Collaboration with fishermen gained insight into how many whales were involved, their sex, what fishing behaviors and acoustic cues* may lead to depredation. We found:

a median of 90 male sperm whales were present in our study area who actively remove fish from longline gear,

if whales are present at the haul there is a high likelihood of depredation, however there is a seasonal effect (reduced early in the season),

One-third of all monitored sets (n=124) had whales near the longline gear during the set, soak or haul.

Of the hauls with whales, 71% had some evidence of depredation.

Depredation was lowest in March and highest during mid summer.

Based on these observations we have derived six low-cost depredation reduction techniques that we propose to quantitatively test over the next two years:
minimize engine cycling while hauling, which seems to attract animals,
deploying anchor lines that have no fishing gear attached (decoys),
acoustic monitoring with a low-cost hydrophone from fishing vessels prior to setting gear,
testing of an existing variant of fishing gear that includes acoustic reflectors and shortened gangions,
changing the time of year the fishermen deploy their gear and
retaining offal onboard until the end of the haulback.

Tentative acoustic observations:

How are whales finding gear?
No distinctive sounds by longline alone or hydraulics
Strongest candidate: way boat is handled
Detection range analysis requires bathymetry (added 2005)

How are whales taking fish?
Visual or acoustic? Very active acoustically
What depth are they taking fish? 50 m vs. 250 m
Are whales targeting dropped fish? Probably

Is avoidance a viable strategy?
Whale detection range at least 10 nm