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Fish Predators (fish + predator)
Selected AbstractsOtolith chemistry of prey fish consumed by a fish predator: does digestion hinder Russian doll techniques?JOURNAL OF FISH BIOLOGY, Issue 10 2009Q. E. Phelps The effect of digestion by a predatory fish (largemouth bass Micropterus salmoides) on stable isotopic (,13C and ,18O) and trace elemental (Sr:Ca and Ba:Ca) compositions of prey fish (bluegill Lepomis macrochirus) otoliths was investigated in a laboratory experiment. Trace element and stable-isotopic signatures of L. macrochirus otoliths were not significantly altered for up to 16 h after L. macrochirus were consumed by M. salmoides. Prey fish otoliths recovered from predator digesta can retain environmental stable isotopic and trace elemental signatures, suggesting that determination of environmental history for prey fishes by stable-isotope and trace-element analysis of otoliths recovered from stomachs of piscivorous fishes will be feasible. [source] Trophic cascades in a temperate seagrass communityOIKOS, Issue 5 2008Per-Olav Moksnes We assessed the relative importance of bottom,up and top,down processes in structuring an eelgrass community in Sweden, a system impacted both by eutrophication and overfishing. Using artificial seagrass as substrate, we manipulated nutrient levels and predator abundance in a full-factorial cage-experiment. The results revealed a seagrass community dominated by strong top,down processes controlling the aggregate biomass of mesograzers and macroalgae. In the absence of predators the large amphipod Gammarus locusta became very abundant resulting in a leaf community with low biomass of algae and smaller mobile fauna. One enclosed gobid fish predator reduced the abundance of adult G. locusta by >90%, causing a three to six times increase in the biomass of algae, smaller mesograzers and meiofauna. Numerous small predators in uncaged habitats reduced the biomass of G. locusta and other mesograzers by >95% in comparison to the fish treatment, further increasing the biomass of epiphytic algae and meiofauna. Although water column nutrient enrichment caused a temporal bloom of the filamentous macroalgae Ulva spp., no significant nutrient-effects were found on the algal community at the end of the experiment. The only lasting nutrient-effect was a significant increase in the biomass of G. locusta, but only in the absence of ambient predators. These results demonstrate that mesograzers can respond to enhanced food supply, increase their biomass and control the algal growth when predation rates are low. However, in the assessed system, high predation rates appear to make mesograzers functionally extinct, causing a community-wide trophic cascade that promotes the growth of ephemeral algae. This top,down effect could penetrate down, despite a complex food-web because the interaction strength in the community was strongly skewed towards two functionally dominant algal and grazer species that were vulnerable to consumption. These results indicate that overexploitation of gadoid fish may be linked to increased macroalgal blooms and loss of eelgrass in the area through a trophic cascade affecting the abundance of mesograzers. [source] Assessing the potential for fish predation to impact zebra mussels (Dreissena polymorpha): insight from bioenergetics modelsECOLOGY OF FRESHWATER FISH, Issue 2 2004M. A. Eggleton Abstract,,, Rates of annual food consumption and biomass were modeled for several fish species across representative rivers and lakes in eastern North America. Results were combined to assess the relative potential of fish predation to impact zebra mussels (Dreissena polymorpha). Predicted annual food consumption by fishes in southern waters was over 100% greater than that in northern systems because of warmer annual water temperatures and presumed increases in metabolic demand. Although generally increasing with latitude, biomasses of several key zebra mussel fish predators did not change significantly across latitudes. Biomasses of some less abundant fish predators did increase significantly with latitude, but increases were not of the magnitude to offset predicted decreases in food consumption. Our results generally support the premise that fishes in rivers and lakes of the southern United States (U.S.) have inherently greater potential to impact zebra mussels by predation. Our simulations may provide a partial explanation of why zebra mussel invasions have not been as rapid and widespread in southern U.S. waters compared to the Great Lakes region. Resumen 1Modelamos la tasa de consumo anual de alimento y biomasa para varias especies de peces en una muestra representativa de ríos y lagos del este de Norte América. Combinamos los resultados para evaluar el potencial relativo que estas especies de peces pueden ejercer sobre la abundancia del mejillón asiático Dreissena polymorpha. Las predicciones sobre consumo para peces en lagos y ríos del sur fueron más del 100% comparadas con sistemas septentrionales. Esto se puede deber a las temperaturas anuales más altas y aumentos en la demanda metabólica de peces en ríos y lagos del sur de Norte América. 2La biomasa de varias especies claves de peces que consumen D. polymorpha no cambió apreciablemente con latitud. La biomasa de algunos peces que consumen D. polymorpha aumentó significativamente con latitud, pero este aumento no era de una magnitud suficiente para compensar la disminución en el consumo de alimento. 3Nuestros resultados apoyan generalmente la premisa de que los peces en ríos y lagos del sur de los Estados Unidos (EE.UU.) tienen un potencial inherente mayor para poder controlar D. polymorpha. Nuestras simulaciones proporcionan una explicación parcial de por qué las invasiones de D. polymorpha no han sido tan rápidas y ampliamente distribuidas en aguas sureñas comparado con la región de los Grandes Lagos. [source] Subtle top-down control of a freshwater meiofaunal assemblage by juvenile fishFRESHWATER BIOLOGY, Issue 9 2010GERARD DINEEN Summary 1. Top-down control of prey assemblages by fish predators has been clearly demonstrated in lakes (for zooplankton prey) and rivers (for macroinvertebrate prey). Fish predation can have a significant impact on the body size of prey assemblages; often large-bodied prey are reduced in abundance, and indirect facilitation of small-bodied prey occurs potentially initiating a trophic cascade. 2. Benthic communities in aquatic ecosystems also include a numerous and functionally important meiofaunal-sized component, but in freshwaters the impact of fish predation on meiofaunal assemblages is unknown. We used a laboratory microcosm study to explore the impact of juvenile fish predation on the abundance and size structure of a riverine meiofaunal assemblage. 3. The presence of fish in our microcosms had no significant effect on overall meiofaunal (temporary and permanent) abundance. However, for the Copepoda, we found the first evidence of top-down control of freshwater meiofaunal assemblages; in microcosms with juvenile fish, the abundance of large-bodied Copepoda was significantly reduced, whereas small-bodied Copepoda were significantly more abundant suggesting indirect facilitation. 4. We conclude that predation by juvenile fish can alter the structure of freshwater meiofaunal assemblages, although we do not yet know whether these relatively subtle changes are overwhelmed by large-scale events such as flow disturbances. [source] Potential sources of food hazards in emerging commercial aquaculture industry in sub-Saharan Africa: a case study for UgandaINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2009Ananias Bagumire Summary A study was conducted to assess sources of food hazards in Uganda's emerging commercial aquaculture industry based on Hazard Analysis Critical Control Point (HACCP), focusing on inputs, their sources and farm-practices on ten representative commercial farms. Critical control points (CCPs) were identified to reveal potential hazards that would jeopardise any export trade. Site selection, water quality, fertiliser, fish seed, fish rearing facilities, feeds, and post-harvest practices were the main CCPs identified. Animal manure was used to generate plankton as pond fertiliser in nine of the ten surveyed farms and veterinary drugs were not found in any of the ten farms, which is starkly different from aquaculture in indutrialised countries. Potential sources of hazards from water were mainly: municipal waste flow which was more likely on five of the ten farms, domestic waste (four farms), agricultural run-off (three farms), and low water pH (three farms). Fish fry and fingerlings from other farms, feeds formulated on-farm from unapproved sources, chemical products, uncontrolled fish predators, and domestic animal and human activities were the other potential sources of hazards. A complete application of HACCP is recommended for producing safe products that meet the strict market standards of developed countries. [source] Escape behaviour and ultimate causes of specific induced defences in an anuran tadpoleJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2005C. Teplitsky Abstract Induced defences, such as the predator avoidance morphologies in amphibians, result from spatial or temporal variability in predation risk. One important component of this variability should be the difference in hunting strategies between predators. However, little is known about how specific and effective induced defences are to different types of predators. We analysed the impact of both pursuing (fish, Gasterosteus aculeatus) and sit-and-wait (dragonfly, Aeshna cyanea) predators on tadpole (Rana dalmatina) morphology and performance (viz locomotive performance and growth rate). We also investigated the potential benefits of the predator-induced phenotype in the presence of fish predators. Both predators induced deeper tail fins in tadpoles exposed to threat of predation, and stickleback presence also induced longer tails and deeper tail muscles. Morphological and behavioural differences resulted in better escape ability of stickleback-induced tadpoles, leading to improved survival in the face of stickleback predation. These results clearly indicate that specific morphological responses to different types of predators have evolved in R. dalmatina. The specific morphologies suggest low correlations between the traits involved in the defence. Independence of traits allows prey species to fine-tune their response according to current predation risk, so that the benefit of the defence can be maximal. [source] Extreme habitats are not refuges: poeciliids suffer from increased aerial predation risk in sulphidic southern Mexican habitatsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010RÜDIGER RIESCH Extreme environments are often considered a predation refuge for organisms living in them. In southern Mexico several species of poeciliid fishes are undergoing incipient speciation in a variety of extreme (i.e. permanently dark and/or sulphidic) freshwater systems, and previous research has demonstrated reproductive isolation between populations from sulphidic and adjacent benign habitats. In the present study, we investigated bird predation rates (measured as successful captures per minute) in two sulphidic surface and several benign surface habitats, to test the hypothesis that extreme habitats are predation refuges. We found capture rates to be approximately 20 times higher in sulphidic environments: probably facilitated by extremophile poeciliids spending most of their time at the water surface, where they engage in aquatic surface respiration as a direct response to hypoxia. Even birds that are usually not considered major fish predators regularly engage in fish predation in the toxic habitats of southern Mexico. Our results demonstrate that extreme environments do not necessarily represent a refuge from predation, and we discuss the general importance of predation in driving incipient speciation in these systems. Finally, we hypothesize that natural selection via avian predation may play an important role in maintaining reproductive isolation between divergent poeciliid populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 417,426. [source] | ||||||||||||||||||||||