Co60腹腔内標識によるニジマス稚魚の天敵の追跡

檜山 義夫; 能勢 幸雄; 清水 誠; 松原 純子

doi:10.2331/suisan.27.296

ON THE PREDATION OF RAIN-BOW TROUT FRY TRACED BY CO⁶⁰ BODY CAVITY TAG

Yoshio HIYAMA, Yukio NOSE, Makoto SHIMIZU, Junko MATSUBARA

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JOURNAL FREE ACCESS

1961 Volume 27 Issue 4 Pages 296-301

DOI https://doi.org/10.2331/suisan.27.296

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Published: April 25, 1961 Received: - Available on J-STAGE: February 29, 2008 Accepted: December 07, 1960 Advance online publication: - Revised: -
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Date of correction: February 29, 2008 Reason for correction: - Correction: ABSTRACT Details: Wrong : At about noon of May 1st, 1960, 191 individuals of rain-bow trout fry, in which 39 fish had a Co⁶⁰ pin radiation source (about 100μc) inserted in the abdominal cavity of each, were liberated close to the midpoint of the same stream that was used in the last Zn⁶⁵ injection experiment (Fig. 1). Since that afternoon, the vicinity around the stream was monitored by Crystal Scintillation Survey Meter (11/2″ NaI Crystal) and by G-M Survey Meter at least once a day, and the locations where the radiation sources were detected, were recorded on the map. (Fig. 1)
The recovery of these Co⁶⁰ marked fry and the Co⁶⁰ pins outside the liberated fry was done first from 9th to 11th of May and secondly from 26th to 29th of July. By these efforts, 36 pieces of Co⁶⁰ pins were recovered in total. 1) 21 individuals of living fry carrying the Co⁶⁰ pins inside their body (F in Fig. 1), 2) 10 pieces of the pins found on the bottom sand of the stream (S), 3) 5 pieces of the pins found in the holes under rocks (R).
About the 10 pieces of Co⁶⁰ pins found on the bottom sand, it was thought to be caused by the predation and the excretion of adult trouts. If it was really so, the adult trouts had taken about 1/4 of the liberated fry within 8 days.
About the 5 pieces of the pins found in the holes under huge rocks, we could not think of any cause other than the result of the predation and the excretion of Japanese water shrew, Chimarrogale platycephala, nested in the experimental area (Fig. 2 and 3). The quantity of predation during 8 days by this mammal was estimated as about 1/8 of total fry liberated.
However, the predation by a wild bird, Cinclus pallasii, the most powerful predator in the last year's experiment, was not recognised, though a couple of this birds with two youngs were very often found flying in the experimental area.
One of the reason why the bird did not predate the fry, was thought to be that the size of fry liberated in this year (average 8 gr.) was much larger than that of last year (average 1.2 gr. for small sized group and 2.7 gr. for large sized group). Moreover, it might be caused by that the distance from the point of liberation to the nest of this bird in this year was farther than that of last year. The nest was found just above the point of liberation in last year, but was not found in and near the experimental area this year.
Right : At about noon of May 1st, 1960, 191 individuals of rain-bow trout fry, in which 39 fish had a Co⁶⁰ pin radiation source (about 100μc) inserted in the abdominal cavity of each, were liberated close to the midpoint of the same stream that was used in the last Zn⁶⁵ injection experiment (Fig. 1). Since that afternoon, the vicinity around the stream was monitored by Crystal Scintillation Survey Meter (11/2" NaI Crystal) and by G-M Survey Meter at least once a day, and the locations where the radiation sources were detected, were recorded on the map. (Fig. 1)
The recovery of these Co⁶⁰ marked fry and the Co⁶⁰ pins outside the liberated fry was done first from 9th to 11th of May and secondly from 26th to 29th of July. By these efforts, 36 pieces of Co⁶⁰ pins were recovered in total. 1) 21 individuals of living fry carrying the Co⁶⁰ pins inside their body (F in Fig. 1), 2) 10 pieces of the pins found on the bottom sand of the stream (S), 3) 5 pieces of the pins found in the holes under rocks (R).
About the 10 pieces of Co⁶⁰ pins found on the bottom sand, it was thought to be caused by the predation and the excretion of adult trouts. If it was really so, the adult trouts had taken about 1/4 of the liberated fry within 8 days.
About the 5 pieces of the pins found in the holes under huge rocks, we could not think of any cause other than the result of the predation and the excretion of Japanese water shrew, Chimarrogale platycephala, nested in the experimental area (Fig. 2 and 3). The quantity of predation during 8 days by this mammal was estimated as about 1/8 of total fry liberated.
However, the predation by a wild bird, Cinclus pallasii, the most powerful predator in the last year's experiment, was not recognised, though a couple of this birds with two youngs were very often found flying in the experimental area.
One of the reason why the bird did not predate the fry, was thought to be that the size of fry liberated in this year (average 8 gr.) was much larger than that of last year (average 1.2 gr. for small sized group and 2.7 gr. for large sized group). Moreover, it might be caused by that the distance from the point of liberation to the nest of this bird in this year was farther than that of last year. The nest was found just above the point of liberation in last year, but was not found in and near the experimental area this year.

Date of correction: February 29, 2008 Reason for correction: - Correction: PDF FILE Details: -

Abstract

At about noon of May 1st, 1960, 191 individuals of rain-bow trout fry, in which 39 fish had a Co⁶⁰ pin radiation source (about 100μc) inserted in the abdominal cavity of each, were liberated close to the midpoint of the same stream that was used in the last Zn⁶⁵ injection experiment (Fig. 1). Since that afternoon, the vicinity around the stream was monitored by Crystal Scintillation Survey Meter (11/2" NaI Crystal) and by G-M Survey Meter at least once a day, and the locations where the radiation sources were detected, were recorded on the map. (Fig. 1)
The recovery of these Co⁶⁰ marked fry and the Co⁶⁰ pins outside the liberated fry was done first from 9th to 11th of May and secondly from 26th to 29th of July. By these efforts, 36 pieces of Co⁶⁰ pins were recovered in total. 1) 21 individuals of living fry carrying the Co⁶⁰ pins inside their body (F in Fig. 1), 2) 10 pieces of the pins found on the bottom sand of the stream (S), 3) 5 pieces of the pins found in the holes under rocks (R).
About the 10 pieces of Co⁶⁰ pins found on the bottom sand, it was thought to be caused by the predation and the excretion of adult trouts. If it was really so, the adult trouts had taken about 1/4 of the liberated fry within 8 days.
About the 5 pieces of the pins found in the holes under huge rocks, we could not think of any cause other than the result of the predation and the excretion of Japanese water shrew, Chimarrogale platycephala, nested in the experimental area (Fig. 2 and 3). The quantity of predation during 8 days by this mammal was estimated as about 1/8 of total fry liberated.
However, the predation by a wild bird, Cinclus pallasii, the most powerful predator in the last year's experiment, was not recognised, though a couple of this birds with two youngs were very often found flying in the experimental area.
One of the reason why the bird did not predate the fry, was thought to be that the size of fry liberated in this year (average 8 gr.) was much larger than that of last year (average 1.2 gr. for small sized group and 2.7 gr. for large sized group). Moreover, it might be caused by that the distance from the point of liberation to the nest of this bird in this year was farther than that of last year. The nest was found just above the point of liberation in last year, but was not found in and near the experimental area this year.

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