title: Chronic stress of rainbow trout Oncorhynchus mykiss at high altitude: a field study.
abstract: The stress response of Oncorhynchus mykiss in high-altitude farms in central Mexico was investigated over two seasons: the cool (9·1-13·7° C) dry winter season, and the warmer (14·7-15·9° C), wetter summer season. Fish were subjected to an acute stress test followed by sampling of six physiological variables: blood cortisol, glucose, lactate, total antioxidant capacity, haemoglobin concentration and per cent packed cell volume (VPC %). Multivariate analyses revealed that lactate and total antioxidant capacity were significantly higher in the summer, when water temperatures were warmer and moderate hypoxia (4·9-5·3 mg l(-1) ) prevailed. In contrast, plasma cortisol was significantly higher in the winter (mean ± s.e.: 76·7 ± 4·0 ng ml(-1) ) when temperatures were cooler and dissolved oxygen levels higher (6·05-7·9 mg l(-1) ), than in the summer (22·7 ± 3·8 ng ml(-1) ). Haemoglobin concentrations (mg dl(-1) ) were not significantly different between seasons, but VPC % was significantly higher in the summer (50%) than in the winter (35%). These results suggest that in summer, effects of high altitude on farmed fish are exacerbated by stresses of high temperatures and hypoxia, resulting in higher blood lactate, increased total antioxidant capacity and elevated VPC % levels.
authors.affiliation: Marine Conservation and Aquatic Physiology Laboratory (MCAPL), Biological Sciences Department, University of North Texas (UNT), Denton, TX, U.S.A.
authors.forename: I
authors.initials: I
authors.lastname: Hunt von Herbing
authors.affiliation: Marine Conservation and Aquatic Physiology Laboratory (MCAPL), Biological Sciences Department, University of North Texas (UNT), Denton, TX, U.S.A.
authors.forename: T-C F
authors.initials: TC
authors.lastname: Pan
authors.affiliation: Facultad de Ciencias, Universidad Autónoma del Estado de México (UAEM), Toluca, México.
authors.forename: F
authors.initials: F
authors.lastname: Méndez-Sánchez
authors.affiliation: Facultad de Ciencias, Universidad Autónoma del Estado de México (UAEM), Toluca, México.
authors.forename: M
authors.initials: M
authors.lastname: Garduño-Paz
authors.affiliation: Facultad de Ciencias, Universidad Autónoma del Estado de México (UAEM), Toluca, México.
authors.forename: O
authors.initials: O
authors.lastname: Hernández-Gallegos
authors.affiliation: Facultad de Ciencias, Universidad Autónoma del Estado de México (UAEM), Toluca, México.
authors.forename: M L
authors.initials: ML
authors.lastname: Ruiz-Gómez
authors.affiliation: Facultad de Ciencias, Universidad Autónoma del Estado de México (UAEM), Toluca, México.
authors.forename: G
authors.initials: G
authors.lastname: Rodríguez-Vargas
mesh_terms: D000531:Altitude; D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D001786:Blood Glucose / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry; D006854:Hydrocortisone / Q000097:blood; D000860:Hypoxia; D019344:Lactic Acid / Q000097:blood; D008800:Mexico; D017686:Oncorhynchus mykiss / Q000502:physiology*; D012621:Seasons; D013312:Stress, Physiological; D013696:Temperature
chemical_list: D000975:Antioxidants; D001786:Blood Glucose; D006454:Hemoglobins; D019344:Lactic Acid; D006854:Hydrocortisone
keywords: Mexico; alpine; aquaculture; hypoxia; salmonids; temperature