STANDARD and CHITTENDEN: REPRODUCTION. MOVEMENT, AND POPULATION OF BANDED DRUM 



mm in July for the abundant fall 1979-spawned 

 group as it approached age II in the northwestern 

 Gulf. We have assumed fish in the north central 

 Gulf were produced in the major fall-spawning 

 period, not the minor spring one, and that differ- 

 ences in size compositions do not reflect only possi- 

 ble intra-Gulf differences and greater size at age 

 in the north central Gulf. Comprehensive collec- 

 tions in that area are needed to resolve the latter 

 assumption. 



Apparent growth of L. fasciatus in the north- 

 western Gulf was similar between fall-spawned 

 groups, mean sizes being 130-150 mm at age I and 

 155-180 mm at or approaching age II. Observed 

 mean sizes and ranges at age I, based on pooled 

 data from September and October (Table 3), were 

 134 mm (120-143) for fall 1976 fish, 148 mm (145- 

 152) for fall 1977 fish, 145 mm (127-164) for fall 



1978 fish, and 147 mm (118-168) for fall 1979 fish. 

 These sizes at age I agree with quadratic regres- 

 sion predictions of 142 and 134 mm (Fig. 7) and von 

 Bertalanffy model predictions of 137 and 131 mm 

 for fall 1978 and fall 1979 fish, respectively. Ob- 

 served mean size and ranges at or approaching age 

 II (Table 3) was 159 mm (150-172) in July 1980 for 

 fall 1978 fish, 159 mm ( 143-176 1 in July 1981 for fall 



1979 fish, and 164 mm (156-177) in August- 

 September 1980 for fall 1978 fish. These values are 

 only slightly larger than a quadratic regression 

 prediction of 155 mm at age II for fall 1978 fish 

 (Fig. 7A), and are the same as or a little smaller 

 than von Bertalanffy model predictions of 164 and 

 181 mm at age II for fall 1979 and fall 1978 fish, 

 respectively. 



Fitted von Bertalanffy equations based on 

 hatching dates of 15 October for fall 1978 fish and 

 17 September for fall 1979 fish were 



Fall 1978: I, = 201 (1 - e 

 Fall 1979: l t = 176 (1 - e 



-0.003162(/-1.574> 



-0.003670U + 4.696) 



young, or a pattern of incomplete recruitment in 

 which smaller, younger fish gradually recruit to 

 join early recruits that are slightly larger and 

 older. Growth increments for age fish were 

 greatest in March-June, peaking in early June 

 (26.7 and 32.1 mm/30 d). Growth increments de- 

 creased as maturation occurred from July through 

 September, became small after spawning in 

 October-January, and increased slightly in 

 June-August as the fish approached age II. 



Apparent sizes of L. fasciatus at or approaching 

 age I in the northwestern Gulf reached a plateau 

 in August-September and for many months later. 

 Mean sizes of fish at or approaching age I re- 

 mained constant then, and 99% confidence limits 

 for observations generally remained uniform at 

 130-160 mm (Table 3, Fig. 6). This pattern suggests 

 an exodus of larger individuals and/or cessation of 

 growth coincident with gonad maturation (see sec- 

 tion on Maturation and Spawning Periodicity). 



Maximum Size, Life Span, 

 and Mortality 



The maximum size L. fasciatus reach in the 

 northwestern Gulf is about 180 mm, but more typ- 

 ically individuals reach only 160-165 mm. The 

 largest of the 13,676 fish we collected there was 182 

 mm; 99% were <161 mm and 99.5% were <164 mm 

 (Fig. 13), these sizes being estimates of l L . 



Typical maximum life span of L. fasciatus ap- 

 pears to be only 1-2 yr in the northwestern Gulf. 

 A value of ti, = 1-2 yr is reasonable for that area 

 because 1) fish average 155-180 mm at or approach- 

 ing age II and 130-150 mm at age I with the upper 

 99% confidence limits for observations at age I 

 generally being 160-165 mm (Table 3 ), 2 ) li values 

 of 161 and 164 mm predict ti values of 1.3-2.0 yr 

 (Table 6), 3) the largest specimen was 20 mo old 

 when collected in May 1980, and 4) L. fasciatus 

 disappeared off Texas at 15-23 mo of age (Table 5), 



where /, = length in millimeters, and t = time in 

 days. Annual K values were 1.15 and 1.34, respec- 

 tively. Respective annual ^ values (0.00431 and 

 -0.01287) were small which may reflect our forc- 

 ing the curve through the origin. 



Apparent growth of fall-spawned L. fasciatus 

 follows an S-shaped intrayear pattern and is 

 greatest in the spring and summer. Observed 

 mean sizes at age showed a clearly S-shaped pat- 

 tern (Fig. 7). Adjusted growth increments were 

 small early in life (Fig. 12) and may reflect cool- 

 water temperatures then, gear selection for larger 



TABLE 6. — Values of fj, (yr) for Larimus fasciatus cal- 

 culated from li i mm TL) using quadratic and von Ber- 

 talanffy equations scaled to hatching dates of 15 October 

 for fall 1978 and 17 September for fall 1979 fish. The 

 apex of the parabola for fall 1979 fish was 157 mm so 

 that ti. values could not be calculated for that cohort. 



355 



