摘要:

SUMMARY.1. The juveniles of dace (Leuciscus leuciscus(L.)) and roach (Rtuihts rtuihis(L.)) and yearling minnows (Phoxtnus phoxinus(L.)) exhibited generally similar patterns of feeding behaviour and preferences for particular prey types.2. Factors affecting prey selection included predator and prey size, prey activity and environmental conditions.3. All three species preferred prey sizes approximately 0.6x their maximum gape.4. Prey motion was essential to induce attack, and prey were usually selected in proportion to their relative activities.5. Specialization on one prey type was observed in still water, and was always directed at the most active prey type. In flowing water no specialization was observed, and size selection was suppressed in the juvenile fish. Yearling minnows, however, were size selective in both still and flowing water.6. The presence of macrophyte cover did not significantly change the pattern of prey selection, but did reduce the predation rale.7. These results are discussed in the context of previous studies of prey selection and optimal foraging.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01034.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARY.1. Blackfly larvae were collected from twenty‐one stations in five lake outlets in Southern Quebec. Tiles (total area=500cm2) were introduced in early March, and collected 4 weeks later: randomly selected rocks (30–500cm) from the surrounding area were collected at the same time.2. Larval densities on tiles were significantly less variable than on rocks. The variance of density estimates on tiles averaged 36% of the observed variance on natural rocks, or 67% when variance on rocks was corrected for average rock size.3. Tiles significantly overestimated densities on rocks in some streams, and significantly underestimated them in others. These differences could not be explained by microhabitat differences (distance from the lake, depth, current velocity) between rock and tile samples. The bias that tiles introduce in density estimates precludes their use in comparisons among si

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01035.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARY.1. The grazing of [methyl‐3H]thymidine‐labelled bacteria by zooplankton was studied in Lake Norrviken. Sweden.2. Animals did not ingest bacteria attached to large colonies of the cyanobacteriumMicrocystis wesenbergiiKom. but small aggregates of hacteria and free bacteria were readily consumed.3.Diaphanosoma brachyurum(Liévin).Daphnia cucullataSars. andDaphnia galeataSars grazed free bacteria more quickly than aggregates, butEndiaptomus gracilis(Sars),Chydorus sphaericusMüll. andBosmi‐ na coregonis.l. Baird grazed the aggregates more readily.4. Filtering rate determinations varied from LA to 123 μl ind.−1h− 1for var

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01036.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARY.1. A range of sizes ofErpobdelta octoculatafL.),Glossiphonia complanata(L.) andHelobdella stagnalis(L.) were introduced to a small weeded pond harbouring invertebrate and amphibian predators. Control leeches were kept in protective cages. Subsequently, gut contents of potential predators were tested against three anti‐leech sera, using the precipitin test. Five of fifteen species tested had fed on leeches;Agabus, Pyrrhosoma, Aeshna, Sympetrumand larvalTrilurus.2. The size distributions of introduced and surviving leeches were compared. Predation pressure had been greatest on smaller leeches and this may have accounted for the observed differential mortality between leech species.3. It is concluded that predation may cause significant mortality in leech populations in weeded ponds, with severity determined by the types and abundance of predators presen

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01037.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARY.1. The intersetular distance (filter mesh‐size) of adultSimocephalusshowed a two‐fold seasonal variation in each of two ponds. In one pond the maximum intersetular distance was found in March, while in the other pond the maximum intersetular distance was found in September.2. These seasonal changes in intersetular distances was positively correlated with changes in phytoplankton biomass (estimated by chlorophyll a). As food concentration increased (estimated by chlorophyll a) the mean intersetular distance of adullSimocephalusalso increased.3. The intersetular distances on fillcring setae also vary with the size of animals. There is a linear relation between body length and intersetular distance.4. Variation in the intersetular dimension with body size may decrease competition tor food between adults and yo

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01038.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01039.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Tyler, S.(Ed.) (1986)Advances in the Biology of Turbellarians and Related Flatyhelmin‐ thes.Smol, J.P., Battarbee, R.W., Davis, R.B&Meriläinen, J.(Eds) (1986)Diatoms and Lake Acidity.Jenkins, D.&Shearer, W.M.(Eds) (1986)The Status of the Atlantic Salmon in Scotla

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01040.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1987.tb01041.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY