104 



Fishery Bulletin 101(1) 



10 



I 

 I 150 



August 



n = 3 



c: Upper bay 



 Lower bay 



 > f 



September 

 n = 494 



October 

 n = 905 



10 15 20 25 



Total length (mm) 



30 ^35 



Figure 3 



Length-frequency distributions of larval and postlarval Atlantic 

 croaker (Micropogonias undulatus) collected in the upper and 

 lower regions of Delaware Bay during the ichthyoplankton sur\'ey 

 in 1996^ 



0-56) in the upper bay zones 5-8 and 4.9 (range: 0-36) in 

 the lower bay zones 1-4 (Figs. 1 and 2), and these CPUE 

 values were significantly different between zones (P=0.03). 

 At least one individual was collected in each of the eight 

 zones in both September and October; the highest two- 

 month combined CPUE occurred in the uppermost zone 

 8 (CPUE=13.4), followed by zone 5 (CPUE=9.6), and the 

 lowest occurred in zone 3 (CPUE=0.1). Larvae were 4-10 

 mm during August (all in zone 2i, predominantly 2-24 mm 

 in September, and 5-28 mm in October (Fig. 3) — the small- 

 est individuals being caught in the lower bay. 



Benthic YOY Atlantic croaker of a variety of sizes first 

 appeared in substantial numbers in September in the 

 otter trawl surveys in both the bay (Fig. 4) and marshes 

 (Fig. 5) at lengths >5 mm, and with modes of 15-30 mm 

 for the primary cohort. Exceptions occurred in the bay in 

 1997, when they were not collected by the trawl survey 

 until October and when they were not collected during 

 September at two of the three upper bay marsh sites each 

 year. 



The CPUE of benthic YOY Atlantic croaker was usually 

 highest during October in the lower bay marshes (Fig. 6). 

 This pattern of abundance is illustrated by the much high- 

 er four-year overall CPUE of recently ingressed YOY, espe- 

 cially at Dennis Township, Commercial Township, and Up- 

 per Moores Beach (Fig. 7). The combined four-year CPUFI 

 values were significantly different (/'<0.001 ) at each of the 

 six sites, and the CPUE values at the Dennis Township 

 site were significantly greater than at all the sites except 



for Commercial Township. Similarly, Commercial Town- 

 ship was different from all sites except Dennis Township 

 and Upper Moores Beach, and Upper Moores Beach also 

 was different from Browns Run in the upper bay. 



Recently settled YOY Atlantic croaker were also caught 

 in the weirs in small intertidal marsh creeks during Sep- 

 tember, October, and November in all three years; the ma- 

 jority were collected at the Dennis Township marsh in the 

 lower bay (Fig. 8). The monthly CPUE (fish per set) in the 

 weirs at Dennis Township was greatest in October 1997 

 and November 1999 (the weirs were not in place until 

 October 1996) and the largest total number was collected 

 during 1999. The combined four-year CPUE values for 

 1996-99 at each of the six sites were significantly different 

 (P<0.001), and the CPUE values at the Dennis Township 

 site were significantly greater than those at all the sites, 

 except Commercial Township. 



The monthly CPUE values during ingress in the bay also 

 were highest in October, but in contrast to the marsh sites 

 were usually higher in the upper part of the bay (Fig. 6). 

 The combined CPUE values for September and October 

 were significantly different between the upper and lower 

 bay regions in 1998 (P<0.001) and 1997 (P=0.048), but not 

 in 1996 (P=0.51). The combined CPUE values for Septem- 

 ber and October for each year ( 1996-98) were significantly 

 different among years (P<0.001) and were different be- 

 tween 1996 and 1997, and between 1996 and 1998. 



A second, smaller cohort of YOY Atlantic croaker ap- 

 peared in the bay in -June and July 1998 and in the tidal 



