Ah, springtime...the trees blossoming, the fish returning, and the annual black box debate.
I have mixed opinions about black boxes. It seems pretty hokey, that the voltage of a flashlight bulb will make any difference to gear wildly spinning 50-100 feet deep, passing by at 2 knots or more. However, I can't entirely rule out the possibility it is a contributing factor. Just as I don't bring bananas on my boat and each sunrise shake ju-ju beads over the downrigger...anything that has a remote chance of helping catch a fish I'm willing to try.
I am an overly analytic and hyper rational person and I'd like fishing to be a science...isolate the variables that matter, control for the rest, voila, success. But I am starting to realize that what is fun about fishing is the uncertainty -- way too many variables to control and a degree of randomness thrown in. Best you can do is be vigilant about doing the best you can do, and then spend as much time on the water as possible. I think that's what separates the slayers from the try-hards, knowing which factors are key, attention to the details, never cutting corners, and knowing when to switch things up. Plus a huge amount of water time.
Black box is one more factor among MANY MANY others. I put it in the category of maybe it helps, but it can't hurt. I can say with certainty though that if you suck at fishing without one, adding one isn't going to help much! [

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[Backatit: you should tell your friend he should work for greenpeace, think of how many sea creatures he has singlehandedly saved?]
[Black box studies: there's some scientists on this forum who can speak with more authority than me about scientific method, but I don't think we'll ever get a definitive answer on black boxes really working or not. There's too many variables that can't be controlled for in the ocean. I think you'd need a closed environment, a big pool with fish in it, then use the same gear with black box and without, and see difference. On the ocean, maybe a reasonable approximation would be to take someone who is a regular fisher and does well. They turn black box on every half hour and then off for next half hour. Keep stats on when there are bites, fish like this for a month or so in peak season, then see if there's any substantial difference. A good thesis for someone maybe...but otherwise not likely to happen, the only people with a stake in it are manufacturers. They lose everything if prove it does not work. So, is the lack of definitive studies by Scotty or ProTroll a sign? Surely they would publicize a study if it showed definitively their product works? Scotty is now producing and selling nylon cable, eliminating need for their own black box product...is that a sign of what they really think? Enquiring minds want to know!]
PS...the partially controllable randomness that makes fishing fun...this is the same thing that makes gambling fun! (why many anglers are basically gambling addicts IMO) It is luck of the draw in the end, but those who use systems to up their chances of winning will consistently win more than those who don't. Black box is one more system.