Location: Warmwater Aquaculture Research Unit2011 Annual Report
1a. Objectives (from AD-416)
Determine steroid levels in reproductive catfish to determine early signs of reproductive success. Evaluate the use of ultrasound estimation of ovary size, level of plasma steroids, group/family of origin, and body weight as predictors of incidence and timing of pond spawning of 2 and 3 year old channel catfish. Evaluate use of ultrasound imaging to sort female channel catfish broodfish on commercial farms into two groups based on estimated ovary size (large vs. small ovaries), and compare steroid levels and incidence and time of spawning of these two groups. Determine the influence of chemical, biological and environmental factors on channel catfish respiration, growth and production, and develop and test practical management methods to minimize limits on production. Induce early maturation in channel catfish.
1b. Approach (from AD-416)
Catfish blood will be analyzed for steroid levels using HPLC/MS. Ultrasound images of female channel catfish ovaries and plasma steroid hormone levels of male and female channel catfish will be collected prior to the spawning season. Fish will be allowed to mate at random in spawning ponds and parentage of spawns will be determined via molecular markers. Statistical analysis will be conducted to determine if ultrasound imaging or steroid hormone levels are predictive of spawning time and incidence. Female channel catfish will be sorted based on ultrasound image predicted ovary size on commercial catfish farms to determine if ultrasound image of ovary size can be used to predict spawning success of females on commercial catfish farms. Ten standard hatchery troughs will be operated during the 2008 spawning season. Spawns will be weighed and sampled prior to being placed in the incubator, and the number of sac fry produced from each trough will be determined, allowing for a calculation of hatch rate. A similar number of troughs will be operated and sampled using the traditional method. Water flow rates, dissolved oxygen concentrations, and water temperature will be monitored. Fish will be exposed to different environmental temperature regimes.
3. Progress Report
Channel catfish were first spawned in captivity nearly a century ago and the methods have changed little over the years. Normally 10-12 spawns (roughly 18 pounds - 250,000 eggs) are held in each 100-gallon hatchery trough, with a water flow of 5 gallons per minute at 78º-82ºF. This incubation system is functional, but limited. Increased egg loading greatly restricts water circulation between and through the spawns resulting in a low dissolved oxygen concentration and dead eggs in the center of the spawns. Those areas may serve as foci for fungal and bacterial infection, greatly reducing the hatch rate in the entire trough. We have developed a new incubation system, the “See-Saw”, that efficiently forces water and oxygen through the egg masses to increase the efficiency of commercial catfish hatcheries. A prototype of the new incubator underwent preliminary testing during the 2007 and 2008 spawning seasons. The first trial (2007) determined the appropriate cycle interval to be approximately ten seconds. In the second trial (2008) the See-Saw was tested with twice the egg density as is recommended. Those preliminary studies were published and describe the construction and operation of the prototype incubator in more detail. In cooperation with Needmore Fisheries LLC, Glen Allen, Mississippi, the first comparative trial was conducted. Pairs of troughs (one control and one See-Saw, with 4 troughs for each treatment) were loaded with 25.6 ± 0.5 egg masses per trough (474,947 ± 3002 and 472,878 ± 3892 eggs per trough, respectively). Survival to swim-up stage averaged 53.6 ± 7.1% in the See-Saw, versus 23.3 ± 6.5% for the control troughs, a 2.3-fold difference. In Year 2 of the project (2010 spawning season) we loaded See-Saws (n=5 troughs for each treatment) with 15.0 ± 0.1 lb (220,300 eggs), 30.1 ± 0.1 lb (447,000 eggs), 45.1 ± 0.1 lb (669,600 eggs), and 60.1 ± 0.0 lb (893,100 eggs) of spawns. Water flow into the troughs averaged 2.1 gal/min, roughly half of the rate recommended for commercial hatcheries. The 15, 30, and 45 lb troughs produced an average of 132,700, 263,800, and 429,400 swim-up fry (survival from egg of 60 ± 9%, 59 ± 6%, and 64 ± 4%, respectively, similar to values reported in commercial hatcheries). However, the 60 lb treatment produced only 417,200 swim-up fry (survival of 46 ± 8%). The results indicated that both hatchery space and water use would be maximized with See-Saw incubators loaded at the 45 lb rate without impacting hatch rate or survival to swim-up. The use of this incubator across the commercial industry would result in considerable savings in water alone, particularly for those hatcheries that need to heat their well water. This incubator may have even greater application in the numerous state and federal hatcheries which are tasked with hatching a growing number of fish species. The See-Saw can reduce both the space and water flow needed to meet their channel catfish production quota, making those resources available for other priority species. ADODR used site visit, email and telephone conferences to monitor activities of the project.