Location: Warmwater Aquaculture Research UnitTitle: Quantifying the contribution of zooplankton to channel catfish and hybrid catfish growth in nursery ponds
|MISCHKE, CHARLES - Mississippi State University|
|FILBRUN, JESSE - Eastern New Mexico University|
|LI, MENGHE - Mississippi State University|
Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2019
Publication Date: 5/18/2019
Citation: Mischke, C., Filbrun, J., Li, M., Chatakondi, N.G. 2019. Quantifying the contribution of zooplankton to channel catfish and hybrid catfish growth in nursery ponds. Aquaculture. 510:51-55.
Interpretive Summary: Channel x blue hybrid catfish constitute the largest and most valuable aquaculture industry in the United States. The present study, large natural differences in the stable carbon and nitrogen isotope ratios between zooplankton and commercial feed to quantify the contribution of these foods to growth of channel catfish and hybrid catfish were determined in nursery ponds. The results of the study support the growing evidence zooplankton management is critical to support desirable growth and survival of channel catfish and hybrid catfish in nursery ponds. The practice of feed training in indoor hatcheries before stocking the fry in ponds is recommended as both groups of fish were able to switch from feed in indoor hatchery to live prey and feed in nursery ponds. Hence, similar pond feeding strategies (35% protein dust, followed by dust and mini-pellet) for channel catfish and hybrid catfish fry is recommended for desirable growth and production of fingerlings.
Technical Abstract: Channel catfish fry rely heavily on zooplankton to support growth in nursery ponds. However, the extent of zooplankton use by hybrid (channel × blue) catfish fry is unknown. To improve feeding methods for channel and hybrid catfish in nursery ponds, we used stable C and N isotope ratios to quantify the fractional contribution of zooplankton and a commercial feed to fish growth. Channel and hybrid catfish fry had no differences in the timing and extent of zooplankton and feed use in ponds. Both fish types used zooplankton and feed equally to support growth (~50% from each source) from the time of pond stocking, and there were no differences in growth rates by length or weight. The fish used feed to support growth before they were visually observed accepting the feed at the surface of ponds 4 weeks after stocking. Zooplankton are clearly important to support desirable growth of channel and hybrid catfish fry in ponds. Thus, we recommend managers monitor densities of preferred zooplankton prey in ponds and use inorganic fertilization methods to enhance zooplankton production, as necessary. Although feed partially supported zooplankton production in this study, we caution against overfeeding, because this practice is expensive, inefficient, and risks hypoxia formation in ponds. Finding no differences in diets and growth rates between channel and hybrid catfish, we provisionally recommend managers practice similar pond management strategies for both fish types.