histological structure damage of gill, hepatopancreas and muscle was gradually aggravated. Moreover, the activity of lactate dehydrogenase (LDH) in hepatopancreas and muscle first increased and then decreased. The maximum LDH activities of hepatopancreas in female and male were observed at 24th and 36th hour, while those of muscle in female and male were observed at 36th and 48th hour, respectively. The lactic acid (LA) content of muscle showed similar trend, with LA contents of female and male being the highest after 60 and 48 h desiccation stress, respectively. The succinate dehydrogenase (SDH) activity reduced significantly during desiccating. Furthermore, the desiccation tolerance of adult crayfish reached the limit after 48 h, and the respiratory metabolism gradually transformed from aerobic respiration to anaerobic respiration, accompanied by histological damage. In conclusion, the ability of resist desiccation between male and female is different. Thus, the desiccation time should not exceed 36 h when transporting adult crayfishes.
By using method of experimental ecology, we studied the effects of salinity (2, 4, 8, 12, 16) and Na+/K+ (27, 50, 75, 100, 125 and 150) ratio on 72 h survival rate, hepatopancreas and muscle structure of Litopenaeus vannamei juveniles with body mass of (1.35 ± 0.37) g under experimental condition. The results show that survival rate of L. vannamei decreased with increasing salinity when the Na+/K+ ratio was above 75. In addition, when the water salinity was over 8, the survival rate increased with decreasing Na+/K+ ratio. The survival rate of L. vannamei was above 66.67% when the Na+/K+ ratio was 27−75. When the Na+/K+ ratio was 100, the half lethal time (LT50) of L. vannamei was 69.78 and 60.15 h at salinity of 12 and 16, respectively. When the Na+/K+ ratio was 125, the LT50 at salinity of 8, 12 and 16 was 76.23, 62.61 and 49.10 h, respectively. When the Na+/K+ ratio was 150, the LT50 at salinity of 4, 8, 12 and 16 was 87.24, 68.65, 59.4 and 39.95 h, respectively. Based on the two-factor variance analysis, the 72 h survival rate of L. vannamei was significantly influenced by salinity, Na+/K+ ratio and their interactions (P<0.001). Histopathology observation reveals that high Na+/K+ ratio can cause abnormal histological change in shrimp muscle and hepatopancreas, such as cell vacuolation or autolysis, larger intercellular space, fuzzy and disordered boundary between tissues. In general, potassium deficiency can aggravate the tissue injury of L. vannamei with higher salinity.
In this paper, we investigated the effects of water temperature, photoperiod and light intensity on the survival, feeding and growth of Schizothorax biddulphi juveniles by using experimental ecological methods; predicted the optimal growth conditions for the juveniles by Box-Benhnken design; and studied the saline alkali tolerance of juveniles by single factor static toxicity acute test. The results show that the survival rate of the juveniles was above 85% at 5−25 ℃. The feeding rate, length growth rate and specific growth rate reached the maximum values at 20 ℃. When the photoperiod was 16 L∶8 D and the light intensity was 500 lx, all the indices of the juveniles reached the maximum values. Under conditions of water temperature of 12.98 ℃, daily light time of 15.07 h and light intensity of 670.27 lx, the best survival, feeding and growth were obtained. The LC50 of NaCl salinity was 4.01, 3.62, 3.29 and 2.92 g·L−1 at 24, 48, 72 and 96 h, respectively, and the safety concentration (SC) was 0.89 g·L−1. The LC50 of NaHCO3 alkalinity was 97.14, 86.75, 80.26 and 74.52 mmol·L−1 at 24, 48, 72 and 96 h, respectively, and the SC was 20.75 mmol·L−1.
In this study, the healthy rice field eels (Monopterus albus) with body mass of (25.03±0.02) g had been cultured for 10 weeks, and the effects of taurine on the growth, digestibility and intestinal enzyme activity of M. albus were studied. Four treatment groups with high-content fish meal (42%, FM), low-content fish meal (22%, T0) and low-content fish meal diet supplemented with 0.2% (T0.2) and 0.5% (T0.5) taurine were set up, with five replicates in each group. The results show that compared with FM group, the weight gain rate, protein efficiency ratio, dry matter digestibility and protein digestibility of rice field eels decreased in T0 group significantly (P<0.05), while the feed conversion ratio increased significantly (P<0.05). Adding an appropriate amount of taurine could increase the weight gain rate, protein efficiency ratio and dry matter digestibility of rice field eels, but reduce the feed coefficient (P<0.05). The weight gain rate, protein efficiency ratio and protein digestibility in T0.5 group were approximate the same in T0 group (P>0.05). Moreover, comparing with FM group, the intestinal creatine kinase, Na+-K+-ATPase, alkaline phosphatase, trypsin and lipase activities in T0 group decreased significantly (P<0.05), but the activities of the aforementioned intestinal enzyme in T0.2 group increased significantly (P<0.05). The activities of Na+-K+-ATPase, alkaline phosphatase, trypsin and lipase in T0.5 group were higher than those in T0 group, without significant difference (P>0.05). To sum up, 0.2% taurine supplementation in low-content fish meal feed can improve the growth performance, intestinal digestion and absorption function of rice field eel, but excess taurine (0.5%) has no obvious effect.
In this study, we examined the tolerance to carbonate alkalinity of two sizes of Nile tilapia (Oreochromis niloticus) [Large: (21.56±0.27) g, Small: (5.92±0.03) g]. Different carbonate-alkalinity solutions were prepared with NaHCO3 to carry out the experiment: 1) The fish were directly transferred from fresh water to 30 or 22 g·L−1 carbonate alkalinity solutions to determine the mortality. 2) The fish were acutely exposed to different carbonate alkalinity solutions ranging from 6 to 10 g·L−1 for 96 h. 3) For chronic alkaline acclimation experiments, the carbonate concentrations increased gradually at three levels of +2, +4 and +6 g·(L·d)−1. The results show that the half lethal alkalinities of Nile tilapia under acute stress for 96 h ranged from 6.25 to 9.01 g·L−1. The alkaline tolerance of Nile tilapia was weaker than that of fish which adapt to extreme alkaline environment (e.g. Gymnocyprinus przewalskii), but it was still stronger than that of most freshwater cultured fish. At juvenile stage, the tolerance of Nile tilapia to carbonate stress was significantly enhanced when its body mass increased more than three times. Nile tilapia can be acclimated by daily alkaline increment of 2 g·L−1. The relationship of "time-alkalinity-mortality" under acute alkaline stress can be well fitted by complementary log-log model.
We investigated the growth, photosynthetic pigment and color change of Betaphycus gelatinae at different light intensities (1 000, 3 000, 5 000, 7 000 and 9 000 lx). Based on CSE-1 imaging chromaticity detection and analysis, we studied the correlation of color parameter L*a*b*(CIE 1976) with light intensity, growth and photosynthetic pigment. The results show that the relative growth rate and weight gain rate increased significantly with the increase of light intensity. The suitable light intensity for growth was 7 000−9000 lx. However, when the light intensity was 1 000 lx, there was no obvious growth of B. gelatinae. With the increase of light intensity, the contents of chlorophyll a, carotenoids, phycoerythrin and phycocyanin generally decreased, and the color of B. gelatinae gradually changed from reddish brown to green. The tristimulus values (XYZ) showed a significant distribution difference on the CIE 1931 chromaticity diagram at different light intensities. Light intensity was significantly positively correlated with lightness L*(P<0.05), but significantly negatively correlated with red-green value a*(P<0.01). There was a significant positive correlation between relative growth rate with lightness L* and yellow-blue value b*(P<0.05). Chlorophyll a was significantly negatively correlated with lightness L*(P<0.05), but significantly positively correlated with red-green value a*(P<0.05). Both phycoerythrin and phycocyanin were significantly positively correlated with the red-green value a*(P<0.05).
Longline tuna fisheries in the Indian Ocean are commerically important for Chinese offshore fisheries. Water temperature at different depths can affect longline albacore catch rates. In this paper, the generalized additive model (GAM) was used to analyze the relationship between the the catch rate of albacore (Thunnus alalunga) and water temperature at different depths based on the fishery data and corresponding Argo buoy data during 2008−2017. The results show that the catch rate of albacore tuna catch rate was significantly affected by the sea surface temperature (0 m), water temperature at depth of 200 and 400 m. The optimal GAM model explained the variance of catch rate (Catch per unit effort) by 53.3%, and the determining coefficient of model was 0.527. The catch rates of albacore tuna had a nonlinear relationship with the temperature of the three selected water layers. High catch areas were concentrated at the surface layer of 17−30 ℃, 200 m deep sea area of 17−20 ℃, and 400 m deep sea area of 9−15 ℃, and their intersection areas. We have derived the relationship between the spatial distribution of albacore tuna catch rate in the South Indian Ocean and the temperature of three water depth sections for the first time, and the results provide technical support for guiding the rational production of albacore tuna in the Indian Ocean.
Investigation on artificial marking technology is very important supporting work for national fish mark release recapture and effectiveness tracing evaluation issues. In this study, two-month old juvenile black carps (Mylopharyngodon piceus) had been immersed in alizarin complexone (ALC) at a concentration of 100 mg·L−1 for 48 h, and then transferred to normal water for 20 d. Three pairs of otoliths (i.e., sagitta, lapillus and asteriscus) were removed from the black carps by continuous sampling, observed under fluorescence microscope and photographed, so as to evaluate the characteristics of deposition and the marking effect of ALC in different otoliths. The results show that the marked areas were clearly observed in each otolith pair under visible light and different excitation light, with a 100% mark success rate. After 20 d of recovery culture in normal water without ALC, the intensity of ALC mark in otoliths of the marked fish was still very high, showing a good marking effect. Moreover, the optimum light source was blue excitation light, followed by green excitation light. The lapillus was the optimal otolith type for ALC marking and for judgment of time lag among the three pairs of otoliths, followed by asteriscus. In addition, there was a time lag of 1 day between the carps immersed in ALC solution and ALC deposition into otolith, as well as between removing immersed carps from ALC solution and disappearance of ALC mark from otolith.
According to the biological survey of bottom trawl fishery conducted in Daya Bay in the summer of 2017 and the winter of 2018, we analyzed the basic characteristics of the stable isotope of carbon and nitrogen (δ13C and δ15N) in fishery organisms by using δ13C and δ15N techniques. In addition, we constructed a continuous trophic level spectrum, and discussed the differences in the nutritional structure of fishery organisms in different seasons. The results show that the range of (δ13C and δ15N) of main fishery species in Daya Bay were −19.66‰−15.19‰ [Average: (−17.26±0.86)‰] and 11.63‰−16.01‰ [Average: (13.59±0.96)‰], respectively. We used the average δ15N of small zooplankton as a reference to construct the trophic level spectrum of fishery organisms, and found that the trophic level of fishery organisms in Daya Bay ranged from 2.99 to 4.28. The trophic level of fish had the widest span and a more complex diet. We calculated seven quantitative community indices of trophic structure of macrobenthos by using the SIBER model, and found that some organisms shared the preys, and there was a phenomenon of niche overlap. In addition, the community nutrition redundancy in summer was lower than that in winter.
In order to find out the current status of the population structure and growth characteristics of grass carp (Ctenopharyngodon idellus) in the middle and lower reaches of the Pearl River, we have investigated the grass carp population from 2019 to 2020. The results show that the body length of grass carp was 103−665 mm [average: (347.89±96.73) mm]. The body mass was 21.4−6 650.0 g [average: (986.87±842.96) g]. The population age was of 0+−5+, and the dominant age was 1+−3+, accounting for 92.8% of the total number of samples. The body length had a significant power function relation with body mass for uniform motion pattern. The growth could be described by Von Bertalanffy equation with the growth parameters: L∞=1187 mm, k=0.128, t0=−0.282, W∞=31 344.51 g. The index of length growth performance (φ) of grass carp was 5.26, and the growth inflection age was 8.29. The total mortality rate, natural mortality rate, fishing mortality rate and exploitation rate were 0.58, 0.29, 0.29 and 0.5, respectively. The sex ratio (Females/Males) was 1.07: 1. The sexual maturation was mainly at Stage II. Compared with the previous data, the growth performance and fecundity of grass carp all showed a decline tendency; the population structure tended to be miniaturized. In order to promote the recovery of grass carp resources in the middle and lower reaches of the Pearl River, it is recommended to reduce the fishing intensity. Besides, the catch body length should be greater than 791 mm and the mass should be greater than 9 279.11 g.
In this study, TM4 Sertoli cells were injured by triptolide (TP) to construct a germ cell injury model, so as to explore the protective effect of oyster (Crassostrea hongkongensis) hydrolyzed ultrafiltration fractions on TP-induced oxidative damage of TM4 Sertoli cells in mice (Mus musculus). Besides, the molecular mass distribution and trace metal element content of the oyster hydrolyzed ultrafiltration fractions were detected, and the cell viability, GSH content, MDA content and ROS level of TM4 cells induced by TP by ultrafiltration fractions were compared. The results show that the oyster hydrolyzed ultrafiltration fractions are rich in trace metal elements such as copper, zinc, manganese and selenium; most small molecules and macromolecular substances were separated by ultrafiltration; compared with the model group, ultrafiltration fractions improved the cell viability of TM4 cells induced by TP. The cell viability of <3, 3–5 and 5–10 ku ultrafiltration fractions was higher than that of >10 ku ultrafiltration fraction; <3 ku ultrafiltration fraction could prevent TP-induced oxidative stress damage in TM4 cells, reduce the production of intracellular reactive oxygen species and lipid peroxidation, and enhance the antioxidant activity of TM4 cells.
In order to accumulate the basic physiological index data for juvenile yellowfin tuna (Thunnus albacores), we evaluated the blood potassium ion (K+), calcium ion (Ca2+), chloride ion (Cl−), hydrogen ion (H+), pH, glucose, lactic acid, sodium ion (Na+) and total hemoglobin concentration and hematocrit, osmotic pressure of the juveniles of different body lengths (20G: 20−30 cm, 30G: 30−40 cm, 40G: 40−50 cm). Results indicate that the blood parameters of the juveniles were relatively stable in the three body length groups. K+, Ca2+, Cl−, H+, pH, glucose and hematocrit were not significantly different between groups (P>0.05). The content of lactic acid and total hemoglobin concentration in the 20G group was significantly higher than the other two groups (P<0.05). The standardized calcium ion in the 30G group was significantly higher than the other two groups (P<0.05). The sodium ion content decreased with the increase of body length gradually, and the difference between the adjacent two groups was not significant (P>0.05). The results show that the juveniles had a small difference between the 30G and 40G groups. The 20G group was relatively different from the other two groups. As body length increased, blood indicators tended to be more stable.