Miller et al : Distribution, abundance, and growth of Micropogonias undulatus 



103 



the mouth to upper creek gradients (see Able et al., 2000; 

 2001; Able et al.M. Thus, at each of the marshes there were 

 six trawling locations. These locations included two large 

 subtidal creeks and two smaller creeks with lower sub- 

 tidal and upper subtidal or intertidal sections in each of 

 the latter. Additional trawling locations were established 

 in the bay immediately outside the mouth of the large 

 creek at the Dennis Township, Moores Beach, Commer- 

 cial Township, and Mad Horse Creek study sites (Fig. 1). 

 The fish collected at these bay stations were used in the 

 length-frequency figures for the bay (exclusive of Novem- 

 ber when there was no trawl survey sampling in the bay) 

 and for the growth calculations, but not in the catch-per- 

 unit-of-effort (CPUE) calculations for the bay. Atlantic 

 croaker collected in each weir set and in each trawl were 

 enumerated, and up to 50 individuals per weir set and 20 

 per trawl were measured to the nearest millimeter total 

 length. Abundances (CPUE, number of fish per trawl) 

 were compared between the upper and lower bay sites in 

 Delaware Bay, among the six different marsh sites, and 

 among years, by using the nonparametric Mann-Whitney 

 f/-test, or the Kruskal-Wallis ANOVA of ranks for mul- 

 tiple comparisons, and when differences were found, the 

 Dunnis test was used (criteria for significance; P<0.05) to 

 make pair-wise comparisons. 



Physical variables were measured at the end of each 

 weir and otter trawl sample in the marshes and in Dela- 

 ware Bay (Table 1). Temperature, salinity, and dissolved 

 oxygen concentrations were measured with a hand-held 

 salinity, temperature, and oxygen meter (YSI Model 85), 

 by lowering the probe into the water and recording surface 

 values. Water transparency was measured by lowering a 

 Secchi disc into the water column until it was no longer 

 visible and recording the corresponding depth in 0.1-m 

 increments. 



Growth 



Figure 2 



Catch per unit of effort (CPUE) of larval and postlar\'al Atlantic 

 croaker (Micropogonias undulatus) collected in the ichthyoplank- 

 ton survey in September and October 1996. 



Growth rates for YOY Atlantic croaker were calculated for 

 samples collected during the late spring through fall in 

 the upper and lower regions of the bay in 1997 and 1998 

 and in the upper and lower bay marsh sites during 1997. 

 1998, and 1999. We compared growth using the progres- 

 sion of the monthly median lengths in each area by com- 

 puting the change in the median length of a cohort over a 

 time period divided by the number of days in the period. 

 This method was based on the following assumptions: 1 ) 

 no new (small) recruits join the population during the 

 calculation interval, and 2) no (large) individuals leave 

 the population over the calculation interval. To best meet 

 these assumptions, median growth rates were calculated 

 by using the monthly length data from May to July when 

 there was a minimum of movement offish between differ- 

 ent areas, and then for longer-term monthly comparisons, 

 from May to August, September, and October when fish 

 were moving out of the marshes into the bay. The smaller- 



Able, K. W., D . M. Nemerson, and T. M. Grothues. In review. 

 Evaluating salt marsh restoration in Delaware Bay: continued 

 analysis offish response at former salt hay farms. 



size cohort present in the bay in June and July 1998 and 

 in the marshes in 1999 was excluded from the growth cal- 

 culations for those years. The linearity of the progression 

 of median lengths was tested by using linear regression, 

 and the resulting lines were compared between the upper 

 and lower bay 



Results 



Distribution, abundance, and size 

 during fall ingress and settlement 



Atlantic croaker lan'ae were collected only in the late 

 summer and fall during the ichthyoplankton survey in 

 Delaware Bay in 1996 ( Figs. 2 and 3 ). A few individuals 

 were first collected in August (/z=3, CPUE=0.02 fish/tow), 

 and then large numbers of larvae were collected through 

 September («=639, CPUE=3.6) and October (n=996, 

 CPUE=9.0), but they were absent from April to July The 

 overall September-October CPUE was 9.0 fish/tow (range; 



