Feeding chronology and habits of Alosa spp. (Clupeidae) juveniles from the lower Hudson River estuary, New York

Synopsis Feeding habits of juvenile alewife, A. pseudoharengus, blueback herring, A. aestivalis, and American shad, Alosa sapidissima, were examined over a 24 h period at an inshore location on the lower Hudson River. Feeding periodicity differed by species: alewives showed no diel differences, whereas shad fed least intensively near dawn and herring least intensively at night. Alewives fed primarily on chironomids and the amphipod Corophium lacustre, shad on Formicidae and larval chironomids, and herring on chironomids and copepods. Diel variation in prey selection was evident. Dietary overlap was generally greatest between alewife and herring and least between shad and herring.     

Factors affecting migration patterns of juvenile river herring in a coastal Massachusetts stream

Juvenile anadromous river herring (alewives, Alosa pseudoharengus, and blueback herring, Alosa aestivalis) spend 3–7 months in freshwater before migrating to the ocean, often exhibiting waves of early and late migrations. Migratory patterns and associated abiotic and biotic factors were examined for both species migrating in 2003 from Herring River in Bourne Massachusetts. Migrating herring were grouped into two temporal periods and separated by species. Relationships between abiotic (water temperature, lunar phase, and precipitation) and biotic (size, age, growth rate, and hatch date) factors and the timing of out-migration (transition to seawater) were examined. Blueback herring migration coincided with a sharp decrease in temperature consistent with the time of year. Peaks in alewive migration may reflect adaptive traits maximizing likelihood of survival through seasonal marginal stream habitats and also avoiding lethal water temperatures in winter. Migrating bluebacks exhibited a single migratory period (late September–October) which occurred between the early and late migratory pulses of the alewives. These patterns may also represent distinct migration strategies between early and late migrating alewives and between the two species of river herring. Early migration may be a mechanism by which factors such as competition and low food availability are mitigated. In contrast, environmental conditions during the post hatching time of late migrators may allow for a size maximizing strategy that promotes migration from the nursery area as late as possible.     

Population structure and biology of alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the Saint John River,New Brunswick

Synopsis Examination of more than 2,000 alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) from various areas in the Saint John River, N.B., showed differences in their morphometric and meristic characters. They differed also in length and age, compositions, spawning time, length and age at maturity, back-calculated lengths, and growth parameters. Within each species, between-area comparisons showed significant differences in some of their meristic characteristics.To test a homing hypothesis for alewives, a multivariate analysis was performed on eight meristic characters. Two discriminant function programs, discriminant analysis for two groups and a multiple group stepwise discriminant analyses were used. Values of the generalized Mahalanobis D² and percent overlap in frequency distributions of meristic characters suggest that considerable straying of fish, especially between adjacent areas occurs during upstream spawning migration.This article is one of several papers presented at the Second European Ichthyological Congress, Paris, 8–15 September 1976, to be published in Environmental Biology of Fishes.     

Phagotrophic Mechanisms and Prey Selection in Free-living Dinoflagellates1

Three types of feeding mechanisms are known in dinoflagellates: pallium feeding, tube feeding, and direct engulfment. Pallium feeding has only been described for heterotrophic thecate species (Protoperidinium, Diplopsalis group). Tube feeding is commonly found among both naked and thecate species of mixotrophic and heterotrophic dinoflagellates (e.g. Amphidinium, Dinophysis, Gyrodinium, Peridiniopsis). Direct engulfment is mainly found among naked species (e.g. Gymnodinium, Gyrodinium, Noctiluca): recently, however, some thecate species have been shown to use this feeding mechanism as well. Feeding behavior in dinoflagellates involves several steps prior to actual ingestion, including precapture, capture, and prey manipulation. As feeding mechanisms allow the ingestion of relatively large prey or parts thereof, dinoflagellates are regarded as raptorial feeders. While prey size plays an important role in the ability of dinoflagellates to ingest food, this alone cannot explain observed prey preferences. Some dinoflagellate species can be very selective in their choice of prey, while others show a remarkable versatility.     

Genetic diversity and structure of two hybridizing anadromous fishes (Alosa pseudoharengus,Alosa aestivalis) across the northern portion of their ranges

Alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), also known collectively as either river herring or gaspereau, are anadromous clupeid fishes that display spatiotemporal overlap during riverine spawning migrations. Both species have experienced severe population declines within portions of their ranges. Evidence that they home to their natal rivers to spawn suggests the likelihood of ecologically significant population structure, yet this hypothesis has not been rigorously tested. We examined genetic diversity, differentiation and population structure in 34 alewife and four blueback herring populations spanning a 2,500 km portion of their northern range, using 14 microsatellite loci. Significant differentiation was detected among most rivers, and eight genetically defined alewife population clusters that largely corresponded to hydrographic regions were identified. Similar population structure was seen for blueback herring. Genetic isolation by distance was not significant among alewife populations in regions that have been historically influenced by dams, and/or stock transfers, but was highly significant in two regions that have not been subject to these influences. Genetic differentiation of alewife populations was strongest in the Bay of Fundy. Bottleneck tests revealed evidence of demographic bottlenecks in all of the alewife populations. Lastly, our results indicated that hybridization between alewife and blueback herring is common.     

Food and habitat partitioning between young-of-year alewives and rainbow smelt in southeastern Lake Ontario

Synopsis Thermal and depth distributions, diets and time of feeding of young-of-year (YOY) alewives and YOY rainbow smelt were compared for evidence of resource partitioning in southeastern Lake Ontario. YOY alewives were largely epilimnial during August and September, but moved toward the bottom during fall turnover. Alewives were most abundant in the warmest available water. YOY rainbow smelt were concentrated at depths between 10 and 30 m in August and September, but moved into deeper water at fall turnover. Depth distribution of YOY smelt was correlated with temperatures of 8–12°C Both species fed predominantly during day on zooplankton during August and September. Cyclopoid copepods were the most common prey, but bosminids, eubosminids, and occasionally calanoid copepods were frequently eaten. As YOY rainbow smelt grew (> 60 mm), they consumed more Mysis relicta and amphipods, which became the major prey of rainbow smelt by November. YOY alewives consumed mostly zooplankton in all months. Diet overlap of the two species was greatest in warm water (> 12.0° during October (94.3% similarity) and August (80.0% similarity) and lowest in November (16.9% similarity). Positive size-selection on zooplankton was found in all months for YOY rainbow smelt, but only in late September through November for YOY alewives. Thus, during thermal stratification, the species were spatially segregated by water temperature but had a high degree of overlap in time of feeding and types of prey eaten. In contrast, after fall turnover there was a greater separation in diet but a higher overlap in habitat use.     

Quantifying alosine prey in the diets of marine piscivores in the Gulf of Maine

The objectives of this work were to quantify the spatial and temporal distribution of the occurrence of anadromous fishes (alewife Alosa pseudoharengus, blueback herring Alosa aestivalis and American shad Alosa sapidissima) in the stomachs of demersal fishes in coastal waters of the north‐west Atlantic Ocean. Results show that anadromous fishes were detectable and quantifiable in the diets of common marine piscivores for every season sampled. Even though anadromous fishes were not the most abundant prey, they accounted for c. 5–10% of the diet by mass for several marine piscivores. Statistical comparisons of these data with fish diet data from a broad‐scale survey of the north‐west Atlantic Ocean indicate that the frequency of this trophic interaction was significantly higher within spatially and temporally focused sampling areas of this study than in the broad‐scale survey. Odds ratios of anadromous predation were as much as 460 times higher in the targeted sampling as compared with the broad‐scale sampling. Analyses indicate that anadromous prey consumption was more concentrated in the near‐coastal waters compared with consumption of a similar, but more widely distributed species, the Atlantic herring Clupea harengus. In the context of ecosystem‐based fisheries management, the results suggest that even low‐frequency feeding events may be locally important, and should be incorporated into ecosystem models.     

Feeding Ecology of Northeast Atlantic Mackerel,Norwegian Spring-Spawning Herring and Blue Whiting in the Norwegian Sea

The Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and Northeast Atlantic (NEA) mackerel (Scomber scombrus) are extremely abundant pelagic planktivores that feed in the Norwegian Sea (NS) during spring and summer. This study investigated the feeding ecology and diet composition of these commercially important fish stocks on the basis of biological data, including an extensive set of stomach samples in combination with hydrographical data, zooplankton samples and acoustic abundance data from 12 stock monitoring surveys carried out in 2005–2010. Mackerel were absent during the spring, but had generally high feeding overlap with herring in the summer, with a diet mainly based on calanoid copepods, especially Calanus finmarchicus, as well as a similar diet width. Stomach fullness in herring diminished from spring to summer and feeding incidence was lower than that of mackerel in summer. However, stomach fullness did not differ between the two species, indicating that herring maintain an equally efficient pattern of feeding as mackerel in summer, but on a diet that is less dominated by copepods and is more reliant on larger prey. Blue whiting tended to have a low dietary overlap with mackerel and herring, with larger prey such as euphausiids and amphipods dominating, and stomach fullness and feeding incidence increasing with length. For all the species, feeding incidence increased with decreasing temperature, and for mackerel so did stomach fullness, indicating that feeding activity is highest in areas associated with colder water masses. Significant annual effects on diet composition and feeding-related variables suggested that the three species are able to adapt to different food and environmental conditions. These annual effects are likely to have an important impact on the predation pressure on different plankton groups and the carrying capacity of individual systems, and emphasise the importance of regular monitoring of pelagic fish diets.     

Foraging behaviors and the interaction of alewife,Alosa pseudoharengus,and bloater,Coregonus hoyi

Synopsis Alewife, Alosa pseudoharengus, and bloater, Coregonus hoyi, are common planktivores in Lake Michigan. Both alewife and bloater use a variety of feeding modes. Alewives can filter, gulp and particulate feed; bloaters can only gulp and particulate feed. We examined handling time per prey and probability of capture for alewife and bloater particulate feeding on Mysis relicta. Using these estimates and available data for filtering alewives, cost curves were derived for alewife and bloater particulate feeding and for alewife using all three modes of feeding. Alewives filter small prey relative to their own body size and particulate feed on larger prey. Feeding mode appears to be dependent on prey size and density and shifts in feeding mode are apparently based on maximizing biomass eaten per time. The ability to filter confers a competitive advantage on alewife when small prey are abundant as they were in the mid 1960s in Lake Michigan. If the zooplankton are large, bloater young-of-year do not suffer this relative disadvantage. In fact, large bloaters can consume prey on the bottom not available to alewife. This shifting competitive balance may explain, in part, the observed dynamics of alewife and bloater.     

Diel variation in density, length composition, and feeding activity of juvenile alewife, Alosa pseudoharengus Wilson, and blueback herring, A. aestivalis Mitchill, at near-surface depths in a hydroelectric dam impoundment

Catches ofjuvenile blueback herring in near-surface (0 to 1.5 m depth) waters, although greater at night than during the day, did not exhibit a strict negative phototropism because catches increased significantly with increasing illumination level during the forenoon and decreased with decreasing illumination during the afternoon. Juvenile alewife were absent from near-surface waters during daylight. Feeding activity by blueback herring increased between dawn and dusk and ceased or slowed overnight but was not strictly positively phototropic. Low power (1-β) of statistical tests due to high sampling variability and low (in hindsight) sample sizes precluded conclusions about the absence of die1 and spatial differences in the pattern of density, length composition, and of feeding activity of juvenile Alosa in those cases where the null hypothesis could not be rejected. Acceptable statistical power would require substantially increased (perhaps impractically so) sample sizes aided by an increase in a (probability of a type I error) from 0.05 to 0.1.     

Feeding habits of the blue shark, Prionace glauca, and salmon shark, Lamna ditropis, in the transition region of the Western North Pacific

We describe the feeding habits of 70 blue sharks (Prionace glauca) and 39 salmon sharks (Lamna ditropis) caught at 0–7 m depth at night by research drift gillnets in the transition region of the western North Pacific during April–May of 1999 and 2000. Blue sharks of 50–175 cm total length fed on a large variety of prey species, consisting of 24 species of cephalopods and 16 species of fishes. Salmon sharks of 69–157 cm total length fed on a few prey species, consisting of 10 species of cephalopods and one species of fish. Important prey for the blue sharks were large, non-active, gelatinous, meso- to bathypelagic cephalopods (e.g., Chiroteuthis calyx, Haliphron atlanticus, Histioteuthis dofleini and Belonella borealis) and small myctophid fishes. Important prey for the salmon sharks were mid-sized, active, muscular, epi- to mesopelagic squids (e.g. Gonatopsis borealis, Onychoteuthis borealijaponica and Berryteuthis anonychus). Our results suggest that blue sharks feed on cephalopods mainly during the daytime when they descend to deep water. Salmon sharks may feed opportunistically with no apparent diurnal feeding period. Blue sharks and salmon sharks have sympatric distribution in the transition region in spring; they have different feeding habits and strategies that reduce competition for food resources.     

Mechanisms of prey selection by predaceous stoneflies: roles of prey morphology,behavior and predator hunger

Summary Laboratory feeding experiments using Hesperoperla pacifica (Banks), Perlidae, and Megarcys signata (Hagen), Perlodidae, as predators and Baetis tricaudatus Dodds and Ephemerella altana Allen as prey indicate a strong effect of prey morphology and mobility and predator hunger on prey selection by stoneflies. Knowledge of both dietary composition and feeding behavior was necessary to fully understand prey selection by these stoneflies.Fasted stoneflies presented with live prey ate more E. altana while satiated stoneflies ate approximately equal numbers of the two mayfly species. This pattern of dietary composition was the result of a reduction of attack frequency on the slower swimming E. altana with predator satiation and a continued high attack rate on B. tricaudatus regardless of recent feeding history. In contrast, fasted H. pacifica fed fresh frozen mayflies ate more B. tricaudatus indicating the importance of differences in prey mobility in controlling dietary composition.The high degree of similarity in patterns of feeding and mechanisms underlying those patterns for H. pacifica and M. signata suggest that they may be using similar rules for choosing mayfly prey and we suggest that mayfly prey are ranked by stoneflies on the basis of handling times. A general mechanistic model for stoneflies feeding on mayflies is presented and discussed.     

The influence of feeding behaviour on growth of Atlantic cod (Gadus morhua,Linnaeus, 1758) in the North Sea

The objective of this study was to resolve key mechanisms driving individual growth patterns of Atlantic cod (Gadus morhua). Growth dynamics were analysed by linking growth patterns with stomach content composition and environmental temperature. Samples were collected in August/September of the years 2009, 2010 and 2011 in the north‐eastern part of the central North Sea. Prey selection was assessed by identification of individual prey items in the stomach content to species. Ten feeding groups were identified consisting of individuals with one prey type dominating their stomach contents (≥75% by mass), of which six were used for growth analyses: “Sandeel”, “Clupeids”, “Norway pout”, “Flatfishes”, “Crustaceans” and “Brittle stars”. For each group, growth patterns were estimated based on measures of otolith growth increments. The stomach contents showed that cod as a species are opportunistic in their prey selection, but at the same time indicated that the total, broad feeding niche width of the population is dominated by individual diet specialization and that many individuals temporally show a preference for a particular prey type. The contribution of invertebrates and particularly crustaceans decreased with increasing cod size, whereas that of fish and predominantly herring increased. Prey type had a significant effect on growth, while temperature had no effect. Slowest growth was observed in the cod group preying on sandeel, while cod preying on Norway pout showed the fastest growth. No significant difference was observed between groups preying on brittle stars, crustaceans, flatfishes and herring. Growth in the year before capture did however not differ between any of these groups. Across sampling years, growth chronology patterns were similar but not significantly influenced by temperature.     

Zooplankton grazing on Phaeocystis: a quantitative review and future challenges

The worldwide colony-forming haptophyte phytoplankton Phaeocystis spp. are key organisms in trophic and biogeochemical processes in the ocean. Many organisms from protists to fish ingest cells and/or colonies of Phaeocystis. Reports on specific mortality of Phaeocystis in natural plankton or mixed prey due to grazing by zooplankton, especially protozooplankton, are still limited. Reported feeding rates vary widely for both crustaceans and protists feeding on even the same Phaeocystis types and sizes. Quantitative analysis of available data showed that: (1) laboratory-derived crustacean grazing rates on monocultures of Phaeocystis may have been overestimated compared to feeding in natural plankton communities, and should be treated with caution; (2) formation of colonies by P. globosa appeared to reduce predation by small copepods (e.g., Acartia, Pseudocalanus, Temora and Centropages), whereas large copepods (e.g., Calanus spp.) were able to feed on colonies of Phaeocystis pouchetii; (3) physiological differences between different growth states, species, strains, cell types, and laboratory culture versus natural assemblages may explain most of the variations in reported feeding rates; (4) chemical signaling between predator and prey may be a major factor controlling grazing on Phaeocystis; (5) it is unclear to what extent different zooplankton, especially protozooplankton, feed on the different life forms of Phaeocystis in situ. To better understand the mechanisms controlling zooplankton grazing in situ, future studies should aim at quantifying specific feeding rates on different Phaeocystis species, strains, cell types, prey sizes and growth states, and account for chemical signaling between the predator and prey. Recently developed molecular tools are promising approaches to achieve this goal in the future.     

Feeding ecology of mackerel and dietary overlap with herring in Icelandic waters

The Northeast Atlantic mackerel (Scomber scombrus) has been extending its summer feeding distribution north and west, including around Iceland, since around 2006. The objective of this study is to quantify the weight gain and total food consumption of mackerel and to evaluate the food competition between mackerel and herring (Clupea harengus) feeding in the marine ecosystem around Iceland during the summers 2009–2011. Mackerel feeding in Icelandic waters gained around 43% on average in weight during these summers. Based on swept-area abundance estimates of mackerel from an international survey in 2011 and available estimates of food conversion efficiency in mackerel, the weight gain in Icelandic waters in 2011 corresponded to a total consumption of around 3.4 (2.4?4.5) million tonnes. Overall, 98% of 2314 mackerel, 91% of 398 Icelandic summer-spawning herring and 96% of 424 Norwegian spring-spawning herring stomachs, collected over the summers 2009?2011, contained food. The mean weight of the stomach content of mackerel was higher than for herring in all the years. While the stomach content weight of mackerel was generally highest in southeastern and southwestern areas, it was highest for herring in western, eastern and northern areas. Analysis of stomach contents showed that Copepoda were the most important food of mackerel in most areas, while Copepoda and Euphausiacea were the most important food items for herring. Fish prey contributed a higher proportion in stomachs of mackerel than herring, although relatively low for both species.     

Variation in diet of yellow perch (Perca flavescens) in a Quebec reservoir

We determined the diet of 1 to 1 1/2 a old yellow perch (Perca flavescens) in a Quebec reservoir, relative to occurrences of available prey species and size classes of prey. We used Schindler-Patalas trap samples taken over four 24-h intervals between June and September 1981 to determine size distribution of available prey species. Relative abundances and size distribution of ingested prey species were determined from examination of gut contents of perch trapped by gill nets during the same time intervals. Electivity values of different prey species and of different size classes of prey were determined. Larger zooplankton prey (e.g.Epischura andLeptodora) were generally preferred but there was considerable variability in diet among individual fish that cannot be explained by patterns of prey availability. Within particular size classes of prey, perch have definite preferences, e.g. when perch consume small prey, they preferBosmina to other similar-sized prey. These results are discussed in relation to theories attempting to describe and predict feeding patterns of planktivorous fish species.Deceased, June 6, 1983     

Relationship between feeding of blueback herring and the zooplankton community of a Texas reservoir

Following the introduction of blueback herring (Alosa aestivalis), we examined herring food habits and the crustacean zooplankton community in Lake Theo, a 30-hectare reservoir located on a tributary of the Red River in north Texas. Prior to the introduction in spring, 1982, the reservoir contained an established fish community dominated by centrarchids. Blueback herring stomachs and zooplankton were sampled quarterly from summer, 1982 through winter, 1985. Cladocerans accounted for 89.4% of the zooplankton consumed by herring. Median lengths of cladocerans and copepods in the herring diet were significantly greater than those in the reservoir. No appreciable changes in lengths of cladocerans and copepods in the reservoir were observed after blueback herring introduction, but the zooplankton community shifted from cladoceran to copepod domination.     

Differences in growth and survival between cod Gadus morhua and herring Clupea harengus early stages co‐reared at variable prey concentrations

It was hypothesized that the survival and growth strategies of herring Clupea harengus, displaying a flexible reproductive activity, are adapted to coping with longer periods of prey deprivation (i.e. more variable prey availability), in contrast to cod Gadus morhua, which are adapted to match growth and survival at high prey concentrations. Experimental larval growth and survival data for the two naturally co‐occurring species reared either in separate tanks or in combination are presented to test this hypothesis. Natural zooplankton was supplied either ad libitum or in a periodically restricted manner to mimic natural suboptimal conditions. Periodically restricted feeding significantly reduced initial growth of G. morhua larvae co‐reared with C. harengus, while no such initial effect was seen for co‐reared C. harengus. Overall survival of G. morhua was higher when reared together with C. harengus (32 v. 24%), while C. harengus had higher survival without the presence of G. morhua (59 v. 44%), indicating that both species were affected by higher densities of G. morhua larvae. Furthermore, the final survival in G. morhua was inversely related to average final size, while in C. harengus an opposite trend was observed. How potential behavioural interactions may drive the present results are discussed and contended that a better insight into field vital rates may be gained from further exploration of co‐rearing experiments.     

Spatial and temporal variations in the diet of nototheniid fish in McMurdo Sound,Antarctica

Specimens of 4 species of Antarctic fish were captured at different locations in McMurdo Sound during the early summer, and for one species also during late winter. Stomach contents were analysed to examine resource utilization across species, at different locations, and between late winter and early summer. The results are consistent with earlier findings that there is a gradation in resource utilization across these species.T. pennelli andT. bernacchii tend to take predominantly benthic crawling prey, though they also take prey from the water column.T. hansoni andT. nicolai tend to take more prey from the water column, a tendency which can be related to the visual feeding vector of these species. Substantial differences in diet for the same species captured in different locations indicated significant flexibility in prey selection which would allow utilization of spatial and temporal fluctuations in prey availability. Successful feeding byT. bernacchii in late winter is a further indication that this species can feed non-visually and supports the notion that non-visual feeding mechanisms are likely to be of importance in the biology of the Antarctic fishes.deceased