Simulation Modeling of the Cryopreservation of Xiphophorus Germplasm

To date, there has only been one published study that applied simulation modelling to cryopreservation in an aquatic species (blue catfish). Catfish must be dissected to remove the testis which is crushed to obtain sperm, and generally testes from different males are not pooled. Sperm from other fishes, such as salmon can be dry stripped which is less labor intensive than dissection. Small-bodied fish such as Xiphophorus must be dissected, and the testes pooled to create a single sample. These examples of differences in processing and labor demonstrates the need to develop simulation models for various species. The goal of this project was to model the cryopreservation processes of the live-bearing genus Xiphophorus. The objectives were to: 1) develop a list of specific activities during cryopreservation and record processing times, personnel involved, supply costs, and sample quality for each activity; 2) predict the maximum output for an 8-hr day with 2 dissectors and 1 freezing operator, and 3) analyze how increasing the number of dissectors affects labor costs and output. ARENA software (Rockwell Automation, Inc.) was used to create the model (Fig. 1). After processing times for each step were recorded, distributions were generated using ARENA Input Analyzer. After 50 simulation replications, the model predicted that 224 fish could be processed in an 8-hr day with 2 dissectors and 1 freezing operator. This resulted in a labor cost of $165 and supply cost of $113. Increasing the number of dissectors resulted in 330 fish processed at a labor cost of $247 for 3 dissectors and 400 fish processed at a labor cost of $319 for 4 dissectors. After 4 dissectors, only 410 fish were processed at a labor cost of $389 for 5 dissectors and 415 fish were processed at a labor cost of $450 for 6 dissectors. These simulations cam play a major role in planning the distribution of labor among different processes, estimated how long it will take to complete the process for a range of sample numbers, and the costs vs. benefits associated with labor and supplies. Mimicking real working situations can also help identify bottlenecks otherwise not foreseeable. Trips can be better planned when traveling to fish farms or hatcheries to cryopreserve onsite, saving time, money, and enabling of economies of scale.