title: Effects of different artificial photoperiods and temperatures on haematological parameters of rainbow trout (Oncorhynchus mykiss).
abstract: This study assessed the effects of two artificial photoperiods (LD 24:0 and LD 12:12) and three temperature regimes (9, 11, and 18 degrees C) for 30 days on haematological parameters of trout (Oncorhynchus mykiss) kept in freshwater. Samples were taken at days 7, 14, and 30 during exposure to treatments. A higher mortality (22%) and lower oxygen concentration (<8.0 mg/l) were associated with the combination of photoperiod LD 24:0 and 18 degrees C. The LD 24:0 photoperiod (independently of temperature) increased the haematocrit and the number of erythrocytes at days 7, 14, and 30 (P < 0.01). A temperature of 18 degrees C (independently of photoperiod regimes) diminished the number of total leucocytes, lymphocytes and thrombocytes (P < 0.01). The LD 24:0 photoperiod (also independently of temperature) lowered the number of lymphocytes only after 14 days of experimentation (P < 0.01). Interaction between artificial photoperiod and temperature was only observed at day 14 for polychromatophils (P < 0.01). These results resemble the effects of stress caused by elevated temperatures and the application of continuous light photoperiods, indicating that survival risks may develop in trout farming when this combination is met.
authors.affiliation: Department of Oceanography, Faculty of Natural Sciences and Oceanography, University of Concepción, PO Box 160-C, Concepcion, Chile. avalenz@udec.cl
authors.forename: Ariel E
authors.initials: AE
authors.lastname: Valenzuela
authors.forename: Victor M
authors.initials: VM
authors.lastname: Silva
authors.forename: Alfredo E
authors.initials: AE
authors.lastname: Klempau
mesh_terms: D000818:Animals; D001773:Blood Cells / Q000502:physiology; D004906:Erythrocyte Count; D005618:Fresh Water / Q000737:chemistry; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D007958:Leukocyte Count; D017686:Oncorhynchus mykiss / Q000097:blood* / Q000502:physiology*; D010100:Oxygen / Q000032:analysis; D017440:Photoperiod; D013696:Temperature
chemical_list: D006454:Hemoglobins; D010100:Oxygen