430 



Whale Movements in Relation to Hydrographic Factors and Submarine Geology 



To a marine mammal, the sea is probably an environment with many local 

 variations. It is possible that bottom topography — submarine canyons, ridges, 

 flat-topped seamounts, etc. — play an Important role in their distribution and 

 ecology. It is clear that oceanographic factors are important to them. The role 

 of these elements of the submarine environment could be explored by the con- 

 ventional means of correlating the occurrence of whales with them or by the de- 

 tailed tracking by means of telemetry of individuals carrying radio packages that 

 have sensors equipped for depth and temperature measurements (see below). 



Telemetric Studies of Free-Ranging Individuals 



Because we cannot directly observe whales in their natural environment, we 

 have had to develop our knowledge of cetacean natural history by inferences 

 drawn from dead animals and hrief observations of live animals when they w^ere 

 near the surface. The development of radio telemetry offers the possibility of 

 directly following known individuals for long periods of time, while also obtain- 

 ing data on the environmental conditions they meet and measurements of physio- 

 logical parameters from which behavioral responses can be deduced. It is tech- 

 nically i)ossible to equip a whale with a telemetry and recording package which 

 would allow the determination of location, a'bdominal temperature, water pres- 

 sure, light intensity, velocity, time, magnetic heading, water temperature, heart 

 rate, and breathing. From these data, it would be possible to follow an individual 

 (either alone or in a group) and obtain information about location ; direction and 

 speed of travel ; frequency, duration and depths of dives ; times and depths of 

 feeding ; and the nature of the water through which it passes. 



The Smaller Whales 



It is important that we consider not only the "commercial" species — the baleen 

 whales and the sperm whales — ^^but also the smaller whales, including the por- 

 poises and dolphins. These smaller cetaceans, although for the most part not 

 commercially exploited, represent a resource of major potential economic im- 

 portance. This has been clearly demonstrated by recent developments in the 

 American tuna fishery, which has produced a problem of great economic and 

 biological importance affecting delphinids of the genera Stenella and Delphinus. 

 Tuna fishermen locate schools of tuna by watching for porpoise and sea bird 

 activity. Having sighted a school, they enclose it in a long purse net which not 

 only captures the tuna but also the cetaceans. There is at present no practical 

 method for effectively separating these delphinids from the tuna. As a result, 

 the setting of one tuna net may result in the death of scores or even hundreds of 

 porpoises. Over most of the world, there is no good market for porpoise meat so 

 the dead i>orpoises are discarded. It has been estimated that in the eastern 

 Pacific alone as many as 250,000 porpoises are wasted annually as a result of 

 this situation. It is obviously only a matter of time until this extremely efiicient 

 method of tuna fishing becomes widespread. The resultant wastage of porpoises 

 will represent a major problem in all oceans. Aside from this specific instance, it 

 is clear that in view of the worldwide shortage of animal protein, in the near 

 future porpoise hunting as an end in itself will become an important enterprise. 

 At present, we do not have the biological information necessary to apply effec- 

 tive management to a porpoise fishery — even the alpha-taxonomy of the smaller 

 cetaceans is fragmentary. Knowledge of their natural history distribution — not 

 to mention their behavior and reproductive biology — is equally incomplete. 



George A. Bartholomew^, Jr., chairman ; A. Aguayo, W. Dawbin, R 



Gambell, A. Jonsgaard, K. Kenyon, T. Ichihara, C. Ray, V. 



Scheffer, W. Schevill, R. Vaz-Ferreira, members. 



Report of the Working Group on Regional Populations 



Stock identification is an important prerequisite for r*atiional exploitation of 

 a fishery. The working group considers that there are five main approaches to 

 thiis problem for cetaceans : studies of density distribution ; marking ; bio- 

 chemlical techniques ; morphometries and morphology ; and biological indicators. 



The working group considered these five main approaches in relation to 

 three categories of exploited sipecies : large cetaceans (the larger mystticetes 

 and Physeter) ; medium-sized cetaceans (minke, pilot, killer, belugas, narwhals 

 and all sipecies of beaked whales) ; and small cetaceans (dolphins, porpoises and 

 the remaining cetaceans) . 



