三峡库区笋溪河流域水质评价及其空间差异

为了解三峡水库库尾地区面源污染现状,以重庆市江津区笋溪河流域为研究对象,利用综合水质识别指数、内梅罗指数和主成分分析方法对笋溪河水质进行评价,主要评价指标有水温、pH、电导率、溶解氧、化学需氧量、总氮和总磷。结果表明:(1)笋溪河流域溶解氧为5.98～8.70 mg/L、化学需氧量为2～14 mg/L,总磷为0.008～0.105 mg/L,均处于Ⅰ类或Ⅱ类水质,总氮为0.64～2.03 mg/L,处于Ⅲ～Ⅴ类水质,污染严重。(2)3种水质评价方法均显示下游水质劣于上游水质,内梅罗指数在考虑平均超标水平的同时兼顾最大超标污染物,研究认为该指数的评价结果最能表现该地区的水质现状。(3)笋溪河上下游之间,溶解氧为上游显著高于下游,水温、pH、电导率、化学需氧量和总氮均为下游显著高于上游(P0.05),总磷浓度未发现有明显的差异(P0.05)。在后续管理中应提升城镇污水和农村污水的处理率,提高水肥利用率,以消减污染负荷、控制水污染趋势,从而改善区域水环境质量。     

汉丰湖入湖支流浮游植物群落结构及环境因子影响分析

为了准确反映汉丰湖的水环境状况,通过浮游植物监测和环境因子监测相结合,探讨汉丰湖入湖支流东河、桃溪河、南河、头道河浮游植物群落结构特征及其与水体理化因子的关系,对小江中上游开县汉丰湖4条主要支流的水体理化指标和浮游植物进行了采样分析,在东河、南河、桃溪河、头道河各设置3个监测点,于2013年3、6、9、12月各采样1次。结果表明,4条入湖支流共采集鉴定浮游植物8门、84属、218种（含变种）,以硅藻（107种）和绿藻（64种）种类居多,其次是蓝藻（31种）,这3类的种数占浮游植物总数的92.7%,其它5门的种类数较少。各支流浮游植物种类数由低到高依次为东河（83种）、桃溪河（100种）、南河（106种）、头道河（120种）,其密度均值在105数量级,南河下游浮游植物密度在夏季出现最大峰值,达到1.06×107 个/L,在大部分时段均以蓝藻占优势。水体理化指标监测数据显示,汉丰湖4条主要支流的总氮、总磷、pH、溶氧、水温、CODMn和电导率均值分别为1.00~1.61 mg/L、0.03~0.11 mg/L、7.82~8.53、6.65~7.03 mg/L、17.9~20.4℃、2.07~4.57 mg/L、269.25~522.50 μS/cm;其中,南河的总氮、CODMn较高,头道河的总磷较高,各支流的水温、溶氧、pH较为接近。浮游植物与环境因子的相关性分析表明,东河的裸藻、桃溪河的绿藻以及头道河的蓝藻密度均与水温显著相关（P<0.05）,南河的硅藻和绿藻密度与水温极显著正相关（P<0.01）,东河的甲藻密度与总磷浓度极显著相关（P<0.01）,桃溪河的硅藻和甲藻密度与总磷浓度显著相关（P<0.05）,绿藻密度与总氮浓度显著负相关（P<0.05）,硅藻密度与总氮浓度极显著负相关（P<0.01）;浮游植物分布及密度主要受水温、总氮和总磷的影响。     

汉丰湖支流浮游植物群落结构及环境因子影响分析

为了准确反映汉丰湖的水环境状况,通过浮游植物监测与环境因子监测相结合,探讨小江中上游汉丰湖入湖支流东河、桃溪河、南河、头道河浮游植物群落结构特征及其与水体理化因子的关系,对水体理化指标和浮游植物进行了采样分析,在东河、南河、桃溪河、头道河各设置3个监测点,于2013年3、6、9、12月各采样1次。结果表明,4条入湖支流共采集鉴定浮游植物8门、84属、218种(含变种),以硅藻(107种)和绿藻(64种)居多,其次是蓝藻(31种),这3类的种数占浮游植物总数的92.7%,其它5门的种类数较少。各支流浮游植物种类数由低到高依次为东河(83种)、桃溪河(100种)、南河(106种)、头道河(120种),其密度均值在105数量级,南河下游浮游植物密度在夏季出现最大峰值,达到1 160×104个/L,在绝大部分时段均以蓝藻占优势。水体理化指标监测数据显示,汉丰湖4条主要支流的总氮、总磷、p H、溶氧、水温、CODMn和电导率均值分别为1.00~1.61 mg/L、0.03~0.11 mg/L、7.82~8.53、6.65~7.03 mg/L、17.9~20.4℃、2.07~4.57 mg/L、269.25~522.50μS/cm;其中,南河的总氮、CODMn较高,头道河的总磷较高,各支流的水温、溶氧、p H较为接近。浮游植物与环境因子的相关性分析表明,东河的裸藻、桃溪河的绿藻以及头道河的蓝藻密度均与水温显著相关(P0.05),南河的硅藻和绿藻密度与水温极显著相关(P0.01),东河的甲藻密度与总磷浓度极显著相关(P0.01),桃溪河的硅藻和甲藻密度与总磷浓度显著相关(P0.05),绿藻密度与总氮浓度显著负相关(P0.05),硅藻密度与总氮浓度极显著负相关(P0.01);浮游植物分布及密度主要受水温、总氮和总磷的影响。     

呼伦湖及其周围水域春季浮游植物功能群及其影响因子

2018年春季(5月),在呼伦湖及其周围水域不同类型水体中设置28个采样点(呼伦湖湖域17个,周围河流流域11个)调查了浮游植物种类和数量,监测了水环境因子,探讨了呼伦湖及其周围水域春季浮游植物功能群及其与环境因子之间的关系。结果表明:春季在呼伦湖及其周围水域中共鉴定出7门80种浮游植物,其中呼伦湖中以绿藻门为主,而周围河流流域则以硅藻门为主。调查区域浮游植物共分为20个功能群,其中C、X2、J和D为重要功能群。Pearson线性相关分析和RDA分析均表明:化学需氧量和电导率是影响呼伦湖及其周围水域浮游植物功能群最主要的水环境因子,功能群C和D同化学需氧量和电导率显著负相关,功能群J同化学需氧量和电导率显著正相关,而功能群X2受水温和溶解氧影响较大,同水温和溶解氧显著正相关。用GB3838-2002评价标准评估各采样点的总氮、总磷及化学需氧量结果表明,呼伦湖内(M9、M16)水质极差,总氮、总磷和化学耗氧量均超过国家V类水标准(2mg/L、0.2mg/L、40mg/L);呼伦湖内西岸(M10～M13)、湖中心(M22～M24)以及周围水域的呼和诺尔(M3)、乌兰诺尔(M27)水中总磷和化学需氧量污染极为严重。结果发现,周围河流水质明显优于呼伦湖内水质。     

南水北调东线南四湖渔业水域水质状况分析

为掌握南水北调东线南四湖的水质现状，于2021年对4个湖区7个站位进行了周年调查，并采用单因子分析和综合营养状态指数法对水质状况进行了评价。结果表明：南四湖水体氨氮和亚硝氮浓度分别为0.166±0.015mg/L和0.050±0.009mg/L,总氮、总磷和CODMn浓度分别为1.767±0.191mg/L、0.053±0.005mg/L和10.58±0.46mg/L并分别超地表水III类水质标准76.69%、6.76%和76.41%;综合营养状态指数介于46.78～66.16,南四湖总体为轻度富营养状态，但部分水域仍存在较重的富营养化问题。伴随南水北调东线的常态化调水及多种水质涵养措施的实施，南四湖水体的富营养状况有所转好，但在部分季节的部分区域仍存在富营养化风险。     

乌杨调节坝运行初期汉丰湖浮游植物群落结构及其与环境因子的相关性分析

为了解乌杨调节坝正式运行初期汉丰湖水体情况,2016年10月—2017年10月对汉丰湖浮游植物群落及水质状况进行了调查。结果显示,调查期间共检出浮游植物7门58属114种,其中绿藻门和硅藻门最多,分别占39.47%和38.60%。尖针杆藻、梅尼小环藻和啮蚀隐藻等为优势种。浮游植物平均密度为8.64×10~5 ind./L;平均生物量为2.03 mg/L;其中,平均密度和生物量在2016年12月最小,2017年2—8月不断增大,10月份有所下降;四个采样点的平均密度和生物量差异均不显著。各采样点浮游植物Margalef物种丰富度指数(d_(Ma))为1.69～5.23;Shannon-Wiener指数(H’e)为1.12～2.75;Pielou均匀性指数(J_e)为0.45～0.96。水温、高锰酸盐指数、总磷、总氮、氨氮的变化范围分别为12.7～31.5℃、1.54～4.92 mg/L、0.01～0.18 mg/L、0.20～1.11mg/L、0.10～0.81 mg/L。冗余分析(RDA)结果表明,汉丰湖浮游植物与高锰酸盐指数、总磷、亚硝态氮和氨氮呈正相关,与透明度呈负相关。     

三峡水库试验性蓄水后小江沿岸水质研究

根据2010年3月－12月对三峡水库小江沿岸水体的水质监测数据,分析总氮、总磷、化学需氧量和叶绿素a等水质因子的时空变化规律,以及叶绿素a与水质因子之间的相互关系,评价水体富营养化水平。结果表明：总氮、总磷、化学需氧量和叶绿素 a含量分别为1.980±0.119mg/L、0.114±0.018mg/L、9.520±1.748 mg/L和23.342±8.810 mg/L,小江沿岸水体呈现中度富营养化水平。叶绿素a与水质因子间的相关关系分析发现,叶绿素a含量与温度、pH、溶解氧、亚硝酸氮和化学需氧量显著相关,与总氮、总磷不具有显著相关性。这说明小江沿岸水体叶绿素a含量与总营养盐无关,而主要与水体所含的有机质含量有关。     

东圳水库水质模拟预测及污染物总量控制研究

研究东圳水库水质变化趋势,计算工程实施后的污染物削减量,为水质保护提供依据。利用SMS模型基于二维不可压缩流体运动方程,建立东圳水库水域二维水流水质数学模型,采用有限单元法,模拟预测东圳水库水环境状况,主要水质分析指标为高锰酸盐指数、氨氮、总氮和总磷。预测结果表明,按目前污染物排放状况,2018年东圳水库水体中污染物含量为氨氮0.14~0.21 mg/L(II类水质)、COD 3.3~3.9 mg/L(III类水质)、总磷0.052~0.062 mg/L(IV类水质),总氮1.1~1.6 mg/L(IV类水质)。实施社会经济调控、污染源防治和生态保育工程后,2018年,预计东圳水库高锰酸盐指数、氨氮、总氮和总磷共排放1 616.6、163.7、1 182.4和155.5 t/a,分别削减了1 501.8、439.9、756.4和105.2 t/a;总氮0.4~0.8 mg/L、总磷0.022~0.032 mg/L,降幅均达到50%以上,达III类水质标准;COD 2.0~3.0 mg/L、氨氮0.11~0.18 mg/L,达到II类水质标准。提出的实施方案对保护东圳水库的水质具有建设性意义,水体水质目标可达。     

天津七里海湿地水质质量现状分析与评价

2012年我们采用现场调查监测的方法,对七里海湿地水质的pH、溶解氧、化学需氧量、总磷、总氮、盐度等十几项水化因子进行了调查监测,并采用营养状态指数法对天津七里海湿地水质富营养化进行评价。评价结果显示:七里海所有监测站位的水质均呈富营养型状态。     

仙女湖网箱取缔后水质情况的调查

仙女湖网箱取缔后,"江西碳汇渔业"课题组对其水质变化情况进行调查研究,从2015年3月至2015年11月进行水温、pH值,透明度、总氮、总磷等理化指标进行监测,结果表明水质比以往有所好转,总氮、总磷指标达到Ⅱ类水标准。总氮的范围在0.012-1.145mg/L,平均值为0.266mg/L;总磷集中变化在0.001-0.01mg/L,平均值0.004mg/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.