Effect of frugivorous birds on the establishment of a naturally regenerating population of Chinese yew in ex situ conservation

The Chinese yew (Taxus chinensis) is catalogued as an endangered species in China because of the small size and senescent status of most populations. Its lack of natural regeneration is the most important reason for its endangered status. We investigated the regeneration of an ex‐situ conservation population, which was introduced into the Nanjing Botanical Garden Memorial Sun Yat‐Sen in the 1950s, and evaluated the role of frugivorous birds on the establishment of this regenerating population. Two hundred and thirteen individual yew seedlings and saplings were found on the hillside in 2006, and the nearest seedling was found more than 10 m away from mother trees. The spatial pattern of all seedlings and saplings occurred as a clumped distribution, which is typical for vertebrate‐dispersed plants. Six bird species were seen ingesting whole “fruits” at yew trees in the present study and 745 visits by avian frugivores were recorded. Red‐billed blue magpie (Urocissa erythrorhyncha), Chinese bulbul (Pycnonotus sinensis) and azure‐winged magpie (Cyanopica cyana) were the most frequent visitors over the two years of the study. Comparing the flights of departure and perching habitats of the three main bird species, we inferred that U. erythrorhyncha would be the most important disperser. This regeneration population has had good development over the past 20 or more years; frugivorous birds have removed seeds to the hillside every year until now, and seed germination and seedling growth continue to develop well under natural conditions. We suggest that the conservation system of the Chinese yew should be composed of yews, avian dispersers and habitats for seed germination and seedling growth.     

Effects of ethanol on fruit selection by frugivorous birds

Ethanol is a natural by-product of the fermentation process of fruit sugars. Its production started with the advent of fleshy fruits, which suggests a long-term association between ethanol and frugivores. Consequently, one suggestion is that because frugivores could use its odour to locate fruiting plants, they should show a preference for fruit with high ethanol concentrations. The aim of this study was to test this hypothesis by determining whether frugivorous birds show a preference for fruit laden with alcohol at levels equivalent to those of overripe fruits. Three species of frugivorous bird species were used for this study: the Cape White-eye (Zosterops virens), Speckled Mousebird (Colius striatus) and Red-winged Starling (Onychognathus morio). Birds were provided with two artificial fruit diets in pairwise choice tests: an experimental diet containing 1% ethanol and a control diet with no ethanol. For all species, no significant differences were observed in the amount of artificial fruit consumed between the food types. Given that the concentration of ethanol used in the study is assumed to represent that of overripe fruit, these results, in conjunction with previous studies, suggest that birds do not show a preference for fruits with high ethanol concentrations.     

Conflicting selection pressures on seed size and germination caused by carnivorous seed dispersers

Plants produce nutritious, fleshy fruits that attract various animals to facilitate seed dispersal and recruitment dynamic. Species-specific differential selection of seed size by multiple frugivorous disperser assemblages may affect the subsequent germination of the ingested seeds. However, there is little empirical evidence supporting this association. In the present study, we documented conflicting selection pressures exerted on seed size and germination by five frugivorous carnivores on a mammal-dispersed pioneer tree, the date-plum persimmon (Diospyros lotus), in a subtropical forest. Fecal analyses revealed that these carnivores acted as primary seed dispersers of D. lotus. We also observed that seed sizes were selected based on body mass and were species-specific, confirming the “gape limitation” hypothesis; three small carnivores (the masked palm civet Paguma larvata, yellow-throated marten Martes flavigula, and Chinese ferret-badger Melogale moschata) significantly preferred to disperse smaller seeds in comparison with control seeds obtained directly from wild plants whereas the largest Asiatic black bears (Ursus thibetanus) ingested larger seeds. Seeds dispersed by medium-sized hog badgers (Arctonyx albogularis) were not significantly different from control seeds. However, regarding the influence of gut passage on seed germination, three arboreal dispersal agents (martens, civets, and bears) enhanced germination success whereas terrestrial species (ferret-badgers and hog badgers) inhibited the germination process compared with undigested control seeds. These conflicting selection pressures on seed size and germination may enhance the heterogeneity of germination dynamics and thus increase species fitness through diversification of the regeneration niche. Our results advance our understanding of seed dispersal mechanisms and have important implications for forest recruitment and ecosystem dynamics.     

Endozoochorous seed dispersal by golden snub-nosed monkeys in a temperate forest

Seed dispersal is essential for plant recruitment and the maintenance of biodiversity. Colobine monkeys are primarily folivorous, but they also consume fruits and are often assumed to be seed predators. Although they are known to be epizoochorous seed dispersers, their role as endozoochorous seed dispersers needs reassessment. We examined potential endozoochory in golden snub-nosed monkeys (Rhinopithecus roxellana) at Dalongtan in Shennongjia National Park, central China, by assessing potential germination of ingested seeds (n = 1806, 9 species) from fecal samples. Intact seeds were in almost all fecal samples (ranging from 5–130 seeds), and ingested seeds were from small seeded species (seed width <4.5 mm). The 2 most abundant species were Actinidia arguta (73%) and Rosa caudata (15%). The fruits of A. arguta were unripe when ingested (i.e. effective seed predation) and the ingested seeds did not germinate in the trials. Therefore, ingestion of unripe seeds does not lead to effective seed dispersal. However, germination rates of defecated R. caudata (9%) were greater than control seeds (6% and 0%), demonstrating potential endozoochorous seed dispersal. Thus, colobine monkeys do indeed disperse mainly small-seeded from multi-seeded fruits through potential endozoochory and this process enhances the recruitment of seedlings.     

Inter‐specific and intra‐specific variability in fruit color preference in two species of Turdus

One of the main hypotheses proposed to explain the evolution of fruit color deals with a preference of avian frugivores for specific colors, mainly black and red, which are the most common fruit colors in many of the studied habitats. I analyzed fruit color preferences by wild birds belonging to 2 species of the highly frugivorous genus Turdus (Eurasian Blackbird Turdus merula Linnaeus, 1758 and Redwing Turdus iliacus Linnaeus, 1758) by means of captivity experiments with artificial fruits. Despite important within‐individual (i.e. temporal) and among‐individual variability, consistent patterns of species‐specific color preferences emerged. Eurasian Blackbirds tended to prefer red over blue, green and black, whereas Redwings seemed to prefer black over the rest. Green was systematically avoided by both species, suggesting that it might signal unripeness of fruits. Both preferred colors have been previously reported as the most common among fleshy‐fruited plants. The high variability, both within and between individuals, in preferences suggests that they can be subject to changes through experience and learning and, therefore, are not likely to drive the evolution of fruit color. The main differences between both species could be related to the most common fruit color they fed upon during the last months before capture.     

Digestive efficiency of indigenous and invasive avian species fed fruit of invasive alien plants in South Africa

Many highly invasive plant species produce fleshy fruit that are consumed and dispersed by frugivorous birds. However, little is known about assimilation efficiency of invasive fruit by indigenous and invasive avian species. We investigated whether indigenous Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos and invasive alien Rose-ringed Parakeets (Psittacula krameri) met their energy demands when fed fruits of four fleshy- fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava and Morus alba. Birds were fed single-fruit diets for two consecutive days and energetic parameters were calculated for all fruit diets. Our results showed that generally both invasive and indigenous avian species managed to gain their daily energy requirements from fruits of the four respective invasive plants, suggesting that they can meet their energetic demands by feeding on them only. The exception was P. krameri, which did not feed on S. mauritianum fruit. These findings may explain why fruits of invasive alien plants are attractive to most avian frugivores and highlight the role of avian frugivores in their dispersal.     

Dispersal of invasive Phytolacca americana seeds by birds in an urban garden in China

Although seed dispersal is a key process determining the regeneration and spread of invasive plant populations, few studies have explicitly addressed the link between dispersal vector behavior and seedling recruitment to gain insight into the invasion process within an urban garden context. We evaluated the role of bird vectors in the dispersal of pokeweed (Phytolacca americana), a North American herb that is invasive in urban gardens in China. Fruiting P. americana attracted both generalist and specialist bird species that fed on and dispersed its seeds. The generalist species Pycnonotus sinensis and Urocissa erythrorhyncha were the most frequent dispersers. Seedling numbers of P. americana were strongly associated with the perching behavior of frugivorous birds. If newly recruited bird species use seedling‐safe perching sites, the P. americana will regenerate faster, which would enhance its invasive potential. Based on our observations, we conclude that the 2 main bird vectors, P. sinensis and U. erythrorhyncha, provide potential effective dispersal agents for P. americana. Our results highlight the role of native birds in seed dispersal of invasive plants in urban gardens.     

Scatter‐hoarding rodents as secondary seed dispersers of a frugivore‐dispersed tree Scleropyrum wallichianum in a defaunated Xishuangbanna tropical forest,China

Local extinction or population decline of large frugivorous vertebrates as primary seed dispersers, caused by human disturbance and habitat change, might lead to dispersal limitation of many large‐seeded fruit trees. However, it is not known whether or not scatter‐hoarding rodents as secondary seed dispersers can help maintain natural regeneration (e.g. seed dispersal) of these frugivore‐dispersed trees in the face of the functional reduction or loss of primary seed dispersers. In the present study, we investigated how scatter‐hoarding rodents affect the fate of tagged seeds of a large‐seeded fruit tree (Scleropyrum wallichianum Arnott, 1838, Santalaceae) from seed fall to seedling establishment in a heavily defaunated tropical forest in the Xishuangbanna region of Yunnan Province, in southwest China, in 2007 and 2008. Our results show that: (i) rodents removed nearly all S. wallichianum seeds in both years; (ii) a large proportion (2007, 75%; 2008, 67.5%) of the tagged seeds were cached individually in the surface soil or under leaf litters; (iii) dispersal distance of primary caches was further in 2007 (19.6 ± 14.6 m) than that in 2008 (14.1 ± 11.6 m), and distance increased as rodents recovered and moved seeds from primary caches into subsequent caching sites; and (iv) part of the cached seeds (2007, 3.2%; 2008, 2%) survived to the seedling stage each year. Our study suggests that by taking roles of both primary and secondary seed dispersers, scatter‐hoarding rodents can play a significant role in maintaining seedling establishment of S. wallichianum, and are able to at least partly compensate for the loss of large frugivorous vertebrates in seed dispersal.     

Fruit availability,frugivore satiation and seed removal in 2 primate‐dispersed tree species

During a mast‐fruiting event we investigated spatial variability in fruit availability, consumption, and seed removal at two sympatric tree species, Manilkara bidentata and M. huberi (Sapotaceae) at Nouragues Natural Reserve, French Guiana. We addressed the question of how Manilkara density and fruits at the community level might be major causes of variability in feeding assemblages between tree species. We thus explored how the frugivore assemblages differed between forest patches with contrasting relative Manilkara density and fruiting context. During the daytime, Alouatta seniculus was more often observed in M. huberi crowns at Petit Plateau (PP) with the greatest density of Manilkara spp. and the lowest fruit diversity and availability, whereas Cebus apella and Saguinus midas were more often observed in M. bidentata crowns at both Grand Plateau (GP), with a lowest density of M. bidentata and overall greater fruit supply, and PP. Overall, nearly 53% and 15% of the M. bidentata seed crop at GP and PP, respectively, and about 47% of the M. huberi seed crop were removed, otherwise either spit out or defecated beneath trees, or dropped in fruits. Small‐bodied primates concentrated fallen seeds beneath parent trees while large‐bodied primate species removed and dispersed more seeds away from parents. However, among the latter, satiated A. seniculus wasted seeds under conspecific trees at PP. Variations in feeding assemblages, seed removal rates and fates possibly reflected interactions with extra‐generic fruit species at the community level, according to feeding choice, habitat preferences and ranging patterns of primate species.     

甘南地区歪头菜的选择性败育及结实格局

歪头菜是甘南地区极具利用价值的饲用植物,可为家畜提供丰富的蛋白质,因此加强种子生产是歪头菜在该地区种植推广的基础。本实验着眼于歪头菜生殖过程中的选择性败育,研究了歪头菜花期不同阶段和花序不同位置果实和种子的结实格局,得出以下结果:1)2龄植株盛花期花序上结荚率最高(41.6%),5龄植株初花期花序上结荚率最高(28.8%),两者均为末花期花序上结荚率最低,且所结荚果内种子数为0。2)2龄和5龄植株均为花序中部结荚率最高,分别为43.9%和41.6%,但上、中、下部位荚果内的种子数无显著(P>0.05)差异。3)荚果内靠近柱头端和靠近小花柄端的胚珠败育的可能性更大,荚果中部(从柱头端算起第2,3,4,5位置)的胚珠形成种子时更易出现交替败育的趋势。4)每序结荚数随着每序单花数的增加呈现先增加后减少的趋势,当每序单花数为20朵时,每序结荚数达到最大8个。由上述结果推测,选择性败育引起的歪头菜果实和种子的结实分配格局可能是资源限制的原因,也可能是植物对特殊生境的一种繁殖策略,然而这一结果影响了歪头菜的实际种子产量。     

Importance of bird traits for seed dispersal patterns of co‐fruiting trees in a patchy forest

Habitat fragmentation is globally one of the most important drivers of change in biodiversity. Seed dispersal by birds is crucial for tree regeneration in remnant patchy forests, yet how bird traits affect seed dispersal pattern is still poorly understood. We studied the extent to which bird traits affect seed‐removal networks and whether these traits affect seed deposition and seedling recruitment for 3 co‐fruiting tree species (Taxus chinensis, Cinnamomum bodinieri and Machilus thunbergii) in a patchy forest. A total of 17, 18 and 10 bird species were recorded foraging for seeds of T. chinensis, M. thunbergii and C. bodinieri, respectively. Frequency of bird visitation increased with tail length, wing length and body length. Furthermore, bird body length, bill length, body weight and wing length were important in the strength of the seed removal network. During foraging, 6 bird species exhibited different patterns of microhabitat utilization and their perching frequency increased with bird weight and tarsus length. As a consequence, frequency of habitat use, bird length and tarsus length were important in determining the number of deposited seeds. For seedling recruitment, seedling number increased with bird tarsus length and weight, but decreased with wing length. Overall, our results showed that various bird traits not only affected seed removal, but also influenced the subsequent processes of seed deposition and seedling distribution in a patchy forest. These results thus highlight the importance of large‐bodied birds for plant recruitment and point out the need to prioritize the protection and conservation of these birds in remnant patchy forests.     

Internal dispersal of seed‐inhabiting insects by vertebrate frugivores: a review and prospects

The finding that some seed‐inhabiting insects can survive passage through the entire digestive tract of seed‐dispersing vertebrates is relatively recent, but evidence suggests that it does occur. Here, I document this phenomenon, discuss its qualitative and quantitative dimensions, and offer suggestions for further research. The few documented cases that I review include plant species belonging to different families, with varied fleshy fruit types, number of seeds per fruit and seed size. The vertebrate frugivores involved include passerines that feed on relatively small fruits, and galliforms, and perissodactyls and primates that feed on larger fruits. The seed‐inhabiting insects involved are the larvae of seed‐infesting wasps, parasitoid wasps and seed‐infesting beetles. The phenomenon has been verified in open, rural ecosystems in North America and Southern Europe, and in tropical and subtropical forests in South America. These varied scenarios suggest that the qualitative dimension of the phenomenon is considerably greater than known thus far. A simple method for detecting new events is proposed. However, research must also focus on the identity and biology of seed‐feeding insects of wild fleshy fruits and their parasitoids. High survival rates of seed‐inhabiting insects after vertebrate gut passage are predominant. This phenomenon generally appears to favor insect dispersal.     

Galápagos land iguana (Conolophus subcristatus) as a seed disperser

The role of the most common land iguana (Conolophus subcristatus) in the Galápagos Islands as an effective seed disperser is explored in this study. A total of 5705 seeds of 32 plant species were identified from 160 scats, 4545 of which (80%) appeared visually undamaged. Germination trials of 849 seeds from 29 species revealed that at least 10 species remained viable after passing through the iguana's gut, although only a small proportion of those seeds (4%) germinated. In any case, we argue that C. subcristatus exerts an important role on the 7 Galapagos islands where it occurs because of its abundance and capacity to ingest and disperse seeds at long distances. Our results strongly suggest that the Galápagos C. subcristatus plays an important role as a seed disperser of not only of native species but also some introduced plants in the Galápagos Islands.     

无籽刺梨果实生长发育的解剖结构观察

本文以贵州无籽刺梨果实为材料,对果实发育进程中的形态和显微结构特征进行测定和观察,旨在为揭示无籽刺梨果实发育的机制提供参考。结果表明,无籽刺梨果实生长发育可分为4个阶段,即阶段1 (S1)、阶段2 (S2)、阶段3 (S3)和阶段4 (S4)。在S1阶段,果实细胞经历快速分裂,维管束木质化程度低,韧皮部比较发达,部分薄壁细胞中储存淀粉粒,未观察到石细胞;随后在S2阶段细胞再次分裂,维管束部分木质化,石细胞出现,此阶段含大量淀粉粒;在S3阶段,细胞膨大,维管束发达,石细胞含量增多,淀粉粒减少;最后在S4阶段,细胞间隙变大,维管束可见度降低,淀粉粒完全消失,石细胞含量降低,果实达到生理成熟。无籽刺梨败育种子未观察到胚和胚乳,且种皮以内的内部系统皱缩且胚柄系统断裂。无籽刺梨子房壁直接发育而成的果皮特化为三个组织层,即外果皮、中果皮和内果皮,果实在S1阶段快速生长,在S2阶段缓慢生长,S3阶段快速生长,S4阶段缓慢生长,整个果实生长发育呈双S型曲线生长模式。无籽刺梨未授粉的胚珠发育中止,导致种子败育。     

Bird habitat preferences drive hemoparasite infection in the Neotropical region

The role that the environment plays in vector-borne parasite infection is one of the central factors for understanding disease dynamics. We assessed how Neotropical bird foraging strata and habitat preferences determine infection by parasites of the genera Haemoproteus, Plasmodium, Leucocytozoon, and Trypanosoma and filarioids, and tested for phylogenetic signal in these host–parasite associations. We performed extensive searches of the scientific literature and created a database of hemoparasite surveys. We collected data on host body mass, foraging strata, habitat preference, and migratory status, and tested if host ecological traits predict each hemoparasite occurrence and prevalence using a phylogenetic Bayesian framework. Species of Plasmodium tend to infect birds from tropical forests while birds from altitudinal environments are likely to be infected by species of Leucocytozoon. The probability of a bird being infected by filarioid or Trypanosoma is higher in lowland forests. Bird species that occur in anthropic environments and dry habitats of tropical latitudes are more susceptible to infection by species of Haemoproteus. Host foraging strata is also influential and bird species that forage in the mid-high and canopy strata are more prone to infection by species of Haemoproteus and filarioids. We also identified phylogenetic signal for host–parasite associations with the probability of infection of Neotropical birds by any hemoparasite being more similar among more closely related species. We provided a useful framework to identify environments that correlate with hemoparasite infection, which is also helpful for detecting areas with potential suitability for hemoparasite infection due to land conversion and climate change.     

草食动物对植物种子的消化道传播研究进展

在Janzen提出“双F假说”之后,草食动物对植物种子的消化道传播就被广泛接受并做了大量的研究工作。草食动物对种子的消化道传播受到诸多因素的影响,这些影响因素概括起来包括4个方面,植物种子自身的结构特点(诸如种子大小形状、种子种皮结构、种子的休眠特征等),动物消化道特征,日粮结构,粪便物理状态。由于这些因素主要包括的植物种子和动物两方面,因此就派生出草食动物植物种子之间是否存在协同进化这一问题。笔者从草食动物消化道传播的理论基础、影响种子消化道传播的主要因素以及草食动物和植物之间在种子消化道传播中是否存在协同进化进行了系统综述,对近年来相关研究进行了总结,提出了在今后有关植物种子消化道传播研究中需要关注的热点。     

Onto the sense of smell in macaws,amazons and toucans: can they use volatile cues of fruits to make foraging decisions?

Over the past decades, empirical evidence has been accumulated indicating that olfactory information plays a fundamental role in bird life history. Nonetheless, many aspects of avian olfaction remain poorly understood. Our purpose was to broaden the knowledge about the importance of the sense of smell in some neglected bird groups: psittaciformes and ramphastids, and to compare how the response varied between the species. Because of the lack of information about the use of chemical cues for locating food in fruit-eating species, we also aimed to delve into this question. We conducted a 3-choice (water/vinegar/papaya and banana juice) scent test in 5 Costa Rican native species: scarlet macaw (Ara macao), red-lored amazon (Amazona autumnalis), yellow-naped amazon (Amazona auropalliata), keel-billed toucan (Ramphastos sulfuratus), and yellow-throated toucan (Ramphastos ambiguus). Results revealed that macaws and toucans allocated significantly more time to interacting with the fruit scent container, indicating that these species can perceive the volatile chemicals emitted by ripe fruits and that they can use this information to make foraging decisions. However, amazons did not dedicate more time to interact with the fruit treatment. Our research provides the first evidence of the ability to exploit chemical volatile cues in macaws and toucans.     

Plant‐frugivore interactions in an intact tropical forest in north‐east Thailand

Fleshy‐fruited plants in tropical forests largely rely on vertebrate frugivores to disperse their seeds. Although this plant–animal interaction is typically considered a diffuse mutualism, it is fundamental as it provides the template on which tropical forest communities are structured. We applied a mutualistic network approach to investigate the relationship between small‐fruited fleshy plant species and the fruit‐eating bird community in an intact evergreen forest in northeast Thailand. A minimum of 53 bird species consumed fruits of 136 plant species. Plant‐avian frugivore networks were highly asymmetrical, with observed networks filling 30% of all potential links. Whereas some of the missing links in the present study might be due to undersampling, forbidden links can be attributed to size constraints, accessibility and phenological uncoupling, and although the majority of missing links were unknown (58.2%), many were probably due to a given bird species being either rare or only a very occasional fruit eater. The most common frugivores were bulbuls, barbets and fairy‐bluebirds, which were responsible for the majority of fruit removal from small fleshy fruited species in our system. Migratory birds seemed to be a minor component of the plant‐frugivore networks, accounting for only 3% of feeding visits to fruiting trees; they filled 2% of the overall potential networks. The majority of interactions were generalized unspecific; however, Saurauia roxburghii Wall. appeared to be dependent on flowerpeckers for dispersal, while Thick‐billed Pigeons were only seen to eat figs.     

Seed handling by primary frugivores differentially influence post‐dispersal seed removal of Chinese yew by ground‐dwelling animals

Seed handling by primary frugivores can influence secondary dispersal and/or predation of post‐dispersal seeds by attracting different guilds of ground‐dwelling animals. Many studies have focused on seeds embedded in feces of mammals or birds; however, less is known about how ground‐dwelling animals treat seeds regurgitated by birds (without pulp and not embedded in feces). To compare the effect of differential seed handling by primary dispersers on secondary seed removal of Chinese yew (Taxus chinensis var. mairei), we conducted a series of exclosure experiments to determine the relative impact of animals on the removal of defecated seeds (handled by masked palm civet), regurgitated seeds (handled by birds) and intact fruits. All types of yew seeds were consistently removed at a higher rate by rodents than by ants. Regurgitated seeds had the highest removal percentage and were only removed by rodents. These seeds were probably eaten in situ without being secondarily dispersed. Defecated seeds were removed by both rodents and ants; only ants might act as secondary dispersers of defecated seeds, whereas rodents ate most of them. We inferred that seeds regurgitated by birds were subjected to the highest rates of predation, whereas those dispersed in the feces of masked palm civets probably had a higher likelihood of secondary dispersal. Seeds from feces attracted ants, which were likely to transport seeds and potentially provided a means by which the seeds could escape predation by rodents. Our study highlighted that primary dispersal by birds might not always facilitate secondary dispersal and establishment of plant populations.     

Efficacy of Hydrogen Peroxide to Control Parasitic Infestations on Hatchery-Reared Fish

Abstract

The efficacy of hydrogen peroxide to control external parasitic infestations on juvenile (10–33-g) rainbow trout Oncorhynchus mykiss was evaluated in three clinical field trials. Fish were exposed to hydrogen peroxide concentrations ranging from 0 to 560 mg/L for 30 min once every other day for a total of three treatments. Pre- and posttreatment skin scrapes and gill wet mounts of test fish were microscopically examined to identify and enumerate external parasites. Infestation severity was classified as nonexistent (0 organisms), low (1–10 organisms), moderate (11–20 organisms), or high (?21 organisms). In trial 1, pretreatment skin examinations revealed a severe infestation of the protozoan Ambiphrya on all fish examined. Posttreatment skin examinations conducted within 24 h of the last treatment indicated that all hydrogen peroxide treatments eliminated Ambiphrya, whereas control fish remained severely infested with the protozoan. In trial 2, pretreatment examinations of skin and gill samples indicated a high infestation of the trematode Gyrodactylus (skin) and the protozoan Trichodina (gills) on all fish. Posttreatment examinations conducted within 24 h of the last treatment indicated that Gyrodactylus was eliminated from the skin of all treated fish; however, the high infestation of Trichodina remained on the gills of the test fish. All control fish had high infestation levels of both parasites. A high infestation of Ambiphrya was found on the skin of test fish before treatment (trial 3). Posttreatment examinations conducted 14 d after the last treatment revealed that 56% of the fish were parasite free, whereas the remaining test fish had low infestation levels. Control fish remained severely infested with the parasite. Based on the efficacy data, all hydrogen peroxide treatment regimens were efficacious in the control of Ambiphrya and Gyrodactylus.