FITZROY RIVER KING THREADFIN FORECAST SEASON 2018

There are a total of 9 forecasts made for King Threadfin in size of fish, catch rates, trends in stocks and recruitment. Catch details are based on T20 fishers that are the top 20% of fishers that catch 80% of the fish. Their catch rates do not reflect the catch rates of the total fishing population however their catches are more sensitive to changes in fish stocks and are comparable from year to ear. Forecasts are available at www.crystal-bowl.com.au.

Season 2018 forecasts

Forecasts for King Threadfin have a moderate level of accuracy due to the limited data available so there is a greater range in some of the forecasts.

Overall Outlook

Stocks to continue to remain steady and historically high with the catch rate for legal fish to remain steady at 0.3-0.7 fish/fisher/day while trophy fish over 1m will feature more strongly in the catch. Recruitment appears to be up on the last 2 years however it will be some time before that can be reliably assessed.

T20 Fishers

  • Most legal-trophy fish will be in the size range 55-75% with trophy fish at 5%-25%
  • Overall catch rates will remain steady for legal fish and rise slightly for trophy fish
  • Catch rates will be slightly up on 2017
  • Stock levels based on numbers of tagged fish forecast to remain steady at historically high levels
  • Recruitment likely to be moderate-strong based on early reports so the number of undersized fish could increase later in the year

Rocky Barra Bounty

  • Forecasts for the Bounty 2018 will be made in Jun 2018 as there are proposed changes to the event that may affect forecasts

Environmental conditions

  • Neutral to slightly La Niña conditions are forecast for the recruitment period (Jan-Apr) with an average wet season with neutral conditions for the remainder of the year
  • Forecast for Fitzroy catchment is a 50-60% chance of exceeding median rainfall from Feb-Apr and conditions to date suggests that forecast is optimistic
  • The relationship between Threadfin recruitment and climate remains uncertain so it is difficult to forecast recruitment with any accuracy

Infofish Australia
January 2018

MEASURE FORECAST

ACTUAL

GRAPH

FITZROY 2017

2017

Fish sizes
Trophy fish >1mLegal - trophy fish 600-999mm
Undersize fish 200-599mm


15% (5-25%)
65% (55-75%)
20% (10-30%)

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Actual catch rates taggers and avid fishers
Fish/fisher/day

Fish/tagger/day

Taggers

Overall
0.6 (0.4-0.8)
Legal fish
0.5 (0.3-0.7)

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Catch rates percentage change compared with 2017

Taggers/avids

Overall
-10-+50%
Legal fish
+10-+50%

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King Threadfin tags in river indicator of trends in stock
Most likely and range
2009-2017
Tagged fish 2018 (Jan-Dec)
400 (300-500)
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Recruitment Moderate/StrongBut highly uncertain
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Climate outlook BOM NINO34
Weak La Niña
Jan - Apr 2018
Neutral
May-Oct 2018
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Rainfall Outlook Feb-Apr 2018 BOM forecast
50-60% chance of exceeding median rainfall
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DATA SOURCES

Data used in the Fitzroy King Threadfin Crystal Bowl are: