{"refrec":{"BRefID":13025,"RR":"<b>Keus, B.</b> (1986). De predatie van de garnaal (<i>Crangon crangon</i>) op het broed van het nonnetje (<i>Macoma balthica</i>). <i>Interne verslagen Nederlands Instituut voor Onderzoek der Zee</i>, 1986(5). NIOZ: Texel. 43 pp.","BEntID":13025,"PublicFlag":1,"CheckedFlag":0,"wosflag":0,"vabbflag":0,"RefStringPartII":". <i>Interne verslagen Nederlands Instituut voor Onderzoek der Zee</i>, 1986(5). NIOZ: Texel.  43 pp.","DocTypID":13,"DocType":"Reports","MarineFlag":1,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Keus, B.","OrigTitleTranslFlag":1,"Authorstringtrunc":"Keus, B.","Englishabstract":"During the summer of 1985 some investigations were carried out on predation by the shrimp (<i>Crangon crangon</i>) on juveniles of the bivalve (<i>Macoma balthica</i>). The main problem was whether this predation contributes significantly to the huge decrease in numbers of juvenile <i>Macoma balthica</i> that occurs during most summers. In the laboratory, shrimps from the size class 2.5 -3.0 cm were able to eat <i>Macoma</i> up to about 2.0 mm. In stomachs of shrimps of the same size class caught at high tide on the tidal flats, <i>Macoma balthica</i> up to a maximum size of 1.5 mm were found. It was concluded that on the tidal flats, where most shrimps are smaller than 3 cm, <i>Macomas</i> larger than 2.0 mm are not predated on by <i>Crangon crangon</i>. Larger shrimps were found to eat larger <i>Macomas</i>. Large shrimps also eat more <i>Macomas</i> than small ones. During high tide about 4 <i>Macomas</i> per m² were present in the stomachs of shrimps on the tidal flat. Based on this result, a predation of about 500 <i>Macomas</i> per m² per month was estimated. The predation by a shrimp population near the tidal channel (larger shrimps) was estimated to be also about 500 <i>Macomas</i> per month.per m². Experiments with shrimps in enclosures on the tidal flat yielded variable results. The average number of <i>Macomas</i> eaten was 3.4 per shrimp per day. With this result an average predation of about 1600 Macomas per m² per month was calculated. Fewer <i>Macomas</i> were eaten when <i>Corophium volutator</i> was also present in the cages as an altemative food source. The estimated predation pressure is not strong enough to explain the huge decrease in the numbers of juvenile <i>Macomas</i> during the first months of summer. A predation pressure of more than 1000 <i>Macomas</i> per month may account for a significant part of the mortality of juvenile <i>Macoma</i> in August and September.","AbstractOtherLang":"Gedurende de zomer van 1985 is onderzoek gedaan naar de predatie van de garnaal (<i>Crangon crangon</i>) op jonge bodem stadia van het nonnetje (<i>Macoma balthica</i>). De vraag was of deze predatie een belangrijke factor is in de vaak geconstateerde grote afname van de aantallen juveniele bivalven tijdens de zomermaanden. In het laboratorium werden door garnalen met een lengte tot 3.0 cm, die de overgrote meerderheid van de plaatpopulaties vormen, nonnetjes tot ca. 2 mm geconsumeerd. In de magen van garnalen van 2.5 tot 3.0 cm die tijdens hoogwater op de plaat gevangen waren werden nonnetjes tot 1.5 mm aangetroffen. Geconcludeerd werd dat nonnetjes als ze op de platen een lengte van 2 mm bereikt hebben verder veilig zijn voor garnalenpredatie. Grotere garnalen eten gemiddeld grotere nonnetjes. Ook werden door de grotere garnalen gemiddeld meer nonnetjes gegeten dan door de kleinere. Op een plaat waren tijdens hoogwater op 28 augustus gemiddeld ca. 4 nonnetjes per m² aanwezig in garnalenmagen. Hieruit werd een predatie van ongeveer 500 nonnetjes per m² per maand berekend. Voor een garnalenpopulatie vlak bij een geul (grotere garnalen) werd ook een predatie van ca. 500 nonnetjes per m² per maand gevonden. Experimenten met garnalen in bakjes op het wad leverden sterk variërende resultaten op. Gemiddeld werden per garnaal 3.4 nonnetjes per dag geconsumeerd. Hiermee werd een predatie van ca. 1600 nonnetjes per maand berekend. Was <i>Corophium volutator</i> als alternatief voedsel aanwezig dan werden minder nonnetjes geconsumeerd. De uit de resultaten berekende predatiedruk is niet voldoende groot om de grote afname van bivalvenbroed gedurende de eerste zomermaanden (juni-juli) geheel te verklaren. Een predatiedruk van meer dan 1000 nonnetjes per maand zou na juli wel merkbare invloed kunnen hebben.","BibLvlCode":"MS","StandardTitle":"De predatie van de garnaal (<i>Crangon crangon</i>) op het broed van het nonnetje (<i>Macoma balthica</i>)","OrigTitleLangCode":"nl","OrigTitleLangCodeExtended":"dut","OrigTitleLangID":41,"DateLastModified":{"date":"2025-07-22 01:33:06.175990","timezone_type":1,"timezone":"+02:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":null,"OtherDescriptors":null,"Notes":null,"AnaPub":null,"MonPub":1986,"DateUpdate":"2025-07-15","DateCreate":"2001-07-09","SecASFANote":null,"ConfID":null,"PeerRev":0,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":1},"refs":null,"anarec":null,"monrec":{"MonID":13025,"ISBN":null,"PubliDate":1986,"IssueDate":null,"Volume":"1986","Issue":"5","Pagination":"43","Place":"Texel","Edition":null,"BRefXtra":null,"BRefXtraRR":null,"SerID":5036,"SerRR":"Interne verslagen Nederlands Instituut voor Onderzoek der Zee. 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