On the diet of the rock sole <Emphasis Type="Italic">Lepidopsetta polyxystra</Emphasis> off the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka

The bulk of diet of the rock sole Lepidopsetta polyxystra in waters of the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka from September to October 1997 was formed by polychaetes and amphipods (36.8 and 35.1% of the food bolus weight, respectively), which is typical of the feeding of this species, on the whole. The dominant consumption by L. polyxystra of polychaetes is recorded from February to June and of amphipods, from August to December. Polychaetes dominated in the diet of individuals with a length of 16–45 cm and amphipods, in the diet of individuals 46–55 cm long. The feeding migration of L. polyxystra in the study area took place at sites with an increased biomass of the accessible food benthos.     

Identifying gray whale (Eschrichtius robustus) foraging grounds along the Chukotka Peninsula, Russia, using satellite telemetry

The purpose of this study was to evaluate summer and fall residency and habitat selection by gray whales, Eschrichtius robustus, together with the biomass of benthic amphipod prey on the coastal feeding grounds along the Chukotka Peninsula. Thirteen gray whales were instrumented with satellite transmitters in September 2006 near the Chukotka Peninsula, Russia. Nine transmitters provided positions from whales for up to 81?days. The whales travelled within 5?km of the Chukotka coast for most of the period they were tracked with only occasional movements offshore. The average daily travel speeds were 23?km?day^?1 (range 9–53?km?day^?1). Four of the whales had daily average travel speeds <1?km?day^?1 suggesting strong fidelity to the study area. The area containing 95% of the locations for individual whales during biweekly periods was on average 13,027?km² (range 7,097–15,896?km²). More than 65% of all locations were in water <30?m, and between 45 and 70% of biweekly kernel home ranges were located in depths between 31 and 50?m. Benthic density of amphipods within the Bering Strait at depths <50?m was on average ~54?g wet wt m^?2 in 2006. It is likely that the abundant benthic biomass is more than sufficient forage to support the current gray whale population. The use of satellite telemetry in this study quantifies space use and movement patterns of gray whales along the Chukotka coast and identifies key feeding areas.     

Feeding ecology of dominant groundfish in the northern Bering Sea

We investigated current diets of the six most abundant benthic fish in the northern Bering Sea. Our objective was to explore feeding strategies and potential competition with other top predators as ecosystem changes occur in the northern Bering Sea ecosystem. Our approach used stomach content data collected from field sampling during spring 2006 and 2007. Calanoid copepods and ampeliscid amphipods were important prey of Arctic cod (Boreogadus saida) but in different proportions depending upon fish size, feeding location, and local environmental conditions. Snailfish (Liparidae) occupied a broad niche and fed on a variety of benthic amphipods. Arctic alligatorfish (Ulcina olrikii) and Arctic staghorn sculpin (Gymnocanthus tricuspis) consumed ampeliscid amphipods predominantly. Shorthorn sculpin (Myoxocephalus scorpius) had a less-diverse diet, with snow crab (Chionoecetes opilio) most important by weight. Finally, all Bering flounder (Hippoglossoides robustus) sampled had empty stomachs. Our results indicate that ampeliscid amphipods, which have high biomass in the central region of the northern Bering Sea, are the most important prey for the dominant groundfish in the Chirikov Basin. Generally, all dominant benthic fish in the northern Bering Sea had narrow feeding niches, except snailfish. High diet overlap was found among many of the fish species, including Arctic cod and snailfish, snailfish and Arctic alligatorfish, and Arctic alligatorfish and Arctic staghorn sculpin. These findings are consistent with a relatively short food chain for benthic fish that are for the most part specialized feeders with narrow preferences for food and may be affected by changes in benthic prey distributions.     

Abundance and Distribution of the Macrobenthic Infauna of the Gulf of Arauco,Chile

The macrobenthic infauna of the Gulf of Arauco (Central Chile), was quantitatively sampled in April 1979. A total of 81 species were identified. The infauna was greatly dominated by polychaetes. The polychaete Paraprionospio pinnata and the amphipod Ampelisca araucana accounted for ca. 45 per cent of the total infauna in terms of numbers. Numerical classification produced four site-groups and four species-groups, mostly reflecting differences in character and depth of sediment. Several community characteristics differed for these assemblages. Biomass also was dominated by polychaetes, with Pectinaria chilensis, P. pinnata, Diopatra chiliensis and Glycera americana making up 45 per cent of the total. The high numbers of the fauna (mean = 15,021 ind m⁻²) and especially the high biomass figures (mean = 21.04 g AFDW m⁻²) reported are consistent with the high productivity of the area, subject to coastal upwelling processes.     

Data on distribution and biology of poachers agonidae from the northwestern part of the Bering Sea

On the basis of materials of 1996–2003, specific features of spatial and seasonal distribution of four species of Agonidae (Percis japonica, Sarritor frenatus, S. leptorhynchus, and Aspidophoroides bartoni) in the northwestern part of the Bering Sea are considered. In this area of the studied species, P. japonica is found in catches most frequently (occurrence reaches 81.8%); the rarest here is S. leptorhynchus (0.7–7.0%). P. japonica begins to spawn in mid-July, and S. frenatus terminates spawning in the second ten-day period in August. Mass (50%) sexual maturation of female P. japonica occurs at a length of 29 cm, and of males, at 23 cm; in S. frenatus, at 24–25 and 23 cm, respectively. The individual absolute fecundity of P. japonica averages 6361 eggs, and oocyte diameter, 2.9 mm; of S. frenatus, 2848 eggs and 1.53 mm, respectively. The bulk of feeding of P. japonica is formed by polychaetes; next in importance are amphipods and caprellids. The bulk of feeding of S. frenatus is formed by amphipods; polychaetes, isopods, and euphausiids (in decreasing order) are also important in the feeding of this species.     

Distribution and some biological features of Lycodes raridens (Zoarcidae) in the western part of the Bering Sea

Based on a bottom trawl survey, it is shown that in Karaginskii and Olyutorskii bays of the western part of the Bering Sea, Lycodes raridens is a typically elittoral species, since it was recorded at depths of 52–120 m, and the majority of individuals of this species were found in the range of depths 50–100 m. The maximum concentrations of Lycodes raridens were 139 ind./km² or 98 kg/km², whereas the average values of the distribution density of this species were 7.8 ind.km² or 5.4 kg/km². In Karaginskii and Olyutorskii bays, Lycodes raridens is represented by individuals with a length of 16–86 cm, weight of 34–4510 g, at the age of 1+ to 7+, although fish with a length of 30–50 cm, weight of 100–1000 g, and age of 3+–4+ dominate. The data obtained suggest that in the autumn or autumn-winter period, the study species spawns in the western part of the Bering Sea. The dominant food of Lycodes raridens here are amphipods, polychaetes, bivalves, and decapods; by occurrence and the relative content in the stomach (% of weight), amphipods (as a rule, Melita spp.) and bivalves (Yoldia spp. and Macoma sp.) dominate. Lycodes raridens is a benthophage in which, at the early stage of the life cycle, gammarids prevail in food; with growth, its diet becomes more diverse due to bivalves, polychaetes, and decapods.     

Comparative Feeding Ecology of Two Sympatric Greenling Species, <Emphasis Type="Italic">Hexagrammos otakii</Emphasis> and <Emphasis Type="Italic">Hexagrammos agrammus</Emphasis> in Eelgrass <Emphasis Type="Italic">Zostera marina</Emphasis> Beds

Synopsis Feeding ecology was compared between sympatric greenling species, Hexagrammos otakii and H. agrammus in the eelgrass beds in Jindong Bay, Korea, from January to December. These two species had similar diets composed of crustaceans, polychaetes, gastropods and fishes; both species consumed primarily crustaceans throughout study periods. H. otakii, however, fed a greater proportion of polychaetes and fishes than H. agrammus. H. agrammus had a greater proportion of gastropods in their diets. The diet of both species underwent size-related changes; smaller individuals of H. otakii and H. agrammus consumed amphipods (gammarid amphipods and caprellid amphipods), while larger individuals of H. otakii ate polychaetes and fishes and those of H. agrammus fed mainly on gastropods and crabs. The diet of H. otakii underwent seasonal changes; H. otakii consumed mainly polychaetes and fishes during January and February 2002 but amphipods during March and May 2002. H. agrammus, however, ate mainly gastropods and crabs all seasons. H. otakii underwent also a significant diel changes that could be related to difference of prey availability. Thus the nocturnal emergence of gammarid amphipods, polychaetes and fishes explained their greater consumption by H. otakii. Dietary breadth of both species was lower in the smallest individuals (<5 cm SL) and in March and April 2002. This was due to the disproportionate dry mass attributable to the consumption of amphipods by both H. otakii and H. agrammus. Dietary overlap of both species was relatively moderate to high, in particular in <9.9 cm SL (0.62 – 0.71) from May to July 2002 (0.63 – 0.71). This is coincident with higher abundances of crabs, caridean shrimps and polychaetes in the study area, and it was assumed that these prey species were not limited resources. Higher dietary overlap was correlated with an abundance of a shared resource and did not indicate the interspecific competition between H. otakii and H. agrammus.     

Benthic–pelagic coupling: a comparison of the community structure of benthic and planktonic heterotrophic protists in shallow inlets of the southern Baltic

1. The taxonomic composition, abundance and biomass of heterotrophic protists (ciliates, heterotrophic flagellates (HF), rhizopods and actinopods) in the sediment and water column of shallow inlets of the Southern Baltic was studied under a variety of environmental conditions during 1996–1997. A shallow, highly eutrophic station and a deeper, less eutrophic station were compared.
2. Community biomass ranged from 0.12 to 0.34 μg C cm?3 in the water column and from 1.5 to 105 μg C cm?3 in the sediment. Heterotrophic protists dominated zooplankton biomass at both stations (73% and 84% mean contribution), while they were of minor importance within the zoobenthos. Expressed per unit area, benthic biomass contributed a significant part (44% and 49%) to the total heterotrophic protistan community at both stations.
3. Although the methodology for counting ciliates and HF was focussed on a high taxonomic resolution, the results reveal some general trends in the distribution of heterotrophic protists: protozooplankton biomass was dominated by flagellates (80% mean biomass contribution) at the shallow station and by ciliates (73% mean biomass contribution) at the deep station. In the benthos at both stations, ciliates were the dominant protozoans, followed by the hitherto little‐studied rhizopods (25% and 35% mean biomass contribution) and flagellates.
4. The degree of benthic–pelagic coupling differed between taxonomic groups. Benthic and pelagic communities of ciliates showed little taxonomic overlap. In contrast, many heterotrophic flagellate species were found both in the benthos and in the pelagic. These benthic–pelagic species contributed significantly to the biomass of HF in the water column. The planktonic rhizopod community consisted of a subset of those species found in the benthos.
5. The abundance of benthic and pelagic protists was positively correlated at the shallow station, but taxonomic data indicate that the direct exchange between benthic and pelagic communities was only partly responsible.     

Diet of the Antarctic starry skate Amblyraja georgiana (Rajidae, Chondrichthyes) at South Georgia (Southern Ocean)

Stomach contents were identified from 206 Antarctic starry skate (Amblyraja georgiana) that were collected during three groundfish surveys (September 2007, April 2008 and January 2009) at South Georgia, Southern Ocean. The diet of A. georgiana varied with skate size and between years. Preferred prey included fish (particularly for larger individuals) and Antarctic krill, Euphausia superba, as well as amphipods, polychaetes and other benthic fauna. The skate A. georgiana appears to be an opportunistic predator, and the clear presence of Antarctic krill in this demersal predator’s diet may indicate a benthic habit of this euphausiid species, which has hitherto mainly been considered as occupying a purely pelagic niche.     

DIET OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS) IN CLAYOQUOT SOUND, BRITISH COLUMBIA, CANADA

In Clayoquot Sound, British Columbia, gray whales ( Eschrichtius robustus ) forage for pelagic, hyperbenthic, and benthic invertebrates. Prey types were collected near feeding whales and at sites where no whales were observed to ascertain whales' diets and to describe prey populations and distributions. Characteristics of prey that are examined include species composition, density, biomass, and size. Whales foraged for mysids, Holmesimysis sculpta being the most abundant species collected. Whales foraged near concentrated patches of porcelain crab zoeal larvae, composed primarily of Pachycheles rudis , 21 –294 times the average density and biomass normally collected. Amphipod biomass, composed primarily of Ampelisca agassizi and A. careyi , was 160 ± 150 g/m² where whales foraged. Larger amphipods, rather than higher density, resulted in higher amphipod biomass between years. Whales foraged where there was a high proportion (61%) of amphipods > 6 mm in length. Whales initially foraged for amphipods along the 20-m depth contour line; amphipod biomass was best developed and least variable at depths between 16 and 20 m.     

Comparisons between the influence of habitat type, season and body size on the dietary compositions of fish species in nearshore marine waters

Fish were collected from over bare sand in nearshore shallow waters at three sites that varied in the extent to which they were exposed to wave activity and which were located within a 45-km stretch on the lower west coast of Australia. Sampling was undertaken within a 4-6-week period in each season. The volumetric contributions of different prey to the stomach contents and the mouth characteristics of four species, i.e. Sillago bassensis and Sillago vittata (Sillaginidae), Spratelloides robustus (Clupeidae) and Pseudorhombus jenynsii (Bothidae), were determined. Overall, the dietary compositions of the four species differed significantly from each other and those of fish at both the three different sites and in four consecutive seasons were also significantly different. In comparison with S. bassensis, the morphologically similar S. vittata fed to a relatively greater extent on polychaetes than zooplankters, presumably reflecting in part its greater ability to extend its upper jaw downwards towards the benthos. S. robustus typically targeted calanoid copepods in the plankton, whereas P. jenynsii fed on larger benthic prey taxa, reflecting the large differences in mouth morphology and feeding behaviour of these species. Although the diets of S. bassensis and S. vittata were strongly influenced by habitat type and season, the former variable was slightly more important for both of these species. However, the reverse applied with S. robustus. Season strongly influenced the dietary composition of P. jenynsii at the one site at which it was regularly caught. The diets of the two Sillago species and P. jenynsii underwent pronounced size-related changes, which would help distribute the food resources among the individuals of the different size classes of each of these species. In contrast, all size classes of S. robustus fed predominantly or exclusively on calanoid copepods at all sites and in all seasons, except at the most sheltered site in winter when these zooplankters were not found in samples taken from the water column. The seasonal and habitat variations recorded in the diets of the fish species in this study imply that these species are able to feed opportunistically, a characteristic that would be of particular value to fish that live in nearshore waters where the relative abundance of the different prey types varies with habitat type and season.     

Epifauna living on sublittoral seaweeds around Cyprus

Macroepifauna living on sublittoral seaweeds were counted,identified and compared among six locations in Cyprus. Mollusks,amphipods, and polychaetes were the major taxa represented. Thedominant alga was Cystoseira barbata which was present at 4of 6 stations and ranged in wet weight from 1–2 kg m^-2 ofbottom. Percent cover of C. barbata ranged from 25 to 90%.Other dominant algae were Laurencia obtusa, Padinapavonica, and Jania rubens. The distribution of epifaunaabundance, species composition, and species richness varied amonglocations. Total epifauna abundance ranged from 1000 to 2250animals m^-2. The abundance of epifauna per gram of plant wassignificantly lower on C. barbata than on the other algalspecies. The total epifauna species richness was more related tolocal algal plant diversity than to plant biomass.     

Predatory disturbance and prey species diversity: the case of gray whale (<Emphasis Type="Italic">Eschrichtius robustus</Emphasis>) foraging on a multi-species mysid (family <Emphasis Type="Italic">Mysidae</Emphasis>) community

Why competitive exclusion does not limit the number of coexisting plankton species is a persistent question for community ecology. One explanation, the intermediate disturbance hypothesis (IDH), proposes that elevated species diversity is a product of moderate levels of disturbance that allow the subsequent invasion of less competitive species. Here, we assess the shifts in species diversity in a mysid (Mysidae Dana, 1850) zooplankton community, where at least 10 species have, over the last 15 years, have come to comprise the primary prey base of summer resident gray whales (Eschrictius robustus Lilljeborg, 1861) in Clayoquot Sound, British Columbia. We evaluate trends in the community structure of mysids (species dominance, diversity, and richness) across mysid habitat in the study area during the gray whale foraging season (May–September) for the period 1996 and 2008. Mysid species composition varies among years and diversity has increased as whales shifted their predatory focus from benthic amphipods (Ampeliscidae Costa, 1857) to mysids, near our starting point in 1996. Holmesimysis sculpta Tattersall, 1933 was the dominant species in early years; however, in 2007, the dominance shifted to Neomysis rayi Murdoch, 1885. The habitat restrictions and life history attributes of local populations of coastal mysids leave them vulnerable to the cumulative impacts of increased predation pressure by gray whales. This case study presents a unique examination implicating predation as an agent of disturbance capable of altering the species structure of a local prey community.     

Seasonal fluctuations of vagile benthos in the uppermost sublittoral of a maritime Antarctic fjord

Quantitative samples of benthos were taken on a stony beach in the maritime Antarctic (Admiralty Bay, King George Island, South Shetland Islands) during a complete annual cycle. The sampled habitat consisted of cobbles lying on sand and gravel in the fringe between the littoral and sublittoral zones; samples were always taken at low tide just below the water line. In this habitat, abundant macroalgal detritus was observed between stones. This stony beach appeared to be very rich in vagile fauna settled between and under stones. Macrobenthos consisted mainly of amphipods (ca. 85% of total number), gastropods (11%) and nemerteans (3%). The abundance of whole macrofauna ranged to over 50,000 ind. m^-2 and its biomass over 600 g m^-2 (FW). Seven species of Amphipoda and four species of Gastropoda were found. Amphipoda were dominated by Gondogeneia antarctica (over 70% of all amphipods) and Paramoera edouardi (over 20%), whereas among gastropods Laevilitorina antarctica prevailed (over 70%). Unexpectedly high abundance and biomass of Amphipoda were observed in the first half of winter (May/July), surpassing otherwise important summer amphipod abundance. The probable reason for this phenomenon could be high autumn abundance of decaying algae on the beach in the tidal zone, providing detritus that is probably the main food source for Amphipoda.     

Life History and Production of the Western Gray Whale’s Prey,Ampelisca eschrichtii Kr?yer, 1842 (Amphipoda,Ampeliscidae)

Ampelisca eschrichtii are among the most important prey of the Western North Pacific gray whales, Eschrichtius robustus. The largest and densest known populations of this amphipod occur in the gray whale’s Offshore feeding area on the Northeastern Sakhalin Island Shelf. The remote location, ice cover and stormy weather at the Offshore area have prevented winter sampling. The incomplete annual sampling has confounded efforts to resolve life history and production of A. eschrichtii. Expanded comparisons of population size structure and individual reproductive development between late spring and early fall over six sampling years between 2002 and 2013 however, reveal that A. eschrichtii are gonochoristic, iteroparous, mature at body lengths greater than 15 mm and have a two-year life span. The low frequencies of brooding females, the lack of early stage juveniles, the lack of individual or population growth or biomass increases over late spring and summer, all indicate that growth and reproduction occur primarily in winter, when sampling does not occur. Distinct juvenile and adult size cohorts additionally indicate growth and juvenile production occurs in winter through spring under ice cover. Winter growth thus requires that winter detritus or primary production are critical food sources for these ampeliscid populations and yet, the Offshore area and the Eastern Sakhalin Shelf ampeliscid communities may be the most abundant and productive amphipod population in the world. These A. eschrichtii populations are unlikely to be limited by western gray whale predation. Whether benthic community structure can limit access and foraging success of western gray whales is unclear.     

Nemertea inhabiting the Haploops (Amphipoda) community of the northern Øresund with special reference to the biology of Nipponnemertes pulcher (Hoplonemertea)

The densities of nemerteans and associated fauna on a soft-bottom sampling station (27–30 m deep) in the Øresund were determined from 47 cores (each 135 cm² in cross-section; 20 + cm deep) collected from September to December 1989; these data were compared with 14 cores taken from the same location in December 1982. Nine species of nemerteans were identified from cores and dredge samples: Palaeonemertea — Callinera-like sp.; Heteronemertea — Cerebratulus fuscus, C. marginatus, Lineus bilineatus, Micrura fasciolata, M. purpurea; Hoplonemertea — Amphiporus bioculatus, A. dissimulans, Nipponnemertes pulcher. Mean numbers of heteronemerteans were 32 and 10 m^?2 in 1982 and 1989, respectively, and hoplonemerteans were 90 and 71 m^?2 , respectively. Only one palaeonemertean was collected during both years. Mean densities of the dominant species, N. pulcher, were similar for the two years, 74 and 68 m^?2. The dominant groups of macrofauna (n m^?2) in 1989 were ostracods (1028), amphipods (618), polychaetes (514), and ophiuroids (449). Amphipods (>90% Haploops spp.) and polychaetes (at least 30 spp.) are the major potential prey for hoplonemerteans and heteronemerteans, respectively. Laboratory feeding experiments with N. pulcher revealed that it consumed amphipods (Haploops tenuis and H. tubicola) at a rate of 2.6 worm^?1 d^?1 during the first 12 hours, but after 36 hours and beyond the rate was maintained at approximately 0.2 worm^?1 d^?1. Beyond 12 hours this nemertean showed a tendancy to only partially evacuate its prey. It was demonstrated experimentally that N. pulcher has a supply of toxin capable of killing six amphipods in approximately one hour. Limited tests showed that N. pulcher fed on the cumacean Diastylis tumida, but not on the amphipod Maera loveni or the ostracod Philomedes globosus, and that Amphiporus dissimulans readily attacked Haploops spp., but not Maera or Philomedes. Although the results of laboratory experiments are tentative, they do suggest that suctorial hoplonemerteans can exert a potentially significant effect on benthic communities. Employing seven species of polychaetes as prey for Cerebratulus fuscus and Micrura fasciolata, only the latter responded positively to one of them, Glycera alba. The hermit crab Pagurus bernhardus violently rejected N. pulcher in all feeding trials.     

Trophic structure of the macrobenthic community of Hornsund,Spitsbergen, based on the determination of stable carbon and nitrogen isotopic signatures

Hornsund is a cold-water fjord in southwestern Spitsbergen, Svalbard Archipelago, with a resident biota that exhibit typical low-temperature Arctic features. Carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic signatures of macrobenthic fauna and its potential food sources were measured in summer 2008 to delineate the trophic structure of the bottom community and to identify its principal carbon sources. The soft-bottom fauna at a water depth of 100 m was found to rely primarily on detritus, which is supplied by sedimentation of suspended organic matter from the water column and horizontal transport of refractory macroalgae from euphotic coastal habitats. Through resuspension by bottom currents, deposited particles also contributed to the diet of benthic filter-feeders. Since benthic organisms were significantly enriched in ¹³C compared to epibenthic zooplankton (mainly amphipods and decapods), the stable carbon signature provides a tool to differentiate benthic and pelagic feeding habits. The benthic food web was characterized by a conventional trophic structure with decreasing species numbers in increasing trophic levels. Primary consumers feeding on a mixture of plant matter, fecal pellets, decaying animal tissue, bacteria, and protists accounted for the greatest biomass share (62 % of the total macrobenthic biomass), followed by secondary consumers (38 %). Based on δ¹⁵N signatures, three trophic levels were detected, corresponding to the following feeding guilds: filter-feeders and feeding generalists (mainly bivalves, crustaceans, polychaetes, and some fish), mixed detritivore–carnivores (polychaetes, priapulids, crustaceans, and ophiuroids) and obligate carnivores (ascidians). The average food chain length (4.5 trophic levels) suggests that high-quality food is readily available in this Arctic fjord ecosystem.     

Threshold foraging by gray whales in response to fine scale variations in mysid density

The gray whale (Eschrichtius robustus) is a coastal species whose nearshore summer foraging grounds off the coast of British Columbia offer an opportunity to study the fine scale foraging response of baleen whales. We explore the relationship between prey density and gray whale foraging starting with regional scale (10 km) assessments of whale density (per square kilometer) and foraging effort as a response to regional mysid density (per cubic meter), between 2006 and 2007. In addition we measure prey density at a local scale (100 m), while following foraging whales during focal surveys. We found regional mysid density had a significant positive relationship with both gray whale density and foraging effort. We identify a threshold response to regional mysid density for both whale density and foraging effort. In 2008 the lowest average local prey density measured beside a foraging whale was 2,300 mysids/m³. This level was maintained even when regional prey density was found to be substantially lower. Similar to other baleen whales, the foraging behavior of gray whales suggests a threshold response to prey density and a complex appreciation of prey availability across fine scales.     

Feeding activities of two euryhaline small-sized fish in a western Baltic brackish fjord

The daily food intake and feeding activities of the common gobyPomatoschistus microps (Krøyer) and the nine-spined sticklebackPungitius pungitius (L.) were investigated in the brackish Schlei fjord. At the investigation site of Olpenitz, salinities varied between 11 and 15‰, and water temperatures between 5 and 18°C during the period of in-situ experiments in 1981 and 1982. Common gobies sometimes attained a density of more than 100 individuals per square metre, nine-spined sticklebacks as much as 18 individuals per square meter. Their food changed depending on the supply of plankton or benthos. Regarding numbers, their food consisted mainly of harpacticoids, in springtimes of calanoids; with regard to weight, amphipods, polychaetes or chironomid larvae often prevailed. The total food ingestion, measured by means of its relation to fish weights (fullness index), was highest in spring and summer: 2.3% inP. microps and 2.6% inP. pungitius. Low fullness indices of 0.8% inP. microps and 0.3% inP. pungitius were found during times of low water temperatures. 24-h field investigations revealed that the adultP. microps presented clear diurnal rhythms with highest fullness indices after dawn and a further maximum at dusk. Only young gobies ingested some benthos at night.P. pungitius displayed similar rhythms in which maximum fullness indices varied during the day. This species seems to forage every four hours. At dusk, both species preferred benthos to plankton. The results are discussed with respect to the implications of diurnal and seasonal fluctuations in prey choice by small-sized fish populations.