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



m after November 1978 and at 55, 64, 73, 82, 86, 

 and 100 m after May 1979. Collections were made 

 during the day through September 1978; there- 

 after, a day and a night cruise usually were made 

 each month. Two 10-min tows (bottom time) were 

 made at each depth except that 1 tow was made at 

 most depths prior to October 1978, usually 8 tows 

 were made at 16 m, and usually 24 tows were made 

 at 22 m. 



All L. fasciatus were culled from the catch, mea- 

 sured to the nearest millimeter total length, fixed 

 in 10'<^ Formalin 5 , and later preserved in 70' , 

 ethanol. For the period October 1979- April 1981, if 

 available, 300 fish each month were selected for 

 intensive processing using stratified random sam- 

 pling in which a stratum included an individual 

 spawned group (Standard 1983: app. 1). The follow- 

 ing data were taken on the first 200 fish selected: 

 total length (TL), standard length (SL), girth at 

 origin of dorsal fin (G), total weight (TW>, gonad 

 weight (GW), sex, and ovary maturity stage. Only 

 sex and ovary maturity stage were recorded for the 

 remaining 100 fish. Maturity stages (Table 1) were 

 assigned to immature and female fish using a 

 slight modification of Kesteven's system (Bagenal 

 and Braum 1971). Gonadosomatic indices (GSI) 

 were calculated for individual females as GSI = 

 100 GW TW. 



Supplemental collections were made in the 

 north central Gulf from 24 October to 5 November 

 1982 aboard the FRS Oregon 11 (NMFS) using 

 standard 12.2 m (40-ft) 4-seam semiballoon 

 shrimp trawls at depths of 9-91 m between long. 

 88°00' and 89°00'W and at depths of 347-549 m 

 between long. 87°50' and 88°00'W (Rohr et al. 6 ). 

 Total length was measured on all L. fasciatus cap- 



r 'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service. NOAA. 



TABLE 1. — Description of gonad maturity stages assigned to 

 Larimus fasciatus. 



Stage and name 



Description 



1 Immature 



2 Maturing Virgin 



3 Early Developing 



4 Late Developing 



5 Gravid 



6 Ripe 



7 Spawning Spent 



8 Resting 



Gonads barely or not visible, sexes indistin- 

 guishable to the naked eye. 



Ovaries small, thin, confined to postenodorsal 

 wall of body cavity. 



Ovaries solid, opaque, occupy 30% of body 

 cavity Individual eggs not visible to naked eye. 



Ovaries occupy -30% of body cavity. Individ- 

 ual eggs opaque, distinguishable to naked 

 eye by close examination. 



Ovaries occupy -50°o of body cavity. Individ- 

 ual eggs distinct, 50% translucent. 



Ovaries completely fill body cavity, -50% of 

 the eggs translucent. 



Ovaries flaccid, remaining eggs translucent. 



Ovaries firm, occupy <30% of body cavity, 

 translucent eggs may persist. Fish large 

 enough to have spawned. 



tured to compare with size compositions from the 

 northwestern Gulf. 



Age in years was determined by length- 

 frequency analysis, e.g., the Petersen Method 

 (Lagler 1956). Spawned groups (intrayear class 

 cohorts) were specified by the season and year 

 when they hatched, e.g., fall 1980. Descriptions of 

 spawning periodicity (beginnings and ends) using 

 length frequencies assume the following size and 

 age combinations predicted from quadratic re- 

 gression of total length on age, years pooled, noted 

 below: 15 mm TL at 1 mo, 30 mm at 2 mo, and 45 

 mm at 3 mo. The same combinations were 

 predicted from regressions for individual fall- 

 spawned groups. 



Duration of the spawning period was approxi- 

 mated for fall-spawned groups following Geoghe- 

 gan and Chittenden (1982) as 



Time-specific mean size range early in life 

 Mean growth/day early in life 



Calculations were based on April-June data, the 

 first months when fall groups appeared fully re- 

 cruited. Time-specific size range was estimated for 

 each fall group as the mean of the 99 c /c confidence 

 intervals for observations in April- June (Table 2). 

 Growth per day was estimated as the mean of the 

 growth per day values between successive collec- 

 tions in the April-June period (Table 2). This pro- 

 cedure assumes large fish hatch before small ones 

 and that all grow at the same rate ( Geoghegan and 

 Chittenden 1982). The latter assumption appears 

 valid because 999? confidence intervals for obser- 

 vations (Table 3) were fairly constant within 

 cruises in the April-June period when sample 

 sizes were large. 



Hatching dates used to set time scales to calcu- 

 late growth of fall-spawned fish were determined 

 by a one-step iteration process. A hatching date of 

 1 October was assigned to start the process be- 

 cause D fish 20-40 mm TL, which we assumed were 

 1-3 mo old, first appear in November-December, 

 and 2) slopes for regressions of ovary weight on 

 total length (Fig. 2) and mean GSI (Fig. 3) were 

 greatest in September-October. Quadratic regres- 

 sions of total length on age in days were then used 

 as a simple model to estimate initial .x- intercepts 

 for each fall-spawned group. Final hatching dates 



6 Rohr. B. A.. A. J.. Kemmerer, and W. H. Fox. Jr. 1983. 

 FRS Oregon II Cruise 130. 10-12-11 24 82. Cruise Rep.. 22 

 p. Southeast Fisheries Center Pascagoula Facility, National 

 Marine Fisheries Service, NOAA. P.O. Drawer 1207, Pascagoula, 

 MS 39567-0112. 



339 



