摘要:

Abstract.During three 5‐month experiments in Thailand, earthen ponds of approximately 370m2 surface area were stocked with male Nile tilapia, Oreochromis niloticus (L.), fingerlings of 4–12g weight at densities of 0·5 to l·6fish/m2. Stocking and fertilization (with chicken manure, urea and TSP) in triplicated depth treatments of 0·6,1·0 and 1·5m were proportional to pond volume in two experiments (wet and dry seasons) and to pond area in the other (dry season).Depth showed no direct effect on fish yields of 0·9–6·3t/ha/year, on survival rates of 66 to 98%, nor on final individual weights of 96–313 g/fish. Greater yields were obtained from deeper ponds when they received proportionally greater stocking and fertilizer inputs. Inputs per unit area were the most important factor accounting for yield variation.Temperature, dissolved N and P, and suspended solids showed little or no relation to depth treatments. Time‐averaged chlorophyll concentrations and photosynthetic production of dissolved oxygen were greater in treatments receiving greater inputs of nitrogen per unit pond volume.Deeper ponds produced the greatest areal yields of fish, when fertilized in proportion to their volumes. Shallow ponds produced fish and dissolved oxygen at least as efficiently per unit input as did deep ponds, which is consistent with models of photosynthesis

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00752.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.This paper examines the digestibility of different feed mixtures by three species of fish: carp,Cyprinus carpioL., tilapia,Oreochromis aureus×O. niloticus, and African catfish, Clarias gariepinus (Burchell 1822). Protein from poultry sources was digested better by tilapia than by carp or catfish, but no significant difference was found in the case of protein mainly from fish meal. Carp showed the best ability to digest fats, followed by catfish, with tilapia having the least ability. Tilapia digested carbohydrate better than the other two species, however, whether from wheat or corn sources. The same pattern applies to the digestibility of energy

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00753.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The growth and survival ofClarias gariepinus(Burchell) fry was investigated at high stocking density. Significant increases in mean fry weight, and concomitant significant decreases in specific growth rate, were recorded over successive 5‐day periods. Fry growth was negatively density dependent. Fry survival was in excess of 90% in all treatments. Increasing stocking density between 50 and 150 fish/l altered the pattern of mortality; non‐cannibalistic deaths decreased significantly with increasing stocking density though cannibalism did not significantly increase. Periods of weaning fish onto larger feed particles were associated with temporarily increased rates of cannibal

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00754.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Newly hatchedChanna striatus(Bloch) were tested for survival and growth under various delayed feeding regimes.Channa striatuslarvae were found to be extremely tolerant to the delay in initial feeding. About 9% of the larvae died when initial feeding was delayed by 2 days after yolk absorption. However, mortality progressively increased with further delays in first feeding. Only 26% of larvae took food when it was offered 11 days after yolk absorption.‘Point of no Return’was reached only on the 14th day of starvat

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00755.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Chinese catfish,Clarias fuscus(Lacepède), within three size ranges were evaluated for growth, survival and feed conversion ratios (FCR). A 4 × 3 factorial design was used during year‐long trials which included four temperatures (20,25,30 and 35 °C) and three feeding rates with commercially formulated salmon/trout feed. Specific growth rates of juvenile fish (1–60g) were highest, ranging from 1–64% body weight/day at 20°C (2%/day feed rate), to 4–94%/day at 25°C (6%/day feed rate). Specific growth rates of sub‐adult fish (60–150g) averaged 0–65%/day, with no significant difference between temperature‐feed rate treatments. Specific growth rates of adult fish (>150g) were lowest, averaging 0–30%/day for grouped feed rate treatments at 25°C, and 0–16%/day at 30°C. Most mortalities occurred during the juvenile stage, with survival ranging from 0% at 35°C(2% feed rate) to 96% at 30°C(6% feed rate). Survival was 95–100% with sub‐adults and adults. FCR were 1 to 4 with juveniles, 2 to 12 with sub‐adults, and 3 to 22 with adults. These trials suggest that optimal growth and FCRs were obtained at 25°C; with feed rates of 6%/day with juveniles, 2%/day with sub‐adults, and 1%/day with adult fish. Final yields at 25 and 30°C indicate that even though growth and FCR are optimal at 25°C, survival was greater at 30°C, which compensated for reduced growth performance at this temperature. Yields at 25 a

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00756.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.One hundred specimens of the European seabass.Dicentrarchus labraxL., from a natural population (Cádiz, Spain) were analysed by starch gel electrophoresis for 23 enzymes; 49 loci were identified, of which five were polymorphic (ADH*, AAT‐3*, EST‐.3*, MEP‐1* and SOD‐2*) P = 10·2% and HQ = 1·8%. Twenty specimens from a hatchery at Tinamenor in northern Spain (Fl progeny from wild) were analysed for 28 different enzymes. A total of 61 loci were identified of which 4 were polymorphic (LDH‐1*, LDH‐2*, MEP‐1*, and XDH‐2*) P = 6·6%,Ho= 1·5%. A total of 31 enzyme systems and 79 different loci were analysed in the two populations. The results suggest that the Cádiz and Tinamenor stocks are reproductively isolated and show a level of stock differentiation not previously known in populations of this species. An estimate of genetic distance based on the 31 loci compared in both populations gave a value of D=0·012+0·018 and a genetic similarity of I=0·988. The implications of these results for fisheries and aquacultu

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00757.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Tiger shrimp, Penaeus monodon Fabricius, post‐larvae (32·0±3mg, 1·43±0·03 cm) were exposed to control, 0·12, 0·60, 1·20 and 2·40mg/l ammonia‐N (un‐ionized plus ionized ammonia as nitrogen) which is equivalent to control, 6,32,63 and 126μg/1 NH3‐N (un‐ionized ammonia as nitrogen) for 8 weeks in 25 ppt, as pH of 7·85–8·18 and 26–28°C by static renewal method. Growth in weight and length of the shrimps exposed to 1·20 and 2·40 mg/l ammonia‐N were significantly lower (P<0·05) than those exposed to control. The EC50(concentration that reduced growth by 50% of that of the controls) was 1·33 mg/l ammonia‐N, 70 μg/l NH3‐N for weight gain, and 2·35 mg/1 ammonia‐N, 123μg/l NH3‐N for length gain of P. monodon post‐larvae. The‘maximum acceptable toxicant concentration’(MATC) of ammonia‐N and NH3‐N for P. monodon post‐larvae was 0·6

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00758.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Eyestalk‐ablated and non‐ablated pond‐rearedPenaeus monodonFabricius of two sizes (116·3 ± 2·8g and 67·9 ± 1·0g body weight (BW)) were injected with crude thoracic ganglion extract from 'spent spawners’(0·4mg/g and 1·0mg/g shrimp respectively). Controls (ablated and non‐ablated groups) received either equivalent amounts of crude muscle extract or crustacean saline.In another experiment, non‐ablatéd shrimps (67·4 ± 1·8g BW) were injected with crude gonad extract from 'spent spawners'. The controls received an equal volume of crustacean saline.Significant differences (P0·05) observed between the gonad‐treated group and the control and between the two control groups receiving crus

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00759.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.This study explored the feasibility of completely replacing live foods with an artificial diet for rearing the larvae ofMetapenaeus ensis(de Haan) andPenaeus chinensis(Osbeck). The artificial diets tested were a microparticulate diet developed at the Centre Océanologique du Pacifique, Tahiti, and Artificial Plankton B.P. (Nippai Shrimp Feed Inc., Japan). Survival and development of shrimp were assessed in 1‐l cones stocked with 100 nauplius V‐VI or protozoea I larvae. Live feeds of the diatomChaetoceros gracilisandArtemianauplii served as controls. Whereas the larvae could be reared to post‐larvae with artificial diets alone, the highest survival and development rates were always obtained with live foods. Larvae fed with artificial diets had retarded development and their survival to post‐larvae was always lower than those fed live foods. Total replacement of live foods with artificial diets resulted in a reduction in the body length of post‐larvae I inP.chinensis. Supplementing Artificial Plankton B.P. withArtemianauplii enhanced survival and development in this species. It was concluded that the two artificial diets are not satisfactory complete substitutes for live foods in raising the two penaeids but can be used as a convenient supplement when algal diet

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00760.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Information on carapace length (CL) and its variability at each instar from settlement (instar 4) to pre‐recruit size (instar 24) is presented for 10 individually reared single parent broods and one mixed brood of European lobster,Homarus gammarus(L.). The lobsters grew from 5mm CL to 74mm CL in approximately 130 weeks at 20°± 2°C. There was some evidence that growth variability of the largest lobsters was influenced by the size of the rearing compartments used during the final growth pe

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1991.tb00761.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY