FITZROY RIVER BARRAMUNDI REVIEW 2017

There were 10 forecasts made for Barramundi in size of fish, catch rates, trends in stocks and recruitment. 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 8 (80%) were within or within 10% of the forecast range
  • Catch details were collected from 158 fishers for 422 fisher days
  • The catch rate for legal fish was 1.2 fish/fisher/day and exceeded 1.0 for the first time in over 20 years with that result due to the removal of commercial net fishing and strong recruitment from 2013-2015 with those fish now legal size (except for some slow growing fish from 2015)
  • The catch rate for legal fish was 106% higher than in 2016
  • For legal fish caught 25% were kept
  • A Voluntary Code of Practice (VCOP) was introduced in late 2017 with limits of 2 Barramundi between 60-100cm with 97% of fisher days complying with the VCOP for the season
  • Poor recruitment in 2016 and low numbers of 2017 recruits in the second half of the season contributed to the drop in the overall catch rate compared to 2016 (down 25%)
  • The average length of fish was 664mm in 2017 and the highest in the last 10 years and is 16% higher than in 2016
  • Recruitment for 2017 was moderate although there were few recruits reported in the second half of the season and the climate index suggested poor recruitment
  • Low recruit levels in the second half of the season could be due to recruits moving to freshwater areas following the Apr flooding (no evidence to support this except in 12 Mile Creek) or due to cannibalism
  • The lower number of tags reflects the targeting of larger fish, poor recruitment in 2016 and low numbers of 2017 recruits in the second half of the season
  • Overall trend in stock level is a decline from 2016 to 2017
  • For Barramundi stocked above the barrage in Alligator Creek in 2015 7.9% have been recaptured below the barrage and for fish stocked in Deep Creek in 2015 there have been 7.1% recaptured below the barrage

Rocky Barra Bounty

  • Forecasts for the Bounty were made in Sep due to the uncertainty of the effects of flooding in the river in Apr however a flow in Oct did not have the same effect as in 2016
  • The Bounty broke many records including the highest catch rate for legal Barramundi, most numbers of trophy fish and largest average sizes for both Barramundi and King Threadfin

Environmental conditions

  • There was a moderate flow in the river in Jan 2017 and then a major flood in Apr 2017
  • There was a further flow in Oct 2017 that may affect spawning and recruitment in 2018
Infofish Australia
November 2017
MEASURE FORECAST

ACTUAL

GRAPH

FITZROY 2017 SEASON

OCT 2017

T20 fishers
Bounty fishers
Days fished
2008-2017
New measure

-

T20 fishers Days
158 422
Bounty Days
174 522
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Fish sizes
Undersize fish 200-579mm
Legal - trophy fish 580-999mm
Trophy fish >1m

T20 fishers
40% (30-50%)
55% (45-65%)
5% (0-15%)



T20 fishers Days
34.3% 24.3%
62.8% 72.9%
2.9% 2.9%
T20 within range
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Percentage of fish in size ranges
T20 fishers
2008-2017
-
Highest Lowest
Legal
2017 2009
62.8% 4.2%
Trophy
2017 2010
2.9% 0.1%
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Average length of fish
T20 fishers
2008-2017

-

Highest Lowest
Legal
2017 2009
644mm 396mm
from 2016-2017
+16.4%
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Percentage of legal fish kept
T20 fishers
New measure

-

T20 days
422
Kept
25%
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Percentage of fisher days compliant with VCOP
T20 fishers
2 fish 60-100cm
New measure
-
T20 days
422
VCOP compliant
97%
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Actual catch rates
T20 fishers
Fish/fisher/day
T20 fishers
Overall
2.5 (2.3-2.7)
Legal fish
1.2 (1.0-1.4)


T20 fishers
Overall
1.9
Legal fish
1.2
Over 10% outside forecast range
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Catch rates percentage change compared with 2016
T20 fishers
Fish/fisher/day
T20 fishers
Overall
0% (-10-+10%)
Legal fish
+100% (90-110%)


T20 fishers
Overall
-24.2%
Legal fish
+106.2%
Over 10% outside forecast range
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Catch rates by month
2015-2017
T20 fishers
Fish/fisher/day
new measure
-
Highest Lowest
Overall
Mar 16 Jul 17
5.0 1.4
Legal
Feb 17 Oct 15
1.5 0.2
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Actual catch rates
T20 fishers
Fish/fisher/day
2008-2017
-
Highest Lowest
ALL
2008 2013
6.85 2.2
LEGAL
2017 2009
1.3 0.1
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Barramundi tags in river indicator of trends in stock
Most likely and range
2008-2017

Tagged fish 2017
(Jan-Dec)
1,100 (800-1,300)

Tagged fish 2017
(Jan-Oct)
1,158
Within range
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Recruitment
Recruits/fisher/day
2008-2017

Moderate
(Jan-Oct)
1.5 (1.0-2.0)

Moderate
(Jan-Oct)
1.8
Within range
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Recruits over the recruitment period Jan-Oct
2013-2017
new measure

- Low numbers of recruits in second half of season
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12 Mile recruitment benchmark site
2008-2017
Moderate
(Jan-Oct)
200 (150-250)

Moderate
(Jan-Oct)
188
Within range
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Stocked fish above barrage
Recaptured in estuary
2012-2017
New measure
-
Alligator Ck
2015 7.9%
Deep Creek
2015 7.1%
Yeppen Lagoon
2015 3.6%
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Stocked fish Alligator Creek 2013-2015
Growth
New measure

New measure
- Fish recaptured in Fitzroy estuary
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Commercial catch
Grids R29 and R30
Catch tonnes
Catch rate kg/day
2008-2017
None forecast as river is now a net free zone
Catch
2015
85.61t
Catch rate
93.3kg/day
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River flow and Barramundi 2016-2017
- Moderate flow in Jan and major flood in Apr have affected catch rates and numbers tagged
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River flow and Barramundi 2008-2017
-
Floods
2008
2011
2013
2015
2017
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DATA SOURCES

Data used in the Fitzroy Barramundi Crystal Bowl are:

 

BASIS FOR ANALYSES

In 2017 saltwater tidal maps (FRR, PAR, CIS) and freshwater maps (RAG, FRF) were separated so that data could be analysed for the different habitats. The analyses of the data were based on the following:

  • T20 fishers were top 20% of fishers based on Pareto distribution of catch in the Fitzroy River
  • Fishing effort for T20 fishers were the number of days fished in map areas FRR, PAR and CIS
  • Catch rate for T20 fishers was calculated as fish/fisher/day
  • Catch rate for commercial fishers was calculated as kg/day
  • Compliance with VCOP based on 2 Barramundi per person/day from 60-100cm
  • Stock trends were based on a modeled estimate of the number of tags in all maps 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 0.5 each year up to 2015 and 0.4 from 2016 considering no commercial catch
  • 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