The effect of the cleaner fish Labroides dimidiatus on the capsalid monogenean Benedenia lolo parasite of the labrid fish Hemigymnus melapterus

The cleaner fish Labroides dimidiatus affected the pigmented monogenean parasite Benedenia lolo on the fish Hemigymnus melapterus (Labridae) held in aquaria. The effect of cleaner fish varied with the size class of fish; only small fish [ a posteriori size class <11.5 cm standard length ( L _S)] exposed to cleaner fish had fewer monogeneans compared with fish not exposed to cleaner fish. The abundance of monogeneans on large fish ( a posteriori size class <11.5 cm L _S) was not affected by cleaner fish. The size-frequency distributions of monogeneans on both size-classes of H. melapterus were affected by cleaner fish. Fish exposed to cleaner fish had fewer large (>3 mm) and more small (<1 mm) monogeneans than fish not exposed to cleaner fish, suggesting cleaner fish selectively removed larger monogeneans. This difference was more pronounced on large fish. In the absence of cleaner fish, small fish had almost as many monogeneans as large fish; they also had more small monogeneans than the large fish, suggesting small fish were more vulnerable to infection by monogeneans than larger fish. This suggests that the cleaner fish L. dimidiatus has the potential to control benedeniine monogeneans on captive fish and highlights the importance of taking into account fish size in studies of the effect of cleaner fish on ectoparasites.     

Cleaner fish drives local fish diversity on coral reefs

Coral reefs are one of the most diverse habitats in the world, yet our understanding of the processes affecting their biodiversity is limited. At the local scale, cleaner fish are thought to have a disproportionate effect, in relation to their abundance and size, on the activity of many other fish species, but confirmation of this species' effect on local fish diversity has proved elusive. The cleaner fish Labroides dimidiatus has major effects on fish activity patterns and may indirectly affect fish demography through the removal of large numbers of parasites. Here we show that small reefs where L. dimidiatus had been experimentally excluded for 18 months had half the species diversity of fish and one-fourth the abundance of individuals. Only fish that move among reefs, however, were affected. These fish include large species that themselves can affect other reef organisms. In contrast, the distribution of resident fish was not affected by cleaner fish. Thus, many fish appear to choose reefs based on the presence of cleaner fish. Our findings indicate that a single small and not very abundant fish has a strong influence on the movement patterns, habitat choice, activity, and local diversity and abundance of a wide variety of reef fish species.     

Effect of the removal of cleaner fish on the abundance and species composition of reef fish

The ecological significance of cleaner fish on coral reefs was investigated. I removed all cleaner fish, Labroides dimidiatus, from eight small reefs, measured the subsequent effect on the abundance and species composition of all reef fish after 3 and 6 months, and compared it with eight control reefs with cleaner fish. The removal of cleaner fish had no detectable effect on the total abundance of fish on reefs and the total number of fish species at both times. Multivariate analysis by non-metric multidimensional scaling and ANOSIM pairwise tests based on 191 fish species revealed no effect of cleaners on the community structure of fish. Similar results were obtained using principal components analysis on subsets of the data using the 33 most common fish species and the 15 most abundant species (≥5 individuals per reef ) with both log10 (x + 1) transformed data and with fish numbers standardized for abundance. This study demonstrates that the removal of cleaner fish for 6 months did not result in fish suffering increased mortality nor in fish leaving reefs to seek cleaning elsewhere. Received: 28 October 1996 / Accepted: 7 February 1997     

Interactions of pelagic cnidarians and ctenophores with fish: a review

Medusae, siphonophores and ctenophores (here grouped as `pelagic coelenterates') interact with fish in several ways. Some interactions are detrimental to fish populations, such as predation by gelatinous species on pelagic eggs and larvae of fish, the potential competition for prey among pelagic coelenterates and fish larvae and zooplanktivorous fish species, and pelagic coelenterates serving as intermediate hosts for fish parasites. Other interactions are positive for fish, such as predation by fish on gelatinous species and commensal associations among fish and pelagic coelenterates. The interactions range from beneficial for the gelatinous species (food, parasite removal), to negative (predation on them). We review existing information and present new data on these topics. Although such interactions have been documented frequently, the significance to either fish or pelagic coelenterate populations is poorly understood. The effects of pelagic coelenterates on fish populations are of particular interest because of the great importance of fisheries to the global economy. As fishing pressures mount, it becomes increasingly important to understand how they may influence the balance between pelagic coelenterates and fish.     

Omnivory by Planktivores Stabilizes Plankton Dynamics, but May Either Promote or Reduce Algal Biomass

Classical models of phytoplankton–zooplankton interaction show that with nutrient enrichment such systems may abruptly shift from limit cycles to stable phytoplankton domination due to zooplankton predation by planktivorous fish. Such models assume that planktivorous fish eat only zooplankton, but there are various species of filter-feeding fish that may also feed on phytoplankton. Here, we extend these classical models to systematically explore the effects of omnivory by planktivorous fish. Our analysis indicates that if fish forage on phytoplankton in addition to zooplankton, the alternative attractors predicted by the classical models disappear for all realistic parameter settings, even if omnivorous fish have a strong preference for zooplankton. Our model also shows that the level of fish biomass above which zooplankton collapse should be higher when fish are omnivorous than when fish are zooplanktivorous. We also used the model to explore the potential effects of the now increasingly common practice of stocking lakes with filter-feeding fish to control cyanobacteria. Because omnivorous filter-feeding fish forage on phytoplankton as well as on the main grazers of phytoplankton, the net effect of such fish on the phytoplankton biomass is not obvious. Our model suggests that there may be a unimodal relationship between the biomass of omnivorous filter-feeding fish and the biomass of phytoplankton. This implies that to manage for reductions in phytoplankton biomass, heavy stocking or strong reduction of such fish is best.     

Measuring fish body condition with or without parasites: does it matter?

A fish body condition index was calculated twice for each individual fish, including or excluding parasite mass from fish body mass, and index values were compared to test the effects of parasite mass on measurement of body condition. Potential correlations between parasite load and the two alternative fish condition index values were tested to assess how parasite mass may influence the perception of the actual effects of parasitism on fish body condition. Helminth parasite mass was estimated in common bully Gobiomorphus cotidianus from four New Zealand lakes and used to assess the biasing effects of parasite mass on body condition indices. Results showed that the inclusion or exclusion of parasite mass from fish body mass in index calculations significantly influenced correlation patterns between parasite load and fish body condition indices. When parasite mass was included, there was a positive correlation between parasite load and fish body condition, seemingly indicating that fish in better condition supported higher parasite loads. When parasite mass was excluded, there was no correlation between parasite load and fish body condition, i.e. there was no detectable effect of helminth parasites on fish condition or fish condition on parasite load. Fish body condition tended to be overestimated when parasite mass was not accounted for; results showed a positive correlation between relative parasite mass and the degree to which individual fish condition was overestimated. Regardless of the actual effects of helminth parasites on fish condition, parasite mass contained within a fish should be taken into account when estimating fish condition. Parasite tissues are not host tissues and should not be included in fish mass when calculating a body condition index, especially when looking at potential effects of helminth infections on fish condition.     

Die großen Fische fressen die kleinen

Big fish eat little fish Interests in fisheries science concentrate nowadays rather on functional aspects of aquatic ecosystems and biological processes than on ways how to increase the yield of distinct fish stocks. Interactions between fishes, their prey organisms and predators as well as fishing activities became in the focus of attention. Latest findings show a surprisingly high foraging of fish on fish. Fish consumption by fish may even exceed the landings of the fishing fleet. In comparison fish consumption by aquatic mammals and birds is relatively small and to neglect mostly.     

我国过鱼设施建设需求、成果及存在的问题

本文首先阐述了水利水电工程对河流连通性的影响以及修建过鱼设施的对策,然后从河流破碎化程度和鱼类洄游习性的角度分析了国内建设过鱼设施的需求,介绍了国内建设过鱼设施的成果,最后提出了6点过鱼设施相关问题和建议:(1)利用多指标量化评价的方法,科学地确定过鱼对象;(2)以复杂流场为背景条件,贴合实际地推进鱼类上溯行为研究;(3)对过鱼设施加大资金投入,扩大设施规模,加大过鱼设施过水流量(至少应为河流流量的1%);(4)为鱼类下行、低水头水工建筑物引起的跌水河段建设过鱼设施;(5)扩大过鱼效果评估的覆盖面,提高监测时长和频率,提出有广泛适用性的监测评估方法;(6)栖息地修复、增殖放流、生态调度、分层取水等多手段联动,确保鱼类通过过鱼设施后仍然能够生存。     

实验用鱼类的水环境及其标准化

由于近年实验用鱼作为新兴模式动物在国内外生命科技界发展迅速,因此实验用鱼的标准化特别是对其水环境的标准化已经成为实验用鱼类研究发展的必然趋势。本文分析和综述了实验用鱼类所需的水源及供水要求、水质和水环境的技术指标特点和对鱼类的影响,以期为斑马鱼、剑尾鱼等水生动物的实验动物化研究提供必要的资料。     

Foraminifera in the diet of coral reef fish from the lagoon of New Caledonia: Predation, digestion, dispersion

Marine benthic Foraminifera are abundant and thus represent a potential food source for fish. Previous studies of Foraminifera in fish diets have examined only small samples, with significant input reported only for a single surface-feeding species of fish. The present study is the first based on a significant sample (247 fish belonging to 83 species, 291 species of Foraminifera identified from more than 20,000 specimens examined). It provides new information on the contribution of Foraminifera to fish diets, and on the impact of fish predation on Foraminifera. The planktonic Tretomphalus phases, selectively ingested by Pomacentrus amboinensis, were the only significant nutritional input from Foraminifera. Herbivorous fish accidentally ingested living epiphytic Foraminifera, which were still living after digestion, and were defecated, with a significant effect on their dispersion. Carnivorous fish ingested a small number of tests, which were generally altered by the acidic phase of digestion and had no impact on foraminiferal assemblages. Sediment feeders ingested large quantities of empty tests that were released elsewhere, suggesting a possible bias in paleontological interpretations by mixing the thanatocoenoses. Observations on gut contents showed that the fish sometimes fed on a wide range of food, changing with food availability and individual preferences of fish.     

Impact of Great Crested Grebes (Podiceps cristatus L.) on fish ponds

Because Great Crested Grebes (Podiceps cristatus L.) mainly feed on fish, fish-farmers sometimes claim that economic losses are caused by grebes (EIFAC, 1988). Such claims were not based on scientific research.Therefore, a study was carried out to measure the impact of Great Crested Grebes on a fish-farm, managed by the Organization for the Improvement of Inland Fisheries (O.V.B.) in Valkenswaard (The Netherlands) during the period 1986–1988. The O.V.B. provided fish data for each pond including fish density and fresh fish weight for each fish species. The number of grebes was counted at least once a week. Activity patterns, including nocturnal activity, were determined both for the period with and without young. No nocturnal foraging activity was observed. Furthermore, fish biomass consumed per 1000 s foraging time by adult birds and chicks was calculated.In some fish-ponds grebes ate coarse fish, and chicks especially were fed these fish. The average daily fish consumption was 222 g for adults and 108 g for juveniles.Based on available fish data, it can be concluded that grebes consumed fewer fish than the number expected to die, and only marginally influenced the fish populations in the aquaculture ponds studied.     

Factors influencing nitrogen and phosphorus excretion rates of fish in a shallow lake

Summary 1. Fish excretion can be an important source of nutrients in aquatic ecosystems. Nitrogen (N) and phosphorus (P) excretion rates are influenced by many factors, including fish diet, fish growth rate and fish size. However, the relative influence of these and other factors on community‐level excretion rates of fish is unknown. 2. We used bioenergetics modeling to estimate excretion rates of eight fish species in a shallow, Minnesota (U.S.A.) lake over four months in both 2004 and 2005. Excretion rates of each species were summed for community‐level N and P excretion rates, as well as the N : P ratio of excretion. We then used a model‐selection approach to assess ability of independent variables to predict excretion rates, and to identify the most parsimonious model for predicting N : P excretion ratios and P and N excretion rates at the community scale. Predictive models were comprised of the independent variables water temperature and average fish density, fish size, fish growth rate, nutrient content of fish and nutrient content of fish diets at the community scale. 3. Fish density and nutrient content of fish diets (either N or P) were the most parsimonious models for predicting both N and P excretion rates, and explained 96% and 92% of the variance in N and P excretion, respectively. Moreover, fish density and nutrient models had 1400‐fold more support for predicting N and 21‐fold more support for predicting P excretion relative to models based on fish density only. Water temperature, fish size, fish growth rates and nutrient content of fish showed little influence on excretion rates, and none of our independent variables showed a strong relationship with N : P ratios of excretion. 4. Past work has focused on the importance of fish density as a driver of fish excretion rates on a volumetric basis. However, our results indicate that volumetric excretion rates at the community scale will also change substantially in response to changes in relative abundance of fish prey or shifts in relative dominance of planktivores, benthivores, or piscivores. Changes in community‐scale excretion rates will have subsequent influences on algal abundance, water clarity, and other ecosystem characteristics.     

Movements of adult Atlantic salmon in relation to a hydroelectric dam and fish ladder

The movements of adult Atlantic salmon were recorded as they approached, entered and ascended the pool-and-orifice fish ladder at Pitlochry Dam, Scotland. Thirty-nine returning salmon were captured in the River Tummel by rod-and-line angling, radio-tagged and released near where they were caught. The subsequent movements of each fish were then monitored. An electronic fish counter collected additional data on movements of untagged fish past a fixed point in the ladder. Of the 39 fish that were radio-tagged, 29 individuals were recorded approaching and ascended the ladder. The remaining fish either did not approach the dam (three fish), approached the dam after detailed tracking had ended (two fish), were recaptured by anglers (three fish), or the radio tags failed (two fish). Salmon released earlier in the year delayed longer before first approaching the dam. Delays between first approaching the dam and ascent of the ladder were greater for fish that approached the dam earlier. The majority of salmon visited the ladder entrance more than once (maximum 10 visits) before ascending. Having entered, all but four salmon ascended the fish ladder successfully on their first attempt. The four individuals that failed to do so succeeded on their second attempt. The rate at which salmon ascended the ladder was related directly to temperature. The shortest ascent time of a radio-tagged salmon was 5·25 h. Movements of eight of 11 tagged fish through the ladder ceased with the onset of darkness but continued on the following morning. No radio-tagged fish entered the ladder at temperatures below 9) C. Similarly, few untagged fish were recorded ascending the ladder by the electronic fish counter at water temperatures below 8·5) C. Records from the fish counter indicated that 92% of upstream movements were made during daylight.     

Effects of dietary trimethylamine on free amino acid and nonprotein nitrogen levels in muscle of the guppy, Poecilia reticulata, in relation to seawater adaptation

Guppies Poecilia reticulata acclimated to 100% seawater (SW) had lower taurine and alanine levels in muscle than fish kept in freshwater (FW). The glycine level, in contrast, was higher in SW fish than in FW fish. Levels of other free amino acids (FAA) were comparatively low and little different between fish adapted in FW and in SW. In both FW and SW fish almost all of muscle FAA showed little difference in levels between fish kept on diets containing three different levels of trimethylamine (TMA) (0, 223, and 334 mumol TMA/kg dry weight of diet). Total FAA and nonprotein nitrogen levels in muscle were unaffected by the difference in either the diet species or the ambient salinities. Muscle trimethylamine oxide levels were higher in SW fish than in FW fish. In both salinities, muscle trimethylamine oxide levels in fish on the diets containing 223 and 334 mumol TMA/kg were slightly greater than the level in fish on the TMA-free diet.     

Effects of habitat relocation on fish community structure- a case study

Local habitat structure and the environment in which it occurs are some of the key components in the development of fish communities. In this case study we examined a snapshot of their relative role following relocation of four artificial reefs (ARs) from a coral reef environment to a sandy area with adjacent sea grass beds. Monitoring the fish communities on ARs and in the surrounding areas revealed that in their new locations, the ARs contained greater fish richness and abundance, with more diurnal than nocturnal fish, but their feeding guilds were similar to those of fish in the reef location. A multivariate analysis showed that the ARs had distinctly different fish assemblage from those of their surroundings regardless of their location. Nonetheless, we identified an effect of the surroundings on AR fish community assemblage. We propose that on a meso- scale, fish community structure is primarily dependent on the properties of the AR rather than on those of the surrounding environment.     

Effects of high-relief structures on cold temperate fish assemblages: A field experiment

High-relief structures may influence the abundance and diversity of reef-associated fish. We conducted a field experiment to investigate whether the presence of vertical structures (PVC pipes) affects fish communities on artificial reefs. The effect of the height of the structures (1 and 3 m) was also tested. Furthermore, the effects on fish of placing artificial reefs on otherwise featureless bottoms were quantified. Algal and macro-invertebrate colonization of the reefs was also recorded. The experiment was carried out on the west coast of Sweden over a period of 1 year. The vertical structures had a positive effect on fish abundance but not on diversity. The height of the structures did not, however, influence the fish communities. Natural as well as urban vertical structures on the seafloor could have a positive effect on local fish abundance. The positive effects of artificial reefs on total fish abundance and diversity were immediate. Of the 10 species recorded, two, the black goby Gobius niger and the goldsinny wrasse Ctenolabrus rupestris, dominated over the whole survey period. There were significant temporal differences in fish abundance, and diversity increased with time.     

海洋鱼类肠道微生物研究进展及应用前景

肠道微生物在动物体内数量庞大、结构复杂,在宿主生长发育过程中发挥着重要作用.淡水鱼类肠道微生物的研究主要集中于其对鱼类生长代谢、营养吸收及免疫调节等方面的影响,海洋鱼类则研究相对较少,且多集中于肠道微生物多样性及其变动影响因素分析.本文在归纳总结鱼类肠道微生物功能及其研究方法的基础上,着重分析肠道微生物在海洋鱼类生长发...     

Immune response of fish to parasitic protozoa

Epizootic outbreaks of fish diseases are increasingly common as a result of intensive aquaculture, fish farming and sea ranching. Very few drugs are available for treatment or prophylaxis against fish diseases, and development of such compounds is inhibited by different national regulations governing the use of chemicals in fish for human or animal consumption. Alternative approaches are urgently needed. But although the taxonomy and biology of fish parasites have been extensively studied, relatively little is known about protective immunity in fish and the effects of parasites on the piscine immune system. In this article, Patrick Woo discusses the immune responses of fish to parasitic protozoa, showing that vaccination is a viable control strategy, and stressing the need for a coordinated global research programme on fish diseases.     

Extensive Aggregations of Wild Fish at Coastal Sea-Cage Fish Farms

We present evidence of a largely undocumented environmental effect of coastal sea-cage fish farms on wild fish. We estimated the total abundance and biomass of wild fish aggregated in the immediate vicinity of nine fish farms in the Mediterranean Sea and one farm off the east coast of Australia. Estimates of wild fish aggregations ranged from 2000 to 86000 individuals and from 100 kg to 38.5 tons of fish per farm and were always greater than control locations. Particularly large aggregations (>30000 fish, > 12 tons) occurred at half of the farms. Aggregations were temporally stable for weeks to months and most wild fish associated with farms (88%) were of adult size. Potential effects of such large aggregations of wild fish in the immediate vicinity of fish farms include increased vulnerability to fishing and pathogen transfer between caged and wild fish. We suggest specific legislation should be enacted wherever large aggregations of wild fish occur around fish farms to enhance the positive and reduce the negative effects of association.     

Fish ecoregions of Kansas: stream fish assemblage patterns and associated environmental correlates

Synopsis Principal components analysis was performed on fish presence/absence data for 39 common fish species from 410 stream sites in Kansas. The analysis confirmed ten ecologically meaningful fish assemblages, based on species associations. Factor scores based on these assemblages were then clustered into six geographic areas or fish ecoregions. Canonical discriminant analysis identified environmental variables that distinguished the derived fish ecoregions. Mean annual runoff, mean annual growing season, and discharge appear most important. Mean width, mean depth, chloride concentration, water temperature, substrate type, gradient, and percent of pool habitat were less important. Correspondence exists between these fish ecoregions and the patterns of physiographic regions, river basins, geology, soil, and potential natural vegetation in Kansas. The multivariate statistical approach used to classify fish ecoregions should have considerable potential value for fish assessment and management purposes in areas other than the state of Kansas.