though it has been assumed that they could see 

 color because of the relative numbers and ar- 

 rangement of rods and cones in the retina of 

 Tursiops (Perez et al. 1972). But since very little in 

 the animals' open ocean experience involves much 

 color, the painted marks may hold small sig- 

 nificance for them. 



Since our purpose was to test the feasibility of 

 paint marking of porpoises, no attempt was made 

 to create an ideal paint, though a paint formulated 

 specifically for marking doubtless would have been 

 better than those we used. Our experiments began 

 with available paints, and those that were found to 

 coat wet surfaces were modified for use in pres- 

 surized containers with high volume valves. Paint 

 manufacturers generally are prepared to process 

 only large volume orders, but we found that 

 smaller specialty companies were able to prepare 

 formulations to order and modify small quantities 

 of pressurized paint containers. 



Conclusions 



Paint marking of porpoises provides a satisfac- 

 tory short-term tag that can be applied at sea. The 

 paint has not modified the animals' behavior and it 

 seems not to be detrimental in any way. The high 

 visibility of the colors we tried often made it 

 possible to locate the marked animal when other 

 porpoises of the school were obscured. The under- 

 water paint marking technique would appear to be 

 potentially useful in the study of other aquatic 

 animals. 



Acknowledgments 



We appreciate the help and advice extended by 

 G.V. Cass of Krylon Department, Borden, Inc., 

 and Helene R. Johnson of Lenmar, Inc. We are 

 grateful also to the Naval Undersea Center, San 

 Diego, for their hospitality and good nature in 

 allowing our paint experiment, especially J. C. 

 Sweeney, Sam H. Ridgway, and William E. Evans. 

 Teresa Bray participated in laboratory test and 

 manuscript preparation. Support for this work 

 was from the Oceanic Biology Program of the 

 Oflfice of Naval Research, contract N00014- 

 74-C-0262. 



Literature Cited 



Evans, W.E. 



1974. Radio-telemetric studies of two species of small 



odontocete cetaceans. In W. E. Schevill (editor), The whale 

 problem, p. .385-394. Harvard Univ. Press, Camh., Mass. 

 Evans, W. E., J. D. Hall, A. B. Irvine, and J. S. Leatherwood. 

 1972. Methods for tagging small cetaceans. Fish. Bull U S 

 70:61-6.5. 



Harrison, R. J., and K. W. Thurley. 



1972. Fine structural features of delphinid epidermis. 

 (Abstr.) J. Anat. 111:498-500. 

 NoRRis, K. S., W. E. Evans, and G. C. Ray. 



1974. New tagging and tracking methods for the study of 

 marine mammal biology and migration, hi W. E. Schevill 

 (editor). The whale problem, p. 395-408. Harvard Univ. 

 Press, Camb., Mass. 

 NoRRis, K. S., and R. L. Gentry. 



1974. Capture and harnessing of young California gray 

 whales, Eschrhichtins rohustttx. Mar. Fish. Rev. 36(4): 

 58-64. 



NoRRis, K. S., and K. W. Pryor. 



1970. A tagging method for small cataceans. J. Mammal. 

 51:609-610. 

 Palmer, E., and G. Weddell. 



1964. The relationship between structure, innervation and 

 function of the skin of the bottle nose dolphin (Tursiops 

 truncatiis). Proc. Zool. Soc. Lond. 143:553-567. 

 Perez, .J. M., W. W. Dawson, and D. Landau. 



1972. Retinal anatomy of the bottlenosed dolphin (Tursiops 

 fruncatus). Cetology 11:1-11. 

 Schevill, W. E. 



1956. Lagenorhynchus acutus off Cape Cod. J. Mammal. 



37:128-129. 

 1966. Comments. In K. S. Norris (editor). Whales, dolphins, 

 and porpoises, p. 487. Univ. Calif. Press, Berkeley and Los 

 Ang. 



W.ATKINS, W. A., AND W. E. SCHEVILL. 



1975. Sperm whales (Physeter catodon) react to pingers. 

 Deep-Sea Res. 22:123-129. 



William A. Watkins 

 William E. Schevill 



Woods Hole Oceanographic Institution 

 Woods Hole, MA 02543 



GRAZING OF FRESHWATER AND ESTUARINE, 



BENTHIC DIATOMS BY ADULT ATLANTIC 



MENHADEN, BREVOORTIA TYRANNUS 



The diet of the Atlantic menhaden, Brevoortia 

 tymnnus (Latrobe), varies with stages in meta- 

 morphosis and the availability of food resources, 

 but it has been characterized consistently in the 

 literature as derived from the particulate organic 

 components of planktonic ecosystems (Reintjes 

 1969; June and Carlson 1971; Jeffries 1975; Peters 

 and Kjelson 1975; Durbin and Durbin 1975). Men- 

 haden larvae feed primarily by selective predation 

 on the larger estuarine zooplankters. Their meta- 

 morphosis into prejuveniles brings about the 



689 



