73 



that a ypar of highly successful reproduction is a decidedly rare event 

 for manv species; and that when (by a happy combination of circu.ii- 

 stances) such an event does occur, its product dominates the stoclc 

 fo- a lonff period thereafter, either until they drop out of the 

 picture by the natural d-ath rate, or until 3nother rich year class 

 is produced. Thus, the fish hatched in 1904 dominated the stock of 

 s^a-herrinff in Norwrieian vjaters until 1319, having supported the 

 fisherv for 15 yearst Had thev not been succeeded by another abun- 

 dant year class before they died (or were killed off), the Norwegian 

 He--ring Fishery would have failed utterly for the time being; and no 

 hu-nan endeavor could have staved off the cala.:iity. Off the IJewfound- 

 land coast of the Gulf of St. Lawrence the crop of 1904 was likewise 

 responsible for most of the commercial catch of herring as late as 

 1915. Even a more striking example of fluctuations in abundance is 

 afforded by the mackerel, causing vicissitudes to the fishing industry 

 that have become proverbial. Similar, if less spectacular, fluctua- 

 tions in abundance have been recorded for cod, for haddock, and tor 

 other species as far back as tho' history of the fisheries runs, and_ 

 long before the latter was intensive enough to make any serious dram 

 on the stock. 



Perhaps the decline and recovery of the Blue fish off southern 

 New England in the late 1700' s and early ISOO's is our best local 

 illustration of the fact that events of this sort may be wholly 

 independent of the acts of man, for decline, total disappearance, and 

 Subsequent recovery of this species took place before any intensive 

 fishery for its species had developed. Similarly, the recovery of the 

 stock of mackerel in North American waters, from its lowest eoo m 

 1910, occurred in the face of a very intensive fishery. In l^orway, 

 too, the historic record discloses a succession declines and recover- 

 ies in the stock of cod over a long period of years. In Scotland tne 

 Haddock failed in 1792; but recovered thereafter; the French (true) 

 sardine has also undergone wide fluctuations in abundance, while many 

 other instances of thii sort might be mentioned, the economic sequellae 

 of which have been far reaching, alternately bringing prosperity and 

 disaster to the fishermen. 



^he stock of ^ given species may also be suddenly reduced almost 

 to the vanishing point by some unfavorable shift in the environment; 

 most often by abnormally low temperatures. ^Fe have record of sucx. an 

 event as far back as 1789, when seafarers brought Dack word that the 

 surface of Barents Sea, north of Europe, was covered with 1-rge _ 

 haddock and coalfish in dying condition; prob-bly they had been chi^lle. 

 by some sporadic flooding of the bottom by kxtlc water. A more -ecen. 

 pnd much herelded instance of destruction of this same sort was that 

 of the tile fish off the eastern United States. In tne spring o^ 

 1882 vessel after vessel reported these fish dead and dying on the 

 surfac- I^ fact, the destruction was so nearly complete thatiu was 

 not until ten years later that a single live tile fish was again seen. 

 But by 1893 they were again as plentiful as ever. These events nave 

 in no way depended on the fisheries. 



Most of +he clear cases of depletion or of indirect damage by 

 industrial developments have affected species living so close to land 

 as to be especially vulnerable. In fact, it is doubtful whether t..e 

 hand of man has, up to the present time, been able appreciaoly to 

 damage the stock of any of the species that support tne great oil- 



