NOTE Lazzari et al.: Physical environment and recruitment variability of Ciupea harengus 
377 
Figure 1 
Map of the Gulf of Maine showing the spawning grounds of Atlantic herring, Ciupea 
harengus. 
as subjects for future research. Through examina- 
tion of time-series data and the use of exploratory 
correlations, contingency tables, and /-tests, a search 
was made for those environmental factors that re- 
lated positively or negatively with size estimates of 
age-2 herring populations. 
Methods 
The method of exploratory correlation (Sutcliffe et 
al., 1977; Hayman, 1978) was used to determine re- 
lationships between monthly means of environmen- 
tal factors along the Maine coast. Records were ana- 
lyzed for the larval year 1 August through 31 July 
for years 1965 through 1990 (Table 1). The herring 
recruitment index used was the virtual population 
analysis (VPA) estimation of two- 
year-olds from 1967 to 1991 in the 
coastal Atlantic stock (NEFC, ! Fig. 
2). For purposes of our analysis, we 
assumed predation to be constant 
and that spawning stock biomass 
was not a major factor affecting re- 
cruitment. Sea surface tempera- 
ture (SST) records were supplied 
by the Maine Department of Ma- 
rine Resources Laboratory, Booth- 
bay Harbor, ME. Sunshine was 
measured as percent possible sun- 
shine from observations of cloud 
cover conditions at the Portland, 
ME, airport. Long-term sunshine, 
atmospheric pressure, wind direc- 
tion, and velocity data records 
were compiled for Portland as 12 
monthly averages per year and 
archived by the National Climatic 
Data Center. 
Wind speed and direction were 
measured at the Portland airport, 
8 km inland, where an anemometer is situated 7 m 
above the ground at an elevation of 25 m. Storm fre- 
quency was also complied as days with mean winds 
in excess of 5 m/s. Daily average wind speed and di- 
rection were further analyzed for the period August- 
December when the influence of wind-driven surface 
currents on the dispersal of newly hatched herring 
larvae would be greatest. The daily resultant wind 
direction (a vector variable) was separated into one 
of four directions on the basis of compass headings 
of northeasterly (1-90°), southeasterly (91-180°), 
southwesterly (181-270°), and northwesterly (27 1— 
3 NEFC (Northeast Fisheries Center). 1991. Assessment of the 
coastal Atlantic herring stock. Thirteenth Northeast Regional 
Stock Assessment Workshop. Northeast Fish. Sci. Center, Natl. 
Mar. Fish. Serv., NOAA, 111 p. 
Table 1 
The location and origin of environmental factors tested for association with the age-2 Atlantic herring abundance estimates. ME 
DMR = Maine Department of Marine Resources; NCDC = National Climatic Data Center; NEFC = Northeast Fisheries Center. 
Environmental factor 
Location 
Years 
Source 
Sea surface temperature 
Boothbay Harbor 
1965-90 
ME DMR 
Wind speed and direction 
Portland, ME 
1965-90 
NCDC, Asheville, NC 
Storm index (no. of days > 5 m/s) 
Portland 
1965-90 
ME DMR 
Sunshine 
Portland 
1965-90 
NCDC, Asheville, NC 
Barometric pressure 
Portland 
1965-90 
NCDC, Asheville, NC 
Herring abundance estimates 
Gulf of Maine 
1967-91 
NEFC, 1991 
