Why are you thinking halibut don't hit mackerel? I'm curious to know your reasoning.
The mackerel I caught for bait were about 8" long.
I lean toward the "big bait, big fish" adage to more narrowly target the fish I want to catch, and to try to avoid collateral damage to undersized fish and other living creatures I don't want to disturb. I recognize that I'm an omnivore, but I also respect and enjoy the sanctity of life around me. Seeing humpback whales and pods of dolphins around me thrills me as much as catching a nice size halibut for dinner.
I'm not a catch and release guy. I'm a catch and eat guy. If I'm not fishing for my favorite fish to eat, then I'm a "live and let live" guy who enjoys the escape, exercise, exploring ideas and relaxation with nature.
Anchovies are no doubt yummy to halibut on light tackle in shallow water on something like a Carolina rig. Larger halibut will bite it too, but I think small anchovies increase the number of undersized halibut we catch. Bass and lots of other fish will chomp on anchovies. I don't want to catch bass, especially when they suck down a trap hook.
The reason I don't care for sardines is because they seem to die too easily, especially if I'm rigging a trap hook. Maybe I don't know how to rig sardines so they survive longer. Mackerel are more durable. Six mackerel will usually be plenty for my half day of fishing and I'll typically release one or two when it's time to go in.
As far as locations, I like exploring many areas. I'm always moving around. Halibut can be anywhere throughout the bay. The more famous places to catch halibut are also full of more people trying to catch halibut, so locations evolve. Halibut also tend to be in different areas and different depths at different times of the year. Think logically about where halibut may be and why, then explore those areas.
There are some places I've heard are good that I've worked hard and never caught a single halibut. Other times I don't over think it so much and get lucky. Other times I move on from where I thought I might catch big halibut only to read later that someone else caught the monster I was looking for, in exactly the same spot, LOL.
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http://www.bigwatersedge.com/bwevb/s...hlight=halibut)
For me, there is a lot of randomness to what happens or not, so I keep exploring new ideas and places. Soon I will be an expert on all the things not to do, and I get better at that every time I go fishing
If there is some secret formula for catching big halibut every time I go out, I don't know what it is. For me, it's more a matter of time spent on the water, steady diligent work, increasing my chances in any way I can, learning from my mistakes, then being patient and waiting for the numbers to work themselves out.
I'm not avoiding your questions. I'm trying to be honest based on my own experience. More than a few fishermen have been known to embellish their stories of prowess as halibut slayers, so I take that with a grain of salt. So should you take my unqualified advice too.
So in summary, I can say this with specificity: I don't know
Have fun, and good luck!