SPAWNING BIOMASS AND EARLY LIFE OF NORTHERN ANCHOVY, 



ENGRAULIS MORDAX, IN THE NORTHERN SUBPOPULATION 



OFF OREGON AND WASHINGTON 



Sally L. Richardson ^ 



ABSTRACT 



A major spavming center for the northern subpopulation of northern anchovy, Engraulis mordax. is 

 documented off the Oregon-Washington coast beyond the contmental shelf, based on collections of 

 planktonic eggs in July 1975 and July 1976. Biomass estimates of northern anchovy in this spawning 

 concentration ranged from 262,506 to 769,511 metric tons in 1975 and 144,654 to 1,005,263 metric tons 

 in 1976, based on egg and larva surveys. Spawning biomass was estimated to be 800,000 metric tons in 

 1977, based on an acoustic survey of adults. The most probable biomass may be more than 100,000 but 

 less than 1,000,000 metric tons. Potential yield estimates ranged from 86,792 to 633,316 metric tons, 

 but realizable yields may be considerably lower if management strategies applied to northern anchovy 

 in the central subpopulation are implemented for the northern subpopulation. 



Spawning appears to be associated with waters of the Columbia River plume which may provide 

 favorable conditions, in terms of stability and productivity for survival of first feeding northern 

 anchovy larvae. Evidence of larval transport south away from the spawning center leads to questions 

 about return mechanisms to explain the occurrence of juveniles in Oregon bays and rivers later in the 

 season. Additional spawning centers within the range of the northern subpopulation have not been 

 documented although some evidence from the literature indicates another spawning center may occur 

 in the Strait of Georgia, British Columbia, around the Fraser River plume. 



Conditions related to spawning differ between the northern and central subpopulations. Off Oregon, 

 spawning occurs from mid- June to mid-August, when current flow to the south is at a maximum, water 

 temperatures are reaching maximum levels for the year, coastal upwelling is at a maximum, and day 

 length is at or near maximum duration. Off California, peak spawning occurs from January through 

 April when southward current flow is minimal, water temperatures are reaching minimal levels for the 

 year, upwelling is minimal, and day length is at minimum duration. These factors are indicative of 

 some degree of reproductive isolation as well as differing reproductive strategies between the two 

 subpopulations. 



The northern anchovy, Engraulis mordax Girard, 

 is an abundant pelagic schooling fish that occurs 

 along the west coast of North America from Cape 

 San Lucas, Baja California, to the Queen Char- 

 lotte Islands, British Columbia (Miller and Lea 

 1972; Hart 1973). It is the object of an expanding 

 fishery off central and southern California and 

 Baja California where about 204,000 metric tons 

 (t) were harvested in 1975, mainly for fish meal 

 (Pacific Fishery Management Council ). In the 

 northern part of its range it is utilized only to a 

 small degree as bait by local fishermen although 

 its potential as a harvestable resource has been 

 suggested (Pruter 1966, 1972). Reports of dense 

 schools off the Oregon and Washington coasts in- 



'School of Oceanography, Oregon State University, Corvallis, 

 Oreg.; present address: Gulf Coast Research Laboratory, East 

 Beach Drive, Ocean Springs, MS 39564. 



^Pacific Fishery Management Council. 1978. Northern an- 

 chovy fishery management plan. U.S. Dep. Commer, NOAA 

 Federal Register 43(141) Book 2:31651-31783. 



Manuscript accepted March 1980. 

 FISHERY BULLETLN: VOL. 78, NO. 4, 1981. 



dicate northern anchovy biomass may be substan- 

 tial (Pruter 1966, 1972). Estimates of an annual 

 consumption of 28,000 t of northern anchovy by 

 four species of marine birds off the Oregon coast 

 (Wiens and Scott 1975) further indicates sizeable 

 biomass. 



In the absence of a fishery, biomass estimates 

 are unavailable for northern anchovy north of 

 California. We know that in the 1940's northern 

 anchovy in ocean waters adjacent to the Columbia 

 River supported a live bait fishery for albacore 

 tuna (Pruter 1966, 1972). Reported commercial 

 landings of northern anchovy in Washington in 

 1947-49 ranged from 20 to 182 1 annually and were 

 28 and 76 t in Oregon in 1948 and 1953 (Pruter 

 1966). A small purse seine fishery for canning once 

 existed around southern British Columbia where 

 harvests ranged from 64 to 6,201 t annually be- 

 tween 1939 and 1947 (Roach and Harrison 1948; 

 Pike 1951). 



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