Single Fish Research Articles

612 A single FISH procedure for the detection of tumor cells: Bladder cancer as model

612 A single FISH procedure for the detection of tumor cells: Bladder cancer as model

A combined RT-PCR and dot-blot hybridization method reveals the coexistence of SJNNV and RGNNV betanodavirus genotypes in wild meagre (Argyrosomus regius)

To detect the possible coexistence of striped jack nervous necrosis virus (SJNNV) and red-spotted grouper nervous necrosis virus (RGNNV) genotypes in a single fish, a methodology based on the combination of PCR amplification and blot hybridization has been developed and applied in this study. The degenerate primers designed for the PCR procedure target the T4 region within the capsid gene, resulting in the amplification of both genotypes. The subsequent hybridization of these amplification products with two different specific digoxigenin-labelled probes resulted in the identification of both genotypes separately. The application of the RT-PCR protocol to analyse blood samples from asymptomatic wild meagre (Argyrosomus regius) specimens has shown a 46.87% of viral nervous necrosis virus carriers. The combination of RT-PCR and blot hybridization increases the detection rate up to 90.62%, and, in addition, it has shown the coexistence of both genotypes in 18 out of the 32 specimens analysed (56.25%). This study reports the coexistence of betanodaviruses belonging to two different genotypes (SJNNV and RGNNV) in wild fish specimens. This is the first report demonstrating the presence of SJNNV and RGNNV genotypes in the same specimen. This study also demonstrates a carrier state in this fish species for the first time.

Distribution history of non-native freshwater fish species in Germany: how invasive are they?

Distribution patterns of non-native fishes in Germany have been analysed starting from their first introductions reported, with the objectives to determine indicators of their invasiveness, to identify the most important distribution pathways, and to predict their further development. In Germany, 14 out of 93 non-native freshwater and migratory fish species ever registered are established today, a further six are possibly established, eight have failed to establish, and the rest were single records. Five of the established and three potentially established species were restricted to single locations. Of the remaining species, only the gobiid species are actually spreading throughout the waterway network, whereas other stocks rather tend to decline or did not change. The most wide-spread species is rainbow trout Oncorhynchus mykiss, with 5,872 records in open waters being the most important fish for German’s commercial inland fisheries with an annual yield of > 21 000 tons. But rainbow trout is widely stocked and its establishment status is a subject of debate. Inland fisheries management has contributed most to the recent distribution of non-native fishes, but it became also the best regulated pathway. Therefore, it is expected that ornamental fish trade and aquaculture will become most important for introducing new non-native fishes in the near future, even if unintentionally. Every single fish escaping from a garden pond or holding facility is a potential founder of an invasive species stock and in particular raising water temperatures in winter might promote the establishment of ornamental fish. Once established, there are nearly no legal means to remove a non-native species successfully from a water body.

Functional Diversification and Evolution of Antifreeze Proteins in the Antarctic Fish Lycodichthys dearborni

Antifreeze proteins (AFPs) have independently evolved in many organisms. AFPs act by binding to ice crystals, effectively lowering the freezing point. AFPs are often at high copy number in a genome and diversity exists between copies. Type III antifreeze proteins are found in Arctic and Antarctic eel pouts, and have previously been shown to evolve under positive selection. Here we combine molecular and proteomic techniques to understand the molecular evolution and diversity of Type III antifreeze proteins in a single individual Antarctic fish Lycodichthys dearborni. Our expressed sequence tag (EST) screen reveals that at least seven different AFP variants are transcribed, which are ultimately translated into five different protein isoforms. The isoforms have identical 66 base pair signal sequences and different numbers of subsequent ice-binding domains followed by a stop codon. Isoforms with one ice-binding unit (monomer), two units (dimer), and multiple units (multimer) were present in the EST library. We identify a previously uncharacterized protein dimer, providing further evidence that there is diversity between Type III AFP isoforms, perhaps driven by positive selection for greater thermal hysteresis. Proteomic analysis confirms that several of these isoforms are translated and present in the liver. Our molecular evolution study shows that paralogs have diverged under positive selection. We hypothesize that antifreeze protein diversity is an important contributor to depressing the serum freezing point.

Low cost fish feed for aquarium fish: a test case using Colisa fasciata

A comprehensive trial was undertaken to assess the effect of various types of feed on biomass conversion rate as well as on gonad (ovarian) weight in Colisa fasciata, a dual-purpose fish for food and ornamental use. Three groups of juvenile fish (3.0±0.015 g; 10.00±0.75 mm) were fed with three different types of feed: dried earthworm feed, laboratory prepared feed (LPF) and market feed. The LPF made with dried earthworm powder, eggshell powder and plant rhizome (Commelina sp.) dusts proved to be the best and economical feed among the three feed tested. The LPF also increased gonad weight of the cultured fishes indicating a production of more fish offspring’s from a single female fish. The plant rhizome possibly played a role in increasingly appetite among LPF cultured fish, which in turn influenced somatic as well as reproductive growth of those fish.

Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) portal of entry into the fish host

The portal of entry and the penetration process of the myxozoan parasite Tetracapsuloides bryosalmonae are still poorly understood. In the present study, spores of T. bryosalmonae derived from the bryozoan host (malacospores) were activated chemically and mechanically to investigate their reaction after attachment to the fish host in vitro. Amoeboid movement of both sporoplasms was shown for the first time. The morphology of malacospores was assessed using scanning electron microscopy (SEM). Openings of the polar capsules and released polar filaments were visible. One sporoplasm was observed leaving the spore shell. Laboratory exposure experiments of juvenile rainbow trout Oncorhynchus mykiss to spores of T. bryosalmonae were also conducted. Single fish were incubated with 1000 to 2000 spores in 100 ml of water for 5 to 60 min. Immunohistochemically stained sections of skin and gills were examined using light microscopy, as well as ultra thin sections using transmission electron microscopy (TEM), to investigate attachment and early penetration. Whole fish and excised gills of fish exposed to a spore suspension were fixed and prepared for scanning electron microscopy. Attached and penetrating stages were found only on or in the gills, and not in the skin. Due to the low overall number of spores, only a few spores were found adjacent to the gill epithelium in TEM. No parasite stages were found on the samples used for SEM. These results indicate that the gills are the preferred entry loci for the amoeboid sporoplasms of T. bryosalmonae into the fish host.

A novel method for investigating the collective behaviour of fish: introducing ‘Robofish’

Collective animal behaviour has attracted much attention recently, but cause-and-effect within interaction sequences has often been difficult to establish. To tackle this problem, we constructed a robotic fish (‘Robofish’) with which three-spined sticklebacks (Gasterosteus aculeatus L.) interact. Robofish is a computer-controlled replica stickleback that can be programmed to move around a tank. First, we demonstrated the functioning of the method: that the sticklebacks interacted with Robofish. We examined two types of interaction: recruitment and leadership. We found that Robofish could recruit a single fish from a refuge and could initiate a turn in singletons and in groups of ten, i.e. act as a leader. We also showed that the influence of Robofish diminished after the first 30 min that fish spent in a new environment. Second, using this method, we investigated the effects of metric and topological inter-individual distance on the influence that Robofish had on the orientation of fish in a shoal of ten. We found that inter-individual interactions during this turn were predominantly mediated by topological, rather than metric, distance. Finally, we discussed the potential of this novel method and the importance of our findings for the study of collective animal behaviour.

Scientific Opinion on marine biotoxins in shellfish – Emerging toxins: Ciguatoxin group

The EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) assessed the risks to human health related to the consumption of ciguatoxin (CTX)-group toxins in fish. CTX-group toxins occur in fish as a result of biotransformation of precursor gambiertoxins produced by the benthic dinoflagellate Gambierdiscus toxicus. CTX-group toxins cause ciguatera fish poisoning. They are mainly found in Pacific, Caribbean and Indian Ocean regions and are classified as Pacific (P), Caribbean (C) and Indian Ocean (I) CTX-group toxins. Recently CTX-group toxins were identified for the first time in fish in Europe. Currently there are no regulatory limits for CTX-group toxins in fish in Europe, but the regulation requires that no fish products containing CTX-group toxins are placed on the market. The toxicological database for CTX-group toxins is limited, comprising mostly acute toxicity studies. In view of the acute toxicity of CTX-group toxins the CONTAM Panel considered establishing an acute reference dose (ARfD). However, due to the very limited quantitative data both in experimental animals as well as related to human intoxications, the CONTAM Panel concluded that the establishment of an oral ARfD was not possible. Based on case reports on human intoxications it appears that a concentration of 0.01 μg P CTX-1 equivalents/kg fish is expected not to exert effects in sensitive individuals when consuming a single fish meal. The mouse bioassay (MBA) has been widely used to detect CTX-group toxins. However, due to insufficient detection capability and ethical concerns the MBA is not considered an appropriate method. In vitro (cytotoxicity and receptor binding) assays have been developed as alternative, but they need further development. Liquid chromatography-tandem mass spectrometry methods can be of value for the quantification of CTX-group toxins, but certified reference standards and reference materials need to be provided to allow method development and (inter-laboratory) validation.

Mineral fish: their morphological classification, usefulness as shear sense indicators and genesis

Mineral fish are sheared and commonly asymmetric mineral grains or clusters of grains. This work reports 11 sub-types of mineral fish showing a top-to-SE sense of ductile shearing in the Karakoram Metamorphic Complex (KMC). The mineral fish are of three broad geometries: sigmoid, lenticular and parallelogram. Reliable senses of shear are indicated by the overall asymmetry and inclination of mineral fish. On the other hand, the true shear sense is not always indicated by either the orientations of their cleavage planes or those of the individual grains in composite mineral fish. The ranges of local orientations of single sigmoid mineral fish that include the lower values (<23°) in the KMC indicate their extensive ductile shearing. The studied mineral fish were products of a range of deformation mechanisms including homogeneous deformation, simple shear, intra-granular slip, crystal-plastic deformation, fracturing and synthetic shearing. Additionally, some examples might have undergone duplex slips and a few nucleated and grew either prior to or during the top-to-SE shearing.

Fish-Borne Zoonotic Trematodes in Cultured and Wild-Caught Freshwater Fish from the Red River Delta, Vietnam

Nam Dinh province in Red River Delta, Vietnam, is an endemic area for the human liver fluke Clonorchis sinensis, but little is known about its occurrence in the fish intermediate host in this region. A cross-sectional study was carried out to identify fish-borne zoonotic trematodes (FZT) species diversity and to estimate the prevalence and infection densities of FZT in three major types of fish: cultured species and self-recruiting species from family ponds and wild-caught species from irrigation canals in Nam Dinh province. A total of 714 wild-caught fish from canals and 829 fish from family ponds were examined for FZT infection. Only a single fish from a pond was infected with Cl. sinensis. The intestinal fluke Haplorchis pumilio was very common and found in more than 50% of fish irrespective of origin. Four other intestinal FZT species were found at low prevalence (<4.0%) except Procerovum varium, which was found in 14.4% of wild-caught fish. There was no significant difference (p > 0.05) in FZT prevalence in cultured fish (64.3%) compared with wild-caught fish (68.9%), nor between cultured fish species (65.1%) and self-recruiting species obtained from ponds (58.1%). The prevalence of FZT in silver carp (Hypophthalmichthys molitrix) (82.7%), grass carp (Ctenopharyngodon idellus) (76.9%), and mrigal (Cirrhinus mrigala) (63.8%) was significantly higher than that in rohu (Labeo rohita) (49.1%) (p < 0.001). The density of FZT metacercariae in fish from canals (0.56 metacercariae/g) was significantly higher (p < 0.001) than that in fish from ponds (0.03 metacercariae/g). The frequent occurrence of intestinal flukes in all fish types indicates that wild-caught and cultured fish are equally at risk of infection with FZT, particularly in species commonly used in Nam Dinh to prepare raw fish dishes. These results underscore the need for greater awareness of the risk from raw fish dishes among public health agencies and consumers.

Spatial ecology of adult muskellunge (Esox masquinongy) in the urban Ottawa reach of the historic Rideau Canal, Canada

The Rideau Canal in Canada was constructed in the 1800s to enable strategic military and commercial transport in eastern Ontario between Lake Ontario and the Ottawa River. Today, the Rideau Canal is managed by Parks Canada and remains an engineered ecosystem, particularly in the urban Ottawa reach (7 km long) where it is largely channelized and is partially drained during the winter to protect canal infrastructure (i.e., locks) and provide recreational opportunities (i.e., skating). Interestingly, the Ottawa reach of the Rideau Canal supports one of the few wild urban muskellunge (Esox masquinongy) fisheries in North America supported by natural reproduction. However, little is known about the spatial ecology, residency patterns or survival of this apex freshwater predator in urban environments or canal systems. Radio-telemetry was used to study adult (N = 10; total size range of 64 to 122 cm) muskellunge in the Ottawa reach of the Rideau Canal over a multiple year period. The seasonal movements and home range of muskellunge were greatest during spring corresponding with the period when water levels in the canal were raised and muskellunge were presumably seeking out suitable spawning habitats following ice-off. During the summer fish ranged throughout the entire 7 km urban reach of the canal and by early fall muskellunge moved to the deeper parts of the reach and became largely restricted to an embayment known as Dow's Lake prior to the lowering of the canal where they stayed for the entire winter. The same pattern of seasonal movements persisted across several years. None of the tagged muskellunge were stranded from the fall canal drainage. One fish emigrated from the urban reach of the canal during the study period, moving upstream through a lock to an exurban reach. In addition, a single tagged fish died from a winterkill event. Environmental influences such as seasonality and water depth (associated with canal operations) are believed to be the primary mechanisms contributing to habitat selection and movement patterns of muskellunge in this reach of the Rideau Canal. Data on the spatial ecology of muskellunge in the urban reaches of the Rideau Canal will inform management of this unique population of fish to ensure that the historic and ecological values are balanced to preserve this iconic Canadian natural heritage site and its biota.

Feeding ecology of the leaf fish Monocirrhus polyacanthus (Perciformes: Polycentridae) in a terra firme stream in the Brazilian Amazon

Monocirrhus polyacanthus (Polycentridae) is a remarkable leaf-mimicking fish that inhabits streams, lake and river margins along the Amazon basin. Despite its obvious predatory habits and being frequently present in the international aquarium trade, little is known about its diet under natural conditions. We examined 35 specimens of leaf fish (28.5-82.0 mm SL), of which 19 had food the stomach. Thirty-three preys were found in the stomach contents, 19 of which were measured (2.0-33.0 mm total length). Up to five preys were found in the stomach contents of a single leaf fish specimen. The diet of the leaf fish was constituted by fish (63.15% FO, n = 12) and invertebrates (36.3% FO, n = 4); fish and invertebrate preys occurred together in three stomachs (15.8% FO). Of the 33 prey found in the stomachs, 21 were fish and 12 invertebrates. Among the consumed prey fishes, Characiformes and Perciformes represented 76.1% and 14.2% respectively. Characidae was the most commonly recorded prey family, followed by Lebiasinidae. Invertebrates were represented by shrimps (Decapoda) and insects (Coleoptera, Hymenoptera, Ephemeroptera and Odonata). There was a positive relation between the size of the leaf fish specimens and of its consumed preys. The combination of leaf fish's visually effective body camouflage and the reduced activity of the characids at crepuscular hours probably allow the capture of such fast moving preys. The coiled position of the fishes found in the stomach of M. polyacanthus possibly allowed the accommodation of more than one prey simultaneously, which seems to be important for predators that consume proportionally large preys that are captured only occasionally.

Distribution and Prevalence of Glochidia-Infested Wild-Caught Fishes at a Muskingum River Site in Southeastern Ohio

ABSTRACT Wild-caught fishes were examined from the Muskingum River in southeastern Ohio for the prevalence of glochidial infestation. Weekly collections over a 24-hour period for one year yielded 22 fish species (2,097 individuals). Six species (27%) were infested with glochidia—channel catfish, freshwater drum, gizzard shad, orange-spotted sunfish, bluegill, and hybrid Morone. Infestations were found during the months of March through August, and no infested fish were found during the months of September through February. The month with the highest number of infested fish species was August, and the lowest number occurred in April. The percentage of all individuals infested with glochidia was very low, 2.5%, but was similar to that reported for other rivers and higher that reported for most lakes. The percentage of all fish species infested was lower than those reported for rivers but still greater than the results for lakes. The impounded study site seems to fall between a unregulated river and a lake in terms of its prevalence of infested fishes. The glochidia were over-dispersed in the host populations; 100% of the infested species had 50% or fewer of their individuals infested. The mussel faunal assemblage at the study site appeared to be driven primarily by the presence of a single fish, freshwater drum, and not by the relative abundance of the fish species available.

Too close for comfort: a fishway exit and a hydro-power station inlet

A major environmental issue for hydro-electric power generation is passage of fish through turbines, or entrainment onto trash racks. At Yarrawonga Weir, on the upper Murray River in south-eastern Australia, the positioning of a fish lock resulted in the potential for upstream migrating fish to be swept back into the adjacent power station by cross flows. In 2004, a 4.5-m long steel extension flume was attached to the exit to alleviate this problem. To determine the fate of native fish after exiting the extension flume, 72 individuals (305–1015 mm long) were implanted with radio-transmitters and released into the fish lock exit channel. In 2004 (power station inflows 10 300 ML day–1), the majority of fish exited successfully (44 of 45) and only a single fish (2%) was entrained into the power station. In 2005 (power station inflows 12 000 ML day–1), fish again exited successfully (26 of 27) but with a higher proportion entrained (5 of 27; 18%). This reduced success appeared to be related to strong transverse flows with high water velocities adjacent to the fish lock exit. The efficiency of fish passage at this site might be improved by altering water management strategies, integrating engineering and fish biology, and through field-testing of proposed solutions.

Contribution to the knowledge of the infection with Acanthocephala of a predatory Antarctic ice-fish Chaenocephalus aceratus

Contribution to the knowledge of the infection with Acanthocephala of a predatory Antarctic ice-fish Chaenocephalus aceratus Adult females of a predatory fish, the blackfin icefish, Chaenocephalus aceratus examined at the South Shetland Islands and South Orkney Islands were by several orders of magnitude more infected with Acanthocephala than the males and immature females. Such phenomenon has not been observed in the neritic zone at South Georgia. Cystacanths of Corynosoma hamanni and Corynosoma pseudohamanni were the dominant parasites in Admiralty Bay, whereas Corynosoma bullosum was the dominant in the open sea off the South Shetland Islands and South Georgia, and in the sub-coastal waters off the South Orkney Islands. However, the dominance of C. bullosum was observed in several hosts in Admiralty Bay and the co-dominance of C. bullosum, C. hamanni, and C. pseudohamanni in one mature female in the neritic zone at the South Shetland Islands. Probably, these fish previously lived in the open sea. Cystacanths of Corynosoma arctocephali and Corynosoma shackletoni occurred in the fish in Admiralty Bay and off South Georgia. The former parasite was present also off the South Orkney Islands. One cystacanth of Andracantha baylisi was found off South Georgia. Two echinorhynchids, Aspersentis megarhynchus and Metacanthocephalus dalmori, occurred in the alimentary tracts of the fish caught in Admiralty Bay and one specimen of Echinorhynchus petrotschenkoi off the South Shetland Islands. The highest infection, amounting to 816 acanthocephalans, was found in a mature female in Admiralty Bay. One cystacanth of C. hamanni occurred in a single immature fish caught in the sub-coastal area off Deception Island.

Suitability of Four Smoked Fish Species to Dermestes maculatue (De Geer) [Coleoptera: Dermestidae

The suitability of four smoked fish species. namely. the Trigger fish (Balistes capriscus Gmelin). Catfish (Synodontis sp.), African catfish (Clarias gariepinus Burchel), and Nile tilapia (Orcochromis niloticus Linnaeus), for hide beetle. Dermestes maculatus (De Geer). development was investigated in the laboratory over a 90-day period. Significant (P&lt;0.05) weight losses were recorded in the two multiple-choice and one no-choice tests with the highest weight loss (78.50±7.15 %) occurring in Synodontis sp. and the lowest weight loss (46.7±2.92 %) occurring in O. niloticus. Interactions between fish species and test methods were significant (P&lt;0.05). The number of D. maculatus which emerged when the pest had free movement from one fish jar to another jar was significantly (P&lt;0.05) higher compared with the test where the pest was confined to ajar containing a single fish species. Significantly higher number of adults developed on Clarias in the no-choice test.

Changes in the pattern of feeding of kokanee Oncorhynchus nerka from Lake Tolmachevskoe during the formation of its population

Analysis of the feeding of kokanee Oncorhynchus nerka from Lake Tolmachevskoe, which was relocated here from Lake Kronotskoe more than 20 years ago, was studied. Lake Kronotskoe is inhabited by two forms of kokanee that differ in the pattern of feeding (plankton-eaters and benthos-eaters) and some morphological characters. According to the number of rakers at the first gill arch, kokanee from Tolmachevskoe Lake corresponds to plankton-eaters from Kronotskoe Lake; however, in the target water body, only single fish and only in the autumn period feed on plankton. The bulk of feeding is comprised of larger organisms: in summer of insect imagines and in autumn of benthos. Feeding of large and small fish in different areas of the lake from July to September is characterized. The change in the lake ecosystem related to the construction of Tolmachevskaya Hydraulic Power Plant and the formation of the reservoir apparently affected the pattern of fish feeding from 2003 to 2007, the number of prey in stomachs and the stomach fullness index considerably decreased, and the proportion in the food bolus of nonfood items, mainly plant remains, drastically increased.

Discriminating zooplankton communities in lakes with brook trout (Salvelinus fontinalis) and in fishless lakes

Natural geographic barriers and escarpments inhibited the post-glacial colonization of many lakes by fish on the eastern Canadian Boreal Shield. Hence, fishless lakes containing freshwater communities that evolved without fish predation are commonly found on the Boreal Shield next to fish-present lakes. The aim of this study was thus to assess how different top-down control from fish or invertebrate predation structure zooplankton communities in eastern Canadian Boreal Shield lakes throughout the ice-free season. We examined zooplankton community characteristics using univariate indices such as abundance, richness (S), evenness (J'), diversity (H'), and multivariate species assemblages (Bray—Curtis dissimilarity) in 5 lakes with a single fish population, brook trout, Salvelinus fontinalis, and in 5 naturally fishless lakes throughout the ice-free season. The total abundance of zooplanktonic organisms was significantly higher in fishless lakes over the whole sampling period; this was related to the presence of small herbivorous species such as rotifers. Species assemblages of zooplankton were also significantly different between the 2 types of lakes throughout the season, principally due to the high abundance of rotifers and the scarcity of immature and mature daphnids in fishless lakes. Our results suggest that the low intensity of selective predation by brook trout on large herbivores and the heavy predation by Chaoborus americanus larvae on daphnids in fishless lakes appear to be the key factors for structuring the zooplankton community. Multivariate indicators identified patterns that were not revealed with the usual univariate indices, showing the importance of selecting appropriate indicators for the assessment of community structure.

Shoaling preferences and the effects of sex ratio on spawning and aggression in small laboratory populations of zebrafish (Danio rerio)

Owing to a lack of basic information on the biology of zebrafish (Danio rerio), lab managers must often base decisions regarding the care and use of this species on anecdotal information. In an effort to provide researchers with context-specific behavioral information, the authors evaluated shoaling and spawning behaviors in small groups of zebrafish. In each shoaling assay, a fish was given a choice to shoal with either a single fish or a group of three fish. Females preferred to shoal with a group of three individuals rather than with a single individual, regardless of the sex of the other fish. Males preferred groups of three males over single males but preferred single females to groups of three females. In spawning assays, zebrafish were placed in breeding tanks in one of three sex ratios (1 male:1 female; 3 males:1 female; 1 male:3 females). Reproductive efficiency did not differ among groups, but aggression (evaluated according to presence of shed scales) was more frequently observed in the male-dominated treatment group.

Longitudinal Mercury Monitoring within the Japanese and Korean Communities (United States): Implications for Exposure Determination and Public Health Protection

BackgroundEstimates of exposure to toxicants are predominantly obtained from single time-point data. Fish consumption guidance based on these data may be incomplete, as recommendations are unlikely to consider impact from factors such as intraindividual variability, seasonal differences in consumption behavior, and species consumed.Objectives/methodsWe studied populations of Korean (n = 108) and Japanese (n = 106) women living in the Puget Sound area in Washington State to estimate mercury exposure based on fish intake and hair Hg levels at two and three time points, respectively. Our goals were to examine changes in hair Hg levels, fish intake behavior, and Hg body burden over time; and to determine if data from multiple time points could improve guidance.Results/conclusionMore than 50 fish species were consumed, with eight species representing approximately three-fourths of fish consumed by the Japanese and 10 species representing approximately four-fifths of fish intake by the Koreans. Fish species responsible for most Hg intake did not change over time; < 10 species accounted for most of the Hg body burden in each population. Longitudinal variability of hair Hg levels changed slowly across the study period. Japanese with hair Hg levels > 1.2 ppm (mean, 2.2 ppm) consumed approximately 150% more fish than those with levels ≤ 1.2 ppm (mean, 0.7 ppm). However, because many participants consumed substantial amounts of fish while having hair-Hg levels ≤ 1.2 ppm, the nutritional benefits offered from fish consumption should be obtainable without exceeding the RfD. We observed a 100% difference in fish intake between open-ended and 2-week recall fish consumption surveys. Open-ended survey data better represent Hg intake as determined from hair Hg levels. Single time-point fish intake data appear to be adequate for deriving guidance, but caution is warranted, as study is required to determine the significance of the different outcomes observed using the two survey time frames.