Detection of Conspecific Alarm Cues by Juvenile Salmonids under Neutral and Weakly Acidic Conditions: Laboratory and Field Tests

• Published in: Oecologia 2004-04, Vol.139 (2), p.318-324
• Main Authors: Leduc, Antoine O. H. C., Kelly, Jocelyn M., Brown, Grant E.
• Format: Article
• Language: English
• Subjects: Acid Rain - adverse effects; Agnatha and pisces; Agnatha. Pisces; Animal and plant ecology; Animal behavior; Animal ethology; Animal, plant and microbial ecology; Animals; Applied ecology; Behavioural Ecology; Biological and medical sciences; Creeks; Demecology; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on vertebrates; Experimentation; Field study; Field tests; Fish; Foraging; Freshwater fishes; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Lethal effects; Mental stimulation; Natural streams; Oncorhynchus mykiss; Oncorhynchus mykiss - physiology; Pheromones; Phoxinus neogaeus; Pimephales promelas; Population Dynamics; Predators; Predatory Behavior; Psychology. Psychoanalysis. Psychiatry; Salmon; Salvelinus fontinalis; Smell; Streams; Trout; Trout - physiology; Vertebrata; Waterways; Young animals
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-004-1492-8

A variety of fishes possess damage-released chemical alarm cues, which play a critical role in the detection and avoidance of potential predation threats. Recently, we have demonstrated that the ability of fathead minnows (Pimephales promelas) and finescale dace (Phoxinus neogaeus) to detect and respond to conspecific alarm cues is significantly reduced under weakly acidic conditions (pH 6.0). Rainbow trout (Oncorhynchus mykiss) and brook charr (Salvelinus fontinalis) possess an analogous alarm cue system. However, it is unknown if the trout alarm cue system is likewise affected by relatively small changes in pH. In addition, previous studies have not verified this phenomenon under natural conditions. We conducted laboratory and field trials to examine the potential effects of acute exposure to weakly acidic (pH 6.0) conditions on the detection and response of conspecific alarm cues by juvenile trout. Our laboratory results demonstrate that while juvenile rainbow trout exhibit significant increases in antipredator behaviour under normal pH conditions (pH 7.0-7.2), they do not respond to the presence of conspecific chemical alarm cues (i.e. response is not different from controls) under weakly acidic conditions. Similarly, a wild strain of brook charr in their natural streams near Sudbury, Ontario, failed to detect conspecific alarm cues in a weakly acidic stream (mean pH 6.11) while they responded to these cues in a neutral stream (mean pH of 6.88). This is the first demonstration that relatively small changes in ambient pH can influence alarm responses under natural conditions. These data suggest significant, sub-lethal effects of acid precipitation on natural waterways.