the bunches which ad ns a dam. The blocked water rorees the small mesh 

 ontboard of the third bow bunch to canopy out and when stretched to its limit 

 the corkline begins to sink, me faster the net was rolled the more rapidly 

 water bad t<> be squeezed oul and the deeper the corkline Bank. It was found 

 thai this kind <>f Sinking COUld l>e easily alleviated by release of the third and 

 second bunches slightly earlier than normal. With large catches (>."><> tons) it 

 may be necessary to roll the net aboard a little more slowly. 



On set :;::. schOOlfisb with a log, a very Strong surface current and an ohlique 

 subsurface CUrrenl caused the entire area of small mesh from the second how 

 bunch to mid net to sink and stay down until the purse rings Were brought up 

 out of the deep current. The surface current moved the log and almost all of 

 the fish over the sunken corkline. It was not possible to judge the degree to 

 •which the small mesh was responsible for the sinking hut it surely contributed 

 to it. To avoid this problem in areas of strong currents, the captain must note 

 the current direction and position all sets to avoid pursing the small mesh area 

 of his net against t he current . 



As with the "Bold Contender" system there is a tendency for the center of 

 the "super apron" to fold into or out of the net in some sets. On 15 sets a 

 speedboat was used without incident to open or adjust the backdown apex prior 

 to backdown. Xo maintenance was required on the small mesh during the 

 cruise and only a few broken meshes and shark holes were seen hy the 

 underwater observer. 



Inflatable Raft 



During 39 of 4."> porpoise sets a small inflatable raft was used as an 

 observation-and-reseue platform by one of the scientists. A mask and snorkel 

 was employed. The raft man signaled the captain when the backdown release 

 area was clear of fish. In addition, he assisted in the removal of the last few 

 porpoise in the late stages of backdown. Generally, backdown was continued 

 until the raftman signaled that all porpoise including the "passive" spotters 

 (see ahove) had been released. In checking to see if all live porpoise were 

 out of the net it was discovered that the raft man could hear vocalizations of 

 porpoise that were still in the net but could not he seen. This final listening 

 check became common practice and several animals were saved as a result. The 

 raft was also used during hack down to herd the porpoise toward the release 

 .area. This seemed to work well but only if the raft stayed more than about 

 10 meters from the nearest animals. When some groups of porpoise (10-100) 

 would refuse to go over the corkline during backdown the raft man would 

 wait until they were congregated near the sunken corkline and then paddle 

 straight at them making as much commotion as possihle. The initial avoidance 

 response of the nearest animals often started them over the corkline and 

 backdown would proceed to completion. 



In four sets with expected large catches of fish the raff was used to attach 

 up to four flotation balloons to the corkline along the sides of the backdown 

 apex to lessen the chance of fish loss if all of the fish happened to move into 

 the apex at one time. This was probably a good safeguard but it was never 

 really tested with a large catch. After backdown the balloons were collected 

 in the raft to facilitate net retrieval. 



summary 



The record low mortality rate experienced on the charter cruise is the result 

 of the concurrent evolution of improved fishing techniques and gear modifica- 

 tions developed hy NMFS and the tuna industry and increased awareness of the 

 captain and crew of the necessity to reduce incidental porpoise mortality. The 

 following general list summarizes the activities which allowed the low mortality 

 rate. 



1. Set positioning to minimize negative effects of wind and current. 



2. Early recognition of potential net collapse areas and use of speedboat (s) 

 to prevent collapse. 



3. Use of speedboats to herd porpoise out of potential danger areas. 



4. Use of speedhoats to adjust hackdown area corkline prior to backdown. 



5. Consistent use of two or three speedboats at hackdown apex to prevent fish 

 loss and to rescue porpoise. 



G. Consistent backing down until all live porpoise are out of the net (very 

 important). 



