Mechanics of the Kona Coastline

A detailed case study of the Kona fishery.
Will James
Kona, Hawaii, offers a perfect location to target big fish in typically calm seas. This case study explains how weather conditions, topography and currents come together to create a legendary fishing spot. Image courtesy of Hawaii Mapping Research Group.
Located on the western side of the big island of Hawaii, the Kona coastline stretches 60 miles from the Kona Airport in the north to the ancient Hawaiian fishing village of Miloli'i in the South. Image courtesy of Hawaii Mapping Research Group.
This Buoyweather High Resolution Wind Chart clearly shows the wind shadow created by Mount Hualalai, Mauna Loa and Mauna Kea. This wind shadow extends well offshore and results in 300-plus days of flat-calm fishing conditions along the Kona coastline.
Kona is known as the birthplace of the modern trolling lure. Plungers, lungers, bullets and straight runners have all been fine-tuned thanks to the remarkably consistent conditions present year-round off Kona.
Offshore eddies dictate the productivity of the Kona fishery. Strong currents pushing onto Kona's ledges stack up small organisms such as pelagic shrimp and baitfish, which in turn attract and hold marlin, tuna, wahoo and mahi. In this image of sea surface height and ocean currents overlayed on FishTrack's cloudfree SST image we can see a large offshore high with clockwise current flow interacting with a nearshore counter-clockwise low located just off Kona's northwest coastline.
When a clockwise eddy (high) is spinning offshore, north-facing ledges such as the "Top Corner" and "Backside" of "the Grounds" off the Kona airport can become especially productive. The currents push water up onto these ledges and the bait and game fish concentrate in that area.
Skipjack tuna and shearwaters can often be seen feeding on small fish and crustaceans attracted to these localized upwellings.
When baitfish such as skipjack tuna gather in the upwellings, the blue marlin won't be far behind. Both live-baiting and trolling are effective ways to catch blue marlin off the Grounds.
The area north of Honokohau harbor known as the Grounds is actually made up of several distinct areas. The Backside Grounds produces best when the current is running north to south. The Top Corner is also productive on a north to south current. The Middle Grounds is characterized by a pocket in the ledge which is productive on a south-to-north current along with the First Grounds which is also productive on a south-to-north current. Image courtesy of Hawaii Mapping Research Group
Small, localized eddies such as this one centered just northwest of the Grounds will also produce. Visible on FishTrack's MODIS Chlorophyll Image, the center of this eddy can be seen as a light-blue area. Spinning in a counter-clockwise direction, this eddy is pushing water directly up and onto the ledges that make up the Middle Grounds.
This image of currents and altimetry overlayed on FishTrack's Cloudfree SST Image show a low-water event (low altimetry) directly off the Kona coast producing a northerly current along the coast.
Schools of spinner dolphin found offshore will hold large tuna all year. The dolphin and tuna hunt together with the dolphins herding the bait from the sides and the tuna pushing bait up from below.
Schools of dolphin (locally known as porpoise schools) can be found in the 1,000-1,500 fathom zone offshore. There are generally two distinct schools of dolphin (although the schools can intermingle and come together). The North School, usually found off Kaiwi to Kealakekua, and the South School which can often be spotted from Kealakekua to Miloli'i.Spinner dolphin jump, spin and splash so you can often see them from miles away
The green stick method of fishing is an extremely effective way to target tuna travelling with the porpoise schools. The green stick also has another advantage -- it allows a fisherman to keep up with the dolphin school as they move up and down the coast. Learn more about green stick fishing . Photo by KJ Robinson.
Another very effective way of catching tuna in the porpoise schools is to race ahead of the school and employ the Maki Dogu technique. Drop a bag full of chum with one piece of bait attached to a circle hook down to the depth where tuna are being marked. Then pop the bag open at the specific depth, and you might just land a large tuna.
Fishing can slow down a little bit during the winter months, but this is also the time of the year when you are most likely to catch striped marlin and shortbill spearfish. Humpback whales are almost always present during the winter as well.
Regardless of the season, you never know when a big marlin will pop up behind the boat. Grander marlin over 1,000 pounds have been weighed every month of the year in Kona. Check out the latest Kona fishing reports on FishTrack's fishing reports page

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