COACTION IN LAMP-COMMUNITIES 



By HiROSHi Maeda 



Shimonoseki College of Fisheries 

 Yamagticki Prefecture, Japan 



Besides many investigations relating to the fish-gathering lamp on 

 5uch items as the light source, condition of light in water, phototaxis 

 of fishes and the methods of fishing, there is an interesting ecological 

 article worked by Hardenberg (1935) on shoals assembling around the 

 lamp. The effect of the fish-gathering lamp is nothing but merely a 

 simple artificial change of the light, one of the physical environmental 

 factors, to gather fishes. Thus, the mechanism of gathering fishes is con- 

 sidered to be based primarily on the phototaxis of some animals. It 

 is, however, quite uncertain whether the behaviors of animals in the 

 natural environment, which appear as the results of complex inter- 

 action of many factors, may accord or not with those observed in the 

 laboratory under special experimental conditions, namely, only one in- 

 dividual or one sort of fish is treated. It is reasonably expected that 

 the coaction of fishes may be modified by light and that the existence 

 of different sorts of animals may cause the phototaxis for some fishes, 

 lor instance, fishermen use "shirasu" (larval fish, particularly sardine 

 or anchovy) or mysids as food for fishes to keep the shoal stable under 

 the lamp; zoo- and phyto-plankton feeders, such as Engraulis and Sto- 

 lephorus, are changed into pure zoo-plankton feeders under the lamp 

 and take smaller planktonic crustaceans assembling around the lamp, 

 and some fishes showing the negative phototaxis in experimental con- 

 dition, many benthonic fishes and higher predators, may act photoposi- 

 tively under the lamp where many prey animals are assembling. Thus, 

 the coaction between fishes around the light under the natural condi- 

 tion must be investigated at first, when we research the cause of the 

 fluctuation found in caches by lamp method. The effect of light upon 

 fishes from the synecological point of view will be understood correctly 

 solely when the interrelation of animals under the light is fully com- 

 pared with that under the non-light condition. However, I can here 

 refer only to the phenomenon observed under the lamp. 



In the following, I wish to give first the outline of coaction of 

 lamp-communities taking the most complex case observed in Shira- 

 hama (Wakayama-ken) as an example, and then show briefly some 



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