FISHERY BULLETIN: VOL. 80, NO. 1 



nary values to much greater, we determined the 

 best L x that resulted in the straightest line. The 

 growth coefficient (K) was the slope of this line 

 and was used to solve for t : 



to = 



y - intercept of natural log line - log P L 3 



K 



We checked the U value to see if it was biased 

 toward younger or older fish by using the equa- 

 tion to = t(l/K) In (1 - h/LJ for separate ages I- 

 IX (Jones 1976). 



Mortality Estimates 



We calculated annual total mortality estimates 

 by analyzing catch curves (Beverton and Holt 

 1957) based on fully recruited age fish and older. 

 If the log, of the age frequency in the catch is 

 plotted on age, the slope of the linear descending 

 right limb of the curve is equal to the mean in- 

 stantaneous total mortality (Z). To calculate 

 mortality rates, we first needed to assign ages to 

 the 1,100 or so unaged fish. We grouped fish of 

 known age by 25 mm length intervals, calculated 

 the percentage of fish of each observed age in 

 each group, and used these percentages to esti- 

 mate the number of fish of each age for the un- 

 aged group (Ricker 1975). 



Length- Weight and Fork Length- 

 Total Length Relationships 



To calculate length-weight and length conver- 

 sion relationships fish lengths were subsampled 

 to provide a fairly equal distribution throughout 

 the size range of fish examined during this study. 

 The length-weight relationship was expressed 

 exponentially, whereas the fork length-total 

 length equation was expressed as a simple linear 

 regression. 



Spawning 



Gonads were examined macroscopically by 

 season to determine the approximate time of 

 spawning. Observations on the development of 

 testes were used collaboratively with measure- 

 ments recorded from ovaries. Ovaries were 

 weighed to calculate a seasonal gonad index, or 

 the percentage of gonad weight to fish weight. 



RESULTS 



Distribution and Relative Abundance 



Tomtates were collected throughout the South 

 Atlantic Bight (Figs. 1-4). Although most of the 

 continental shelf is sandy "open-shelf habitat" 

 (Struhsaker 1969), the greatest catches of tom- 

 tates were directly associated with the irregu- 

 larly distributed sponge-coral ("live bottom") 

 habitats (as defined by Wenner et al. 1979a). In- 

 dices of relative abundance over live-bottom 

 areas were significantly larger (P<0.01) than 

 abundance indices from sandy-bottom catches in 

 all seasons and years, except during the cold 

 winter of 1977 (Table 2). Although tomtates 

 occurred in 30-70% of the collections from the 

 sponge-coral habitat, 79.6% of the total number 

 caught during seven cruises, excluding the cold 

 winter of 1977, were at sponge-coral stations 

 (Table 3). 



During all seasons, catches of tomtates over 

 sand were infrequent, but occasionally large 

 (Wenner et al. 1979a, b, c, d). Occurrence of 

 tomtates in both sandy-bottom and live-bottom 

 habitats increased the difficulty in biomass esti- 

 mations. Information from catches over the 

 sponge-coral habitat with the 30-min tows was 

 expanded to preliminary estimates of biomass 

 (Tables 4, 5), although the catch represented a 

 mixed habitat collection of unknown propor- 

 tions. Standing crop estimates of tomtates from 

 the region between Cape Fear and Cape Canav- 

 eral ranged from 1,730 t (minimum catch, sum- 

 mer 1974) to 12,878 t (maximum catch, winter 

 1976). Although biomass estimates were calcu- 

 lated separately for each depth zone and stand- 

 ing crop estimates were calculated separately 

 for catches from live-bottom and sandy-bottom 

 habitats (Table 6), all estimates represent mini- 

 mal values because fish availability and vulner- 

 ability to the trawl were not considered. 



Tomtates, both juvenile (<137 mm TL) and 

 adult, were more abundant in catches in the 

 northern part of the South Atlantic Bight than in 

 catches in the south. During all seasons sampled, 

 between 1973 and 1977, the catch north of lat. 

 32°32'N, an arbitrary shelf division, was be- 

 tween 59 and 89% of the total catch. The one ex- 

 ception occurred during the cold winter of 1977, 

 when 98% of the total catch (3,192 fish) was made 

 south of lat. 32°30'N at a single station. 



