Clarity of OTC Mark on Northern Pike Otoliths Using Different Microscope Filters

Presenter Information

Merissa Oswald, Minnesota State University, Mankato

Location

CSU 284A

Start Date

5-4-2010 1:00 PM

End Date

5-4-2010 3:00 PM

Student's Major

Biological Sciences

Student's College

Science, Engineering and Technology

Mentor's Name

Shannon Fisher

Mentor's Department

Biological Sciences

Mentor's College

Science, Engineering and Technology

Description

Oxytetracycline (OTC) is used to mark bony structures on fish to estimate the age of the fish. The inner ear bones, otoliths, are used to read OTC marking because otoliths are the easiest bony structure to get a quality age reading. The prepared otolith is placed under a microscope with a filter and ultraviolet light to read the OTC mark. The filter gives the otolith a color and the mark a different color. Different filters exist. One filter makes the otolith green and the OTC mark yellow, while another filter makes the otolith blue and the OTC mark red. I investigated the clarity of the OTC marks using 3 different filters. Northern pike were marked with OTC as fingerlings and stocked in a rearing pond. The age zero fish were then gathered and the otoliths were removed, dried, sanded, and fixed to a slide. The OTC markers were read under 3 different filters and given a score of 0 to 4 (0 being no mark and 4 being a very distinct mark) to analyze the clarity of the OTC mark under each filter. More than one person read each mark to eliminate human eye bias. The results are still being collected. A study on efficiency of the different filters has not been conducted before. The goal of this experiment was to eliminate bias readings due to poor clarity of OTC marks. Greater contrast between colors the filter creates could produce more distinguishable marks and result in more accurate fish aging.