The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon
1. Most animals are active by day or by night, but not both; juvenile salmonids are unusual in that they switch from being predominantly diurnal for most of the year to being nocturnal in winter. They are visual foragers, and adaptations for high visual acuity at daytime light intensities are genera...
Published in: | Functional Ecology |
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Language: | English |
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Online Access: | http://dx.doi.org/10.1046/j.1365-2435.1997.00098.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2435.1997.00098.x https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2435.1997.00098.x |
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crwiley:10.1046/j.1365-2435.1997.00098.x 2024-09-09T19:30:37+00:00 The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon FRASER, N. H. C. METCALFE, N. B. 1997 http://dx.doi.org/10.1046/j.1365-2435.1997.00098.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2435.1997.00098.x https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2435.1997.00098.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Functional Ecology volume 11, issue 3, page 385-391 ISSN 0269-8463 1365-2435 journal-article 1997 crwiley https://doi.org/10.1046/j.1365-2435.1997.00098.x 2024-08-27T04:28:13Z 1. Most animals are active by day or by night, but not both; juvenile salmonids are unusual in that they switch from being predominantly diurnal for most of the year to being nocturnal in winter. They are visual foragers, and adaptations for high visual acuity at daytime light intensities are generally incompatible with sensitive night vision. Here we test whether juvenile Atlantic Salmon Salmo salar are able to maintain their efficiency of prey capture when switching between diurnal and nocturnal foraging. 2. By testing the ability of the fish to acquire drifting food items under a range of manipulated light intensities, we show that the foraging efficiency of juvenile salmon is high at light intensities down to those equivalent to dawn or dusk, but drops markedly at lower levels of illumination: even under the best night condition (full moon and clear sky), the feeding efficiency is only 35% of their diurnal efficiency, and fish will usually be feeding at less than 10% (whenever the moon is not full, skies are overcast or when in the shade of bankside trees). Fish were unable to feed on drifting prey when in complete darkness. 3. The ability of juvenile salmon to detect prey under different light intensities is similar to that of other planktivorous or drift‐feeding species of fish; they thus appear to have no special adaptations for nocturnal foraging. 4. While winter drift abundance is slightly higher by night than by day, the difference is not enough to compensate for the loss in foraging efficiency. We suggest that juvenile salmon can nonetheless switch to nocturnal foraging in winter because their food requirements are low, many individuals adopting a strategy in which intake is suppressed to the minimum that ensures survival. Article in Journal/Newspaper Atlantic salmon Salmo salar Wiley Online Library Functional Ecology 11 3 385 391 |
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collection |
Wiley Online Library |
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crwiley |
language |
English |
description |
1. Most animals are active by day or by night, but not both; juvenile salmonids are unusual in that they switch from being predominantly diurnal for most of the year to being nocturnal in winter. They are visual foragers, and adaptations for high visual acuity at daytime light intensities are generally incompatible with sensitive night vision. Here we test whether juvenile Atlantic Salmon Salmo salar are able to maintain their efficiency of prey capture when switching between diurnal and nocturnal foraging. 2. By testing the ability of the fish to acquire drifting food items under a range of manipulated light intensities, we show that the foraging efficiency of juvenile salmon is high at light intensities down to those equivalent to dawn or dusk, but drops markedly at lower levels of illumination: even under the best night condition (full moon and clear sky), the feeding efficiency is only 35% of their diurnal efficiency, and fish will usually be feeding at less than 10% (whenever the moon is not full, skies are overcast or when in the shade of bankside trees). Fish were unable to feed on drifting prey when in complete darkness. 3. The ability of juvenile salmon to detect prey under different light intensities is similar to that of other planktivorous or drift‐feeding species of fish; they thus appear to have no special adaptations for nocturnal foraging. 4. While winter drift abundance is slightly higher by night than by day, the difference is not enough to compensate for the loss in foraging efficiency. We suggest that juvenile salmon can nonetheless switch to nocturnal foraging in winter because their food requirements are low, many individuals adopting a strategy in which intake is suppressed to the minimum that ensures survival. |
format |
Article in Journal/Newspaper |
author |
FRASER, N. H. C. METCALFE, N. B. |
spellingShingle |
FRASER, N. H. C. METCALFE, N. B. The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon |
author_facet |
FRASER, N. H. C. METCALFE, N. B. |
author_sort |
FRASER, N. H. C. |
title |
The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon |
title_short |
The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon |
title_full |
The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon |
title_fullStr |
The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon |
title_full_unstemmed |
The costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile Atlantic Salmon |
title_sort |
costs of becoming nocturnal: feeding efficiency in relation to light intensity in juvenile atlantic salmon |
publisher |
Wiley |
publishDate |
1997 |
url |
http://dx.doi.org/10.1046/j.1365-2435.1997.00098.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2435.1997.00098.x https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2435.1997.00098.x |
genre |
Atlantic salmon Salmo salar |
genre_facet |
Atlantic salmon Salmo salar |
op_source |
Functional Ecology volume 11, issue 3, page 385-391 ISSN 0269-8463 1365-2435 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1046/j.1365-2435.1997.00098.x |
container_title |
Functional Ecology |
container_volume |
11 |
container_issue |
3 |
container_start_page |
385 |
op_container_end_page |
391 |
_version_ |
1809899607577067520 |