WEAKFISH MIGRATION IN RELATION TO ITS CONSERVATION 



There has been much speculation but little definite knowledge about 

 the migrations of the fishes which summer in the inshore waters of the 

 Middle Atlantic Bight. It has, of course, long been known that many of 

 these species migrate seasonally. For example, the bluefish, butterfish, 

 croakers, scup, sea bass, weakfish, and surimer flounder, disappear from in- 

 shore waters vdth the autumnal chilling and return lAdth vernal warming. 

 Knowledge of their winter habitat has been fragmentary. Occasional winter 

 captures of "sunmer fish" have been reported from the zone of moderate temp- 

 eratures along the edge of the continent from the latitude of Cape Hatteras 

 to the southern edge of Georges Bank. The establishment in the winter of 

 1929-30 of a winter fishery for some of these fishes off the Virginia Capes 

 (Pearson, 1932; Nesbit and Neville, 1935) and the results of tagging experi- 

 ments (Nesbit and Neville, 1935) all suggest that most individuals of the 

 several species of shore fishes migrate southward as well as offshore in 

 winter, so that the occasional fish captured along the northern part of the 

 continental edge may be regarded as stragglers . 1/ 



Foremost among the questions raised by the migrations of these fishes 

 are those concerned with the unity or diversity of the populations. It is 

 of economic as well as scientific importance to know whether or not the 

 populations of these fishes are composed of many local races, each with its 

 own peculiar migratory habits. If separate population units or races exist 

 and remain distinct throughout the summer fishing season, such conservation 

 measures as may be found desirable may be applied by each locality indepen- 

 dently. If, on the other hand, mixing occurs in summer as well as in winter, 

 local conservation measures will be ineffectual, for restrictions in one 

 locality may be expected to stimulate fishing activities elsewhere so that 

 the strain on the general population will be moderated but slightly, if at 

 all. 



For several reasons the weakfish ( Cynoscion regalis ) is a particularly 

 desirable species for study of this problem. It moves inshore for spawning 

 in summer, and withdraws in Xianter. Its scales show age marks with remark- 

 able clarity, and reveal peculiarities of surface pattern by which local 

 races may be recognized. Considered solely from the point of view of 



1/ The hydrography of the continental shelf between Cape Cod and Cape 



Hatteras has been discussed by Rathbun, 188?; Parr, 1933; Bigelow, 1926; 

 and Bigelow and Sears, 1935. The principal hydrographic features which 

 influence the movements of the fish are: (1) the range of the seasonal 

 cycle of temperature within' th6 10-fathom contour ' s so ^;reat (0° to h° C. 

 in winter, 20" to 25" in summer) that only very tolerant species can be 

 year-round residents; (2) there is a zone along the edge of the conti- 

 nent where moderate temperatures (8° co 12°) prevail with remarkably 

 little seasonal or annual variation. This offers a winter refuge for 

 species that do not tolerate near-freezing temperatures. 



