Diel variation in diet composition of a riverine fish community

Although diel food habit studies have been undertaken on a number of individual species, few studies have examined diel variation in the diets of fish communities. We examined the diel diet variation and feeding periodicity of a fish community in the Juniata River, Pennsylvania. Nine species, totalling 1,098 fish, were collected at 4-h intervals over a 24-h period in October 1989, in numbers sufficient to describe their diel variation in diet composition. Diel variation in diet composition was evident in all species, as no single prey taxon was dominant in the diet of any species during any 4-h interval. Ephemeropterans were the most important prey taxa for four species of centrarchids, whereas chironomids were the main prey of banded killifish, mimic shiners, and spotfin shiners. Algae was the major component in the diet of spottail shiners, whereas bluntnose minnows contained mostly detritus. Feeding activities of rock bass, redbreast sunfish, and pumpkinseed occurred at low levels throughout the day; peak feeding occurred from 2000 to 0400 hours. Food consumption of smallmouth bass increased throughout the day with peak consumption occurring at 2000 hours. Non-centrarchids fed little during daylight hours and showed peak activity at 2000–2400 h. Construction of a 24-hour diet from six 4-h interval estimates and feeding periodicity data provided a comprehensive representation of the diel feeding ecology of all species collected.     

Diel feeding ecology of the nymphs of Aeshna multicolor and Lestes unguiculatus (Odonata)

SUMMARY.

• 1 Diel feeding periodicity and diet composition of nymphs of Aeshna multicolor and Lestes unguiculatus were examined at 6 h intervals in a small pond. Feeding intensity of A. multicolor increased from 06.00 hours to approximately 18.00 hours whereas food intake by L. unguiculatus was uniformly high between 12.00 and 18.00 hours. Feeding of both species was reduced during the night.
• 2 Diel variation in diet composition was substantial in each species. Chironomid larvae were the major prey (48.9%) in the diet of A. multicolor. Zooplankton, mainly cladocerans (42.0%) and ostracods (21.1%), were the principal prey of L. unguiculatus. Detritus composed a substantial portion of the diets of both species.
• 3 Diet overlap (Cλ) at each 6 h interval was high (0.43–0.72) when detritus was included in the calculation and was low (0.48–0.54) when detrital material was omitted.

     

Diet and feeding habits of Economidichthys pygmaeus (Perciformes: Gobiidae) in Lake Pamvotis,NW Greece

The purpose of the study was to define the diet composition, feeding preferences, seasonal, size and sex related changes in diet, feeding strategy and diel cycle of Economidichthys pygmaeus. Important features of the overall feeding patterns of the goby include (i) feeding activity, (ii) bottom habits and (iii) consumption of food items to identify the dietary breadth. Stomach contents of 533 specimens, 13.42–48.65 mm total length (TL), collected by hand net (2 mm mesh size) from October 2006 to September 2007 were analyzed. The percentage of 76 empty stomachs (14.26%) did not vary significantly with season. The food composition suggested that the goby is a carnivorous fish. Prey items identified in the stomachs belonged to four major groups: Crustaceans, Insects, Mollusca and Plants. Copepods were the most important (%IRI = 57.51), especially in fish larger than 23 mm TL. Chironomids (%IRI = 43.23) constituted the main prey for fish <23 mm TL. Diet composition showed little seasonal variation. Copepoda dominated the diet in autumn and winter (43.4%; 82.4%) and were replaced by Chironomidae larvae in spring (39.7%) and summer (47.7%). During the reproductive season, large males show a narrow food spectrum as opposed to large females, reflecting the different activity pattern exhibited by males and females during the breeding season, since the former supports parental care. According to the modified Costello graphical method, specialist individuals form the goby population that feeds on two preferential prey types (e.g. Copepods, Chironomids). Nevertheless, they consume some occasional prey (e.g. Cladocera, Insects, Gastropods). The species foraged chiefly at night and early morning, during lower light intensity. The highest feeding activity recorded at night (02.00 hours) and during early morning (08.00 hours) could be related to the cryptic behaviour displayed by the species.     

Feeding ecology of larval and juvenile American shad (Alosa sapidissima) in a small pond

Release ponds are used as part of a multifacet effort to restore American shad ( Alosa sapidissima ) in the upper Susquehanna River basin. Little information exists, however, on the feeding ecology of young shad in small ponds. Consequently, we examined feeding ecology and prey selection of 299 larval and 299 juvenile American shad in a small pond during spring and summer. Larval shad mainly consumed copepods (37.7%) and cladocerans (37.4%) whereas juvenile shad ate chironomids (43.1%) and ostracods (28.4%). Larval and juvenile shad exhibited diel variation in diet composition and feeding periodicity. Food consumption by shad was minimal at night; feeding activity was highest during the day, peaking at 2000 h for both larvae and juveniles. Electivity values of shad larvae for prey taxa were highest for cladocerans (+0.27) and lowest for ostracods (−0.07). Electivity values of juvenile shad were highest for chironomids (+ 0.21) and ostracods (+ 0.09), and lowest for copepods (− 0.08) and baetids (− 0.14). Our data indicate differences in diet composition, prey preference and, to a lesser extent, feeding patterns between larval and juvenile American shad in small pond environments.     

Diel biting activity of Culex (Melanoconion) caudelli in Trinidad, West Indies

The diel biting periodicity of the arbovirus vector Culex (Melanoconion) caudelli Dyar and Knab (Diptera; Culicidae) in the Aripo-Wallerfield forest, Trinidad, was studied by collecting mosquitoes attracted to mouse-baited traps at 2-hourly intervals during eight 24 h periods. Biting females of Cx caudelli were collected during all night-time hours, 18.00-06.00 hours, with an overall unimodal pattern, i.e. one well-defined peak between 22.00 and 04.00 hours. This contrasts with previous reports that Cx caudelli is diurnally active. During the four moon phases, the period of peak biting activity varied from 22.00 to 24.00 hours at fullmoon, from 22.00 to 04.00 hours at first quarter, and from 24.00 to 02.00 hours at new moon and last quarter phases. The number of mosquitoes collected varied significantly with moon phases, the highest (152/24 h) being collected in the first lunar quarter and the lowest (71/24 h) in the last lunar quarter. Cloud cover and rainfall had no significant effect on the diel biting periodicity of Cx caudelli.     

Vertical distribution and feeding of larval blue whiting in turbulent waters above Porcupine Bank

In April 1995 a patch of blue whiting larvae Micromesistius poutassou was found at low illumination levels below 20 m depth near Porcupine Bank, west of Ireland, together with high densities of copepod nauplii and reduced turbulence rates, suggesting that larval blue whiting vertical distribution was determined by prey concentration, illumination and turbulence. Most (83·8%) larvae (2·0–7·5 mm L _s) had food in their guts. Feeding incidence and feeding intensities increased with increasing larval length. Only larvae >5·5 mm reduced numerical in favour of weight-based feeding intensity, indicating a shift in dietary composition. Maxima of the diel rhythms of feeding incidence and intensities occurred at 1800 and 2100 hours and minima at dawn (0600 hours). Proportionately, more nauplii were eaten by day but more copepod eggs and tintinnids at night. The distinct diel pattern in larval blue whiting feeding suggests that any analysis of factors mediating feeding must take into account diel feeding cycles. Larval feeding was significantly affected by wind speed. The larvae ate more and larger items at low than at higher turbulence levels. The data suggest that the maximum level of turbulence was not beneficial for larval blue whiting, but more moderate wind speeds could have had an enhancing effect on larval feeding success.     

Diel diet shift of roach and its implications for the estimation of daily rations

In a small, 12 ha, mesotropic lake, roach Rutilus rutilus performed diel habitat shifts that clearly influenced the composition of their diet. During daytime, roach stayed in the littoral zone and concentrated on littoral prey. At night they were found in the pelagic zone, and pelagic prey items such as Daphnia spp. or Chaoborus flaricans dominated their food. On a seasonal scale, there were shifts in the importance of different food items and in the diel pattern of feeding intensity. Bioenergetics modelling in combination with an evacuation rate method for estimating daily rations allowed for changes in feeding modes to be taken into account, and so food item specific daily rations over the season could be determined. With the evacuation rate method applied on selected days, diel changes in diet compositions and feeding intensities could be quantitatively accounted for. When the 24 h integrated diet proportions were then used as an input parameter for bioenergetics modelling, food item specific consumption could be determined over the entire sampling season. The consideration of the diel diet shifts proved to be essential for the model output. If only the daytime or the night-time diet composition (derived from one single daily sampling) was taken into account for bioenergetics modelling, severe under- or overestimations of daily rations for specific food items resulted.     

Diel feeding periodicity, daily ration and prey selection of a riverine population of juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum)

The diel feeding periodicity, daily ration and prey selection of juvenile chinook salmon, Oncorhynchus tshawytscha , were studied in relation to the available prey. Maximum dry weight of food intake occurred about dawn, when mayflies were the major prey, but the greatest number of freshly eaten prey occurred during the afternoon, when chironomids and terrestrial dipterans predominated. Feeding activity at night was low, with smaller mayflies comprising up to 50% of the prey. During the day the young salmon fed selectively on chironomids and the larger mayflies, while trichopterans and terrestrial taxa were under-represented in the diet. Food consumption over the 24-h period averaged 8.3% of the fish dry body weight. Prey abundance in the drift explained about 50% of the composition of the diet. Although the fish selected larger mayflies, size apparently was not a main criterion for selection because chironomids, although smaller than mayflies, were also frequently eaten. Previous dietary experience of the fish and the diel pattern of prey abundance appear to best explain the selective feeding of juvenile chinook salmon.     

Spatial and temporal variation in the diet of a predaceous stonefly (Plecoptera: Perlodidae)

SUMMARY. 1. Spatial and temporal variation in the diet of the univoltine predatory stonefly, Kogotus nonus , was studied over 3 years in a small Alberta stream to determine whether the relative abundance of prey types in the diet of Kogotus reflected relative prey densities in the stream and whether the variation in absolute feeding rate was related to either prey or predator density.
2. The seasonal shift from sole utilization of Orthocladiinae to inclusion of Baetis in the diet could not be attributed to seasonal changes in prey density, but was probably related to predator size and ability to handle very active prey. Most of the spatial variation in diet could be related to differences in background prey densities, but very high densities of Baetis caused the predator to specialize on this prey.
3. Feeding rate on Baetis . as assessed by per capita gut contents, showed a seasonal shift from a positive correlation with Baetis density in winter to a negative relationship with predator density in spring. This suggested that feeding by small Kogotus is a function of prey density. while feeding by later instars is influenced by between predator interactions such as interference.     

Changes in feeding behaviour of the larvae of the damselfly Enallagma cyathigerum in response to stimuli from predators

1. The feeding rates, diet composition and diel periodicity in feeding activity among larvae of the damselfly Enallagma cyathigerum Charp., exposed to chemical, visual and mechanical stimuli from the predators Ranatra linearis (L.), Notonecta glauca L. and Rutilus rutilus (L.) were investigated.
2. In response to chemical cues produced by all the predator species, larvae reduced their rate of feeding significantly (especially on large, sedentary prey).
3. Small larvae reacted more strongly than large ones to the kairomone produced by N. glauca.
4. The fish kairomone induced a reduction in feeding activity during daylight hours only. This reaction was more intense than the reaction to non-chemical cues.
5. Observed predator-induced changes in diet composition, caused directly by reduced activity during feeding, are discussed as an antipredator behaviour of damselfly larvae.     

A twelve-month field study of the west African thrush Turdus pelios (Passeriformes: Muscicapidae). Part 1: food and feeding ecology

The feeding ecology of Turdus pelios was studied from field observations and gizzard contents. Quantitative data on feeding were obtained from repeated standard "fixed route" walks and observational points at seven sites from January to December 1998 on 5065ha at the Obafemi Awolowo University campus, Ile-Ife (7 degrees 20' N, 4 degrees 33' E). Walks (each lasting about two hours) were started at various times of the day between 7.00 and 16.45 h. A total of 100 walks were made and binoculars were used to observe all feeding activities during 10 minutes at each site. Each feeding record included food type, method of feeding and reaction with con-specifics at feeding sites. Gizzards from mist-netted specimens were also studied. These birds fed most commonly twice a day between 06.00-9.30 hr in the morning and between 17.00-18.30 hr in the evening. Field observations showed that about 62% of the diet consisted of plant matter. The prey items were earthworms and terrestrial arthropods, of which orthopterans alone constituted 45% of the total. The prey size consumed by both sexes overlapped extensively: differences in prey size were significant only for spiders.     

Seasonal, diel and ontogenetic variation in feeding patterns of small yellow croaker in the central Yellow Sea

Stomach contents of 1603 small yellow croaker Pseudosciaena polyactis , sampled from seasonal bottom trawl surveys in the central Yellow Sea between March 2001 and January 2002, were examined. The results showed that small yellow croaker was a carnivorous predator and >30 prey species were identified from stomach contents analysis. Crustaceans (mainly euphausiids and decapods) were the most important prey, occurring in 93·1% of the stomachs containing food, and accounting for 77·6% of the total food by mass. Feeding activity was highest in autumn and lowest in spring and winter. Decapods were more important in summer, whereas euphausiids were more important during other seasons. Ontogenetic differences were found in the diet composition and feeding activity within the range of size (standard length, L _S) studied. The importance of fishes and decapods increased with L _S, whereas euphausiids, copepods and amphipods decreased in importance with L _S. Dietary breadth increased markedly for adults. A positive relationship was found between L _S and prey size. In each season the maximum diel feeding activity occurred at 0800 and 2400 hours, indicating that there was crepuscular and nocturnal feeding by small yellow croaker.     

Food partitioning between coexisting Atlantic salmon and brook trout in the Sainte‐Marguerite River ecosystem, Quebec

Food resource partitioning between similar‐sized, sympatric Atlantic salmon Salmo salar and brook trout Salvelinus fontinalis was examined as a possible mechanism enabling their coexistence in a stream (Allaire) of the Sainte‐Marguerite River ecosystem, Quebec, Canada. Fish stomach contents and invertebrate drift were collected concurrently during three diel cycles in August to September 1996. The food and feeding habits of an allopatric brook trout population in a nearby stream (Epinette) were studied for comparison. The diel feeding rhythms of the two coexisting fish species were similar. The composition of their diet, however, showed significant differences. Atlantic salmon predominantly (60–90%) fed on aquatic insects, mainly Ephemeroptera (35–60% of the diet). The brook trout mostly (50–80%) fed upon the allochthonous terrestrial insects (mainly adults of Coleoptera, Hymenoptera and Diptera) which comprised 5–40% of the stream drift. The allopatric brook trout fed opportunistically on the more abundant aquatic insects and terrestrial insects rarely formed 25% of its diet. The allopatric trout fed nearly twice as much as the sympatric brook trout during a day. The results suggest that the differences in feeding by brook trout in the two streams (with and without Atlantic salmon) are the result of inter‐specific interaction with Atlantic salmon and are not related to the differences in food availability between the two streams. Food resource partitioning between Atlantic salmon and brook trout may be viewed as an adaptive response resulting in a greater exploitation of available resources and coexistence.     

The effects of prey profitability and habitat complexity on the foraging success and growth of stonefly (Plecoptera) nymphs

• 1 The feeding behaviour of nymphs of the perlid stonefly Dinocras cephalotes when presented with two different mayfly prey types on different substrates was examined in the laboratory.
• 2 Most of the evidence suggested that Dinocras cephalotes did not choose between Baetis rhodani and Rhithrogena semicolomta as, under identical circumstances: (i) the survival of both prey types was the same; (ii) the predator's overall searching behaviour was similar in the presence of either mayfly, although B. rhodani was pursued more, especially on complex substrates; (iii) the number of attacks on both prey types was the same; and (iv) the intake of dry weight prey biomass over 24 h remained the same, irrespective of prey species.
• 3 The predation efficiency (no. of prey captured/no, of encounters) of D. cephalotes decreased with increasing substrate complexity—but only with R. semicolorata as prey, and also when more than one stonefly was present—but only when B. rhodani was the prey. Predator efficiency was greater at low densities of R. semicolorata but highest at a medium density of B. rhodani.
• 4 Increase in the body weight of D. cephalotes was greater when nymphs were fed a monospecific diet of R. semicolorata compared with one of B. rhodani. This was despite the findings that: (i) nymphs of B. rhodani contained 31.3% more protein (per mg dry body weight) than nymphs of R. semicolorata, whereas the latter contained 81.0% more chitin; and (ii) nymphs of R. semicolorata took 2.7 times as long to consume and almost twice as long to pass through the predator's gut. The longer gut passage time may have allowed a greater assimilation efficiency which may have led to the observed better growth.
• 5 Dinocras cephalotes is thought to feed opportunistically, with a certain daily food biomass intake as its primary need rather than any specific prey preference. Foraging decisions, or opportunities, affect the fitness of individual nymphs and this may be reflected in the wide size range of contemporary nymphs found in field populations. Variation in foraging efficiency by predators and evasion success by prey, across substrate types, is thought to contribute to the well-known microdistribution patterns of species observed in lotic communities.

     

Rapid cold-hardening of Drosophila melanogaster in a field setting

Abstract.  Although laboratory studies demonstrate that cooling to ecologically relevant temperatures and/or at ecologically relevant rates induces rapid cold-hardening (RCH) in a variety of insects, little is known of the induction of RCH in nature. In the present study, caged Drosophila melanogaster (1–2 days posteclosion) from a colony established with flies collected locally are placed in a field setting (i.e. in approximately 4-cm deep leaf litter beneath an apple tree in Mount Pleasant, Michigan) during late afternoon (18.00 h EST; 05.00 h GMT). As the cage temperature falls from 22.1 ± 0.8 to 10.1 ± 0.1 °C between 18.00 and 06.00 h, the proportion of flies surviving a transfer to –6 °C for 1 h increases from 10.0 ± 6.2% to 68.1 ± 7.2%. When obtained from field cages, and then cooled from 23 °C at approximately 0.33 °C min⁻¹, more female flies remain behaviourally responsive (clinging to surfaces, exhibiting an active righting response, and/or climbing) at temperatures of 8–12 °C (24.00 h samples) or 7–12 °C (06.00 h samples), than do those sampled from cages kept in an incubator (23 °C). Field cooling reduces chill coma temperature from 8.7 ± 0.2 °C at 06.00 h to 7.1 ± 0.2 °C at 24.00 h, and to 6.6 ± 0.2 °C at 06.00 h. These data demonstrate that, in a recently collected culture of D. melanogaster , natural changes in microenvironmental temperature induce RCH that can benefit the organism at temperatures encountered in nature.     

Relative contribution of euphausiid prey species and timing of breeding to Cassin's auklet Ptychoramphus aleuticus growth: within-season effects

Within-season variation in life-history parameters is characteristic of long-lived seabirds breeding in dynamic marine environments. Zooplanktivorous Cassin's auklets Ptychoramphus aleuticus breeding in central California feed primarily on euphausiid crustaceans, and switch from provisioning their offspring with Euphausia pacifica early in the nestling period to Thysanoessa spinifera later in the nestling period. I examined the effects of seasonal variation in nestling diet composition and meal mass, and timing of breeding and breeding attempt number (only/first or second breeding attempt) on the growth rate of individual nestlings on Southeast Farallon Island, California. For individual years, there were variable seasonal trends in growth, but no trends were apparent when all years were combined. Along with the predicted seasonal shift in prey use, there was a concurrent decrease in meal mass. In multivariate models, there were significant and positive effects of the mass proportions of E. pacifica and T. spinifera in the diet, meal mass and breeding attempt number on nestling growth, while the effect of hatching date on growth was negative. The relative influence of T. spinifera on growth was stronger than that of E. pacifica , the effects of hatching date on growth were likely dependent on the effects of breeding attempt, and breeding attempt exerted the strongest effect on nestling growth of all parameters examined. These suggest that the seasonal switch in prey use is advantageous (whether intentional or otherwise). Results illustrate the importance of adequate availability of both E. pacifica and T. spinifera to auklets in the Gulf of the Farallones. This study represents a unique approach in the investigation of linkages between individual nestling growth rate and diet and breeding phenology parameters by focusing on a fine temporal scale.     

Temporal variability in marine feeding of sympatric Arctic charr and sea trout

The marine feeding pattern of anadromous brown trout (sea trout) Salmo trutta and Arctic charr Salvelinus alpinus was studied during June to August in 1992–1993 and 2000–2004 in a fjord in northern Norway. In general sea trout fed proportionally more on fishes than on crustaceans and insects (81, 1 and 18% by mass, respectively) by comparison with Arctic charr (52, 25 and 22% by mass, respectively). Herring Clupea harengus dominated the total fish diet of both species, but the Arctic charr also fed significantly on gadoids and sandlance Ammodytes spp. While sea trout became virtually all piscivorous at fork lengths ( L _F) ≥250 mm, the Arctic charr was ≥400 mm L _F before shifting totally to a fish diet. Despite annual variation in diet and forage ratios, there was a clear shift in diet from 1992–1993 to 2000–2004. Sandlance and different crustaceans constituted most of the diet during the initial period with a shift towards gadoids and especially herring during the latter period. This shift seemed to be associated with a high abundance of herring larvae during the latter sampling period, indicating a preferential selection on herring when present, particularly by sea trout. Furthermore, an index indicated dietary overlap in years with intensive feeding on herring of both species, and usually differences in the trophic ecology during years feeding mostly on other prey species. In combination, it was hypothesized that the two species reflect the type of marine prey present within a fjord system over time, and therefore provide an index of variation in the production and biological diversity of their potential prey within fjords.     

The functions of plant feeding in the omnivorous predator Dicyphus hesperus: water places limits on predation

1. Dicyphus hesperus Knight (Heteroptera: Miridae) nymphs were fed from egg hatch to the adult stage on Ephestia kuehniella eggs provided either alone or in combination with tomato leaves or with a supplementary water source. 2. Only 6% of individuals completed nymphal development on a diet of eggs alone. In contrast, a high proportion of nymphs completed development on a diet of eggs when either tomato leaves (97%) or a supplementary water source (88%) were provided. 3. The development times of nymphs given access to leaves were significantly shorter than those of nymphs given access only to supplementary water. 4. Adult female D. hesperus that were given access to tomato leaves prior to feeding trials consumed significantly more eggs in a 4‐h period than females that were dehydrated before trials. Dehydrated females that were allowed access to water for 3 h before trials consumed an intermediate number of eggs. 5. Plant feeding or access to some other water source is required for prey feeding, growth, and development in D. hesperus, and acquisition of water is proposed as a primary function of plant feeding. In addition, D. hesperus derives nutrients from plant feeding that increase the rate of nymphal development, although nymphs cannot complete development when provided only with tomato leaves. 6. Three simple models are presented of feeding behaviour in predatory Heteroptera where the amount of plant feeding either decreases, increases, or is constant as a function of the amount of prey feeding. The models are discussed with reference to the results and the probable multifunctional nature of plant feeding in predatory Heteroptera.     

Diel feeding patterns of the congiopodid fishHypodytes rubripinnis in Aburatsubo Bay,Japan

Diel changes in the feeding intensity and diet composition of the congiopodid fishHypodytes rubriphnnis were studied in Aburatsubo Bay, Miura Peninsula, Japan, on July 24 and 25, 1985. In samples taken at night, the ratio of stomach content weight to body weight was high and the frequency of occurrence of fish with empty stomach was very low, while the reverse was the case in the daytime, suggesting that this species feeds intensively at night, instead of during the day. Gammarids were the most dominant prey and isopods and caprellids were next important. These three prey items accounted for 91% of the total diet by number. The proportion of isopods in the total diet showed the most remarkable diel change. They amounted to about 30% at night, but were not consumed in the daytime.     

Diel variations in the assemblage structure and foraging ecology of larval and 0+ year juvenile fishes in a man‐made floodplain waterbody

This study investigated diel variations in zooplankton composition and abundance, and the species composition, density, size structure, feeding activity, diet composition and prey selection of larval and 0+ year juvenile fishes in the littoral of a man‐made floodplain waterbody over five 24 h periods within a 57 day period. There was a significant difference in the species composition of diurnal and nocturnal catches, with most species consistently peaking in abundance either during daylight or at night, reflecting their main activity period. There were no consistent diel patterns in assemblage structure or the abundance of some species, however, most likely, respectively, due to the phenology of fish hatching and ontogenetic shifts in diel behaviour or habitat use. There were few clear diel patterns in the diet composition or prey selection of larval and 0+ year juvenile roach Rutilus rutilus and perch Perca fluviatilis, with most taxa consistently selected or avoided irrespective of the time of day or night, and no obvious shift between planktonic and benthic food sources, but dietary overlap suggested that interspecific interactions were probably strongest at night. It is essential that sampling programmes account for the diel ecology of the target species, as diurnal surveys alone could produce inaccurate assessments of resource use. The relative lack of consistent diel patterns in this study suggests that multiple 24 h surveys are required in late spring and early summer to provide accurate assessments of 0+ year fish assemblage structure and foraging ecology.