FITZROY RIVER BARRAMUNDI MID SEASON REVIEW 2017

There was a total of 10 forecasts made for Barramundi in size of fish, catch rates, trends in stocks and recruitment. Taggers/avid fishers catch rates do not reflect the catch rates of the total fishing population however as they are generally in the top 20% of fishers that catch most fish and 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 – mid-season June 2017 review

Taggers/Avids

  • Of the forecasts for taggers/avids 6 (60%) are within the forecast range or within 10% of the forecast range and forecasts remain unchanged
  • Poor recruitment in 2016 has contributed to the slight drop in the overall catch rate compared to 2016
  • The catch rate for legal fish has exceeded 1.0 fish/fisher/day for the time in over 20 years and is the result of 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 is 122.8% higher that in 2016
  • The average length of fish is 671mm in 2017 and the highest in the last 10 years and is 19.8% higher than in 2016
  • The low number of tags so far reflects the targeting of larger fish and poor recruitment in 2016 however numbers are expected to pick up in the second half of the season due to strong recruitment in 2017 (those fish are now 200-300mm and able to be tagged)
  • Moderate flow in Jan and flooding in Apr has also impacted on the numbers of fish tagged
  • Forecast was for moderate recruitment with early indications for strong recruitment however that is expected to ease back to moderate/strong as the season progresses

Rocky Barra Bounty

  • Forecasts for the Bounty will be made in Sep due to the uncertainty from flooding in the river in Apr

Environmental conditions

  • There was a moderate flow in the river in Jan 2017 and then a major flood in Apr 2017
  • Climate outlook is for neutral conditions through to Feb 2018
  • Rainfall forecasts are only available for 3 months and the forecast is for a 45-55% chance of exceeding median rainfall from Jun-Aug

Infofish Australia
June 2017

MEASURE FORECAST

ACTUAL

GRAPH

FITZROY 2017

Jun 2017

Fish sizes
Undersize fish 200-579mm
Legal - trophy fish 580-999mm
Trophy fish >1m


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

Taggers/Bounty
31.0%
65.3%
3.7%

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Percentage of fish in size ranges
2008-2017

Highest  Lowest
LEGAL-TROPHY
2017    2009
65.3    2.5

TROPHY
2017    2010
3.7    0.1

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Average length of fish 2008-2017

Fish/tagger/day
 

Highest   Lowest
2017   2009
671mm   383mm
increase 19.8% from 2016-2017

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

Fish/tagger/day

Taggers/Bounty

Overall
2.5 (2.3-2.7)
Legal fish
0.75 (0.6-0.9)
Legal revised 1.2 (1.0-1.4)

Taggers/Bounty

Overall
2.2
Legal fish
1.3

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Catch rates percentage change compared with 2016
Fish/fisher/day

Taggers/avids

Overall
0% (-10-+10%)
Legal fish
+30% (20-40%)    -160-180
Legal revised
+100% (90-110%)

Taggers/avids

Overall
-13.1%
Legal fish
+122.8%

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Catch rates by month
2015-2017
Fish/fisher/day
new measure
Highest   Lowest
Overall
MAR 16    APR 16
5.0    1.5
Legal
FEB 17    OCT 15
1.5    0.2
Tagged fish 2016 (Jan-Dec)
1,191
-15% compared with 2015
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Actual catch rates taggers and avid 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
2009-2017
Tagged fish 2017 (Jan-Dec)
1,500 (1,200-1,800)
Revised
1,100 (800-1,300)
Tagged fish 2017 (Jan-May)
312
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Recruitment
Recruits/fisher/day
2008-2017
Moderate
(Jan-Oct)
1.5 (1.0-2.0)
Revised
3.0 (2.5-3.5)
mod-strong
Strong
(Jan-May)
3.0
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12 Mile recruitment benchmark site Moderate
100 (50-150)
Revised
mod-strong
200 (150-250)
Moderate
150
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Commercial catchGrids R29 and R30
Catch tonnes
Catch rate kg/day
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 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 2007-2016 Floods
2008
2011
2013
2015
2017
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Climate outlook to Feb 2018 BOM NINO34 Neutral conditions through to Feb 2018
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Rainfall Outlook to Jun-Aug 2017 BOM forecast 45-55% chance of exceeding median rainfall
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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:
  • Effort data for taggers/avids were the number of days fished in map areas FRR, PAR and CIS
  • Catch rates for taggers was calculated as fish/fisher/day
  • Catch rates for commercial fishers was calculated as kg/day
  • 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
  • In 2016 recruits fish in Jan-Feb 0-200mm, Mar-Apr 0-250mm, May-Aug 0-300mm, Sep-Oct 0-350mm