Interannual and regional variability in distribution and ecology of juvenile pollock and their prey in frontal structures of the Bering Sea

The distribution, size, length-specific weight, growth, and feeding of age-0 walleye pollock (Theragra chalcogramma) were examined along with their prey distribution patterns in two contrasting transects over a 4-year period (1994–1997) in relation to biophysical properties of frontal regions around the Pribilof Islands, Bering Sea. There were significant interannual differences in catch of age-0 pollock, but transect and habitat differences (inshore vs. front vs. offshore) were not significant for either catch or size of pollock. There were significant variations in length-specific weight and growth of pollock, but the trends were inconsistent. Copepods dominated the zooplankton biomass in all habitats and years; there were no consistent differences in the densities of the dominant zooplankton taxa among the habitats. There were, however, strong habitat and transect differences in juvenile pollock diet, particularly for the larger and presumably rarer prey taxa (euphausiids, chaetognaths, fish). We did not find any evidence that occupying a particular habitat was beneficial to young pollock, although other factors (e.g. bioenergetic advantage and predation refuge) that we did not examine here could have been more variable and critical to pollock survival. In a physically dynamic system such as the Pribilof Islands, age-0 pollock may need to continuously search for optimal conditions of high prey availability and low predation pressure.     

Feeding ecology of the deep-water blue–red shrimp Aristeus antennatus (Decapoda: Aristeidae) in the Greek Ionian Sea (E. Mediterranean)

The feeding habits of the deep-sea blue–red shrimp Aristeus antennatus were determined based on the analysis of 1047 stomach contents, sampled in the Greek Ionian Sea (E. Mediterranean). The diet of this economically and biologically important decapod was studied in relation to the season, size class and sex. The diet of A. antennatus consisted of 54 different prey categories, and belonged mainly to smaller crustaceans (e.g. natantian decapods, euphausiids, tanaidaceans), molluscs, polychaetes, chaetognaths and, to a lesser extent, fishes. The above prey categories consisted of 71–82% of the relative abundance and total occurrence for males and 61–81% for females. Females seemed to be better fed than males (stomach fullness, food quality). A. antennatus displayed a highly diversified diet and the different feeding patterns were discussed. Diet composition showed slight seasonal fluctuations. The observed slight differences on A. antennatus diet among the western, central and eastern Mediterranean could be attributed to the more oligotrophic character of the eastern part of the basin. The principal factors driving the changes in the feeding strategy of this decapod among the seasons are the increased energy demands related to sexual requirements and the food availability in the marine environment. The ontogenetic changes in the shrimp's diet were relatively clear. Larger individuals exhibited selecting prey with a good swimming capacity (e.g. fishes), while the smaller individuals consumed prey with low mobility (e.g. copepods, ostracods).     

Diet composition and feeding behaviour of juvenile Greenland halibut (Reinhardtius hippoglossoides) in the Svalbard area

The diet of trawl-captured juvenile Greenland halibut (Reinhardtius hippoglossoides Walbaum) from three locations on the western and northern coasts of Svalbard, Norway, in December 1995 and January 1996 is described. Stomach fullness was recorded for 1216 fish of 7 to 65 cm length, and stomach contents were analysed for 353 non-empty stomachs. The diet differed only slightly between the sampling areas and no differences were found between males and females. The overall percentage of empty stomachs (PES) was comparable to other nursery areas and lower than recordings from feeding and spawning areas. PES decreased and prey size increased as predator length increased. Fish and crustaceans dominated the diet, the most important prey species being Atlantic cod (Gadus morhua), polar cod (Boreogadus saida) and northern shrimp (Pandalus borealis). The relative importance of fish and crustaceans, respectively, was independent of predator length. However, a size-dependent variation in preferred prey was found, as smaller fish preyed upon small crustaceans and polar cod while larger individuals displayed a preference for northern shrimp, juvenile Atlantic cod, and other larger fish. Finally, there was a close resemblance between the length distribution of prey species from the trawl and from the stomachs.     

Abundance,distribution, and feeding patterns of juvenile coho salmon (Oncorhynchus kisutch) in the Juan de Fuca Eddy

The Juan de Fuca Eddy is a seasonal, counter-clockwise gyre off the mouth of the Strait of Juan de Fuca between Washington, USA and British Columbia, Canada that may provide favorable feeding habitat for juvenile coho salmon (Oncorhynchus kisutch) during their early marine existence. In late September 2002, physical and biological sampling was conducted along two transects of the eddy region. Surface rope trawling was conducted to capture juvenile salmon and other nekton, along with bongo and neuston net tows to examine potential mesozooplanktonic salmon prey. Presence of the Juan de Fuca Eddy was confirmed with vertical water profiles. In addition, nutrient and chlorophyll a concentrations collected from 3-m depth were within the range observed in previous studies within the eddy region. In the mesozooplankton community, euphausiids, chaetognaths, and decapod megalopae were common. In the diet of juvenile coho salmon, euphausiids and decapod megalopae were dominant by percent number, and larval and juvenile fish were dominant by percent weight. Feeding intensity (percent body weight) based on stomach contents was variable, but not significantly different among stations. To compare the Juan de Fuca Eddy region with an upwelling area, we sampled along a transect off La Push (LP), Washington, USA which is south of the eddy. The eddy region was found to be less productive than the LP transect. Nutrients were lower, chlorophyll a concentrations were higher, and zooplankton abundance was generally higher along the LP transect than in the eddy region. In addition, more juvenile coho salmon were captured from the LP transect than the eddy region. Prey items in stomachs of salmon from the LP transect were heterogeneous compared to those from the eddy region. Feeding intensity along the LP transect was slightly lower and more variable than in the eddy region, and differences in feeding intensity among LP stations were significant. In addition, feeding intensities among stations nested within regions were significantly different.     

Revisiting Peruvian anchovy (Engraulis ringens) trophodynamics provides a new vision of the Humboldt Current system

The Peruvian anchovy or anchoveta (Engraulis ringens) forages on plankton and is a main prey for marine mammals, seabirds, fish, and fishers, and is therefore a key element of the food web in the Humboldt Current system (HCS). Here, we present results from the analysis of 21,203 anchoveta stomach contents sampled during 23 acoustic surveys over the period 1996–2003. Prey items were identified to the genus level, and the relative dietary importance of different prey was assessed by determination of their carbon content. Variability in stomach fullness was examined relative to the diel cycle, the distance from the coast, sea surface temperature, and latitude, using generalized additive models (GAMs). Whereas phytoplankton largely dominated anchoveta diets in terms of numerical abundance and comprised >99% of ingested prey items, the carbon content of prey items indicated that zooplankton was by far the most important dietary component, with euphausiids contributing 67.5% of dietary carbon followed by copepods (26.3%). Stomach fullness data showed that anchoveta feed mainly during daytime between 07h00 and 18h00, although night-time feeding also made a substantial contribution to total food consumption. Stomach fullness also varied with latitude, distance from the coast, and temperature, but with substantial variability indicating a high degree of plasticity in anchoveta feeding behaviour. The results suggest an ecological role for anchoveta that challenges current understanding of its position in the foodweb, the functioning of the HCS, and trophic models of the HCS.     

Feeding ecology of the mud shrimp Solenocera melantho in the East China Sea

The feeding habits of the mud shrimp Solenocera melantho were studied in the East China Sea by analysing 720 stomach contents and comparing diet composition and prey diversity among seasons, sexes and size classes. Feeding activity was linked to season and ovarian condition. The stomach fullness was high during spring and summer and low in fall. Females with advanced ovaries also displayed low stomach fullness, which suggests that feeding activity is affected by the reproductive cycle. The diet of S. melantho consisted of 42 different prey categories, primarily smaller crustaceans, Foraminifera, polychaetes, mollusks and fishes (larvae and eggs). Crustacea,Foraminifera and polychaetes together constituted the dominant prey groups, accounting for 75% of total prey abundance and >50% of total prey occurrence. Diet composition differed among seasons between sexes and size classes. Females and males consumed the same prey items but with different orders of importance. In terms of body size, the small shrimps preferred relatively small food items, such as Foraminifera and algae, whereas larger shrimps preferred polychaetes and crustaceans. Trophic diversity varied among the seasons within both sexes and size classes, with the highest values being observed in fall. Niche overlap was high within both sexes and size classes among seasons (0.6051–0.8740).     

Feeding of the Norwegian spring spawning herring Clupea harengus (Linne) at the different stages of its life cycle

The aim of the research was to investigate the diet of herring at different stages of its life cycle. For that purpose feeding of 0-group and immature herring in the Barents Sea, as well as of mature fish from the Norwegian Sea, was studied. 0-Group herring was sampled in the Barents Sea in August–September 2002–2005 during the international 0-group and trawl-acoustic survey of pelagic fish, as well as during the trawl-acoustic survey of demersal fish in November–December 2003–2004. Stomach samples of immature herring (1–3 years) were collected in late May and early of June 2001 and 2005 in the south-western part of the Barents Sea during the trawl-acoustic survey for young herring. Stomach samples of mature herring were collected in the Norwegian Sea in 1996, 1998, 1999, 2001, and 2002 in the course of the international trawl-acoustic survey of pelagic fish. Feeding intensity of herring of all age groups varied considerably between years and this was probably associated with availability and accessibility of their prey. The 0-group herring was found to have the most diverse diet, including 31 different taxa. In August–September, copepods, euphausiids, Cladocera, and larvae Bivalvia were most frequent in the diet of 0-group herring, but euphausiids and Calanus finmarchicus were the main prey taken. In November–December, euphausiids and tunicates were major prey groups. It was found that C. finmarchicus in the diet of 0-group herring was replaced by larval and adult euphausiids with increasing fish length. C. finmarchicus was the principal prey of immature herring and dominated in the diet of both small and large individuals and mainly older copepodites of C. finmarchicus were taken. Larval and adult euphausiids were found in stomachs of immature herring as well, but their share was not large. The importance of different prey for mature herring in the Norwegian Sea varied depending on the feeding area and length of the herring. On the whole C. finmarchicus and 0-group fish were the most important prey for mature herring diet, but fish prey were only important in a small sampling area. Hyperiids, euphausiids, tunicates, and pteropods were less important prey, and in 2002 herring actively consumed herring fry and redfish larvae.     

Physical and biological factors influencing the spatial distribution of age-0 walleye pollock (Theragra chalcogramma) around the Pribilof Islands, Bering Sea

The waters around the Pribilof Islands, in the southeast Bering Sea, are a main nursery area for age-0 pollock. Each summer, the islands are surrounded by a well-mixed inshore region, separated from a stratified offshore region by a frontal zone. To study the spatial distribution of age-0 pollock around this frontal structure in relation to physical and biological factors that are likely to influence it, such as advection, age-0 pollock feeding, and predation, samples were collected during September of four consecutive years, 1994–97, along two transects. Samples collected included water column hydrography and currents, acoustic backscatter, and groundfish predator density.Our analysis suggested that different mechanisms may be involved in controlling age-0 pollock distribution north and south of the islands. On the shelf area north of the islands, high age-0 pollock density was significantly associated with areas of high potential for growth only in years or portions of the frontal transect in which predator numbers were relatively low, indicating the importance of predation in controlling fish distribution in this area. In contrast, south of the islands, age-0 pollock distribution was associated more with prey availability, which appeared to be determined by vertical spatial overlap between predators and prey. Moreover, south of the islands, the stronger geostrophic currents, typical of the slope region, were more likely to affect the overall standing biomass of juvenile pollock, by constantly advecting fish away from the area.     

Food and feeding of small fish in the Rakaia River,New Zealand

Benthic macroinvertebrates and fish species were collected at monthly intervals during a 12‐month period, from 3 areas of the lower Rakaia River. The composition and abundance of the benthos and stomach contents of the fish were analysed for seasonal trends, food niche breadth and overlap between pairs of fish species, and overlap between the benthos and the diet of each fish species. The diets of bluegilled bully (Gobiomorphus hubbsi), upland bully (G. breviceps), juvenile longfinned eel (Anguilla dieffenbachii), Galaxias brevipinnis, G. paucispondylus, and juvenile brown trout (Salmo trutta) were similar to the proportions of prey species in the benthos. Deleatidium and chironomid larvae dominated the benthos in all seasons and formed the majority of food items in the diet of these species. Food niche overlap between these species was high, indicating potential competition, but preferred habitat and feeding habit differences plus low fish population density and abundance of main prey items probably eliminate the occurrence of any serious competition. The diet of the other fish species differed from this pattern. The common bully (Gobiomorphus cotidianus) ate proportionally more chironomid larvae and fish eggs than occurred in the benthos; torrentfish (Cheimarrichthys fosteri) ate proportionally more chironomid larvae than occurred in the benthos; and quinnat salmon (Oncorhynchus tshawytscha) depended largely upon prey species of terrestial origin, such as adult Deleatidium and dipterans.     

Altered feeding habits and strategies of a benthic forage fish (Fundulus heteroclitus) in chronically polluted tidal salt marshes

Responses in feeding ecology of a benthic forage fish, mummichogs (Fundulus heteroclitus), to altered prey resources were investigated in chronically polluted salt marshes (the Arthur Kill-AK, New York, USA). The diet niche breadth of the AK populations of mummichogs was significantly lower than that of the reference population, reflecting reduced benthic macroinfaunal species diversity. Most of the AK populations also had 2-3 times less food in their gut than the reference population. This disparity in gut fullness among the populations appeared to be partly due to ingested prey size shifts; some of the AK populations ingested fewer large prey than the reference population. Furthermore, benthic assemblages were strongly associated with sediment-associated mercury; gut fullness of the AK populations also significantly decreased with increasing mercury body burdens. These results indicate that chronic pollution may have directly (chemical bioaccumulation) and indirectly (reduced prey availability) altered the feeding ecology of mummichogs.     

鮸状黄姑鱼早期发育阶段的摄食与生长特性

1997年4－5月,在集美大学水产学院海水育苗试验场,采用生态学方法对人工培育的状黄姑鱼仔、稚、幼鱼的援食和生长特性进行分析。结果表明,在人工培育条件下,仔、稚、幼鱼的摄食率达97.9％,摄食量占体重的1．4％－23．4％,日摄食量占体重的36．47％－6519％;摄食具明显的昼夜节律,黄昏和早晨为摄食高峰;对较大个体的饵料生物有明显的选择性;饵料密度对摄食量有一定影响。摄食量与体重的关系式为y=0.1327x＋0．5613,全长与日龄的关系式为LT=2.5799eg.g516D,体重与日龄的回归方程为W=0．0537e‘.1786D,全长与体重的回归方程为W＝0．0042L。     

花鲈仔、稚、幼鱼摄食习性与生长的研究

分析了花鲈仔、稚、幼鱼的摄食习性与生长.结果表明,在水温为15.5～16.5℃时,花妒仔鱼孵出约140h左右开口摄食,开口饵料为小型臂尾轮虫.全长10mm左右的仔鱼可摄食卤虫幼体,全长11mm左右的个体可摄食枝角类.对431尾仔、稚、幼鱼观察结果,在实验条件下其摄食率高达99.1%,胃饱满系数波动于2.38%～16.48%之间,日摄食指数在45%～60%.其摄食强度具明显的昼夜节律,以16:00～20:00胃饱满度最高.仔、稚鱼夜间基本不摄食,部分幼鱼个体少量摄食.仔、稚、幼鱼个体间生长速度具有一定的差异性.其体重与摄食量的关系符合直线方程y=0.1018+8.3261×10-2x;全长与体重的相关关系可用ω=1.6473×10-3L3.4743表示,全长与日龄的关系式为L_t=5.5242e1.9681×10-2D;体重与日龄的回归方程为ω=0.5836e6.9208×10-2D.     

Changes in the diet and feeding of the hake Merluccius merluccius at the shelf-break of the Balearic Islands: Influence of the mesopelagic-boundary community

Short spatio–temporal variations in the feeding intensity and the diet of the European hake, Merluccius merluccius, together with the abundance of their potential prey were studied between August 2003 and June 2004 at two locations, northwest (Sóller) and south (Cabrera), off the island of Mallorca (Balearic Islands, Western Mediterranean) at depths between 150 and 750 m. The two areas present different oceanographic conditions. Hake was mainly distributed along the shelf-slope break and the upper slope (between 166 and 350 m) where recruits (TL<18 cm) were dominant. The hake's diet varied as a function of size. Recruits fed mainly on micronektonic prey, and the diet was influenced primarily by seasonality, with two dietary patterns (identified by MDS analyses) corresponding to August–September 2003 (summer) and to November 2003/February–April 2004 (autumn–winter). The summer pattern was consistent with a thermally stratified water column, while November and April were consistent with homogenized temperature and salinity throughout all the water column. The main prey of recruits were the euphausiid Meganyctiphanes norvegica and the midwater fish Maurolicus muelleri in autumn–winter and myctophids (mainly Ceratoscopelus maderensis) in summer. In contrast to recruits, the geographic factor (NW vs. S) was the main factor influencing the diets of post-recruits (TL between 18 and 21.9 cm) and adults (TL?22 cm). Hake recruits (and to a lesser extent post-recruits) and their preferred prey occupied different depth ranges during daylight periods. Meganyctiphanes norvegica and Ceratoscopelus maderensis were, for instance, distributed as much as 500 m deeper than hake that had eaten them. All these trends were especially obvious at NW, an area with a more abrupt slope and with a greater influence by northern winter intermediate water (WIW) inflow in early spring than the S area. These factors probably enhanced micronekton aggregation in April, when feeding intensity (stomach fullness) increased among recruits and post-recruits only at NW. All these factors may have a crucial role in the diet, distribution and probably recruitment success of small hake. Biological factors were also important in trophic shifts in the diet and feeding of hake. Multi-linear regression models pointed to a trend of higher fullness with higher hepato-somatic index (HSI). Therefore greater food consumption by hake may enhance its metabolic condition. Within the framework of shelf-break and slope ecology, we show how the ‘boundary’ mesopelagic community inhabiting the middle slope sustains the trophic requirements of hake, a species distributed at shallower depths along the shelf-slope break. Mesopelagic euphausiids and myctophids are often found in the diets of shelf-break fish. Because the boundary mesopelagic community is distributed worldwide, the high levels of fish biomass often found at shelf-slope breaks could be sustained trophically by deeper, offshore mesopelagic communities, an inverse energy transfer from deep to shallow-water marine ecosystems.     

The diet of mesopelagic fish from the Pacific coast of Hokkaido,Japan

The diet of at least 28 species of mesopelagic fish from the Pacific coast of Hokkaido was examined. The dominant family was the Gonostomatidae (42%) which was represented by five species. The most abundant species wasCyclothone atraria which together with the other species of this genus preyed predominantly on copepods. Euphausiids and copepods were dominant in the diet ofGonostoma gracile. The next most abundant family was the Myctophidae (32%) which was represented by seven species. The dominant species,Stenobrachius nannochir, preyed mainly on copepods. Copepods were also the dominant food item of the other myctophids except forLampanyctus jordani which fed mainly on euphausiids. The other important family was the Bathylagidae (21%).Leuroglossus schmidti was the dominant species and its diet was more diverse with ostracods, copepods, molluscs and larvaceans being the most important food items.Bathylagus ochotensis had a similar diet. Copepods were the most important food items for all but a few species and their occurrence in the fish stomachs was related to the known vertical distribution of both predators and prey. Ostracods and euphausiids were also important prey items, the latter especially in large fish species. Molluscs and larvaceans were restricted to the two species of the family Bathylagidae.     

Effects of sample size on numerical estimates of diel prey consumption in a fish population

Numerical data based on stomach content analysis of the zooplanktivorous freshwater fish, Retropinna semoni, were used to examine the effect of fish sample size on mean counts of dominant prey items. Fifty adult R. semoni were collected from throughout the open‐water of Lake Benanee, Australia at each of five times over a diel period. Bootstrapping was used to generate confidence intervals around sample means, and markedly more accurate means were obtained from samples collected in the day than the night. High variation in night samples was the by‐product of a diurnal feeding regime. Traditional sample sizes of 10 to 15 stomachs resulted in reasonable confidence intervals of sample means derived from collections on the first day, corresponding to uniform feeding patterns in the population. However, increased sample sizes were required to describe more complex feeding behaviour on the second day, when a proportion of the population switched to an alternative prey source.     

Evaluation of food competition and resource partitioning of recruiting fish with permanent residents in a seagrass habitat

ABSTRACT

Recruiting King George whiting Sillaginodes punctatus were studied to assess the potential for food competition with permanent resident fish species in a nursery habitat. Marine migrant post larval S. punctatus (<60?mm TL) consumed primarily harpacticoid copepods and had high (>0.6) diet overlap with permanent resident fish species Favonigobius leteralis and Stigmatopora nigra. Food electivity index indicated that S. punctatus juveniles preferred harpacticoid copepods and amphipods, while juvenile Heteroclinus adelaide and Gymnapistes marmoratus migrating to the nursery habitat targeted larger prey such as amphipods. Preference for larger prey by H. adelaide and G. marmoratus species coupled with differences in prey composition in the stomach was due to mouth size and feeding habits, resulting in different food preferences to S. punctatus. The whiting showed an ontogenetic shift in diet with early settlers (>60?mm TL) consuming less copepods and more amphipods, while previous year recruits (>120?mm TL) consumed polychaete worms. This study indicates that competition for food resources between the new recruiting S. punctatus juveniles and permanent resident juveniles is reduced through differences in temporal and spatial feeding behaviours, mouth morphology, and ontogenetic shift in prey consumption.     

The feeding and diet of the deep-sea shrimp Aristeus antennatus off the Balearic Islands (Western Mediterranean): Influence of environmental factors and relationship with the biological cycle

Spatio-temporal variation of feeding intensity and diet in the red shrimp Aristeus antennatus was studied at two locations around the island of Mallorca (Balearic Islands, Western Mediterraean) in August, September, and November 2003, and in February, April and June 2004 at depths between 550 and 750 m. The two areas, with different oceanographic conditions, were respectively located in the northwest (Sóller) and the south (Cabrera) of Mallorca. Off Sóller, feeding intensity of A. antennatus showed a significant increase from February to April and June 2004 in all the three size-classes studied (small shrimps: CL < 30 mm; medium: CL between 30 and 40 mm; large: CL ? 40 mm). Off Cabrera, the highest fullness was recorded in November 2003 among small and medium shrimp, while only large specimens showed patterns similar to that found off Sóller. Off Sóller, the diet of both small (CL < 34 mm) and large (CL ? 34 mm) A. antennatus was mainly influenced by season, with three dietary groups corresponding to August-September 2003, to November 2003/February 2004, and to hauls from April to June 2004. Off Cabrera, hauls (representing diets) were grouped by depth, never by season. The most remarkable seasonal shift in the diet of A. antennatus off Sóller was the increase of mesopelagic prey in April-June relative to other months. In all size categories there was an increase off Sóller in the energy intake of prey ingested from February to June 2004, an increase not found off Cabrera. Degree of digestion of mesopelagic prey indicated nocturnal feeding on mesopelagic fauna. These prey probably have a shallower depth distribution at night than found in our daylight sampling, and possible migratory movements among prey and A. antennatus at night would explain the lack of correlation between prey abundance in guts and in the environment found during daylight periods for most micronekton mesopelagic prey (euphausiids, myctophids and sergestids). Off Sóller, fullness and diet were significantly linked to temporal changes in water column productivity (e.g., Chl a readings, fluorescence) and to changes in the shrimp biology (lipid content of hepatopancreas, Gonado-somatic Index, GSI). Off Cabrera, we found a higher dependence of fullness and diet with T and S, both variables in turn related to depth. The increase of stomach fullness and dietary energy intake in pre-reproductive females from February to April-June 2004 found off Sóller, coupled with the consumption of mesopelagic prey, was parallel to a significant increase of the gonad weight (GSI, fecundity) in June. Most individuals attain gonad development in the period May-June, after two months of the peak of primary production at the surface. The strong link found between pelagic resources and reproductive processes in a deep-sea species such as the shrimp Aristeus antennatus, situated near the top of the trophic web, suggests a rapid energy flow via mesopelagic fauna between surface primary production and bathyal megabenthic communities at oligotrophic insular areas. In contrast to mainland areas off the Catalan coasts submitted to the influence of submarine canyons, around the island of Mallorca the empoverishment of benthos biomass may enhance consumption of micronektonic prey and a possible accumulation of pre-reproductive females of A. antennatus in areas (e.g., steep slopes and persistent frontal systems found off Sóller) with high zooplankton aggregations.     

Feeding Habits of the Mesopelagic Fish Gonostoma gracile in the Northwestern North Pacific

The diet of Gonostoma gracile, a numerically abundant mesopelagic fish in the Subtropical Region and the Transition Domain of the northwestern North Pacific, was examined using 520 specimens collected during June–July 1988, June 1995 and November 1995. The prey included mainly copepods, ostracods, amphipods and euphausiids. Copepods and ostracods were the most abundant, comprising approximately 70% of the total diet. There was little evidence of an ontogenetic dietary shift; Pleuromamma copepods were the most abundant prey for all size classes of fish ranging from 19 to 116 mm in standard length. The size range of prey increased with growth, but all fish sizes examined fed mainly on 1–4 mm long prey. Luminescent copepods and ostracods were the most abundant prey, suggesting that G. gracile detects its prey visually. This revised version was published online in August 2006 with corrections to the Cover Date.     

Feeding ecology,diet and field-based studies on feeding selectivity of the Cape anchovy Engraulis capensis Gilchrist

Samples collected during four cruises on board R.S. Africana were used to study the trophic ecology and feeding behaviour of Engraulis capensis in the southern Benguela region. Previous work had indicated that this species was a non-selective filter-feeding omnivore, diatoms comprising the bulk of the diet. The results of the present study reveal that anchovies selectively feed on mesozooplankton, especially calanoid copepods and euphausiids. Investigation of the feeding behaviour of the species indicates that raptorial feeding is dominant over filter-feeding and that prey appears to be selected primarily on the basis of size.     

Preliminary Observations on the Feeding Activity of Fishes during Tidal and Diel Cycles in the Loire Estuary: The Bib Trisopterus luscus L. 1758

Abstract. .Series of experimental trawls repeated over the same area during both 12 and 24 h cycles coupled with an analysis of the stomach contents of the bib demonstrated quantitative and qualitative variations in the predator's diet. The population studied feeds continuously over 24 h, the coefficient of "fullness" is relatively constant, and freshly eaten prey can be observed both during the day and at night. The proportion of brown shrimp in the food increases after high tide, especially when this occurs at night, coinciding with the shrimp's period of maximum activity. However, the overall impact of the bib on the shrimp population depends more on the abundance of the former than on variations in their individual food intake.