158 FISHING-GKOUNDS OF NORTU AMERICA. 



that the tirst schools appear iu Chesapeake Bay in March aad April, on the coast of New Jersey 

 iu April aud early May, and on the south coast of New England in late April and May, oti' Cape 

 Ann about the middle of May, and in the Gulf of Maine about the latter part of May and the 

 first of June. Keturniug, they leave Maine in late September and October ; Massachusetts in 

 October, November, and December; Long Island Sound and vicinity in November and December: 

 Chesapeake Bay in December, and Cape Hatteras iu January. Farther to the south they appear 

 to remain more or less constantly throughout the year." 



In his concluding remarks the same writer states that "these facts [which he sets forth in 

 considerable detail] appear to indicate that under ordinary circumstances the menhaden prefers a 

 temperature of 00° to 70° Fahrenheit. When the rising temperature of spring has passed the 

 limit of 50° to 51°, the fish are certain to appear, and when the falling temperature of autumn 

 reaches that point, their departure is equally sure, though a few individuals may linger in waters 

 not congenial to them. The opposite limit seems to be marked by the line of 80° or perhaps 75°. 

 An easterly or northerly wind, lowering temporarily the surface temperature, causes the schools 

 to sink below the surface. The chill of night also drives them down. These conclusions are not 

 to be regarded as final. The movements of the fish about Cape Hatteras are very puzzling, and 

 need to be intei'preted by a series of careful temperature observations." 



More recently similar comparisons of water temperatures have been made by Col. JIarshall 

 McDonald with respect to the shad and river herrings or alewives,* the observations he makes 

 use of being relatively more extensive than was the case in Mr. Goode's studies of the menhaden. 

 His observations are restricted to the Chesapeake Bay region, with special reference to the Poto- 

 mac River, and are accomjianied by instructive diagrams, on which the relations of temperature to 

 the abundance of the two species of herring and the shad are graphically represented. 



His final conclusions are as follows : " The diagram showing fluctuations of water temperature 

 in the Chesapeake Bay region furnishes very interesting and suggestive data for discussion. 

 During the winter months the water temperatures on the ocean plateau, outside of the capes, is 

 higher than that of Chesapeake Bay or the Potomac River. The latter part of February or early 

 in March the temperature of the bay waters rises above that of the ocean waters outside. Coincident 

 with this the shad make their appearance in the Chesapeake and are taken in the pounds which 

 are set in salt-water along the shores of the bay. About the first of April the temperature of tlie 

 water in the Potomac River rises above the temperature of the water in the bay. Coincident with 

 this is the beginning of the shad season in the river. The lesson taught by the diagram is that shad 

 do not enter our rivers to spawn until the temperature of the river waters is higher than that of the 

 salt- water from which they come. Should the waters of either the Potomac or Susquehanna continue 

 during the season at a lower temiierature than those of the bay, we would liave no run either of 

 shad or glut herring during tlie season." 



Our object in prefacing this introduction with the above extracts from two of the most 

 important contributions on the subject of water temperatures in their relation to the migration 

 of fishes, has been to give a practical illustration of the great value of such studies, which have 

 been strangely neglected by investigators. With respect to the oceanic species, there are, of 

 necessity, many difQculties, some of them insurmountable, iu the way of obtaining observations, 

 as permanent stations for that purpose must be located mostly on or very near the coast, while 

 the larger schools of fishes often remain some distance from the land. River stations for observ- 



"The Shad — Clxpea sapidissima, by Marshall McDonald. The Fisheries and Fishery Industries of llio United 

 States, by GeorRe Brown Goodeand a staff of associates. Section I : Natural History of Aquatic Animals, pp. ,')94-607, 

 plates 214, 215. Washington, 1884. Also in Report United States Commissioner of Fish and Fisheries for 1883 (1885), 

 p. 1034, pi. 1. 



