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1.
The fishery biology of mud crabs Scylla spp. was examined using baited traps and gill nets from September 2001 to August 2005 at Iriomote Island, Japan. To elucidate the growth of the crabs, artificially produced S. serrata juveniles were released and recaptured at the study site. The sizes at which 50% of females and males of S. serrata reached sexual maturity (SM50) were estimated as an external carapace width (ECW) based on the morphology of the abdomen and the chela respectively. Two species, S. serrata and S. olivacea, were identified in the area with S. serrata being the dominant species (>95% of the catch). Changes in the mean ECW and the results of the release and recapture experiments suggested that the recruitment of young crabs to the fishery occurred from December/January to April/May. The SM50 of females and males occurred at 132.4 and 150.7 mm ECW respectively. The body size composition of S. serrata revealed that immature crabs comprised approximately 40 and 65% of the catch for females and males respectively. To maintain a sustainable fishery for S. serrata, a minimum landing size based on the SM50 estimates should be implemented as a fishing regulation.  相似文献   

2.
An epidemic of ‘milky disease’ in the mud crab (Scylla paramamosain) generally breaks out in the fall when the crab is near maturity, resulting in large economic losses in crab farming. Vibrio parahaemolyticus has been proven to be one of the major pathogens. In this study, the mud crabs were challenged with V. parahaemolyticus, and their innate immune responses were investigated in terms of total haemocyte counts (THCs), haemocytic enzyme activities and gene expression levels during a 114‐h period. The THCs of the mud crabs decreased significantly after 42 h of exposure. The activities of the haemocytic enzymes, including acid phosphatase‐alkaline phosphatase, phenoloxidase, superoxide dismutase (SOD), peroxidase and nitric oxidase synthethase, were significantly enhanced during the challenge course. The gene expression levels also significantly increased for all tested genes (proPO, Cu/Zn‐SOD, Prx, LYS, CRU and ALF) with the exception of CAT down‐regulated expression. The results may imply that the immune responses of the mud crab could be activated by the pathogens, and the data here will provide many clues for further systematic investigation of ‘milky disease’ caused by V. parahaemolyticus and the disease prevention in mud crab S. paramamosain.  相似文献   

3.
刘红 《水产学报》2006,30(5):577-585
该论文首次报道了经由促雄性腺提取物的注射而在蟹类中引起的性逆转现象。此前关于蟹类促雄性腺活性研究的报道极少，而且蟹类的雄性化均是由促雄性腺的移植所产生。本实验中将锯缘青蟹和中华绒螯蟹的促雄性腺提取物分别注射到刚刚完成性别分化的中华绒螯蟹雌性幼蟹体内，此时幼蟹处于4至5期，壳宽为5～8 mm。注射之后，幼蟹经过大约1～2次蜕皮，此时在注射锯缘青蟹以及中华绒螯蟹的促雄性腺提取物的两组实验幼蟹中均能观察到雄性化现象，而注射生理盐水的对照组实验幼蟹中未能观察到相同现象。由此本实验可以证明促雄性腺确实是蟹类的一种雄性激素，注射促雄性腺提取物能引起雌性幼蟹发生性逆转；同时根据锯缘青蟹和中华绒螯蟹的促雄性腺提取物均能引起中华绒螯蟹雌性幼蟹发生性逆转的现象推测，锯缘青蟹和中华绒螯蟹两种间可能存在促雄性腺的交叉活性；不仅如此，性逆转还能在极低的注射剂量下获得，相当于中华绒螯蟹0.14促雄性腺当量和锯缘青蟹0.06促雄性腺当量。  相似文献   

4.
Vibrio spp. is one of the main pathogens to cause high levels of mortality in the culture industry of mud crabs, Scylla paramamosain. Although considerable efforts have been devoted to understanding the immune response of S. paramamosain against pathogens, both immune‐response proteins and systematic responses to foreign agent invasions have yet to be investigated in detail. Hence, in this study, we challenged S. paramamosain with bacterial lipopolysaccharides (LPS) by injection. We examined a number of immune‐related indices in the crabs at 0, 2, 6, 12, 24, 36, 48, and 72 h postinjection, that is, the total hemocyte counts in hemolymph; the serum activities of phenoloxidase, superoxide dismutase, lysozyme, acid phosphatase, and alkaline phosphatase; and the mRNA levels of immune‐related genes encoding prophenoloxidase, serine protease inhibitors, antimicrobial peptide scygonadin, crustin, anti‐lipopolysaccharide factor, and catalase in hemocytes. In addition, the immune‐response proteins were identified in hemocytes at 24 h postinjection using two‐dimensional polyacrylamide gel electrophoresis. The results showed that the immune‐related enzymes and genes examined were induced in a time‐dependent manner post‐LPS challenge. Moreover, 18 altered proteins were present in the hemocytes and the main proteins to be altered were highly homologous to hemocyanin and protein kinase. Ultimately, this study provides useful information for understanding the immune response of S. paramamosain to bacterial infection.  相似文献   

5.
The production performance of Scylla paramamosain and S. olivacea reared together in ponds and provided with different supplementary diets (crustaceans or trash fish) were evaluated with that of an unfed control group relying only on natural food available within the pond. Each treatment was conducted in triplicate. The aim was to evaluate two production strategies over a 130‐day grow‐out trial: (1) production to 200 g crab?1, which is the minimum preferred marketable size in the Lower Mekong Delta (LMD) and (2) production to 300 g crab?1, the size that fetches the highest market price. Growth production models were estimated which revealed that the rearing period required to produce crabs of 200 g was 102 days with supplementary feeding, compared with 120 days for the unfed control group. The rearing period needed to produce 300‐g‐sized crabs was estimated to be 144 days and 186 days for the supplementary fed and unfed groups respectively. The additional risk involved in rearing mud crabs to 300 g is not considered worthwhile, under similar culture conditions as observed in this trial, as a decrease in pond water quality and higher mortality rates were observed in the final month of culture needed to achieve this larger size.  相似文献   

6.
不断壮大的东海近海笼壶渔业对三疣梭子蟹（Portunus trituberculatus）等甲壳类资源造成了巨大的压力,实施养护幼蟹的管理措施已成为渔业管理者和生产者的共同呼声。本研究通过海上对比试验,分析了放大网目尺寸对蟹笼渔获效率的影响,运用SELECT模型估算了蟹笼对三疣梭子蟹的尺寸选择性,结合混合影响模型探讨了作业时间和可捕群体对选择性分析的影响。结果显示,对照蟹笼（网目尺寸32.0 mm）与试验蟹笼（网目尺寸分别为52.3 mm和59.7 mm）的三疣梭子蟹渔获甲宽分布存在显著性差异;SELECT模型拟合结果显示试验蟹笼与对照蟹笼的相对作业强度无显著性差异,网目尺寸分别为52.3 mm和59.7 mm的试验蟹笼对三疣梭子蟹的50%选择甲宽（CW50）分别为86.9 mm和90.9 mm,选择范围分别为15.9 mm和9.2 mm。试验蟹笼的CW50远未达到浙江省等当前的最小可捕尺寸规定,表明蟹笼渔业中仅依靠放大网目尺寸可能难以实现幼蟹的有效释放。结果分析显示,在此次试验中作业时间和可捕群体的数量对蟹笼的选择性没有显著性影响。  相似文献   

7.
For the improvement of nursery culture of the mud crab Scylla paramamosain, a special nursery facility was purposely designed and built. This facility consists of nursery ponds (areas of 20, 50, and 120 m2, respectively) and a seed collecting pond connected to each nursery pond. There were 140 nursery facility units in operation for large-scale juvenile crab production. A series of experiments were carried out using the facility to investigate the effects of the age of megalopae, stocking density, and culture duration of both megalopae and first-stage crabs on the survival of megalopae and early juveniles of S. paramamosain. The results showed that when megalopae were stocked at a density between 3,000 and 5,000 ind m−2 and reared to reach the first-stage crabs, a survival rate of up to 50% could be achieved. When the first-stage juvenile crabs were stocked at a density between 2,000 and 3,000 ind m−2, their survival was more than 50% after 14 days of culture.  相似文献   

8.
Abstract Optimising harvests from fishery resources requires appropriate data. In this study, fishery‐independent survey and size‐at‐first maturity (L50) data were used to assess the suitability of current minimum legal sizes (MLS) and total allowable commercial catches (TACC) in the South Australian, mixed‐species, mud‐cockle (Katelysia spp.) fishery. Estimates of L50 suggested the MLS was conservative in one fishing zone (Coffin Bay), but appropriate elsewhere. Harvestable‐biomass estimates (HB) demonstrated that TACCs were excessive in the Port River (41% of HB), suitable in Coffin Bay (10% of HB) and precautionary in the West Coast (1.5% of HB) fishing zones. Consequently, the MLS was decreased by 5 mm shell length in Coffin Bay and the TACCs for the Port River (reduced by 80%) and West Coast (increased by 40%) amended. This study demonstrated that harvest strategies in mixed‐species fisheries can be optimised by explicitly considering data on species composition, abundance and population biology.  相似文献   

9.
The performance of hatchery‐reared juveniles either in aquaculture grow‐out systems or stock enhancement is likely to be dependent on a range of factors during the hatchery phase of production. With recent progress in the development of hatchery systems for the mud crabs Scylla spp., there is growing interest in evaluation of the quality of hatchery‐reared juveniles relative to wild seed crabs as currently used in aquaculture. Hatchery‐reared and wild‐collected Scylla paramamosain juveniles were stocked either together in ponds or separately. All crabs were tagged with microwire‐coded tags, so that origin could be determined in the mixed groups. Preliminary validation demonstrated that tagging did not affect survival or growth, with a tag retention of 94%. After 106 days of culture, there was no significant difference in survival at harvest between the two sources of crabs. The wild juvenile crabs had a significantly higher initial weight:carapace width (CW) ratio compared with those from the hatchery, indicating a difference in condition. However, where crabs were stocked separately, the hatchery‐reared animals exhibited significantly faster growth than those collected from the wild, both in terms of specific growth rate and CW increase per month. However, in the mixed ponds, where there was competition with wild crabs, there was no significant difference in growth rate between crabs from the two sources. Overall, the results demonstrate that the growth performance of hatchery‐reared S. paramamosain can at least equal that of wild‐collected seed crabs in ponds culture.  相似文献   

10.
A 56‐day feeding trial was conducted to investigate the effect of dietary cholesterol (CHOL) levels on growth performance, body composition and gene expression of juvenile mud crab (Scylla paramamosain). Four isonitrogenous and isoenergetic diets were formulated with 0.4%, 0.8%, 1.2% and 1.6% CHOL supplemented, and the final dietary CHOL concentrations were 0.72%, 1.11%, 1.49% and 1.83% respectively. Each dietary treatment was performed with three replicates (28 crabs per replicate, initial body weight 0.04 g). At the termination of the experiment, although the survival had no statistic difference in all treatments, the mud crabs fed the lowest CHOL diet had the lowest survival rate. The weight gain (WG) of mud crab significantly increased with dietary CHOL level up to 1.11% and then significantly decreased with dietary CHOL level further increased. The total‐cholesterol (T‐CHOL) content in whole body had an increasing trend with the dietary CHOL level increased. Besides, dietary CHOL supplement generally increased the hepatic superoxide dismutase (SOD) activity, and the mud crabs fed diets CHOL1.11 and CHOL1.49 showed significantly higher value than those fed other diets. The hepatic aspartate aminotransferase (AST) activity decreased slightly with dietary CHOL level up to 1.11% and then significantly increased with CHOL level further increased. The mRNA expression of ecdysone receptor (EcR) gene in the eyestalk obviously increased with dietary CHOL level up to 1.11% and then significantly decreased with dietary CHOL further increased. These results suggested that about 1.11% dietary CHOL seem fulfil to maintain good growth performance and healthy condition for juvenile S. paramamosain.  相似文献   

11.
Laboratory experiments were firstly conducted to determine the possibility of modification of the collapsible pot for blue swimming crab Portunus pelagicus by designing appropriate escape vents in terms of shape, position, and size to improve size selectivity by reducing the catch of immature crabs. In laboratory observations, nearly square-shaped vents of 35 mm height and 45 mm length, located at the lower part of the side panel, showed the best performance to allow the escape of immature-size crabs by side-crawling escape behavior through the vents, with L 50% selection carapace length (CL) of 39.1, 44.4, and 48.7 mm CL for 40, 45, and 50 mm vent length, respectively. Comparative fishing trials between conventional and vented pots with vents of 35 × 45 mm size were conducted to examine the crab size and species selectivity. Use of the vented pots was found to reduce the number of immature crabs in the catch from 70.5% to 11.0% on average, while not affecting the catch efficiency of mature-size crabs. The vented pots also had a selective effect for reducing the catch of bycatch species in comparative fishing trials.  相似文献   

12.
Reproductive characteristics relevant to population sustainability were examined for eight abundant invertebrate species caught as byproduct by the Northern Prawn Fishery (NPF) in northern Australia. Slipper lobsters Thenus parindicus and Thenus australiensis differed in their size at maturity, with T. parindicus maturing at smaller size. Both species had similar reproductive seasonality, with most recruitment early in the year (January–March). Our estimates of carapace length (CL) at which 50% of females are mature (CL50) suggest that current management regulations (minimum legal size 52 mm CL) for Thenus are probably adequate for T. parindicus, but suboptimal for T. australiensis. However, T. australiensis only contributes a small proportion to the NPF Thenus catch. This species is likely to be protected as its preferred habitat is coarse substrate and deeper water (>40 m), which does not overlap greatly with the current commercial trawl effort distribution. Uroteuthis squid and Sepia cuttlefishes also varied in size at maturity and reproductive seasonality. Squid and cuttlefish populations are likely to be underexploited based on historical catches. Under current fishing levels, squid stocks appear to be resilient to the opportunistic targeting of spawning aggregations in similar NPF regions over several years.  相似文献   

13.
Predicting growth is critical in aquaculture, but models of growth are largely missing for mud crab species. Here, we present the first model of natural growth in juvenile and adult mud crabs Scylla serrata from East Africa using a stepwise growth function based on data on intermoult periods and growth at moult from field mark‐recapture, pond and laboratory studies. The results showed a sigmoid growth pattern in carapace width and suggest that S. serrata in East Africa will reach 300 g and sexual maturity ~9.9 months after settlement, and a commercial size of 500 g after 12.4 months. Analyses of the literature identified several issues with the common praxis to compare standard growth measures between aquaculture studies with different initial size or growing periods. Using the new growth function to estimate the proportional difference between modelled and obtained growth as an alternative method, we show that growth rates of S. serrata cultured in cage systems, which are dominant in East Africa, was <40% of the estimated natural growth and growth obtained in pond systems. The analysis also indicated that growth rates of S. serrata in Southeast Asia was over 50% higher compared with similar culture systems in East Africa, and that different species of mud crabs had large differences in growth rates. This study shows that growth in the present mud crab aquaculture systems in East Africa is below their expected potential. Further work is needed to identify the factors behind this observation.  相似文献   

14.
A 6‐week study was conducted to determine the effects of different lipid sources in pelleted diets on juvenile mud crab Scylla paramamosain. Five isonitrogenous and isolipidic diets containing 8% level of fish oil (FO), lard (LD), safflower oil (SO), perilla seed oil (PO) or mixture oil (MO; VFO:VSO:VPO = 1:1:1), and a live food of marine bivalve Potamocorbula rubromuscula as the control diet (CF), were fed to groups of 25 juvenile crabs (average initial weight 7.4 g, carapace width 3.5 cm) in triplicate. The results showed that crabs fed MO had the highest survival (P < 0.05). The moisture content was significantly higher in crabs fed LD, SO and PO (P < 0.05). Crabs fed SO exhibited the lowest crude protein and lipid (P < 0.05). Ash contents were obviously lower in LD group (P < 0.05). Highest total lipid in the hepatopancreas and muscle was in LD and FO group respectively. Glucose, total cholesterol and low‐density lipoprotein were higher while high‐density lipoprotein was lower (P < 0.05) in LD group. Tissue fatty acid compositions were consistent with those in diets. FO and MO diets had the same depression effect like CF on fatty acid synthase activity and mRNA expression in the hepatopancreas. The results of this study indicated that FO and mixed oil are suitable for preparation of pelleted diets with better effects for juvenile S. paramamosain compared with live food, and the ratio of n‐6/n‐3 fatty acids in pelleted diets must be <1.  相似文献   

15.
The significant decrease in wild mud crab population highlights the need to manage the resources and domesticate crabs. This paper presents the initial results of the domestication of mud crab Scylla serrata aimed at producing good-quality captive broodstock. The analysis of the genetic structure of the base population was done as a prerequisite for domestication. Adult S. serrata from the northern to southern parts of the Philippines (Cagayan, Camarines, Samar, and Surigao) were obtained for genetic diversity analysis and domestication. Analysis of molecular variance showed that differences in the genetic variability between the four populations were not significant. Moreover, no significant deviation from Hardy–Weinberg Equilibrium was observed in each sample population and even in pooled populations. Body weight was positively correlated with the carapace width. Second spawning occurred 41–46 days after the first spawning and 34 days from second to third spawning. However, there was a decrease in the number of zoea in repeat spawnings. Twenty-four first-generation (F1) families were produced from the four sites. The duration from spawning of the base population (P0) to attainment of broodstock size F1 was 10–14 months. Four second-generation (F2) families were produced after 11–12 months. Up to the F2, crabs tested negative for six viruses: white spot syndrome virus, infectious hypodermal and hematopoietic necrosis virus, gill-associated virus, yellow head virus, Taura syndrome virus, and infectious myonecrosis virus. The reproductive performance of P0 was comparable to the succeeding generations. Several families were obtained from one population in a year. However, due to the cannibalistic behavior of crabs, more space is required for the nursery and grow-out phase. The domestication of S. serrata is the first study done on any mud crab species in the Indo-west Pacific region. The initial results would serve as guide to understand and eliminate the barriers to mud crab domestication. The breeding technology developed from this study will support the production of good-quality seedstock for farming.  相似文献   

16.
Four iso‐nitrogenous and iso‐lipidic diets were designed to investigate the effects of dietary phospholipids (PL) levels (with 0%, 1%, 2%, and 4% PL supplementation) on growth performance, lipid metabolism, and antioxidant capacity in early juvenile green mud crab (Scylla paramamosain). There were three replicates of 28 crabs (initial body weight from 42.02 to 42.44 mg) for each diet treatment, and growth trial lasted for 8 weeks. At the end of the growth trial, there was no significant difference in survival among all treatments. Crabs fed diet with 2% PL obtained highest weight gain (WG) and specific growth rate than other crabs. The molting frequency was not affected by different dietary PL addition. Besides, the contents of whole body lipid and long chain highly unsaturated fatty acids significantly increased with elevating dietary PL levels. In the hepatopancreas, crabs fed diet with 0% PL had significantly higher malondialdehyde concentration than other crabs. And crabs fed diet with 2% PL obtained significantly higher superoxide dismutase activity than crabs fed diets with 0% and 4% PL. Moreover, the mRNA expression of Na+/K+‐ATPase was significantly down‐regulated with dietary PL supplementation over 2%. Based on the second order polynomial regression analysis of WG, 2.37% dietary PL level was the optimal demand for early juvenile S. paramamosain. Moreover, we found crabs fed diet with 2% PL obtained better antioxidant capacity than other crabs.  相似文献   

17.
An experiment was conducted to evaluate the effect of different forms of Artemia biomass as a food source on survival, molting and growth rate of mud crab Scylla paramamosain. Instar 1 crablets with a mean weight of 0.0082 ± 0.0007 g were reared both individually and communally and fed with different diets consisting of fresh shrimp meat (control feed), live Artemia biomass, frozen Artemia biomass and a dried Artemia‐based formulated feed for 40 days. The highest survival was obtained for crablets receiving live Artemia (92.5% and 75.8%) followed by the groups fed with frozen biomass (90.0% and 47.5%), the control feed (72.5% and 24.2%) and the dried Artemia‐based diet (60.0% and 21.7%) for individual and communal cultures, respectively. The intermolt period, the total number of moltings and the growth rate, which were determined on individually reared crabs, showed the same pattern as for survival. The results suggest that crab performance decreased in the following order: live Artemia>frozen Artemia > fresh shrimp meat > dried Artemia‐based formulated feed. Live Artemia biomass proved an ideal feed for nursery of Scylla paramamosain crabs. Frozen Artemia biomass may be an alternative in times of shortage. Our findings illustrate the high potential for local utilization of Artemia biomass in Vietnam for reliable production of mud crab juveniles.  相似文献   

18.
中国东南沿海青蟹线粒体COI基因部分序列分析   总被引：17，自引：1，他引：17  
马凌波 《水产学报》2006,30(4):463-468
对我国东南沿海5个地区的72个青蟹个体的线粒体细胞色素氧化酶亚基I (COI)部分序列序列进行了测定和分析。获得的72个细胞色素氧化酶亚基I (COI)序列可分为12个单倍型，与GenBank中已知的Scylla paramamosain COI序列的相似性达到98%以上，与其它3种 青蟹的差异为7.36%～15.54%。这些序列与S. paramamosain的遗传距离仅为0.00783，但是与S. serrata、S. olivacea和S. tranquebarica〗的遗传距离却分别达到0.11659、0.17812和0.08423。序列特征、遗传距离和系统进化等分析结果都表明本文研究的青蟹为S. paramamosain。结果提示，在进行青蟹属相关研究应当仔细鉴别采集样本的种类。  相似文献   

19.
Treated with combined bilateral eyestalk ablation and maintenance of water temperature at 22.5±1.5 °C, mud crab Scylla paramamosain females with mature ovaries were induced to produce eggs outside the natural spawning season in subtropical southern China. Newly extruded eggs from a crab were incubated in vitro at 10, 15, 20, 25, 27, 30, 35 °C, respectively, and the embryonic development was closely monitored. Abnormal cell division was observed at temperatures 10 and 35 °C. At 15 °C, development remained at the gastrula stage by day 32 post‐spawn, at which time the experiment was terminated. Hatching of in vitro incubated eggs occurred between 20 and 30 °C. An increase in incubation temperature from 20 to 25 °C reduced the incubation duration by 14 days, 2.6 times of that measured for a similar 5 °C increase from 25 to 30 °C. Embryonic development of S. paramamosain was divided into stage 0–10, and the duration of each stage was recorded for each incubation temperature. The information obtained allows accurate prediction of hatching time of female crabs incubated under variable temperatures. Larvae hatched from in vitro incubated eggs were reared to reach first juvenile crab stage and their dry weights were similar to those of larvae hatched naturally.  相似文献   

20.
A scientific observer programme was used to quantify the composition and magnitude of discards in the gillnet fishery for dusky flathead, Platycephalus fuscus (Cuvier), in three barrier estuaries in New South Wales, Australia, during the 2001 fishing season. Regulations only permit the retention of legal‐sized dusky flathead and legal‐sized blue swimmer crab, Portunus pelagicus L., and mud crab, Scylla serrata (Forskål); all other organisms were discarded. Sampling was stratified into two time periods; before and after 1 July 2001 which coincided with the increase in the minimum legal length (MLL) of dusky flathead from 33 to 36 cm total length (TL). Eighty one catches were sampled, yielding 38 finfish species and two portunid crab species. Legal‐sized dusky flathead were the most abundant organism captured, accounting for 23–47% by number and 34–54% by weight of the mean observed catch depending on the estuary and survey period, with a mean catch of 25–59 flathead weighing 13–25 kg per fishing‐night. Species composition and relative abundance of catches differed among estuaries, but not between sampling periods. Predominant bycatch species included legal and undersize blue swimmer crab, sea mullet, Mugil cephalus L., luderick, Girella tricuspidata (Quoy & Gaimard), bream, Acanthopagrus australis (Günther) and yellowfin leatherjacket, Meuschenia trachylepis (Günther). These five species accounted for 82% of total bycatch by number and 71% by weight, pooled across the three estuaries. More crabs were retained than discarded, with retained legal‐size crabs (byproduct) accounting for 16% of total bycatch by number and 13% by weight, with an average of 5–22 crabs weighing 1–6 kg being caught per fishing‐night, depending on the estuary. Overall, 7% of dusky flathead captured (number) were below the MLL of 36 cm and discarded, suggesting the nets as currently configured may be relatively selective in catching legal‐size flathead. However, 41% of dusky flathead were <40 cm TL, indicating that if the MLL for this species is increased to this length as proposed, new nets must be introduced into the fishery. The findings are discussed in terms of making the flathead fishery more sustainable, including alternative management strategies for the fishery.  相似文献   

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