![]() ![]() ![]() Also at the end of study, ten randomly sampled fish from each tank were weighed to the nearest 0.1 g, and total length was measured to the nearest 1.0 mm. Total tank weights were recorded to the nearest 0.2 kg at the conclusion of the experiment. (a) Top view of a 3.63 m diameter circular tank indicating location of suspended plastic array used as environmental enrichment (b) Side view of a 3.63 m diameter ciruclar tank containing the array of suspended plastic conduit.Ī projected growth rate of 0.08 cm/day and a planned feed conversion of 1.1. Feeding rates were determined for each experiment by the hatchery constant method withįigure 1. The array was situated approximately 58 cm from the edge of the tank at a quarter turn of the tank away from the spray bar from which water entered the tank ( Figure 1(a) and Figure 1(b)).Īll fish were fed 3.0 mm BioVita feed (Bio-Oregon, Longview, Washington, USA) daily over a 12 hour period during daylight hours using automatic belt feeders (Pentair Aquatic Ecosystems, Apopka, Florida, USA). The pipes were evenly spaced approximately 16.5 cm from each other, arranged in an array with an area of 43 cm × 117 cm. The vertically suspended enrichments consisted of 20 hollow plastic polyvinyl chloride (PVC) electrical conduit pipes (diameter = 4.34 cm, length = 0.94 m), suspended from attachment points on the overhead covers. All tanks were near fully covered by corrugated plastic overhead covers. ![]() Three control tanks were devoid of any internal structure, while three tanks contained vertically-suspended structure as environmental enrichment, as described by White et al. Two different treatments were assigned to the six circular tanks (N = 3). Each tank initially received 4.60 kg (approximately 330 fish). On May 23, 2018, approximately 2000 fish (mean ± SE total length = 125.4 ± 3 mm, mean weight = 19.8 ± 1.5 g, N = 20) were moved into six larger tanks (diameter = 3.63 m, height = 1.09 m, water depth = 0.71 m). Juvenile Atlantic salmon, Saint John’s River strain, were reared initially in 1.8 m diameter unenriched circular tanks at McNenny State Fish Hatchery in rural Spearfish, South Dakota, USA, using well water at a constant temperature of 11˚C (water hardness as CaCO 3 = 360 mg/L, alkalinity as CaCO 3 = 210 mg/L, pH = 7.6, total dissolved solids = 390 mg/L). Thus, the objective of this study was to evaluate the hatchery rearing performance of Atlantic salmon after long-term rearing with vertically-suspended environmental enrichment. did not observe any environmental enrichment effects on Atlantic salmon growth until after 311 days of hatchery rearing. However, the 125-day study duration may not have been long enough to detect any effects from environmental enrichment with Atlantic salmon. ![]() did not observe improved hatchery rearing performance with the use of vertically-suspended arrays in juvenile Atlantic salmon (Salmo salar) during a 125 day study. In general, the suspension of vertical structures has improved feed conversion ratios and salmonid growth without disrupting circular tank self-cleaning. The use of vertically-suspended arrays as environmental enrichment is a recent development. As a result, there may be a potential increase of disease outbreaks and increased labor requirements from hatchery staff. While these supplements attempt to replicate a natural environment, they also disrupt the hydraulic self-cleaning of circular tanks. Forms of environmental enrichment have included natural and artificial plants, sand and gravel substrate, wood, rocks, and concrete blocks. It has been used in an attempt to alter fish behavior and physiology to improve hatchery rearing performance or post-stocking survival. Of vertically-suspended structures to improve the hatchery rearing performanceĮnvironmental enrichment is the addition of material within a barren hatchery rearing unit to imitate natural environments normally encountered by fish. The results of this study support the use The suspended array did not interfere with the hydraulic Likely because of large variances in body size due to sexual dimorphism and Individual fish length, weight, or condition factor between the treatments, Gain of 182.0 kg in the enriched tanks compared to 162.9 kg in the control Weight gain were not significantly different, although the difference in mean With enrichment compared to the barren control tanks. After 168 days,įeed conversion ratio was significantly improved for salmon reared in tanks This study investigated the use of a vertically-suspended plastic conduit arrayĪs enrichment in 3.63 m circular tanks during Atlantic salmon ( Salmo salar ) rearing. Materials into hatchery tanks to simulate a more natural rearing environment. Environmental enrichment is the incorporation of ![]()
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