Abstract. -The seasonal distri- 

 bution and relative abundance of 

 river herring ^iosa pseudoharengiis 

 and A. aestivalis off Nova Scotia is 

 examined using Canadian Depart- 

 ment of Fisheries and Oceans data 

 from bottom-trawl surveys (1970-89) 

 and the International Observer Pro- 

 gram (1980-89). River herring oc- 

 curred throughout the year in re- 

 gions characterized by strong tidal 

 mixing and upwelling in the Bay of 

 Fundy and off southwestern Nova 

 Scotia. During spring, river herring 

 were most abundant in the warmer, 

 deeper waters of the central Scotian 

 Shelf, particularly between Emerald 

 and Western Banks, and in areas of 

 warm slope water intrusion along 

 the Scotian Slope, the western and 

 southern edges of Georges Bank, 

 and in the eastern Gulf of Maine-Bay 

 of Fundy. Most catches occurred 

 at bottom temperatures of 7-1 1°C 

 offshore at mid-depths in spring 

 (101-183m), in shallower nearshore 

 waters in summer (46-82 m) and 

 in deeper offshore waters in fall 

 (1 19-192 m). Diel variation in catch 

 occurred during summer and fall 

 but not during spring, with largest 

 catches during daylight. Seasonal 

 distribution patterns of small (< 19 

 cmFL) and large (>19cmFL) river 

 herring overlapped geographically. 

 Small fish preferred shallow regions 

 (<93 m) during spring and fall, while 

 large fish occurred in deeper areas 

 (>93 m) during all seasons. The 

 temporal and spatial distribution of 

 river herring off the coast of Nova 

 Scotia is hkely influenced by zoo- 

 plankton concentrations and occur- 

 rence of bottom temperatures >5°C. 

 The pattern of seasonal movement is 

 generally inshore and northward 

 during spring, and offshore and 

 southward in the fall. 



Seasonal distribution of river 

 Inerring Alosa pseudoharengus 

 and A. aestivalis off the Atlantic 

 coast of IMova Scotia 



Heath H. Stone 

 Brian M. Jessop 



Department of Fisheries and Oceans, Biological Science Branch 

 P.O. Box 550, Halifax, Nova Scotia B3J 2S7, Canada 



Manuscript accepted 6 March 1992. 

 Fishery Bulletin, U.S. 90:376-389 (1992). 



River herring (a collective term for 

 the alewife Alosa pseudoharengus 

 and the blueback herring A. aesti- 

 valis) are anadromous clupeids native 

 to the Atlantic coast of North Ameri- 

 ca. These closely-related species are 

 remarkably similar in morphology 

 and life history and differ only slight- 

 ly in terms of meristics, morphomet- 

 ries, growth parameters and time of 

 spawning (Bigelow and Schroeder 

 1953, Leim and Scott 1966, Messieh 

 1977, Loesch 1987). Alewives and 

 blueback herring are sympatric; ale- 

 wife range from Newrfoundland to 

 North Carolina, and blueback her- 

 ring from the Gulf of St. Lawrence 

 to Florida (Bigelow and Schroeder 

 1953). They are fished commercially 

 in the Maritime provinces of Canada 

 and Atlantic coastal United States 

 during their spring spawning migra- 

 tions and are often marketed togeth- 

 er as alewife, gaspereau, or river her- 

 ring, depending on local convention. 

 Both species often co-occur in 

 freshwater (Loesch et al. 1982, Jes- 

 sop and Anderson 1989), estuarine 

 (Stone and Daborn 1987), and marine 

 (Neves 1981) habitats. While the 

 freshwater life histories of alewives 

 and blueback herring have been well 

 documented (reviewed by Loesch 

 1987), less information is available 

 on their distribution and movements 

 at sea, particularly in Canadian coast- 

 al areas. Off the Atlantic coast of 

 Nova Scotia, bottom trawls have 

 caught river herring on the western 



Scotian Shelf, with alewives collected 

 during spring and fall (Vladykov 

 1936, Neves 1981, Vinogradov 1984) 

 and blueback herring in spring and 

 summer (Netzel and Stanek 1966, 

 Neves 1981). In the inner Bay of 

 Fundy, river herring aggregate dur- 

 ing summer in the turbid estuarine 

 waters of Minas Basin (Rulifson 

 1984, Stone and Daborn 1987) and 

 Cumberland Basin (Dadswell et al. 

 1984). In the outer Bay of Fundy, 

 alewives and blueback herring have 

 been captured during summer and 

 autumn in herring weirs, purse 

 seines (Jessop 1986), and during 

 bottom-trawl surveys (Neves 1981). 

 Neves (1981) examined the marine 

 distribution and seasonal movements 

 of river herring along the continen- 

 tal shelf from Cape Hatteras, North 

 Carolina, to southwestern Nova 

 Scotia. In this paper, we describe the 

 seasonal marine distribution and 

 relative abundance of river herring 

 off Nova Scotia based on 20 years of 

 combined alewife and blueback 

 herring catch data from Canadian 

 research vessel surveys, thereby ex- 

 tending northward the analysis by 

 Neves (1981) of their distribution off 

 the Atlantic coast of the United 

 States. Offshore distributions are in- 

 terpreted in relation to water depth 

 and temperature within the survey 

 area. 



Although marine exploitation of 

 alewives and blueback herring in 

 the Maritime provinces by incidental 



376 



