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1.
Estimating rates of mortality is important for assessing stocks and for effectively managing seafood resources. This study reports the first estimates of rates of instantaneous fishing mortality (F) and natural mortality (M) for the commercially important school prawn, Metapenaeus macleayi. Replicated tag-recapture experiments were conducted on two stocks (Clarence River and Wallis Lake) to estimate the catchability coefficient (q) and F, whilst M was estimated from meta-analyses. Experiments were conducted across spatial and temporal scales to consider variability between stocks and variability between fisheries targeting this resource. The catchability coefficient was fitted to tag-recapture data in a population model across a range of M values (0.001-0.025 per day) and average daily F values were calculated. Values of q ranged between 2.03E−04 and 5.43E−02 and, 1.29E−04 and 3.41E−03 for the Clarence River and Wallis Lake stocks, respectively. Average daily F ranged between 2.86E−03 and 1.69 for the Clarence stock and 1.71E−03 and 3.44E−02 for the Wallis stock. With one exception (the November 2004 experiment) there were no differences in q and F values between experiments conducted on the Wallis Lake stock. For the Clarence stock values of q and F varied between years and within years. Factors thought to contribute to this variability were changes in prawn behaviour, differences in sizes of prawns tagged between experiments and differences in the survival of tagged prawns. The catchability coefficient for the Clarence River stock was weakly correlated to greater rates of river discharge. Estimates of F for the Wallis stock, the Clarence stock in 2004-05 and estimates of M were comparable to those reported for other penaeid fisheries world wide. There was no consistent pattern in comparisons of q and F values between the predominantly trawling operation of the Clarence River fishery and the seine netting of the fishery in Wallis Lake.  相似文献   

2.
生物学指标在评定养殖鲫肝脏脂肪蓄积程度中的作用   总被引：1，自引：0，他引：1  
为了了解配合饲料养殖鲫肝脏中脂肪蓄积状况,以及肥满度、体质量/体长、脏体指数、肝体指数、肠系膜脂肪指数、肠道指数等6项生物学指标在评定养殖鲫肝脏脂肪蓄积程度中的作用,分别采用物理方法和索氏抽提法对30尾野生鲫和60尾配合饲料养殖鲫的生物学指标和肝脏脂肪含量进行了检测;采用HE染色法制作和观察了鲫肝脏组织切片;采用SPSS 19.0软件对生物学指标和肝脏脂肪含量的相关关系进行了统计分析.结果表明,养殖鲫的肥满度、体质量/体长、脏体指数、肝体指数、肠系膜脂肪指数、肠道指数、肝脏脂肪含量平均值均高于野生鲫;其中野生和养殖鲫肝脏脂肪含量平均值分别为2.11％±0.69％和19.49％±4.31％.肝脏组织学检查发现野生鲫肝细胞形态正常,肝细胞轮廓清晰,且沿肝细胞索有序排列,无脂肪空泡;养殖鲫的肝脏细胞形态大小不一,细胞核萎缩、溶解以及偏移细胞中央的现象比较严重,肝细胞轮廓不清,脂肪严重蓄积时可见明显脂肪空泡.养殖鲫的肥满度、体质量/体长、肠道指数均与肝脏脂肪含量之间无显著相关;但脏体指数(X1)、肝体指数(X2)、肠系膜脂肪指数(X3)均与肝脏脂肪含量(Y)存在显著中等正相关,多元线性回归方程为Y=8.085 +0.282X1+3.726 X2 +0.505X3(R =0.562,F=3.995,P=0.018).养殖鲫肝脏中脂肪蓄积现象严重,并且蓄积程度随脏体指数、肝体指数、肠系膜脂肪指数的增加而加重.  相似文献   

3.
Atlantic salmon (Salmo salar, L.), kept in sea pens were fed diets containing pure carotenoids. No significant preferential utilization of the (3S,3′S), (3R,3′S) or (3R,3′R) optical isomers of astaxanthin was observed. No epimerization occurred in the flesh at the chiral centres at C-3 and C-3′ in astaxanthin.  相似文献   

4.
In vitro accumulation of tetrodotoxin (TTX) and paralytic shellfish toxin (PST) in tiger puffer fish Takifugu rubripes was investigated using liver tissue slices. When T. rubripes liver slices were incubated with Leibovitz’s L-15 medium containing 0.13 mM TTX at 20 °C in air with saturated humidity, they accumulated 21.5 ± 7.3 μg TTX g?1 liver after the incubation for 12 h and increased to 55.3 ± 8.2 μg TTX g?1 liver at 48 h. In the incubation of T. rubripes liver slices with 0.13 mM PST-containing medium, PST was detected 6.3 ± 0.9 μg g?1 liver at 12 h and reached a plateau thereafter. These results reveal the difference between TTX and PST in accumulation in T. rubripes liver tissue slices. To examine the variation in PST accumulation among fish species, the liver tissue slices from tiger puffer fish T. rubripes, parrot-bass Oplegnathus fasciatus and green ling Hexagrammos otakii were incubated at a concentration of 0.027 mM PST. The toxin contents of 3.0 μg g?1 liver were observed at 8 h regardless of fish species but were not increased subsequently, showing no variety among these three species as to accumulation patterns of PST. It is noted that the tiger puffer fish T. rubripes liver specifically accumulate TTX in preference to PST.  相似文献   

5.
The tilapias were formerly included in the genus Tilapia. Now only the substrate-brooders retain the generic name Tilapia, e.g. Tilapia sparrmanii, T. guineensis. There are two main kinds of mouth-brooders, Sarotherodon (e.g. S. galilaeus) and Oreochromis (e.g. O. mossambicus, O. niloticus, O. macrochir). In Sarotherodon brooding is paternal or biparental (where known), in Oreochromis maternal. All are included, with a few other genera, in the Tribe Tilapiini and may be referred to colloquially as tilapias, with a small ‘t’ and no italics.  相似文献   

6.
To identify the factors that influence the growth rate of flathead flounder Hippoglossoides dubius in Funka Bay, Japan, we studied temporal changes in the growth of this species and its prey from 1989 to 2012. The lowest growth rate of H. dubius was recorded in the 1995 year-class, which had experienced severe hypoxia between 1995 and 1997. However, the highest growth rate was recorded in the 2007 year-class, which had experienced hypoxia between 2009 and 2011. In 2000 and 2001, small-sized flounder (<200 mm TL) from the 1995 year-class were feeding on mysidaceans, whereas those from other year-classes fed on small Ophiura spp. (<9 mm in disc diameter) in 2009, 2011, and 2012. Small Ophiura spp. were more abundant in 2007 and 2011 than in 2002 and 2003. Successful recruitment of Ophiura spp. took place between 2007 and 2011 and cohorts from these years could tolerate hypoxia. This suggests that food availability improved under hypoxic conditions, which led to improved growth in small flounders. Large flounders (≥200 mm TL) from all year-classes fed on prickleback fishes (Stichaeidae) and walleye pollock Gadus chalcogrammus juveniles. The growth of large flounders was enhanced by an increase in the abundance of Stichaeidae fishes and G. chalcogrammus juveniles.  相似文献   

7.
Preliminary determinations for the best species combination for the fastest rate of growth of Tilapia nilotica (Saro therodon niloticus) and T. zillii indicated that T. nilotica grew better (1.3 g/day) when raised with T. zillii (0.9 g/day) and common carp, Cyprinus carpio (3.2 g/day). In other non-replicated experiments involving T. nilotica and T. zillii only, growth rates of 1.0 g/day and 0.9 g/day were recorded respectively which bettered those observed in monoculture experiments, namely 0.8 g/day and 0.6 g/day respectively.  相似文献   

8.
Bonamia ostreae is an intracellular haplosporidian parasite in European flat oysters Ostrea edulis that occurs on both coasts of the United States and causes significant mortality in Europe. Canada was considered free of B. ostreae until 2004, when it was first detected in O. edulis obtained for laboratory study from a western Canadian oyster farm. Bonamia ostreae was confirmed in O. edulis at the index farm in November 2004 using histopathology, conventional polymerase chain reaction (PCR) assays, restriction fragment length polymorphism (RFLP) analysis, and sequencing of the PCR product. Archived samples of European flat oysters obtained from the index farm between 1999 and 2004 (n = 343) were re-examined and all samples collected before 2003 (n = 306) were confirmed negative for B. ostreae by histopathology (n = 306) and PCR (n = 62). In archived samples from 2003, B. ostreae was detected in 3 of 37 O. edulis by histopathology (n = 2) and/or PCR (n = 2). Also, records indicate that B. ostreae was not detected in O. edulis (n = 348) from five other locations in western Canada between 1986 and 2000. To better understand the distribution and prevalence of B. ostreae in western Canada, 607 oysters from the index farm and 2 additional farms were sampled in the summer of 2005. All 3 farms had been stocked with O. edulis spat from the State of Washington, USA, where B. ostreae is endemic. Samples were analyzed by histopathology and a new real-time PCR that amplifies a 68-bp target DNA fragment. B. ostreae was detected in all three locations, with prevalence ranging from 0.5 to 11.1%. Diagnostic sensitivity of the real-time PCR method was consistently greater than histopathology. Also, preliminary evidence supports the conclusion that real-time PCR on paraffin sections is more sensitive than histopathology; B. ostreae DNA was confirmed in 4 oysters by real-time PCR on paraffin-embedded tissues (and independently confirmed on unfixed tissues) that was not detected by histopathology. As a result of these findings, O. edulis spat are no longer allowed to be imported from endemic areas into Canada.  相似文献   

9.
《水生生物资源》1998,11(5):325-334
Patterns in fish taxa composition were examined in Portuguese reservoirs to assess whether distinct types of assemblages exist. Furthermore, the environmental variables most tightly associated with assemblage-level patterns were identified. Classification of the fish taxa-by-reservoirs matrix revealed four major groups. Groups were separated by means of canonical correspondence analysis according to (by decreasing correlation with canonical axis): air temperature, annual rainfall, surface elevation, trophic state, mean depth and reservoir placement within the basin. In addition to these variables, stocking practices and predation likely contributed to assemblage composition. Assemblages in group A were distinguished by the permanent presence of largemouth bass (Micropterus salmoides) and the absence of trout (Salmo trutta and/or Oncorhynchus mykiss), nase (Chondrostoma sp.) and barbel (Barbus sp.). Group B assemblages invariably included bass, barbel and nase, while pumpkinseed (Lepomis gibbosus) was frequent and trout was extremely rare. Assemblages in group C were also characterised by nase and barbel, but in contrast to group B, trout was frequent, whereas bass was rare and pumpkinseed was absent. Group D assemblages consisted exclusively of trout and chub (Leuciscus sp.). The relationships observed parallel patterns detected in natural lakes to a certain extent, despite the critical human influence and the probable instability of some of the patterns detected.  相似文献   

10.
Octopus (Amphioctopus) areolatus is an important marine cephalopod in Japan. We examined its diploid chromosome number, karyotype, and genome size (C value), and performed fluorescence in situ hybridization (FISH) using a vertebrate telomeric probe. The diploid chromosome number was 60 in embryonic cells, with 24 pairs of metacentric chromosomes, four pairs of metacentric/submetacentric chromosomes, and two pairs of submetacentric chromosomes. The mean C value was estimated to be 5.47 pg. From these findings, and those reported previously for other octopus species, we suggest that the factor causing the quantum change of C value in O. (A.) areolatus was genome duplication, and not polyploidy. In telomeric FISH analysis, hybridization signals were clearly observed in the telomeric regions of the chromosomes. This is the first report of FISH analysis of cephalopod chromosomes, and our findings suggest that the telomere sequence of O. (A.) areolatus is (TTAGGG) n , which may allow gene mapping in the future.  相似文献   

11.
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12.
In the present study, different reference genes were isolated, and their stability in the skeletal muscle of fine flounder subjected to different nutritional states was assessed using geNorm and NormFinder. The combinations between 18S and ActB; Fau and 18S; and Fau and Tubb were chosen as the most stable gene combinations in feeding, long-term fasting and refeeding, and short-term refeeding conditions, respectively. In all periods, ActB was identified as the single least stable gene. Subsequently, the expression of the myosin heavy chain (MYH) and the insulin-like growth factor-I receptor (IGF-IR) was assessed. A large variation in MYH and IGF-IR expression was found depending on the reference gene that was chosen for normalizing the expression of both genes. Using the most stable reference genes, mRNA levels of MYH decreased and IGF-IR increased during fasting, with both returning to basal levels during refeeding. However, the drop in mRNA levels for IGF-IR occurred during short-term refeeding, in contrast with the observed events in the expression of MYH, which occurred during long-term refeeding. The present study highlights the vast differences incurred when using unsuitable versus suitable reference genes for normalizing gene expression, pointing out that normalization without proper validation could result in a bias of gene expression.  相似文献   

13.
Composite fish culture of the Indian major carp, Catla catla, Labeo rohita and Cirrhinus mrigala together with the Chinese silver carp Hypophthalmichthys molitrix and grass carp Ctenopharyngodon idella and the Indonesian strain of common carp (Cyprinus carpio communis) was carried out in experimental ponds in 1971–1972 and 1973–1974. The management techniques adopted aimed at high yields of marketable fish (around 1 kg) in 1 year.In the first year, production varied from 3 889 to 5 600 kg/ha/year and this rose to an average of 8 200 kg/ha/year with a maximum of 9 389 kg/ha/year in the second year. The important changes made to the management schedule in 1973 were increased stocking density, greater use of feed and fertilizers, and provision of more weeds for grass carp.The experimental studies demonstrate the practicability of raising large crops of healthy marketable fish in India.  相似文献   

14.
SOX9基因在脊椎动物性别决定和性腺分化中扮演重要的调控作用。从mRNA和蛋白水平分析中华鳖SOX9基因在不同组织中的差异性表达、在胚胎性腺和成年睾丸中的细胞定位以及在性逆转中的表达变化,研究SOX9基因在中华鳖性别分化中的调控作用。Real-time PCR结果显示,SOX9基因在中华鳖雄性性腺中特异性表达。免疫荧光染色分析显示,SOX9蛋白在雄性18期胚胎性腺中开始表达,随着性腺的发育,SOX9蛋白定位于性腺Sertoli前体细胞细胞核中;而在雌性胚胎性腺并未见其表达。此外,在雌激素诱导的雄性向雌性性逆转胚胎中,SOX9基因显著下调,而在芳香化酶抑制剂诱导的雌性向雄性性逆转胚胎中,SOX9基因表达则显著上升。研究表明,SOX9基因为中华鳖雄性特异性基因,参与雄性性腺的发育过程,可能在中华鳖早期性别分化过程中起调控作用。  相似文献   

15.
Cre/loxP-mediated cell targeting is considered to be a powerful tool for biotechnology in farmed fish. As a first step toward establishing cell targeting in salmonids, we analyzed the functionality of the Cre/loxP system in rainbow trout. We first established stable transgenic strains carrying the DsRed gene, which was flanked by loxP sites and further spliced with the EGFP gene. By microinjecting Cre complementary RNA (cRNA) into fertilized eggs of the transgenic trout, the functionality of the Cre/loxP system was evaluated. The results showed that all of the embryos exhibited green fluorescence in at least some of their cells. While 19 out of 20 embryos comprised cells showing both green and red fluorescence, the remaining embryo showed only green fluorescence. Polymerase chain reaction (PCR) using primers designed to recognize sequences outside of the two loxP sites revealed that, in addition to long intact fragments, the 19 individuals carried short fragments that were equivalent in length to the loxP-excised fragments. The remaining green embryo carried only this short fragment. DNA sequencing of the short fragment revealed that it lacked the DNA fragments flanking the loxP sites and the spliced fragments did not contain any sequence rearrangements. These results suggest that the Cre/loxP system is functional in rainbow trout.  相似文献   

16.
The results of four field experiments on rearing fry to fingerlings of mainly exotic carp, Hypophthalmichthys molitrix, Ctenopharyngodon idella and Cyprinus carpio var. communis conducted for three- and six-month periods during 1971–1975 are presented. In one experiment Labeo rohita, an indigenous species was also introduced as a compatible species. Fry were stocked at densities of 200 000 and 250 000 per hectare in the three-month period and at 100 000 and 250 000 per hectare in the six-month period.Under pond fertilization and supplementary feeding a high percentage of fingerling survival was recorded; the aggregate percentages ranging between 71.50 and 91.16 in the three-month period and 61.26 and 89.03 in the six-month period.  相似文献   

17.
Greenwater technology is based on integrating finfishes inside pens for zero water exchange system of shrimp aquaculture. Nitrogen transformation could be improved by rearing euryhaline finfishes like grey mullet, milkfish which have a broad diet and tolerate poor water quality. The abundance of four denitrifying functional genes coding for nitrate reductase (narG and napA), nitrite reductase (nirS), nitric oxide reductase (qnorB) and nitrous oxide reductase (nosZ) has been examined in the greenwater system through a metagenomic approach. Phylogeny revealed homology of narG clones with uncultured environmental clones, whereas napA clone sequences were found to have homology with cultured (Stappia aggregata) and uncultured microorganisms. The nirS clones show uniqueness with Marinobacter hydrocarbonoclasticus, Aromatoleum aromaticum, and Ruegeria pomeroyi. The qnorB gene has been reported for the first time from culture systems along the Indian coast and clone exhibited 84–87 % identity with different uncultured bacteria. The nosZ clones are closely affiliated with S. aggregate and alpha bacterium. This study revealed denitrifying diversity from a greenwater system which could eventually be used in planning the future strategy for comprehending nitrogen fluxes, greenhouse gases and their mitigation in coastal aquaculture systems.  相似文献   

18.
Three types of vitellogenins (Vgs) namely vitellogenin A (VgA), vitellogenin B (VgB) and vitellogenin C (VgC) have been identified in fishes. The existence of VgA and VgB is reported in the Indian freshwater murrel Channa punctatus. Gene-specific primers were designed using available nucleotide sequences in National Centre for Biotechnology Information (NCBI), for amplification of VgA and VgB cDNA. Differential processing of Vgs is evident in many fishes. Adult male murrel expressed both the VgA and VgB genes when estradiol-17β (E2) is injected in vivo and Vg levels in blood quantified by Enzyme linked immunosorbent assay (ELISA) showed a dose-related response in such treatments. Cultured hepatocytes on treatment with E2, however, expressed only VgB as detected by RT-PCR, suggesting different regulatory mechanism for the VgA and VgB genes.  相似文献   

19.
Selective breeding of European sea bass (Dicentrarchus labrax) receives a growing interest, as the estimated heritability of growth is medium to high. In this study, we compared the offspring of four groups of sea bass sires, mated with the same wild dams: wild (W), first generation of domestication (D), first generation of mass selection for length (M), first generation of PROSPER-like selection for length (P). The comparison was done both in replicated tanks (separate rearing) and in mixed tanks (mixed rearing) where sire origins were recovered by genotyping of eight microsatellite markers. Weight, length and growth rate were measured from day 238 post-fertilization (69 g mean weight) to day 611 post-fertilization (390 g mean weight). Both in mixed and separate tanks, both selected groups (P, M) were larger than unselected groups (W, D). No difference was seen at any time between W and D, nor between M and P. The selection response estimate on weight was larger in mixed tanks when compared to separate tanks (+ 42% in mixed tanks, + 23% in separate tanks at day 611), yielding realized heritability estimates of 0.60 and 0.34, respectively, and confirming the excellent potential of the species for growth improvement through selective breeding. Both selection response and the amplification effect between mixed and separate tanks decreased as rearing density increased. Our hypothesis is that selection response is magnified by competition in mixed tanks, while sub-optimal rearing conditions lower the observed selection response, more in separate tanks (where selected thus larger fish are at a higher density than unselected ones) than in mixed tanks (where all fish experience the same density effects).  相似文献   

20.
Information on aquaculture-related environmental impact along the eastern Adriatic coast is very scarce. In this paper, the area affected by fish farm and sewage derived particulate nitrogen in the Murter Sea and semi-enclosed Pirovac Bay (central Adriatic, Croatia) was assessed using the stable nitrogen isotopic composition (δ15N) in particulate organic matter (POM) and benthic sessile invertebrates (Aplysina aerophoba, Balanus perforatus and Anemonia sulcata) in the exposed areas compared to an unpolluted reference site. The results suggest that increased δ15N values in the POM and biota in the impacted areas are predominantly due to nitrogen losses through feed wastage and fish excretion (faeces), but also due to the sewage discharge into the marine coastal ecosystems. The δ15N values of the selected organisms were significantly higher around fish cages, as well as at sites polluted by urban waste, compared to the reference site and some other pristine offshore locations. The 15N enrichments of A. aerophoba, A. sulcata and B. perforatus collected around fish cages compared to the reference location were up to 6.8, 6.5 and 5.2‰, respectively, which exceeds the natural variability. While the δ15N values of A. sulcata and B. perforatus showed an excellent linear correlation with those of the POM, a weaker correlation was found between δ15N of A. aerophoba and the POM, although its δ15N values consistently increased with the increased δ15N values of POM. This is attributed to the presence of different bacterial populations hosting in the sponge. A geochemical map of the δ15N values in the POM and organisms was created, which could be used for tracing the dispersion of 15N loading generated by aquaculture and sewage in the receiving environment, and their transfer into biota in the adjacent coastal ecosystem. Sponges or other organisms, although known as non-selective suspension feeders, but hosting abundant bacterial populations, may have δ15N values lower than the POM, but still reflecting the overall enrichment of the environment in 15N due to the presence of enriched effluents from aquaculture operation or municipal discharges.  相似文献   

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