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Fishery Bulletin 101(1) 



creeks and large subtidal creeks within the study area. 

 Intensive tag and recapture studies in marsh creeks at the 

 Dennis Township site found that YOY were resident for 

 periods of up to 78 days from July through October 1998 

 (Miller and Able, 2002). As a result, our interpretations of 

 habitat use and gi-owth may be representative for much of 

 the summer and fall in Delaware Bay marsh creeks. 



In the deeper water of the bay, YOY were collected 

 throughout the whole range of salinities but were most 

 abundant over the predominantly pure mud sediments in 

 the lower Delaware River and over areas with mud sedi- 

 ments elsewhere in the lower bay. This pattern is evident 

 elsewhere because YOY have been reported to be most 

 abundant over soft mud sediments in Apalachicola Bay in 

 the Gulf of Mexico (Kobylinski and Sheridan, 1979). As in 

 Delaware Bay, YOY have been collected over the full range 

 of salinities in South Carolina (Bearden, 1964; Miglarese 

 et al.. 19821 and Georgia (Dahlberg, 1972). However, labo- 

 ratory experiments suggest that lower salinities are meta- 

 bolically less costly for YOY (Moser and Gerry, 1989; Pe- 

 terson et al., 1999) and that in some areas of Chesapeake 

 Bay, YOY are most abundant in regions with low salinities 

 (<18'7„) (Haven, 1957). 



Habitat use and survival in the winter may vary be- 

 tween estuaries. Young-of-the-year Atlantic croaker appear 

 to overwinter in estuaries in the Gulf of Mexico (Pearson, 

 1929; Suttkus, 1955; Hansen, 1969; Knudsen and Herke, 

 1978) and in the South Atlantic Bight (Bearden, 1964; 

 Dahlberg, 1972; Bozeman and Dean, 1980), but in the MAB 

 there is probably significant overwinter mortality in years 

 with particularly cold winters. The YOY appear to over- 

 winter in some estuarine habitats in the York River region 

 of Chesapeake Bay in most years (Haven, 1957; Chao and 

 Musick, 1977) and in deeper areas of the bay (Welsh and 

 Breder, 1923), but in some years YOY have been observed 

 to experience winter mortality based on their subsequent 

 disappearance after a cold period (Massman and Pacheco, 

 1960) and on direct observations of mass mortalities and 

 collections of dead YOY in years with unusually cold 

 winters (Joseph, 1972; Chao and Musick, 1977, Wojcik, 

 1978). Further, analysis of long-term recruitment indices 

 for Atlantic croaker from 1979 to 1993 indicates that the 

 YOY of this species may have experienced winter mortal- 

 ity due to low water temperatures in 30'7f of the years in 

 Chesapeake Bay and 74*7^ of the years in Delaware Bay 

 I Lankford and fargett, 2001 ). 



Overwintering mortality apparently occurred in Dela- 

 ware Bay in 1996 when water temperatures in the region 

 dropped below 3°C and remained below 4°C for an extend- 

 ed period of time. The NOAA Buoy 4409, located in the 

 ocean just south of the mouth of Delaware Bay, recorded 

 water temperatures at about 2-4°C for 18 days during 

 January and February 1996, which is at or below the ap- 

 proximate survival temperature of 3°C determined in lab- 

 oratory experiments (Lankford and Targett, 20011. This 

 apparently resulted in a total absence of YOY throughout 

 the bay and in marsh creeks during the spring and sum- 

 mer, which is not surprising because temperatures in the 

 estuary were likely cooler than in the ocean. In contrast, 

 during the winters preceding the relatively high catch 



years of 1997 and 1998, water temperatures at the same 

 location never dropped below 4.4°C during the winter of 

 1996-97 or below 5.6°C during 1997-98. 



Growth 



Growth rates that we calculated in both upper and lower 

 regions ofthe Delaware Bay (two years) and in the marshes 

 (three years) ranged from about 0.8 to 1.4 mm/d from May 

 to July. The strong linear correlation between median 

 length and date suggested that the average growth rates 

 were relatively constant during the summer from May to 

 August before egress from marshes. Seasonal growth rates 

 of YOY Atlantic croaker in other estuaries along the Atlan- 

 tic coast may be similar to those in Delaware Bay, but the 

 way in which they were calculated influences the values. 

 Knudsen and Herke ( 1978) reviewed the apparent growth 

 rates of YOY Atlantic croaker from a variety of sources 

 but presented growth rates only for the entire first year 

 of growth, which were all less than 0.5 mm/d for studies 

 along the Atlantic coast and in the Gulf of Mexico. How- 

 ever, these estimates included both larval and overwinter- 

 ing periods; therefore they probably underestimated the 

 growth rates during the summer when growth rates are 

 highest. Monthly modal progression in published lengths 

 indicate relatively fast growth rates during the summer 

 in estuarine areas south of Delaware Bay Our calculation 

 of modal progression in lengths from May to July in vari- 

 ous parts ofthe York and Pamunkey rivers of Chesapeake 

 Bay suggested growth rates of approximately 1.3 and 0.7 

 mm/d in 1952 and 1953, respectively (Haven, 1957) and of 

 0.9 mm/d in 1972 (Chao and Musick, 1977). Similarly cal- 

 culated values for May to July for fish from shallow creeks 

 in North Carolina indicated growth rates of 0.6, 0.8, and 

 0.9 mm/d in 1979, 1980, and 1981. but the 1979 estimate is 

 likely to be an underestimate because many of the larger 

 fish appeared to be moving into deeper habitats during 

 that time period (Ross, 1988). In our study, the growth 

 rates remained relatively high when calculated through 

 October (1.1-1.3 mm/d) in the bay but dropped off in the 

 marshes (0.5-0.7 mm/d), potentially reflecting the egress 

 of larger YOY out ofthe marshes into the bay. 



Data from the Gulf of Mexico suggest slower growth rates 

 of YOY Atlantic croaker in some areas but egress of larger 

 fish out ofthe sampling area may also bias these estimates. 

 Hansen (1969) used length-frequency data to determine 

 growth rate estimates of 0.3 mm/d from January through 

 August in the Pensacola Estuary on the Florida gulf coast 

 in both 1964 and 1965 but noted the highest growth rates 

 were in July (0.6 mm/d). Knudsen and Herke (1978) es- 

 timated gi-owth of YOY in a semi-impounded marsh in 

 Louisiana using recaptured individuals sprayed with 

 fluorescent pigment during winter and spring and found 

 rates of 0.4-0.5 mm/d for fish marked in late January and 

 early February and recaptured into March. Rates for those 

 marked mid-F'ebruary to late March and recaptured into 

 May were 0.8-0.92 mm/d. A previous study at the same 

 location, using the same techniques, estimated that fish 

 marked from December to March and recaptured into June 

 grew at about 0.47 mm/d (Arnold! et al., 1974 ). The monthly 



