706 



Fishery Bulletin 101(3) 



At stations where replicate tows were taken, densities 

 were averaged. Ichthyoplankton samples were preserved 

 in 95% ethanol. Temperature was measured at all stations 

 with a hand-held thermometer and salinity was measured 

 with a refractometer. Size at age of larvae was estimated 

 from the equation L,, standard length = -1.31 + 1.2162 

 (L,, age in daysl (Powell et al.^). 



Because of the high coefficient of variation associ- 

 ated with ichthyoplankton samples (Cyr et al., 1992), my 

 sampling design was probably inadequate for multiway 

 statistical comparisons. Therefore, I used nonparametric 

 Kruskal-Wallis tests with o = 0.10 (Sokal and Rohlf, 1981) 

 and relied on patterns and trends to infer differences in 

 densities of spotted seatrout between stations and time 

 periods. In the period 1994-95 we tested densities among 

 nine months and 14 stations to determine trends in spatial 

 and temporal spawning habits. We also tested differences 

 between the period 1994-95 and the period 1996 to de- 

 termine interannual spatial and temporal differences or 

 similarities. Only those months (April through August) 

 that were sampled during the two periods were included. 

 During the period from 1997 through 1999 it was only 

 appropriate to determine spatial differences because we 

 sampled irregularly during this period. 



A general description of the diverse habitats in relation 

 to stations in the present study is described by Holmquist 

 et al. ( 1989, decapod and stomatopod communities ); Thayer 

 and Chester (1989, fish distribution, seagrass distribution 

 and abundance, sediment depth, and organic content); Zie- 

 man et al. ( 1989, macrophyte distribution); and Fourqurean 

 and Robblee (1999, general description of the Florida Bay 

 ecosystem). 



Results 



In 1994-95, salinities were lowest and most variable at sta- 

 tions 1-5 and 7 in the eastern part of Florida Bay (Figs. 1 

 and 2 ). Hyperhaline conditions were never observed during 

 this period. Salinities in 1996, which were recorded monthly 

 from April through September at stations where recently 

 hatched spotted seatrout were collected in 1994-95, were 

 generally euhaline and, as in 1994-95, hyperhaline con- 

 ditions were never observed. From July 1997 through 

 November 1999 at four trout monitoring stations, mean 

 salinities were similar at stations 6, 16, and 17 but were 

 most variable at station 6. Station 15 had the lowest mean 

 salinity and the greatest variation. At this station salini- 

 ties ranged from 10.0 (March 1998) to 33.0 psu (May 1999). 

 Highest salinities for all four stations were observed in 

 May 1999. Hyperhaline conditions were observed only at 

 station 6 in June 1998 and May 1999 and at station 16 in 

 May 1999 (Fig. 2). 



In general, spawning in Florida Bay occurred between 

 March and October and peaked in June, August, and Sep- 



3 Powell, A. B., R. Cheshire, E. H. Laban, J. Colvocnresses, P. 

 O'Donnell.and M. Davidian. In review. Growth, mortality and 

 hatchdate distributions of larval and juvenile spotted seatrout, 

 Cynoscion nehulosus, in Florida Bay, 26 p. 



15 

 10 



40 -1 

 35 

 S 30 



Q. 



$• 25 



c 



« on - 

 15 

 10 



~i — I — I — I — I — I — I — I — I — I — I — I — r 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 



B 



i  i i « i 



~i I I I r I I 

 5 6 9 10 11 12 13 



40 



35 



30 - 



25 - 



20 



15 



10 



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1 1 1 1 



6 15 16 17 



Station 



Figure 2 



Mean salinities SD for (A) 14 stations sampled 

 from September 1994 through August 1995, 

 (B) 7 stations sampled monthly from April 

 through September 1996, and (C) 4 stations 

 sampled from July 1997 through November 

 1999. For months that samples were taken, 

 refer to Tables 2 and 3. 



tember ( Table 2 ). Densities of spotted seatrout were signifi- 

 cantly different among months in 1994-95 (P<0.01) and 

 1996 (P=0.01). Spotted seatrout larvae were absent during 

 December, February, and April in 1994—96 (Table 2), and 

 in November 1997-99 (Table 3). Most spawning, based on 

 larval collections, occurred between 26° and 34°C (Fig. 3). 

 The coldest temperature at which larval spotted seatrout 

 were collected was 20°C in March 1998 at station 6. Spotted 

 seatrout larvae were collected mainly at salinities between 

 25 and 40 psu (Fig. 3), although larvae were collected in 

 salinities as low as 12 psu at station 15. 



