INTRODUCTION

The records of the LIGFC and AIMS’ physical data have enabled a thorough look at the activity of black marlin in relation to diurnal, tidal and lunar cycles and other factors.

The annual tally of Strikes (red), Hookups (yellow) and Tags (green) over the past 9 years of the Lizard Island Black Marlin Classic indicate that the fleet encountered particularly good fishing in 1991, 1992 and 1994. For reference, the Southern Oscillation Index (SOI) to October, 1999 is displayed (upper plot).

This graph does not include any information on the number of boats involved in achieving the displayed results. 

When hookup times are adjusted relative to the tidal cycle, and account taken of the variations in effort (number of boats fishing) at all stages of the tide, better than average results are achieved on a making tide. A typical tidal cycle is indicated and the bars indicate better than (above the line) and worse than (below the line) average hookup rates.

The blue line is a typical tidal cycle and the red bars are average hookup rates.

The current meter moored adjacent to Jewel reef provides information on the direction and strength of the East Australian Current (EAC). These data have been resolved into components parallel to the reefs to indicate a northwards or southwards set and drift.

The EAC is an offshoot of the South Equatorial Current and believed to be relevant to the migration of black marlin to the reefal waters of the Great Barrier Reef. The EAC is not constant and, in particular, can be influenced by the SE trade winds. To date, there is no evidence of a direct relationship between the EAC and black marlin activity as represented in the LIGFC data.

The plots on the right indicate water movement in a northerly (above the line) or southerly (below the line) direction. The month of October is shown for the nominated years and the week of the tournament is shaded yellow. Rates of up to 0.7 knots are indicated.

While the SE trades are a fact of life at these latitudes over the winter months, they are more variable during the fishing season. 

This graph, utilising data from the Agincourt Reef weather station, indicates that a boat’s average daily strike rate improves as the wind picks up from the south.

Wind speed (km/hr)

With access to the precise time of hookup, the activity throughout a typical day’s fishing can be displayed. With regard only to time of day, the fishing appears to improve through to lunch time and then remain relatively constant throughout the afternoon. In reality, competitors do not start fishing at the same time and the fleet is not fully engaged until about midday. 

Therefore, this data would indicate that black marlin can be caught, in similar numbers, at all times of the day between 10:30 and 17:30.

The moon has a lot to do with cycles in activity in fish – ask any fisherman. Over the years, the Lizard Island Black Marlin Classic has seen strike rates improve over the first quarter and leading up to the new moon. The horizontal axis indicates the lunar cycle and better than average strike rates above the line. The club has avoided scheduling tournaments over the full moon and the data indicates poor fishing either side of this no fishing period.

If you refer to the graphs displaying strikes, hookups and tags, it is evident that 3 strikes will produce 2 hookups with 1 fish tagged. When moon phase is considered, a better result is obtained at those times when strike rates are better. The bars above the line represent better than average hookup rates.

Strike rates improve over the first quarter and leading into the dark moon. Bars above the line represent better than average strike rates.

The likelihood of hooking up after getting a strike from a Black Marlin appears to improve slightly over the first quarter and the dark moon. Bars above the line represent better than average hookup rates.