Effects of dietary cottonseed meal protein level on growth, gonad development and plasma sex steroid hormones of tropical fish tilapia Oreochromis sp

Five experimental diets containing increasing proportions of cottonseedmeal (CSM) protein (0, 25, 50, 75 and 100%; diets 1 to 5, respectively) toreplace fish meal (FM) protein were formulated for intensive culture of tilapiaOreochromis sp. Each diet was fed to three replicategroupsof fish (mean weight ± SE = 11.3 ± 3.9 g) in30L aquaria connected as a closed recirculating-water system andmaintained at 27 ± 1 °C. Fish were fed three times adayby hand at a rate of 3% of body weight during four weeks, after which thefeeding rate was gradually decreased to reach 1.5% at 16 weeks. Thesubstitutionof 75 and 100% of FM proteins by CSM proteins resulted in significantly lowerbody weights in both sexes. In both sexes, gonadosomatic indexes and plasmaconcentrations of sex steroids (testosterone, 11-ketotestoterone,estradiol-17 and 17,20-dihydroxy-4-pregnen-3-one) were notsignificantly different among dietary treatments. The concentration ofgossypol,an antifertility agent contained in CSM, was measured in reproductive tissues.The total gossypol concentration in the testis was consistently lower than thatmeasured in the ovaries of the same group. Moreover, in both sexes, theconcentration of the (+)isomer of gossypol was always higher than that of(–)isomer. The total gossypol concentrations in testes increasedsignificantly with the increase of CSM in the diet. The highest levels of the(+)isomer (7.64 ± 0.62 g g^–1)were found in the testes of fish fed diet 4, whereas the (–)isomerreached its highest values in the testes of fish fed diet 5. The highest levelsof both enantiomers of gossypol were found in the ovaries of fish fed diet 4(14.2 ± 2.7 and 5.6 ± 1.5 g g^–1for (+) and (–)isomers, respectively). In both sexes, thehistological analysis of the gonads did not reveal differences among the fishfed different levels of CSM. Although CSM at any levels did not affect thereproductive parameters examined in this study, it cannot be used to substitutemore than 50% of FM since at higher levels growth of tilapia was compromised.     

Culture of Macrobrachium rosenbergii (De Man 1879) in experimental cages in a freshwater eutrophic lake at different stocking densities

Macrobrachium rosenbergii (de Man 1879) juveniles (0.4 g) were cultured in experimental cages (L × W × H: 2.5 × 1 × 1 m) in Laguna de Bay, the largest lake in the Philippines. The following stocking densities at four replicates each were used: 15, 30, 60 and 90 prawns m⁻² of cage bottom. The mean sizes at harvest after 5 months of culture ranged from 14.3 g for the highest stocking density to 26.3 g for the lowest. The mean size at harvest, daily growth rate and size class distribution were significantly influenced by stocking density, with those at the lowest stocking density showing significantly better growth and overall proportion of larger prawns. Heterogeneous individual growth (HIG) was fairly evident in all treatments. The percentage of blue‐clawed males was not influenced by treatment but the mean weight was significantly higher in the lower stocking densities. Both the percentage and mean weight of berried females were significantly higher in the lowest stocking density. Survival was the highest in the lower stocking densities (55.3%, 54.0%, 52.7% and 36.9% for 15, 30, 60 and 90 prawns m⁻² respectively). Feed conversion ratio (FCR) improved with decreasing stocking density, ranging from 2.1 to 3. As expected, yield per cropping increased with stocking density and ranged from 450 to 1089 g m⁻² yr⁻¹ of actual cage area. Production values obtained in the cage cultured M. rosenbergii were comparable to or even higher than those reported from pond culture, given that the stocking densities used in this study were generally higher than in ponds. The results show that the farming of M. rosenbergii in cages in lakes is a viable alternative to pond culture and has the potential of improve aquaculture production in lakeshore fish farming communities.     

Accuracy of a machine-vision pellet detection system

Video cameras are employed on net pen fish farms for monitoring food pellet levels near the cage bottom. Herein, the accuracy of a new machine-vision system for the identification of a feed-wastage event and its response time are reported. Research involved novel tests and definitions, video footage recorded under different stocking and environmental conditions, and numerical filters to reduce the effects of misclassifications and patchiness of the pellet wastage record on overall system accuracy. Single-frame food pellet detection accuracy was based on the difference between computer-generated and actual frame counts of pellets greater than 30 pixels in size. A pellet wastage event was defined as a median of three or more visible pellets per frame. During tests on still video frames from different feeding events, the system missed 0.1±0.1 to 1.3±0.4 pellets frame⁻¹, and miss-classified as pellets 0±0.1 to 2.3±0.5 objects frame⁻¹ (n=264). Most missed pellet images were on top of fish images. Waste matter accounted for 65% of the misclassifications, while particles associated with poor camera maintenance accounted for approximately 24%. The average response time to a pellet wastage event was 5.1 and 11.4 s for sampling rates of 2 frames s⁻¹ and 0.5 frames s⁻¹, respectively (n=20 different pellet wastage events). The longest response time (26 s) occurred when fish were amassed against the camera and/or covering pellets. Using appropriate camera lens, camera positioning and/or ‘warning’ software can address fish-interference problems.     

Investigations of physiological and pathological levels of total plasma protein in rainbow trout, Oncorhynchus mykiss (Walbaum)

This study was aimed at construction of reference (physiological) value intervals determined by lower 2.5% and upper 97.5% quantiles for total plasma protein (TPP) in farmed rainbow trout, Oncorhychus mykiss (Kamloops strain), aged 10–12 months (n=755). Total plasma protein in male trout from raceway culture was found to be significantly greater (38–58.3 g L^?1) relative to females (31–51.5 g L^?1). Total plasma protein in trout from cage culture was significantly greater (32–54 g L^?1) compared with the raceway culture (31–49 g L^?1). Moderate product–moment correlations between TPP and cholesterol (r=0.8730), TPP and total calcium (r=0.8188), TPP and alanine aminotransferase (r=0.6200) and between TPP and aspartate aminotransferase (r=0.6430) were estimated. Proteinaemia was explained as a metabolic response to feed content, infections of bacterial or viral aetiology or to intoxications.     

Pollution of Environmental Endocrine Disrupting Chemicals(EDCs) in Water and Its Adverse Reproductive Effect on Fish

越来越多的环境内分泌干扰物（ EDCs）不断释放到环境,并通过大气沉降、地表径流、土壤淋溶和直接排放等方式进入水体,从而使水体成为 EDCs 存在的主要场所之一。为引起社会对水体 EDCs 污染的广泛关注,并积极采取EDCs 危害防治措施,保护鱼类资源和水生态系统,本文介绍了 EDCs 的分类,详述了自然水体、饮用水源水以及自来水中EDCs 污染情况,阐明了 EDCs 对鱼类的生殖危害。资料分析显示,EDCs 能够扰乱生物体内分泌功能,导致生殖器官、生殖机能和生殖行为异常,引起生育力下降,甚至生物繁殖机能损害,并最终导致种群数量下降,以至物种灭绝。虽然国内外已经开展了一些关于 EDCs 对生物危害等方面的研究,但大都处于起步阶段,存在着基础研究薄弱、识别和鉴定困难或代价太大等问题,有关工作亟需全面、深入开展。     

饲料磷脂对仔稚鱼营养生理的研究进展

近年来,磷脂(Phospholipids,PL)在仔稚鱼营养生理所发挥的作用引起人们广泛重视。综述了近年来饲料磷脂对仔稚鱼生长表现、消化道、骨骼发育以及脂肪代谢等方面的影响,以期为磷脂在水产苗种饲料中合理添加与应用提供理论参考。     

Fish larvae: zooplankton relationships in microcosm simulations of earthen nursery ponds. II. brackish water system

A simulation of the effects of predation intensity on zooplankton composition in brackish water nursery ponds was carried out in order to address the problem that commercial fish nurseries encounter in obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed. The experimental system consisted of twelve 130 l containers with treatments of four densities (0, 1, 2, or 4 larvae l⁻¹) of common carp (Cyprinus carpio L.), stocked on the 6th day after filling the containers. Zooplankton-environment relationships were explored using factor analysis. Factor analysis allowed identifying several groups of zooplankters that responded in different ways to fish larvae predation pressure. The first factor represented a general measurement of rotifer abundance, and the second identified the direct effect of size-selective fish predation. Since no rotifers were present in the filling water, all these species were autochthonous populations that hatched from resting forms in the sediment and reproduced. In the absence of fish predation, this led to a steep rotifer increase. Fish predation started when the rotifer concentration was just starting to increase and their direct predation reduced and delayed the rotifer abundance peak. This effect increased with the increase in fish larvae density. Estimations of rotifer consumption by fish larvae in this experiment were higher than similar calculations from data of the literature, which led us to test the hypothesis that factors other than direct predation were affecting rotifer population dynamics. The mechanisms involved in rotifer population regulation are discussed. It was concluded that in commercial nurseries, increased larvae production can be achieved by keeping the larvae density at an intermediate level and stocking fish to match the increasing phase of the rotifer peak. Under reasonable larvae density (up to 2 l⁻¹) it seems that the direct predation effect of fish larvae on rotifer dynamics is minor, compared to fish induced self regulation.     

亚热带水产养殖寒灾预警系统的设计与实现

通过对亚热带水产养殖现状的分析，论述了亚热带水产养殖寒灾预警系统建设的必要性、研究的目标和任务，详细介绍了系统的结构和框架，以及亚热带水产养殖寒灾预警的几个关键问题及其解决方法。     

鱼精粉在肉鸡日粮中替代进口鱼粉的效果

选用ＡＡ肉鸡进行试验，试验在生产后期进行，试验分为两组：对照组（含有３％的秘鲁鱼粉）和试验组（含有３％的鱼精粉），两组的营养水平接近。试验组平均日增重为４７．１８ｇ，对照组为４７．０６ｇ；试验组的料肉比为２．６８４，对照组为２．７４５。两者的重要生产性能指标接近，差异不显著。试验结果表明，在生长后期的肉鸡日粮中，使用鱼精粉替代进口鱼粉并不影响试验鸡的生产性能。