208 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



those mentioned above, tlie first embracing all those causes based on the 

 idea that the herrings were either destroyed or driven away by human 

 agencies, and the second embracing all those causes based on the idea 

 that the herrings had been forced to leaA^e the coast from lack of food. 

 The causes mentioned under the first heading have, generally speaking, 

 not met with universal favor, many of then defenders being led by ill- 

 concealed feelings of envy ; and the causes mentioned under the second 

 heading are generally in direct opposition to the first. Strange to say, 

 the method of explanation which has recently been adopted by G. C. 

 Cederstrom has seemingly met with some opposition by the knowledge 

 which we have gained concerning the great Bohuslan herring-fisheries, 

 that those fishing-periods lasted longest during which fishing was car- 

 ried on with the greatest zeal, whilst those were shortest during which 

 fishing was neglected." It ought scarcely to be necessary to refute this 

 theory, and as far as the above-mentioned theories of explanation are 

 concerned, we may point to the, generally speaking, reliable opinions of 

 the authors mentioned before (53). It must be granted that the influ- 

 ence of human agencies on small fisheries may be noticeable ; but their 

 influence on the great herring- fisheries is doubtless exceedingly small, 

 and can in no wise be the cause of such phenomena as the cessation 

 of the great herring-fisheries. At the present time it is very rare to 

 find any scientist who still holds to the old and fully refuted opinions. 

 50. The biological and physical causes doubtless deserve more atten- 

 tion. With regard to them a distinction may be made between the 

 theory that the herrings are periodically destroyed and that they leave 

 the coast during long intervals. KrUyer has mentioned that if a school 

 of herrings is by unfavorable weather compelled to spawn in unsuitable 

 places for several years in succession, it may be entirely destroyed or 

 at least be diminished to such a degree that the fisheries must come to 

 an end. Later, G. C. Cederstrom has thrown out the hint that unfavor- 

 able outward conditions had towards the end of the last great Bohuslan 

 fishery-period decimated the herrings and thereby brought about the 

 end of the fisheries. All the suppositions, however, cannot explain the 

 periodicity of the great herring-fisheries ; for these fisheries, as, among 

 the rest, has been said by H^filsson, Loberg, and Boecl; have come to an 

 end, not from lack of herrings, but because the herrings left those regions 

 where they had been accustomed to come. If this were not the case a 

 gradual decrease in the number of herrings ought to have been noticed 

 towards the end of a fishery-period, but nothing of the kind has ever 

 been observed. There is far greater probability in the supiDosition that 

 from some outward causes the herrings have been induced to periodic- 

 ally leave those regions which for a long time they had visited regularly. 

 The most prominent among them is this, that the herrings shoidd have 



"This supposition is by some people harmonized even with the actual deterioration 

 in the quality of the herrings which undoubtedly takes place towards the end of a 

 fishery-period. 



