中国北部海域主要无脊椎动物群落结构及多样性

根据2010年5月、8月在渤海及黄海北部进行的底拖网定点调查资料,分析了中国北部海域无脊椎动物群落结构及其生物多样性。中国北部海域共捕获无脊椎动物32种,其中虾类15种,蟹类10种,头足类7种;在渤海,虾类占主导地位,春季其生物量及密度比例分别为86.57%和96.55%,夏季为46.16%和80.85%;在黄海北部,春季蟹类在生物量组成中占绝对优势地位(91.07%),夏季则为头足类占优势地位(80.41%)。运用相对重要性指数(IRI)研究了渤海及黄海北部的优势种类组成,优势种类随季节及海区的变化差异较大。使用多样性指数D、H’、J’分析了无脊椎动物群落的多样性,渤海生物多样性高于黄海北部。分析了渤海及黄海北部群落物种组成相似性,两个海区物种组成相似性分别为春季0.315和夏季0.297。使用季节更替指数和迁移指数研究了两个海区无脊椎动物群落的稳定性,表明从春季至夏季,黄海北部部分种类向渤海迁移。     

长江口及邻近海域无脊椎动物群落结构及其生物多样性研究

根据2006年6月、8月和10月长江口及邻近海域无脊椎动物的底拖网定点捕捞调查资料,研究区域内无脊椎动物的群落结构及其生物多样性.调查共捕获无脊椎动物49种,共2232.277kg、1 037 641尾.分析了调查区域内虾类、蟹类、头足类及口虾蛄4个类别的生物量及密度组成,虾类在密度组成中占主导地位,占总密度的90.1%,蟹类在生物量组成中占主导地位,占总生物量的58.2%.运用相对重要性指数(IRI)研究不同种类的生态优势度,细点圆趾蟹(1 822.64)为6月份的唯一优势种,双斑蝠(1 573.90)及中华管鞭虾(1 135.36)为8月份优势种.三疣梭子蟹(3 667.30)、鹰爪虾(1 568.35)及口虾蛄(1248.70)为10月份优势种.使用多样性指数D、H'、J分析了该水域无脊椎动物群落的多样性,发现在3个航次调查中,10月份多样性指数最高;在不同调查区域,长江口中部多样性指数最高.采用Bray-Curtis指数Cn比较了长江口不同区域的无脊椎动物群落之间物种组成的相似性.结果表明,长江口中部及长江口南部种类组成相似性最高,Cn=0.628;长江口北部和长江口南部种类组成相似性最低,Cn=0.1660与历史资料对比,长江口及邻近海域无脊椎动物主要捕获种类变化不大,群落结构比较稳定.     

舟山沿岸渔场春秋季鱼类群落结构特征分析

根据2015年11月(秋季)、2016年5月(春季)在舟山沿岸渔场开展的渔业资源调查中所获得的鱼类资料，采用群聚的物种相似性、多样性指数、RDA分析等方法，对该海域鱼类种类组成、生态类群、多样性和群聚特征进行了分析。结果显示，本调查共鉴定出鱼类81种，隶属于12目39科63属，以近海暖水种为主；Jaccard相似性指数为37.04%，处于中等不相似水平；优势种计算结果显示，春季优势种为六丝钝尾虾虎鱼(Amblychaeturichthys hexanema)，渔获量占总渔获量的42.16%；秋季优势种为龙头鱼(Harpodon nehereus)，占总渔获量的43.56%；春季多样性高于秋季，但2个季节的多样性指数平面分布相似，均为调查海域南部最低，越往北多样性指数越高，且东部海域高于西部海域；ANOSIM检验显示，各群落间差异极显著；相似性百分比(SIMPER)显示，蓝圆鲹(Decapterus maruadsi)、棘头梅童鱼(Collichthys lucidus)、龙头鱼等7种，中华小沙丁鱼(Sardinella nymphaea)、鳀(Engraulis japonicus)、七星底灯鱼(Benthosema pterotum)等9种，分别是春、秋季各组群的典型种及造成鱼类群落结构差异的主要分歧种。RDA研究结果显示，盐度、温度是舟山沿岸渔场鱼类群落结构主要的环境影响因子。     

南海中部海域秋冬季中层渔业生物群落结构的初步研究

根据2014年对南海中部海域秋冬季2个航次中层拖网调查数据,分析了中层渔业生物种类组成、优势种和多样性等群落结构特征。共鉴定中层渔业生物241种,其中鱼类196种、头足类21种、甲壳类24种,冬季的渔获种类高于秋季,但单位捕捞努力量渔获量(CPUE)略低于秋季。相对重要性指数(index of relative importance,IRI)结果表明,秋季IRI≥100的优势种群有25种,其中IRI≥500的优势种有5种,包括蝰鱼(Chauliodus sloani)、尾明角灯鱼(Ceratoscopelus warmingii)、条带眶灯鱼(Diaphus brachycephalus)、日本乌鲂(Brama japonica)和条带多光鱼(Diplophos taenia);冬季IRI≥100的优势种群有26种,其中IRI≥500的优势种有3种,分别为典型刺虾(Oplphorus typus)、蝰鱼和太平洋帆乌贼(Histioteuthis pacifica)。秋冬季的IRI组成不存在显著性差异(P0.05)。以个体数计算的中层渔业生物丰富度指数、均匀度指数和多样性指数冬季高于秋季,但优势度指数是冬季低于秋季。以生物量计算的多样性指标中,冬季中层渔业生物丰富度指数和多样性指数高于秋季,而优势度指数和均匀度指数则低于秋季。利用数量生物量比较曲线(abundance-biomass comparison curves,ABC)方法分析南海中部海域中层渔业生物群落的状况,结果显示,秋季中层渔业生物群落处于较大干扰状况,冬季群落处于中等干扰状况。     

春季黄河口海域2种网具渔获物组成的比较分析

根据2007年5月在黄河口海域弓子网和小型单船底拖网渔业资源调查资料，分析了2种网具的渔获物种类组成，并分别计算了Sorensen相似性指数（SS）、种类丰富度指数（R）、Shannon—Wiener多样性指数（H＇）、Pielou均匀度指数（J＇）和相对重要性指数（index of relative importance，IRI）。弓子网和底拖网的SS指数为0．63，2种网具渔获物组成的相似性较差。弓子网和底拖网的R、H’、J’指数分别为3．61、2．28、0．64和3．55、2．40、0．72，底拖网渔获物多样性程度高于弓子网。分析结果表明，2种网具的单位功率渔获量（catch per unit effort，CPUE）均不高，且存在选择性差和对幼体生物伤害严重的问题。     

长江上游珍稀特有鱼类国家级自然保护区干流段鱼类群落结构特征分析

长江上游珍稀特有鱼类国家级自然保护区位于向家坝坝下江段，随着金沙江下游梯级水电站相继蓄水运行和“十年禁渔”政策的实施，保护区干流段鱼类群落可能会发生改变。为探究“十年禁渔”前保护区干流段鱼类群落结构特征，基于该江段2017—2019年渔获物监测数据，对鱼类种类组成、生态类型、群落相似度、物种优势度、生物多样性以及群落结构稳定性等特征进行分析。结果显示，本次调查共采集到鱼类134种，隶属于7目21科83属，其中长江上游特有鱼类有27种，外来物种有12种，分别占总种类数20.15%和8.96%。鱼类群落以底层、产沉性卵、杂食性鱼类为主。等级聚类分析(Cluster)和非度量多维尺度分析(NMDS)显示，在一定的相似性水平上，保护区干流段鱼类的群落类型基本可分为3组，宜宾、泸州与合江可以聚为一组，巴南、江津分别独立成组。保护区干流优势种共有14种，其中瓦氏黄颡鱼是整个研究区域的优势种，在合江站点的优势度最高，IRI值为27.00%。Shannon-Wiener指数、Simpson指数、Margalef指数和Pielou指数变化范围分别为2.725～3.306、0.883～0.942、5.83...     

秋季黄海底层鱼类群落结构的变化

根据1985年和2000年秋季渔业生物资源底拖网调查资料，分析了黄海底层鱼类群落结构的时空变化。结果表明，渔业资源优势种的组成随区域和时间不同有着较大的差异。黄海北部和中部渔获种类组成相似性较高，北部与南部、中部与南部的相似性较低；黄海渔获生物种类组成年间相似性较高，为65。进一步的单因子ANOSIM分析表明黄海底层鱼类群落不同区域和年间种类组成没有显著性差异。黄海渔业生物多样性由北向南递减。与1985年相比，2000年鱼类群落长度谱表现出小型种类和小个体增多，大个体减少，且长度范围变小；主要优势种的长度组成也呈现小型化趋势。长度谱区域变化则是从北部向南部小个体数量增多，大个体数量减少。     

黄、东海渔业资源群落结构变化研究

为了解黄海和东海渔业资源群落结构的变化，基于2013年6月(夏季)和9月(秋季)黄、东海渔业资源底拖网调查数据，对渔业资源种类组成、优势种、渔获量空间分布、群落多样性和群落结构进行了研究。结果显示，共鉴定渔业种类185种，其中底层鱼类93种、中上层鱼类31种、甲壳类48种、头足类12种和贝类1种。在鱼类中，鲈形目种类最多，27科47属56种，占鱼类总种类数的45.2%。夏季优势种为鳀(Engraulis japonicus)、脊腹褐虾(Crangon affinis)、带鱼(Trichiurus lepturus)和小黄鱼(Larimichthys polyactis)，秋季优势种为三疣梭子蟹(Portunus trituberculatus)、小黄鱼、鳀和带鱼，优势种季节波动不大。秋季平均单位时间渔获量为46.60 kg/h，高于夏季(39.35 kg/h)。秋季航次调查中渔业资源较夏季更为集中，主要分布在长江口和吕泗渔场附近，其他断面渔获量较低。夏季航次群落多样性指数高于秋季航次。CLUSTER聚类分析表明，黄、东海渔业生物群落可分为2组，夏、秋季2组界线变动不大，2组聚类的形成可能受水温和长江径流影响。     

珠江口南沙海域秋季渔业资源群落结构特征

根据2015年11月珠江口南沙海域的渔业资源调查资料,对该海域秋季渔业资源群落组成、优势种和生物多样性等群落结构特征进行了初步研究。结果表明,该海域共出现渔业生物40种,以鱼类和甲壳类为主。其中,底层鱼类21种,中上层鱼类3种,甲壳类16种。相对重要性指数(IRI)可用来度量物种的生态优势度,秋季优势种类有亨氏仿对虾(Parapenaeopsis hungerfordi)和锐齿(Charybdis acuta)2种(IRI≥1 000)。该区域内各站位质量渔获率为0.63~11.15 kg·h~(-1),平均为4.23 kg·h~(-1);尾数渔获率为84~885尾·h~(-1),平均为433尾·h~(-1)。Shannon-Wiener多样性指数(H')为2.07,Margalef丰富度指数(D)为1.64,Peilou均匀度指数(J')为0.59。分析表明,该海域渔获物以小型经济甲壳动物和经济幼鱼为主,渔获个体偏小,总体上多样性空间差异不大。与该区域2002年同月份的调查数据相比,目前渔获物多样性下降明显,群落结构相对简单。     

沱江中游鱼类资源现状及多样性

为探究“十年禁渔”前沱江中游江段鱼类资源和物种多样性，于2017—2020年对该江段鱼类资源进行了8次调查，并对鱼类种类组成、生态类型、群落相似度、种群优势度、生物多样性以及群落结构稳定性等特征进行分析。结果显示，本次调查共采集鱼类87种，隶属于5目14科52属。其中，长江上游特有鱼类18种，外来物种6种，分别占总种类数的20.69%和6.90%。鱼类群落以底层、缓流型、产沉性卵、杂食性鱼类为主。相对重要性指数(IRI)显示，蛇、鲤等中小型鱼类为优势种。Shannon-Wiener指数、Simpson指数、Margalef指数、Pielou指数变化范围分别为2.700～3.742、0.873～0.968、5.374～11.323、0.737～0.887，表明沱江中游鱼类群落分布均匀。等级聚类分析(Cluster)和非度量多维尺度分析(NMDS)显示，在一定的相似性水平上，沱江中游江段鱼类的群落类型基本可分为3组，莲花山、麻柳坝工业园与铁路沟可以聚为一组，万古庙、五里店水电站、资州大桥、银山镇、二水厂与西林渡口聚为一组，沱桥独立成组。数量/生物量比较曲线分析结果显示，西林渡口和沱桥江段鱼...     

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.