泥蚶血清及血细胞免疫功能研究

初步研究了泥蚶（Ｔｅｇｉｌｌａｒｃａｇｒａｎｏｓａ）血细胞离体条件下的吞噬作用以及血清因子对其的影响,并测定经大肠杆菌注射以后,泥蚶血清中抗菌、溶菌、酚氧化酶（ＰＯ）、超氧化物歧化酶（ＳＯＤ）活力的变化。结果表明,泥蚶血清能促进血细胞对大肠杆菌的吞噬,但不能识别鸡红细胞。大肠杆菌激发后泥蚶血清中抗菌活力在１ｈ、１５ｈ和３０ｈ时实验组均显著高于对照组。溶菌活力实验组均高于对照组,但在１５ｈ差异不显著。ＰＯ活力实验组均低于对照组,在３０ｈ时差异极显著。ＳＯＤ活力在１ｈ时显著低于对照组,而在３０ｈ时显著高于对照组。     

病毒感染对栉孔扇贝血淋巴中过氧化氢酶和过氧化物酶活力的影响

用从病贝体内分离的非包涵体球形病毒感染栉孔扇贝,采用分光光度技术,分别于6,24,72h,测定栉孔扇贝血清和血细胞中过氧化氢酶(CAT)活力和过氧化物酶(POD)活力。结果表明,感染病毒后,血清中CAT活力在6,24,72h时,实验组均高于对照组,6h时差异极显著,24h时差异显著,72h时差异不显著;血细胞中CAT活力在6,24,72h时,实验组均高于对照组,6h和24h时差异极显著,72h时差异不显著。血清和血细胞中POD活力在6h和24h时,实验组均高于对照组,且均差异极显著。说明病毒感染后栉孔扇贝血淋巴中CAT和POD的活力增强。     

氨氮对拟穴青蟹的急性毒性及对其血清免疫相关酶活力的影响

采用静水法研究氨氮对拟穴青蟹(Scylla paramamosain)的急性毒性及在氨氮初始浓度分别为0(C0,对照组)、10(C10组)、20(C20组)、30(C30组)、40(C40组)、50 mg/L(C50组),胁迫时间分别为0、6、24、48、72 h的条件下对其血清中碱性磷酸酶(AKP)、酸性磷酸酶(ACP)、溶菌酶(LZM)、超氧化物歧化酶(SOD)和酚氧化酶(PO)活力的影响。结果显示,总氨氮对拟穴青蟹24 h和48 h的半致死浓度分别为104.793、66.124 mg/L,安全浓度为7.90 mg/L,非离子氨对拟穴青蟹24 h和48 h的半致死浓度分别为8.396、5.298 mg/L,安全浓度为0.63 mg/L。在胁迫6、24、48与72 h时,各实验组的LZM活力均显著低于对照组(P0.01)。相较于对照组,C10、C20及C40组在24 h的AKP、ACP活力均显著升高(P0.05)。C20组在24 h的SOD活力则显著低于其他胁迫时间点(P0.05)。胁迫72 h时,C30、C40及C50组的PO活力显著高于对照组(P0.05)。该实验条件下,不高于40 mg/L的氨氮可在24 h内使拟穴青蟹血清中的AKP与ACP活力显著升高,而50 mg/L的氨氮则对其具有抑制作用;各实验组浓度氨氮均在72 h内对拟穴青蟹血清中的LZM活力具有显著的抑制作用,对PO活力具有明显的刺激作用,对SOD活力无显著影响。     

泥蚶血细胞耐饥饿及抗菌力特性的研究

显微镜下观察泥蚶血细胞抗菌能力以及在不同饥饿条件下细胞形态结构的变化。结果表明:经饥饿处理后,泥蚶血细胞随着时间的迁移,出现细胞形态不规则、胞质色泽变浅、胞质颗粒物减少、胞膜边缘光滑度减小等现象。血细胞对大肠杆菌、奥斯陆莫拉氏菌、脲放线杆菌均具较高的噬菌率,噬菌实验过程中血细胞形态结构以及细胞组分不断产生变化。细胞抗菌活性检测结果表明:血细胞对三者都具有一定的抗菌活性,活性依次为:大肠杆菌>奥斯陆莫拉氏菌>脲放线杆菌。     

插核手术对合浦珠母贝免疫水平的影响

对插核手术前后合浦珠母贝血清的超氧化物岐化酶（SOD）活力、溶菌活力和抗菌活力以及血细胞的吞噬活性进行了比较研究。结果表明：插核手术后贝血清的SOD活力明显上升,溶菌、抗菌活力明显下降,血红细胞的吞噬活性降低,化学发光的各种参数显著改变,说明贝的体液和细胞免疫水平都明显降低。据此推断手术贝的免疫力低下是导致手术贝高死亡率的最根本原因。     

浒苔多糖对扇贝SOD酶和溶菌酶活力的影响

华贵栉孔扇贝体内注射了体积分数0．1％、0．25％的浒苔多糖后，在第24、48、72小时分别测定了扇贝血淋巴中SOD酶和溶菌酶活力。实验组扇贝血清中SOD酶活力在不同测定时间都显著地高于对照组，而血细胞中SOD酶活力在注射24h后和48h后显著地高于对照组；实验组扇贝血淋巴中溶菌酶在注射24h后和48h后显著高于对照组。说明浒苔多糖具有增强华贵栉孔扇贝免疫活性的作用。     

氨氮胁迫对三疣梭子蟹酚氧化酶原系统和免疫指标的影响

以三疣梭子蟹(Portunus trituberculatus)为研究对象,研究氨氮胁迫对其酚氧化酶原系统和免疫指标的影响.实验分0mg/L、1 mg,L、5mg,L、20mg,L氨氮处理组,分别于0h、6h、12 h、24 h、48 h取样并进行相关指标测定.结果表明:氨氮胁迫对三疣梭子蟹血淋巴多巴胺含量、血细胞数量、血细胞酚氧化酶原(proPO)活力和mRNA表达以及抗菌、溶菌活力的影响显著(P<0.05).各处理组血淋巴多巴胺含量于6 h达到最大值,12 h后恢复至对照组水平;各处理组血细胞数量均呈明显下降趋势,除20mg/L氨氮处理组半颗粒细胞、总细胞数量表现为逐渐下降趋势外,其他处理组3类血细胞和总细胞数量分别于12h或24h时降至最低值,然后保持稳定.各处理组上述指标分别呈明显下降、升高、下降和峰值变化趋势,其中1mg/L处理组血细胞proPO活力在12 h后恢复至对照组水平,而mRNA表达与对照组差异不显著,其他处理组血细胞proPO活力和mRNA表达分别于12h、6h后保持稳定;各处理组抗菌活力于6h或12h达到最小值,然后恢复至对照组水平,而溶菌活力在24 h后趋于稳定,且1 mg/L处理组与对照组无明显差异.各处理组血细胞数量、proPO活力、溶菌活力在稳定后均与氨氮浓度呈明显的负相关性,而血细胞proPO mRNA表达呈显著正相关性.由此可见,三疣梭子蟹在氨氮胁迫下血细胞数量、proPO活力和mRNA表达以及免疫指标表现出明显的时间剂量效应性,具有显著的免疫毒性效应.本研究旨在为三疣梭子蟹养殖水环境调控和病害防治提供基础依据.     

皂角苷对大菱鲆非特异免疫的增强作用

为评价皂角苷增强鱼类非特异免疫效果,分别用浓度为0、15和35 mg/L的皂角苷浸泡大菱鲆,分析了浸泡后6、12、24、48和72 h时大菱鲆白细胞的吞噬活力、血清补体旁路途径溶血活性、血清与黏液中溶菌酶活性、抑菌活性与碱性磷酸酶(AKP)活性及血清总蛋白浓度。结果显示,皂角苷低浓度组(15 mg/L)与高浓度组(35 mg/L)大菱鲆白细胞吞噬活力分别在浸泡后12与24 h出现显著的增高(P0.05)。实验组大菱鲆血清中补体旁路途径溶血活性除低浓度组在12与24 h较对照组低外,其他检测时段均高于对照组(P0.05)。血清溶菌酶活性最高值出现在低浓度组浸泡后6 h时,黏液中未能检测出。不同时间点各组大菱鲆黏液抑菌活力变化幅度较大,两实验组黏液抑菌活力在浸泡后6与12 h时较对照组提高,两个实验组间无差异(P0.05)。血清中AKP活力高峰值出现在浸泡后6与12 h,该时段AKP的活力显著高于对照组,且实验组间存在差异(P0.05),而黏液中AKP高峰值出现在12 h,该时段AKP的活力显著高于对照组(P0.05),实验组间无差异。浸泡皂角苷后6 h高浓度组血清中蛋白浓度达到最高值,除12 h时各组差异不显著外(P0.05),24~72 h高浓度组中血清蛋白含量均高于低浓度及对照组(P0.05)。研究表明,皂角苷具有提高鱼类非特异免疫水平的效果。     

Cd胁迫对泥蚶Cd积累及相关生理代谢的影响

为了探讨镉(Cd)胁迫对泥蚶(Tegillarca granosa)体内重金属 Cd 含量积累、相关酶活力变化及基因表达水平的影响, 本研究将泥蚶暴露于 Cd 质量浓度为 0 mg/L、0.05 mg/L、0.1 mg/L、0.5 mg/L 的海水中, 对其软体部 Cd 含量, 超氧化物歧化酶(SOD)和三磷酸腺苷酶(ATP)的酶活力, 丙二醛(MDA)含量以及 ATP 结合盒转运子 A 家族(ABCA3)、 金属硫蛋白(MT)、ATP 合酶(ATP)、超氧化物歧化酶(SOD)基因表达等指标的变化进行分析。结果显示, Cd 胁迫后泥蚶软体部 Cd 含量明显增加, 呈现明显的时间–剂量效应；Cd 胁迫后 0.05 mg/L 和 0.1 mg/L 质量浓度组中鳃和外套膜 Cd 含量显著高于其他组织(P＜0.05), 0.5 mg/L 组内脏团 Cd 含量最高。Cd 胁迫后泥蚶内脏团中 SOD 酶和 ATP 酶活力及 MDA 含量前期呈上升趋势, 后期呈现下降趋势, 且均高于对照组。Cd 胁迫后 ABCA3、SOD、MT 基因表达上调, ATP 合酶基因的表达与对照组相比没有显著变化。胁迫后泥蚶软体部 Cd 大量增加, 诱导机体产生氧化应激反应, 泥蚶通过调整自身酶活力和相关基因表达水平的变化, 减少 Cd 胁迫产生的氧自由基对自身的毒害作用。     

氨氮对凡纳对虾免疫指标的影响

以凡纳对虾(Litopenaeus vannamei)为研究对象,研究氨氮对其免疫指标的影响。实验氨氮质量浓度梯度设置为0.05(对照)、0.5、1.0、1.5、2.0、2.5 mg／L,各氨氮梯度用4g／L的氯化铵溶液来调节。将暂养在自然海水(对照)中的凡纳对虾分别放入各实验梯度中,对虾体长为(8.5±0.5)cm。结果表明,氨氮对凡纳对虾血细胞数量、血清中的酚氧化酶活力、溶菌和抗菌活力的影响显著(F>F0.05),且随着氨氮质量浓度的升高,血细胞数量和溶菌、抗菌活力降低,酚氧化酶活力升高;在0-24 h实验时间内,各处理组(对照组除外)对虾血细胞数量和溶菌、抗菌活力呈下降趋势,酚氧化酶活力呈上升趋势,24 h后稳定在较低水平上。实验说明,随着氨氮水平升高,凡纳对虾免疫力明显下降,对病原菌的易感性提高,因此在养殖过程中,环境氨氮变化幅度不应超过0.5 mg／L,或长时间维持在较高氨氮水平(>0.5 mg／L)。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.