FISHERY BULLETIN: VOL. 79, NO. 3 



comparable with those on other anadromous 

 species (Merriman 1941; Raney et al. 1954; Talbot 

 and Sykes 1958; Chapoton and Sykes 1961; Leggett 

 and Whitney 1972). 



If the water temperature regime recorded for 

 oceanic occurrence of alewives and blueback her- 

 ring ( Figure 3) applies to all stocks of these species 

 at sea, the migratory route of blueback herring 

 populations returning to South Atlantic rivers 

 would be similar to that proposed for American 

 shad by Neves and Despres (1979). Prespawning 

 adults returning to coastal waters from the ocean 

 would encounter a thermal barrier south of Cape 

 Hatteras, where offshore temperatures remain 

 above 17.5° C throughout the year. Migration to- 

 ward shore north of Cape Hatteras and then south 

 along the coast would appear to be essential for 

 successful homing to South Atlantic rivers. 



A determination of oceanic location and migra- 

 tory routes of river herring stocks has particular 

 relevance to the commercial fishery, centered 

 primarily in Virginia and North Carolina. Large 

 catches of river herring were taken offshore by 

 foreign fishing vessels in ICNAF Subarea 6 during 

 the mid-1960's, and by 1969 foreign catches ex- 

 ceeded domestic catches (McHugh and Ginter 

 1978). The increase in high-seas catches, consist- 

 ing of juveniles and adults, was accompanied by a 

 marked decrease in inshore landings. This foreign 

 fishing pressure, added to that of the domestic 

 fishery, resulted in a drastic reduction of total an- 

 nual catches (Table 4). Street and Davis^ pos- 

 tulated that this decline reflected a reduction in 

 stock size due to excessive harvest. The United 

 States obtained certain limitations on foreign 



^Street, M. W, andJ. Davis. 1976. Notes on the river her- 

 ring fishery of SA6. Int. Comm. Northwest Atl. Fish. Annu. 

 Meet. 1976, Res. Doc. 76/VI/61, Serial No. 3848, 7 p. 



Table 4. — Annual catches (metric tons round, fresh) of alewives 

 and blueback herring (species combined) by domestic and 

 foreign fisheries in three ICNAF subareas, 1966-78. 



catches of river herring through bilateral negotia- 

 tions during the mid-1970's, and after the im- 

 plementation of the Fishery Conservation and 

 Management Act of 1976 (PL 94-265), offshore 

 catches of river herring by foreign vessels were 

 virtually eliminated. Johnson et al.^ reported that 

 Virginia landings of river herring in 1978 in- 

 creased 53% compared with those in 1977, but did 

 not attribute this increase to good recruitment. 

 River herring catches in North Carolina have con- 

 tinued to decline, and water quality degradation 

 in several spawning areas may be creating addi- 

 tional problems (Street^). Future monitoring of 

 stock abundance by coastal states should help re- 

 solve the question of whether stocks were seri- 

 ously reduced by offshore fishing. 



Depth Distribution 



Frequency of alewife and blueback herring 

 catches within the four depth strata indicated that 

 these species occur primarily at water depths <110 

 m at sea. Both species are size-selective zooplank- 

 ton feeders (Bigelow and Schroeder 1953; Hilde- 

 brand 1963; Brooks and Dodson 1965). My exami- 

 nation of the stomachs of 100 alewives and 75 

 blueback herring, collected in April 1978 during 

 the spring survey, revealed calanoid copepods, 

 mysids, and other zooplankters in that order of 

 frequency and abundance in both species. The oc- 

 currence of major zooplankton concentrations in 

 the Gulf of Maine at depths <100 m (Bigelow 1926; 

 Whiteley 1948) may therefore influence the depth 

 distribution of river herring. 



The numerous catches of river herring in the 

 northwestern Gulf of Maine during autumn were 

 centered at about lat. 44° N, long. 68° W. Mean 

 depth at these stations was 112 m (range, 64-179 

 m), and mean bottom temperature was 9.5° C 

 (range, 8.0°-13.4° C). This apparent concentration 

 of river herring is noteworthy, particularly since 

 studies on zooplankton availability in this region 

 are contradictory. From late summer to December, 

 zooplankton is most abundant in the northern 

 Gulf of Maine (Cohen^); however, Sherman (1970) 



'Johnson, H. B., D. W. Crocker, B. F Holland, Jr , J. W. Gilliken, 

 D. L. Taylor, and M. W. Street. 1978. Biology and manage- 

 ment of mid-Atlantic anadromous fishes under extended juris- 

 diction. Annu. Rep. Anadromous Fish Proj. 1978, N.C.-Va. 

 AFCS 9-2, 175 p. 



^M. W. Street, N.C. Div. Mar Fish. Morehead City, N.C. 28556, 

 pers. commun. June 1980. 



^Cohen, E. B. 1975. An overview of the plankton com- 

 munities of the Gulf of Maine. Int. Comm. Northwest Atl. Fish. 

 Annu. Meet. 1975, Res. Doc. No. 106, Ser No. 3599, 16 p. 



482 



