GLADSTONE BARRAMUNDI END OF SEASON REVIEW 2017

There were 11 forecasts made for Barramundi in size of fish, catch rates, trends in stocks, recruitment and commercial catch. Catch details are based on the top 20% of fishers (T20) 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 year. Forecasts are available at www.crystal-bowl.com.au.

Season 2017 forecasts versus actual – end-season review Nov 2017

T20 Fishers

  • Of the 10 forecasts for T20 fishers 9 were within the forecast range or within 10% of the forecast range
  • Catch details were collected from 50 fishers for 194 fisher days
  • Initial forecasts for size range of fish were affected by fish spilling from Lake Awoonga in Apr 2017 however there was no change made to the forecast
  • Catch rates were on track as forecast until fish spilled from Awoonga and forecasts were revised upward to take account of this influx of fish
  • Forecast was for poor/moderate recruitment and was assessed as poor with little evidence of 2017 recruits
  • The trend in stock levels was downward until fish spilled from Awoonga and that was revised to upward as a result, however it has not been possible to assess the overall effect on stocks
  • Fish that spilled from Awoonga were largely confined to the Boyne River with little evidence of these fish in Gladstone Harbour or the Calliope River
  • In the last 10 years there have been 2.43 million Barramundi fingerlings mostly from 30-70mm stocked into Lake Awoonga with 191k added in 2017

Commercial Fishers

  • Complete catches are only available to 2016 while data for 2017 is incomplete (Feb-Jun) and will be updated when complete data are available
  • There were no forecasts made for commercial effort in 2017 due to the uncertainty in effort shift resulting from the introduction of the Capricornia Net Free Zone
  • Commercial effort increased by 51% in 2016 compared with 2015
  • The increase in commercial effort is likely to reflect some of the effort displaced from the Capricornia Net Free Zone

Environmental conditions

  • Dry conditions largely persisted through to Apr 2017 resulting in poor conditions for recruitment
  • The remnants of Cyclone Debbie brought flooding to much of coastal Central Queensland and Awoonga dam spilled over a 30 day period in Apr 2017 with fish leaving the lake
  • Awoonga dam spilled again in Oct 2017 however the effects of this will not be known until the 2018 season
  • There was flooding in the Calliope River in Apr 2017 and minor flooding again in Oct 2017

Infofish Australia
Nov 2017

MEASURE FORECAST

ACTUAL

GRAPH

GLADSTONE 2017 Season

Nov 2017

T20 fishers
Fisher days
2008-2017
new measure
2017 T20 fishers
Fisher days
194
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Fish sizes
Undersize fish 200-579mm
Legal - trophy fish 580-999mm
Trophy fish >1m


25% (15-35%)
70% (65-85%)
5% (0-15%)



35.7%
52.9%
11.3%

Outside 10% of forecast range

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Percentage of fish in size ranges
Highest Lowest
LEGAL TROPHY
2013 2009
72.9 27.6
TROPHY
2008 2009
13.6 1.1
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Average length of fish 2008-2017

Fish/tagger/day
Highest Lowest
2015 2009
755 524
From 2016-2017
6.5%
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Actual catch rates
T20 fishers
Fish/fisher/day
Overall
2.0 (1.8-2.2)
Legal fish
1.5 (1.3-1.7)

Overall
2.2%
Legal fish
1.7%

Within range

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Catch rates percentage change compared with 2016
Overall
+50% (+30-+70%)
Legal fish
+50% (+30-+70%)

Overall
+60.9%
Legal fish
+77.1%

Within 10% of forecast range

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Actual catch rates
T20 fishers
Fish/fisher/day

Highest Lowest
All
2012 2008
3.4 0.6
Legal
2013 2009
2.5 0.2
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Barramundi tags in Gladstone indicator of trends in stock
Most likely and range
Tagged fish 2017
(Jan-Dec)
400 (300-500)



Tagged fish 2017
(Jan-Oct)
418
Compared with 2016
+ 230%
Within range
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Recruitment
Recruits/fisher/day
Poor/Moderate
0.1 (0.05-0.15)


Poor
0.03

Within 10% of forecast range

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Gladstone Harbour and Barramundi
Low numbers of trophy fish
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Calliope River flow and Barramundi
Low numbers of trophy fish
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Barramundi fingerlings
(~30-70mm)
stocked in Awoonga

Total stocked
2008-2017
2,428,230
Stocked
2017
191,167
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Barramundi tagged and stocked in Awoonga
2008-2017
new measure
Tagged fish
2016
794
2017
1696
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Awoonga dam levels
2008-2017
new measure
Dam spilled
Jan-Mar 2015
Did not spill 2016
Spilled
Apr 2017
Oct 2017
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Boyne River flow and Barramundi
Fish spilled from Awoonga
Jan-Mar 2015
Apr 2017
Oct 2017
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Boyne River Barramundi size range 2017
Size ranges reflect fish spilled from Awoonga
Apr 2017
Oct 2017
n=331
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Commercial effort
Grids S29/S30/S31
Days fished
No forecast
Days 2016
505 (Feb-Oct)
Days 2015-16
+51%
Days 2017
194 (Feb-Jun)
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Commercial catch
Grids S29/S30/S31
Catch (tonnes)
Catch rate (kg/day)
Grids S29/S30/S31
Days fished
No forecast
Catch 2017
(Feb-Jun)
15.5
Catch rate 2017
(Feb-Jun)
79.8
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DATA SOURCES

Data used in the Gladstone Barramundi Crystal Bowl are:

BASIS FOR ANALYSES

The analyses of the data were based on the following:

  • T20 fishers were top 20% of fishers based on Pareto distribution of catch and were primarily taggers
  • Fishing effort for T20 fishers were the number of days fished in map areas CISG, GLD, CR02 and BRG
  • Catch rate for T20 fishers was calculated as fish/fisher/day
  • Catch rate for commercial fishers was calculated as kg/day
  • Stock trends were based on a modeled estimate of the number of tags in maps CISG, GLD, CR02 and BRG each year where the tag reduction rate was calculated based on the reduction of recaptures each year
  • The most likely number of tags was based on a tag reduction rate of 50% each year
  • Recruits were based on tracking recruits over the first year from Jan-Oct with fish in Jan-Feb 0-250mm, Mar-Apr 0-300mm, May-Aug 0-350mm, Sep-Oct 0-400mm
  • Historic data are presented on a 10 year rolling timeframe