Age Determination of Hybrid Catfish Ictalurus punctatus ♀ x Ictalurus furcatus ♂ and Channel Catfish Ictalurus punctatus and Economic Evaluation of Three Strategies to Control Big Fish on Commercial Fish Farms
Type of DegreeMaster's Thesis
Fisheries and Allied Aquacultures
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The number of catfish farms in west Alabama has declined from 250 to 71 over the 2003 to 2020 period. This has been due to a variety of reasons including foreign competition, changing consumer preferences, volatile market prices, increased production costs, and live fish that exceed the maximum desirable size of the processor (i.e., Big Fish). Processing plants desire a live fish within the 0.45 – 1.81 kg range and pay a premium price for this size. Catfish products coming from live fish > 1.81 kg cannot be processed nor sold easily by processing plants to their established markets. This results in farmers receiving a reduced price or no compensation at all for Big Fish. Catfish that routinely escape harvest remain in the pond over multiple production cycles resulting in Big Fish that cause financial and production issues, such as increased feeding that leads to higher costs and deteriorating feed conversion ratios. Additionally, it is likely Big Fish consume smaller catfish in the pond. A two-year study was conducted to determine the age structure of different size classes of Channel Catfish Ictalurus punctatus and hybrid catfish Ictalurus punctatus ♀ x Ictalurus furcatus found in commercial production ponds and to economically evaluate management strategies to control Big Fish. In 2018, otoliths were collected from 287 catfish (153 Channel Catfish and 134 hybrid catfish ranging from 0.45 – 20.6 kg) from commercial catfish farms in west Alabama to determine their age and growth rates. Results of this study indicate that hybrid catfish had a faster growth rate compared to Channel Catfish at every age class sampled during this study. Channel Catfish and hybrid catfish could grow into Big Fish in 1.5 years and 2.6 years, respectively. Thus, it is recommended that both species should be harvested after one production cycle when fish are approximately 2 years of age to avoid becoming Big Fish. In year 2, a survey titled “2019 Big Fish Survey of the Alabama Catfish Industry” was sent to catfish producers in west Alabama. Its objective was to obtain information on catfish management strategies, production characteristics, and their methods of controlling Big Fish. Three management strategies used to control Big Fish based on survey results were analyzed economically. Each strategy had the goal of zeroing out fish in the pond before the next fish crop was stocked. The control strategies included 1) additional re-seinings of the pond after the initial harvest, 2) using rotenone after the pond has been completely harvested of premium sized fish, and 3) draining the pond to renovate its bottom into a smooth surface to improve seining efficiency. Using survey data and partial budgeting techniques, we were able to establish the costs and benefits of each management strategy. The most cost-effective solution was to hire a custom seine crew for additional re-seining after the initial harvest and this approach will work well with single-batch (hybrid catfish) and multiple-batch (Channel Catfish) systems. The second least expensive approach was the use of rotenone after initial harvest and re-seining, and this approach will work with single-batch (hybrid catfish) systems only but is not viable for the multiple-batch (Channel Catfish) system. Multiple-batch systems have several batches of different age/size classes of fish in the pond simultaneously and use of rotenone would kill fish destined for future harvesting. The most expensive solution is the complete draining and re-working of the pond bottom, this approach will work well with single-batch (hybrid catfish) and multiple-batch (Channel Catfish) systems. However, based on farmer interviews and survey results, we believe the best long-term solution forward in regards to Big Fish is to re-work pond bottoms as the opportunity arises and cash flow permits, to increase seining efficiency. In the meantime, additional re-seines to remove Big Fish missed from commercial harvests is a good management strategy to reduce and minimize Big Fish on farms. There is no easy solution to the Big Fish problem and a multi-faceted approach will be required to manage this issue.