FISHERY BULLETIN: VOL. 70, NO. 1 



mal were of most importance in predicting the 

 probable response of naive wild porpoise, as the 

 animals were able quickly to achieve high levels 

 of performance even at very shallow depths. 



CORKLINE 



A corkline across the toj) of the ojiening caused 

 Waimea (III) and Nani (II) to fail on initial 

 trials, and greatly affected the performance of 

 Nohea (IV) . Waimea, after four failures, over- 

 came reluctance to pass through an oi:)ennig with 

 a corkline at the surface and reachieved a high 

 level of performance. An interaction between 

 the corkline and depth of opening was apparent 

 in the factorial experiment with Nohea. Initial 

 trials with the corkline (second block) produced 

 a temporary drop in performance with a 1.1-m- 

 deep opening. In the fourth block, the corkline 

 was again inserted, and performance dropped 

 at 0.61 m depth but not at 1.1 m. 



MONOFILAMENT PANEL 



When the panel of nylon monofilament web- 

 bing was inserted into the opening (1.1 m deep) 

 after a series of trials in which performance was 

 consistently high, Waimea (IV), Nani (III), and 

 Nohea (III) swam into the webbing as if it did 

 not exist. Performance in subsequent trials 

 without the i^anel was not affected (Nani III). 

 Upon hitting the webbing, the porpoise became 

 entangled and had to be extricated by a diver. 



POLYVINYL PANEL 



In the two single trials with a panel of clear 

 polyvinyl sheeting inserted in the opening, Nohea 

 (V and VI) hit the ])anel and slid over the top 

 as it buckled. No difference was noted in be- 

 havior in these trials from that in trials in which 

 the panel was absent. 



During these experiments Nohea in several 

 trials passed back and forth through the opening 

 two or three times after the initial escape, while 

 the net wall was being closed. The values for 

 the surface area index shown in the figure are 

 for the first passage. The incidence of such be- 

 havior throughout the course of all the experi- 

 ments occurred only after considerable expe- 

 rience with a particular net configuration. In 

 most cases, only one or two double "escapes" 

 occurred during an experiment. 



EXPERIMENTS WITH 

 NAIVE PORPOISE 



Eleven experiments were conducted with the 

 naive porpoise (Table 3, Figures 5 and 6). The 

 first naive animal. Westward, was captured on 

 June 12, 1970, and after a relatively short han- 

 dling period was placed in Bateson's Bay. Her 

 swimming behavior during the first 5 days of 

 captivity was unlike that of the trained porpoise. 

 The trained porpoise continually swam about the 

 tank during and between experiments, diving 

 and "porpoising," and spinning. Westward, on 



Table 3. — Experiments with naive porpoise. 



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