530 
Daily age and growth of larval and 
early juvenile Spanish mackerel, 
Scomberomorus maculatus, 
from the South Atlantic Bight* 
John S. Peters 
Department of Biology, College of Charleston 
66 George St., Charleston, South Carolina 29424 
E-mail address: petersj@cofc.edu 
David J. Schmidt 
Smartech 
1725 Signal Pt. Rd., Charleston, South Carolina 29412 
Abstract.-Age and growth of lar- 
val and juvenile Spanish mackerel, 
Scomberomorus maculatus, were deter- 
mined by examining increments of 
daily growth on the otoliths (lapilli) of 
specimens collected along the south- 
eastern Atlantic coast, 1983-89. Mar- 
ginal increment analysis was per- 
formed on 152 fish (7.4-97.0 mm SL) 
to validate the deposition of daily rings. 
A mean standardized marginal incre- 
ment (SMI) was calculated by compar- 
ing the width of the marginal increment 
to the adjacent increment on the lapilli 
of fish captured over a diel cycle. The 
distribution of mean SMI was uni- 
modal. A nonlinear equation was used 
to model growth (In SL - 6.2 - 55.1/ 
Age). Based on this growth equation, 
predicted absolute growth rates for the 
first 23 days of life were approximately 
1.9 mm/day, followed by a surge of rapid 
growth approaching 5.0 mm/day over 
the next 17 days. Absolute growth rates 
subsequent to 40 days of age were 2.1 
mm/day. 
Manuscript accepted 22 November 1996 
Fishery Bulletin: 530-539 (1997). 
The Spanish mackerel, Scombero- 
morus maculatus (Mitchill), is an 
inhabitant of the Gulf of Mexico and 
the Atlantic coast of the United 
States. During winter months, 
Spanish mackerel are concentrated 
in waters off southern Florida. In 
late spring and summer, however, 
they are widely distributed along the 
Atlantic coast to the Gulf of Maine 
(Klima, 1959; MacEachran et al., 
1980; Finucane and Collins, 1986). 
Most life history studies on Span- 
ish mackerel have focused on adults 
from southern Florida and the Gulf 
of Mexico (Klima, 1959; Powell, 
1975; Finucane and Collins, 1986; 
Fable et al., 1987; Schmidt et al., 
1993 ). Except for work by DeVries et 
al. (1990) on growth rates of larval 
and early juvenile Spanish and king 
mackerel (2.8-22.0 mm SL), very 
little has been done on the early life 
history of S. maculatus, particularly 
in the South Atlantic Bight (SAB). 
Daily growth increments on oto- 
liths of juvenile scombrids (skipjack, 
Euthynnus pelamis, and yellowfin 
tuna, Thunnus albacares, bluefin 
tuna, T. thynnus, black skipjack, 
Euthynnus lineatus, Atlantic mack- 
erel, Scomber scombrus, and south- 
ern bluefin tuna, Thunnus maccoyii) 
have been tentatively validated 
(Uchiyama and Struhsaker, 1981; 
Radtke, 1983; Wild and Foreman, 
1980; Brothers et al., 1983; D’Amours 
et al., 1990; Jenkins and Davis, 1990; 
Wexler, 1993). However, no published 
study has been directed at the vali- 
dation of daily growth increments on 
the otoliths of Spanish mackerel. 
The validation of the consistent 
periodic deposition of growth rings 
generally requires that fishes be 
held in captivity under conditions 
that approximate the natural envi- 
ronment. However, Spanish mack- 
erel larvae and juveniles are diffi- 
cult to rear in the laboratory. An- 
other method that has moderate 
reliability involves demonstrating 
that initiation of increment forma- 
tion is synchronous throughout the 
population (Tanaka et al., 1981; 
Geffen, 1987; Jenkins and Davis, 
1990). If fishes deposit increments 
in response to external environmen- 
tal cues of diel periodicity, or an en- 
dogenous daily rhythm, then indi- 
viduals experiencing the same envi- 
ronmental conditions (light, tempera- 
ture, feeding activity) would be ex- 
pected to initiate increment deposi- 
* Contribution 377 from the South Carolina 
Department of Natural Resources, Charles- 
ton, South Carolina 29422 and contribu- 
tion 135 from the University of Charles- 
ton’s Grice Marine Laboratory, Charleston, 
South Carolina 29412. 
