摘要:

AbstractGrowth and survival rates of smallmouth bass (Micropterus dolomieui) were compared for fishes reared from larval stages, for three weeks using different feeding regimes. Diets consisted of a commercial dry diet formulated for larval fishes, the dry diet plusArtemia salinanauplii, andArtemia salinanauplii alone. Smallmouth bass on the three diets showed average daily gains of 0.7, 0.7 and 0.5 mm/day and 11.0, 11.4 and 5.2 mg/day, respectively. Condition factors for the three diets were not significantly different (P>0.05). Mean survival rates were 39, 85 and 77% respectively.

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb00516.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractChinese catfish (Clarias fuscus) were successfully spawned in Hawaii using human chorionic gonadotropin (HCG) at dosage rates of two and four international units (IU) per gram body weight. Fish not injected with HCG did not produce viable eggs. Successful spawns with HCG occurred between May and October. Hatch rates of up to 80% were obtained during June, July, and August for those fish given either a 2 or 4 IU per gram body weight injection of HCG. Fish spawned in either May or October yielded significantly higher hatch rates when injected with 4 rather than 2 IU per gram body weight. Fish held at elevated temperatures (28 to 30 C) prior to the normal spawning season developed significantly larger oocyte diameters, 60 days earlier than fish held under ambient temperature conditions (21.5 to 24 C). Photoperiod manipulation at ambient temperature conditions was associated with earlier oocyte maturation, but photoperiod effects were much less important than temperature.

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb00517.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractModels describing the food uptake kinetics of a growingArtemiaculture and the hatching rate ofArtemiacysts are combined to yield equations capable of predicting the effects of variable algal cell concentration upon the growth rates of brine shrimp cohorts. The model illustrates that the feeding ability of the brine shrimp can be viewed as one becoming increasingly more efficient as the animals mature. This increasing efficiency in a population of variable age animals (from a single hatch) results in accelerated growth of first hatched animals relative to later hatched animals, especially at algal cell concentrations below certain threshold values. Growth rates of variable age groups of brine shrimp are mathematically manipulated to predict variable size brine shrimp at low algal cell concentration and uniformly sized brine shrimp at high algal cell concentration. This predicted result is confirmed with data fromArtemiagrowth trials at high and low algal cell concentrations. It is suggested that similar variations in population attributes of other species may be explained as an animal‐food interaction in which minor initial variations in individual animal maturity (weight, size, etc.) are magnified as a consequence of continuous competition for a common pool of foo

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb00518.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of continuous paddlewheel operation on shrimp growth, yield and crop value were studied in Hawaii. Six 0.4 ha earthen ponds were stocked withPenaeus vannameiat 25 postlarvae/m2. Three ponds served as controls with no mechanical aeration or mixing. Each of the other three ponds had two 1 hp paddlewheel aerators (3.7 kw/ha) running continuously throughout the five month trial (29 April‐8 October 1986). All other management factors were applied uniformly.Daily water temperature and use were significantly different between treatments. Paddlewheel ponds had lower water temperatures (28.3 vs. 28.5 C) and lower water use (0.8% exchange per day vs. 2.2% exchange per day) than control ponds.Faster shrimp growth in paddlewheel ponds was evident in week 8. At week 14, mean shrimp body weights and growth rates were significantly greater. Shrimp at harvest were 21.2 ± 2.6 g in paddlewheel ponds versus 15.3 ± 2.6 g in control ponds. Mean shrimp production was 2,852 ± 222 kg/ha in paddlewheel ponds compared to only 2,061 ± 558 kg/ha in controls. Mean crop value was $13,719 per pond per crop for paddlewheel ponds versus $9,111 for control ponds. Hence, paddlewheels afforded an increase of 42% in net crop value after subtracting purchase and operating

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb00519.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA commercial micropulverized 50% crude protein diet for penaeid culture was studied for biochemical oxygen demand and to assess its effect upon water quality in the hatchery and raceway environment. The feed was separated into 13 sizes ranging from 250 μm to 2 mm in diameter. The first order reaction rate constant (k) increased with decreasing particle size. The micropulverized feed was highly biologically reactive and the rate constant (k) varied from 0.1 to 0.24 day‐1, depending on the particle size. The ultimate BOD was 660 mg/g. The goal of this research was to predict the impact of this feed in relation to varying particle size upon the oxygen and ammonia dynamics of the water. This information will enable shrimp hatchery managers to more effectively assess the water quality impact and water replacement schemes when using artificial micropulverized fee

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb00520.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY