WWELLINQ AND THE PRODUCTION OF FISH
273
wards was only just detectable. Off Oregon and Washington, the
upwelling occurs in July and August and it goes on until the winds veer
westerly when the Aleutian lows intensify across the North Pacific
(Smith et al., 1966). The seasonal shift to the north is shown most
clearly in the charts of 13-year mean temperatures by months (Lynn,
1967).
In September 1952, a chart of upwelling in California was constructed in units of ascending velocity (ftjmonth) (California Department of Fish and Game, 1953). Upwelling extended from Monterey,
just south of San Francisco, to Ensenada, in Baja California, and a
patch occurred off the Cedros Islands north of Punta San Eugenio and
off the point itself. Off southern California it was concentratted south of
Monterey, south of Point Conception and off Sail Diego ; in these areas
and off Punta San Eugenio, the ascending velocity was as high as
200 ftlmonth. There are long-term changes in the patterns of upwelling,
as might be expected from the changes in wind speed and direction over
long time periods ; before 1949, the upwelling may have been limited to
the area between Cape Blanco in southern Oregon and Cape Mendocino
and south of Monterey. After 1949, the area extended additionally to
Punta San Eugenio, as if the wind had veered a point or so into the
WNW.
The biological system has been investigated mainly in the form of
extensive egg and larval surveys (Ahlstrom, 1966) between Cape San
Lucas, the most southerly point of Baja California, and just north of
Cape Mendocino. The distributions of sardine, anchovy, jack mackerel
and hake off this coast are well known. The sardine spawns inshore in
spring, mainly in the upwelled water ; indeed, since the stock has become reduced, it has concentrated in spawning off Cedros Island and
Punta San Eugenio. The anchovy has replaced the sardine since 1951
(Ahlstrom, 1966, 1967) and the eggs are found inshore off southern
California and Baja California in all the upwelling areas. The jack
mackerel spawning area lies offshore (Blunt, 1969), as if excluded from
the points of upwelling, and the hake spawning area (Alverson and
Larkins, 1969) spreads over roughly the same region as the sardinej
anchovy area. The sardines spawn in late winter and early spring and
the hake spawn in March ; the anchovy spawns at about the same time
off Baja California, but off southern California it also spawns in the
early summer.
Alverson and Larkins (1969) have constructed a migration circuit
for the Pacific hake. From its late winter spawning ground off California it moves north and appears off Oregon and Washington in June
and July. In summer the fish live at about 100 m or less and in winter
273
wards was only just detectable. Off Oregon and Washington, the
upwelling occurs in July and August and it goes on until the winds veer
westerly when the Aleutian lows intensify across the North Pacific
(Smith et al., 1966). The seasonal shift to the north is shown most
clearly in the charts of 13-year mean temperatures by months (Lynn,
1967).
In September 1952, a chart of upwelling in California was constructed in units of ascending velocity (ftjmonth) (California Department of Fish and Game, 1953). Upwelling extended from Monterey,
just south of San Francisco, to Ensenada, in Baja California, and a
patch occurred off the Cedros Islands north of Punta San Eugenio and
off the point itself. Off southern California it was concentratted south of
Monterey, south of Point Conception and off Sail Diego ; in these areas
and off Punta San Eugenio, the ascending velocity was as high as
200 ftlmonth. There are long-term changes in the patterns of upwelling,
as might be expected from the changes in wind speed and direction over
long time periods ; before 1949, the upwelling may have been limited to
the area between Cape Blanco in southern Oregon and Cape Mendocino
and south of Monterey. After 1949, the area extended additionally to
Punta San Eugenio, as if the wind had veered a point or so into the
WNW.
The biological system has been investigated mainly in the form of
extensive egg and larval surveys (Ahlstrom, 1966) between Cape San
Lucas, the most southerly point of Baja California, and just north of
Cape Mendocino. The distributions of sardine, anchovy, jack mackerel
and hake off this coast are well known. The sardine spawns inshore in
spring, mainly in the upwelled water ; indeed, since the stock has become reduced, it has concentrated in spawning off Cedros Island and
Punta San Eugenio. The anchovy has replaced the sardine since 1951
(Ahlstrom, 1966, 1967) and the eggs are found inshore off southern
California and Baja California in all the upwelling areas. The jack
mackerel spawning area lies offshore (Blunt, 1969), as if excluded from
the points of upwelling, and the hake spawning area (Alverson and
Larkins, 1969) spreads over roughly the same region as the sardinej
anchovy area. The sardines spawn in late winter and early spring and
the hake spawn in March ; the anchovy spawns at about the same time
off Baja California, but off southern California it also spawns in the
early summer.
Alverson and Larkins (1969) have constructed a migration circuit
for the Pacific hake. From its late winter spawning ground off California it moves north and appears off Oregon and Washington in June
and July. In summer the fish live at about 100 m or less and in winter