Tuna fishery potential

Tuna fishery potential

It’s hard to beat a tuna for pure excitement during that first screaming run, along with great power and endurance afterwards, yet recreational anglers are currently missing out on two fantastic opportunities that occur over winter and spring. In this instance I’m referring to the winter run of huge albacore tuna found off the Bay of Plenty between late July and the end of September, and the rather unique bigeye tuna fishery that occurs off the Mercury Bay region from about mid-October.

This feature concentrates on the big albacore that run to more than 25 kilos and generally visit Bay of Plenty waters in September – which is why most game fishermen miss out. Having said that, the Tauranga Sport Fishing Club hosts an annual tournament specifically targeting them in September – a great idea, as chasing albacore on light tackle can provide really worthwhile challenges. (If reports from Tony Walker are anything to go by, I wouldn’t be surprised if Bay of Plenty and Mercury Bay fishers establish a new bigeye tuna fishery in the process, But more on that later…)

My first serious attempt at catching big, winter-run albacore was aboard the Tauranga-based charter vessel Pasador during the 1998-1999 season. Back then we had a reliable area that fished well from mid to late September – and it fishes well to this day for large numbers of albacore between 20 and 25 kilos.

The first run of albacore tuna that enter the Bay of Plenty fishery are by far the biggest. Averaging between 15 and 25 kilos, the commercial long-liners regularly nail specimens between 30 and 35 kilos, which tend to be found out a lot deeper and wider off Mayor and White Island.

This time last year, tuna long-line fisherman caught albacore tuna to 40 kilos whilst targeting southern bluefin tuna off East Cape, and last week I also heard a report on our local Newstalk ZB fishing show from Rick Pollock, who operates the charter boat Pursuit out of Whakatane, saying a surface long-liner had caught a 50-kilo specimen off White Island!

It just goes to show how much we have yet to explore out there.

As the water temperature warms up a little, reaching 15.8-16.5 degrees, these big albacore start moving into the area. Traditionally, albacore follow a northeast-southeast migration pattern, swimming down into the western Bay of Plenty and Mercury Bay region via the 2000-metre line during August. They then follow the currents and head inshore during September on the 1000-metre line between the Alderman Islands and Mayor Island.

At this time there are usually tonnes of krill and plankton out there, as indicated by the sooty shearwaters. It is a surefire thing that the Mayor Island Knolls, the Penguin Shoals, and out at the back of Plate Island on the 200-metre line, will have 15-25kg fish somewhere in the vicinity.

Albacore tuna are highly pelagic. They seek open, clear water, and the aim of the game is to find areas with the highest concentration of chlorophyll (phytoplankton) blooms.

Chlorophyll blooms tend to form along temperature/current breaks where two bodies of water are in close proximity to one another. There will be cooler, nutrient-rich water on one side and warmer, clearer water on the other. These breaks also tend to extend vertically deep into the water column, forming a barrier into which albacore tuna, bigeye and southern bluefin tuna push baitfish. That’s why tuna long-line fishermen stay alert for temperature breaks – find the breaks and find the various tuna species being targeted.

To successfully find the chlorophyll blooms, it’s important to pay attention to what the currents are doing over a period of a few days or more.

Sea surface temperature and chlorophyll charts provide great ways to get started, with websites such as FishTrack.com updating the latest satellite imagery several times daily. (Commercial tuna fishermen throughout the Pacific already use SST charts to chase albacore and bigeye tuna, so it’s nothing new to them.)

For many recreational game-fishers, using satellite imagery to identify prime fishing locations is a bit of a challenge. However, once you have a basic understanding of what you are looking at, it’s actually not that hard to interpret. (I wouldn’t be at all surprised if the top game boats here in New Zealand use them, but if they do, they certainly keep very quiet about it!)

So, what is chlorophyll, and how do you use it to find tuna? Chlorophyll is the green stuff found in plants, algae and even in tiny little micro-organisms in our oceans called plankton. Plankton provides the foundation to the ocean’s food chain, and most krill and small baitfish eat it.

By looking at the chlorophyll charts, you are basically looking for plankton blooms in your fishing area – the start of the food chain. So, if blooms stay in your fishing area for several days, a food chain will develop, with the krill and small baitfish turning up and eating the plankton, which are then eaten by bigger predators and so on. By looking at the chart of Waihau Bay, you will see what chlorophyll indications look like. Areas of warmer, clearer water appear as blue, while areas of colder, nutrient-rich water appear as green, due to the high concentrations of plankton. Baitfish concentrations, including squid, will likely be found where these two bodies of water meet, especially along the leading edges. The tuna will also concentrate here over several days or more, providing the currents don’t push the concentrations out again.

If you take note of the chlorophyll reading at the top left of the picture, you will notice it reads 0.55. This measurement indicates plankton concentrations at milligrams per cubic metre. Look at where the cursor is set – smack-bang in the greener water, which has a high level of chlorophyll. This is where the plankton bloom is located, along with the albacore and southern bluefin tuna attracted by the smorgasbord on offer.

The best combination for finding tuna and the like off Waihau Bay, for example, is to find where the clearer, bluer water meets more greeny water with a high level of plankton. You can apply this to your own fishing area anywhere in New Zealand.

(The above is only a brief description of one way to find tuna; in a future edition of the magazine I will expand on the interpretation of sea-surface temperature charts, temperature breaks, sea-surface height anomalies, chlorophyll charts, as well as the currents and the tides from a commercial tuna fisherman’s point of view. This will help you to locate the most productive water and put you ahead of the pack.)

When trying to locate albacore tuna schools, the primary aim involves seeking out any seabird or seal activity and then sticking with it.

Fishing out wide off Tauranga, you will often encounter heaps of sooty shearwaters on top of the knolls and seamounts. Locate these birds and you are in the right zone.

The area may look dead, but when you watch hundreds of birds poking their little heads below the water, it generally means the baitfish are being herded by the tuna down deep. From my experience, it will be either albacore or bluefin harassing the baitfish, and if seals are present, then more often than not it will be bluefin. However, as winter turns to spring, the tuna could easily be bigeye, as they start to show up on the knolls and seamounts east of Whitianga in October.

On most of the offshore knolls off Mayor Island, you will get seals and seabirds working the area together, with tuna not far behind them. In such situations, deep down, where you can’t see anything, albacore will usually be herding the baitfish into small baitfish balls, occasionally pushing them up towards the surface where the seabirds are ready to pounce.

If an area looks this fishy, you have to work the area and stick with it; the albacore tuna around the Mayor Island knolls tend to feed sporadically.

If, like me, you are considering having a crack at these large albacore tuna this month, here are a few pointers to get you underway.

Always check the weather. Albacore often bite like crazy when there is a bit of chop on the water; we have the most success on days when it is overcast and a bit lumpy.

Watch for that that magical water temperature of 15.8–16.4 degrees. If you don’t have access to a sea-surface temperature chart, then find someone who does.

Winter albacore will be found swimming in tight vertical packs on the edges of the temperature and chlorophyll breaks; a slick of warm water running across underwater structure is a key indicator they may well be present.

Albacore tend to be found on the leading edges where cooler water pushes up against warmer water. For example, if trolling in 15-degree water and it suddenly increases to 16 degrees, that is the temperature break. Work the area by zigzagging in and out, or trolling along the edge of it.

Traditionally, areas such as the waters beyond Astrolabe Reef, Penguin Shoals and the Mayor Island Knolls hold 20- to 25-kilo albacore from time to time, as these areas also accommodate good concentrations of squid.

Use straight-running lures – you don’t want lures that duck and dive all over the place. The big albacore don’t seem particularly interested in big marlin lures producing big bubble trails. Instead, invest heavily in bullet-head lures. (Most of the tournament-winning fish have fallen victim to hex-heads and small feathered lures such as the Black Magic and MacSkippy ranges of lures.)

So, there you have it – just a little bit of a teaser to showcase another winter fishery available to well-prepared fishers keen for some game-fishing action before the traditional target species, marlin, arrives. And, of course, there are bigeye tuna, but this species is the subject of a future feature…

   This article is reproduced with permission of   
New Zealand Fishing News

September 2017 - Ben Carey
Re-publishing elsewhere is prohibited

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