UNDERWATER PAINT MARKING 

 OF PORPOISES^ 



Identification of individual animals has always 

 been a problem in cetacean behavioral research. 

 Only a small part of the animal is ordinarily 

 visible, and individuals within a pod of whales or 

 porpoises may all look very much alike, and, for 

 that matter, very much like all the individuals in 

 all neighboring pods. How does one mark (or label) 

 an animal at sea? 



Our radio tagging experiments and flashing 

 light systems (Schevill and Watkins-) were design- 

 ed to provide a partial solution to this problem, 

 and, more recently, radio transmitters have been 

 attached to animals by means of harnesses or 

 other fastenings (Evans 1974; Norris and Gentry 

 1974; Norris et al. 1974). Conspicuous visual marks 

 have often been suggested, and a few have been 

 successfully contrived for particular experiments, 

 including freeze-branding, brightly colored 

 buoyant lines, buoys, and plastic numbered but- 

 tons toggled through dorsal fins (Norris and Pryor 

 1970; Evans et al. 1972) 



We have been loath to use acoustic tags on 

 animals that react to the noise of ships, and even to 

 low-level pingers (Watkins and Schevill 1975). 

 Frequencies that are above their hearing would be 

 useful only at short ranges because of attenuation 

 of high frequencies in seawater. 



Ideally, we wanted a mark that was highly 

 visible, that could be varied, that had no effect on 

 the behavior of the animal, that would last for long 

 periods of time, and that was easy to apply at sea. 

 Even a temporary mark permitting positive iden- 

 tification for only a few hours would be a boon. 

 Paint seemed an answer (Schevill 1966). 



Materials and Methods 



Several standard paint formulations were tried; 

 some could be applied to a wet surface, and some 

 would set relatively quickly underwater. Applica- 

 tion of these paints was easiest by pressurized 

 spray. We experimented with spray volumes, 

 velocities, propellants, and methods of controlling 

 the paint. A propellant that mixed well with the 

 paint carried it in a discrete stream, preventing 



immediate mixing with the water, and higher 

 volumes of the paint mixture provided more 

 effective displacement of the water on the surface 

 to be painted. In our most satisfactory marking 

 system, we used 186-g (6-ounce) pressurized cans 

 of paint with a fire-extinguisher type of valve to 

 deliver short bursts of paint at about 125 g/s. A 

 nozzle 3 cm long with a 3.5-mm orifice was 

 fabricated to actuate the valve and direct the paint 

 in a coherent stream (in air, 2 or 3 m horizontally). 

 An internal modification to the standard container 

 removed the dip tube so that the can could be used 

 in an inverted position. For ease in handling and to 

 allow the stream of paint to be brought close to a 

 passing animal (as from the bow of a ship), a 

 holder for the paint can was mounted at the end of 

 a pole. 



Paint bounced off most hard-surface materials 

 before it could set underwater, unlike human or 

 porpoise skin which appeared to have approxi- 

 mately equivalent temporary reactions to paint. 

 But paper masking tape (3M-Scotch 183),^ which 

 has a softer surface, reacted somewhat like skin to 

 both the paint and the water, and was used as an 

 underwater test surface. 



Two paints were selected: a red lacquer based on 

 a nitrocellulose/alkyd vehicle and a red-orange 

 fluorescent based on an acrylic ester resin vehicle."* 

 These paints solidify by removal of the solvents 

 rather than by oxidation, as in the usual paint 

 preparations. The paint containers were capped at 

 about 4.2 kg/cm- (60 Ib/in^) at room temperature. 

 A 5% change of pressure can be expected with 

 each 5°C change in ambient temperature; can 

 temperature is critical for adequate pressure. 



Tests were conducted in a 3-m-^ tank of flowing 

 seawater, and water temperatures were controlled 

 from 20.9°C in steps of a degree or less to 3.45°C, 

 and a comparison was made for each temperature 

 at several depths. Both paints penetrated the 

 water in a coherent stream, adhered to the test 

 surface, and set (hardened) underwater. The red 

 lacquer set within a second or two, but was con- 

 siderably dulled when applied through the water. 

 The fluorescent red-orange was largely unaffected 

 by underwater application, except that its setting 

 time was extended by 10-15 min. Patches of both 



'Contribution No. 3586 from the Woods Hole Oceanographic 

 Institution. 



-Schevill, W. E., and W. A. Watkins. 1966. Radio-tagging of 

 whales. Unpubl. manuscr., 15 p. Woods Hole Oceanogr. Inst. Ref. 

 No. 66-17. 



^Reference to trade names and manufacturers does not imply 

 endorsement by the National Marine Fisheries Service, NOAA. 



-•These two paints are similar to formulation AL-98 and V-129 

 by Lenmar, Inc., 150 South Calverton Road, Baltimore, Md. 

 These and other formulations and colors recommended by 

 Lenmar have been tested and appear to have equivalent under- 

 water characteristics. 



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