Alternatives to Freeze‐Dried Krill in the Feed Training Phase of Largemouth Bass

Abstract

Fry of largemouth bass Micropterus salmoides are typically pond reared on natural foods until they reach approximately 4–6 cm. Fish that are to be raised on pellets are typically feed trained in tanks using freeze‐dried krill (FDK), which is gradually replaced with prepared diet. The cost of FDK (retail >US$40 per kg) can be a significant expense in the feed training phase. An experiment was conducted to determine whether FDK could be eliminated by simple diet amendment. The largemouth bass fingerlings (mean weight ± SD = 2.2 ± 0.3 g) were stocked in 190‐L tanks at 150 fish/tank. Four treatments with four replicates each were compared: (1) fingerlings were initially fed FDK and then were gradually weaned to a commercial pellet (1.5‐mm floating trout feed; control [CTL], current practice); (2) fish were offered only the dry commercial pellet throughout (DRY); (3) commercial pellets were moistened with water before use (MST); and (4) commercial pellets were top‐dressed with menhaden fish oil at 10% of diet by weight initially and at a gradually reduced percentage over time (OIL). After 18 d, there was no significant difference (P > 0.05) in the average weights of fish. However, in terms of percentage of fish that were successfully habituated to the final dry pellets, the DRY treatment resulted in a significantly lower (P < 0.05) success rate (82%) than other treatments. Training success was not significantly different (P > 0.05) among the CTL (98%), MST (93%), and OIL (92%) treatments. The best diet for feed training of largemouth bass will vary depending on the cost and availability of FDK and the economic importance of production maximization.

The Effect of Water Temperature on Growth and Survival of Largemouth Bass during Feed Training

“…Training success in this study was 70-90%, which is higher than many published reports, but is comparable with previous feed-training experiments at this laboratory using the same strain, similar-sized fish, and a floating pellet as the training diet (Skudlarek et al 2007). According to Heidinger (2000), most established producers of largemouth bass are successful in training approximately 75% of pond-reared fingerlings to feed on a prepared diet.…”

“…Feed-training success of largemouth bass is highly variable, ranging from 13% to 90% (Lovshin and Rushing 1989;Sloane 1993;Kubitza and Lovshin 1997;Skudlarek et al 2007). As the cost of feedtrained largemouth bass fingerlings is relatively high (approximately US$0.20-0.25 per 7-cm-TL fish; Robert Mayer, Mayer's Fish Farm, Bardstown, Kentucky, personal communication), success rates during feed training can have a major effect on production costs.…”

“…Training success can be influenced by many variables including initial fish size and condition, the acceptability of the training diet, environmental conditions in the training system, stocking densities, and the genetic potential of the particular strain (Williamson 1983). Several studies have described and tested different initial food items, such as ground fish, fish eggs, moist pellets, and freeze-dried krill (FDK) used for feed training largemouth bass fingerlings (Snow 1965;Anderson 1974;Kubitza and Lovshin 1997;Skudlarek et al 2007). However, little to no research has been conducted on the optimal physical conditions during the feed-training period.…”