军曹鱼幼鱼日粮锌最适添加量的研究

在以卵白蛋白为蛋白源的基础饲料（Zn含量为5．65mg／kg）中添加10、20、30、40、50mg／kg以ZnSO4为Zn源的Zn,使饲料中总Zn含量为15．97、25．66、33．90、45．85、55．88mg／kg。投喂军曹鱼幼鱼8周。试验结果表明,基础饲料组鱼出现生长不良、厌食、皮肤糜烂和白内障等症状,其成活率、增重率、血清碱性磷酸酶活性（AKP）显著低于添加Zn组（P〈0．05）,骨骼、肌肉、血清和肝脏Zn含量也表现出相同趋势。10mg／kg和20mg／kgZn添加量组鱼仍出现缺Zn症状,各项测定指标随Zn添加量的增加而增大。当饲料中Zn添加量达到30mg／kg时,各项指标趋向稳定,与添加量40mg／kg和50mg／kg组无显著差异。以增重率和骨骼Zn含量为主要评价指标,通过回归分析表明,以ZnSO4为Zn源时,军曹鱼幼鱼日粮Zn的最适添加量为42．86mg／kg。     

Resistance of Cobia,Rachycentron canadum,Juveniles to Low Salinity,Low Temperature,and High Environmental Nitrite Concentrations

Abstract

Resistance of juvenile cobia, Rachycentron canadum, to low salinity, low temperature and high nitrite concentrations was examined under laboratory conditions. After acclimating juveniles to a salinity of 20 g/L (27.3°C), salinity was decreased by 2 g/L/day. The first fish died at a salinity of 8 g/L and 80% offish were dead within 24 hours of exposure to 2 g/L. Acclimation offish to 22.6°C (21 g/L salinity) followed by a temperature reduction of 0.53°C/day resulted in initial mortality at 12.9°C. The median-lethal temperature was 12.1°C and all fish were dead by the time the temperature reached 10.4°C. Fish exposed for 96 hours to nominal ? 32 mg/L nitrite-N survived. Results of this study indicate that cobia juveniles require a salinity and temperature of > 8.0 g/L and > 12.9°C, respectively, and that environmental nitrite should not be deleterious at concentrations normally found in aquaculture systems.     

军曹鱼幼鱼商品饲料中铁、锌适宜添加量的研究

在军曹鱼幼鱼商品饲料中添加铁100、200、300 mg/kg,添加锌30、110、190 mg/kg,共投喂56 d.试验结束时测定,军曹鱼成活率、质量增加率、红细胞含量、肌肉铁含量、骨骼铁、锌含量和肝脏铁、锌含量明显受饲料中铁、锌添加量的影响;血清碱性磷酸酶活性受铁、锌交互作用影响显著,饲料系数主要受铁锌交互作用的影响.以成活率和质量增加率为评价指标,军曹鱼幼鱼商品饲料中铁和锌适宜添加量分别为200 mg/kg和110 mg/kg.     

Pond Culture of Larval and Juvenile Cobia,Rachycentron canadum,in the Southeastern United States

Abstract

The potential of growing larval and juvenile cobia, Rach-ycentron canadum, in ponds was investigated. Larval cobia, obtained from tank spawning of wild-caught adults, were stocked 48-72-h post-hatch at a rate of 700,000/ha into three fertilized 0.25-ha ponds. At one week post-stocking (WPS), fish were observed consuming formulated feed. Growth was rapid, with specific growth rates (SGR) ranging from 12.5-19.2% body weight/day. At harvest (5 WPS) fish reared in two ponds weighed 7.9 and 9.3 g and total length (TL) was 118.9 and 129.3 mm, respectively (all fish reared in remaining pond died the night prior to harvest due to aerator failure). Feed conversion ratio (FCR) was 3.8 for both ponds and survival was 5.3 and 8.5%. Low survival rates were thought to be due primarily to cannibalism. Immediately after harvest, fish were restocked into two 0.25-ha ponds at a stocking rate of 14,400/ ha. Fish were fed formulated, pelleted feeds. Growth was rapid up to ～9 WPS, after which pond water temperatures declined. Ponds were harvested at 13 and 15 WPS, respectively. Final weight of fish was 309.9 and 362.5 g. Final TL was 343.1 and 355.7 mm. FCR was 3.8 and 4.5 and survival was 27.5 and 30.5%. Major losses of fish were associated with avian predators and possibly a toxic algal bloom. Results of trials indicate that cobia larvae and juveniles can be reared in pond-based culture systems, however additional research is needed to refine this approach.     

Relative contribution of alternative proteins to the growth of Juvenile Cobia,Rachycentron canadum (Linnaeus)

Five isonitrogenous and isocaloric diets were fed to juvenile cobia, to assess the relative contribution of different proteins (fish meal, soybean meal, corn gluten and beer yeast) to the growth of cobia. The dietary effects on nitrogen and carbon turnover and on the isotopic diet‐consumer discrimination factors (Δ¹⁵N and Δ¹³C) were also assessed. Growth results showed that the final body weight, growth rate, feed conversion ratio and protein efficiency ratio of cobia fed diets with alternative protein were significantly lower (P < 0.05) than cobia fed diet formulated with 100% fish meal. The estimated half‐lives of nitrogen and carbon ranged between 9–11 days and 6–8 days, respectively, with significant differences among treatments (P < 0.05). Δ¹⁵N ranged between 0.0–1.2‰ and ?0.1–1.6‰ in whole fish and muscle and Δ¹³C ranged between 3.8–5.1‰ and 4.0–5.1‰ in whole fish and muscle respectively. Diets were formulated with low levels of dietary nitrogen (10%) supplied by alternative protein sources substituting fish meal. The relative contributions of the dietary nitrogen supplied from these sources to the growth of whole fish and muscle tissue ranged between 4.9–5.2% and 5.9–7.7% respectively. Results indicated that growth accounted for the majority of observed isotopic change in animals under all treatments. In whole animals and muscle tissue, isotopic change due to metabolism occurred faster for carbon stable isotopes than for nitrogen stable isotopes. Cobia fed diets formulated with alternative proteins showed reduced nitrogen turnover rate and increased Δ¹⁵N.     

不同饲料对军曹鱼组织消化酶活力的影响

比较研究了投喂冰鲜鱼和人工配合饲料的军曹鱼胃、前肠以及肝脏消化酶(蛋白酶、胰蛋白酶、淀粉酶和脂肪酶)活力.试验结果表明,(1)蛋白酶活力:前肠与肝脏的蛋白酶比活力,投喂配合饲料组显著高于冰鲜鱼组(P<0.05),而胃中的蛋白酶比活力以冰鲜鱼组显著高于配合饲料组(P<0.05);(2)胰蛋白酶活力:胃中胰蛋白酶比活力,冰鲜鱼组显著高于配合饲料组(P<0.05),前肠与肝脏的胰蛋白酶比活力配合饲料显著高于冰鲜鱼组(P<0.05);(3)淀粉酶活力:胃中的淀粉酶比活力,冰鲜鱼组显著高于配合饲料组(P <0.05),前肠的淀粉酶比活力则是配合饲料组显著高于冰鲜鱼组(P<0.05),两种饲料对军曹鱼肝脏淀粉酶比活力影响不显著(P>0.05);(4)脂肪酶活力:胃及前肠的脂肪酶比活力两种饲料间差异不显著(P>0.05),但肝脏的脂肪酶比活力则以配合饲料组显著高于冰鲜鱼组(P<0.05).     

Ecological and economic analysis for cobia Rachycentron canadum commercial cage culture in Taiwan

The structure of cost and return for cobia cage culture in Taiwan was studied by considering two major factors, geographical location and production scale. Although the geographical location had little influence on the input intensities, the production scale would have a significant impact on the cost structure. However, the performances of profitability were significantly affected by not only the individual main effects but also their interaction. As a result, the studied effects on the cost and return were quantitatively estimated by a series of statistical models, in turn quantitatively measured by a set of indices. A short-term strategy of the management suggested that the best choice regarding profitability is to locate the farming system with a large-scale operation in the coastal waters of Pindong. Additionally, the profitability could be further increased by selecting better quality fingerlings and feeds based on a set of the computed indices. A long-term strategy of the management strongly recommends that to increase the system size in cobia production would be much more profitable due to the positive economies of scale. Finally, a future study shall be interested in whether current speed has a limiting effect on the profitability.     

Performance of Advanced Juvenile Cobia,Rachycentron canadum,Reared Under Different Thermal Regimes: Evidence for Compensatory Growth and a Method for Cold Banking

ABSTRACT

Two trials were undertaken to examine the growth response of juvenile cobia, Rachycentron canadum, at varying temperatures. The initial trial was conducted to determine the effect of various temperatures (18, 23, and 29°C) on weight gain and feed efficiency. The second trial investigated the effect of elevating water temperature in which fish maintained at 18°C and 23°C to a temperature close to their optimum (29°C). The latter study was undertaken in order to determine the effect of thermal shifts upon subsequent growth response of the species. Such information will assist commercial producers in developing various culture guidelines. As anticipated, differences (P < 0.01) in weight gain were recorded among all treatments, although remarkably, feed efficiency did not differ for cobia held at 23°C and 29°C. Following thermal shift, cobia subjected to the largest temperature change (18–29°C) illustrated an immediate growth response, but specific growth rates (SGR) did not exceed that of cobia held at 29°C for the duration of the trial. Nevertheless, when SGR were examined using fish of similar size (i.e., derived from different time points during the study) evidence for growth compensation was obtained. This study illustrates that cobia can be held at reduced temperatures, without detrimental impact on future performance, as a means of maintaining animals at smaller size for production and experimental purposes: “Cold banking.”     

Peptones in Silage from Tilapia (Oreochromis niloticus) and Cobia (Rachycentron canadum) Waste as a Culture Medium for Bioprocesses

This study investigated the efficacy of the aqueous fraction obtained after fractionating silage of tilapia (Oreochromis niloticus) and cobia (Rachycentron canadum) in supporting the growth of Escherichia coli and Staphylococcus aureus. The silages were prepared using combinations of citric, formic, and propionic acids. The aqueous fractions, used as test peptones, contained lower levels of total protein. The concentrations of 18 amino acids in all the samples were observed to be lower than those in the commercial peptone. Glutamic acid, lysine, glycine, and aspartic acid were present in higher concentrations than other amino acids, for both types of silage. Biomass production from E. coli culture ranged from 38.4 to 65.9 mg 100 mL^?1 for all the tested treatments, while that for S. aureus was from 26.3 to 53.7 mg 100 mL^?1. This indicated that products from fish silage were effective for bacterial growth in terms of biomass, by providing the main sources of nitrogen and carbon to facilitate their growth. The tested silages yielded similar efficiency to the commercial peptone. The findings revealed that it is feasible for the fish processing industry to incorporate freeze-dried by-products obtained after fractioning waste silage from the processing of tilapia and cobia.     

温度对细鳞鲑幼鱼最大代谢率和代谢范围的影响

为了探究温度对细鳞鲑(Brachymystax lenok)幼鱼的代谢特征和有氧运动能力的影响,在不同温度(4℃、8℃、12℃、16℃、20℃)下测定了实验鱼的静止代谢率(RMR)、有氧运动过程中的最大代谢率(MMR)以及能量代谢范围(MS)和临界游泳速度(UCrit)。结果表明,随着温度的上升,RMR和MMR均显著提高(P0.05),各温度下的RMR和MMR分别较4℃条件的提高了62%(8℃)、165%(12℃)、390%(16℃)、411%(20℃)和3%(8℃)、34%(12℃)、111%(16℃)、115%(20℃);MS随水温的升高呈现下降的趋势,且4℃条件具有最大的代谢范围。不同温度条件下UCrit存在显著性差异,但随着温度升高未表现出明显的变化规律。有氧运动过程中,不同流速下测定的MMR多出现在70%UCrit附近,可能是由于无氧代谢过早启动,使得机体乳酸积累过多进,降低了有氧代谢水平。     

鲢鳙幼鱼临界游泳速度的比较研究

通过比较不同鱼类的游泳能力,为鱼道建设和鱼类行为学研究提供基础资料。在(20±1)℃水温下,使用丹麦Loligo System公司的鱼类行为视频跟踪系统,采用Brett流速递增法,以鲢(Hypophthalmichthys molitrix)和鳙(Aristichthys nobilis)为研究对象,体长作为划分依据,分别测定不同体长组鲢鳙临界游泳速度。结果表明:(1)鲢鳙绝对临界游泳速度随着体长的增加而增大,相对临界游泳速度随着体长的增大而减小,鲢体长与绝对临界游泳速度拟合方程为:Y1=0.10X21-0.11X1+55.86(R2=0.85),与相对临界游泳速度拟合方程为:y1=0.02x21-0.87x1+12.86(R2=0.94),鳙体长与绝对临界游泳速度拟合方程为:Y2=0.03X32-1.29X22+21.04X2-29.21(R2=0.85),与相对临界游泳速度拟合方程为:y2=0.02x22-0.87x2+14.81(R2=0.98);(2)相近体长组鲢(10.11±0.24)cm和鳙(10.78±1.34)cm临界游泳速度分别为(65.50±2.08)cm/s和(80.89±4.03)cm/s,可知鳙鲢,且差异性显著(P0.05);(16.90±0.55)cm鲢和(15.39±0.62)cm鳙的临界游泳速度为(83.92±3.03)cm/s和(91.62±3.54)cm/s,无显著性差异(P0.05);(3)通过比较鲢鳙临界游泳速度与突进游泳速度能力,发现鲢的突进游泳速度大于鳙,而临界游泳速度小于后者,可知鲢鳙有氧运动和无氧运动能力之间存在权衡作用,临界游泳速度与突进游泳速度不一定呈现正相关关系。鱼类能否顺利完成上溯需求取决于鱼道内水力条件和自身游泳能力。     

Thermal Optima for the Culture of Juvenile Summer Flounder,Paralichthys dentatus

Abstract

Summer flounder, Paralichthys dentatus, aquaculture has shown promise over the recent past and a considerable body of knowledge is amassing for this species of flatfish. Even with the amassing data, basic information on environmental parameter ranges to maintain in indoor culture systems is still lacking. Therefore, the current study was undertaken to elucidate a temperature range that may be best suited for juvenile summer flounder production in indoor recirculating aquaculture. A 10-week study was designed to address 19, 24 and 29°C as potential temperatures for the culture of summer flounder. Fish averaging 9.5 g initial weight were stocked into triplicate 20-L aquaria per treatment after conditioning to their respective temperatures for 1 week. Fish were fed to apparent satiation twice daily a 50% crude protein fingerling diet and weighed every 2 weeks to assess growth rates.

Juvenile summer flounder grew better at 24 and 29°C (167 and 197% increase initial weight, respectively) than at 19°C (97% increase in initial weight) with increased individual fish variation within a treatment as temperature increased above 19°C. Feed efficiency was greatest at 24 and 29°C (0.65 and 0.57, respectively), but survival decreased at temperatures above 19°C (93, 60 and 57% for 19, 24 and 29°C, respectively). There was no effect of temperature on the hepatosomatic index or interior muscle ratio, but the finray muscle ratio was slightly elevated when flounder were cultured at 29°C. The lipid content of the finray muscle and liver also increased at 29°C. Therefore, 24°C appears to be the best culture temperature for summer flounder with respect to growth rates and efficiency, but survival and homogeneity of flounder may be lowered at temperatures above 19°C.     

Critical Thermal Maximum of Juvenile Spotted Seatrout (Cynoscion nebulosus) Reared for Summer Stocking in Texas

The critical thermal maximum of juvenile spotted seatrout (SL range 18–33 mm) was determined using a temperature increase of +0.26°C per hour. The critical thermal maximum (water temperature that was lethal to 50% of the test fish [LT₅₀]) for trial 1 was LT₅₀ = 38.8°C, LT₅₀ = 39.4°C for trial 2, and LT₅₀ = 38.9°C for trial 3. Critical thermal maximums differed significantly (P < 0.05) between trials 2 and 3, whereas trial 1 did not differ among trials. This difference correlated with body size, where fish in trial 2 were significantly larger (P < 0.05) (mean = 27.6 ± 2.0 mm in SL) (mean ± SE) than the fish of trials 1 (mean = 23.1 ± 0.5 mm in SL) and 3 (mean = 21.5 ± 0.7 mm in SL), suggesting positive size dependence in the critical thermal maximum.     

Temperature,plankton and conspecific density influence dynamics of age‐0 gizzard shad: implications for a gape‐limited piscivore

Age‐0 gizzard shad Dorosoma cepedianum are the main prey fish for white crappies Pomoxis annularis in many US reservoirs. However, these prey fish commonly outgrow their vulnerability to white crappie predation in some, but not all, northern Missouri reservoirs. Potential variables that could influence abundance, growth and mortality of age‐0 gizzard shad were examined in three reservoirs that differed with respect to age‐0 gizzard shad growth rates. Because of thermal effluent from a power plant, gizzard shad spawned earlier in Thomas Hill Lake and initial densities of larvae were greater than in the other reservoirs. Larval and juvenile gizzard shad grew slowest in Thomas Hill Lake, followed by Mark Twain Lake and Long Branch Lake. Growth rate of larvae increased with increasing water temperature and food abundance, but decreased with increasing conspecific density. Similar relationships were found for juvenile growth, except that growth declined with increasing temperature. The slower growth of larvae and juveniles in Thomas Hill Lake was probably a consequence of their greater densities relative to their food abundance and higher water temperatures during the juvenile stage. Conversely, both larvae and juvenile gizzard shad grew more rapidly and juveniles attained large sizes in Long Branch Lake owing to their lower densities relative to their available food. Mortality of larvae and juveniles was mostly similar among the reservoirs. Because of their greater abundance and slower growth, gizzard shad were available as prey for white crappies for a longer period in Thomas Hill Lake than in the other reservoirs.