Dietary potassium requirement of fingerling Indian major carp,Labeo rohita (Hamilton), based on growth parameters,gill Na+‐K+ ATPase activity,tissue mineralization and antioxidant activities

To quantify the dietary potassium requirement of fingerling Labeo rohita (6.2 ± 0.12 cm; 1.98 ± 0.06 g), seven purified experimental diets (350 g/kg crude protein and 16.72 kJ/g gross energy) with graded levels of potassium (0.32, 1.35, 2.41, 3.46, 6.48, 9.47 and 12.39 g/kg diet) were fed to triplicate groups of fishes at 08:00, 12:00 and 16:00 hr to apparent satiation for 8 weeks. Live weight gain (LWG; 671.46%), specific growth rate (3.65%/day), protein efficiency ratio (2.16), protein gain (PG; 2.41 g/fish) and feed conversion ratio (1.32) were found to be best in fish fed diet containing 3.46 g/kg potassium. Gill Na⁺‐K⁺ ATPase activity was also highest in fish fed diet with 3.46 g/kg potassium. Potassium content of whole‐body, vertebrae and scales increased significantly with the increase in dietary potassium level up to 6.48 g/kg. Significant changes were also noted in serum malondialdehyde content, superoxide dismutase, catalase, glutathione peroxidase and alkaline phosphatase activity. Based on the maximum live weight and protein gain observed in the present study, the inclusion of 3.55 g/kg potassium is recommended for developing potassium‐balanced commercial feeds for intensive culture of fingerling L. rohita.     

Improving rearing performance in sea‐cage culture of Pacific bluefin tuna Thunnus orientalis juveniles (Temminck and Schlegel) using small sea cages

High levels of mortality occur in large net‐cage culture of Pacific bluefin tuna (PBF) Thunnus orientalis due to poor growth on commencement of sea‐cage culture obstructing the mass production of fingerlings. Therefore, we carried out this study to develop a countermeasure by using small sea cages (square with 13‐m sides). PBF juveniles were directly transferred to a 30‐m‐diameter cage (control) and compared them to fish transferred to small sea cages for 12 days before being merged into another 30‐m‐diameter cage. The survival rate, growth performance and potential factors increasing mortality were examined. The results of our study showed that survival rate in small sea cages was approximately 20% higher than that of the control. Poor growth also occurred in the small sea cages; however, its frequency and daily mortality rate were half those in the control. In addition, growth performance such as specific growth rate and weight gain of PBF juveniles in small sea cages significantly increased compared to the control. These results suggest that using small sea cages could be an effective countermeasure for poor growth, which may mitigate the high‐mortality conditions of current sea‐cage culture systems for PBF.     

黄鳝的胚胎发育及鱼苗培育

黄鳝胚胎发育的时间较长,在水温２６℃左右时从受精卵到孵出需要１４２ｈ。并且胚胎发育速度及孵化率与水温密切相关,在水温２４．５￣２８．５℃范围内,随温度升高,胚胎发育速度增加。在黄鳝胚胎发育过程中,可见胸鳍形成并不断扇动,说明黄鳝祖先是有鳍条的。进行鳝苗培育,投喂食物以动物活饵料比较适宜,水丝蚓效果最好,浮游动物在培育前期也较适宜。而植物性饵料如米糠、麸皮不适宜用于培育鳝苗。     

池塘主养草鱼种高产试验

在３００５ｍ＾２的池塘里,高密度培养大规格草鱼种,且塔养鲢,鳙,鲤种。采取的技术措施是：草鱼种入池先喂芜萍,２０天后改喂浮萍并驯喂粗蛋白含量较高的小颗粒配饵。草鱼种长到１０ｃｍ后,改喂粗蛋白含量较低的配饵;定期注入新水,增氧,泼洒药物,投喂药饵,高温季节,使池水保持长流水。结果：共产草鱼种５０３２ｋｇ,平均规格８０．１ｇ;鲢鳙鱼种２６６０．６ｋｇ,鲤种５３６．３ｋｇ,纯利４８９２８．６元,投入产出     

奥尼罗非鱼养殖池沉积形成及其主要影响因子的初步研究

在半封闭式奥尼罗非鱼养殖池中投入饲料,探索养殖过程中鱼池沉积形成及其主要影响因子。试验结果表明:无论养鱼或未养鱼,投饲或不投饲,各池均发生不同程度的沉积;外源饲料输入量相同时,养鱼池新颗粒物生成量(干重)比未养鱼池大15.63%,而沉积量比未养鱼池小19.49%;无外源饲料输入时,养鱼池的沉积量比未养鱼池大75.76%;养殖系统内养殖对象与其所处环境的相互依存和相互制约对系统新颗粒物生成及沉积具有重要作用。     

匙吻鲟苗种规模化培育技术

2010年4月14日至6月1日在湖北宜昌进行了匙吻鲟苗种的规模化培育试验示范。鱼苗培育在室内水槽内进行,放养密度800～1000尾/m2,改善水温、溶氧、流速等养殖条件,适时投喂适口饵料生物,经过15d养殖,获4cm左右的鱼种47.12万尾,成活率95%;鱼种培育在水库坝下池塘进行,放养密度30万～40万尾/hm2,以...     

Growth performance of pengba,Osteobrama belangeri (Valenciennes, 1844) and water quality changes during fingerling rearing with varied stocking density in large outdoor concrete tanks

Fingerling rearing of pengba, Osteobrama belangeri, was conducted at varied densities for 90 days in 12 outdoor concrete tanks (10 m × 5 m × 1 m). The tanks, grouped into four triplicated treatments, were stocked with fry at 20, 30, 40 and 50 fry m^‐3; and designated as control, T‐1, T‐2 and T‐3 respectively. Tanks were filled up to 90 cm depth. Evaporation loss compensated fortnightly. Fish sampling and monitoring of water quality parameters done at fortnight intervals. Survival varied between 71.5% and 84.0% in treatments. Both survival and total length significantly reduced with increasing densities from control to T‐2 (p < .05), while no differences were observed between T‐2 and T‐3 (p > .05). Similarly, significant reductions in final body weight and specific growth rate were observed with increased densities and these values further reduced in T‐3 than T‐2 (p < .05). Such results corroborated the inverse relationship between stocking density and growth. Gross biomass yields in two higher densities (T‐2 and T‐3), despite their lower survivals, were significantly higher than the two lower densities. The numbers of fingerlings harvested were 35, 74 and 112% higher than the control in T‐1, T‐2 and T‐3 respectively. The lowest size obtained even at the highest density (T‐3) was of 7.0 ± 1.0 cm and 3.99 ± 0.17 g, which can be considered as ideal grow‐out stocking size of pengba. Therefore, the study showed feasibility of stocking up to 50 fry m^‐3 for rearing from fry to fingerling stage. However, the other lower densities may be used in case of requirement of larger fingerlings.     

Haemato-biochemical responses and induction of HSP70 to dietary phosphorus in <Emphasis Type="Italic">Catla catla</Emphasis> (Hamilton) fingerlings

A feeding trial of 120 days was conducted to study the effect of graded levels of dietary phosphorus on haematology, serum protein concentrations and HSP70 expression in fingerlings of the Indian major carp, Catla (Catla catla). Eight isonitrogenous and isoenergetic purified diets were formulated to contain graded levels of dietary phosphorus (dP), i.e., T₁, 0.1%; T₂, 0.3%; T₃, 0.5%; T₄, 0.7%; T₅, 0.9%; T₆, 1.1%; T₇, 1.3%; or T₈, 1.5%. Four hundred and eighty fish (average weight 4.23 ± 0.016 g) were equally distributed into 24 tanks forming eight treatments with three replicates each. The fish were fed daily at the rate of 3.5% body weight in two instalments. At the end of feeding trial fish were sampled to study total RBC and WBC count, haemoglobin, serum lysozyme activity, serum total protein, albumin (A), globulin (G) concentration and HSP70 expression. Total RBC count, haemoglobin concentration and serum lysozyme activity did not vary significantly in response to different dietary phosphorus concentrations. Total WBC count was found to be significantly (P < 0.05) higher in T₁ relative to all other treatments. Serum albumin and A/G ratio was found to be significantly lower in fish of T₁ and T₂ in relation to T₇ group (P < 0.05). Serum globulin and total protein levels remained unaffected by variations in dietary phosphorus. HSP70 expression was observed in T₁ group (0.1% dP) in gills and brain tissue, but not in liver and muscle tissues. No HSP70 expression was observed in fish of T₄ (0.7% dP) and T₈ (1.5% dP) treatments. These prima facie results suggest that dietary phosphorus had only minor influence on the haemato-biochemical parameters studied; however dietary phosphorus deficiency caused organ specific induction of HSP70 in catla fingerlings.     

On‐farm evaluation of formulated feeds on the breeding performance of Catla catla reared in rural ponds

Female Catla catla brood fish were reared in 12 ponds (0.03–0.05 ha) and fed daily once in the morning at 30 g kg^?1 body weight for 150 days with formulated feeds (six treatment feeds each with two replicates of pond) to study the breeding performances. The feed ingredients were rice polish (RP) and groundnut oil cake (GNOC) (1 : 1) for T1 (control); RP, GNOC and fish meal (FM) (3 : 4 : 3) for T2; RP, GNOC, FM and soybean meal (SM) (3 : 4 : 2 : 1) for T3; RP, GNOC, FM and SM (3 : 4 : 1: 2) for T4; RP, GNOC, FM and SM (3 : 4 : 1 : 2) with added vitamin–mineral (VM) premix for T5; RP, GNOC, FM and SM (3 : 4 : 1 : 2) with added VM and vegetable oil for T6. Results indicated that except the feed T6, all other feed (T2–T5) with 338–344 g crude protein (CP) kg^?1 feed enhanced the breeding performances of the fish compared with control (262 g CP kg^?1). The feed T3 showed the best performances in terms of matured female (%), fully bred female (%), relative fecundity, spawn production and profit. This suggests that a combination of RP, GNOC, FM and SM at definite proportion could supply the essential nutrients needed for higher breeding response.     

Labeo rohita and Argulus siamensis infection: Host size,local inflammatory reaction and immunity modulate ectoparasite load on fish

Parasite species often show a heterogeneous, highly dispersed pattern of infestation within hosts. Varieties of factors including morphological, physiological, immunological and nutritional characteristics affect the infestation level of a specific parasite in homogenous pray. Limited attempts, however, have been made to explore such underlying drivers of infestation pattern. Here, three stages of Labeo rohita (fingerling, juvenile and pre‐adult) were challenged with ectoparasite, Argulus siamensis in same aquaria. The parasite load on individuals was determined at 5‐day interval for 1 month. The load was found to be highest in pre‐adult stage followed by juveniles and fingerlings. On day 20 post infection, the load of parasite on pre‐adult fish was high along with detectable skin damages. Skin tissues were collected for immune gene expression analysis and histopathology. Histological studies showed increased melanization in the dermis and mild inflammatory cellular reactions in pre‐adult fish whereas, massive subcutaneous myositis with engorged blood vessels were observed in fingerlings. The expression levels of various inflammation and innate immune‐related genes viz., interleukin (IL)‐8, IL‐10, IL‐11, IL‐15, natural killer enhancing factor, toll‐like receptor 4, apolipoprotein A–I and immunoglobulin Z were significantly high in skin samples of infected fingerlings as compared to other two growth stages or controls of each stage. On the other hand, the expression of immunoglobulin M was down‐regulated in all infected samples as compared to their respective controls. The results thus depict that local immuno‐inflammatory response plays a significant role in determining susceptibility of host in intra‐specific group, and has important implications for ecology and aquaculture.