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The Egyptian government is committed to the development of rice field fish culture systems as means of protein production. Trials on the growing of common carp (Cyprinus carpio L.) were conducted in Gharbia governorate in the middle of the Nile delta. The trials reported here have shown that fish could successfully be reared in the Egyptian rice fields. Different stocking rates were used varying from less than 1000 up to 5500 fry/ha. The relation between different stocking rates and final fish weight, length, mortality and production of fish was studied. With stocking rates over 20000 a significant reduct (P < 0.001) in fish weight, and length was observed and mortality also increased (P < 0.02). Supplementary feeding at stocking rates of over 2000 fry/ha resulted in a partial restoration of fish weight and length (P < 0.001). Feeding reduced mortality from 46.2 to 33.5%. The data indicates an increase in fish production with the increase in stocking rate up to 100/ha but there were insufficient trials to give a statistically significant results. The highest production achieved in the trials without feeding was 167 kg/ha with a mean value of 88 kg/ha. The highest production of all trials was 264 kg/ha in a fertile area with supplementary feeding and with additional dose of organic manure. A strong relation was found between carp growth and the quantity and quality of natural food in the rice fields. Carp grew rapidly following introducing with a specific growth rate of 24% /day but this fell to 4% per day by the middle of the season, towards the end growth fell to zero or even negative values corresponded with the depletion of the community of invertebrate food organisms. The abundance of phytoplankton in the rice fields could provide a rich environment for raising other species of fish such as silver carp (<i>Hypophthalmichthys molitrix</i>) and <i>Sarotherodon niloticus</i>. Significant numbers of accidentally introduced fish of other species, were found (<i>Clarias lazera</i>; catfish), Tilapia spp., <i>Lates niloticus</i>, Nile perch), the rice field could be a reliable source of tilapia fry in addition to consumption carp. With the development of cage culture system an integration between rice fish culture and cage culture could potentially be achieved with the small fish obtained at the end of the growing season could be restocked in cages. The average additional income obtained from the introduction of carp to the rice fields represent an increase of more than 20%. This profit was obtained with as little as 2.31% increase in the total costs of rice and fish. In addition less labour was needed for weeding, with one weeding instead of the normal three.

This thesis examines protein metabolism and growth in decapod crustaceans; protein synthesis being investigated by a flooding dose of tritiated phenylaline. Using three isoproteic diets, the effect of dietary protein on protein synthesis and growth of juvenile shrimps <I>Penaeus vannamei</I> was investigated. Survival, specific growth, and protein synthesis rates were higher (and protein degradation was lower) in shrimps fed a fish/squid/shrimp meal diet, or a 50% laboratory diet/ 50% soybean meal variant diet, than in those fed a casein-based diet. The efficiency of whole body protein retention was 94% for shrimps fed the fish meal diet suggesting that crustaceans have a low protein turnover and a high protein growth efficiency. These data suggest lower costs and consistent availability of soybean meal provides an attractive alternative to a more expensive, fish protein based, feed. However protein retention was only 80% for those fed the casein diet, the amino acid profile of which was poorly correlated with that of the shrimps. The effects of low and high rations on food consumption and protein synthesis in crabs (<I>Carcinus maenas</I>) fed either mussels or salmon were examined. With the mussel diet, the daily variability in the amount of food obtained by individuals decreased as the quantity of food provided to the group was increased. The opposite occurred for the salmon diet; i.e. the diet with the enriched protein source. Thus the nutritional status of the diet influenced appetite. The effect of feeding frequency on growth and protein metabolism in the European lobster, <I>Hommarus gammarus</I>, was investigated. A feeding regime comprising of a single daily ration of 10% of body weight, of an artificial diet, resulted in optimal growth. This was found to be the result of decreased protein degradation, rather than increased protein synthesis. The results suggest that lobsters are slow, periodic feeders and that growth can be readily increased by manipulation of particular environmental factors such as feeding frequency, space and photoperiod.

1. Investigations have been carried out into mechanisms underlying rapid hypercalcaemic actions of parathyroid hormone (PTH) and prostaglandins (PGs) in chicks (12 day old), and in a limited parallel study, immature (4 week old) rats <i>in vivo</i>. 2. Intravenous (i.v.) injection of synthetic bPTH(1-34) (3.3μg/100g body wt.) or 16,16-dimethyl PGE_2 (5-20μg/100g body wt.) caused hypercalcaemia within 15 minutes in chicks. The PG, but not PTH, also elevated plasma P<SUB>i</SUB> levels at early (15-90 min.) time intervals in chicks. Similar but less sensitive plasma Ca and P<SUB>i</SUB> responses occurred following i.v. injection of these agents into rats. bPTH(1-34) and 16,16-dimethyl PGE<SUB>2</SUB> had little effect on plasma osmolality in chicks, indicating the relative specificity of their actions on plasma Ca and P<SUB>i</SUB>. 3. Studies were carried out using a combination of acute <SUP>45</SUP>Ca labelling (injected i.v. with hormone) and microwave fixation to stabilize tissue isotope levels after death. In the absence of hormones, <SUP>45</SUP>Ca was rapidly taken up by the skeleton in preference to a variety of soft tissues. Bone and soft tissue <SUP>45</SUP>Ca uptake was greater in non-microwaved compared with microwave fixed chicks. 4. bPTH(1-34) (0.36-3.3μg/100g body wt.), 16,16-dimethyl PGE_2 (0.55-5μg/100g body wt.), and a range of natural PGs (PGE<SUB>2</SUB>, PGE<SUB>1</SUB>, PGF<SUB>2α</SUB>, PGI<SUB>2</SUB>) (5-20μg/100g body wt.) each inhibited net ^45Ca uptake by femur and calvarium within 3 minutes in chicks. Purified bPTH(1-84) (10μg/100g body wt.) and synthetic hPTH(1-34) (3.3μg/100g body wt.) also showed a tendency to inhibit chick bone net ^45Ca uptake at early (3-15 min.) time intervals. Responses to bPTH(1-34) and 16,16-dimethyl PGE_2 were reflected by plasma retention of the acutely injected ^45Ca label compared with controls.

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