EFFECTS OF CROWDING AND WATER FLOW ON GOLDEN SHINERS Notemigonus crysoleucas IN FLOW TANKS  

The golden shiner Notemigonus crysoleucas is one of the primary baitfish species raised in traditional earthen ponds in the southern United States. Following the success of raising hybrid catfish (Ictalurus punctatus x I. furcatus) in split-pond systems, efforts are underway to investigate the usage of split ponds for baitfish production. In split-pond systems fish are confined to approximately one-fifth of the pond while the remaining area serves as a water treatment area.  This purpose of this design is to augment water quality by circulation of water between the two units. The split pond design may subject golden shiners to stressors such as crowding and increased water flow. The present study was conducted to evaluate the effect of crowding and water flow on golden shiners using a flow tank model.      

Two 28-d experiments were conducted to determine the effects of 1) crowding and 2) water flow rate on the growth and physiology of golden shiners. Both studies were conducted using a common set-up and identical methods. Water was re-circulated through 12 flow tanks (300 cm x 7.5 cm x 6.25 cm; 14 L) from a 568-L head tank and exiting into a 1100-L sump. Water was pumped from the sump into the head-tank by a 0.37-kW (½ HP) submersible pump (Figure 1). A constant inflow of fresh well water into the head tank and sump were maintained. Thirty fish were stocked into each flow-tank for both experiments.

To test the effects of crowding, fish were held under three density treatments: 600, 1200, and 2400 fish/m³ with four replicates per treatment (n=12).  Water flow rate was maintained at 1.0 cm/s. To test the effects of water flow, 30 fish were held at a uniform density of 600 fish/m³ in each of the same 12 flow tanks, flow rates were adjusted to: 1, 2, and 4 cm/s, with four replicates per treatment (n=12).  At the end of each experiment, fish were subject to a 1- min acute net-handling stress. Cortisol measurements were obtained at 30 min time intervals from 0 h to 2 h. For both the experiments, growth parameters, survival rates and feed conversion ratios were measured and statistically compared across all treatment groups using one-way analysis of variance (ANOVA). Results will be presented at the conference.

Figure 1: Experimental set-up of flow tanks