AGE, SIZE, GROWTH, AND CHEMICAL COMPOSITION OF 



ATLANTIC MENHADEN, BREVOORTIA TYRANNUS, FROM 



NARRAGANSETT BAY, RHODE ISLAND 



Ann Gall Durbin, Edward G. Durbin, Thomas J. Smayda, and 



Peter G. Verity 1 



ABSTRACT 



Age and size were determined for 2,015 Atlantic menhaden caught in Narragansett Bay, R.I., 

 during 1976. Atlantic menhaden were predominantly age 2 and age 3, and in all age groups were 

 significantly smaller than fish caught from Long Island Sound to the Gulf of Maineduring 1955-71. 

 The chemical composition of the Atlantic menhaden, as determined from analysis of selected sub- 

 samples, was ash— 10.94. carbon— 56.61, and nitrogen— 8.03% of dry weight; kilocalories— 6. 238 per 

 gram dry weight and 7.002 per gram ash-free dry weight; and dry weight — 33.4% of wet weight. 

 Instantaneous annual growth rates during the years 1970-75 were estimated from back- 

 calculated fork lengths and wet weights at the time successive scale annuli were formed. Instanta- 

 neous daily growth rates of Atlantic menhaden in Narragansett Bay during 1976 were estimated 

 from the growth of the scale margin beyond the 1976 annulus, and from the increase in mean fork 

 length and wet weight of the fish as the season progressed. Growth rates of age 2 and age 3 Atlantic 

 menhaden in 1976 were considerably greater than the respective average growth rates estimated 

 for previous years, suggesting significant differences in age-specific growth rates of Atlantic 

 menhaden in different regions and different years. 



The Atlantic menhaden, Breroortia tyrannus, is 

 a schooling, plankton-feeding clupeid which 

 ranges inshore along the Atlantic coast from 

 Florida to Maine. It makes extensive seasonal 

 migrations, moving north during spring and 

 south during fall (Nicholson 1971, 1972, 1978). 

 Atlantic menhaden are usually present in 

 Narragansett Bay, R.I., from April to Novem- 

 ber, with peak abundance from June to mid- 

 September. Here we report measurements of 

 age, size, and chemical composition of menhaden 

 caught in Narragansett Bay during 1976. We 

 also report the first calculations of instantaneous 

 growth rates in fork length and wet weight, as 

 measured from scale annuli of individual fish. 

 These data are part of a larger study to deter- 

 mine the energy budget of adult menhaden in 

 Narragansett Bay. 



METHODS 



Atlantic menhaden were sampled from the 

 catch of two purse seiners, operating from Point 

 Judith, R.I. During 1976, fishing activity fluc- 

 tuated considerably, according to abundance 

 and availability of Atlantic menhaden in Nar- 



'Graduate School of Oceanography, University of Rhode 

 Island, South Ferry Road, Narragansett, RI 02882. 



ragansett Bay. Most of the catch was obtained 

 during early June and from late July to early 

 September. All samples were collected during 

 these two periods, with two additional samples 

 collected on 7 October and one on 4 November. 



Random samples of fish from a purse seine set 

 were stored on ice and returned to the laboratory 

 at the end of the day. A total of 2,262 fish were 

 sampled from 24 purse seine sets. An average of 

 94 fish were collected per set, with a maximum of 

 2 sets sampled on a given day. About 11% (247 

 fish) that had regenerated scales, and therefore 

 could not be aged, were excluded from further 

 analysis. 



Wet weight and fork length were recorded, 

 and several scales were collected for age deter- 

 mination (June and Roithmayr 1960). Every 

 fifth fish from each sample was collected into a 

 subset of five fish and frozen for dry weight de- 

 termination or chemical analysis. Dry weights, 

 for the calculation of wet weight:dry weight 

 ratios, were determined by drying groups of 

 these frozen fish at 105°C to constant weight. 

 Fish used for chemical analysis were homogen- 

 ized, while still frozen, with an equal volume of 

 distilled water. Ash, carbon, nitrogen, and calor- 

 ic contents were determined for subsamples of 

 the freeze-dried homogenate. The ash content 

 was measured by combusting samples at 475°C 



Manuscript accepted Julv 1982. 



FISHERY BULLETIN: VOL. 81. NO. 1, 1983. 



133 



