Intercohort cannibalism and parturition-associated behaviour of adult swordtail, Xiphophorus helleri Heckel (Pisces: Poeciliidae)

The post‐parturition behavioural patterns of adult Xiphophorus helleri (Heckel) were described and quantified by recording their duration and/or frequency in glass tanks. All births occurred in the dark. Female behaviour might increase the chance of newborn juvenile survival: at the top of the tank, where juveniles are more vulnerable to predation, the females gave birth in the artificial refuge, while no parturition took place in the refuge at the bottom. Birth‐giving females were no less cannibalistic than males and other females. There was a reduction in cannibalism and the frequency of secondary attacks with time, even though the number of juveniles in the tank continued to increase due to ongoing parturition. Most adults were found at the bottom of the water column during the first 500 min of parturition, after which they were distributed equally in the water column. The movement of adults, away from the bottom and consequently away from the juveniles corresponded with an increase in feeding on alternative food and a reduction in cannibalism. Thus, cannibalism in swordtail might be opportunistic predation.     

Feeding experiments on the larvae of the fiddler crab Uca pugilator (Brachyura,Ocypodidae), reared in the laboratory

Larvae of Uca pugilator (Bosc) were reared in the laboratory from hatching to the megalopa stage on three different diets: (1) newly hatched Artemia salina nauplii (diet A), (2) the rotifer Brachionus plicatilis (O.F. Müller) and a ciliate Euplotes sp. (diet RC), and (3) a combination of the above two diets (diet ARC). The survival rate of zoeae fed diet A (90.0%) and diet ARC (93.8%) was much higher than that of the larvae fed diet RC (22.5%). The duration of the zoeal stages was significantly shorter for the larvae fed diet ARC than for those fed diets A and RC. The survival rate of megalopa larvae (reared on diets A and ARC in the zoeal stages) was high (above 90%) for megalopa fed Artemia nauplii only, as well as for those fed a combination of Artemia nauplii and shrimp. No significant differences in duration of the megalopa stage were found between the latter diet groups.     

Early development,growth and survival of the yellow crab Cancer anthonyi Rathbun (Decapoda,Brachyura) in the laboratory

Larvae of the yellow crab, Cancer anthonyi Rathbun, were reared through five zoeal stages and one megalops stage in the laboratory. Total larval development times were 33 and 45 days at 22°C and 18°C, respectively. Survival rates to the first crab instar, for larvae reared in recirculating systems on a diet of Artemia nauplii, were 26% at 22°C and 17% at 18°C. Although no larvae reared in glass containers at 22°C survived past the first zoeal stage, 11% of those in similar containers at 18°C reached the first crab instar. Bacterial infections were associated with most observed mortalities. Antibiotics failed to increase the survival rates of larvae reared in glass containers.Juvenile crabs were reared in individual containers and in communal aquaria through 14 crab instars. Although instar durations were shorter at 22°C than at 18°C, mean carapace widths were significantly greater at the lower temperature. Crabs in communal aquaria at 22°C were larger than corresponding crabs at the same temperature in individual containers. Crabs reared in aquaria at 22°C reached the twelfth instar with a mean size of 90.3 mm, 195 days after hatching. Sexually mature thirteenth stage laboratory-reared crabs were mated and their offspring were reared through the ninth crab stage.     

Larval molting and growth of the Japanese spiny lobster Panulirus japonicus under laboratory conditions

ABSTRACT:   Ten newly hatched phyllosoma of Panulirus japonicus were cultured individually to monitor body length ( BL ) and intermolt period, and 2000 were cultured in groups to sample specimens for measurement of body weight. Phyllosoma were fed with Artemia and mussel gonad; the culture seawater temperature was 24–26°C. The individually cultured phyllosoma showed an increment in body length by the first molt of approximately 0.5 mm, and the molt increment increased to approximately 1 mm at 5 mm BL ; it was constant to 15 mm BL . Thereafter, the molt increment increased exponentially. The duration of the first instar was 6–7 days. Instar duration increased with development up to approximately 2 weeks at the 20th instar (∼16 mm BL ) and then became constant. Of the 10 larvae reared individually, five metamorphosed to the puerulus stage. The entire phyllosoma life ranged from 245–326 days (mean 289.0 days), and the number of instars ranged from 22–29 (mean 26.2). Body length in the final instar ranged from 28.50–33.10 mm (mean 30.280 mm). For the phyllosoma cultured in groups, relationships between BL and wet/dry body weights ( WW / DW , mg) were expressed as exponential equations: WW  = 0.0686 BL ^2.2023 and DW  = 0.0209 BL ^2.1905.     

Effects of feeding conditions and size differences on aggressive behaviour and cannibalism in the Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel) larvae

We examined the effects of feeding conditions and size differences on the aggressive behaviour and cannibalism in Pacific bluefin tuna (PBT) Thunnus orientalis larvae. In a 24 h experiment, restricted feeding alone was found to remarkably increase the frequency of aggressive behaviour, which was further elevated by differences in fish size. In a 4‐day rearing experiment, while aggressive behaviour was increased by restricted feeding alone, the frequency of cannibalism did not change significantly. Although the frequency of aggressive behaviour did not increase with difference in size factor, small fish in this group gradually tended to die over 4‐day period. In the restricted feeding and size difference group, large fish were observed to bite the small fish, and almost all the small fish died on the day after the start of the experiment. These results suggest that the aggressive behaviour of PBT larvae is chiefly increased by the shortage of live food; however, deaths related to cannibalism mainly occurred in small larvae and rapidly increased with food restriction and differences in fish size.     

Development of nursery culture techniques for the mud crab Scylla paramamosain (Estampador)

Cannibalism is one of the main causes of mortality in the culture of the mud crab Scylla paramamosain, particularly in the early post‐larval and juvenile stages when the densities of hatchery‐reared crabs may be very high before stocking into ponds or release into the wild for stock enhancement. In a series of experiments investigating cannibalism mitigation, the influence of stocking density, the effectiveness of sand substrate, brick and shell shelters and feed type were compared in culture of crabs from instar 1 for short nursery periods of 15–30 days. Inclusion of brick and shell shelters significantly increased survival over sand substrate alone. However, inclusion of shelters did not affect growth rates. In scaled‐up nursery production in lined‐ponds, with shelters, live Artemia biomass and fresh chopped shrimp or tilapia were found to be equally effective feeds for juvenile crabs stocked at a density of 70 m⁻² from instar 1 and grown for 30 days [52–66% survival, 21.6–24.6 mm carapace width (CW)]. In an extended nursery period for a further 30 days, crabs of 22 mm CW, stocked at 30 m⁻² in the same ponds, attained a final size of 34.5–36.2 mm CW with a survival of 64.3–67.0% using the same feeds.     

Morphological characterization of larval stages and first juvenile of the freshwater prawn Cryphiops caementarius (Molina, 1782) (Decapoda: Palaemonidae) under laboratory conditions

Research has been in progress for several years on various aspects of the biology and ecology of the freshwater prawn Cryphiops caementarius, an inhabitant of rivers in northern Chile. The commercial value of this prawn fomented the accomplishment of studies on its reproduction and development with the aim of producing juveniles under controlled conditions, to be followed by growout to commercial size in managed culture systems. The present study describes larval culture of this species from eggs of gravid females obtained in the field, from the first developmental stage (Zoea I) through the first juvenile stage. The larvae were cultured at 25 °C in UV sterilized water at variable salinities based on the requirements of the developmental stages. Larvae were fed with Nannochloris, Isochrysis and Artemia nauplii as required. This report describes in detail the 18 larval stages of this prawn, as well as its first juvenile form.     

Bioenergetics of cannibalism in juvenile barramundi Lates calcarifer (Bloch): exploring growth advantage of fish fed live prey and formulated diet

The present study investigated the growth performance of juvenile barramundi Lates calcarifer (Bloch) fed conspecific prey (CP), formulated diet (FD) and a mix of both (MIX) using a bioenergetics approach. Fish in the MIX treatment ingested significantly more CP than FD by dry mass. However, prey mass ingestion and cannibalism rate in the MIX treatment were significantly lower than in the CP treatment. This indicates that the provision of alternative food does not complete mitigate cannibalism, but it can significantly reduce cannibalism in barramundi. Fish in the FD treatment showed a significantly higher daily food intake than fish in the CP or MIX treatments. However, fish fed conspecifics showed significantly better feed conversion efficiencies, apparent digestibility rates and growth performances. Exclusive cannibalistic barramundi assimilated significantly more energy consumed, with 1.5% of energy lost in faeces comparing with 7.3% of siblings feeding exclusively on FD. Consequently, exclusive cannibals channelized more energy consumption into growth (57.1%) than those fed solely on FD (43.9%). Therefore, high energy allocation into growth promoted better feed conversion efficiency and growth performance of cannibalistic barramundi than siblings fed solely on FDs. This study implies that fast‐growing cannibals may continuously prey on slow‐growing conspecifics due to growth advantage through cannibalism. Therefore, size heterogeneity should be reduced at initial stocking and controlled as fish grow to avoid the emergence of new cannibals.     

Larval survival,development and growth in the horsehair crab,Erimacrus isenbeckii,cultured under different photoperiod conditions

Larval sinking causes larval mass mortality during seed production in the horsehair crab, Erimacrus isenbeckii. Under normal light conditions, horsehair crab larvae generally show negative phototactic behaviour and sink in their rearing seawater. It has been proposed that culturing larvae in the dark may prevent larval sinking. Herein, we examined the effect of photoperiods on horsehair crab larval survival and development to facilitate the development of larval rearing techniques that prevent sinking. Newly hatched larvae were reared with Artemia to the first crab stage in 2‐L beakers under five photoperiods: 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Larvae survived and molted to the first crab stage under all tested photoperiod conditions. The survival rate improved with increasing light period, whereas the developmental period for each larval stage decreased with increasing light period. Longer light periods increased the carapace length at the first crab stage. Our results suggest that larvae could be cultured to the first crab stage in large‐scale tanks under constant darkness. However, significantly improved larval performance under longer photoperiodic conditions indicates a need for developing alternative culture techniques to control larval behaviour in the seed production tank.     

Effects of stocking density and size distribution on growth, survival and cannibalism in juvenile fat snook (Centropomus parallelus Poey)

This study was carried out in order to determine the effect of stocking density and size distribution on growth, survival and cannibalism of fat snook (Centropomus parallelus Poey) juveniles. Three stocking densities (1.5, 3 and 6 fish L⁻¹) were tested in two groups of fish: homogeneous [total length (TL)=22.1 mm; coefficient of variation of length (CV)=8%] and heterogeneous (TL=22.7 mm; CV=15%). The experimental design was factorial (3 × 2) using triplicates. Fish were reared for 30 days in 80‐L circular tanks with an open flow‐through system. There was no significant interaction between the two factors (density and size distribution). The highest cannibalism rate (14.2%) was observed in the heterogeneous group, which also had a significantly higher growth rate (TL=45.6 mm) than the homogeneous group (3.2% and TL=40.9 mm). Significant differences were found between the two lowest densities and the highest density (6.2%, 6.3% and 13.4% respectively). Growth was not affected by fish density. Cannibalism was the main cause of mortality. In 90% of the occurrences, whole prey ingestion was observed. According to the results obtained, cannibalism was positively correlated to density, although size grading of fat snook juveniles is recommended to control cannibalism in all the densities tested.     

Application of logistic regression analysis to predict cannibalism in orange‐spotted grouper Epinephelus coioides (Hamilton) fry

Cannibalism is frequently observed in larviculture of orange‐spotted grouper Epinephelus coioides. Previously, based on measurements of morphometric characters, a linear equation of total length (TL) of prey to cannibals was proposed: TL_prey = 0.80 TL_cannibal – 1.50. To verify the reliability of the equation, experiments were performed with pairs of fish with different TLs. Cannibalism occurred only when the cannibal‐prey size ratios were equal to or larger than that predicted by the equation. To predict the probability of cannibalism among the grouper of known TLs, a logistic regression model was proposed. The logistic regression model is: The logistic regression model showed the following: when either TL_prey or TL_cannibal is constant, the probability of cannibalism increases with increase in the cannibal‐prey size ratios; if given a constant cannibal‐prey size ratio, probability of cannibalism is lower in early stages than in later stages. The prediction contrasts with that calculated from the linear equation where the minimum cannibal‐prey size ratios decrease with size of the cannibal. However, the prediction matches observed rearing experiences: cannibals prefer smaller prey to larger ones and the cannibalism rate declines as fry age.     

Lethal doses of ammonia on the late-stage larvae of Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), (Decapoda: Grapsidae) reared in the laboratory

Four successive life stages (zoea-III, zoea-IV, zoea-V and megalopa) of the Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), were exposed to ammonia in a series of short-term bioassays with the static-renewal method at 22°C, pH 8.0 and 25%o salinity. The greatest sensitivity was observed in the zoea-III stage. The 24-h LC₅₀ values for zoea-III, zoea-IV, zoea-V and megalopa were 32.8, 73.1, 84.0 and 90.1 mg L^?1 for NH₃+ NH₄⁺, and 1.11, 2.36, 2.77 and 3.18 mg L^?1 for NH₃, respectively. The 72-h LC₅₀ values for zoea-III, zoea-IV and zoea-V were 11.9, 23.6 and 38.2 mg L^?1 for NH₃+ NH₄⁺, and 0.40, 0.76 and 1.26 mg L^?1 for NH₃, respectively. The 96-h LC₅₀ values for megalopa were 37.3 mg L^?1 for NH₃+ NH₄⁺ and 1.31 mg L^?1 for NH₃. It was found that ammonia tolerance increased with larval development from zoea-III to megalopa, especially from zoea-III to zoea-IV and from zoea-IV to zoea-V. A comparison of safe levels of ammonia among the different life stages indicated that all stages were significantly different with respect to safe levels of ammonia (P < 0.05) except zoea-V and megalopa, which had the highest safe levels. In general, both the larvae and juveniles of E. sinensis are less resistant to ammonia than those of other crustacean species studied so far.     

Pathology of shell disease in the blue crab, Callinectes sapidus Rathbun, (Decapoda: Portunidae)

Blue crabs affected with shell disease displayed a wide array of pathologies in response to this very common affliction. Grossly, shell disease lesions most commonly presented as variably sized brown to black foci. Such lesions ranged from very small (1 mm2) to locally extensive (up to 200 mm2 in area). The larger of the melanized lesions sometimes appeared ulcerated. The most severe lesions observed (Pamlico River shell disease-PRSD) resulted in loss of up to 25% of the entire carapace. A diverse bacterial flora consisting of aeromonads, vibrios and five other genera were isolated as the predominant organisms from shell disease lesions. Fungi were rarely observed in larger lesions. Protozoa and algae were also rarely observed on the surface of some lesions. Histologically, lesions ranged from mild erosion of the epicuticle and outermost layers of the calcified endocuticle to more extensive endocuticle erosion with accompanying inflammation. In the most severe cases, there was total loss of the endocuticle and epidermis, with pseudomembrane formation, intense haemocyte infiltration, and involvement of adjacent viscera. There was no apparent relationship between the size of gross lesions and their histological severity (as defined by the extent of tissue damage), suggesting that gross examination of shell disease lesions is not a reliable method for assessing the damage to affected blue crabs.     

Daily food intakes and optimal food concentrations for red king crab (Paralithodes camtschaticus) larvae fed Artemia nauplii under laboratory conditions

Daily food intakes, optimal feeding regimes and food concentrations for laboratory reared Paralithodes camtschaticus (Tilesius, 1815) larvae were investigated. Artemia nauplii hatched at standard conditions were used as food. Daily food intakes of zoeae I–IV at 7–8 °C comprised 11.3, 22.4, 33.2, and 41.8 nauplii individuals (ind)^?1 day^?1, respectively, taking into account that wet weight of Artemia nauplii used for the experiments constituted 0.026 mg, dry weight 0.0042 mg. Optimal initial Artemia nauplii concentrations for feeding zoeae I–IV was determined as 400–600, 600–800, 800–1000 and 1000–1200 nauplii L^?1 respectively. Recommendations on using Artemia nauplii as food for red king crab larvae were outlined on the basis of experimental results. Growth, development and survival rates of zoeae I–IV reared in recycling water system at 7–8 °C and fed Artemia nauplii according to these recommendations were described.     

中华绒螯蟹肝胰腺白化症的病因研究

2002年10月以来,通过逐户访问及调查问卷的形式对2001～2002年东太湖中华绒螯蟹(Eriocheir sinensis)养殖区"白膏症"发病症状、扣蟹的来源、投饵模式、水草覆盖率、螺蛳投入量、底泥状况、回捕率、产量等进行较为系统的调查。同时对病蟹进行寄生虫检查、病原微生物分离、回接攻毒及病变组织的电镜观察等病原学研究,结果未发现致病性生物。调查结果表明,中华绒螯蟹"白膏症"的发病率雄蟹显著高于雌蟹,其症状为甲壳发黄,头胸甲腹面下肝区发白色或青黑色,肝胰腺由正常的橘黄色变成淡黄或白色;症状严重的病蟹胸腔积水,肌肉松驰萎缩,肝胰腺呈糜烂状,鳃丝发黑。调查结果显示,"白膏症"的发生与饵料的投喂量、动植物饵料之比及水环境有着密切的联系。根据该病的主要症状及发病原因,认为该病应命名为中华绒螯蟹肝胰腺白化症。     

饲料中添加维生素A、C和E对克氏原螯虾生长和免疫力的影响

维生素在甲壳动物的存活、生长、繁殖过程中起重要作用。本研究采用正交设计实验,研究了维生素A、维生素C和维生素E的添加量对克氏原螯虾(Procambarus clarkii)幼虾生存、生长和免疫的影响。研究设立三个因子A、B、C,分别为维生素A、维生素C、维生素E的添加量。每个因子设3个水平,维生素A添加量的3个水平为:0.0048、0.0054、0.006%;维生素C添加量的3个水平为:0.02、0.05、0.08%;维生素E添加量的3个水平为:0.02、0.04、0.06%。极差分析结果表明,克氏原螯虾幼虾成活率最高时的因子水平组合为:A3B1/B3C2;增重率最大时的因子水平组合为:A3B2C2;丙二醛(MDA)含量、超氧化物气化酶(SOD)活性和SOD基因表达水平最低时的因子组合水平都为:A2B1C1;酚氧化酶(PO)活性最高时的因子水平组合为:A3B2C1;谷胱甘肽过氧化物酶基因GPx表达水平最低时的因子水平组合为:A3B1C1。将克氏原螯虾幼虾的成活率和增重率作为主要考虑因素,综合考虑免疫指标及成本因素,我们建议在本次实验设计的条件中,选择A3B1C2作为最佳组合方案,即维生素A添加量为0.006%、维生素C添加量为0.02%、维生素E添加量为0.04%时,最有利于克氏原螯虾幼虾的存活、生长,提高其免疫力。     

The larval rearing of the marine ornamental crab, Mithraculus forceps (A. Milne Edwards, 1875) (Decapoda: Brachyura: Majidae)

The goal of this study is to develop a larviculture protocol for Mithraculus forceps, a popular marine aquarium species. Different temperatures (25±0.5°C and 28±0.5°C), stocking densities (10, 20, 40 and 80 larvae L^?1), prey densities (newly hatched Artemia of 1, 4, 7 and 12 nauplii mL^?1) and metamorphosis to crab conditions (Systems A and B) were tested. The best survivorship and faster development were obtained when the larvae were reared at a density of 40 larvae L^?1 for 7 days post hatching (DPH) in System A, at 28°C and fed with 7 mL^?1 of newly hatched Artemia nauplii. After 7 DPH all the megalopa were moved to System B and the same temperature and prey density were maintained. At the end of the experiment, 12 DPH, survivorship of 74.1±4.8% was obtained.