The Occurrence of Blindness in the Black Bullhead, lctalurus melas (Rafinesque), of East Okoboji Lake, Iowa

• Main Author: Mayhew, James
• Format: Text
• Language: English
• Published: UNI ScholarWorks 1957
• Subjects: Gar’; Gunter; Gar Lake; Red drum
• Online Access: https://scholarworks.uni.edu/pias/vol64/iss1/87; https://scholarworks.uni.edu/context/pias/article/2858/viewcontent/84_The_Occurrence_of_Blindness_in_the_Black.pdf

During the summer of 1954 anglers reported numerous blind bullheads at East Okoboji Lake, Dickinson County, Iowa. Eventually one of these specimens was brought to the State Conservation Commission Biology Laboratory for examination. Blindness, of course, is not uncommon in fishes, but this type was apparently due to the complete absence of functional eyes. Gunter (1956) has reported on a red drum, from Abazon Bay, Texas, with a similar sightless condition. With evidence suggesting that blindness was rather common in East Okoboji, special attention was given to the bullheads captured during the annual fisheries survey of the lake. From the 1954 survey seine hauls, 2,753 bullheads were examined, of which 27 blind individuals were observed. One additional blind specimen was caught in Upper Gar Lake which connects with East Okoboji on the south. In 1955, special attention was again given to the bullheads captured during the survey. In six seine hauls, 3,646 adult bullheads were examined and 31 sightless fish were obtained. Several thousand immature specimens were also examined without finding apparent ophthalmological disturbances. The blind and normal individuals were easily separated since the skin of the sightless fish is very heavily pigmented making them appear much darker than the normal specimens. Creel census clerks reported approximately ten more of these sightless fish in anglers'' catches. Fourteen blind bullheads were preserved or frozen in an effort to determine: (1) the cause of the apparent lack of functional eyes, (2) the age and growth in comparison to normal bullheads, and (3) the physical condition of the blind fish to determine if the blindness had affected feeding habits enough to alter the well-being of the fish.