900 
Abstract .—Late larvae (15-30 mm 
TL) of the Japanese sardine, Sardinops 
melanostictus, are commercially ex- 
ploited in fishing grounds along the 
Pacific coast of western and central 
Japan. Concentrated shoals of late lar- 
vae in the shallow (15-30 m deep) 
coastal (4-6 miles from the coast) fish- 
ing grounds enable fishermen to catch 
as much as several hundred metric tons 
(t) (several billion larvae in number) per 
month. Growth trajectories of sardine 
larvae caught in the fishing ground off 
Atsumi Peninsula in central Japan 
were individually backcalculated by 
using the biological intercept method 
based on the allometric relationship 
between otolith radius and fish length. 
Growth rates for larvae up to 13-21 d 
were high, ranging from 0.79 to 0.85 
mm/d, but declined after reaching size 
of immigration ( 13-19 mm TL) from the 
offshore waters to the coastal fishing 
grounds. The decline of growth rate in 
the late larval stage seemed to be re- 
lated to the concentration of late lar- 
vae in the fishing grounds, the result of 
onshore intrusions of offshore Kuroshio 
waters. Total lengths at age 20 d were 
significantly smaller in 1990 (total 
catch of larval sardine was 720 t) than 
in 1991 (total catch 300 t) in spite of a 
higher sea surface temperature in 1990 
in the coastal habitat. This may have 
resulted from a larger population of late 
larvae on the fishing ground in 1990 
than in 1991. 
Manuscript accepted 6 February 1998. 
Fish. Bull. 96:900-907 (1998). 
Growth trajectory of the 
larval Japanese sardine, 
Sardinops melanostictus , 
transported into the Pacific 
coastal waters off central Japan 
Yoshiro Watanabe 
Ocean Research Institute, University of Tokyo 
1- 15-1 Minamidai, Nakano-ku, Tokyo 164, Japan 
E-mail address : ywatanab@ori.u-tokyo.ac.jp 
Motohiko Nakamura 
Marine Resources Research Center, Aichi Fisheries Research Institute 
2- 1 Toyoura, Toyohama, Minami-Chita, Chita-gun, Aichi 470-34, Japan 
Late larvae of the Japanese sardine 
Sardinops melanostictus and the 
Japanese anchovy, Engraulis japon- 
icus, termed shirasu in Japan, are 
fished by boat seiners in waters 
along the Pacific coast of western 
and central Japan. The coastal wa- 
ters (4-6 miles from the coast) off 
Atsumi Peninsula (Fig. 1) are one 
of the major fishing grounds for 
sh irasu. Depth of the sea bed of the 
fishing grounds is about 20 m, with 
a range from 15 to 30 m. The 
shirasu fishery for sardine larvae 
begins in March and continues to 
December, with the major effort 
shifting to anchovy in early sum- 
mer. The annual catch of sardine 
larvae in the waters ranged from 
700 to 2000 metric tons (t), 7-20 
billion larvae, 1980-88. However, 
between 1989 and 1991 the catch 
declined to 300-700 t (Fig. 2). Since 
1992, catches have been as low as 
several tens of tons, with an excep- 
tion of about 400 t in 1993. 
Growth rates of fish larvae affect 
their survival and recruitment to 
the adult population (Anderson, 
1988). From life-stage table analy- 
ses, growth rate has been shown to 
be an important determinant of 
year-class strength by delimiting 
the duration of a particular life 
stage with high instantaneous mor- 
tality (Lo et al., 1995; Butler et al., 
1996). Watanabe et al. (1995) 
showed that recruitment failures of 
the Japanese sardine in 1988-91 
could not be explained by mass mor- 
tality at the first feeding stage. Cu- 
mulative mortality after the first 
feeding stage of the sardine, which 
may be a function of growth rate, is 
likely to have determined the re- 
cruitment in these years. Meekan 
and Fortier (1996) examined early 
life growth and survival of the At- 
lantic cod, Gadus morhua, and 
showed that fast-growing pelagic 
larvae survived better through the 
larval stage and dominated in the 
cohort of demersal juveniles. Cam- 
pana (1996) found a positive corre- 
lation between growth rates in ju- 
venile Atlantic cod and subsequent 
year-class strengths, which enabled 
him to predict recruitment from the 
juvenile growth rates. 
Available population size of late 
larval sardine in the shirasu fish- 
ing grounds could be affected by lar- 
val growth. The size range of lar- 
vae caught in the shirasu fishery is 
usually from 15 to 30 mm TL. Be- 
cause the duration time of this size 
