Abstract.— Knowledge of popu- 

 lation dynamics and production of 

 dominant benthic organisms on the 

 northwestern Atlantic continental 

 shelf is important for developing or 

 interpreting models addressing eco- 

 logical or fishery management ques- 

 tions. This paper estimates the re- 

 cruitment frequency and success, life 

 span, growth rate, and production 

 of a major component of the sand- 

 bottom benthic community in this re- 

 gion: the common sand dollar Echl- 

 naracluiius parma (Echinodermata: 

 Echinoidea). These estimates are 

 based on size-frequency data col- 

 lected at least annually between 1977 

 and 1985 from three sites in the Mid- 

 dle Atlantic Bight and one site on 

 Georges Bank. Larval recruitment of 

 E. parvia to the sites was mostly an- 

 nual, but persistent cohorts were ir- 

 regular. Average life span was about 

 8 years with some rare, larger, and 

 presumably older animals present; 

 the ma.ximum size found was ,54 mm. 

 A time series of modal size progres- 

 sions suggests mean growth in body 

 width ranged from 3.5 to 6 mm/yr 

 over a period of at least 5 years, with 

 growth curves for cohorts appearing 

 to be sigmoidal. Annual production: 

 biomass ratios for definable cohorts 

 varied with age, ranging from -0.04 

 for senescent older cohorts to 8.10 

 for juveniles. 



Population Dynamics, 

 GrowtPi, and Production 

 Estimates for the Sand Dollar 

 Echinarachnius parma 



Frank W. Steimie 



Sandy Hook Laboratory. Northeast Fisheries Center 

 National Marine Fisheries Service, NOAA 

 Highlands. New Jersey 07732 



Manuscript accepted 18 .July 1989. 

 Fishery Bulletin, U.S. 88:179-189. 



Information on growth and produc- 

 tion rates of major marine taxa can 

 support the development of better 

 ecological and fishery production 

 theories or models (Winberg 1971, 

 Greze 1978). Echinoderms are one of 

 the major marine benthic taxa; how- 

 ever, information on their gi'owth and 

 production rates is scarce. For exam- 

 ple, production estimates are cur- 

 rently available for little more than 

 a dozen species worldwide (Richards 

 and Riley 1967, Zaika 1972, Miller 

 and Mann 1973, Buchanan and War- 

 wick 1974, Greze 1978, Warwick et 

 al. 1978, Warwick and George 1980). 

 On the Atlantic continental shelf 

 north of Cape Hatteras, North Caro- 

 lina, the sand doWar Echinamchniufi 

 parma is an abundant echinoderm of 

 fine to medium-sand habitats (Coe 

 1972, Wigley and Theroux 1981). Be- 

 cause of its relatively large size (>50 

 mm) and population densities which 

 can reach hundreds of adult individu- 

 als per m- (Caracciolo and Steimie 

 1983), it may be a "keystone" species 

 as defined by Paine (1969), i.e., a ma- 

 jor factor in structuring the benthic 

 community by dominating habitat and 

 detrital food use. Stanley and James 

 (1971) conclude this species to be the 

 second most important factor, after 

 major storms, in reworking surface 

 sediments. This sediment reworking 

 can disturb smaller epifaunal benthic 

 species and larval recruitment, which 

 can include shellfish species of com- 

 mercial interest. For example, Rich- 



ardson et al, (1983) studied an E. par- 

 ma community off Rhode Island, and 

 studies of similar Pacific and Atlantic 

 sand dollar species Dendraster excen- 

 t7-icus and Mellita quinquiesperfora- 

 ta by Smith (1981), Creed and Coull 

 (1984), and J. A. Reidenauer (Dep. 

 Oceanogr., Fla. State Univ., Tallahas- 

 see, FL 32306, pers. comm., July 1985) 

 found that aggregations of sand dol- 

 lars substantially alter benthic macro- 

 fauna community structure, especi- 

 ally for tube dwellers and meiofauna. 

 Besides its potential role in control- 

 ling benthic community structure, E. 

 parma also occurs frequently in the 

 diets of some commercially/recrea- 

 tionally valuable fish, including had- 

 dock Melanogrammus aeglefinus, 

 summer flounder Pa ralichthys denta- 

 tus, American plaice Hippoglossoides 

 platessoides, scup Stenotomns chry- 

 sops. tautog Tautoga onitis, and yel- 

 lowtail flounder Limandaferruginea 

 (Bigelow and Schroeder 1953, Coe 

 1972, Maurer and Bowman 1975, 

 Collie 1987). However, its food value 

 (Kcal/g) is half that of other common 

 benthic prey, e,g., polychaetes or 

 crustaceans (Steimie and Terranova 

 1985). Despite wide use of £". parma 

 as prey, extensive populations of this 

 echinoderm, primarily of individuals 

 too large to be eaten by most preda- 

 tors, may be an energy sink (Mercer 

 1982), For example, E. parma can 

 comprise 40-50% of the total benthic 

 macrofaunal biomass on Georges 

 Bank (Steimie 1987). 



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