FISHERY BULLETIN: VOL. 73, NO. 2 



Table 2.-Suinmary of biomass and production data by sampling data averaged over all size classes. 



sampling period, the mean numbers, live length 

 (or volume for Mnemiopsis), ash-free dry w^eight 

 per organism, and ash-free dry v^^eight per size 

 class are tabulated. The mean net daily production 

 of each size class (per cubic meter) averaged over 

 the entire period using the information on daily 

 rates of growth and mortality and the average 

 duration of each size class (over the three 

 temperatures) is also provided. 



Seasonal changes in production reflected those 

 of biomass generally as indicated in the produc- 

 tion/biomass ratios (Table 2), which varied 

 between 0.20 and 0.41 (mean, 0.31) for Sagitta and 

 0.059 and 0.20 (mean, 0.12) for Mnemiopsis. The 

 ratios were highest in Sagitta in the summer when 

 growth rates were maximum, but biomass and 

 production was at its lowest. In Mnemiopsis, which 

 also exhibited minimum summer biomass and 

 production levels, the ratio tended to be low rela- 

 tively, as was growth rate. This summer low point 

 of biomass and production is a confirmation of the 

 experience of some nine seasons of observation by 

 the first author and is characteristic of the 200-;u,m 

 net plankton of Card Sound and Biscayne Bay as a 

 whole (for a discussion of which, see reviews of 

 Reeve and Cosper 1973 and Reeve in press). 



Throughout the rest of the year the chaetognath 

 biomass of Card Sound and Biscayne Bay fluc- 

 tuated much less widely than that of the 



ctenophores in Biscayne Bay. The biomass of 

 Sagitta ranged (excluding July-September) 

 between 1- and 12-mg ash-free dry wt/m' in Card 

 Sound and an estimated 2- and 20-mg ash-free dry 

 weight in Biscayne Bay, whereas for ctenophores 

 the range was 0.2 to 314 mg/m\ The mean annual 

 biomass of Sagitta in Card Sound and Biscayne 

 Bay was 3.36- and 8.04-mg ash-free dry wt/m' and 

 for Mnemiopsis in Biscayne Bay was 25.2- to 42.5- 

 mg ash-free dry wt/m' (reckoning 12 mo from the 

 date of the first sample or 12 mo prior to the date of 

 the last sample). 



The range of net daily production rate in terms 

 of ash-free dry weight for Sagitta at the surface 

 from Card Sound and Mnemiopsis from Biscayne 

 Bay was 0.04 to 3.1 and < 0.01 to 27.8/m', respec- 

 tively. Table 3 contains production estimates on an 

 annual basis computed for surface and average 

 water column (for Sagitta only) as ash-free dry 

 weight and carbon per cubic meter. For 

 Mnemiopsis, carbon production is computed both 

 on the basis of the carbon content of Sagitta and 

 the experimentally determined carbon content for 

 Mnemiopsis. Daily production estimates per cubic 

 meter and per square meter are also computed in 

 terms of experimentally determined carbon con- 

 tent. As noted above, the two values in each case 

 for Mnemiopsis incorporate successive annual 

 production peaks. 



244 



