DALY RIVER BARRAMUNDI 2007-2016

An assessment was made of available data for the Daly River using data from all available sources including the Barra Classic and Barra Nationals fishing competitions and from monitoring undertaken by Northern Territory Fisheries from 2000-2016. Based on that assessment a Crystal Bowl has been set up based on data from 2007-2016.

Summary

  • For the Barra Classic effort has increased steadily while catches have remained low since 2013
  • For the Barra Classic the trend in the overall catch rate and catch rate for legal fish has declined slightly over time and catch rates were low from 2013-2016
  • The catch rates for the Barra Nationals for the 2 years of data are comparable to the Classic
  • Number of fish tagged in the Classic peaked in 2011 at 1711 and was the lowest in 2013 at 214
  • The average length of fish in the Classic has remained steady and ranged from 628mm in 2011 to 541mm in 2012
  • Stock levels are likely to have fallen since 2012, based on a modeled estimate of the number of Barra Classic tags in the river, with low/moderate recruitment not making up for fishing and natural mortality
  • Recruitment was highest in 2011 and significantly higher than any other year with reasonable recruitment in 2014
  • There is a correlation between river flows from Dec-Feb and the number of recruits although data for 2008 and 2009 do not fit well given that 2011 saw the highest number of fish tagged which would require strong recruitment in those years and that is supported by river flows

Environmental conditions and Outlook

  • Flows in Jan-Feb 2016 in the river were within the timeframe and range for above average recruitment and that should be reflected in the 2017 Classic fish – NT Fisheries monitoring suggests reasonable recruitment
  • BOM ENSO outlook based on POAMA NINO 34 is for neutral conditions for the early part of 2017 tending towards El Niño in the second half of the year
  • BOM forecasts for Jan-Mar 2017 are for a 55-60% chance of above median rainfall supporting moderate recruitment

Infofish Australia
January 2017

MEASURE

ACTUAL

GRAPH

DALY RIVER BARRAMUNDI
Classic catch and effort
number of fish
fisher days

Highest  Lowest
CATCH
2011    2013
1711    214

EFFORT
2016    2007 810    670

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Nationals catch and effort
number of fish
fisher days

Data only available for 2015-2016

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Classic catch rates
fish 400mm+
legal fish 550mm+
fish/fisher/day

Highest  Lowest
ALL
2011    2013
2.24    0.29

LEGAL
2011    2013
1.67    0.10

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National catch rates
fish 400mm+
legal fish 550mm+
fish/fisher/day

Data only available for 2015-2016

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Classic
average length mm
and size range

Highest   Lowest
2006nbsp;  2012
628mm   541mm

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Classic percentage sizes
undersize <550mm
legal-trophy 550-999mm
trophy 1000mm+

Highest   Lowest
LEGAL-TROPHY
2011   2013
74.1%   31.3%

2013   2012
4.3   0.1
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Nationals
average length mm
and size range

Data only available for 2015-2016

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Nationals percentage sizes
undersize <550mm
legal-trophy 550-999mm
trophy 1000mm+

Data only available for 2015-2016

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Competition catch rates
fish 400mm+
Barra Classic
Barra Nationals
Rocky Barra Bounty
(Fitzroy River Qld)

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Competition catch rates
fish 550mm+ (NT legal)
Barra Classic
Barra Nationals
Rocky Barra Bounty
(Fitzroy River Qld)

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Stock trends based on model of Classic tags
Estimate of tags in river each year

Stock levels have trended down since 2012
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Timeline of Barramundi tagged and river flows

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Recruitment using Classic year 2 fish 350-450mm
number of recruits
river flow Dec-Feb

GOOD RECRUITMENT
2011 2014
POOR RECRUITMENT
2012 2013 2015?
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Barramundi tags in Google Earth map grids
(based on limited data where locations were able to be plotted at grid scale)

Available from INF_KML_405.3.KML
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River flow and rainfall NINO34 forecast is for neutral conditions for 2017
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Rainfall outlook
Jan-Mar 2017
BOM forecast is for 55-60% chance of exceeding median rainfall
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DATA SOURCES

Data used in the Brisbane River King Threadfin Crystal Bowl are:

BASIS FOR THE ANALYSIS

The analyses of the data were based on the following:

  • Tag data were available for all years from the Barra Classic however there are no tag records for the last day of the Classic in 2015 – 17/5/2015
  • Catch data are only available for 2015-16 for the Barra Nationals (back years’ data may still be provided)
  • Recruitment has been assessed using Classic fish from 350-450mm as recruits in year 2 however only fish over 400mm were generally tagged and the data have not been adjusted for effort so that reduces the reliability of the recruitment data
  • A model has been developed for estimating the number of tags in the river at the end of each year based on the rate of loss of tags each year from recaptures (the rate of tag loss for the Daly is very similar to that for the Fitzroy River in Qld)
  • Where locations have been able to be plotted at the grid scale (2kmx2km) a Google Map has been prepared showing the number and size range of fish tagged in each grid