THE SALT-WATER FISHERIES OF BOHUSLAN. 165 



may suddenly leave the coast from this cause. The Dutch Meteorological 

 Institute at Utrecht says, in its report of 1859, on observations made 

 during the so-called "great fisheries," "that during a thunder-storm ac- 

 companied by heavy rain the herrings do not come up to a height where 

 they can be caught till dawn"; and the Meteorological Society of Edin- 

 burgh mentions "that according to their observations there wiU be good 

 fishing the same day when a considerable thunder-storm extends over the 

 greater portion of Eastern Scotland, but that there will be scarcely any 

 fishing on the day following on that portion of the coast-waters which, 

 so to speak, forms the outer edge of the great deep." G. C. Gederstrom 

 believes that he has found " a surprising connection between the course of 

 the fish and electricity." It seems, however, that this " connection" may 

 be ascribed to other causes than the influence of "cosmic electricity." 



12. Eegarding the influence of light we possess a considerable num- 

 ber of observations, and oijinions based on them. Light is therefore 

 justly considered as one of the more important causes which exercise an 

 influence on the more or less regular course of the herrings. We shall 

 below give a full account of these observations and of the various opin- 

 ions based on them. The herring, like many of our salt-water fish, can- 

 not bear a very strong light, or prefers at any rate a dim light. Ifeu- 

 crantz therefore supposes that the glare of the lightning drives the 

 herrings into deeper water." 



It is well known that both the herring and the small herring stay in 

 deeper water during the day than during the night on account of the 

 light, although the depth, of course, varies according to the greater or 

 smaller intensity of the light. A bright moonlight *uight is therefore 

 considered less favorable for herring-fishing, because the herring stay 

 in deeper water. It is, however, just as probable that this opinion has 

 been created by the increased diificulty of catching the herrings in a 

 bright light, as by the supposition that in the darkness the herrings 

 find some protection from their pursuers, and therefore seek dark places 

 even during day-time.^^ This probably also causes the influence which 

 the varying degree of transparency of the water exercises on the fish, 

 cries, fishing always being best when the water is less transparent or 

 turbid, or when the rays of light are broken by small waves. 



The changes of light and darkness caused by the setting and rising of 

 the sun seem to have a great influence on the herring, exciting them 

 considerably and causing them to come up from the deep ; fishing with 

 floating nets is consequently most profitable at those times. If during 

 very dark nights the herrings keep in such deep water that they can- 

 not be reached with the floating nets, it happens occasionally that the 

 light of the rising moon attracts them towards the surface so the nets 



^^ To show how sensitive fish are to the influence of light, we may mention the fact, 

 that codfish kept in shallow vessels open to the siin have become blind fiom the strong 

 light. 



•■'« When seeking food the herrings are, even in day-time, not uufrequently found 

 near the surface of the water. 



