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Avoidance of solar ultraviolet radiation by juvenile coho salmon (Oncorhynchus kisutch)

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Abstract:

Shade-seeking behavior and avoidance of solar ultraviolet radiation (UVR) by newly emerged coho salmon (Oncorhynchus kisutch) alevins and two-month-old coho juveniles was documented in experimental trials in the Little Qualicum River, British Columbia, using outdoor chambers that provided the fish with a binary choice of photo environments. Under high solar intensities (i.e., midsummer, cloudless skies) coho of both age classes strongly preferred 50% neutral density shaded conditions to unattenuated full-spectrum (280–700 nm) sunlight (t test, p < 0.025). In addition, coho alevins and juveniles showed a high selective avoidance of UVR (280–400 nm) (t test, p < 0.05). Within the UVR spectrum, coho responded significantly to UVA (320–400 nm) (t test, p = 0.028). Evidence of UVB (280–320 nm) avoidance was confounded by higher visible and UVA irradiance levels under screens exposing coho to UVB. Under lower solar intensities (i.e., cloudy skies) coho showed no spectral preference and did not seek neutral density shade. Behavioral avoidance of high intensity UVR, particularly UVA, suggests that shade-seeking behavior of juvenile coho may be linked to avoiding potentially harmful UVR exposure.

Des chambres d'observation à l'extérieur qui offrent un choix binaire d'environnements lumineux nous ont permis d'étudier expérimentalement les comportements de recherche de l'ombre et d'évitement de la radiation solaire ultraviolette (UVR) chez des alevins nouvellement émergés et des jeunes saumons coho (Oncorhynchus kisutch) âgés de 2 mois dans la petite rivière Qualicum en Colombie-Britannique. Sous de fortes intensités de radiation solaire, (i.e., à la mi-été, sous un ciel découvert), les saumons des deux groupes préfèrent nettement des conditions d'ombrage de densité neutre de 50 % à la lumière solaire non-filtrée de plein spectre (280–700 nm) (test de t, p < 0,025). Les saumons réagissent de façon significative aux radiations UVA (320–400 nm) dans le spectre des UVR (test de t, p = 0,028). Les indications de l'existence d'un évitement des radiations UVB sont masquées par la présence de niveaux d'irradiance de lumière visible et UVA sous les filtres exposant les saumons à l'UVB. Dans des conditions d'intensité solaire réduites (i.e., sous un ciel nuageux), les saumons n'affichent pas de préférence pour une région particulière du spectre lumineux et ne recherchent pas l'ombre de densité neutre. L'évitement de l'UVR de haute intensité, particulièrement de l'UVA, par les jeunes saumons coho laisse croire que le comportement de recherche de l'ombre est relié à l'évitement d'une exposition potentiellement nocive à la radiation UVR.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2002-03-01

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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