Length-weight, Age 

 and GroNA/th, and Landings 

 Observations for Sheepshead 

 Archosargus probatocephalus 

 from North Carolina 



Frank J. Schwartz 



Institute of Marine Sciences, University of North Carolina 

 Morehead City, North Carolina 28557 



Sheepshead Archosargus jn-obato- 

 cephahis range from Nova Scotia to 

 Brazil (Robins and Ray 1986). Three 

 subspecies have been recognized, 

 based on the number and size of 

 body bars: A. p. probatocephalus 

 ranges along the Atlantic coast of 

 the United States; A. p. oviceps, 

 from St. Mark's, Florida to the 

 Campeche Banks; and A. p. aries, 

 from Belize to Babia de Sepetiba, 

 Brazil (Caldwell 1958, 1965). Little 

 is known concerning length-weight 

 or age and growth relationships for 

 this common edible fish. 



This paper presents the age and 

 growth and length-weight relation- 

 ships, reviews changes in historical 

 catch for sheepshead from North 

 Carolina, and resolves discrepancies 

 in the literature concerning max- 

 imum length and weight of this 

 species (Hildebrand and Schroeder 

 1928, Hildebrand and Cable 1938, 

 Bigelow and Schroeder 1953, Rob- 

 ins and Ray 1986). 



Methods 



Most specimens were captured in 

 12-m otter trawls, 91-m gillnets, or 

 by spear. Most specimens were ob- 

 tained from two sites where sheeps- 

 head are presently common in 

 North Carolina: the Masonboro and 

 Carolina Beach Inlets-Cape Fear 

 River area of New Hanover and 

 Brunswick counties, and Radio 

 Island Jetty, Carteret County, ex- 



tending from Beaufort Inlet in the 

 Atlantic Ocean to just south of 

 Shackleford Banks and Cape 

 Lookout Jetty. The largest speci- 

 mens and the state record-sized fish 

 were caught in the Carolina Beach 

 area by hook-and-line fishermen as 

 part of the state's fishing citation 

 progi'am. Specimens were measiu-ed 

 to the nearest millimeter standard 

 (SL) and total length (TL) and 

 weighed to the nearest gram, ex- 

 cept for the tournament fish, which 

 represented the upper end of the 

 length-weight curve and were 

 weighed to the nearest 114 g. Con- 

 version from total length to stan- 

 dard length, for study fish larger 

 than 100 mmSL, was possible by 

 the formula SL = 0.817TL, N= 240; 

 for fish smaller than 100 mmSL the 

 conversion formula was SL = 0.780 

 TL. The latter conversion was deter- 

 mined by utilizing data for 412 yoiuig 

 specimens (6-48 mm) measured by 

 Hildebrand at Beaufort, North 

 Carolina in 1914 (Hildebrand's field 

 notes, Inst. Mar. Sci., Morehead 

 City). Length-weight and standard 

 length-scale radius relationships 

 were calculated using log-log for- 

 mulas where log(y) = a + b log (x), 

 where x is either standard length or 

 scale radius, measured from the 

 focus to the outer lateral edge of the 

 scale, and y equals weight. 



Scales were removed for ageing 

 from just below the spinous/soft-ray 

 dorsal-fin junction and the area 

 above the lateral line. Scales were 



read at lOK magnification using a 

 Baush and Lomb dissecting micro- 

 scope. No validation of annulus for- 

 mation was attempted considering 

 the diverse availability of speci- 

 mens. Therefore, the values I report 

 are only presumed ages. 



Results 



The length-weight relationship for 

 282 sheepshead, measuring 9-591 

 mmSL (723 mniTL) and weighing 

 0.042-8370 g (18 lb, 7 oz), was cal- 

 culated by the formula log (y) = 

 - 4.5287 + 3.0446 log (x), r = 0.9929 

 (Fig. 1). 



A linear relationship between stan- 

 dard length and scale radius was 

 described for 68 fish measuring 

 31-525 mmSL by the formula log 

 (y) = 0.8801 -H 0.820 log (x), r = 

 0.9789. Too few scales from speci- 

 mens smaller than 30 mm were 

 available for inclusion in the rela- 

 tionship calculation. Scales of fish 

 17-400 mmSL or those to age 4 

 were easy to read. Scales of older 

 and larger specimens were difficult 

 to read as the focus often became 

 opaque and thickened, thereby 

 obscuring the first two annuli. 



Backcalculations of age and size 

 from 50 of the best scales suggested 

 seven age-classes (Table 1); how- 

 ever, these did not agree with a 

 simple length-frequency plot where 

 eight age classes seemed to prevail 

 (Fig. 2). Also the maximum back- 

 calculated size was 482 mm, where- 

 as the largest fish studied was 525 

 mmSL. This discrepancy strength- 

 ened the observation that perhaps 

 one or two annulae were obscured 

 on scales of specimens larger than 

 400 mmSL, which were probably 

 older than 8 years of age. 



Reference to trade names does not imply en- 

 dorsement by the National Marine Fisheries 

 Service, NOAA. 



Manuscript accepted 29 June 1990. 

 Fishery Bulletin, t'.S. 88:829-832. 



829 



