On the Food of the Salmonoid Fish, Ayu (Plecoglossus altivelis Temminck &amp; Schlegel). II

Ueda, Saburo; Okada, Yoshikazu

doi:10.2331/suisan.3.275

Cited by 5 publications

(4 citation statements)

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“…Microalgae ingested by ayu in the Ohta River were similar to those reported by Matsui, 6 and Ueda and Okada, 2–5 except for the blue‐green algae Homoeathrix sp. and the green algae Dictyosphearium sp.…”

Section: Discussionsupporting

confidence: 84%

“…Ayu gain weight rapidly while feeding on these microalgae in rivers, but the intestine is relatively short compared to other herbivorous fishes 1 . Food organisms and the feeding behavior of ayu have been described previously by Ueda and Okada, 2–5 Matsui, 6 Ishida, 7 and Kawanabe et al 8 Rearing techniques for ayu are well established, but digestion mechanisms are poorly known. Better understanding of digestive mechanisms should be useful for improving the quality of artificial food fed to cultured ayu.…”

Section: Introductionmentioning

confidence: 95%

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Characterization of the digestive tract of wild ayu

et al. 2002

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The gut and gut contents of ayu Plecoglossus altivelis caught in the Ohta River in Hiroshima prefecture, Japan were examined. Relative intestine length (intestine length/body length) was almost constant. Except for relative intestine length, characteristics of the gut of wild ayu were not significantly different from those of cultured ayu. The height of intestinal folds increased and their width declined from stomach to anus. Cyanobacteria (Homoeathrix sp. and Calothrix sp.) and diatoms (Cymbella sp., Gomphonema sp., Melosira sp., Navicula sp., and Synedra sp.) were well digested during passage through the gut despite a lack of apparent destruction. In contrast, green algae (Dictyosphearium sp., Coelastrum sp., and Pediastrum sp.) exhibited little degradation. The pH of stomach contents ranged from 2.8 to 7.4 (mean ± SD = 4.1 ± 1.0), whereas that of the posterior intestine was 7.0–8.5 (7.9 ± 0.4). Gut contents of wild ayu increased with bodyweight, and were more than threefold greater than those of cultured ayu, suggesting that wild ayu compensate for low nutrient content of algae through the continuous ingestion of large quantities of feed organisms.

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Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 95%

Characterization of the digestive tract of wild ayu

et al. 2002

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“…Hatched larvae drift downstream to the sea or lakes, and young fish swim up the rivers in spring. Ayu forage predominantly on benthic algae on river cobbles, boulders, and rocks, occasionally establishing territories (Kawanabe 1970, Iguchi and Hino 1996, Katano and Iguchi 1996, but when benthic algae are not available, they prey on invertebrates (Ueda and Okada 1934, 1935, Morioka et al 1989.…”

Section: Fish and Study Areamentioning

confidence: 99%

Indirect Contramensalism Through Trophic Cascades Between Two Omnivorous Fishes

Katano

Aonuma

Nakamura

et al. 2003

Ecology

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The impact of trophic cascades on the interspecific relationship between two omnivorous stream fish, ayu (Plecoglossus altivelis altivelis) and Japanese dace (Tribolodon hakonensis), were analyzed in experimental pools. Benthic algae grew on the pool beds, and macroinvertebrates colonized the pools. Ayu predominantly grazed the algae, occasionally forming territories. Japanese dace fed on both benthic algae and invertebrates when ayu were absent, and predominantly on invertebrates when ayu were present. The presence of Japanese dace reduced the number of invertebrates and increased algal biomass (chlorophyll a) through trophic cascades, but the effects of respiration and excretion of dace did not notably increase algal biomass probably because the water continuously pumped into the pools was already nutrient rich. The growth rate of ayu was enhanced in the presence of Japanese dace due to increased algal biomass. In contrast, as the number of ayu increased, the growth rate of Japanese dace was reduced because of the exploitation of benthic algae and occasional attacks by ayu on dace. The relationship between ayu and Japanese dace is not merely competitive, but partly indirect contramensalism through trophic cascades. The occasional attacks by ayu on Japanese dace were mainly directed at individuals moving near the pool beds and therefore might function to increase benthic algal resources by limiting grazing by dace.

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“…Both goldfish and Japanese dace are omnivorous, feeding on plants and animals 23,33 . Adult ayu graze predominantly on benthic algae, but occasionally feed on both aerial and aquatic invertebrates 34–36 . In the experimental ponds, benthic algae increased rapidly, constituting an important food resource for all prey fish.…”

Section: Discussionmentioning

confidence: 99%

An experimental study of the effects of smallmouth bass on the behavior, growth and survival of prey fish

Katano

Aonuma

2002

Fisheries Sci

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The effects of smallmouth bass on the behavior, growth and survival of the prey fish (goldfish, ayu and Japanese dace) were examined experimentally in artificial ponds. In most cases, goldfish aggregated both when smallmouth bass were present and absent. Ayu and Japanese dace aggregated more frequently in the presence of smallmouth bass. All prey fish fed predominantly on benthic algae or aquatic insects and their dietary composition was not affected by smallmouth bass. In goldfish and Japanese dace, the total number of feeding acts exhibited by each individual was significantly less in the presence of smallmouth bass than in the absence and, in goldfish, the growth rate was less when smallmouth bass were present. In contrast, the presence of smallmouth bass did not affect either the total number of feeding acts or the growth rate of ayu. However, ayu were preyed on by smallmouth bass most frequently among the three prey species. Smallmouth bass tended to prey on smaller individuals, but ayu were not smaller than goldfish or Japanese dace.

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On the Food of the Salmonoid Fish, Ayu (Plecoglossus altivelis Temminck & Schlegel). II

Cited by 5 publications

References 0 publications

Characterization of the digestive tract of wild ayu

Characterization of the digestive tract of wild ayu

Indirect Contramensalism Through Trophic Cascades Between Two Omnivorous Fishes

An experimental study of the effects of smallmouth bass on the behavior, growth and survival of prey fish

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