The following data came
from a couple of local fishing books and reports from the
Western Pacific Regional Fishery Management Council but, one thing you should know is that fish don't
know how to read calendars. 
Like party guests, they don't always show up
when they should and sometimes they still hang around when they're supposed to
leave. The best fisherman in Kona will alter their target species with what will
give you the best chance of a successful fishing day. I have the best catch rate
of any charter captain in Kona every year since 1997 by doing it this way! 
If I'm
already booked up, I refer captains/boats that have a higher than average catch
rate.
Further explanation: Kona is the Pacific blue marlin capital of the world. At times (not determined by a calendar) marlin are one of the most common daily catches here. The yearly average of a good charter boat that is solely dedicated to trolling all day is to catch just under 1 marlin in every 4 days. The way this yearly average works can be misleading. When the Kona marlin bite is "on", you might catch one or more daily. When the marlin bite is "off", you might not see a marlin for a whole month. The "average" is based on the number of marlin caught in a year divided by the number of days fished. Multiple marlin caught in a single day brings that yearly average up. A good blue marlin run can happen for a short period of time in any month of the year. The Striped marlin are here in the winter (not always) and are a rare catch in the summer months but not unheard of. Black marlin are rare with less than 20 caught a year here. Sailfish are rare too but do show up from time to time. Spearfish show up in big numbers here and are one of the best eating fish there is. In general, if you plan on trolling for billfish all day, also plan on not catching one. The statistics are not in your favor. Some alnglers have tried for many years and haven't caught one yet. It is a gamble though so first time winners happen all the time.
Mahi mahi (dolphin fish) can be caught year round as can ono (wahoo). Use the chart above for peak season(s) but again, the runs may not happen according to the calendar. In the summer months we normally get "blind strike" yellowfin tuna bites. A 100+ yellowfin can hop on your line any time you're trolling but in the other seasons, blind strikes are rare. Yellowfin tuna commonly travel with the spotted dolphins (called a porpoise school) so any time of year you run into a porpoise school, there's a chance of catching 100+ lb. yellowfin tuna. There are only a few boats in kona that aggressively search out and target the schools. Smaller yellowfin (under 15 lbs.) and small bigeye tuna are common around the fish aggregation buoys (FAD's) in the winter months. Sometimes they come in early and sometimes they stay into the summer months. The "big" bigeye tuna ones are an uncommon catch here. Skipjack tuna are the most common fish we have. At under 10 lbs., they're considered a bait fish. Once they reach the 10+ lb. size, they are called "otado" or "otaru". If properly bled out and iced down, they're a good eating fish. Especially when they reach 20 lbs. or more.
Amberjack, almaco jack and sharks are the most common fish caught near and on the bottom year round. All of these are hard fighting sport fish. Giant trevally (GT) and some other kinds of trevally are a more rare catch. Snapper and grouper are more of a bycatch while going for the bottom fish.
In some areas of the world, tides and moon phases are the most important factor when choosing your fishing day(s). Here in Kona, the current is king! There's no way to predict it. When it runs steady (North or South), the bite is usually good unless it's running too fast. When it switches, the bite drops off. Sometimes we get a split current and it's going South, South of the harbor and North, North of the harbor. Or that split can happen anywhere along the coast line. We only get an average of a 2' tide change here so it's not much of a factor. New moons and full moons can make the bite better but the current often cancels or enhances this effect.
I hope this information is useful to you. You can always check out my fish Photos
Page to see what I've been catching lately and I do the Kona fishing
report monthly, near the end of each month. The page also has a ticker-tape style update that I try to update every week or two.
