Doing the Maths on the Seaway
Part of successful fishing the seaway is knowing where to be at what time. Certain species will start feeding according to tidal and other influences and if you are there then some good fishing can result. With the use of basic formulas we can work out the feeding times for certain species in certain area's and predict certain behaviour.
Firstly and most importantly we need to accurately work out the tides. The official tides are laughably inaccurate in terms of actual tidal flow which as fisherman we are most interested in.
Over to the right we have a single days tides, these are the official tides for the Gold Coast Seaway on Wednesday 30th October 2013. The first column represents times of day, the second represents how big or small the tide is.
To get the actual tide we need to apply some basic mathematics to each value. To get the start of the run in you need to add 1.5 - 2 hours to the bottom of the official tide. In this case the official Low tide is at 10.52am so the start of the run in will be between 12.20pm and 12.50pm. It is impossible to get more accurate than a half hour window as it is determined by the amount of tidal flow on the day. The smaller the tide, the sooner after the official Low tide the water will begin to run in. The larger the tide(around the Full and New moons) the later after the offical Low tide the tide will start to run in.
To get the actual end of the run in tide, the tide will start to slow 15-20 minutes after the official top of the tide(17.03pm) so around 17.20pm it will start to slow and the tide won't start to run out until around 1 hour after the official top of the tide....so around 18.00pm.
To summarise... Add 1.5-2 hours to the official bottom of the tide to get the start of the run-in. Add 1 hour to the official top of the tide to get the start of the run-out. Smaller the tide add less time, bigger the tide add more.
The GT Tide
The GT tide was originally formulated as the perfect tide for GT surface feeding, but it can be applied to all surface feeding fish. Basically it is a tide that begins to run-in in the time between first light and the hour after. This is a good tide is because all the baitfish are pushed out of the seaway on the run-out tide and they hang around the dirty/clean water lines waiting to go back in with the tide. When this happens within the dawn timeframe you have two elements coming together, the dawn bite plus masses of baitfish entering the seaway which usually means some excellent surface fishing action during the dawn period and sometimes the hours after. GT's love it, as do bigeyes and kingfish.
To work out the GT tide you need to add 1.5-2 hours to the bottom of the tide to get the start of the run-in as discussed above. The GT tide usually only happens once or twice every two weeks. Over to our right we have three days which would be suitable for GT tide status. Right now(end of October) first light is at 4am sharp so the Monday tide with a forecast Low at 2.56am should have the tide pushing in at approximately 4.30-5am which is just about perfect. As there is only 30 minutes between the tidal differences on consecutive days you could go a day earlier on the sunday, though I suspect Tuesdays may be a bit too late.
Due to the fact that dawn is at a different time in different season's you need to adjust the time that causes that perfect run-in tide. During winter for example as first light isn't until around 6am, a perfect GT tide woul be one that has an official Low around 4 - 4.30am. Over summer first light is around 3.45am so look for tides with official Low's around 2.30 -3am.
When they are around, Giant Trevally are the most predictable fish in the seaway. Earlier this year using a basic formula I was able to predict within a 30 minute window of when GT's would begin to feed on surface if the tides were suitable. Basically, I would add 2 hours to the official bottom of the tide to get the start of the run-in, then add an hour for the clean water to get to the Canyon. Anywhere within the next half hour after that the GT's would begin to feed on surface.
Over to the right we have a selection of tides I would have picked as ideal for GT's earlier on in the year. Using the formula of adding 3 hours to the official bottom of the tide, the GT's would begin to feed around 7am on Thursday, 8am on Friday and 9am on the Saturday.
You can also use basic formula's to predict when GT's would start taking trolled lures as well, but you need tides as well as time of day. Afternoons tend to work a bit better and the top half of the run-in and first half of the run-out worked the best for trolling and by using a formula of 1.5 hours before sunset you can predict within a 30 minute window of when schooled GT's would take trolled lures. Using both of these formula's I was able to predict GT feeding behaviour and have some excellent sessions.
Bigeye Trevally have been very erratic this year but I have worked out some nocturnal feeding patterns for them around the pipeline, daytime is too erratic to predict. At night you are looking for half an hour after the start of the runout tide. Using the tidal formula above we can deduce that on Saturday the 9th the Official Low tide is 19.35pm. To get the start of the run-out tide we add an hour so around 20.35 plus add another half an hour to an hour for the fish to get organised. So they would start to feed anywhere between 21.00pm and 21.30pm.
Tarpon had similar behaviour to the Bigeye Trevally but in different locations and on both the run-in and run-out tides. By adding 30 minutes to an hour to the start of the actual run-in and run-out tides I could predict within a certain time frame of when they would begin to feed. The main difference between the Bigeyes and Tarpon is that the Tarpon moved around alot more so you still had to find them even though you had a fairly accurate window of when they would begin to feed.
Mulloway are a very predictable fish, they mainly feed when the tide is slowing down or speeding up. So using the tidal formula we know that Mulloway will feed around 1.5-2 hours after the official bottom of the tide, just as that tide starts to push in the seaway. They will also feed at the top end of the tide just as the tide starts to slow, so I would start fishing just before the official top of the tide to get the time when the tide begins to slow. The start of the run-out is also a feeding time for them so add 1 hour after the official top of the tide to get the start of the run out and fish for the next hour. Dawn and dusk are also important, if you can coincide Dawn with a slowing or speeding up tide your chances of cathing bigger fish are increased.
Kingfish are very random and it has been hard to work out any patterns or formula's for them. The small ones that have been hanging around the pipe tend to feed best 2 hours after the official top of the tide, but they are easily shut down. The big ones are much too random to get any sort of pattern going.
Obviously if you are constrained by work and family commitments and you can only go fishing on one day out of 7 then you are going to do it tougher than those who can pick and choose the days to fish. By checking the tides and using these formula's on the days you can actually fish, you can make the best of what time you do have on the water. If you do fish a day when none of the tides are right then I recommend just doing a bunch of random stuff in the hope that some odd fish behaviour present's itself. Every now and again you'll come across something worthwhile. Last Decembers 70cm+ GT's feeding well after sunup on the bottom of the run-out for example.