€ GEORGE V SESSIONAL PAPER No. 38a A. 1916 



XI. 



ARE MI-GEATING EELS DETERRED BY A RANGE OF LIGHTS-REPORT 



ON EXPERIMENTAL TESTS. 



By PitoF. Philip Gov, Ph. D., etc., University of New Bninswicl: 



Some one had ventured the opinion, on what grounds I know not, that such a 

 device is eifectual, and I was requested to test it by a series of experiments at the 

 Biological Station, St. Andrews, in the summer of 1913. As the common eel, Anguilla 

 chrysopa, is known to be a persistent and voracious spawn-eater, its exclusion by any 

 means from the spawning grounds of lake and river food-fishes would be of vast 

 importance to thtose fisheries, and give a stimulus to the restocking of new or depleted 

 waters. 



No fact is better known to the small boy who builds his fire at the water's edge 

 after night, than that eels are attracted by the light; but will they come fully into 

 and pass through it? 



Two series of experiments .were conducted : the first, in one of the tanks in the 

 laboratorj-; the second on a larger scale and under more normal conditions in the 

 outlook of Eocabec lake, 12 miles from the station. 



Experiment I, July 27. — In a tray, 7 feet by 3 feet and 3 inches deep, were placed 

 five eels which had been taken from a fresh-water lake, and gradually passed through 

 water of increasing degrees of salinity until the average w^as reached. Water was 

 admitted through a tap, provided with a jet attachment, and the stream struck the 

 surface at a very acute angle, keeping the tray well oxygenated. Across the tank, and 

 resting on the sides 2 J feet from the upper end, was a broad board on which an 

 acetylene lamp stood, screened behind so that the lower part was dark, the other 

 brightly lighted, and the line of demarcation between the two sharp and v/ell defined. 

 It was remarlrable how soon the fish seemed to accommodate themselves to the 

 increasingly salt medium, which at first made them apparently very uncomfortable 

 I'lUt at the end of two or three hours failed to have any apparent disturbing effect at 

 all. One fish, a very large one, had been in the tray two days before the experiment 

 began; the rest were placed there in the afternoon of the evening when the first trial 

 was made. 



July 27. 



Experiment I. 



At 9 p.m. the fish were screened to the lower end of the tray, the laboratory 

 (larKened and the lamp lighted. 

 9.26. An eel moved into the light, swam to the end of the illuminated space, turned 

 and disappeared in darkness. This was the large one which had been imprisoned 

 two days. 

 y.oO. Another moved half-way into the light and rested there. 



9.36. It swam out into the lighted area, turned, stopped for a minute or two, and 

 disappeared. 

 ,10.50, One has pushed its nose to the illuminated line. 

 J 0.52. It dropped back into darkness. 



11.30. Another, the large one, has drawn up close to the lighted line. 

 11.45. Another has moved up to the same place. 

 38a— 8J 



