. Commercial fisheries review. Fisheries; Fish trade. Fig. 3 - Dolphins photographed from observation capsule. Jack Mackerel Schools Observed The Sea-See made three 1-day trips near the Isthmus of Catalina Island. Jack mackerel schools were located on 2 of the 3. Under- water observations were made and photos taken of the schools. Some of the stereo- photos taken during the day were good enough for making estimates of interfish distances; these will be compared with measurements made in the La Jolla lab. Feeding The schools of about 500 individuals (60- 82 mm SL) remained at 5 to 25 feet. Fish
. Commercial fisheries review. Fisheries; Fish trade. Fig. 3 - Dolphins photographed from observation capsule. Jack Mackerel Schools Observed The Sea-See made three 1-day trips near the Isthmus of Catalina Island. Jack mackerel schools were located on 2 of the 3. Under- water observations were made and photos taken of the schools. Some of the stereo- photos taken during the day were good enough for making estimates of interfish distances; these will be compared with measurements made in the La Jolla lab. Feeding The schools of about 500 individuals (60- 82 mm SL) remained at 5 to 25 feet. Fish fed through the day. Feeding frequencies ranged from 0 in a interval to 29 feeding snaps in a interval; the median frequency was 14 snaps per minute. Stomach contents of 4 feeding fish were taken and all were full. One stomach was examined. It contained 1,454 food items; 88% were cope- pods of 4 genera. "This preliminary experiment demon- strated that feeding experiments incorporat- ing behavioral observations can be conducted in the field on a pelagic marine ; Strobe Photos Strobe photos were taken at night where schools had been observed during the day. The purpose was to determine if jack mack- erel schools continued to school at night. Photos were taken at 1-minute intervals from 5:30-6 Jack mackerel schools were in many photos. The latest in the even- ing these schools were photographed was 5:57 , about 8 minutes after end of nau- tical twilight. The sky was clear but moon- less. Fig. 2 - The octagonal underwater viewing Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. National Marine Fisheries Service; U. S. Fish and Wildlife Service; United States. Bureau of Commericial Fisheries. [Washington] : National Marine Fisheries Service; [fo
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