Growth response of Nile tilapia fry to salinity stress in the presence of an 'internal reference' fish

Growth of three strains of Oreochromis niloticus L. fry exposed to salinity stress in the presence of an internal reference fish were compared. The Central Luzon State University (CLSU) strain was obtained from the Freshwater Aquaculture Center, CLSU, Philippines. The ISRAEL strain was acquired from the Philippine government's Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR‐NFFTC), Munoz, Nueva Ecija. The National Inland Fisheries Institute (NIFI) strain was obtained from the NIFI, Bangkok, Thailand. Eight to nine full‐sib families (replicates) per strain were split into two groups. One group was grown in freshwater for 2 weeks, acclimated to 32 ppt and reared for 2 weeks and finally grown in freshwater for another 2 weeks. Another group was contemporaneously grown in freshwater polyethylene tanks for 6 weeks. Each replicate family included a size‐matched internal reference population of red tilapia strain. Two‐way analysis of variance (anova ) revealed no significant strain differences (P=0.081; r²=0.106). However, analysis of covariance with the internal reference strain used as a covariate showed significant (P=0.049; r²=0.638) strain effects on specific growth (based on standard length measurements). The ISRAEL strain showed consistently better growth rate in both saline and freshwater environments than the NIFI and CLSU strains. We estimated the statistical power of the two‐way anova (?=√(k′?1)(factor MS?s²)/(k′s²); Zar 1984) to be ～0.30. There was a 70% probability of a Type II error and no true difference in the growth of the three strains was detected. The use of internal reference strain as a covariate improved the r² from 0.106 to 0.638 and increased the efficiency of the test in detecting a true difference. Other strain comparison studies in our laboratory at the Southeast Asian Fisheries Development Center Aquaculture Department showed that the ISRAEL strain shows better growth than the NIFI and CLSU strains in a crowding stress tolerance experiment, when fed only with rice bran and under restrictive feeding regimes.     

An attempt to determine the survival time for starving fish larvae

Studies were carried out on the respiratory rate of starving and fed whitefish larvae in light and darkness. Using the average respiratory rate and chemical composition of the body, the theoretical survival time for starving whitefish larvae was calculated for a given temperature during the period from hatching to 50% mortality. Applying Q₁₀ coefficients, average survival times were also calculated for starving larvae in different water temperatures.     

The effect of photoperiod on the reproductive performance of the Nile tilapia, Oreochromis niloticus

The reproductive performance of O. niloticus was evaluated in four different photoperiods. Results suggested that long days were the most suitable for egg production and reduction of inter-spawning interval.     

Dietary taurine improves reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock

This study was conducted to evaluate the effects of supplemental taurine on reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock fed soybean meal‐based diets. Four isonitrogenous (350 g kg^?1 protein), isocaloric (18 MJ kg^?1) diets were formulated to contain 0, 5, 10 and 15 g kg^?1 taurine. The diets were fed to triplicate groups of juvenile Nile tilapia (10–15 g average body weight) at a female: male ratio of 3 : 1, to apparent satiation, three times per day for 130 days. The size at first maturation decreased with increasing dietary taurine to 10 g kg^?1 and levelled off with further taurine supplementation. The time to first spawning was also significantly shorter at 10 g kg^?1 taurine level. Spawning performances, including spawning frequencies, total number of spawnings per tank, number of spawnings per female and absolute fecundity, were all significantly improved with increasing dietary taurine up to 10 g kg^?1. However, the quadratic regression analyses indicated that the maximum spawning performance occurred at 8 g kg^?1 of supplemental taurine. Eggs produced from broodstock fed 10 g kg^?1 taurine exhibited significantly higher hatchability and required shorter time for hatching and yolk‐sac absorption and also resulted in higher larval weight than at other dietary taurine levels. The highest egg protein, total amino acids and taurine were also obtained at 10 g kg^?1 taurine. These results suggest that 8 g kg^?1 dietary taurine is required for optimum reproductive outputs of Nile tilapia broodstock.     

Generation of mouse monoclonal antibodies specific to tilapia immunoglobulin using fish immunoglobulin/BSA complex for monitoring of the immune response in Nile tilapia Oreochromis niloticus

The simple immunoprecipitation method was used to isolate tilapia immunoglobulin (Ig) for immunization in order to produce monoclonal antibodies (MAbs) specific to tilapia Ig. First, the tilapia antiserum against bovine serum albumin (BSA) was prepared by peritoneal injection of BSA into tilapia, and the tilapia anti‐BSA antiserum was used to precipitate BSA to form the Ig/BSA immune complex. The Ig/BSA immune complex was then injected into Swiss mice for hybridoma production. After fusion, three hybridoma clones producing MAbs specific to the tilapia antibody were selected by dot blot and Western blot. All MAbs (101A, 59G, and 11A) were bound specifically to the heavy chain of immunoglobulin M (IgM). The MAbs 101A and 59G demonstrated twofold higher affinity than MAb 11A and the commercialized antibody. However, MAbs 11A could also bind to the heavy chain of IgM in Asian seabass, Lates calcarifer, as well. These MAbs can be used to monitor the immune responses of individual fish by indirect ELISA upon exposure to various antigens.     

A simulation application to improve the operational efficiency of the wholesale fish market in Taiwan

Abstract

This paper presents the applications of two simulation models developed for the Pu‐Shin wholesale fish market: the current operational model and the alternative operational model. This study analyses the possible influence on the wholesale fish system by manipulating the number of porters in the alternative operational model. Cost‐benefit analysis is conducted to compare the two models. The results suggest ways to improve the operational efficiency of the wholesale fish market in Taiwan.     

Effect of dietary protein level on the reproductive performance of Nile tilapia, Oreochromis niloticus (L.)

The effects of five dietary protein levels (25%, 30%, 35%, 40% and 45%) on the individual spawning frequency and the egg production of 135 tagged female Nile tilapia, Oreochromis niloticus (L.), were studied from 8 May to 19 November 1996 in outdoor concrete tanks. Virtually identical spawning patterns were found in all treatments, but there was a great deal of variation in the frequency of spawning and egg production. Overall, individual spawning frequency varied from one to 14 and individual egg production from 31 to 2828 eggs per spawning. The average number of spawnings and average number of eggs per spawning for fish receiving dietary protein levels of 25%, 30%, 35%, 40% and 45% were 8.0 ±1.6, 8.4 ± 2.2, 8.5 ± 2.7, 8.4 ± 2.5 and 9.4 ± 2.1 spawnings, and 1167 ± 305, 1082 ± 410, 1288 ± 324, 1145 ± 389 and 1328 ± 311 eggs per spawning, respectively. Fish receiving 45% dietary protein spawned more frequently than fish receiving 25% dietary protein. The total number of eggs produced per female was significantly higher for females fed 45% protein feed than females receiving 25% and 30% protein feeds. No definite trend was found in the number of eggs produced per spawning and the number of eggs produced per gram in females fed at different protein levels. Based on weekly checking, the time interval between spawnings varied from 7 to 77 days, and mean spawning intervals ranged from 15.8 to 17.1 days. Sixty per cent of females spawned after an interval 14 days, 15% after 21 days, 13.6% after 7 days, 7.2% after 28 days, 1.8% after 35 days and 1.0% after 42 days, and the time interval was 49-77 days for the rest of the females (1.5%). In all treatments, maximum spawning activity was recorded from May to August, and thereafter, it gradually decreased and no spawning females were found in November.     

Evaluation of replacing fish meal with corn protein concentrate in Nile tilapia Oreochromis niloticus fingerlings commercial diet

Four isocaloric‐isonitrogenous diets containing 0, 50, 100 and 190 g/kg corn protein concentrate (CPC) as replacement for dietary fish meal were fed to Nile tilapia Oreochromis niloticus fingerlings for 8 weeks. Tilapia growth parameters were not significantly (p > .05) different in fish fed diets with 0, 50 and 100 g/kg CPC and found to be superior compared to those fed on 190 g/kg CPC. Fish dressing ratios and body composition were similar among all treatments. The electron microscope indicated that the stomach size of control fish was slightly smaller and the wall was thinner while the stomach of the fish fed all other levels of CPC undergone a remarkable size increase and their walls were thicker after feeding diets with CPC. Total aerobic bacterial and coliform counts were significantly decreased in fish intestine when fed diets with 100 and 190 g/kg CPC compared with fish fed diets with 0 g/kg or 50 g/kg CPC. This study indicates that it is possible to replace up to 534 g/kg of dietary fish meal in tilapia fingerlings using 100 g/kg of CPC without any negative effect on fish growth and proximate body composition.     

The eyes of the common carp and Nile tilapia are sensitive to near-infrared

Fish biologists have shown little interest in near-infrared (NIR) sensitivity because water absorbs light in the red and near-infrared and because downward irradiance in clear ocean water is mostly blue light. In recent years, however, Nile tilapia Oreochromis niloticus was shown to be NIR sensitive by behavioral techniques. This study confirmed NIR sensitivity in the common carp Cyprinus carpio and Nile tilapia by using a more sensitive technique than a behavioral one. Cardiac conditioning experiments showed that both fishes are sensitive to 865 nm NIR. The conditioned response to 865 nm NIR was observed in Nile tilapia when the eyes were not covered and the pineal window was covered, but not when the same fish had its eyes covered and the pineal window exposed to the NIR. The eyes are thus, the NIR-sensitive organs in Nile tilapia. To identify the NIR photoreceptor, the retina was examined by histology. The retina exposed to 865 nm NIR showed incomplete dark adaptation with rods exposed from retinal epithelial pigment. Though the reaction to NIR seemed to be mediated mainly by the red cone, the involvement of the rod could not be ruled out.     

遗传全雄尼罗罗非鱼与吉富罗非鱼养殖性能比较

以超雄鱼为父本进行遗传全雄鱼的繁育是获得全雄罗非鱼苗种的方法之一.为了评估全雄尼罗罗非鱼的养殖性能,进行了遗传全雄尼罗罗非鱼与吉富罗非鱼的池塘及网箱养殖比较试验.结果显示,初始体长3～5 cm的遗传全雄尼罗罗非鱼和吉富罗非鱼鱼苗经过100 d池塘养殖后,平均体质量分别达到558.00 g和501.80 g,遗传全雄群体...     

青鱼原种繁殖技术与实践

青鱼因其生长快、个体大、疾病少、肉质鲜嫩、经济价值高而深受养殖者和消费者的青睐。近年来,随着渔业养殖品种结构的调整,青鱼养殖面积有所扩大,其苗种需求逐年增加。但青鱼繁殖与鲢、鳙、草鱼比较,技术难度较大,要求较高。笔者结合武汉市滠口渔场自1991年建立青鱼原种场以来的生产实践,探索了青鱼苗种繁殖技术,特撰此文,旨在为青鱼原种繁殖和生产发展提供参考。1　原种的引进、培育与选择1.1　原种引进家鱼经过近40年的人工繁殖,由于近亲繁殖等原因,其个体趋小、性成熟提前、生长速度下降、抗病力降低,商品生产性能远不如其原产地长江等…     

Dietary supplementation of Tribulus terrestris extract improves growth and reproductive performances of the male Nile tilapia (Oreochromis niloticus)

Effects of dietary supplementation of Tribulus terrestris (TT) and 17α‐methyl testosterone (MT) on growth performance and reproductive efficiency of male Nile tilapia, Oreochromis niloticus (N = 75, initial weight 60 ± 3.251 g), were evaluated. Five experimental treatments in triplicate were fed on basal diet (30% crude protein) (control group, CG), basal diet containing 60 mg MT (MT group) and basal diet containing 250, 500 and 750 mg/kg diet TT (TT250, TT500 and TT750 groups), respectively, for consecutive 45 days. Results revealed that the fish received TT in diet showed better growth performance (final body weight, weight gain, feed conversion ratio, specific growth rate, testes weight and gonadosomatic index) compared with MT and CG (p < .05), as well as for haemoglobin content and red blood cell count (p < .05). The highest level of testosterone, 11‐keto testosterone, sperm concentration and vitality was recorded in TT750 followed by TT500, TT250 and MT groups, while the lowest value was recorded in the CG (p < .05). The highest seminiferous tubule diameter was recorded in TT750 followed by TT500, TT250 and CG, while the lowest diameter was recorded in the MT group (p < .05). Fish received TT showed normal dilated seminiferous tubule filled with large amount of free sperms within their lumen in a dose related effect. In conclusion, male Nile tilapia dietary supplementation with different inclusions of Tribulus terrestris extract specially 500 and 750 mg/kg diet improves growth performance, health condition, semen quality and reproductive efficiency without any harmful effect on water quality.     

引进漠斑牙鲆亲鱼国内转运技术

近年来,国内已有6-7个单位 从美国引进了漠斑牙鲆 (Paralichthys lethostigma)亲鱼、 鱼苗进行培育,有的单位已取得较 大的进展,但亲鱼培育与产卵技术 还存在一些问题,没有形成规模化 苗种生产的能力。目前,国内很多 科研企业正致力于引进漠斑牙鲆亲鱼 来进行苗种生产,而漠斑牙鲆亲鱼 的长途运输技术已比较完善,在国 内机场交货时的成活率基本能够达到 100％,但是有些企业在国内转运过 程中,由于经验不足造成亲鱼部分 死亡,有些情况下死亡率高达 40％,损失巨大。笔者总结了自身 在漠斑牙鲆亲鱼国内转运实践中的一 些做法,希望对养殖企业能够有所 借鉴和帮助。     

An appraisal of factors constraining the success of fish stock enhancement programmes

Stocking and introduction of fish have been widely applied in Yunnan Province, China, for many years to mitigate for declines in natural stocks and commercial catches, and to restore or create new fisheries. The present paper assesses the results of activities concerned with stock enhancement programmes to evaluate the factors which have contributed towards the success of these projects. Factors such as natural lake conditions, stocking density, the age and size of fish stocked, and the mechanisms of stocking are discussed. Stocking density was evaluated using the equations Y _p = [ B ( P / B ) U _f]/ K _f or PY_p = (P × U_f)/K_f, which were based on the ecological carrying capacity of the recipient lake and other criteria. The stocking density in most lakes in Yunnan was high, but the recapture rates and total yield did not reach the predicted levels. This may have been an effect of the size of the fingerlings released (finger-lings >10 cm have a greater chance of survival). Key management measures for stocking and the ecological impacts of overstocking grass carp, Ctenopharyngodon idella (Valenciennes), are also described.     

Characterization and comparison of variations in reproductive performance of Chitralada strain Nile tilapia, Oreochromis niloticus (L.)

In an attempt to better understand and characterize the variability in the female reproduction of individual Thai‐Chitralada strains of Nile tilapia, Oreochromis niloticus (L.), tagged mature females (n=68) from a single population were monitored in a hapa‐in‐pond system over a 12‐month experimental period. Spawn female⁻¹, eggs female⁻¹ day⁻¹, eggs kg female⁻¹ day⁻¹, day spawn⁻¹ and weight (g) at first spawning of individual females were determined from the regular weekly sampling of weight (g) and eggs per spawn. For analysis, the females were grouped into two, high spawning (HSF) and low spawning frequency (LSF) classes based on their spawning frequency (SF) record. Moreover, nested under these two classes were two groups each based on growth rate, i.e., high frequency – large size (HL), high frequency – small size (HS), low frequency – large size (LL) and low frequency – small size (LS). There was no difference in eggs spawn⁻¹ among all females. The HSF group produced 68% and 361% more eggs female⁻¹ day⁻¹ than the population mean and LSF group respectively. Eggs female⁻¹ day⁻¹ and spawn female⁻¹ remained high in the HSF group and low in the LSF group throughout the 12‐month experimental period. This suggests that individual female spawning activity is consistent within a population in a common environment. The inter‐spawn interval increased with age in all four groups, and day spawn⁻¹ was shorter by 130% in HSF females compared with day spawn⁻¹ in LSF. The HSF group also spawned more successively (≥3), while the LSF group of females had fewer successive spawns (≤2). Body weight (g) had no influence on the number of eggs produced. The study indicates that separating frequently spawning females could be used as an important strategy to improve commercial seed production of Nile tilapia.     

Mianserin affects alarm reaction to conspecific chemical alarm cues in Nile tilapia

In this study, I show that mianserin, a chemical with serotonin and adrenoceptor antagonist activities, increases fish vulnerability to a potential predator threat, when prey fish must deal with this threat based on conspecific chemical alarm cues. For that, I evaluated whether mianserin, diluted in the water, influences the behavioral responses of Nile tilapia (Oreochromis niloticus) to conspecific skin extract (chemical alarm cues). I found that, while mianserin did not abolished antipredator responses, this drug mitigates some components of this defensive reaction. Thus, a potential decrease in serotonin and adrenergic activities reduces the ability of dealing with predators when perceiving conspecific chemical alarm cues.     

Production of heterozygous and homozygous clones in Nile tilapia

Production of heterozygous and homozygous clones of Nile tilapia (Oreochromis niloticus L.) was successfully carried out. An outbred clonal line was produced by cross-breeding between a viable mitotic gynogenetic female and male (recessive mutation in a sex determining gene). At the same time, an inbred clonal line was produced by gynogenetic reproduction (retention of 2nd polar body) using optimal pressure/heat shock treatments. The heterozygous and homozygous nature of the two types of clonal lines were checked and identified at the adenosine deaminase ADA* marker locus. A model for the large scale production of similar clones is presented. The possible implications of such clonal lines in genetic research and in the culture of Oreochromis spp. are discussed. © Rapid Science Ltd. 1998     

Evaluation of Nile tilapia pond management strategies in Egypt

Five pond management strategies for Nile tilapia Oreochromis niloticus L. production were evaluated in 0.1‐ha earthen ponds in Egypt during a 145‐day production cycle. Pond management strategies developed by the Pond Dynamics/Aquaculture Collaborative Research Support Programme (PD/A CRSP) were compared with a traditional and a modified Egyptian pond management strategy. Young‐of‐year Nile (mixed‐sex or sex‐reversed) tilapia were stocked into ponds at 20 000 fish ha^?1. Sex‐reversed tilapia were stocked into chemical fertilization, organic fertilization plus formulated feed and feed only treatment ponds, whereas mixed‐sex tilapia were stocked into organic fertilization plus formulated feed and chemical plus organic fertilization plus formulated feed treatment ponds. Nile tilapia yields ranged from 1274 to 2929 kg ha^?1. Nile tilapia yields in organic fertilization plus formulated feed treatments were significantly greater than the yield from chemical fertilization ponds. PD/A CRSP pond management strategies did not produce significantly greater Nile tilapia yields than the traditional Egyptian system, but a larger percentage of harvested tilapia in the organic fertilization plus feed treatments were classified in the first and second class size categories compared with the traditional Egyptian system. Organic fertilization plus formulated feed pond management strategies had the highest net returns, average rate of return on capital and the highest margin between average price and break‐even prices to cover total variable costs or total costs.     

Total replacement of fish meal with animal protein sources in Nile tilapia,Oreochromis niloticus (L.), feeds

The effects of total replacement of dietary fish meal (FM) with animal protein sources on the growth, feed efficiency and profit indices of Nile tilapia, Oreochromis niloticus (L.), were investigated. Shrimp meal (SM), blood meal (BM), meat and bone meal (MBM), BM + MBM mix and poultry by-product meal (PBM) replaced FM in six isonitrogenous (30% crude protein), isocaloric (400 kcal GE 100 g^–1) diets. The diets were fed to O. niloticus fingerlings (12.5 g) to satiation twice a day for 150 days. The growth of fish fed SM, PBM and MBM was not significantly different from those fed the FM-based diet, while feed conversion and protein efficiency ratios were significantly retarded. Further reduction in fish performance was noticed when BM or BM + MBM replaced FM in the control diet. Cost–benefit analyses of the test diets indicated that these sources were economically superior to FM. The PBM-based diet produced higher carcass lipid than other diets. Fish fed SM, MBM and PBM diets had significantly higher ash contents (P < 0.05).