Assessment of octopus beak digestion by a harbor seal (Phoca vitulina) under feeding experiment.
In: Journal of Agriculture Science Tokyo, Jg. 67 (2022-10-01), Heft 3, S. 111-115
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Zugriff:
Seals are considered ecologically important because they are the top predator in coastal ecosystems・ However, the dietary habits necessary for assessing their impact have been investigated using indirect methods because foraging behavior cannot be directly observed. Of these, stomach content analysis can directly identify the foraging organisms and the amount of food consumed during the day or so immediately prior to death. 011 the other hand, it has been pointed out that the digestion in the stomach may lead to underestimation of species identification and foraging volume estimation. In this study, we euthanized a harbor seal, which was scheduled to be killed for population control purposes, alter feeding it one octopus per day for eight consecutive days and examined the effect of digestion by analyzing the remaining lower beaks in the stomach. As a result, it was estimated that both the upper and lower jaw plates were retained in the stomach for about 7 days, and then migrated to the intestine. The Lower-Hood Length (LHL) of the lower beak was suggested to be the most accurate method for reproducing the weight of the forehead plate, which is necessary for estimating the weight of a predated octopus. [ABSTRACT FROM AUTHOR]
高次捕食者であるアザラシ類は沿岸生態系において生態学的に重要な位置を占めていると考えられる が,その影響評価に必要な食性については,採餌行動を直接観察できないことから間接的な手法の他 胃内 容分析による調査が行われている。このうち,胃内容分析は死亡する直前の1日間程度の採餌生物と採餌量 を直接特定することができるものの,胃内の消化》犬況によって種の同定や採餌量の推定が過小評価になる恐 れが指摘されている。本研究では,個体数管理上の殺処分が予定されているゼニガタアザラシ1個体に対し て8日間連続で1日1個体のマダコ科頭足類を給餌した後に安楽死させ,胃中に残った顎板を解析すること により消化の影響を検討した。その結果,顎板は上顎,下顎ともに胃内に7日間程度保持された後,腸内へ 消化されると推定された。顎板は消化により摩耗が進行するが,捕食されたマダコ科頭足類の重量を推定す るのに必要な額板重量の再現には,下顎のLower-Hood Length (LHL)を使用することが最も精度が高い ことが示唆された。. [ABSTRACT FROM AUTHOR]
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Titel: |
Assessment of octopus beak digestion by a harbor seal (Phoca vitulina) under feeding experiment.
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Autor/in / Beteiligte Person: | Takahito, MASUBUCHI ; Mari, KOBAYASHI |
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Zeitschrift: | Journal of Agriculture Science Tokyo, Jg. 67 (2022-10-01), Heft 3, S. 111-115 |
Veröffentlichung: | 2022 |
Medientyp: | academicJournal |
ISSN: | 0375-9202 (print) |
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