VI 



INTRODUCTIOlSr. 



Menhaden appeared in Washington (I). C.) markets February 25, 1879, 

 nearly three weeks in advance of the •'branch-herring," four in advance of 

 the shad, and eight before the "glut-herring."' 



The cause of the unusual movements of the menhaden in 1879 is dif- 

 ficult to ascertain. The idea has been suggested that they were driven 

 back by the schools of blue-fish, which, by this theory, are supposed to 

 have approached the coast in advance of them. This explanation seems 

 scarcely satisfactory, for there is no evidence that the blue-fish were earlier 

 than usual. On the other hand, there is reason to doubt whether blue-fish 

 ever come near the coast until they are lured in by the presence of their 

 favorite food. See the table, on page 46, which shows that for thirteen 

 years the menhaden always entered Waquoit Bay from five to twenty days 

 in advance of the blue-fish. In fact blue-fish, as well as menhaden, have 

 been unusually scarce north of (Jape Cod in 1879. 



A more satisfactory explanation is to be found in the unusual coldness 

 of the water in the Gulf of Maine. The following preliminary conclusions 

 have been reached, but I hope in future to be able to discuss the subject 

 more at length : 



The season of 1878, in Maine, was fairly successful, the three sum- 

 mer months being warmer than in ,1S77, but cooler than in 1876. The 

 al>sence of the menhaden schools, north of Cape Cod, in 1879, may 

 be explained by the study of the temperatures of the water of the 

 Gulf of Maine, as indicated by the observations made in Portland harbor. 

 The averages for the three summer months are as follows, the nunun";itor 

 of the fraction being the average surface temperature, the denominator 

 that of the bottom : 



1876, 



62.5 

 57.9 



1877, 



58.5 



1878, 



56.7 



G1.5 

 58.1 



1879, 



56.1 

 54.6 



The average for the three summer months of 1879 is less than that of 

 June, 1876. In August, 1878, there Avas a very rapid fall in the tempera- 

 tures of the surface in the Gulf of Maine, so that the average of that 

 month was less than that of July, instead of being higher, as is usual. 

 This, ])erhaps, had the effect of driving the fish into the Avarmer Avater of 

 the bays and estuaries. The monthly averages for 1876, 1877, 1878, and 

 1879, are as folloAvs : 



1876, June, 



1877, June, 



1878, June, 



}879, June, 



56.9 



54.0 

 54.9 



53.3 



56.8 



55.3 

 53.9 



51,7 



July, 



July, 



July. 



July, 



66.7 



59.4 



58.1 



56.3 

 66.9 



59.3 

 55.9 



54,1 



August, 



August, 



August, 



August, 



63.9 



60.4 

 63.4 



60.6 

 60.7 



59.9 

 59.6 



08^ 



