Fish Feeding Behavior Research Articles

Palatability of stereoisomers and other amino acid derivatives to fish

Using a behavioral approach, it was shown that stereoisomers and other derivatives of amino acids (Ala, Glu, Gln; 0.1–0.01 М) have different palatability to fish (three-spined stickleback Gasterosteus aculeatus). The palatability of L-α-Ala is higher than of D-α-Ala or L-β-Ala, however, L-Glu and D-Glu equally increase the uptake of agar-agar pellets. L-Glu-Na has no stimulatory effect, probably, due to carnivorous feeding type in the three-spined stickleback. Palatabilities of L-Gln and L-Gln-HCl differ considerably. It is assumed that the influence of the configuration and structure of molecules on the palatability of amino acids to fish, as well as their taste preferences, are species-specific. The diversity of taste properties not only of L-, but also D-isomers of amino acids may matter in choosing adequate food objects in fish. Fish feeding behavior during oral sensory testing of artificial pellets, containing amino acids or their derivatives, obeys two alternative stereotypes, differing in the number of repeated manipulations with pellets and duration of the pellet retention time.

Development of a method for classifying and transmitting high-resolution feeding behavior of fish using an acceleration pinger

BackgroundMonitoring the feeding behavior of animals in the wild is key to understanding their energetics and the influence of the environment on their survival. Recently, a novel acceleration transmitter that processes acceleration data onboard and outputs identification results has been developed by AquaSound Inc. (Kobe, Japan) to investigate feeding biology in fish. To date, few attempts have been made to identify the feeding behavior of fish using transmitters, and none of these attempts accomplished classification of alternative feeding behaviors according to prey items. The objective of this study was to develop an algorithm that can be incorporated in the acceleration transmitter and can identify alternative feeding behaviors in fish, using red-spotted grouper (Epinephelus akaara) as a model species.ResultsMost of the identification algorithms describing feeding behavior in fish developed in previous studies used a combination of acceleration and angular velocity. In this study, we constructed an algorithm based on three-axis accelerometry data alone, since a gyroscope consumes much more electricity and would shorten the battery life of the transmitter. Acceleration data were obtained in tank experiments. Feeding behaviors, induced by feeding three types of live prey (Trachurus japonicus, Metapenaeus ensis and Hemigrapsus sanguineus), as well as other behaviors (routine and escape movements), were simultaneously recorded at 200 Hz by acceleration data loggers, implanted in the abdominal cavities of fish, and by a video camera. A decision tree, including a three-dimensional lookup table, was constructed to classify the behaviors into four behavior classes: shrimp-eating, fish-eating, crab-eating and other behaviors. The classification accuracy was estimated to be 0.77 (F-measure) for shrimp-eating, 0.73 for fish-eating, 0.71 for crab-eating and 0.78 for other movements, using fivefold cross-validation.ConclusionsThe algorithm developed in this study could be incorporated into the transmitter, which would record acceleration data at high frequency (200 Hz), process the data onboard and output classification results of behaviors. This method would reveal more aspects of fish biology, such as individual feeding strategies.

Near-infrared imaging to quantify the feeding behavior of fish in aquaculture

In aquaculture, fish feeding behavior under culture conditions holds important information for the aquaculturist. In this study, near-infrared imaging was used to observe feeding processes of fish as a novel method for quantifying variations in fish feeding behavior. First, images of the fish feeding activity were collected using a near-infrared industrial camera installed at the top of the tank. A binary image of the fish was obtained following a series of steps such as image enhancement, background subtraction, and target extraction. Moreover, to eliminate the effects of splash and reflection on the result, a reflective frame classification and removal method based on the Support Vector Machine and Gray-Level Gradient Co-occurrence Matrix was proposed. Second, the centroid of the fish was calculated by the order moment, and then, the centroids were used as a vertex in Delaunay Triangulation. Finally, the flocking index of fish feeding behavior (FIFFB) was calculated to quantify the feeding behavior of a fish shoal according to the results of the Delaunay Triangulation, and the FIFFB values of the removed reflective frames were fitted by the Least Squares Polynomial Fitting method. The results show that variations in fish feeding behaviors can be accurately quantified and analyzed using the FIFFB values, for which the linear correlation coefficient versus expert manual scoring reached 0.945. This method provides an effective method to quantify fish behavior, which can be used to guide practice.

Effects of Common Angler Handling Techniques on Florida Largemouth Bass Behavior, Feeding, and Survival

AbstractBlack bass Micropterus spp. support popular freshwater sport fisheries in North America. Bass anglers commonly adopt catch and release as a conservation practice, and frequently over 75% of angled black bass are released back into the water. If fish survive the angling event, the practice of catch and release as an alternative to harvest reduces direct mortality, but it has the potential to affect the postrelease feeding behavior and survival of the fish. The act of lifting black bass for handling, hook removal, and photograph opportunities may cause stress and injury, and the degree of injury sustained could be influenced by fish size. Holding fish in a tilted grip by the jaw has raised concern among anglers about potential damage to jaw musculature and tendons, as they may not support the fish's body weight out of water, particularly for trophy bass. We conducted an experiment with Florida Largemouth Bass M. salmoides floridanus to evaluate the relative differences in survival, jaw mechanics, and feeding success after the use of three common handling treatments: (1) a vertical hold using a lip‐grip device (vertical treatment); (2) a tilted, one‐handed grip using only the lower jaw (horizontal treatment); and (3) two‐handed support to the lower jaw and body (support treatment). The time taken by fish to regain equilibrium and resume normal swimming behavior after handling differed among the three treatments; the recovery period was shortest for fish in the support treatment (mean ± SD = 7 ± 10 s; vertical treatment: 33 ± 74 s; horizontal treatment: 12 ± 16 s). Minor injuries (e.g., abrasions and sores) and diseases (e.g., tumors and fungus) tended to increase after handling across the entire sample. Results suggested no evidence of handling‐specific differences in fish feeding behavior, jaw adjustments, and mortality after release. However, based on our results, we recommend that anglers use two‐handed support to handle Florida Largemouth Bass, thus minimizing the mean amount of time for an individual fish to regain equilibrium after an angling event.Received February 22, 2016; accepted October 7, 2016 Published online February 22, 2017

Effects of Glyphosate-Based Herbicide Sub-Lethal Concentrations on Fish Feeding Behavior.

Glyphosate-based herbicides are widely used in agricultural systems. Although the target organism are particularly plant organisms, there are numerous studies showing adverse effects in aquatic animals, such as inhibition of acetyl cholinesterase, effects on kidney, liver, and gill and stressors effects. This study analyzed the effects of commercial formulation of glyphosate on feeding behavior in Pacu (Piaractus mesopotamicus). Fish were exposed to three glyphosate concentrations (0.2, 0.6, and 1.8ppm) for 15 days. At concentrations of 0.2 and 0.6ppm, food intake decreased on day 13 and then returned to normal on day 15. At the highest glyphosate-based herbicide concentration, 1.8ppm, food consumption decreased dramatically and did not recover on day 15. This study showed that glyphosate-based herbicide at sub-lethal concentrations can affect feed intake in pacu and consequently inhibits its growth.

Toxic metals in tissues of fishes from the Black Sea and associated human health risk exposure.

The anthropogenic activities in the Black Sea area are responsible for toxic metal contamination of sea food products. In this study, several toxic metals: cadmium, lead, nickel, chromium, and copper were quantified in different tissues (digestive tract, muscle, skeleton, skin) of nine fish species (Neogobius melanostomus, Belone belone, Solea solea, Trachurus mediterraneus ponticus, Sardina pilchardus, Engraulis encrasicolus, Pomatomus saltatrix, Sprattus sprattus, Scorpaena porcus) by using atomic absorption spectrometer with a high-resolution continuum source and graphite furnace technique (HR-CS GF-AAS), and the risk of fish meat consumption by the young human population was evaluated. These metals are used in high amounts in industries located near the coastline such as shipyard construction and industrial plants. Toxic metal accumulation depends on fish feeding behavior, abiotic conditions, metal chemistry, and animal physiology. For instance, cadmium was measured in the muscle of the investigated species and average values of 0.0008-0.0338mgkg-1 were obtained. The lowest average value of this metal was measured at benthic species N. melanostomus and the highest at the pelagic predator T. mediterraneus ponticus. Generally, the highest metal concentration was measured in the digestive tract that has the role of biofilter for these contaminants. The risk of contamination is significantly reduced by avoiding the consumption of certain fish tissues (digestive tract and skin for copper and skeleton for nickel). An estimation of the dietary metal intake to young consumers was realized for each of the studied species of fish from Romanian, Bulgarian, and Turkish waters, during the period 2001-2014 in order to evaluate the risks of chronic exposure in time due to metal toxicity. This estimation is important for the prevention of chronic exposure due to metal toxicity. Food exposure to studied metals showed a negative trend for Romania, Turkey, and Bulgaria based on the data provided by this study. The young consumers were highly exposed to these elements during the 2001-2006 period as proven by the results from this study.

Effects of motorboat noise on foraging behaviour in Eurasian perch and roach: a field experiment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 564:115-125 (2017) - DOI: https://doi.org/10.3354/meps11997 Effects of motorboat noise on foraging behaviour in Eurasian perch and roach: a field experiment Carin Magnhagen1,*, Kajsa Johansson1, Peter Sigray2 1Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden 2Department of Underwater Research, Swedish Defence Research Institute, 164 90 Stockholm, Sweden *Corresponding author: carin.magnhagen@slu.se ABSTRACT: The negative impact of anthropogenic noise on marine animals is receiving increasing attention. In order to study the effect of motorboat noise on foraging behaviour in fish, we chose 2 species with different hearing abilities. The roach Rutilus rutilus has a better developed sense of hearing than the Eurasian perch Perca fluviatilis. The study took place in an inlet of the Bothnian Sea where boat traffic is almost absent. Groups of 6 fish were placed in field enclosures containing either one of the species or equal numbers of perch and roach. Half of each enclosure was covered with artificial vegetation. The fish were fed with pieces of saithe twice a day, both with and without the disturbance of an outboard motor. Sound pressure level and particle acceleration were measured for the motor, which was run at 2000 rpm. The trials were repeated for 5 d. Perch made fewer feeding attempts during noise exposure compared to controls in the single-species enclosures. As the experiment progressed, they gradually increased feeding and time spent in the open area, both with and without noise, indicating habituation. Habitat utilization was affected by the interaction of noise exposure and day. Roach responded to noise exposure with fewer feeding attempts, higher latency to enter the open area, and longer time spent in the vegetation compared to the controls without noise. Roach behaviour changed with time only when housed together with perch. This study, using authentic sound in a natural habitat, shows that noise exposure may affect the feeding behaviour of fish, that the response is species-specific, and that habituation and the presence of other species may modify the effects. KEY WORDS: Anthropogenic noise · Feeding activity · Field enclosures · Perca fluviatilis · Rutilus rutilus · Sound disturbance Full text in pdf format Supplementary material PreviousNextCite this article as: Magnhagen C, Johansson K, Sigray P (2017) Effects of motorboat noise on foraging behaviour in Eurasian perch and roach: a field experiment. Mar Ecol Prog Ser 564:115-125. https://doi.org/10.3354/meps11997 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 564. Online publication date: February 03, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

GABAA receptors activate fish feeding behaviour via two distinct functional pathways.

Benzodiazepines, acting through ionotropic receptors of γ-aminobutyric acid (GABAA receptors, GABAR), have been shown to modify feeding behaviour and increase appetite in humans and non-human subjects. However, the cellular and molecular mechanisms that underlie connected short-term behavioural fluctuations are still unclear. In the present study, we used Carassius gibelio (Prussian carp) as a model organism to research the impact of scantily explored benzodiazepine phenazepam (PNZ) on feeding behaviour and the related molecular mechanisms of PNZ action at single-cell and single-receptor levels. We found that the feeding activity of C. gibelio is under control of GABARs via two distinct mechanisms: orthosteric (triggered by GABA binding site) and allosteric (triggered by benzodiazepine binding site). PNZ displayed clear stimulatory effects on both mechanisms in a GABA-dependent manner. In addition, orthosteric and allosteric effects were found to be partially competitive, which leads to complex behavioural repercussions of conjoint effects of GABAR ligands.

Brain and intestinal expression of galanin-like peptide (GALP), galanin receptor R1 and galanin receptor R2, and GALP regulation of food intake in goldfish (Carassius auratus)

Galanin-like peptide (GALP) is a 60 amino acid neuropeptide originally discovered from porcine hypothalamus, and is involved in the regulation of food intake in mammals. Since its discovery, GALP and its receptors (GALR1 and GALR2) have been characterized in mammals, but no publications are available on GALP in fish and other non-mammals. The present study aimed to characterize brain and intestinal GALP and its receptors using immunohistochemistry in a teleost, the goldfish (Carassius auratus), and to study its effects on feeding behavior. Immunostaining of brain sections shows the presence of GALP- and GALR1- and GALR2-like immunoreactive cells in different encephalic areas, including the telencephalon, some hypothalamic nuclei, the optic tectum, the torus longitudinalis and the cerebellum. Signal for GALP was also observed in the fasciculus retroflexus. In the gut, GALP-and GALR1 and GALR2 immunoreactive cells were detected in the mucosa. Results from the feeding study demonstrate that intracerebroventricular administration of GALP (1ng/g bodyweight) increases goldfish food intake at 1h post-injection. These observations form the first report on the presence of GALP in the fish brain and gut, and also on its modulatory role on fish feeding behavior. GALP, as in mammals, appears to be a functional neuropeptide in goldfish.

Tracking Change in the Illinois River using Stable Isotopes in Modern and Ancient Fishes

The Illinois River has been heavily modified by human activities. We examined the nitrogen and carbon stable isotope composition of collagen from fish bones in two Native American middens comparing them to modern fishes in the River today. We also compared ancient and modern fishes to three reference samples—(i) Illinois River phytoplankton; (ii) backwater lake sediment; and (iii) tissue from riverside trees. We found a large increase in δ15N values in modern fish bone collagen relative to ancient collagen. However, there is little change in δ13C between ancient and modern samples. Bone collagen from invasive carp species (Hypopthalmichthys and Cyprinus) are similar to modern phytoplankton. All fishes are different from riverside trees and backwater lake sediment. The large shift in δ15N values between ancient and modern fishes is probably caused by contamination of the river by Chicago treated wastewater and by denitrified fertilizer run-off. Our results indicate a major change in nitrogen biogeochemistry in the modern river. Comparisons between ancient and modern δ13C values suggest little change in feeding behaviour of fishes between ancient and modern times. However, our data for invasive carp suggest strong competition with native planktivores. © 2016 The Authors. River Research and Applications Published by John Wiley & Sons Ltd.

Waste Feed from Fish Farms of the Eastern Mediterranean and Attraction of Wild Fish

Fish are attracted to floating structures, including coastal cage fish farms, sometimes in dense aggregations. To understand the influence of aquaculture on wild fish stocks, three samplings were carried out by fishing bait and trammel netting around two Eastern Mediterranean farms. A total number of 54 individuals belonging to 12 species were captured. Striped mullet, salema and white trevally were the species that consumed pellets in great quantity. The results of this preliminary study indicates that feeding behavior of wild fish around fish cages can have important ecological consequences on reducing the environmental effects of aquaculture in Pagasitikos gulf.

An experimental test of sub-hourly changes in macroinvertebrate drift density associated with hydropeaking in a regulated river

ABSTRACTWe investigated the response of the invertebrate drift to the regulated peaking Magpie River under experimental sub-hourly changes in flow conditions. Benthic invertebrates were also quantified upstream of invertebrate drift sampling sites in order to examine the propensity of nearby invertebrates to drift under hydropeaking cycles. To provide an understanding of the natural patterns of drift in relation to changes in discharge, the proximate natural Batchawana River was similarly sampled. Increased discharge was associated with higher drift densities and greater particulate organic matter in the Magpie River. At the family level, multiple drift responses were observed suggesting that ecological traits and behaviors drive drift response to changes in discharge. The drift densities of some invertebrates varied in proportion to discharge; whereas, other invertebrates in the drift decreased to pre-peaking levels shortly after peak discharge was reached, with some invertebrates exhibiting a secondary peak in density as discharge returned to pre-peaking levels. Although average drift densities were comparable between the two rivers, drift density on the natural Batchawana River was much more stable than that of the Magpie River. Changes in drift density associated with flow manipulation likely impact feeding patterns and behavior of drift feeding fish.

Effect of angling intensity on feeding behaviour and community structure of subtropical reef-associated fishes

Baited hooks used in angling may influence foraging behaviour and trophic interactions among reef fishes, which may be reinforced over successive generations. In contrast to other scavenging opportunities involving pulsed resources (e.g. food falls), there is an asymmetric susceptibility to becoming hooked for species and size classes. The resulting effect may provoke behavioural changes in reef fishes through cognitive or phenotypic selective processes. We investigated the effects of angling pressure on the feeding behaviour and community structure of reef-associated fishes using a novel underwater video approach. Fish community and behavioural responses to simulated angling baits were assessed at paired sites of contrasting angling pressure at Amity Point and Ballina, on the east coast of Australia from late 2013 to 2014. Bait introduction differentially influenced trophic interactions of reef-associated communities according to angling intensity regime. Locations with higher angling pressure correlated with increased feeding hesitation among potentially capture-susceptible species, most notably Acanthopagrus australis. The feeding hierarchy of less dominant feeders and their interactions also differed compared with those exhibited under lower angling intensity regimes. Specifically, smaller opportunistic feeders (e.g. Microcanthus strigatus) that could utilise angling bait for dietary supplementation without risk of being hooked were able to maintain higher feeding ranks in areas subject to high angling pressure due to reduced interference competition from larger species, e.g. A. australis. We discuss the potential for complex ecological effects to follow from high-intensity angling activities and highlight the potentially confounding effects of using bait as a focus for fish assemblage monitoring.

Turbidity amplifies the non‐lethal effects of predation and affects the foraging success of characid fish shoals

Summary In aquatic systems, many species rely primarily on visual cues to choose optimal foraging sites, capture prey and avoid potential threats. Increases in the turbidity of water reduce visibility and impede animals in determining the precise location of both predators and food. How individuals balance foraging decisions with anti‐predator behaviour in turbid environments is not well understood. We tested the effects of turbidity and predation risk on the foraging behaviour and feeding of an invertivorous fish, Moenkhausia forestii (Characidae), using a mesocosm experiment with a 2 × 2 design, crossing water clarity (clear versus turbid) with predation risk as reflected by the presence or absence of the piscivorous wolf‐fish Hoplias aff. malabaricus (Erythrinidae). We predicted that turbidity and predator presence would interact additively to reduce foraging rates, and that increased turbidity or predator presence would result in disproportionate food partitioning among shoal members. The combination of high turbidity and predator presence resulted in a significant reduction in prey consumption. Foraging success exhibited a skewed distribution in the turbid treatment, i.e. there was a decreased evenness of food partitioning within shoals. Hence, both turbidity and predator presence affect the prey consumption and foraging behaviour of invertivorous fish, with turbidity amplifying the non‐lethal effects of predation risk on foraging success. Our results imply that turbidity‐induced visual obstruction amplifies the negative effects of predator presence on invertivorous fish feeding behaviour, resulting in higher prey survival. Also, our finding that food intake by an intermediate consumer decreased in turbid water with a top predator lends no support to the hypothesis that intermediate consumer fish reduce their anti‐predator behaviour in turbid water. From a management perspective, our findings suggest that the oligotrophication of aquatic systems could dramatically increase predation on basal prey organisms naturally adapted to turbid waters, and reduce within‐shoal differences in feeding behaviour.

Selective feeding in fish: Effect of feeding and defensive motivations evoked by natural odors

The effect of feeding and defensive motivations evoked by natural olfactory signals (the food odor, the alarm pheromone) on choice and consumption of food items different in color and taste, and the manifestation of foraging behavior were examined in fish (koi Cyprinus carpio, roach Rutilus rutilus). The agar-agar pellets of red and green color having one of the amino acids (glycine, L-proline, L-alanine; all in concentration of 0.1 M) were simultaneously offered to single fishes in pure water, and in water extract of Chironomidae larvae or in water extract of fish skin. It was found out that odors used have different effects on fish foraging activity and on pellet selection for both pellet choice and consumption. On background of food odor, fish grasped pellets more often than in pure water. The equal choice of red and green pellets in pure water shifted to the preference of red ones in the presence of food odor. Despite the increase in the absolute number of pellets grasped, the relative consumption reduced and was replaced by selective consumption of pellets with glycine regardless of their color. Increasing demand for the food quality, due to the increased feeding motivation in response to food odor, is an important adaptation enhancing selection and consumption of food with more appropriate sensory qualities for fish. Defensive motivation caused by alarm pheromone suppressed predisposition. of fish to feed. Fish grasped pellets several times less often than in pure water and refused most of them. Any changes in the color or taste preferences were absent. Feeding behavior of fish of both species was characterized by repeated intraoral pellet testing, but in koi handling was less typical than in roach. In both species, handling activity was higher in those cases when the pellet was finally rejected. This activity was enhanced also on the background of food odor.

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.

Stilt fisher knowledge in southern Sri Lanka as an expert system: A strategy towards co-management

Most small-scale fisheries throughout the world are based primarily on fisher knowledge, which is essentially experiential knowledge consisting of a replicable, verbally transmitted set of skills. Even though fisher knowledge is well documented for some fisheries, there are only a few studies that explain how it actually works as a management system. Stilt fishing is a unique method confined to the southern coast of Sri Lanka. We studied traditional stilt fisher knowledge as an expert system that helps make decisions for successful fishing. Study shows that traditional fisher knowledge base and the decision-making process can be explained as an expert system. Fisher knowledge on biological and physical indicators that gives cues on commencement date of fishing season, arrival of fish schools and its composition and ecology and behaviour of target fish were distilled and empirically confirmed. Traditional stilt fishers were found to hold detailed knowledge about weather, fishing season, feeding and migratory behaviour of target fishes, mainly the bluestripe herring (Herklotsichthys quadrimaculatus). Empirical studies on feeding behaviour, movement and migratory path of bluestripe herring indicate the reliability of fisher knowledge. Fishers’ expectations before starting fishing (ex-ante) on species composition arriving at fishing territory were 100% accurate at the actual harvest in conclusion of fishing (ex-post). Success in fishing depends mainly on technical skills, and there exists considerable variation in the level of expertise among fishers. Traditional fishers are more successful in fishing than non-traditional fishers. Traditional stilt fishers provide inexpensive information that can complement scientific information to produce better management outcomes. Fisher knowledge can therefore be effectively utilized in formulating policies for co-management of coastal fisheries in Sri Lanka. Opportunities exist to set up proper baseline for the management of artisanal coastal fisheries with the ultimate aim of incorporating traditional fisher knowledge into management decision making.

The effect of sublethal concentrations of the water-soluble fraction of crude oil on the chemosensory function of Caspian roach, Rutilus caspicus (YAKOVLEV, 1870).

The water-soluble fraction of crude oil is a complex and toxic mixture of hydrocarbons. Because aquatic organisms directly encounter it, the water-soluble fraction plays an important role in the toxicity of crude oil in aquatic environments. To determine whether fish are attracted to or avoid the water-soluble fraction, Caspian roaches (Rutilus caspicus) were exposed to different concentrations of the water-soluble fraction in a choice maze apparatus. The results showed that Caspian roaches can detect and avoid 2 mg/L of the water-soluble fraction. To study the effect of the water-soluble fraction on the olfactory function of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water-soluble fraction for 96 h; afterward, exposed fish encountered food extract in a choice maze apparatus. The present study showed that the water-soluble fraction significantly impairs the olfactory function of roaches. To investigate the effect of olfactory system dysfunction on the feeding behavior of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water-soluble fraction. After 4 d, 8 d, and 12 d of exposure, the feeding behavior toward the food extract was tested. The results showed that both 3.2 mg/L and 16 mg/L of the water-soluble fraction suppress the feeding behavior of Caspian roaches. The present study demonstrates that sublethal concentrations of crude oil's water-soluble fraction impair the olfactory function of fish and consequently suppress the feeding behavior.

Ontogenetic changes in predator–prey interactions between two species of larval fishes and oyster veligers

The naked goby (Gobiosoma bosc), striped blenny (Chasmodes bosquianus), and eastern oyster (Crassostrea virginica) are common resident species in temperate Atlantic tidal waters. All three species produce planktonic larvae, and interactions between their early life stages likely influence recruitment success. Fish predation on oyster veligers requires co-occurrence as well as a match between prey behavior, size, and morphology and the ability of the predator to capture and engulf the veliger (prey). Wild plankton, oyster veligers, and wild plankton enriched with oyster veligers (mixed) were fed to cultured larval fishes during laboratory experiments. Three hypotheses were tested: (1) no fish species-specific differences in oyster veliger consumption exist within similar predator–prey development stage combinations, (2) postflexion blennies and gobies consume more veligers than preflexion fishes, (3) veligers reach a size refuge from fish predation by the umbo developmental stage. The resulting data provide a quantitative description of larval fish feeding behavior with respect to fish (preflexion, postflexion) and veliger (straight hinge, umbo) developmental stage. Selectivity for bivalve veligers as well as ontogenetic effects on the predator–prey interaction were examined. Fish nests were cultured to provide larval fish predators of known age. Overall, 70% of striped blennies and 59% of naked gobies consumed at least one prey item during the 3h experiments. There were fish species-specific differences in oyster veliger consumption between striped blennies and naked gobies. Striped blennies consumed more prey items including a wider range of veliger ages than larval naked gobies of the same developmental stages, regardless of the prey treatment. Fish selectivity was high for copepod nauplii and bivalve veligers and usually low for polychaete larvae, barnacle nauplii, and diatoms. There was a significant positive relationship between standardized consumption and predator development stage in the wild treatment for both fishes and in mixed and veliger treatments for blennies. All fishes consumed straight hinge veligers more often than umbo stage veligers. The largest veligers appear to reach a predation refuge from both fishes. Larval gobies and blennies are generalist predators that use seasonal pulses of zooplankton prey within temperate estuaries. Potential mismatches between predator–prey spatial and temporal overlap that might reduce fish recruitment are likely offset by adult spawning strategies that result in multiple nests within a long spawning season.

Food and Feeding of Fishes. What Do We Need to Know?

Abstract Unrevealing food and feeding habits of fishes is the centre of research in aquatic biology, ecology, conservation biology and fisheries. The current practice in feeding ecology of fish accredits it as descriptive ecology, relying primarily on the information of their diet, directly through gut analysis or indirectly by computing some diet based indices. Such methods often mislead in the understanding of the true feeding behaviour of organisms need for more reliable and functional approach. The main objective of feeding ecology is to evaluate feeding behaviour of fish. Recent developments in tools and techniques of analytical research is an opportunity to take up more reliable details by formulating affordable methodical design for recording, modulating and designing suitable approaches for better explanation of the feeding biology in fish.