Taxonomy-based differences in feeding guilds of fish

It has been taken for granted that feeding guilds and behavior in animals are linked to the taxonomic relatedness of species,but empirical evidence supporting such relationship is virtually missing.To examine the importance of taxonomy on trophic ecology,I here present the first well-resolved dietary taxonomy analysis based on feeding guilds(predation,herbivory,and filtering)among families and genera within the fish order Perciformes.Taxonomic relatedness in feeding did not vary with ecosystem dimension(marine vs.freshwater).Although predation dominates among Perciformes fishes,this study shows that in most cases taxonomic units(family or genus)are composed by species with several feeding guilds.Related species are more similar in feeding compared with species that are taxonomically more distant demonstrating that there is a greater variation of feeding guilds within families than genera.Thus,there is no consistency in feeding guilds between family-and genus-level taxonomy.This study provides empirical support for the notion that genera are more informative than families,underlining that family-level taxonomy should be avoided to infer feeding habits of fish species at finer taxonomic resolution.Thus,the choice of taxonomic resolution(family or genus level)in ecological studies is key to avoid information loss and misleading results.I conclude that high-rank taxonomic units(i.e.,above the generic level)are not appropriate to test research hypotheses about the feeding of fish.     

食蚊鱼昼夜摄食节律观察

以分时段采样法研究入侵物种食蚊鱼的夏季昼夜摄食节律。食蚊鱼夏季种群内有雌鱼、雄鱼和幼鱼三个不同的摄食类群,这三个类群的摄食节律差异明显。雌鱼摄食节律成双峰型,第一高峰在10:00,而最高峰在22:00,此时肠道食物团平均重量11.70±11.60mg,饱满指数为190.22±155.61。幼鱼也成双峰型,分别在6:00和18:00有两个摄食高峰,以清晨6:00为最高,肠道食物团平均重1.08±1.09mg,饱满指数为128.44±105.49。雄鱼则成单峰型,摄食高峰出现午后14:00左右,肠道食物团平均重0.71±0.96mg,饱满指数为71.80±107.65。食蚊鱼不同摄食类群间的摄食高峰交错出现,是其协调种内关系,降低种内竞争的一种有效行为机制。     

Hydrodynamics of suction feeding of fish in motion

Forward motion was shown to increase the efficiency of suction feeding by causing the ingested volume to be predominantly in front of the fish, instead of being a sphere centred on the fish mouth. This increases the distance from which a prey, located in front of the predator, can be ingested by suction.
A general hydrodynamic model of the external effects of the suction process is presented, showing that this is dependent upon a single non-dimensional parameter, the ratio of a characteristic mouth dimension, divided by the forward swimming speed and the suction time. Data for large-mouth bass, Micropterus salmoides show that the observed average forward velocity while feeding, of 3.1 body length/s, serves to increase the ingestion range by more than 60% over suction while not moving.     

Proteinases of hydrobionts--potential objects of fish feeding

The review analyzes data on activities and characteristics of proteinases of digestive system and of cathepsins of various tissues in potential preys of fish differing by the character of feeding. There are presented data on multiple forms and molecular mass of proteinases, species-related differences, dependence of proteinase activities on the life cycle stages, type of nutrition, and biochemical food composition as well as on temperature and pH optima. Role of cathepsin in evolution of enzymatic systems providing degradation of food protein components in fish is discussed.     

Evolutionary patterns in tropical marine reef fish feeding

The majority of tropical reef fishes are acanthopterygians. Most of them are percomorphs and thus are likely monophyletic. In accordance to modern systematics, the primitive types among the latter are large-mouthed suction feeders. Species from advanced families often have biting oral jaws with a reduced number and complexly shaped teeth. Mouth sizes decrease from the primitive towards the advanced reef fishes when ranked according to increasing family numbers (Nelson 1984). To create a functional resource axis, Randall's (1967) and Hobson's (1974) data on tropical reef fish feeding were re-interpreted by ranking food items from mobile to sessile prey. The primitive paracantho pterygian and acanthopterygian reef fishes are large-mouthed, suction-feeding predators on mobile prey. Most of the advanced, small-mouthed species are browsers and grazers, but often feed on mobile prey too. Obligatory specialists (monophagous and unable to switch) seem to be relatively rare among modern reef fishes. The trends stated above indicate a wealth of parallel developments in many advanced families of reef fishes towards small, often biting oral jaws. This parallelism may be the result of comparable regimes of selection pressures in reefs and of the need for newly evolved species to establish themselves within the already existing guilds.     

Zooplankton feeding in the fish Trichogaster pectoralis Regan

The traditional culture method of Trichogaster pectoralis, using zooplankton produced from fermenting aquatic weeds as a source of food for the fry, leads to productions of ca 1 000 kg ha^–1 a^–1. If chicken manure is applied at a rate of ca 450 kg ha^–1 month^–1 instead, much more zooplankton is produced more rapidly, and fish production increases to ca 2 000 kg ha^–1 a^–1. This results from a higher survival rate of the fry, which feeds on rotifers, ciliates, copepods and cladocera until a size of ca 15.0 mm, when plant material also becomes important in the diet.     

Dependency and independency among fish density and electivity indices in a stream fish assemblage

Habitat preferences can be identified from population density and electivity indices, which can be derived from either abundance or occurrence data. This study examined the preference detectability and independency of density and electivity indices from different data sources -- abundance and occurrence. Eight scenarios comprising four fish species along two environmental gradients (flow velocity and water depth) in an undisturbed mountain stream were used in this study. Fish density and seven electivity indices were calculated from abundance and occurrence data for the eight scenarios. The correlation analyses illustrated that abundance electivity indices were positively correlated with density in all eight scenarios while occurrence electivity indices were positively correlated with density in only three scenarios. Electivity indices were positively correlated with each other within the same data quality (abundance or occurrence) but not between. The Chesson’s L index was less correlated with other indices and should be used cautiously. Natural historical traits, such as social interactions among organisms, may affect the preference performance of density and electivity indices. In conclusion, density is a good preference indicator. Abundance electivity indices can represent density while occurrence electivity density should be used cautiously for fast assessment. Three electivity indices, Ivlev’s E and E′ and Jacobs’ D, were recommended for their ease of understanding.     

Monitoring the feeding activity of individual fish with a demand feeding system

Feeding activity of individual Arctic charr ( Salvelinus alpinus ) was recorded automatically for 29 days using a demand feeding system. Each of three groups of 15 fish was kept in 1 m³ tanks, containing brackish water at 10° C. Individual biting activity was continuously monitored using a PIT-tag (Passive Integrated Transponders) system with unique individual codes. The accuracies of the bite detection system were 91, 93.1 and 99.5% respectively, in the three tanks. In all tanks, most of the individuals (12–14) bit on the releasing trigger a few times during the first 3 days. Thereafter, one or two individuals per tank accounted for almost all of the biting activity. This pronounced shift in bite-number distribution among individuals was probably due to the development of a dominance hierarchy, in which the dominant individuals monopolized the trigger. Growth rates appeared to be highest among high ranking fish. The implications of using demand feeding and PIT-tag devices in feeding studies are discussed.     

Restricted fish feeding reduces cod otolith opacity

The purpose of this work was to examine the effect of reduced feeding and constant temperature on cod otolith opacity. Three groups of juvenile cod were given restricted food rations at different times for 4 months, resulting in depressed somatic growth. Otolith opacity was measured on pictures of the otolith sections. The otolith carbonate deposited during the experimental period was generally opaque compared to the more translucent otolith material deposited prior to and after the experimental period, when the fish were kept in a pond and in sea‐cages at higher temperatures. Large variations in otolith opacity were found between individual fish both within groups and between groups. In two of the three groups significantly more translucent otolith material was deposited in response to reduced feeding. Our results show that variations in feeding and hence fish growth resulted in variation in otolith opacity, but the effect was minor compared to that of variations in ambient temperature. The combined influence of these effects, which both act on fish metabolism, are most likely controlling the seasonal opacity changes observed in wild fish. Our results help explain the variations seen in fish at constant temperatures.     

Patterns and predictors of condition indices in a critically endangered fish

Hydrobiologia - Condition indices are key predictors of health and fitness in wild fish populations. Variation in body condition, therefore, can be used to identify stressful conditions that may...     

Diel pattern of pelagic distribution and feeding in planktivorous fish

Summary The spatial distribution of juvenile roach (Rutilus rutilus), rudd (Scardinius erythrophtalamus), bream (Abramis brama) and bleak (Alburnus alburnus) was registered by echosounding during two years in small Bavarian lakes. The gut contents of the fish were analysed in order to reconstruct their rhythmicity of food intake. Fish were found in the pelagic zone only during the night, feeding before midnight with maximal rate. The vertical position of the fish was dependent on the water transparency following a light intensity in the order of 10^-3 Lux. The diel migration between littoral and pelagic zones was a mainly horizontal one with a vertical component. Both the speed of increase of fish density in the open water and of the vertical movement was correlated to the speed of change of light intensity. Shoals broke up into single fish during the offshore migration. The span of presence in the pelagic zone was identical with the duration of the dark period. During winter no diel migration nor periodical feeding took place.     

黄河流域鱼类食性同资源种团的时空变化

鱼类资源保护是黄河流域生态保护和高质量发展的重要环节.通过历史资料整理和野外调查发现,1960-2019年,黄河流域共分布鱼类16目35科201种.其中,鲤形目物种数最多,占比60.7％;鲈形目次之,占比10.0％.1960-1980年分布鱼类15目28科182种;1980-2019年分布鱼类10目23科112种.源区...     

Mechanics of the feeding action of a cyprinid fish

The pressures in the buccal cavities of Golden orfe (Idus idus) have been recorded as the fish took food from a tube connected to a pressure transducer. Pressures 50–105 cm water below the pressure of the surrounding water were recorded as the buccal cavity expanded to suck the food in. Calculations based on the dimensions of the muscles lead to the conclusion that the levatores hyoidei, sternohyoideus, rectus abdominis, epaxial trunk muscles and obliquus internus probably all had to exert almost their maximum isometric tensions, to produce the largest reductions of pressure. These muscles seem nicely balanced in strength for their functions in feeding.     

Dietary self-selection in fish: a new approach to studying fish nutrition and feeding behavior

The principles of modern aquaculture encourage the development of fish feeds containing low fish meal content and several types of plant ingredients plus nutrients to avoid depleting global fish stocks and to reduce costs. However, food constituents can affect animal nutrition and feeding behavior, so the effect of different diets on fish behavior and growth needs to be understood to optimize the use of nutrients and to improve fish welfare. The development of multiple-choice self-feeding systems led to a new perspective for investigating these issues in aquaculture species. Our purpose with this review is to summarize the information that has been published to date on this topic and to identify gaps in knowledge where research is needed. Key subjects are assessed under the following major headings: How do we study dietary selection in fish? What food signals do fish use to choose the right diet? and How do fish respond to food challenges? The present review will provide a picture of the main results obtained to date in these studies in aquaculture fish species, as well as perspectives for future research in the field.     

Assessing fish metrics and biotic indices in a Mediterranean stream: effects of uncertain native status of fish

Implementation of the Water Framework Directive requires tools for measuring and monitoring the ecological status of aquatic ecosystems. Several indices are in use in the Iberian Peninsula, although there has been little comparison among them. We sampled the fish assemblage and limnological features of the Tordera stream (NE Spain) quarterly from September 2001 to May 2003 to evaluate the usefulness of several fish metrics and to compare habitat quality and biotic indices currently in use. Data for eight biotic and abiotic indices for this and three other Catalan river basins were also compiled in order to analyse the relationships among indices. In the Tordera stream, fish abundance and richness increased with stream order except in the last sampling site that had the lowest fish abundance owing to the effects of drought and water abstraction. Although most indices were positively correlated, some displayed low or null correlations particularly for the Tordera basin which is more affected by water abstraction and less by pollution; a commonly used physico-chemical index (ISQA) was the least correlated. In a regional fish index (IBICAT) under development, the brown trout (Salmo trutta) has been previously considered as introduced in the Tordera basin. Here, we report an old published record that demonstrates that trout was present before 1845 and we argue that its status should be considered as uncertain given the current information available. Whether brown trout is treated as native or introduced to this river basin has profound effects on the results of fish metrics because of its dominance in the upper reaches. We briefly discuss the role of introduced species, particularly in headwater streams, in the development of fish indices. Our study exemplifies the need for careful, basin-specific assessment of native/introduced status in the development of fish metrics. Handling editor: K. Martens     

The ontogeny of feeding behaviour in four species of centrarchid fish

Relatively little work has been done on the ontogeny of feeding behaviour in fish. One of the aims of this study was to compare the ontogeny of feeding behaviour in four species of centrarchid fish of diverse feeding guilds. A second aim was to test Mayr's hypothesis that the locomotory acts involved in the ontogeny of feeding behaviour would be stereotyped. All four species initially displayed five feeding acts, with three of the acts disappearing from the repertoire at various intervals. The disappearance of the acts appeared to be related to the size and not to the age of the fry. The acts decreased in frequency as the fry aged and differences among the species in frequencies were minimal. The data supported Mayr's hypothesis but a modifying corollary was added to account for changes due to maturation.     

Diversification and functional evolution of reef fish feeding guilds

A core eco‐evolutionary aim is to better understand the factors driving the diversification of functions in ecosystems. Using phylogenetic, trophic, and functional information, we tested whether trophic habits (i.e. feeding guilds) affect lineage and functional diversification in two major radiations of reef fishes. Our results from wrasses (Labridae) and damselfishes (Pomacentridae) do not fully support the ‘dead‐end’ hypothesis that specialisation leads to reduce speciation rates because the tempo of lineage diversification did not substantially vary among guilds in both fish families. Our findings also demonstrate a tight relationship between trophic habits and functional roles held by fish in reef ecosystems, which is not associated with a variation in the tempo of functional diversification among guilds. By illustrating the pivotal importance of the generalist feeding strategy during the evolutionary history of reef fishes, our study emphasises the role of this feeding guild as a reservoir for future diversity.