RESPONSES OF MARINE ORGANISMS DURING THE SOLAR ECLIPSE OF JULY 1963 



By Bernard E. Skud, Fishery Biologist 

 Bureau of Commercial Fisheries Biological Laboratory 

 BooTHBAY Harbor, Maine 04575 



ABSTRACT 



Biological and physical observations and measurements 

 were made on the day before and on the day of a total 

 eclipse of the sun, July 19-20, 1963. Totality occurred at 

 1745 hours (e.d.t. ), and observations continued through 

 sunset on both days and in two locations — Bar Harbor and 

 Boothbay Harbor, Maine. Plankton was collected at half- 

 hour intervals, and the activity of herring ( Clupea haren- 

 gus harengus ) and green crabs ( Carcinus maenas ) was 

 recorded every 15 minutes. Collections of physical data 

 included surface and subsurface illuminance, air and water 

 temperature, salinity, barometric pressure, cloud cover, visi- 

 bility, and tidal data. 



At totality and sunset, the volumes of zooplankton in the 

 surface waters decreased. The responses of copepods varied 

 with the species. Pseudocalanus minutus and Acarlia 



longiremis showed the most pronounced response and 

 moved towards the surface. Females of Acartia were more 

 active than the males. The reactions of other zooplankters 

 were either weak or ill-defined. Herring began schooling 

 near the surface at totality; this behavior, though not as 

 strong, was comparable to that observed at sunset. Green 

 crabs were not active during the eclipse, but were very 

 active after sunset. Similarly, strong echo-tracings were 

 documented after sunset but none were recorded at totality. 

 Apparently the duration of the eclipse was too short or the 

 light intensity too high, or both, to elicit responses from 

 some organisms. 



Observations from earlier eclipse studies of marine 

 organisms are discussed and comparisons are made with 

 other field and laboratory studies of behavior in relation 

 to environmental changes. 



Animal behavior during solar eclipses has 

 attracted the interest of scientists and natural- 

 ists, alike, but relatively few observations of 

 aquatic organisms, particularly marine an- 

 imals, have been published. A discussion of 

 this lack at a meeting of the Oceanographic 

 Committee of the National Academy of 

 Sciences in 1962 provided the impetus to un- 

 dertake the observations reported in this 

 paper. 



The fevi^ specific references to aquatic ob- 

 servations during solar ecHpses generally failed 

 to include adequate definition of the physical 

 conditions. Wheeler, MacCoy, Griscom, Allen, 

 and Coolidge (1935) reported on the behavior 

 of fishes and amphibians as observed by game 

 wardens and the interested public during the 

 eclipse of 1932 in the United States. These 

 reports included remarks about feeding habits 

 of freshwater "trout" and "minnows," re- 

 sponses to angling lures, and unusual activity 

 such as pickerel jumping out of the water, and 

 a goldfish eating the tail of another in an 



MARINE ORGANISMS DURING SOLAR ECLIPSE 



aquarium. E. E. Dissell (personal communica- 

 tion, Portland, Maine) reported that a school 

 of pollock (Pollachius virens) surfaced during 

 the 1932 eclipse — the earliest observation I 

 located for a marine fish. Some of these reports 

 suggest a suppression of activity at totality and 

 others an increased level of activity; but most 

 of the reports were casual observations by lay- 

 men and the significance of the observations is 

 limited. 



Probably the first carefully planned series of 

 observations was made by Mori (1939), dur- 

 ing the 1936 eclipse in Japan. He studied the 

 responses of insects and birds at totality and 

 mentioned the behavior of the sandhopper, 

 Orchestia sp., and the migration of eye pigment 

 in the crayfish, Cambaroides japonicus. He 

 also included a brief reference to responses of 

 other crustaceans and several fishes. Weber 

 (1952), though mostly concerned with terres- 

 trial organisms, concentrated his efforts on 

 species whose normal behavior was well known 

 and recorded changes in temperature, light, and 



259 



Published June 1967. 



