W. E. Evans is with the Naval 

 LJndersca Center. San Diego, 

 C A 92132. 



(Gigi II) captured by Sea World, Inc., 

 San Diego, on 13 March 1971, in 

 Scammon's Lagoon. Baja California. 

 Mexico, and the timing of the northern 

 migration of CaMfornia gray whales 

 (March-Aprill, the program was ac- 

 celerated to take advantage of this 

 opportunity. The prototype data trans- 

 mission/acquisition system had been 

 designed and bench-tested in anticipa- 

 tion of tests on a Pacific pilot whale. 

 ClohiccphaUi cf. sctiniiiuini. in mid- 

 summer 1972. The unit was repack- 

 aged and the test dates subsequently 

 moved up to coincide with the planned 

 release of the Sea World captive year- 

 ling gray whale which was scheduled 

 for 13 March 1972. It was then field 

 tested attached to the ,Sea World gray 

 whale when she was relased at 0905 

 hours at lat. 32°4I.5'N. long. 117° 

 20,5'W into a group of four to five 

 California gray whales moving north. 



DATA PARAMETERS 



Since one of our primary purposes 

 for using a data system attached to a 

 cetacean was to measure environ- 

 mental parameters associated with the 

 animafs movements below the air-sea 

 interface, the instrumentation used 

 must indicate the depth at which the 

 measurement was made. The follow- 

 ing parameters were considered as po- 

 tential indicators of productivity and 

 important correlates of cetacean 

 movement; 



1. Temperature at depth. 



2. Ocean current speed at surface 

 and at depth. 



3. Salinity-derived from conduc- 

 tivity measurements 



4. Dissolved gases: 



a. O2: 



b. No; 



c. FreeC02. 



5. Light; 



a. Absorption loss due to molec- 

 ular absorption, particulate 

 matter; 



Figure 1. — Block diagram of telemetry transmitter attactied to yearling California gray wtiale (Gigi). 



b. Backscattering from particu- 

 late matter; 



c. Light level at depth. 



After consideration of all these 

 parameters, temperature was selected 

 as the most desirable for this phase of 

 the program because; 1) methods of 

 measurement are straightforward elec- 

 tronically. 2) considerable bathyther- 

 mal data exist for the California C ur- 

 rent region, 3) data transmitted from 

 the instrumented animal could be 

 easily checked by use of currently 

 available expendable bathythermo- 

 graphs, and 4) a great deal of data 

 relating the thermal structure of the 

 water columns to primary and secon- 

 dary productivity are available in the 

 scientific literature (e,g. Eckman, 

 1953). 



INSTRUMENTATION 



Data Transmission System 



The data acquisition system mount- 

 ed on the yearling gray whale pro- 

 vided measurement of the depth of 

 each dive and the water temperature 

 at that depth, and served as a radio 

 beacon for tracking. Data measured 

 was telemetered by an 1 I meter trans- 

 mitter (27.585 megaHertz) to either a 

 surface vessel, shore station, or air- 



craft-based receiving set which would 

 also demodulate the data being trans- 

 mitted. Directional information for 

 tracking was obtained by a special fast 

 response automatic direction finder 

 developed several years ago specifical- 

 ly for this type of application (Ocean 

 Applied Research Corporation, San 

 Diego, Model ADF210).i 



A block diagram of the telemetry 

 transmitter is shown in Figure I . Func- 

 tion and operation are as follows; 



Pressure is measured by a semi- 

 conductor strain-gauge bridge excited 

 with constant current. The output 

 voltage is amplified by three opera- 

 tional amplifiers connected in an 

 "instrumentation amplifier" configura- 

 tion and the peak pressure reading 

 stored (remembered) on a capacitor 

 which is followed by an insulated-gate 

 field-effect transistor (LET). This 

 peak detector is inside the feedback 

 loop of the amplifier which maintains 

 accuracy and also yields a digital 

 zero at point A when pressure is de- 

 creasing from the peak depth. This 

 level is used to hold the temperature 

 reading. 



' Use of trade names in this publication does 

 not imply endorsement of commercial products 

 by the National Marine Fisheries Service 



53 



