Swimming Crab Research Articles

Morphometric Differentiation of the Swimming Crab Portunus sanguinolentus (Herbst, 1783) Populations in East Asia: Implications for Stock Identification and Management

Morphometric disparities were employed to characterize the geographical variations in and elucidate the phylogeography of Portunus sanguinolentus in East Asia. In this study, a comprehensive assessment was undertaken based on measurements from 833 individual crabs. These crabs were sampled from eight distinct locations, namely Kyushu (KS), Fuzhou (FZ), Yilan (YL), Xiamen (XM), Tainan (TN), Hong Kong (HK), Vietnam (VN), and Singapore (SG). Twelve morphometric measurements were standardized based on size using the allometric method. A cluster analysis and a canonical variate analysis (CVA) were then conducted for a data analysis. Randomization tests were subsequently performed to validate the morphometric differences observed among the groups. The analytical results classified the eight sampled populations into at least two distinct clusters. The first cluster included three samples from China (specifically FZ, XM, and HK), while the second cluster consisted of samples from East Asia (including KS, YL, TN, VN, and SG). The CVA revealed a tripartite division into three groups: the mainland China group (FZ, XM, and HK), the Kuroshio group (KS, YL, and TN), and the Southeast Asia group (VN and SG). The observed morphometric variations between these broad groups were statistically significant for both genders. These differences may be attributed to evolutionary origins, geographical events, or environmental adaptations. This study highlights the effectiveness of morphometric techniques in providing comprehensive insights into species delimitation and philogeographic relationships.

Application prospect of replacement of fish meal with spray-dried egg meal in diets for swimming crab (Portunus trituberculatus)

An 8-week feeding trial was conducted to evaluate the effects of replacing fish meal with spray-dried egg meal (SEM) on growth performance, anti-oxidative capacity, mTOR pathway, and cholesterol metabolism in juvenile Portunus trituberculatus. The results showed that the highest percent weight gain was observed in crabs fed diet with 10% replacement of fish meal with SEM. Essential amino acids in the muscle and hepatopancreas significantly decreased with the increase of dietary replacement levels of fish meal with SEM. The lowest content of MDA in hepatopancreas was occurred at those fed diet with 40% replacement of fish meal with SEM, the activities of T-AOC, GSH-PX and content of GSH in hepatopancreas significantly increased with dietary SEM replacement fish meal increasing from 10% to 50%. The expression of akt, eif4e1a, eif4e2, eif4e3, and 4ebp1 significantly up-regulated, however, the expression of tor was showed significantly linear down-regulated, and the highest expression of akt, eif4e2 and 4ebp1 were found in crabs fed diet with 20% replacement of fish meal with SEM, the highest expression of eif4e1a was observed in those fed diet with 10% replacement of fish meal with SEM, the highest expression of eif4e3 was occurred in crabs fed diet with 30% replacement of fish meal with SEM. In cholesterol metabolism, the expression of abcg1 and lrp2 significantly down-regulated and the expression of npc1 significantly up-regulated with increase of replacement level of fish meal with SEM. The content of T-CHO in hemolymph and hepatopancreas significantly linear increased. In conclusion, based on quadratic broken-line regression analysis of PWG against the dietary replacement of fish meal with SEM, the optimal replacement level of fish meal with SEM was estimated to be 15.94% for juvenile swimming crab.

Effects of spatial–temporal conditions and fishing-vessel capacity on the capture of swimming crabs by using different fishing gear around the waters of Taiwan

Context Swimming crab is a vital fishery resource and a valuable source of income in the southern East China Sea, but it lacks management strategies, especially when using different fishing gear. Aims This study aimed to determine the effects of spatial–temporal conditions and vessel capacity on swimming crabs by using different fishing-gear types in the Taiwan Strait (TS). Methods We used generalised linear mixed models (GLMMs) to investigate data from Taiwanese vessels (2011–2019) on how spatial–temporal conditions and vessel capacity affected the catch of swimming crabs when using trawls, gill-nets and traps. Key results The results showed that the traps (>80.0%) caught more swimming crabs in the TS than did the gill-nets (6.6%) and trawls (8.0%). Additionally, the GLMM analysis showed that Charybdis feriatus, Portunus pelagicus and Portunus sanguinolentus catches by traps and trawls were significantly affected by different fishing locations, climate events, work hours and vessel sizes. However, for gill-nets, spatial–temporal conditions and vessel capacity did not affect the catch of C. feriatus. Conclusions Monitoring fishing efforts and environmental factors is vital to understanding their impacts on marine ecosystems. Implications These findings enable future sustainable crab fishing through harvesting strategy planning, ecosystem management and spatial–temporal governance.

A Concept of Open-Closed Season Approach for Indonesian Blue Swimming Crab (Portunus Pelagicus) Management on the North Coast of Java

The open-closed season approach has not been widely used in fisheries management in Indonesia, including blue swimming crab (BSC) fisheries that created ecological and economic balance. This research aims to illustrate the characteristics of BSC fishers, examine the application of the concept of the open-closed season in blue swimming crab fisheries, and predict the sustainability of fishermen's livelihoods. Data collection was conducted in 2020 and 2022 in four regencies: Rembang, Demak, Cirebon, and Lampung. However, Lampung is excluded in 2022. The primary data were obtained from structured questionnaires sent to 520 fishermen and 63 mini plants and collectors, then analysed by descriptive analysis, Likert scale, and business sustainability index. The findings showed that blue swimming crab fishing characteristics at four research sites showed different conditions. Working as fishermen cannot contribute sufficiently to improving the household economy. The factor influencing the blue swimming crab fishing business is the size of the fishing boats. The open-closed season (OCS) policy is worthy of short-term goals consisting of fishermen's welfare and business justice in business actors and long-term goals, namely the sustainability of blue swimming crabs. Institutional schemes are proposed for the OCS model to maintain the sustainability of resources and businesses.

Bioaccumulation of zinc by Portunus pelagicus: Nuclear application techniques that use radiotracer 65Zn to study influence of concentration of Zn in seawater

Zinc (Zn) is an essential trace metal, but also a potential toxicant to aquatic organisms. Zinc is one of the toxicants from various industrial and domestic activities whose waste is directly discharged into water. One of the marine organisms used as an indicator of pollution is the blue swimming crab (Portunus pelagicus). Bioaccumulation studies of Zn in Portunus pelagicus from Jakarta Bay were conducted in a radiotracer laboratory. Laboratory experiments were done to study the uptake and release of 65Zn radioisotope in Portunus pelagicus. The experiments conducted were biota collection, acclimatization, bioaccumulation, and elimination. This study was to determine the relationship between the amount of 65Zn released into the aquatic environment and its effect on Zn bioaccumulation ability and radiation dose received by Portunus pelagicus. Biokinetics parameters, such as concentration factors CF, uptake rate constant ku, elimination rate constant ke, and concentration factor steady state (CFss) were investigated. The results showed that an increase in concentration would decrease the rate of absorption and rate of elimination, and that the concentration factor CF values ​​varied from 7.82 - 60.62 ml.g-1 in Portunus pelagicus. The concentration factor at steady-state Zn was 25.55-59.47 ml.g–1, which is influenced by the concentration after 6 days of exposure. The depuration rate was observed to be high, with a value of retention 34.33 - 78.88 % of 65Zn absorbed by Portunus pelagicus, which was absent 7 days after exposure. Highlights Laboratory experiments lasting 14 days showed that Portunus pelagicus has the ability to accumulate the heavy metal zinc (Zn) from the environment and release it back into the water The highest bioaccumulation kinetics of zinc (Zn) metal in Portunus pelagicus during the 7-day experiment occurred at a contaminant concentration of 0.5 ppm with an absorption constant (ku) value of 0.7838 d-1 and a release constant value (ke) of 0.0892 d-1 Portunus pelagicus concentration factor (CF) has a moderate value and the smallest uptake constant (ku) and elimination constant (ke) value compared to other biota

Identification of candidate genes associated with body weight in swimming crab (Portunus trituberculatus) according to conjunctive analyses of BSA-seq and RNA-seq

The swimming crab (Portunus trituberculatus) is a valuable crustacean species extensively cultivated in China, owing to its fast development, palatability, and rich nutrition. However, the genetic factors regulating its growth remain elusive, impeding the progress of breeding initiatives for this economically important species. In this study, we combined bulk segregation analysis sequencing (BSA-seq) and transcriptome sequencing (RNA-seq) to identify potential candidate genes related to the body weight of P. trituberculatus using a full-sib family. BSA-seq successfully identified five candidate intervals on chromosomes 31, 38, and 47, spanning a total length of 9.76 Mb, which encompassed 137 annotated genes. By conducting RNA-seq analysis on swimming crab individuals in two extreme weight groups, 1581 genes were mined as differentially expressed genes (DEGs), involving 357 up-regulated and 1224 down-regulated genes. GO enrichment analysis demonstrated that DEGs were significantly enriched in proteolysis, obsolete oxidation-reduction process, nucleus, cytoplasm, molecular function, and metal ion binding. KEGG enrichment analysis showed that the proteasome signaling pathway could play a prominent role in the growth difference of P. trituberculatus. The conjunctive analyses of BSA-seq and RNA-seq led to the identification of eight critical DEGs, including peripheral plasma membrane protein CASK (CASK), cytoplasmic dynein 2 heavy chain 1 (Dyh1b), RNA-binding protein 5 (Rbm5), structural maintenance of chromosomes protein 3 (Smc3), hemicentin-2 (Hmcn1), A-kinase anchor protein 13 (Akap13), zinc finger MYM-type protein 2 (Zmym3), and extracellular matrix protein FRAS1 (Fras1), which exert influence over the growth of P. trituberculatus. This study not only enhances our understanding of the molecular mechanism governing the growth of P. trituberculatus but also provides valuable insights for future aquaculture programs aimed at selective breeding of this species.

Chitin Extracted from the Shell of Blue Swimming Crabs (Portunus pelagicus Linn.) Inhibits NF-kappaB p65 in Ethanol-Induced Gastric Ulcerative Wistar Rats.

Peptic ulcer disease is generated by the activation of NF-kappaB activity. A recent clinical study reported a significant increase in NF-kappaB2 gene expression in 79 samples of peptic ulcer patients compared to the control group. Moreover, the deacetylated chitin could alter the translocation of NF-kappaB p65 to the nucleus. Considering this, our work aims to explore the effect of chitin extracted from the shell of blue swimming crabs (Portunus pelagicus Linn.) towards NF-kappaB p65 levels in ethanol-induced gastric ulcerative Wistar rats. The shells are found abundantly as the waste of seafood processing in the northern part of West Java, Indonesia. In this study, chitin extraction was carried out using the microwave-assisted extraction method by employing choline chloride (C5H14ClNO) and DL-malic acid (C₄H₆O₅) as the solvents. The inhibitory activity assay of chitin on the expression of NF-kappaB p65 was performed by using Western blot. The extraction yielded a good quality of chitin with a deacetylation degree of 30.8026%, molecular weight of 3.35 × 105 Da, and a negligible heavy metals level. Moreover, chitin extract at doses of 150, 300, and 600 mg/kg BW significantly reduced the percentage of gastric ulcer index compared to the negative control group. Meanwhile, chitin extract at doses of 300 and 600 mg/kg BW significantly inhibited NF-kappaB expression compared to the negative control group. Histopathological examination demonstrated a decrease in the number of necrotic cells and fat degeneration in the gastric mucosa and an increase in normal cells. Taken together, chitin extract obtained from the shells of blue swimming crabs may be able to prevent gastric ulcers induced by ethanol via the inhibition of NF-kappaB p65; however, further studies are needed to verify its anti-ulcerative properties.

TWO IN ONE: REPORT OF TWO EPIBIONTS GROUPS ON THE Callinectes bocourti A. MILNE-EDWARDS, 1879 (DECAPODA: PORTUNIDAE) FROM THE AMAZON PROVINCE

Case studies reporting crustaceans acting as basibionts for a wide range of encrusting invertebrates are widely observed in the literature. For swimming crabs of the genus Callinectes, these commensal interactions are commonly observed in estuaries and coastal zones worldwide. Despite the broad distribution of Callinectes bocourti A. Milne-Edwards, 1879 in Amazon province, the occurrence of epibiosis for this species in the area is rarely reported. Herein, we report the double occurrence of epibiont groups: the mollusks Ostrea puelchana d’Orbigny, 1842 and Sphenia fragilis (H. Adams & A. Adams, 1854) and the barnacles Amphibalanus improvisus (Darwin, 1854) and Chelonibia testudinaria (Linnaeus, 1758) from the new host C. bocourti, collected from the Amazon province, Brazil. The specimens of C. bocourti showing epibionts were collected manually in low tide, with a baited trap called “puçá”, in the region of Curuçá River mouth, state of Pará (0°40’3,705”S, 047°54”43,405”W). We observed five specimens of C. bocourti showing double cases of epibiosis, composed by mollusks and crustaceans sharing the same area. In addition, here, we expand the range extension of the mollusk O. puelchana and we register the presence of the invasive species barnacle A. improvisus from the state of Pará, being this last species, reported as parasite adhered in carapace and branchial chambers of the host.

Syndication of sink-source and area-based resource management as a remedy to sustain a small-scale fishery: The case study of blue swimming crab fishery from Sri Lanka

Tropical small-scale fisheries (SSF) have become more vulnerable to over-exploitation due to: delayed alarming stock status, consequences of implementing deprived management strategies, data-poor scenarios, ambiguous assessment approaches and failures in a comprehensive understanding of the context of specific resource users. Hence, the current study on the blue swimming crab (BSC) fishery off the northern coast of Sri Lanka (September 2017 to November 2018), reveals the evidence of the SSF's requirement for a precise management and decision approach for sustainability. Therefore, here we intended, to evaluate The TropfishR package of the electronic length frequency (ELEFAN) method with new optimization techniques for data-limited fisheries analysis with length frequency (LFQ) data. Further multivariate techniques were used for the follow-up analysis. Results of LFQ data obtained through scrutinized ELEFAN methods and followed-up analysis showed that all studied fishing grounds are overexploited (E > 0.5) due to the “effort-creep” in post-war context and higher economic demand of BSC, which were collectively drive the prevailing behaviour of fishers. Further, due to cultural constraints such as caste-based gear choices and fishing ground choices, the small and immature stages of BSC become more susceptible to gears with low selectivity, which frequently operated in the estuary (ES) and shallow coast (SC). So under this multi-gear, complex SSF scenario banning or restricting the harmful gears becomes socially impossible. Hence, area-based management through a sink-source approach that characterizes the fishing ground with respect to the gear, seems to be promising. Therefore, we conclude that through a such robust approach, we could able to replenish a similarly overfished fishery scenario in the SSF.

Human health risk assessment for consumption of microplastics and plasticizing substances through marine species

A special characteristic of MP (microplastics) in the ocean is they may act as carriers of additives specific to the plastic materials used in their manufacture, such as plasticizers, among which Bisphenol-A (BPA), bis (2-ethylhexyl) phthalate (DEHP), dybuthyl phthalate (DBP). Both MP as the plasticizers were searched in composite samples of mangrove cockle (Anadara tuberculosa), Stolzmann's weakfish (Cynoscion stolzmanni) and arched swimming crab (Callinectes arcuatus). Extraction of MP was done through physical-chemical techniques and identification was carried out employing the techniques of light microscopy, energy dispersive spectrometer (EDS), scanning electron microscope (SEM) and Raman spectroscopy; the sizes of MP obtained were between 0.5 μm and 106 μm, the following average results being obtained: for Arched swimming crab 4.0 ± 1.0 MP/g; mangrove cockle 3.3 ± 2.9 MP/g; and for Stolzmann's weakfish, the average was 2.4 ± 1.3 MP/g; the most observed shapes were fibers and irregular segments; the most identified MP was polyethylene terephthalate (PET). Regarding extraction and quantification of plasticizers, the extraction stage was carried out using QuEChERS tubes; and the identification and quantification with gas chromatography coupled to a mass spectrometer (GC-MS). Regarding the plasticizing substances, DEHP was found in detectable levels in all the samples; BPA was found in 84% of the composite samples analyzed; DBP was found in 50% of them, of the analyzed samples 34% were positive for the 3 analytes. The dietary exposure of people to plasticizers was calculated and for BPA the exposure obtained was compared with respect to the TDI (tolerable intake dose) for pregnant women and the new TDI proposed by EFSA in 2021 according to the estrogenic effect of this substance in the fetus. The objective of the work was to determine if a relationship could be established between both PM and plasticizers, which gave a positive relationship.

Chronic ammonia toxicity disturbed energy homeostasis and damaged the hepatopancreas of swimming crab Portunus trituberculatus

Ammonia is toxic to aquatic animals and its chronic effects on the swimming crab Portunus trituberculatus is still not fully understood. Therefore, we conducted this study to detect the responses of energy metabolism of crabs to chronic high environmental ammonia (HEA) exposure by exposing them to HEA (5 and 15 mg·L−1) for 15 d and subsequently recovering in natural seawater for 7 d. Then we analyzed the glucose and lactate content, ATPases activities and the expression of the genes involved in energy homeostasis. Besides, glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), alkaline phosphatase (AKP) activity and histological changes were assayed to determine the HEA-induced hepatopancreas damage. Results showed a HEA dose- and exposure time-dependent mortality and hepatopancreas damage. This was accompanied by a loss of energy homeostasis as indicated by the significant increase of AMP/ATP ratio and genes expression involved in AMPK pathway (P < 0.05). While indices such as HMGCR expression, glucose content and ion related ATPases demonstrated the energy dishomeostasis might be related with the inhibitory effect of chronic HEA on energy regulatory capacity especially when HEA approached 15 mg·L−1. In summary, chronic HEA can seriously damage hepatopancreas structure and function of energy metabolism in P. trituberculatus, and this deleterious effect could even not be completely repaired in a short recovery time.

Sensory Value, Proximate Analysis, Amino Acid and Fatty Acid Profile of Steamed and Boiled Blue Swimming Crab (Portunus pelagicus)

Whole blue swimming crab (Portunus pelagicus) is usually steamed or boiled before taking the meat for canning. The choice of the cooking process between steaming or boiling can determine the characteristics of blue swimming crab (Portunus pelagicus) meat. This study aims to determine and compare the flavor profile of blue swimming crab cooked by steaming and boiling. Whole blue swimming crab were steamed and boiled for 15 minutes at 100°C respectively. The cooked blue swimming crab meat was then tested for yield, sensory value, proximate analysis, amino acid and fatty acid profile. The results showed that the steaming process gave higher yields and sensory value than boiled blue swimming crab.

Microplastics in the Gastrointestinal Tract of Blue Crab (Portunus pelagicus) Caught by Bandaran, Bangkalan Fishermen at Different Sizes

Microplastics are plastic waste that is degraded into small sizes that float in water bodies and can be ingested by aquatic biota. This study aims to determine the shape, color, and abundance of microplastics in the digestive tract of blue swimming crab (Portunus pelagicus) caught by fishermen in Bandaran Village, Bangkalan at different sizes. Swimming crab sampling was carried out 3 times with different sizes, namely small, medium, and large. Identification of microplastics using a solution of H2SO4 and H2O2 with a concentration of 30% with a ratio of 3:1. Microplastic forms found include fiber, fragments, and films. The highest abundance of microplastics was found in large crabs with a value of 3.13 particles/g. The simple regression test results obtained a relatively small R² value of 0.0003 meaning that the size of the crab has a very small correlation with the abundance of microplastics in the digestive tract.

Long-term in-vitro culture and subculture of the hemocytes of swimming crab Portunus trituberculatus

Long-term in-vitro culture and subculture of the hemocytes of swimming crab Portunus trituberculatus

Evolution of the Food Web in Bandon Bay, the Gulf of Thailand: Ten Years of the Blue Swimming Crab Stocking Programme.

The ecosystem of Bandon Bay, in the Gulf of Thailand (GoT), has been impacted since 2007 by the continued stocking of larval blue swimming crab Portunus pelagicus, also called a crab bank. In this study, the food web in the Bay was modelled using Ecopath software to compare the trophic status, interaction and energy flow among the components in the system in 2007 and 2016 (i.e., before and 10 years after the crab bank intervention). The models were based on data collected from trawling. Twenty fish and shellfish components were used in the 2007 model, while 22 were used in the 2016 model. A significant increase in biomass was found in blue swimming crab, but biomass declined for other demersal fishes, cephalopods, and Penaeid shrimps. The production/biomass ratios of most components were higher in 2016 but the consumption/biomass ratios were relatively unchanged. The ecotrophic efficiency indicated that shellfishes were more exploited than fishes. Changes in most of the ecological indices revealed higher maturity and stability after 10 years of crab bank operation. The mixed trophic impact indicated bottom-up regulation, and that the increase of blue swimming crab negatively impacted only Mantis shrimp. Overall, the results indicate positive impacts of the crab bank intervention.

Selective Gap Analysis of the Escape Hatch in the Umbrella Trap with Six Doors for the Blue Swimming Crab (Portunus pelagicus)

The blue swimming crab fishermen in Teluk Makassar, Lantebung Village tend to exploit the blue swimming crab resources without considering Sustainable Fisheries and environmental sustainability by using non-environmentally friendly fishing gear. The innovation of constructing a trap with an escape hatch is expected to provide an opportunity for undersized blue swimming crabs (carapace width &lt; 10 cm) to escape from the trap through the escape hatch. This research aims to determine the selectivity and effectiveness of using the escape hatch to allow blue swimming crabs to escape in the waters of Teluk Makassar, Lantebung Village. The research was conducted for two months, from November to December 2022. Blue swimming crab samples were collected from foldable traps and dragon traps used by the fishermen, and the crabs were collected while still alive. The experimental method was employed, with four treatments and 21 replications. Based on the estimation of the selection ogive and the selectivity ogive curve, it can be concluded that the selectivity of the 3.5x4 escape hatch is more effective in allowing blue swimming crabs with carapace width below 10 cm to escape compared to other escape hatch sizes, thus avoiding the capture of immature or maturing crabs with mature gonads.

Comparative transcriptomic analysis provided insights into the local molecular responses of swimming crabs, Portunus trituberculatus and mud crabs, Scylla paramamosain to the infection of Ameson portunus (Microsporidia)

Microsporidiosis has been increasingly causing severe economic losses in aquaculture. Insights into the molecular mechanism of host responses to aquatic microsporidia infection will be beneficial for the formulation of control strategies of microsporidiosis in aquaculture. Ameson portunus is the recently identified causative agent of “toothpaste-like syndrome” in Portunus trituberculatus and “slurry-like syndrome” in Scylla paramamosain. Here, muscle tissues of these two crabs at the early and late disease stages of A. portunus infection were subjected to the comparative transcriptomic analysis to disclose differential molecular responses of this microsporidian infection and characterize the host's responses dynamics against the infection at these two stages. These differentially expressed genes (DEGs) were mainly involved in DNA replication, metabolism, and immunity. Among them, the DEGs associated with DNA replication were significantly up-regulated, indicating that A. portunus can achieve proliferation by regulating the cellular responses of host. The significant upregulation of DEGs associated with recognizing and removing DNA damage, homologous recombination, and mismatch repair suggested that A. portunus damaged to the genetic material of crab muscle cells, and host repaired DNA damage caused by the infection of A. portunus by enhancing homologous recombination. The DEGs associated with amino acid and carbohydrate metabolism were significantly down-regulated, suggesting that muscle metabolic function was impaired in severely infected crabs, and energy supply, regulation of oxidative stress, and resistance to pathogens of host were significantly affected at the late disease stage. It could possibly explain why diseased P. trituberculatus and S. paramamosain exhibited reduced food intake, sluggish movement, and slow growth. In response to the infection, the two crabs exhibited different immune responses. P. trituberculatus responded to the infection of A. portunus by phagocytosis and apoptosis, and S. paramamosain induced cytokine production by recognizing the pathogen and signaling downstream to eventually clear the invading cells of A. portunus.

Population structure and reproductive dynamics of the ridged swimming crab Charybdis natator in the southern Taiwan Strait of China: significant changes within 25 years

The ridged swimming crab Charybdis natator (Portunidae) is a commercially important crustacean species in China. The purpose of this study is to compare its population structure and reproductive pattern within the same fishing area (the southern Taiwan Strait) from two datasets over 25 years; one from 1994−1996 (the early years of the C. natator fishery) and the other from 2019. The overall sex ratio (male:female) changed from a male bias (1:0.76, p &amp;lt; 0.01) in 1994−1996 to a female bias (1:1.38, p &amp;lt; 0.01) in 2019. Male body sizes (carapace width, CW) were significantly larger than those of females in both datasets (p &amp;lt; 0.05). The average CW and body weight (BW) of males and females in 2019 were significantly smaller (p &amp;lt; 0.01) and lighter (p &amp;lt; 0.01) than those in 1994−1996. The maximum body size and the proportion of large-sized individuals (CW &amp;gt; 10 cm) decreased dramatically over 25 years. One spawning peak season was identified from each dataset, i.e., March−August 1994−1996 and February−April 2019, revealing a 1-month shift. The minimum body sizes for female maturation (carrying eggs) were 6.9 cm CW in 1994−1996 and 6.1 cm CW in 2019, an 11.6% reduction over 25 years. For the first time, the CW at 50% female maturation, the relationship between female absolute fecundity and CW, and egg diameters were obtained from the 2019 dataset, which can be applied in the future comparisons. Recent studies have revealed a consistent spawning peak in February–April for several commercially important crabs in the southern Taiwan Strait. These findings should be considered in crab fishery management. Furthermore, both fishery- and environment-associated factors influencing crustacean population structure and reproductive dynamics merit further investigation.

Purification, Expression, and Characterization of Sarcoplasmic Calcium Binding Protein: A Novel Allergen of Portunus trituberculatus.

Swimming crab (Portunus trituberculatus), a crucial valuable crustacean, is a common factor causing food allergy. However, studies on allergens of P. trituberculatus are scarce. In this study, the sarcoplasmic calcium binding protein (SCP) of P. trituberculatus was expressed in Escherichia coli, purified with affinity chromatography, and the IgE-binding activity was evaluated through serological analyses. Further, the structure, physicochemical properties, and cross-reactivity were assessed via bioinformatics, immunologic, and spectroscopy techniques. The results indicated that P. trituberculatus SCP was an allergen displaying strong IgE-binding capacity, composed of 60% α-helix. It presented good immunologic and structural stability at 4-70 °C and pH 3-10, and only exhibited high IgG cross-reactivity among crustaceans, without cross-reactivity with other species tested. These results establish the foundations for further studies on SCP and are promising to promote the development of specific crustacean allergen detection and precise allergy diagnosis.

Effects of misrepresentative length samples on individual growth and stock condition estimates

Despite its importance in fisheries studies, there is insufficient understanding on the effect of sampling error or bias on individual growth and other stock indicators. We show the influence of sample length distributions on parameter estimates, illustrating with an example. For the brown swimming crab, we simulated length samples in five configurations and estimated parameters of von Bertalanffy (k, L∞L∞ , t0), asymptotic weight ( W∞W∞ ), weight-length relationship (a, b), growth performance (ϕ’) and condition factor (Kn). Parameter estimates were compared with baseline values using relative bias, standard error and root mean square error. The results show that the accuracy and bias of parameter estimates depend on the lengths sampled. For example, the bias and accuracy of L∞L∞ and W∞W∞ vary inversely with sampled length, whereas combining length segments yields smaller biases of k and t0 than those of L∞L∞ and W∞W∞ . In general, the accuracy of parameter estimates does not always depend on sampling the entire length range, and errors are not the same for all parameters. These results are useful to guide sampling when resources are scarce. We discuss potential reasons for incomplete length sample structure and offer recommendations to obtain best estimates for parameters of interest.