EFFECTS OF FRESHWATER RUNOFF ON FISHES OCCUPYING THE FRESHWATER 

 AND ESTUARINE COASTAL WATERSHEDS OF NORTH CAROLINA 



Frank J. Schwartz 



Institute of Marine Sciences 

 University of North Carolina 

 Morehead City, North Carolina 



ABSTRACT 



INTRODUCTION 



Presently 37 freshwater and 77 

 marine fishes, within 13 freshwater 

 and 38 marine families, respectively, 

 are known to inhabit the oligohaline 

 or euryhaline "freshwater" estuaries 

 of coastal North Carolina for pro- 

 longed periods. Most species are 

 typical primary, secondary, diadro- 

 mous, complementary or sporadic 

 fishes, as defined by Myers (1938; 

 1949a, b; 1951). Eighteen of the 

 freshwater and 37 of the marine 

 fishes noted are new additions to the 

 lists compiled by Schwartz (1964) and 

 Gunter (1942, 1956) of known fishes 

 which occur in low salinity fresh 

 waters. The extent of the euryhaline 

 zone created by seasonal or sudden 

 runoff conditions, is described for 

 each of the major coastal watersheds 

 of North Carolina. Maximum or mini- 

 mum salinity occurrence levels are 

 noted for each species frequenting 

 the area. Comments similar to 

 Gunter et al. (1974) are presented on 

 length of survival in low saline 

 water situations and/or responses to 

 other environmental variables, in 

 relation to fish size. 



habitats 

 Douglas 



Fishes are usually categorized 

 as primary, secondary, peripheral 

 freshwater or marine, yet we know 

 that there are anadromous, cata- 

 dromous, diadromous, amphidromous , 

 potamodromous , oceanodromous , vicar- 

 ious, complementary or sporadic 

 (Myers 1938; 1949a, b; 1951) fishes 

 that pass into or out of fresh or 

 marine regimes (Hoar and Randall 

 1979). Faunal fish surveys, however, 

 are usually stilted to sampling 

 either in fresh or marine 

 (i.e., Carr and Goin 1955; 

 1974; Livingston et al. 1976, 1977). 

 Occasionally, there have been efforts 

 to study the "salting out" effects 

 where fresh waters mix with marine 

 waters (i.e., Chesapeake Research 

 Consortium 1976; Lauff 1967; Wiley 

 1978). More importantly almost no 

 prolonged study has been aimed at 

 that unstable area where fresh waters 

 meet estuarine waters, the area 

 that was estuarine and which suddenly 

 is transformed into a freshwater 

 habitat by increased freshwater run- 

 off or to what happens to the fish 

 faunas of either regimes when 



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