Simulation of Nile tilapia (Oreochromis niloticus niloticus L.) culture in ponds, through individual-based modelling, using a population dynamic approach     

Gertjan J de Graaf  Pieter J Dekker  Bram Huisman  & Johan A J Verreth 《Aquaculture Research》2005,36(5):455-471

A simulation model for the production of the Nile tilapia (Oreochromis niloticus niloticus L.) for mixed‐ or mono‐sex culture and for poly‐culture with the African catfish (Clarias gariepinus Burchell 1822) or African snakehead (Parachanna obscura Günther 1861) is presented. The model is based on an exponential decay model used in population dynamics and follows an individual‐based approach. The model consists of a tilapia sub‐model representing population dynamics, growth and recruitment and a predator sub‐model representing the predation process and population dynamics and growth of the used predator. The model was calibrated with data on mixed‐ or mono‐sex culture of Nile tilapia and for poly‐culture with the African catfish or African snakehead obtained in Congo Brazzaville and validated with similar data from the Philippines, Thailand and the Ivory Coast. The model visualized major underlying processes in tilapia farming and aspects for further improvement of the model; growth is one of the most sensitive input parameters and should be quantitatively related to feeding level and feed quality; length at first maturity and quantification of the recruitment of Nile tilapia has a relatively large influence and recruitment should be related to the length of the females; prey–predator relations are too coarse and should be more fine‐tuned with the relation between prey size and predator size. Incorporation of these features would provide the basis of a model that can serve as a predictive and decision‐making support tool.  相似文献   

Urea and ammonia excretion by embryos and larvae of the African catfish Clarias gariepinus (Burchell 1822)     

B.F. Terjesen  J. Verreth  H.J. Fyhn 《Fish physiology and biochemistry》1997,16(4):311-321

Yolk-sac larvae and starved larvae of Clarias gariepinus (Burchell 1822), reared at 28°C, were predominantly ammonotelic, but urea excretion contributed about 19±7% to the total nitrogen excretion. Exogenously feeding larvae of C. gariepinus were mainly ammonotelic until 180-205 h post fertilization, but from then on the relative urea excretion stabilized at 44±13%. The contents of total free amino acids (FAA) and ammonia in C. gariepinus peaked around complete yolk absorption. During the first period after hatching 64% of the FAA and 60% of the total ammonia were located in the yolk compartment. The body compartment contained the highest amount of FAA and total ammonia at the end of the yolk-sac period (65 and 77%, respectively). The amount of nitrogen originating from catabolism of amino acids was balanced within 6% by the excreted sum of ammonia and urea. The high degree of ureotelism in C. gariepinus larvae may constitute an adaptive mechanism to a habitat of temporal water shortage.  相似文献   

The effect of stocking density on growth,survival and agonistic behaviour of African catfish     

H. Kaiser  O. Weyl  T. Hecht 《Aquaculture International》1995,3(3):217-225

A high rate of sibling cannibalism is one of the principal obstacles in the rearing of larvae and juveniles of the African catfish Clarias gariepinus. This paper examines the underlying behavioural components of agonistic behaviour under culture conditions. Ten day old catfish larvae were stocked at 30 larvae l^–1 in three tank designs with different surface areas and equal volumes. Stocking densities were 1.2, 0.6 and 0.3 fish cm^–2 bottom surface. Growth did not differ between treatments. The highest mortality over 30 days was recorded at the medium density (0.6 larvae l^–1). Fish stocked at this density showed the highest rate of aggression, while there was no difference in aggression between the highest and the lowest stocking densities. The results indicate that stocking density should be at least as high as 1.2 larvae cm^–2 bottom surface area to obtain high production at best survival rates.  相似文献   

Catecholestrogens inhibit dopamine methylation in the gonadotrops of the African catfish,Clarias gariepinus     

L. A. C. Van Asselt  R. J. M. Timmers  H. J. Th. Goos  J. G. D. Lambert  P. G. W. J. Van Oordt 《Fish physiology and biochemistry》1989,6(4):207-212

Isolated gonadotrops of the African catfish,Clarias gariepinus, were incubated with dopamine (DA) and/or catecholestrone and the activity of the enzyme catechol-O-methyltransferase (COMT) was determined by measuring the methylated products. From the apparent Km values for DA and catecholestrone of 0.4–1.3 M and 17.9–25.2 M respectively, it was concluded that catecholestrone is a better substrate for the enzyme COMT, compared to DA. Moreover, the methylation of DA is inhibited by comparatively low concentrations of catecholestrone.  相似文献   

Approaches to optimizing dietary protein to energy ratio for African catfish Clarias gariepinus (Burchell, 1822)     

M.Z. ALI  & K. JAUNCEY 《Aquaculture Nutrition》2005,11(2):95-101

An 8‐week feeding trial was conducted in a recycling water system at 28 ± 1 °C to investigate protein to energy ratio (P/E ratio) in African catfish Clarias gariepinus (10.9 ± 0.04 g). Six fishmeal‐based diets of two protein levels (330 and 430 g kg^?1), each with three lipid levels (40, 80 and 120 g kg^?1) resulted in P/E ratios ranging from 15.5 to 21.3 mg protein kJ^?1 gross energy (GE) were fed to 20 fish (per 30‐L tank) in triplicate. Fish were fed 50 g kg^?1 of their body weight per day adjusted fortnightly. Significantly higher (P < 0.05) growth rates and feed conversion efficiency were evident in fish fed with higher protein diet. The highest growth rate was found by fish fed 430 g kg^?1 protein, 21.2 kJ^?1 GE with a P/E ratio of 20.5 mg protein kJ^?1 GE. Significantly indifferent (P > 0.05) values of protein utilization were found in‐between the both (higher and lower) protein diets. Higher lipid deposition (P < 0.05) in whole body and liver was observed with increasing dietary lipid level at each protein diet and as higher (P < 0.05) for the lower protein diets. Liver glycogen tended to decrease with increasing gross energy at each protein diet and higher protein diet showed comparatively lower values (P > 0.05). Digestive enzyme activities (protease and lipase) and histological examination of intestine and liver of fish fed varying P/E diets found no significant differences in response to experimental diets. The study reveals that African catfish C. gariepinus performed best the diet containing 430 g kg^?1, 21.2 kJ g^?1 and 20.5 mg protein kJ g^?1 GE protein, gross energy and P/E ratio, respectively.  相似文献   

Changes in tissue α-tocopherol status and degree of lipid peroxidation with varying α-tocopheryl acetate inclusion in diets for the African catfish     

R.T.M. BAKER  S.J. DAVIES 《Aquaculture Nutrition》1996,2(2):71-79

Juvenile African catfish, Clarias gariepinus (Burchell), were fed low-tocopherol, practical test-diets containing graded levels of α-tocopheryl acetate (0, 80, 200 and 500 mg kg^?1 dry feed) at proportionately 0.02 body weight per day for 70 days. After the feeding period, selected fish tissues were assayed for α-tocopherol and thiobarbituric acid reactive substances (TBARS) concentrations, before and after iron-ascorbate stimulated peroxidation. Results show that tissue accretion of α-tocopherol in muscle, liver and blood plasma increased linearly (R²= 0.83, 0.82 and 0.93, respectively) in response to elevated dietary supplementation of α-tocopheryl acetate within the range of doses under study. In muscle and liver this resulted in a significant decrease (P < 0.05) in basal TBARS and TBARS after stimulated peroxidation, indicating a greater stability against oxidation. Growth indices were not significantly affected (P > 0.05) by dietary α-tocopheryl acetate inclusion. Clarias fed the highest α-tocopheryl acetate dose (500 mg kg^?1 dry feed) were observed to have significantly lower (P < 0.05) haematocrit (% packed cell volume) than fish fed the basal diet (0 mg kg^?1 dry feed). It was concluded that supplemental α-tocopheryl acetate in practical diets, for Clarias gariepinus, was effective in reducing the degree of tissue-lipid peroxidation under conditions of increased oxidative stress. Thus, the post mortem resistance to oxidation achieved would improve the stability of catfish products destined for human consumption.  相似文献   

Survival of Clarias gariepinus fry in earthen ponds: Effects of composts and leaks     

S. Yong-Sulem  E.T. Tomedi  S. Mounchili  S. Tekeng  R.E. Brummett 《Aquaculture (Amsterdam, Netherlands)》2006,260(1-4):139-144

To inform decisions on improving the yields of African catfish Clarias gariepinus fingerlings in earthen ponds, the hypothesis that composts and leaks were partly responsible for usually low and variable fry survivals was tested, through comparison of treatments and simple regression. The occurrence of amphibians was significantly higher (P < 0.05) and survival of fry was significantly lower (P < 0.02) in ponds with composts than in those without. The survival of fry and fingerlings in earthen ponds was negatively correlated with their night leaking rates and regression analysis yielded the equations y = − 13.31x + 82.56 for fry and y = − 6.97x + 95.29 for fingerlings, where y is the survival of fry or fingerlings in a holding pond and x is the leaking rate of the pond. Realizing how negatively the existence of composts and leaks could affect the survival of fry and fingerlings, fertilizing unfenced ponds with composts and sterilizing nursery ponds by drying were proscribed.  相似文献   

Pituitary gonadotropin-releasing hormone (GnRH) receptor activity in goldfish and catfish: seasonal and gonadal effects   总被引：3，自引：0，他引：3  

H. R. Habibi  R. De Leeuw  C. S. Nahorniak  H. J. Th Goos  R. E. Peter 《Fish physiology and biochemistry》1989,7(1-6):109-118

The goldfish pituitary contains two classes of gonadotropin-releasing hormone (GnRH) binding sites, a high affinity/low capacity site and a low affinity/high capacity site (Habibiet al. 1987a), whereas the catfish pituitary contains a single class of high affinity GnRH binding sites (De Leeuwet al. 1988a). Seasonal variations in pituitary GnRH receptor binding parameters, and the effect of castration on pituitary GnRH receptor binding were investigated in goldfish and catfish, respectively. In goldfish, GnRH receptors undergo seasonal variation with the highest pituitary content of both high and low affinity sites occurring during the late stages of gonadal recrudescence. The observed changes in pituitary GnRH receptor content correlate closely with responsiveness to a GnRH agonistin vivo in terms of serum gonadotropin (GTH) levels. In catfish, castration results in a two-fold increase in pituitary GnRH receptor content, which can be reversed by concomitant treatment with androstenedione, but not by the non-aromatizable androgen 11β-hydroxyandrostenedione; changes observed in GnRH receptor content correlate with variations in serum GTH levels and responsiveness to a GnRH agonist. In summary, the present study provides a clear evidence for seasonal variation in pituitary GnRH receptor activity in goldfish, and demonstrates a gonadal feedback mechanism regulating GnRH receptor activity in the catfish pituitary.  相似文献   

Stunning of farmed African catfish (Clarias gariepinus) using a captive needle pistol; assessment of welfare aspects     

E Lambooij  R J Kloosterboer  C Pieterse  M A Gerritzen  & J W Van de vis 《Aquaculture Research》2003,34(14):1353-1358

The objective of this study was to assess whether high‐pressure injection of air into the brain of African catfish (Clarias gariepinus) could render the animal unconscious and insensible immediately and permanently. In the study, 48 African catfish with a live weight of 900–1900 g were restrained and equipped with EEG and ECG electrodes and then stunned. The catfish were stunned mechanically using a captive needle pistol. The pressure to shoot the needle was 8 bar and that to inject the air was 3 bar for 1.5 s. The catfish behaviour was observed during and after stunning. τ and δ waves and spikes, which precede a stoppage in brain activity as measured on the EEG, were used as indices for the measurement of immediate induction of unconsciousness and insensibility In 23 of 42 fish, an iso‐electric line was observed after an average of 13.4 s, while in the remaining fish the τ and δ waves and spikes remained on the EEG during the recording period. In all cases, the ECG showed an irregular heart rate with fibrillation and extra systolae. Moreover, the configuration showed ischaemia. Before the captive needle stunning, free‐swimming fish (n=7) explored the tank for an average of 21±12 s before lying down at the bottom. After stunning, they showed clonic uncoordinated swimming movements. The movements stopped after an average of 38±50 s. In another group (n=7) that was stunned and subsequently placed in ice water, clonic cramps were observed in two out of seven animals. When taking into account the number of animals with a reliable EEG (n=42) and using 95% confidence intervals, it was concluded that at least 93% of the catfish were effectively stunned using a correctly positioned captive needle pistol. Furthermore, it is recommended to immobilize the stunned fish by chilling, as the post‐stun clonic cramps may hinder gutting and filleting.  相似文献   

三起违法经营、运输病死猪案件的查处与思考     

陈炳中 《中国动物检疫》2016,33(1):37-39

福建省漳州市长泰县动物卫生监督所与公安等部门联合执法,查处了三起违法经营、运输病死猪的案件,通过分析讨论此类案件的法律适用和查处方法,认为收集病死猪用于养殖埃及胡子鲶应当属于经营病死猪行为,应依据《食品安全法》、《动物防疫法》和《饲料和饲料添加剂管理条例》进行查处。  相似文献