Producing Hybrid Catfish Fry: Workshop Manual

Producing Hybrid Catfish Fry: Workshop Manual - By Dr. Brian Bosworth and Dr. Brian Small, USDA ARS and Dr. James Steeby and Dr. Jimmy Avery, Mississippi State University - Production of hybrids between the channel catfish (Ictalurus punctatus) and the blue catfish (Ictalurus furcatus) was reported as early as 1966 (Giudice).

Contents

Techniques for Producing Hybrid Catfish Fry

• Overview
• Broodstock Care/selection
• Hormone Dosage and Administration
• Testes Collection and Sperm Preparation
• Timing Ovulation
• Stripping and Fertilization
• Literature Cited

Care of Hybrid Catfish Egg Masses

• Factors Leading to Dead Eggs and Disease
• Disease Causing Organisms
• Chemical Disinfection
• Summary
• Additional Resources

Appendix

• Vendors/supply list
• Hanks Buffered Salt Solution (HBSS) recipe
• Phosphate Buffered Saline (PBS), vendors and recipe
• INAD (Investigational New Animal Drug) information and forms
• Workshop Slide Presentation

SRAC Publications

• # 1802 - Channel Catfish Broodfish Management.
• # 1803 - Channel Catfish Broodfish and Hatchery Management
• # 421 - Introduction to Hormone-Induced Spawning of Fish
• # 422 - Capturing, Handling, Transporting, Injecting and Holding Brood Fish for Induced Spawning
• # 424 - Hormonal Control of Reproduction in Fish for Induced Spawning
• # 425 - Hormone Preparation, Dosage Calculation, and Injection Techniques for Induced Spawning of Fish
• # 426 - Techniques for Taking and Fertilizing the Spawn of Fish
• # 190 - Production of Hybrid Catfish
• SRAC 17th Annual Progress Report Improving Reproductive Efficiency to
• Produce Channel x Blue Hybrid Catfish Fry pp 61-76

Introduction

Production of Eggs and Fingerlings
Research to develop and refine methods for producing hybrids and to evaluate their performance for economically important traits has continued until present. Although researchers from several state and federal agencies have conducted research with hybrids, much of the research on hybrids has been done at Auburn University. The hybrid generally performs better than either parent species for several important production traits including survival, growth, disease resistance, and carcass yield (Giudice 1966, Yant et al. 1975, Dunham et al. 1983, Dunham et al. 1987, Dunham et al. 1990, Ramboux 1990, Wolters et al. 1996, Dunham and Argue 1998, Dunham and Brummett 1999, Chatakondi et al.

2000, Bosworth et al. 2004, Li et al. 2004). The hybrid produced by crossing a female channel catfish and blue male catfish is the mostly commonly produced hybrid and tends to be easier to produce and performs better than the blue catfish female x channel catfish male hybrid (Dunham et al.1982). Therefore, throughout this manual the term hybrid refers to the channel catfish female x blue catfish male hybrid.

The primary constraint to commercial production of the hybrid has been the lack of reliable, cost-effective methods for producing large quantities of fry needed for commercial catfish farming. However, continued problems with production of channel catfish, primarily related to diseases, coupled with refinements of techniques for producing hybrids have spurred renewed interest in use of hybrids for commercial production.

Traditional pond-spawning, which is effectively used to produce channel catfish fry, is ineffective for consistent, large-scale production of hybrid fry because of reproductive barriers (behavioral, physiological etc.) that prevent spawning between blue and channel catfish. Although there have been reports of successful spawning in brood ponds stocked with male blue catfish and female channel catfish, the occurrence of pond-spawning is very rare and not reliable for commercial hatchery production. Unless some future development dramatically improves the spawning rate in traditional brood ponds, production of hybrid fry will depend on the use of hormones to induce ovulation (final maturation and release of eggs) in females, manual stripping of eggs, and manual fertilization of the eggs with blue catfish sperm (Tave and Smitherman 1982, Dunham et al. 2000).

Hormone-induced spawning is a commonly used technique for production of fry of many fish species and a variety of compounds (common carp pituitary extract - CCP, lutenizing hormone releasing hormone analog LHRHa, human chorionic gonadotropin) have been successfully used for inducing ovulation in catfish. These compounds initiate the chain of events that lead to ovulation and release of eggs. The two most commonly used, and presumably most effective, compounds for inducing ovulation in channel catfish are CCP and LHRHa. Therefore the methods section of this manual will focus on the use of these two compounds.

Considerations in Using Hybrids in Growout Ponds

While the hybrid has several advantages in disease resistance, growth, and ease of catch, experienced hybrid producers report that there will have to be adjustments to the typical channel catfish production system to successfully raise hybrids. Due to the smaller size of the hybrids head compared to a channel catfish, harvesting can be difficult if traditional mesh sizes are used (especially when using grading nets with larger than 1-inch mesh). Release of gilled fish often results in subsequent Columnaris infections, therefore complete harvest of all fish that have been caught is recommended. This may require increased flexibility on the part of the processor.

Hybrids are also reported to congregate nearer the water surface than channel catfish when needing aeration. Also, if improved growth and survival is realized, additional aeration will be required. Most hybrid growers recommend 3-4 hp of paddlewheel aeration per acre. The spines of the hybrid are sharp and can be difficult to collapse compared with channel catfish. Workers should take special care when handling the hybrids. If possible contact a producer that has already grown hybrids and consult with them on other aspects.

This Workshop

The goal of this workshop is to present practical information and hands-on experience related to hormone-induced spawning and production of hybrid catfish fry. However, hormone-induced spawning of catfish is still part art and part science. The information supplied in the workshop provides basic information on techniques used for production of hybrid fry, but experience is the best way to learn how to produce hybrids. Start small, get a feel for the process and gain some experience, and alter the protocols and techniques as you see fit. Even people with substantial experience have variable results in producing hybrid fry, so dont be discouraged if your early results are less than what you expected.

Also remember that the content emphasized in the workshop is based on the authors experience and knowledge. Other people may use variations in techniques and have different opinions on which issues are more or less important than those highlighted in this manual. You would be well served to gather information, advice, and opinions on the production of hybrid fry from as many sources as possible. We hope you find the workshop to be informative and enjoyable.

Further Information

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May 2006