Crab Yield Research Articles

Research on the insurance of swimming crab temperature and salinity index insurance based on Copula function.

Under climate change, the sea surface temperature and salinity change greatly, which poses a considerable threat to sustainable food security. Sea surface temperature and salinity (SST/SSS) are selected to examine the annual output of swimming crab in 24 cities along the eastern China. The Copula-based function was used to construct the probability distribution model of the swimming crab yield with SST and SSS. The pure premium rate of the swimming crab production in these 24 cities are also examined. The results show that 1) There is significant positive correlations between the yield of swimming crab with temperature and salinity over the study area. The only exception is that the correlation between yield of swimming crab and salinity is not significant in the south of study area. 2) The span of the pure insurance premium rate of swimming crab in 24 cities increases rapidly with the increase of the protection level, the maximum span up to 2.04%, and the minimum span is only 1.6%. 3) The distribution of the swimming crab insurance premium rate is various in space. The insurance premium rate of 8 cities in the south of Taizhou is low with the highest premium rate at 5.6%. The insurance premium rate of 16 cities in north of Taizhou is relatively high with the rate between 6%-22%. The research can provide a theoretical basis for the pricing of insurance products for swimming crab in 24 cities in the typical aquaculture areas in eastern China.

Pola Sebaran Kepiting Bakau Dengan Alat Tangkap Bubu Di Perairan Payau Sungai Tanjung Keramat Kecamatan Banda Mulia Kabupaten Aceh Tamiang

Mud crab (Scylla spp.) is a fisheries commodity that is able to adapt strongly to mangrove forests and has a wide distribution area. The wide spread of mud crab is due to the fact that mud crab have a wide tolerance to abiotic factors, especially temperature and salinity. This study aims to determine the composition of the catch and the distribution pattern of mud crab (Scylla spp.) in the waters of the Gampong Tanjung Keramat River, Banda Mulia District, Aceh Tamiang Regency. Sampling was carried out randomly using purposive sampling method at three observation stations including Station 1 (mangrove ecosystem in the river mouth), Station 2 (in the middle of river in the mangrove ecosystem), and Station 3 (in the middle of the mangrove ecosystem). The results showed that the mud crab that were caught using traps consisted of one species, Scylla serrata, with the ratio of male and female mud crab yield is 1.5: 1 (6 males and 4 females). The body size of mud crab varies with the length range of male mud crab, namely 5.2 cm - 8.1 cm, the length of female mud crab is 5 cm - 7 cm. While the range of male mud crab widths is 6.7 cm - 9.6 cm, the width of female mud crab is 5 cm - 8.8 cm. The body weight of male mud crab is 80 g - 350 g, while the body weight of female crab is 90 g - 150 g. Distribution pattern of Scylla spp. located in 3 locations with 9 points of trap/ bubu operation spread over 3 stations. The distribution locations of mud crab are: mangrove ecosystem, river flow in the middle of mangrove ecosystem, and in the middle of river flow of mangrove ecosystem.

Productivity and the complementary use of nitrogen in the coupled rice-crab system

Agricultural intensification has greatly increased yields but has also negatively affected the environment. The coupling of two agricultural systems (i.e., integrated agriculture-aquaculture or integrated crop-livestock) has been proposed as one of the important ways that reduce the negative effects of agriculture on the environment, but large-scale experimental data are lacking. In this study, we examined the coupled rice-crab system, which is a rapidly developing rice-fish system in China. We conducted a field survey across several rice-planting areas and field and mesocosm experiments to determine whether the rice-crab system achieves high yields of both rice and crab without damaging the environment. Our field survey showed that rice yield was not reduced in the rice-crab system across four rice-growing areas although total fertilizer N was reduced compared to rice monoculture. Our field experiment also showed that the rice-crab treatment produced higher rice yield than rice monoculture treatment with the same fertilizer N application, and that the coupled rice-crab treatment had higher crab yield with less crab numbers of precocious maturation than the crab monoculture treatment with the same amount of feed. Both field and mesocosm experiments showed that the rice-crab system did not cause serious feed-N accumulation in the field. Isotope 15N labeling indicated that rice plants used 7.6% of the feed-N. Dual isotope 13C/15N analysis showed that 59.1% of the food consumed by crabs consisted of organisms that thrived by directly using nutrients in the field. This recycling of N within the field explains the low fertilizer-N input and low effluent-N in the coupled rice-crab system. Our results suggest that the coupling of rice with fish production can achieve synergies between food production systems to reduce environmental impacts per unit of production.

Estimation of the lower practical limit of aquatic plant coverage in intensive Chinese mitten crab ( Eriocheir sinensis ) rearing ponds using an unmanned aerial vehicle

Aquatic plants play important roles in the productivity of intensive Chinese mitten crab (CMC) rearing ponds. This study aimed to evaluate the lower limit of aquatic plant coverage (APC) in CMC ponds. A field investigation was conducted and unmanned aerial vehicle was used to estimate APCs. A follow‐on single factor experiment was performed to verify the results and evaluated the efficacy of APC values with 15%, 45%, 65% and 85% APC treatments. Average total nitrogen (0.81 mg/L), total phosphorus (0.06 mg/L), ammonium‐N (0.12 mg/L) and nitrate‐N (0.10 mg/L) met the grade II–IV standards for surface water quality in China in the investigations. Further, the use of an exponential decay model for water qualities and APCs indicated that an effective APC threshold was around 30%, and crab yields (1,536 kg ha–¹ year–¹) significantly decreased by 19.2% if the pond APCs could not reach this threshold. Crab yields were also correlated with crab feed characteristics, and especially the level of fish meat that was used. The single factor experiment for APC again confirmed our APC value threshold via exponential model. Meanwhile, the water quality measurements of the 15% APC treatment were significantly larger than the other APC treatments, but the crab yield, individual weight and carapace length indeed decreased in this single factor experiment for APC. We therefore conclude that the empirical APC level of 60% is preferred, but that smaller APCs could be acceptable in intensive CMC ponds if an APC of at least 30% is maintained.

Using Ipomoea aquatic as an environmental-friendly alternative to Elodea nuttallii for the aquaculture of Chinese mitten crab.

Elodea nuttallii is widely used in Chinese mitten crab (CMC) rearing practice, but it is not a native aquatic plant and cannot endure high temperature. Thus, large E. nuttallii mortality and water deterioration events could occur during high-temperature seasons. The aim of this study was to identify the use of local macrophytes in CMC rearing practice, including Ipomoea aquatic and Oryza sativa. A completely randomized field experiment was conducted to investigate the crab yield, water quality, bacterioplankton community and functions in the three different systems (E. nuttallii, I. aquatic, and O. sativa). Average crab yields in the different macrophyte systems did not differ significantly. The I. aquatic and O. sativa systems significantly decreased the total nitrogen and nitrate-N quantities in the outflow waters during the rearing period compared to the E. nuttallii system, and the I. aquatic and O. sativa plants assimilated more nitrogen than the E. nuttallii plant. Moreover, the significant changes of bacterioplankton abundances and biodiversity in the three systems implied that cleanliness of rearing waters was concomitantly attributed to the differential microbial community and functions. In addition, principle component analysis successfully differentiated the bacterioplankton communities of the three macrophytes systems. Environmental factor fitting and the co-occurrence network analyses indicated that pH was the driver of bacterioplankton community structure. Functional predictions using PICRUSt (v.1.1.3) software based on evolutionary modeling indicated a higher potential for microbial denitrification in the I. aquatic and O. sativa systems. Notably, the O. sativa plants stopped growing in the middle of the rearing period. Thus, the I. aquatic system rather than the O. sativa system could be a feasible and environmental-friendly alternative to the E. nuttallii system in CMC rearing practice.

Rice-crab coculture to sustain cleaner food production in Liaohe River Basin, China: An economic and environmental assessment

Irrational rice planting–breeding modes may result in serious ecological and environmental issues and unsustainable agriculture. In this study, economic benefits combined with emergy analysis were used to evaluate the environmental and economic performances of three rice production modes, namely, rice monoculture (RM), conventional rice-crab (CRC) and optimized rice-crab (ORC) modes, in Panjin City surrounding Liaohe River Basin in Northeast China. Rice and crab yields of ORC were increased by 8%–12% and 9% compared with those of RM and CRC modes, respectively. The value-to-cost ratio, economic benefits density and benefit-cost ratio of ORC increased by 46%–51%, 55%–80% and 59%–66%, respectively, compared with those of RM and CRC modes. The results of emergy analysis indicated that the production efficiency of ORC mode increased by 21%–45% compared with that of CRC mode according to the unit emergy values though slightly lower than that of RM mode. Compared with those of RM and CRC modes, renewable fraction and emergy sustainability index increased within the ranges 7%–28% and 4%–36%, respectively, and environmental loading ratio decreased by 9%–34%,. Considering ecological and economic effects, ORC mode was conducive to improve the sustainability and economic viability of rice production in Liaohe River Basin. Labor and service, fertilizer utilization, and forage input play an important role in emergy investment structure among the three modes, thereby suggesting that appropriate allocation of labor should be implemented to improve the labor efficiency and government should increase subsidies for fertilizer and agricultural machinery. Moderate industrial integration and large-scale operation modes, efficient utilization of local resources, whereas reducing external inputs are suggested to considerably improve the environmental performance and sustainable development capacity of the rice planting–breeding mode.

Does the wild-caught Chinese mitten crab megalopae perform better than the hatchery-produced seed during the juvenile culture?

Although wild Yangtze Eriocheir sinensis juveniles (coin‐sized seed) have better culture performance than the pond‐reared juveniles during the adult crab culture stage, the culture performance of wild‐caught megalopae (WC) remains unknown. Therefore, this study was designed to compare the growth, survival rate, crab yield, feed conversion rate (FCR), precocity, final weight and size distribution between WC and hatchery‐produced megalopae (HP) during the juvenile culture stage. Wild‐caught megalopae had significantly higher body weight, weight gain rate (WGR) and specific growth rate (SGR) during 0–4 weeks but lower WGR and SGR than HP during 4–8 weeks (p < .05). Although WC had a significantly lower survival rate and yield of normal juvenile crabs than HP, total yields of normal juveniles and precocious crabs were similar. Wild‐caught megalopae had a significantly higher precocious rate and yield of precocious crabs than HP (p < .05). Regardless of sex, no significant differences were found in the gonadosomatic index (GSI), hepatosomatic index (HSI) and final weight of normal juveniles and precocious crabs between WC and HP. As for the size distribution of normal crabs, WC had a higher percentage of small female juveniles (<3 g) but a lower proportion of middle size ranges (3–5.99 g and 6–8.99 g) than HP for females (p < .05), and there was no significant difference for males. In conclusion, wild megalopae of the Yangtze E. sinensis had worse culture performance than the hatchery‐produced seeds; therefore, wild megalopae would not be recommended for commercially juvenile culture of E. sinensis.

Distribusi Spasial Rajungan (Portunus pelagicus) pada Musim Timur di Perairan Pulau Lancang, Kepulauan Seribu

A study was carried out to assess the present status of blue swimmer crab (Portunus pelagicus) in Lancang Island, incorporating identification of fishing ground, also measurement of environmental condition and crab biometry. Monthly catch assessment was performed on JuneSeptember 2015 at three landing bases using structured questionnaire and morphometric sampling of minimum randomly selected 30 crabs. Bathymetric survey was conducted to produce depth-contoured maps combined with certain oceanographic parameters (sea surface temperature, salinity, water clarity, total suspended solids, dissolved oxygen, and nitrate-NO3) measured at 15 sampling sites. A grid map was produced to identify key areas of crab fishing grounds, recruitment habitat, and spawning habitats. During southeast monsoon, main fishing ground was distributed in the western and southern part of Lancang Island (grid C3, C4, and D5). In general, crab yields were dominated by female (66.9%) and 43.8% of them were bearing eggs. Four size classes were determined from frequency distribution of carapace width (Class 1 = 7.0-10.6 cm; Class 2 = 10.7-14.2 cm; Class 3 = 14.3-17.8 cm; and Class 4 = 17.9-21.5 cm), with Class 2 as the most prominent catch. Referring to ontogenetic migration trait of the species, presumed recruitment habitat for blue swimmer crab in Lancang Island is located at A6, where abundant juveniles were harvested in the area with strong oceanic influence and depth range of 24-30 m. Spatial coherence on the distribution of bearing egg female with several environmental parameters (sea surface temperature, salinity, and dissolved oxygen) indicates strong estuarine influence is required for crab spawning habitat at C3 and

Sustainable fisheries in shallow lakes: an independent empirical test of the Chinese mitten crab yield model

Next to excessive nutrient loading, intensive aquaculture is one of the major anthropogenic impacts threatening lake ecosystems. In China, particularly in the shallow lakes of mid-lower Changjiang (Yangtze) River, continuous overstocking of the Chinese mitten crab (Eriocheir sinensis) could deteriorate water quality and exhaust natural resources. A series of crab yield models and a general optimum-stocking rate model have been established, which seek to benefit both crab culture and the environment. In this research, independent investigations were carried out to evaluate the crab yield models and modify the optimum-stocking model. Low percentage errors (average 47%, median 36%) between observed and calculated crab yields were obtained. Specific values were defined for adult crab body mass (135 g/ind.) and recapture rate (18% and 30% in lakes with submerged macrophyte biomass above and below 1 000 g/m2) to modify the optimum-stocking model. Analysis based on the modified optimum-stocking model indicated that the actual stocking rates in most lakes were much higher than the calculated optimum-stocking rates. This implies that, for most lakes, the current stocking rates should be greatly reduced to maintain healthy lake ecosystems.

Occurrence of the blue crab Callinectes sapidus, Rathbun, 1896, and its fisheries biology in Bardawil Lagoon, Sinai Peninsula, Egypt

This study reports the yearly occurrence and the biology of fisheries belonging to the blue crab Callinectes sapidus (Rath.) in the catch yield of Bardawil Lagoon (BL) in Sinai Peninsula, Egypt over the past 15years. The study shows that between the years 2000–2015 the crustacean fishery increased (pooling both shrimp and crabs) with fluctuations from 40% to 63% of the total production of the lagoon. The crab yield, during this period, increased from 19% to 42% of the total lagoon production. Moreover, the results show that the crab catch of BL is composed mainly of two crab species Portunus pelagicus (L.) and C. sapidus (Rath.). The latter is considered the most dominant in the crab yield with 85% of the total crab production, while C. sapidus is only 15%. The size of C. sapidus ranged between 65 and 155mm (carapace width) with a dominance of the class size 105mm. Furthermore, the ratio of C. sapidus males to females was in favor of males. The regression of width–length relationship showed a marked deviation from the isometric growth. Length–width and body weight regressions also showed deviations from the isometric growth and the analysis of the covariance. This indicates the significant difference between sexes in respect to length weight relationship. The interrelationships between width–length and propodus length and depth of males and with abdomen in females of C. sapidus suggested that in most conditions the relationships were positive and highly significant. This study shows the first insights on the status of C. sapidus in Bardawil Lagoon, Egypt.

Comparison of the culture performance and profitability of wild-caught and captive pond-reared Chinese mitten crab (Eriocheir sinensis) juveniles reared in grow-out ponds: Implications for seed selection and genetic selection programs

Abstract The Chinese mitten crab, Eriocheir sinensis, is a commercially important freshwater crab with a high market value in East Asian countries. The farming of E. sinensis has undergone rapid development in China. Generally, ponds are stocked from two seedstock sources, captive pond-reared juveniles (coin-sized seed, PR) or wild-caught seedstock of E. sinensis (WC). Anecdotally, WC stocks are preferred as they are thought to perform better in culture compared with PR stocks. However, the availability and low cost of PR seedstock have resulted in this becoming the dominant seedstock for production, despite a lack of selective breeding programs. We compared the growth, gonadal development, survival, crab yield, feed conversion rate (FCR), size distribution, and profit between WC and PR populations of E. sinensis seedstock from the Yangtze basin that were cultured in commercial-sized production ponds. The PR had a higher body weight, weight gain rate (WGR), and specific growth rate (SGR) than the WC during the mid-period of the study (July to August) whereas WC had a higher WGR and SGR than PR during the latter part of the study (September to October). Regardless of sex, PR commenced their puberty molt and gonadal development earlier than WC, which resulted in PR having a significantly higher gonadosomatic index (GSI) than WC during the periods between September and November. WC had the higher survival and crab yield, and a lower FCR at the end of the study, though the differences were not significant. However, the proportion of larger sized male or female adults was higher in WC (male ≥ 225 g/crab; female ≥ 125 g/crab) than in PR. The cost of purchasing and feeding WC seedstock was greater than that of the PR seedstock, however the return-on-investment (ROI) for WC seedstock was higher because of higher yield and the higher price for larger crabs. Despite having better culture performance and greater ROI from stocking WC crabs, this source of seedstock is not sustainable for the E. sinensis farming industry because of the variable quantity, high seed cost, and very limited natural seedstock resources in the Yangtze River. Thus, there is a need for genetic-improvement breeding programs focused on the establishment of captive stocks to obtain desirable traits, such as larger harvest size, low FCR, and delayed onset of maturity in E. sinensis.

The effect of stocking density of Chinese mitten crab Eriocheir sinensis on rice and crab seed yields in rice–crab culture systems

Normally Chinese mitten crab Eriocheir sinensis were cultured for 2 years, 1 year is cultured from crab larvae to seeds or button sized crab in ponds, tanks or rice fields, the another year is cultured from seeds to market size in ponds, reservoirs or other waters. The present study was conducted to determine the effect of stocking density (0, 3.75, 15, 30 and 60 inds. per m2, respectively) of Chinese mitten crab larvae on rice and crab seed yields in rice–crab culture systems using land-based enclosures (4 m×7 m, with three replicates for each stocking density) at the Panjin Guanghe Fisheries Co. Ltd, in the Liaohe Delta, China. Zoobenthos biomass, production of crab and rice paddy, and economical profit among the treatments were determined. The experiment showed that zoobenthos biomass in rice–crab culture systems was relatively variant and not significantly correlated to these stocking density. The biomass of aquatic plant declined significantly with increasing stocking density. Specific growth rates (SGR) and survival rates of the crab were significantly higher at the lower stocking density (P<0.05); in addition, the ratio of precocious crab and total crab significantly increased with the stocking density increasing (P<0.05); There were not significant effect of presence of crab on yields of rice straw and rice paddy (P>0.05). Net crab yield and net profit were the highest at the 15 treatment (P<0.05), however, the net profits among 3.75, 15 and 30 treatments did not show significant difference (P>0.05) economically. Based on the observations above, a stocking density of 3.75 to 30 inds. per m2 was considered reasonable in rice–crab culture system.

Stocking models of Chinese mitten crab ( Eriocheir japonica sinensis) in Yangtze lakes

The farming of Chinese mitten crab, a quality aquatic product in China and neighbouring Asian countries, has been developing rapidly in China since last decade. It reached a total yield of 3.4 × 10 5 tonnes in 2002. Due to the successive over-stocking year after year, many lakes in the mid-lower Yangtze Basin, the main farming area, are under deterioration, leading to a reduction of crab yield and quality, and, subsequently, a loss of farming profits. Aiming at a normal development of crab culture and the sustainable use of lakes, an annual investigation dealing with lake environmental factors in relation to stocked crab populations was carried out at 20 farms in 4 lakes. The results show that the submersed macrophyte biomass ( B Mac) is the key factor affecting annual crab yield (CY). Using the ratio of Secchi depth to mean depth ( Z SD / Z M), an easily measured parameter closely correlated to B Mac, as driving variable, 10 regression models of maximal crab yields were generated ( r 2 ranging 0.49–0.81). Based on the theory of MSY (Maximum Sustainable Yield), in combination with body-weight (BW) and recapture rate (RR) of adult crabs, a general optimal stocking model was eventually formulated. All models are simple and easy to operate. Comments on their applications and prospects are given in brief.

On changing the size selectivity of fishing gear for Chionoecetes opilio in the Japan Sea.

At present, management agencies enforce size limit restrictions in the Japan Sea which prevent the landing of male C. opilio less than 9cm carapace width. Since Danish seiners cannot avoid capturing illegal sized crabs, a large number of the crabs are discarded at sea in the hope that they will eventually recruit into the legal size. However, catches of this crab have declined accom-panied by a reduction in average crab size. We demonstrate that crab yield can be increased by switching the gear to long line traps with 15cm streched mesh. Thus, by changing the size selec-tivity of the gear, crabs smaller than 9cm carapace width can be protected from the fishery.

Preliminary Report on the Culture of the Stone Crab

ABSTRACTMass‐culture experiments of stone crab (Menippe mercenaria) were successfully performed in 1970. Ovigerous female stone crabs were obtained from traps set in Biscayne Bay, Miami, Florida. The females were held separately in indoor aquaria. A maximum of 10 ovipositions (spawnings) within one inter‐molt phase were observed for a single female over a 120‐day period. During this period, the embryonic duration of the eggs was approximately 10 days at temperatures of 29 to 30 C, and the period between larval hatching and the female's next oviposition was 2 to 3 days.The duration of the larval period (five zoeal stages and one megalopal stage) was 14 days at temperatures ranging between 30.5 and 32.0 C, with salinity in excess of 30 ppt; 18 days were required at temperatures ranging from 28.0 to 30.0 C in the same salinity range. The time requirements in mass culture were found to be greatly reduced compared with individual compartment culture methods, which normally would take 20 to 21 days.Experiments using two different filtered seawater media were performed. In one, seawater was filtered through a 165 μ mesh screen; in the second seawater was filtered through a fine dacron wool filter. Results were similar.Initial larval culture media was stabilized by adding Chlorella to the culture seawater. The early zoeae were fed with separately cultured rotifers (Branchionus plicatilis) and Artemia nauplii. Only Artemia nauplii were provided for the late zoeal stages. The food for megalopae and juveniles was chopped fish and squid. To reduce cannibalism in the megalopal stages a screen‐ring was installed. This screen also provided a good substratum for settling.The maximum young crab yield was about 360 second‐stage crabs in a 200 1 plastic container, and 960 second‐stage crabs in a 600 1 capacity wooden tank. The best survival rate from hatching to the first crab stage was about 9%. Mortality occurred primarily in the magalopal stage.A promising future for stone crab culture is indicated from the growth rates obtained beyond the juvenile crab stage. Individuals reared separately in the indoor aquaria showed rapid growth. The most rapidly growing individual reached a carapace length of 9.1 cm and a weight of 236 g in 7 months from hatching. Approximately 10 molts are required to reach this size from the first crab stage. The color pattern of the cultured crab was noticeably different from that found in nature.