Abstract
Although an important part of the natural environment of fish, overhead cover is usually absent during hatchery rearing. To evaluate the possible influence of overhead cover on juvenile brown trout Salmo trutta hatchery rearing performance, this study compared three different cover treatments: near-full (98%) cover, partial (65%) cover, and no cover (completely open). After 12 weeks of rearing in 1.8 m-diameter circular tanks, total tank weight gain was significantly greater and feed conversion ratios were significantly less in tanks of brown trout that were either partially or near-totally covered, in comparison to those tanks that were completely open. The viscerosomatic index, hepatosomatic index, and splenosomatic index values were not significantly different among any of the treatments. Fin condition indices were also not significantly different. The use of either partial or full covers is recommended to maximize brown trout rearing efficiencies, with full covers providing the additional benefit of preventing fish from jumping out of the tanks.
Highlights
Tanks used during hatchery rearing are typically uncovered to facilitate regular cleaning, allow for observations on fish growth, and discover possible fish health issues [1] [2] [3]
The use of either partial or full covers is recommended to maximize brown trout rearing efficiencies, with full covers providing the additional benefit of preventing fish from jumping out of the tanks
Overhead cover is a normal part of the natural environment of wild fish, and brown trout Salmo trutta in particular is attracted to overhead cover [4] [5]
Summary
Tanks used during hatchery rearing are typically uncovered to facilitate regular cleaning, allow for observations on fish growth, and discover possible fish health issues [1] [2] [3]. Overhead cover is a normal part of the natural environment of wild fish, and brown trout Salmo trutta in particular is attracted to overhead cover [4] [5]. Because overhead cover is essential in natural habitats for numerous salmonids [6] [7] [8] [9] [10], studies have been conducted evaluating the use of partial covers during hatchery rearing. Partial overhead tank covers have improved the hatchery rearing performance of rainbow trout Oncorhynchus mykiss [11] [12] and brown. The benefits of partial tank covers have not been universally reported, and may be species or strain specific [14] [15] [16] [17]
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