(10.01%). Food chain efficiencies were lower than ecological efficiencies, 

 suggesting under-utilization of available food. Hard clam, with lowest feeding 

 rate, was more efficient at utilizing food it filtered and so had the highest 

 net production (=ecological efficiency) . In contrast, mussels had the highest 

 feeding rate but lowest ecological efficiency. Rates of regeneration of 

 nutrients, especially total inorganic N, and high biodeposition rates of 

 bivalves suggest that multispecies aquaculture systems would be more 

 efficient and productive than one-species systems. - modified authors' 

 abstract - J.L.M. 



1795 



Thayer, Gordon W. , S. Marshall Adams, and Michael W. LaCroix. 1975. 



Structural and functional aspects of a recently established Zostera marina 

 community. Proc . 2nd Internatl. Estuar. Res. Conf. 1: 518-540. In 

 Estuarine Research. Vol. 1. Chemistry, Biology, and the Estuarine System. 

 L. Eugene Cronin (edj . Academic Press, Inc., New York: 518-54 0. 



The study area was Phillips Island, near the mouth of the Newport River 

 estuary, near Beaufort Inlet, N.C. Mercenaria mercenaria ranked 35th among 

 45 species of epifauna, making up 0.05% of the organisms by number. No other 

 specific reference is made to hard clam. - J.L.M. 



1796 



Thilberg, G. W. 1975. 



The role of law enforcement. In Proceedings of a Workshop on the Shellfish 

 Management Program in New York State. N.Y.S. Dept. Envir. Conserv. and N.Y. 

 Sea Grant Inst., Albany: 34-36. 



The main responsibility of the Division of Law Enforcement with respect to 

 shellfish is to patrol noncertified shellfish areas. Not too long ago the 

 total force was 6 officers and limited equipment. In 1975 the complement of 

 officers was 34, and equipment included boats with radar, fast skiffs pov/ered 

 with outboard motors, radio-equipped cars, and walkie-talkies. It was believed 

 that very few shellfish from closed areas were getting to market. Another 

 problem is illegal harvesting and marketing of high-value undersized clams or 

 "seed clams". On Long Island 90% of enforcement effort was concentrated on 

 marine resources. Leniency in the courts also was a problem. Suffolk County 

 has assigned an Assistant District Attorney to handle conservation cases only. 

 Illegal shellfish harvesting also was being discouraged by suspension of 

 permits and seizure of boat, motor and all equipment. - J.L.M. 



1797 



Thompson, Ida. 197 5. 



Biological clocks and shell growth in bivalves. In Growth Rhythms and the 

 History of the Earth's Rotation. G. D. Rosenberg and S. K. Runcorn (eds.) . 

 John Wiley Inc., London: 149-162. 



Mercenaria mercenaria, 40 to 55 mm shell height, was the experimental animal. 

 Before experiments began the growing edge was rubbed to break the periostracal 

 seal, leaving a notch in the shell. Experimental tanks were closed systems in 

 which the liquid medium was instant ocean. Semidiurnal intertidal experiments 

 simulated a 12.4 hr tidal cycle in which clams were exposed to air for half 

 the period. The light cycle was 12 hr light, 12 hr darkness. Temp varied 

 with light cycle from 20-26°C. In non-tidal experiments water level was 

 constant, light cycle was 12 hr light, 12 hr dark, temp was 19 ± 2°C. Constant- 

 condition experiments had constant water level, constant light, and temp 

 19 ± 2°C. Duration of experiments was 36 to 130 days. Clams were not fed. 

 Valve movement was measured automatically with a lever which magnified 

 movements 2.5 times, connected to a recorder. Valve movement was clearly 

 rhythmic in all experiments. In the simulated intertidal experiment the 

 pattern of rhythms was similar in individual clams. In the non-tidal regime 

 patterns of rhythms varied among individuals. In the constant-conditions 

 regime variation was even greater, but rhythms continued, demonstrating 

 presence of a bioclock. Microscopic study of shell sections showed that the 

 number of open intervals and number of daily growth increments corresponded 

 closely. Shell growth maps shell movements, and is bioclock-controlled. In 



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