Ticking the boxes with TK

by Tony Walker (aka TK) TK Offshore Fishing

Oceanographic data is crucial to finding Sea Surface Temperature (SST). It's a big ocean out there and recreational fisherman have very limited time on the water so they need accurate data to assist them. I call it ticking the boxes, and the more boxes you tick the more chances you have of finding Southern Bluefin Tuna. While SST is the most common data used by recreational fisherman, there are a few more types of meteorological data that I use to help pinpoint the bait aggregations and the old adage is "find the bait, find the tuna".

1. SST has been used by fishermen for a long time and comes from satellite observation, and for that reason it is very accurate and updated daily. You are looking for temperature breaks where the temperature varies quickly, as these fronts act as natural barriers for fish that tend to accumulate or swim along them.

‍2. SSH, or Sea Surface Height anomalies, means the sea surface is not flat! The water level rises and falls according to the water column temperature and other factors. Water which is relatively colder will be heavier than warmer water. This heavier water will cause a difference in height (SSH). High spots in the ocean surface column associated with positive values are usually nutrient-poor waters. Low spots in the ocean water column associated with negative values are nutrient-rich areas and have everything needed to attract food for pelagic fish at the top of the food chain. Many times areas found between high and low spots form "oceanic highways" where fish are most likely to be. The fish like to hunt in the low areas and rest in the high areas. Finding these SSH "fronts” is important for fishermen as tuna often like to cross this border.

‍3. Chlorophyll and phytoplankton. Small fish (bait) like to stay in high concentration areas where the food (microorganisms) can be found. Larger fish like tuna are more likely to be found around the edges of these concentrations. They will hunt in the higher concentrations where the bait is found and then retreat to the low-chlorophyll areas to find "comfort" (better visibility with more oxygen).

4. Currents. Once I have found a likely looking area of SST I look at the currents in the area to fine tune my target area. Currents offshore are not tidal-based, as they are influenced by the SSH anomalies and bottom structure like seamounts and canyons. The currents will determine where the bait concentrations are likely to be. When you have heavy cloud cover you will not get accurate SST data, and most modern weather apps will use predictive technology to predict the movement of the bodies of water while we have heavy cloud cover. The satellites will however still give very accurate data on SSH movements and the currents are associated with the SSH, so if you know where the warm water is in relation to the SSH feature before the clouds roll in you can still track the body of warm water using the SSH and current data.

While I enjoy the benefits of world-leading weather data through my association with Furuno and Timezero this technology is not available to everyone, so there are still techniques we have been using for decades to target tuna that will assist you.

5. Gossip. Check out your social media feeds, talk to your buddies, support your local game-fishing club. These are all great sources of information on where the SBT are biting.

6. Dolphins. Watch for the pods of dolphins and watch their behaviour. Are they frolicking around and riding your bow wave, or are they ignoring you and all travelling in one direction at pace? If they are speeding off in one direction they are hunting

7. Birds. Watch for the birds, as they will indicate where the bait balls are. Watch their behaviour. Are they circling and diving or are they up high searching? If you get dolphins and birds together, stop searching as you have found your tuna.

8. Watch your SST gauge as you are traveling. Any sharp rise or fall in SST is a temperature break and you will find tuna hunting these breaks.

9. Sea surface colour changes. If you see the water change colour from say a deep green to blue this also indicates a temperature or current shear.

10. Flotsam and dunnage. If you see a line of brown water with stuff floating amongst it like seaweed, or rubbish like plastic water bottles (stop and retrieve them from the water), this indicates a current shear and the tuna will be working that line.

Tick these boxes because the more of these indicators you can find the better your chances are of locating the tuna. Goodluck!

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