OFFSHORE DISTRIBUTION OF ALEWIFE, ALOSA PSEUDOHARENGUS, 



AND BLUEBACK HERRING, ALOSA AESTIVALIS, 



ALONG THE ATLANTIC COAST 



Richard J. Neves' 



ABSTRACT 



This study of the offshore distribution of alewife, Alosa pseudoharengus, and blueback herring, A. 

 aestivalis, in the Atlantic Ocean was based on catch data collected over the 16-year period 1963-78 

 during bottom trawl surveys by the National Marine Fisheries Service and its predecessor agency. All 

 catches of the two species were made where bottom water temperatures ranged from 2° to 17° C, and 

 catches were most frequent at bottom temperatures between 4° and 7° C. Most catches of both species 

 were made at stations where depth was less than 100 m. Chi-square analyses indicated that alewives 

 were captured significantly more often than expected in the 56 to 110 m depth stratum and blueback 

 herring in the 27 to 55 m stratum (P-^0.01). During summer and autumn, all catches ofthe two species 

 were confined to the region north of latitude 40° north in three general areas: Nantucket Shoals, 

 Georges Bank, and the perimeter ofthe Gulf of Maine (especially in autumn along the northwestern 

 edge of the gulf). Winter catches were between latitude 40° and 43° north, and spring catches were 

 distributed throughout the continental shelf area between Cape Hatteras, N.C., and Nova Scotia. 

 Previous studies on juveniles, food of adults, and differences in time of capture during National Marine 

 Fisheries Service surveys indicated that these species are vertical migrators, apparently following the 

 diel movements of zooplankton in the water column. 



The alewife, Alosa pseudoharengus , and blueback 

 herring, A. aestivalis, are anadromous clupeids 

 that support substantial commercial fisheries dur- 

 ing their spawning runs into rivers along the At- 

 lantic coast. They are sympatric over most of their 

 range and remarkably similar in external appear- 

 ance; species separation is based primarily on eye 

 size and the color of the abdominal peritoneum 

 (Scott and Grossman 1973). Except for a descrip- 

 tion of some biological characteristics of these 

 species from catches on Georges Bank (Netzel and 

 Stanek 1966), virtually nothing has been written 

 about the offshore biology or movements of these 

 "river herring" (a term used by commercial 

 fishermen for the two species combined). 



The alewife, which ranges from North Garolina 

 to the St. Lav^ence River, Ganada, spawns in 

 rivers during spring. Spawning runs occur in a 

 chronological south to north progression, from 

 March through May. The significance of specific 

 water temperatures for both upstream migration 

 and spawning has been well documented for anad- 

 romous alewife populations (Gooper 1961; Dominy 



Assistant Unit Leader, Virginia Cooperative Fishery Re- 

 search Unit, 106 Cheatham Hall, VPI & SU, Blacksburg, VA 

 24061. 



Manuscript accepted April 1981. 



FISHERY BULLETIN: VOL. 79, NO. 3, 1981. 



1971; Saila et al. 1972; Kissil 1974; Richkus 1974; 

 Tyus 1974). Adults migrate upstream and spawn 

 in ponds, lakes, or slow-flowing stretches of rivers 

 at water temperatures between 12° and 16° G 

 (Bigelow and Schroeder 1953). Available evidence 

 indicates that alewdves home to their natal rivers 

 to spawn (Belding 1921; Havey 1961; Thunberg 

 1971). The young remain in freshwater for several 

 months, migrate downstream during summer and 

 autumn, and generally spend 2 to 4 yr at sea, until 

 sexually mature. 



The behavioral response of alewives to changes 

 in water temperature has received special re- 

 search attention since the species invaded the 

 Great Lakes (Golby 1973; Otto et al. 1976). Large, 

 periodic die-offs in the Great Lakes have indicated 

 a failure of this species to adjust completely to lake 

 conditions. Hypotheses to explain these die-offs 

 have alluded to differences between the lacustrine 

 environment and the ancestral ocean, and their 

 effect on the physiology of preadults (Smith 1968; 

 Golby 1971; Stanley and Golby 1971); however, 

 specific information on the marine phase of the 

 alewife's life history is lacking. 



The blueback herring ranges from northern 

 Florida to Nova Scotia but is most abundant along 

 the middle and south Atlantic coast. Its freshwa- 



473 



