Effect of combined photoperiod, water calcium concentration and pH on survival, growth, and moulting of juvenile crayfish (Procambarus clarkii ) cultured under laboratory conditions

The red swamp crayfish, Procambarus clarkii (Girard), is one of the most commonly farmed freshwater species in inland China due to its high market value and consumer demand. The aim of this study was to determine the optimum combinations of photoperiod, water calcium concentration and pH for juvenile survival, growth and moulting. In our orthogonal experiment, the three environmental factors were varied at three levels (photoperiod: 16L:8D, 12L:12D and 8L:16D; calcium concentration: 45.5, 65.5 and 85.5 mg L⁻¹; and pH: 6.8, 7.8 and 8.8). Range analysis showed that the maximum survival of juvenile crayfish occurred at photoperiods of 16L:8D or 8L:16D, water calcium concentration of 45.5 mg L⁻¹ and pH of 7.8; maximum weight gain at photoperiod 16L:8D, water calcium concentration 65.5 mg L⁻¹ and pH 7.8; maximum length increase at photoperiod 16L:8D, water calcium concentration 65.5 mg L⁻¹ and pH 7.8; and the highest moult frequency at photoperiod 12L:12D, water calcium concentration 65.5 mg L⁻¹ and pH 7.8. Analysis of variance indicated that photoperiod, water calcium concentration and pH significantly influenced only the weight gain of juvenile crayfish ( P <0.05). Taking growth into consideration, we suggest that a photoperiod of 16L:8D, calcium concentration of 65.5 mg L⁻¹ and pH 7.8 might be optimal conditions for rearing juvenile P. clarkii .     

Effects of dietary l-tryptophan on the agonistic behavior,growth, and survival of freshwater crayfish Astacus leptodactylus Eschscholtz

In this study, the effects of dietary tryptophan (a precursor of 5-hydroxytryptamine, 5-HT, serotonin) on the agonistic behavior, growth, and survival of freshwater crayfish were investigated. For this aim, a control diet (D1) and three experimental diets (D2, D3, and D4) were prepared. D1 contained no additional tryptophan (TRP), but D2, D3, and D4 diets were supplemented with TRP at 0.50, 0.75, and 1.00 % in dry diet, respectively. The control contained 0.33 % TRP. Results revealed that higher supplemental dietary TRP levels caused a significant decrease in the aggressive behavior (P < 0.05), but an increase in the calmness of crayfish. In addition, the results showed that 5-HT levels in the hemolymph before the fight (after 15 days of feeding; resting) were significantly different (P < 0.05) between D1 and D4. There was a significant difference (P < 0.05) in the 5-HT level of hemolymph between the crayfish fed control and D4 after 15 days of feeding. However, after the fight, 5-HT concentration was significantly higher (P < 0.05) in TRP-supplemented A. leptodactylus as compared with the control. The findings of this study showed that supplemental dietary TRP caused a significant increase (P < 0.05) in the growth and survival rate of A. leptodactylus. The crayfish fed D4 had the best survival rate at the end of the experiment (91.60 % in August). The findings of this study also showed that difference in survival rate between the crayfish fed control and D2 in June, July, and August was not significant (P > 0.05). In addition to these, supplemental dietary TRP gave rise to significantly higher specific growth rate (SGR) values in June and July (P < 0.05). For example, in June, it was 0.38 for the crayfish fed D4, 0.28 for the crayfish fed D3, 0.18 for the crayfish fed D2, and 0.13 for the crayfish fed control. However, in August, the highest SGR (0.56) was obtained from the crayfish fed control. The results also showed that the SGRs of females were lower than the males in June, July, and August (P < 0.05). In conclusion, this research shows that the aggressive behavior of A. leptodactylus can be suppressed, and rearing efficiency (i.e., increased growth and high survival rate) of this species can be improved by increasing TRP levels to 1.00 % in its diet.     

Effect of dietary supplementation of calcium chloride on growth,survival, moulting frequency and body composition of narrow‐clawed crayfish,Astacus leptodactylus (Eschscholtz, 1823)

The effects of dietary calcium chloride (CaCl₂) concentration on the growth, survival, moulting and body composition of Astacus leptodactylus were studied. Diets were prepared using supplementation of 0 (control), 30, 60 and 120 g kg^?1 calcium chloride commercial trout larvae diet containing 50% protein and 12% lipid. Astacus leptodactylus larvae with an average total length of 22.0 ± 0.05 mm (TL) and weight of 0.53 ± 0.01 g obtained from eighteen ovigerous females collected from Seydisehir Sugla Dam lake in Konya, Turkey, were stocked in 0.2‐m² aquariums at a rate of 50 crayfish m^?2 and reared for 90 days. The experiments included four treatments (diets) with three replicates each. Calcium chloride exerted positive effects on growth, moulting frequency, feed efficiency and survival of narrow‐clawed crayfish. Crayfish fed with 60 g calcium kg^?1 calcium chloride‐supplemented diet exhibited the highest weight gain and specific growth rate (SGR) but the lowest survival rate (63.3%) (P < 0.05). There were no significant differences (P > 0.05) in mean moisture (803.5 g kg^?1) and protein content (177.0 g kg^?1) in crayfish tail meat. However, lipid values were between 3.8 and 11.6 g kg^?1 and significantly different among the diets (P < 0.05). Diet with 60 g kg^?1 calcium chloride is recommended for the best growth of freshwater crayfish.     

Effects of food concentration and temperature on development,growth, reproduction and survival of the copepod Pseudodiaptomus euryhalinus

A series of experiments were conducted to evaluate the effect of temperature and the microalgae Isochrysis sp. concentration on the copepod Pseudodiaptomus euryhalinus cultured in laboratory conditions. First, the ingestion rate of P. euryhalinus was evaluated with different concentrations of Isochrysis sp. [2.74, 5.47, 8.21, 10.94 and 16.41 µg mL^?1 organic dry weight (ODW)] during 24 h, at a temperature of 24.3 ± 0.3 °C. The ingestion rate increased in direct proportion to microalgae concentration, reaching an asymptotic point at 16.41 µg mL^?1. P. euryhalinus was then cultured for 11 days at 24.4 ± 0.3 °C with different concentrations of Isochrysis sp. (5.47, 8.21, 10.94 and 16.41 µg mL^?1 ODW) in order to quantify the optimal food density. It was observed that food concentration did not have a significant effect on the development, growth, maturity, fecundity and survival of P. euryhalinus. The effect of different temperatures (19.4 ± 0.5, 21.9 ± 1.0, 24.2 ± 0.3, 27.8 ± 0.5 and 30.1 ± 0.8 °C) on the development, growth, survival and sex ratio of P. euryhalinus fed with Isochrysis sp. at 5.47 µg mL^?1 ODW was evaluated for 11 days of culture. The temperature had an inversely proportional effect on the time of development, and highest survival and growth were observed at 24.2 ± 0.3 °C. Finally, the effects of different temperatures (21.7 ± 0.5, 24.2 ± 0.3, 27.2 ± 0.3 and 30.7 ± 0.6 °C) in nauplii production of adult copepods were evaluated during 11 days. Nauplii production increased in direct proportion with the temperature. These results suggest that the optimum temperature and food concentration for P. euryhalinus culture are 24.2 ± 0.3 °C and 5.47 µg mL^?1 ODW of Isochrysis sp., respectively.     

Effects of soluble dietary cellulose on specific growth rate,survival and digestive enzyme activities in three freshwater crayfish (Cherax) species

The current study evaluated the effect of soluble dietary cellulose on growth, survival and digestive enzyme activity in three endemic, Australian freshwater crayfish species (redclaw: Cherax quadricarinatus, marron: C. tenuimanus, yabby: C. destructor). Separate individual feeding trials were conducted for late‐stage juveniles from each species in an automated recirculating freshwater, culture system. Animals were fed either a test diet (TD) that contained 20% soluble cellulose or a reference diet (RD) substituted with the same amount of corn starch, over a 12‐week period. Redclaw fed with RD showed significantly higher (P < 0.05) specific growth rates (SGR) compared with animals fed the TD, while SGR of marron and yabby fed the two diets were not significantly different. Expressed cellulase activity levels in redclaw were not significantly different between diets. Marron and yabby showed significantly higher cellulase activity when fed the RD (P < 0.05). Amylase and protease activity in all three species were significantly higher in the animals fed with RD (P < 0.05). These results indicate that test animals of all three species appear to utilize starch more efficiently than soluble dietary cellulose in their diet. The inclusion of 20% soluble cellulose in diets did not appear, however, to have a significant negative effect on growth rates.     

Effects of dietary mannan oligosaccharide on the survival,growth, immunity and digestive enzyme activity of freshwater crayfish,Cherax destructor Clark (1936)

The aim of this experiment was to determine the effects of dietary supplementation of Bio‐Mos^® as a source of mannan oligosaccharide (MOS) on the growth, survival, immunity and digestive enzyme activity of freshwater crayfish, Cherax destructor (yabby). A basal diet and another diet with 0.4% of Bio‐Mos^® supplemented to the basal diet were formulated. Each diet was provided to eight yabbies (35.14 ± 0.48 g, initial weight) replicated 3 times in individual 250‐L plastic cylindrical tanks for a duration of 56 days. Each tank was provided with an independent recirculating water system filtered with a biological filtration. Growth parameters such as weight, specific growth rate and average weekly gain of Bio‐Mos^®‐fed yabbies were higher (P < 0.05) than yabbies fed the control diet. Total haemocyte count, granular cells and semi‐granular cells were also higher in the yabbies fed Bio‐Mos^® diet. Protease activity was higher in hepatopancreas, and amylase activity was higher in the guts of yabbies fed Bio‐Mos^® diet. The results implies that supplementation of MOS through Bio‐Mos^® can effectively improve growth and immunological condition of yabbies.     

水体中钙和镁对凡纳滨对虾幼体成活率和生长的影响

在相同饲养条件下,Ca2 浓度为494 mg/L时,幼虾增重效果显著(P<0.05);Mg2 浓度为1 185mg/L的增重效果显著优于1 135 mg/L水平;Ca2 浓度为444和494 mg/L时,分别对提高M3育成P1和P10的成活效果具有极显著作用(P<0.01);Mg2 浓度为1 185 mg/L和Ca2 浓度为494 mg/L(R=2.40)的交互作用对提高M3育成P10的成活效果最佳(P<0.01);Ca2 浓度为444和494 mg/L时,其R值可适范围分别为2.67~2.78和2.30~2.50。Ca2 浓度是影响凡纳滨对虾增重和成活的主要因子,但对体长增长无显著影响(P>0.05),其可适范围为444~494 mg/L;Mg2 浓度对凡纳滨对虾的生长影响均不显著;Ca2 浓度和Mg2 浓度的交互作用极显著影响凡纳滨对虾M3育成P10的成活率。     

温度对中间球海胆幼胆生存、生长和行为的影响

底播增殖是一种提高中间球海胆(Strongylocentrotus intermedius)产量的有效方法.底播增殖受到多种内在和外在因素的影响,其中温度发挥着十分重要的作用,因此确定中间球海胆适宜增殖温度范围至关重要.本实验将大(23.29±0.27)mm、小(18.78±0.19)mm两种规格的中间球海胆放置在3个...     

Effects of diet and sediment type on survival, growth and moulting of juvenile tiger crab, Orithyia sinica L.

This study investigated the effects of different types of diet and sediment on the growth parameters of juvenile tiger crab Orithyia sinica under laboratory conditions, focusing on survival, growth and moulting. In the first set of experiments, juvenile tiger crabs were reared with five different types of sediment, i.e., soft sand, coarse sand, soft sand mixed with coarse sand, mud or bare bottom. Soft sand resulted in not only the highest survival rate of 78% but also the best rate of growth and feed intake. Crabs reared with a mud substrate showed the worst results in these parameters. The intermoult period, however, was not affected by sediment types. In the second set of experiments, crabs were fed different types of diet to determine their effects on the same growth parameters. Diets were composed of different combinations with Manila clam (Ruditapes philippinarum), brine shrimp (Artemia nauplii), microencapsulated feeds and marine diatom (Chaetoceros gracilis). Survival and growth in crabs fed Manila clam as a diet component were significantly higher than in those on other diets. The highest survival and growth were achieved with a diet that included all four components. These results provide valuable information on the appropriate bottom substrates and diet types necessary for artificial mass culture of the tiger crab.     

Effects of ammonia and nitrite on survival, growth and moulting in juvenile tiger crab, Orithyia sinica (Linnaeus)

The effects of ammonia and nitrite on survival, growth and moulting were investigated in juvenile tiger crab, Orithyia sinica (carapace length 3.91±0.15 mm, carapace width 3.84±0.23 mm, n=440), after 30 days exposure to ammonia‐N (0, 20, 50, 100 and 150 mg L^?1) and nitrite‐N (0, 50, 100, 150, 200 and 250 mg L^?1) using a continuous flow system. Survival rates of tiger crab exposed to ammonia and nitrite decreased linearly with the exposure time and concentration. The growth rate of tiger crab exposed to 50, 100 and 150 mg L^?1 ammonia was significantly lower than that of control crabs. The growth rate of tiger crab exposed to nitrite decreased at 150, 200 and 250 mg L^?1 nitrite. During the ammonia and nitrite exposure, the intermoult period of the juveniles of tiger crab O. sinica was shortened between the first and second moult, and the number of moulting of crabs exposed to a higher concentration were significantly higher than that of control crabs.     

Effect of temperature and phytoplankton concentration of Partitioned Aquaculture System water on freshwater mussel filtration

The freshwater mussel Elliptio complanata was provided green algal‐dominated water from a Partitioned Aquaculture System (PAS) over a range of water temperatures (6.1–32.4 °C) and suspended particulate organic carbon (POC) concentrations (<1–32.2 mg C L^?1) to determine filtration rates as mg POC kg^?1 wet tissue weight h^?1. The lowest filtration rates were observed at lowest temperatures and POC concentrations while the highest rates were at intermediate temperatures and the highest POC levels. The predicted filtration rate (PFR) in response to water temperature and POC concentrations was as follows: ln PFR=1.4352+0.1192 POC+0.1399 T?0.0001 T³. Within the experimental conditions, PFRs at any POC concentration increased with increased water temperature to a peak at 22 °C and then decreased. The maximum PFR occurred at 22 °C and 32 mg C L^?1 and the minimum PFR at 7 °C and 1 mg C L^?1. A model to describe the mussel filtration rate responses to PAS water conditions involves both water temperature and POC concentration.     

A comparison of the growth and survival of two freshwater crayfish species, Astacus leptodactylus Eschscholtz and Pacifastacus leniusculus (Dana), under different temperature and density regimes

Growth experiments carried out with two juvenile crayfish species, Astacus leptodactylus Eschscholtz and Pacifastacus leniusculus (Dana), at different temperatures and densities highlighted the problem of cannibalism under conditions aimed at intensifying crayfish production. Cannibalism proved to be much lower in A. leptodactylus than P. leniusculus, suggesting that the former might be the better candidate for astaciculture. In the first of two population survival trials, A. leptodactylus showed a higher survival rate than P. leniusculus, with 26% of P. leniusculus surviving in the first replicate, compared to 42.3% of P. leniusculus, and 40.76% surviving in the second replicate, compared to 47.6% of P. leniusculus. The same trend was observed in the second experiment, with P. leniusculus showing survival rates of 48.5 and 55.3% (first and second replicates, respectively) in comparison to 65.2 and 68.2%, respectively, for A. leptodactylus. It is therefore highly likely that if P. leniusculus were to become established in Turkey, it would outcompete the native A. leptodactylus even if it were not to be devastated by the crayfish plague that has decimated the native species. The experiments also highlighted the problem of differential growth, with some juveniles hardly growing at all while others reached a relatively large size. The range in carapace length (CL) was 9–18 mm for A. leptodactylus and 8.5–18.5 mm CL for P. leniusculus at the end of the first experiment. While both species grew quickly, P. leniusculus hatched earlier, giving it an advantage over A. leptodactylus; consequently, by the end of the summer, the juveniles of the former were larger than those of A. leptodactylus. Specific growth rate values showed that the juveniles of the two species had similar growth rates. The results also revealed that growth was not significantly affected by density in both species at 15°C, but at 25°C, growth was significantly better at a density of 234 juveniles m⁻² than at 468 juveniles m⁻², and better at 468 juveniles m⁻² than at 937 juveniles m⁻² (P < 0.01 and P < 0.001, respectively). We conclude that P. leniusculus is a good candidate for aquaculture as it has a rapid growth rate and early hatching and maturity; however, its aggressive behavior may make it a less attractive proposition than A. leptodactylus, which is also fast growing but less aggressive. This study is a part of PhD study of M.M. Harlıoğlu, who is supported by Fırat University Elazığ, Turkey.     

Effect of high water temperature on the survival, moulting and food consumption of Penaeus (Marsupenaeus) japonicus (Bate, 1888)

The kuruma shrimp, Penaeus (Marsupenaeus) japonicus (Bate, 1888), is a valuable aquaculture species in Queensland, Australia. The shrimp is supplied live to the Japanese market and must survive emersed transport for up to 36 h. In-transit mortality after harvest from high water temperatures (> 30 °C) has been reported by the industry, and a knowledge of the effects of high water temperature may provide important information for producers on grow-out management, timing of production and farm location. Experiments were conducted to determine the effect of high water temperature on survival, moulting and food consumption in P. japonicus. Replicated groups of 15.6 ± 0.2 g shrimp were acclimated and exposed to five temperatures, between 28 and 36 °C, for up to 28 days. Mortality was highest at 36 °C and equally lowest between 28 °C and 32 °C. Intermoult period was not significantly different for temperatures between 28 and 32 °C (19.8–15.5 days) but was significantly greater above 32 °C (27.4 days at 34 °C and > 104 days at 36 °C). There was evidence of moulting synchrony at 28 °C. Mean daily food consumption was highest at 32 °C at 2.34% of body weight, but decreased to 1.56% at 28 °C and 1.33% at 36 °C. Over the range of water temperatures examined, survival, moulting rate and food consumption were highest at 32 °C.     

Effect of dietary protein level on growth and survival of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda: Parastacidae)

Protein requirements of juvenile freshwater crayfish Cherax quadricarinatus, with initial mean weight of 1.08 ± 0.34 g, were studied. Juveniles were fed experimental diets containing seven levels of crude protein (CP) (20, 25, 31, 37, 43, 49, and 55%) and 18.73–21.45 kJ  g^?1 of gross energy. The highest mean weight and specific growth rate (SGR) (P < 0.05), with values of 9.6 g, and 3.64% day^?1, respectively, were achieved by feeding a diet of 31% CP. This diet resulted in a survival rate of 80% over 60 days of culture at 27 °C. The higher protein level tested (55% CP), yielded a significantly (P < 0.05) lower mean weight of 6.4 g. However, there were no significant differences in SGR among the 20, 25, and 49% CP diets. Feed Conversion Ratio (FCR) was close to 1 for all treatments except the lowest (20%) and highest (55%) CP. Optimum protein requirements were estimated by fitting mean weight gain data to a quadratic model (y = 1.142+0.484 ? 0.0071x², r² = 0.952, P < 0.05). Optimal growth occurred with 34.2% CP, but the results suggest that optimum protein level for 1‐g juvenile C. quadricarinatus is 31% in least‐cost diets. The information obtained will contribute to the formulation of diets that will enhance production of C. quadricarinatus.     

海水养殖对近岸生态环境的影响

文章研究了从硝化菌群中分离的菌株NB5在不同培养条件下的生长情况及其对氨氮 (NH₄ ⁺-N) 和亚硝氮 (NO₂ ⁻-N) 的去除效果,并对菌株NB5进行了鉴定。结果发现,菌株NB5在盐度25~45、pH 6.0~9.0、15~35 ℃和通气量1~2 L·min⁻¹的条件下生长良好 (P>0.05)。在盐度45、35和25条件下对NH₄ ⁺-N的最大去除率分别为96.24%、88.93%和75.08%;pH 7.5和9.0条件下分别为99.53%和99.37%;温度30、25、15和35 ℃条件下分别为99.53%、97.22%、97.29%和71.26%;通气量为2和1 L·min⁻¹时分别为99.87%和99.82%。在上述培养条件下菌株NB5对NH₄ ⁺-N的最大去除率均显著高于对照组和其他条件组 (P<0.05)。菌株NB5在不同培养条件下对NO₂ ⁻-N浓度变化无显著作用 (P>0.05)。经16S rDNA序列分析,菌株NB5鉴定为海水硝酸盐还原菌 (Nitratireductor aquimarinus)。研究表明,菌株NB5具有较好的环境适应性和氨氮去除效果,尤其适合中高盐度 (25~45) 养殖池塘环境。

     

不同温度和光周期对三疣子蟹幼体成活度的影响

利用容积为500ml的微流水装置,放入50个同一批三庞梭子蟹(Portunus,trituburculatus)蚤状幼体(Z1～Z1)和大眼幼体(M),温度控制在室温(18.0℃～27.5℃)、20℃、23℃、26℃、29℃和32℃,光周期控制在室温0h、6h、10h、14h、18h和24h,常规管理观察幼体成活率.结果表明,Z1、Z2、Z3、Z4和M在温度和光周期分别为20℃、18h～24h;21℃～23℃、18h ～22h;23℃～26℃、14h～24h和23℃～26℃、18h时,变态率较高.     

Distribution of freshwater crayfish in the British Isles,with particular reference to crayfish plague,alien introductions and water quality

1. The distribution of native and alien crayfish in the British Isles, based on records from 1970–1991, is figured at the 10 km square level and that for Britain is tabulated regionally. 2. Since 1981 crayfish plague has been recorded from six catchments in Britain and one in Ireland, and suspected from an additional four catchments in Britain; 56.2% of native crayfish sites in Britain occur in catchments from which plague has been confirmed. 3. Since the mid-1970s approximately 300 signal crayfish implants have been made in Britain. Only 117 “successful” implants of signals are known to the authors; 39 crayfish farmers were registered in 1986 and 68 by 1990. In 1989 declared production was approximately 7 tonnes. 4. Some mixed populations of natives and disease-free signals exist. Evidence for exclusion of natives is being monitored. 5. Signal crayfish are found in the flowing waters of seven catchments; 58.1% of native crayfish sites are located in catchments which support farmed and wild populations of signals. Some rapidly-expanding Turkish crayfish populations are known, particularly in the Thames catchment. 6. At least 87% of native crayfish records are from good quality waters. 7. Native populations from 88.6% of sites recorded in Britain since 1970 have either been eliminated, or are directly threatened, by crayfish plague infection, and/or habitat invasion by signals, and/or pollution. 8. The native crayfish was added to the list of species protected under the Wildlife and Countryside Act in 1986. 9. Recommendations to assist in the conservation of the native crayfish include a ban on future imports of alien crayfish, a reassessment of records, the setting up of “no-go” areas, the protection of isolated sites, and a restocking programme. 10. There are many restrictedt, healthy populations of native crayfish in areas which could be protected by designating them as Sites of Special Scientific Interest (SSSIs).     

水温对东星斑幼鱼存活、摄食及生长的影响

在实验室条件下,初步研究了水温对东星斑幼鱼摄食、生长及存活的影响。温度设5个水平(15、20、25、30、35℃),东星斑幼鱼在玻璃蓄养槽内养殖40d。结果显示20℃组、25℃组和30℃组的鱼没有死亡,35℃组的存活率为88.9%,15℃组的存活率仅为50%;总摄食量在30℃组最高,15℃组最低;特定生长率在30℃组最高,15℃组、35℃组为负值;在可以生长的组别里,30℃组饵料系数最小。本研究表明,水温对东星斑幼鱼生长发育的影响明显,东星斑的适宜摄食温度为20～30℃,最佳摄食温度为25～30℃;水温<20℃东星斑幼鱼不能正常摄食、生长,甚至会死亡,水温15℃时,几乎不摄食;水温>30℃,东星斑幼鱼可以正常摄食,但是不能正常生长,甚至会死亡。     

温度变化对斑点鳟鲑仔鱼存活与生长的影响

本文研究了温度变化对斑点鳟鲑仔鱼存活与生长的影响。结果表明,温度变化对斑点鳟鲑20日龄仔鱼存活与生长有明显的影响,20日龄仔鱼在水温10～26℃范围内均能存活、生长。最适水温为14～22℃,在适温范围内幼鱼具有较高的存活率和生长率,温度过高或过低均对其生长发育有抑制作用,在(18±0.5)℃时生长率达到峰值,为0.93mm/d。     

Effects of replacement of animal protein by soybean meal on growth and carcass composition in juvenile Australian freshwater crayfish

A feed trial was conducted for 59 days with juvenile Cherax destructor, mean weight (se) 0.61 (0.01) g, reared communally and maintained on 16 isoenergetic diets containing crude protein levels of 15, 20, 25, and 30%. For each protein level the fish meal component was replaced by soybean meal to produce diets in which 0, 20, 40, or 60% of the protein originated from soybean meal. Mean percentage weight gain per day ranged from 2.98% (15% protein, 60% soybean meal diet), to 11.75% (30% protein, 40% soybean meal diet). When soybean meal was included at a level of 40–60%, growth rate was reduced relative to that achieved with control diets at 15% and 20% protein levels. In no case did a 20% substitution significantly affect growth over that achieved with controls. A two-way interaction occurred between dietary protein and the level of dietary soybean meal. Feeds of higher protein content appeared to permit higher soybean meal inclusion levels without significantly affecting growth. Increases of 5% protein produced a significant improvement in growth when soybean meal contributed from 40–60% of the total protein. This effect was less pronounced in the control diets and the 20% soybean meal series. The percentages of protein increased and lipid decreased in the carcass as the level of dietary protein increased. A similar effect occurred by increasing the soybean meal substitution level to 60%. An obvious trend in carcass moisture, energy, and ash did not occur. A protein requirement of 30% is apparent when fish meal and soybean meal are included in diets at levels of 20% and 24% respectively. A maximum weight of 14.13 g was recorded for an individual fed the 30% protein, 20% soybean meal diet.