印度洋黄鳍金枪鱼生物学特性的初步研究

以闽南-台湾浅滩渔场历次海洋科学调查所获得的初级生产力为基础,并于2000-2001年对该渔场的鱼类资源组成结构、浮游植物有机碳含量、生态效率、52种主要经济鱼类的营养级及其有机碳含量等的调查、分析和检测,获得相关的生态参数后,应用营养动态模型和Cushing模型,估算鱼类资源的生态容量(潜在生产量),同时也应用Steele模型分别估算中上层鱼类、底层鱼类的资源生产量,进而从鱼类资源生产量中分离出近底层鱼类的资源生产量。然后采用Cadima模式和MSY简单模式估算鱼类及其各生态类群资源最大可持续开发量,并从捕捞现状和主要种群生态学参数的变化,讨论鱼类及其不同生态类群的开发利用水平。旨在为渔业决策部门今后在该渔场实行TAC和渔获量配额制度提供科学依据。估算结果:鱼类资源生态容量为98.63×104t,最大可持续开发量为48.35×104t。其中中上层鱼类资源生产量为56.90×104t,最大可持续开发量28.35×104t,底层和近底层鱼类资源生产量分别为19.45×104t和22.28×104t,合计最大可持续开发量为21.28×104t。然而,底层和近底层鱼类实际年渔获量自1994年以来已连续9年超过其最大持续可开发量,呈过度捕捞。中上层鱼类实际年渔获量至今尚未超过其最大可持续开发量。因此,对于底层和近底层鱼类资源必须采取有效管理措施,防止资源继续恶化。     

闽中渔场不同生态类群的鱼类资源生产量

本文以海洋生态系统营养动力学为理论依据,依据台湾海峡历次海洋科学调查在闽中渔场所获得的初级生产力为基础,通过对该渔场的浮游植物有机碳含量和生态效率及61种主要鱼类的营养级,58种主要鱼类有机碳含量的调查、检测。采用营养动态模型和Cushing模型估算鱼类资源潜在生产量,同时采用Steele模式估算中上层鱼类和底层鱼类资源生产量,进而从鱼类生产量中分离出近底层鱼类资源的生产量;采用Cadima模式估算鱼类及其不同生态类群的最大可持续开发量。估算结果:营养动态模型和Cushing模型估算鱼类资源潜在生产量分别为38.52×104t和44.34×104t,平均41.43×104t;Steele模式估算中上层鱼类和底层鱼类资源生产量分别为25.31×104t和8.05×104t,近底层鱼类资源生产量为8.07×104t;Cadima模式估算鱼类最大可持续开发量为25.41×104t,中上层鱼类最大可持续开发量为13.96×104t,底层和近底层鱼类最大持续可开发量为9.51×104t;1994年以来鱼类实际年渔获量在27.00×104t~40.01×104t,已连续11年超过了鱼类资源最大可持续开发量。1994年以来投入的捕捞力量为3702艘~5967艘福建标准机动单拖渔船,也连续11年超过了Schaefer和Fox2种剩余产量模式估算的最大持续捕捞力量3678艘福建标准机动单拖渔船,呈现捕获量和捕捞力量“双超”局面。底层和近底层鱼类渔获量自1985以来连续19年超过其最大可持续开发量;中上层鱼类渔获量1998年以来连续6年超过其最大可持续开发量;鱼类的主要种群结构出现简单化、小型化和低龄化,生态学参数渐近体长L∞和渐近体重W∞趋小,个体生长曲率K加大,体重生长拐点tr提前,初届性成熟体长趋小,捕捞死亡系数提高和开发比率上升,资源明显衰退。必须加强对该渔场鱼类资源的管理,采取有力措施控制捕捞力量的投入和渔获量的产出,以防鱼类资源进一步恶化。     

闽东渔场鱼类资源生态容量和最大可持续开发量

以海洋生态系统营养动力学为理论依据,根据历次调查所获得的闽东渔场初级生产力资料,通过对该渔场浮游植物有机碳含量和生态效率的测算、52种主要鱼类营养级及其有机碳含量的检测,采用营养动态模型和Cushing模型估算鱼类资源生态容量(自然生产量),采用Cadima模式和MSY简单模式估算鱼类资源最大可持续开发量。估算结果:闽东渔场鱼类资源生态容量平均为6.308×10~5t,最大可持续开发量为3.268×10~5t。1994年以来闽东渔场实际年渔获量3.435～4.685×10~5t,平均4.267×10~5t,已连续9年超过鱼类资源最大可持续开发量,呈现过度捕捞态势。必须实行渔获量负增长制度才能使鱼类资源得到有效恢复。     

闽南-台湾浅滩渔场鱼类及其不同生态类群的资源生产量

以闽南-台湾浅滩渔场历次海洋科学调查获得的初级生产力为基础,在对该渔场的鱼类资源结构调查、浮游植物有机碳含量检测和生态效率的测算、52种主要经济鱼类的营养级及其有机碳含量的检测后,先采用营养动态模型和Cusing模型估算鱼类资源的生态容量(潜在生产量),然后应用Seetile模型分别估算中上层鱼类、底层鱼类的资源生产量,进而从鱼类资源生产量中分离出近底层鱼类的资源生产量,采用Gadima模式和MSY简单模式估算各生态类群的鱼类资源最大可持续开发量,并讨论它们的开发利用程度.估算结果:鱼类资源生态容量为98.62×104 t,最大持续可开发量为48.34×104 t.其中中上层鱼类资源生产量为56.90×104 t,最大持续可开发量为28.35×104 t,底层和近底层鱼类资源生产量分别为19.45×104 t和22.27×104 t,合计最大持续可开发量为21.27×104 t.底层和近底层鱼类实际年渔获量自1994年以来已连续9年超过其最大持续可开发量,呈过度捕捞.中上层鱼类实际年渔获量至今尚未超过其最大可持续开发量.     

闽中渔场鱼类资源生产量和最大可持续开发量

以海洋生态系统营养动力学为理论依据,依据历次台湾海峡海洋科学调查在闽中渔场所获得的初级生产力为基础,通过2000~2001年对该渔场的浮游植物有机碳含量和生态效率及61种主要经济鱼类的营养级,58种主要鱼类有机碳含量的调查、检测,采用营养动态模型和Cushing模型估算鱼类资源生产量;进而采用Cadima模式和剩余产量模式估算鱼类资源最大可持续开发量。估算结果:营养动态模型估算鱼类资源潜在生产量为38·59×104t,Cushing模型估算为43·68×104t;Cadima模式估算最大可持续开发量为25·32×104t;Schaefer和Fox模式估算最大可持续开发量分别为23·96×104和25·28×104t,估算的最大持续捕捞力量换算为以福建单拖渔船艘为标准分别为3372和3983艘;1994年以来实际年渔获量在27·00×104~40·01×104t,实际捕捞力量在3897~5967艘标准单拖渔船,已连续11年超过了鱼类资源最大可持续开发量和鱼类资源可承载的最大持续捕捞力量。主要鱼类种群结构出现简单化、小型化和低龄化,生态学参数渐近体长L∞和渐近体重W∞趋小,个体生长速率K加大,体重生长拐点tr提前,初次性成熟年龄提早,捕捞死亡系数提高和开发比率上升,资源明显衰退。必须加强对该渔场鱼类资源的管理,采取有力措施控制捕捞力量的投入和渔获量的产出,以防鱼类资源进一步恶化。     

闽南—台湾浅滩渔场鲐鲹鱼类群聚资源生产量和允许总渔获量

以海洋生态系营养动力学为基础,采用Steele模式估算闽南—台湾浅滩渔场中上层鱼类资源年生产量为86.14×10~4t,进而以鲐鲹鱼类群聚资源在中上层鱼类资源的比例,估算鲐鲹鱼类群聚资源的年生产量为51.76×10~4t。Gulland和MSY简单模式估算鲐鲹鱼类群聚资源的最大持续产量分别为25.00×10~4t和25.88×10~4t。Schaefer和Fox剩余产量模式估算鲐鲹鱼类群聚资源的最大持续产量分别23.60×10~4t和23.41×10~4t,最大持续捕捞力量分别为1140.41×10~4kw·d和1266.66×10~4kw·d。折算为福建灯光围网渔船分别为424和471组,并从开发现状和种群生态学及捕捞死亡等参数分析鲐鲹鱼类群聚资源的开发前景。     

汕头～台湾浅滩生态系统渔业资源生产量及最大持续产量评估

本文以汕头～台湾浅滩海域的初级生产力为基础,以主要鱼类品种的营养级及其有机碳含量和生态效率,运用营养动态模型和Cushing模型估算海域生态系统渔业资源生产量,同时,运用Gulland模式和MSY简单模式估算渔业资源最大可持续开发量,结果表明该海域渔业资源生产量为77.4万吨,最大可持续开发量为45.6万吨,近十年来全渔场实际年捕捞量在55万吨以上,超过了渔业资源的最大持续产量,处于过度捕捞状态。     

台湾海峡及邻近海域渔业资源可持续开发量研究

利用1999～2001年课题组在台湾海峡及邻近海域采集的海洋渔业资源生物资料和在岸上采集的生产技术资料,通过分析渔业资源种类组成和结构、测算初级生产力,检测浮游植物含碳率,鱼类、虾蟹类、头足类等主要种的营养级及其含碳量率、测算生态效率;利用Cushing模型和营养动态模型估算该海区的潜在渔业资源量,利用Cadima经验公式和Gulland经验公式估算渔业资源最大持续开发量。结果表明,该海区的潜在渔业资源量为250.34×104t,最大可持续开发量为136.98×104t。2000年该海区的实际年捕捞量为217.2×104t,超过了渔业资源的剩余产量80.22×104t。因此,为了持续利用该海区的渔业资源,应减少投入捕捞力量和实行捕捞限额制度。     

汕头～台湾浅滩渔场中上层鱼类资源量 鲐黪鱼类群聚资源量及最大持续产量评估

本文以汕头～台湾浅滩海域生态系统渔业资源容纳量、初级生产力和资源生物含碳率及其转化为基础，根据鲐黪鱼类体内含碳率的测定结果，估算渔场中上层鱼类资源量和鲐黪鱼类群聚资源量，并运用Gulland模式和MSY简单模式估算渔业资源最大可持续开发量。结果显示：渔场中上层鱼类资源量为33．75万吨、最大持续产量16．875万吨：渔场鲐黪鱼类群聚资源量20．25万吨、最大持续产量10．2万吨。近十年来全渔场实际年捕捞量在5．5—10万吨之间，中上层鱼类资源接近充分利用。     

闽南、台湾浅滩渔场主要捕捞作业数量配置

根据评估的闽南、台湾浅滩渔场渔业资源生态容量121.33×104t和最大持续产量63.32×104t及闽南、台湾浅滩渔场不同类群渔业资源的开发利用现状,用单位捕捞力量渔获量和平均单船功率配置福建省在闽南、台湾浅滩渔场主要捕捞作业的功率和渔船数量,以达到渔业资源的合理利用和养护,促进闽南、台湾浅滩渔场的可持续发展。     

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.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

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.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

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.     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

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.