R. S. McKinley

Influence of Transmitter Attachment Procedures on Swimming Performance of Wild and Hatchery-Reared Atlantic Salmon Smolts

Abstract Effects of transmitter attachment procedures on smolts of Atlantic salmon Salmo salar have primarily been examined in the laboratory with hatchery-reared fish. Biotelemetry researchers must extrapolate findings of tagging studies to wild, migrating smolts. Because hatchery rearing can affect salmonid development and because field tagging procedures and environmental conditions can differ from those in the laboratory, we measured critical swimming speed of hatchery-reared Atlantic salmon smolts equipped with internal, external, or gastric dummy radio transmitters in the laboratory. We then repeated the experiment with wild, migrating fish in ambient environmental conditions. Swimming ability of hatchery smolts was not significantly affected by any attachment procedure, and no significant differences were found between fish tested 1 or 16 h after tagging. Similarly, wild smolts were not impaired by gastric transmitters; however, performance of wild fish tested 1 or 16 h after internal or external a...

Cardiac Response to Variable Forced Exercise at Different Temperatures: An Angling Simulation for Smallmouth Bass

Abstract Longer angling durations (capture by hook and line) and higher water temperatures are generally thought to be more detrimental to angled fish. Here, this concept was investigated in smallmouth bass Micropterus dolomieu by monitoring cardiac output (CO) and its components, heart rate (HR) and stroke volume (SV), before, during, and after a simulated angling event in a Blazka-type respirometer. Fish (total n = 31) were acclimated to 12, 16, or 20°C and exposed to conditions that elicited repeated burst swimming either briefly (20 s) or to exhaustion (120–180 s). Resting CO and HR increased significantly with increasing temperature (Q 10 ∼ 2), indicating temperature conformity, whereas SV was not affected by temperature. Recovery times (time after angling until cardiac parameters returned to resting levels) ranged from 0 to 85 min (mean ∼ 40 min) for briefly angled fish and from 20 to 210 min (mean ∼ 105 min) for exhaustively angled fish. These recovery times increased significantly with angling dur...

Microhabitat Use of Juvenile Atlantic Cod in a Coastal Area of Bonavista Bay, Newfoundland

Abstract Scuba surveys were used to examine the seasonal abundance and habitat use (substrate, temperature, and depth) of two species of juvenile cod Gadus spp. over the diel cycle in a coastal area of Bonavista Bay, Newfoundland. The abundance of age-0 cod increased throughout the study period (from early August until mid-November), while that of age-1 and age-2 Atlantic cod Gadus morhua peaked in mid-October. The diel abundance of age-1 Atlantic cod increased with the onset of dusk, indicating that these individuals moved from other habitats into the study area at this time. Although all age-classes used areas with kelp significantly more than other areas during the day, the differences between age-classes became apparent at dusk. Age-1 cod showed no significant difference in habitat density at dusk, while age-2 cod had higher concentrations over complex substrates (kelp and boulders); habitat use at dusk by age-0 cod was inconclusive. No significant differences in nocturnal habitat use were found for a...