East Coast SBT Habitat Report
Jason Hartog and Alistair Hobday
AFMA Report 13, October 28, 2014
Summary
The most recent SST composite is from October 26, 2014 and is obtained from the Bureau of Meteorology
(RAMSSA v1.1). This composite product incorporates the SST provided by the Group for High Resolution
Sea Surface Temperature (GHRSST) and illustrates the general ocean situation off eastern Australia (Figure
1). The predicted locations of the SBT habitat from the Habitat Prediction Model are shown in Figure 2.
There have been some small changes since the last report, but mainly in offshore regions. The southern flow
of the EAC has strengthened and rather than flowing into the eddy off the coast of Sydney as in the previous
report (seen as OK habitat in Figure 2), it is flowing offshore creating a large pool of warm water to the north
east of the Sydney eddy (IMOS image and Figure 1). This warm pool of water is seen as OK and buffer
habitat in Figure 2. The anti-cyclonic eddy off the coast of Sydney is drawing in cold water from the south
(Figure 1) and this is seen as core habitat on the eastern side of the feature (Figure 2).
The seasonal SBT habitat forecast suggest the remainder of the season will be a typical year (Figure 4). We
note, however, that in May, when we began the SBT forecasts for the year, that this year was projected by
the BOM and other international modelling groups to be an El Nino year
(http://www.bom.gov.au/climate/enso/). More recent projections are less confident, and suggest more neutral
conditions. Our unpublished analysis shows that movement of the SBT habitat zones, which is significantly
driven by ocean temperatures, is not markedly different in El Nino years.
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East Coast SBT Habitat, AFMA Report
Most Recent SST image
http://oceancurrent.imos.org.au/Syd-Hob/latest.html
The IMOS SST satellite image that was provided in this section in previous reports is no longer provided as
the data generating that image is now incorporated into the full habitat model as part of the RAMSSA v1.1
(Beggs, 2007). The Group for High Resolution Sea Surface Temperature (GHRSST,
https://www.ghrsst.org/) data that is underpinning RAMSSA was sourced from the Integrated Marine
Observing System (IMOS) - IMOS is supported by the Australian Government through the National
Collaborative Research Infrastructure Strategy and the Super Science Initiative.
Model Coverage
For this SBT season, AFMA have requested the model to be run in an “inshore” mode (out to 155°E) and in
“regular” mode (habitat preference extending to 170°E). The shelf region has been blocked with a mask for
distribution to stakeholders. The offshore and inshore climatology are shown in Figure 4. The inshore mode
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East Coast SBT Habitat, AFMA Report
climatology has more variability as it is focusing on the most dynamic part of the EAC, and this variability is
seen in the width of the buffer zone climatology in the winter months when the EAC is retreating and
advancing rapidly.
Seasonal Forecast
Forecasts of the position of the SBT habitat zones using the POAMA (Predictive Ocean Atmosphere Model
for Australia) model (http://poama.bom.gov.au/), developed by Bureau of Meteorology (BoM) is shown in this
report. While POAMA is a coarser resolution model than the one we use for the habitat nowcasts (Figure 2),
the model can provide managers some information about the coming months of SBT habitat distribution. We
have verified the skill of POAMA for this purpose (Hobday et al 2011) and this report provides operational
forecasts for SBT habitat zones out to 5 months (Figure 3). Our published analysis suggests that the skill of
the forecast deteriorates after 3 to 4 months, and so projected habitat locations more than three months into
the future should be interpreted with caution. These projections may help managers and fishers plan their
operations over and above using the climatology alone.
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East Coast SBT Habitat, AFMA Report
Figure 1. High-resolution 3-day composite SST image for the most recent model run. The 200 m depth
contour is also depicted. The image from the previous report is shown below for comparison.
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East Coast SBT Habitat, AFMA Report
Figure 2. Habitat nowcast: Distribution of zones based on percentage distribution of SBT habitat from the habitat prediction model based on Scenario 1 (80%: 15%: 5%). The
image from the previous report is shown to the side for comparison. The 200 m depth segment of the shelf is masked out. The major fishing ports have been added to aid
interpretation.
a) Current Report
b) Previous Report
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East Coast SBT Habitat, AFMA Report
Figure 3: Seasonal forecast: Distribution of zones based on percentage distribution of SBT habitat from the
habitat prediction model using POAMA temperature fields based on Scenario 1 (80%: 15%: 5%). The 200 m
depth segment of the shelf is blacked out. The thick dark line on the current forecast shows a contour
analysis of the operational nowcast core zone. The thick dark line on the 1 to 5 month forecasts shows a
contour analysis of the current forecast to aid understanding of how the core zone will be changing when
compared to the current POAMA forecast. The arrows on the right side of each panel give an indication of
whether the core zone is moving north or south when compared to the previous month’s forecast.
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East Coast SBT Habitat, AFMA Report
Figure 4: Climatology showing the mean position of the buffer zone throughout the year is indicated by the yellow band and is based on an analysis of satellite SST and subsurface temperature from 2009 to 2013 (to 170°E). The blue lines indicate the maximum northerly (5%) and southerly extent (5%) of buffer pixels in any year. For the climatology
the position of the buffer zone is estimated as the upper and lower 5% of buffer pixels in the current year is depicted by the red band. This may not reflect the optimal placement of
the buffer zone, and is intended as a guide to the seasonal movements of the SBT habitat preferences. Scenario 1 is the 80:15:5 habitat division. The red stars show the location
of the core zone in this climatology for the 1 to 5 month forecasts.
a) Regular mode: coast to 170°E
b) Inshore mode: coast to 155°E
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East Coast SBT Habitat, AFMA Report
Methods
The set of predictions of the extent of SBT habitat on the east coast of Australia are based on
analyses of current satellite sea surface temperatures (SST), sub-surface temperatures from a
CSIRO ocean model incorporating satellite sea surface height data and pop-up tag temperature
data for SBT. This model run uses the revised SynTS 3-D ocean product (introduced in 2006)
which has improved depth resolution (more layers to a depth of 200 meters: 25 compared with
17). Surface currents are shown on the surface SST map to aid understanding of the ocean
dynamics. One habitat preference scenario is now used based on “Percent Habitat Distribution”.
This is known as Scenario 1: 80%: 15%: 5% (core zone: buffer zone: ok zone)
Until the middle of July, tag observations within 70 days of the analysis date will be considered
(e.g. May 2 ± 70 days). This restriction changes to 30 days after that date, as in previous years.
The reason for this is that there is limited data in the early part of the year to condition the model.
Thus, the current habitat model is conditioned on a pop-up tag dataset consisting of 71 tags for
the years 2001-2009 (7656 observations at this time of year). As in 2012, we have included data
from SBT tagged in New Zealand, and we acknowledge MFish in New Zealand for the use of
these data. Analysis of the data suggests that these animals are suitable to provide additional
information on habitat preference in the study area. The pop-up tags provide information about
the sub-surface temperatures that the tagged SBT encounters in addition to the SST. This report
used SBT sub-surface temperature preferences in combination with a sub-surface temperature
oceanographic model to calculate the probability of SBT presence at depths to 200 m. In waters
shallower than 200 m the depth integration is only to the maximum depth. These probabilities are
then combined over all depths to calculate the probability of SBT presence at a single location.
This same methodology is used to generate the habitat forecast shown in Figure 3, with the SST
and sub surface temperature field being replaced by temperature depth fields obtained from the
POAMA model from the Bureau of Meteorology.
The climatology (Figure 4) compares the average latitudinal position of the buffer zone so far this
year with its average position (based on tuna habitat preferences and a 18-year analysis of SST
from 1994 to 2013). The climatology is calculated using the subsurface model. Note that the
width of the buffer in Figure 4 is due to a persistent inshore filament of buffer water along the
coast, and the offshore fraction outside the core of the EAC. This has the effect of moving the
most northern 5% of buffer pixels used to calculate the habitat climatology much further north
than is apparent in the real-time prediction (e.g. Figure 2). The core zone predictions from the
seasonal forecast are shown as red stars on Figure 4. POAMA is not eddy resolving, so there
will be dynamic features of the EAC that are not captured in the seasonal forecast. This effect of
this is that there are small differences in the core zone prediction (Figure 3a), but overall there is
skill in the predictions obtained using POAMA (Hobday et al 2011). The “northerly jump” in the
climatology beginning about April is influenced by limited tag data in this period: the model uses
the limited SBT data from the first portion of the year (Figure 5), and then transitions to using the
bulk of data available after April. This discontinuity will exist until more data from tags at liberty in
February to April are collected.
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East Coast SBT Habitat, AFMA Report
Figure 5: The number of observations from pop-up tags that are used in the analysis during different times
of the year is shown below for each of the years during which the observations were obtained.
Observations Used per day
2500
Observations
2000
1500
2001
2002
2003
2004
2005
2006
2007
2008
2009
All Years
1000
500
0
Jan
Apr
Jul
Oct
Jan
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East Coast SBT Habitat, AFMA Report
Summary of reports
Report
Report sent
from CSIRO
Date of Data
used in
Model
Date
decision
made by
AFMA
Date lines
implemented
by AFMA
1
May 13, 2014
May 7- May 9,
May 14, 2014
May 15, 2014
2014
Line positions
Comments
Buffer Zone: No buffer zone in place.
Core Zone: The western boundary commences on the
coast at the NSW/Victorian border and extends south-east
to latitude 38°30’S, longitude 152°00’E. The line then
continues directly east from this point.
Inshore Buffer Zone: No inshore buffer zone in place
2
May 27, 2014
May 20-22, 2014
No change, assess next week
3
June 3, 2014
May 30 – June 1,
No change indicated
2014
4
June 10, 2014
June 5-7, 2014
June 10, 2014
June 12, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast with latitude
36°30’S and extends due east.
Core Zone: The northern boundary of the Core Zone
commences at the intersection of latitude 37°00’S with the
Inshore Buffer Zone and extends due east.
Inshore Buffer Zone: There has been an inshore Buffer
Zone implemented on the western side of the Core Zone
from the coast out to the approximate position of the
1000 fathom line and extending south to the NSW/Vic
border.
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East Coast SBT Habitat, AFMA Report
June 17, 2014
June 19, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast at latitude
35°15’S and longitude 150°32’E, and extends in a southeast direction to latitude 37°00’S and longitude 152°00’E.
No report sent from CSIRO
Core Zone: no change
Inshore Buffer Zone: in place as in previous advice
5
June 24, 2014
June 20-22, 2014
No Change indicated
July 1, 2014
July 3, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast with latitude
34°00’S and extends east.
Core Zone: The northern boundary of the Core Zone
commences at the intersection of latitude 35°00’S,
longitude 151°19’E with the Inshore Buffer Zone and
extends east.
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July 8, 2014
July 4-6, 2014
July 8, 2014
July 10, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast at latitude
33°30'S and extends east to longitude 153°00'E.
The eastern boundary of the Buffer Zone commences at
latitude 33°30'S, longitude 153°00'E and extends south.
The southern boundary of the Buffer Zone commences at
latitude 35°00'S, longitude 153°00'E and extends west to
the intersection with the inshore buffer zone at latitude
35°00'S, longitude 151°19'E.
Core Zone: The northern boundary of the Core Zone
commences at the intersection of latitude 33°30'S,
longitude 153°00'E with the Buffer Zone and extends east
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No report sent from CSIRO
East Coast SBT Habitat, AFMA Report
July 15, 2014
July 17, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast at latitude
32°30'S and extends south-east to latitude 34°00'S,
longitude 154°00'E.
No report sent from CSIRO
Core Zone: The northern boundary of the Core Zone
commences at the intersection of the inshore buffer zone
at latitude 34°00'S, longitude 151°54.50'E and extends
east.
7
July 22, 2014
July 18-20, 2014
July 22, 2014
July 24, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast at latitude
32°00’S and extends south-east to latitude 34°00’S,
longitude 154°00’E. The line continues north-east to
latitude 31°00’S, longitude 157°00’E and then extends
east.
Core Zone: The northern boundary of the Core Zone
commences at the intersection of the inshore buffer zone
at latitude 34°00’S, longitude 151°54.50’E and extends
east.
July 29, 2014
July 31, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast at latitude
33°00’S and extends south-east to latitude 34°00’S,
longitude 154°00’E. The line then continues north-east to
latitude 30°30’S, longitude 158°30’E and extends east.
Core Zone: The northern boundary of the Core Zone
commences at the intersection of the inshore buffer zone
at latitude 34°00’S, longitude 151°54.50’E and extends
east.
8
August 5, 2014
August 1-3, 2014
August 5, 2014
No change
12
No report, but habitat model images
sent to AFMA from CSIRO.
East Coast SBT Habitat, AFMA Report
August 12, 2014
August 14, 2014
Buffer Zone: The northern boundary of the Buffer Zone
commences at the intersection of the coast at latitude
33°00'S and extends south-east to latitude 34°00'S,
longitude 154°00'E. The line then continues north to
latitude 31°30'S, longitude 154°00'E and then extends
east.
Core Zone: The northern boundary of the Core Zone
commences at the intersection of the inshore buffer zone
at latitude 34°00'S, longitude 151°54.50'E and extends
east
9
August 19, 2014
August 5-7, 2014
August 19, 2014
August 21, 2014
CSIRO SST not up to date (August 6
Buffer Zone: No Buffer Zone in place.
Core Zone: The northern boundary of the Core Zone
commences at the intersection with the Inshore Buffer
Zone at latitude 33°45’S, longitude 152°06.75’E and
extends south-east to latitude 36°00’S, longitude 154°00’E.
The line then extends directly east.
instead of August 16) due to
hardware failure. Alternative SST
and habitat sent independently.
No report sent
Buffer Zone: The upper boundary of the buffer zone
commences at the intersection with the coast at latitude
34°05’S, longitude 151°10.3’E and extends south-southeast to latitude 34°45’S, longitude 151°25.5’E.
Core Zone: The northern boundary of the Core Zone
commences at the intersection with the Inshore Buffer
Zone at latitude 34°45’S, longitude 151°25.5’E and extends
south- east to latitude 35°05’S, longitude 152°10’E. The
line then continues east.
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East Coast SBT Habitat, AFMA Report
10
September 2, 2014
August 27 -31,
September 2,
2014
2014
September 4, 2014
GHRSST data now used for SST
Buffer Zone: The upper boundary of the buffer zone
commences at the intersection with the coast at latitude
34°05’S, longitude 151°10.3’E and extends south-east to
latitude 34°30’S, longitude 151°32’E.
Core Zone: The northern boundary of the Core Zone
commences at the intersection with the Buffer Zone at
latitude 34°30’S, longitude 151°32’E and extends southeast to latitude 36°00’S, longitude 153°00’E. The line then
continues east.
11
September 16, 2014
September 12-
September 16,
14, 2014
2014
September 18, 2014
POAMA forecast not updated due
Buffer Zone: The upper boundary of the buffer zone
commences at the intersection with the coast at latitude
34°05’S, longitude 151°10.3’E and extends south-east to
latitude 34°30’S, longitude 151°32’E.
operational holdup
Core Zone: The northern boundary of the Core Zone
commences at the intersection with the Buffer Zone at
latitude 34°30’S, longitude 151°32’E and extends southeast to latitude 36°00’S, longitude 154°00’E. The line then
continues east.
October 8, 2014
October 9, 2014
No report sent, main report images
Buffer Zone: The upper boundary of the buffer zone
commences at the intersection with the coast at latitude
35°30’S and extends east to the edge of the inshore buffer
zone at latitude 35°30’S, longitude 150°56.80’E.
sent via email
Core Zone: The northern boundary of the Core Zone
commences at the intersection with the inshore Buffer
Zone at latitude 35°30’S, longitude 150°56.80’E and
extends directly east.
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October 14, 2014
October 11-13,
October 15, 2014
No change
2014
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East Coast SBT Habitat, AFMA Report
13
October 28, 2014
October 25-27
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East Coast SBT Habitat, AFMA Report
References
Beggs, H. 2007, A high-resolution blended sea surface temperature analysis over the Australian region, BMRC Research Report, RR130, Bur. Met. Australia. 43
pp.
Hobday AJ, Hartog J, Spillman C, Alves O 2011 Seasonal forecasting of tuna habitat for dynamic spatial management. Canadian Journal of Fisheries and
Aquatic Sciences. 68, 1-14.
Hartog J, Hobday AJ, Matear R, Feng M (2011) Habitat overlap of southern bluefin tuna and yellowfin tuna in the east coast longline fishery - implications for
present and future spatial management. Deep Sea Research Part II 58, 746-752.
Hobday AJ, Hartog JR, Timmis T, Fielding J (2010) Dynamic spatial zoning to manage southern bluefin tuna capture in a multi-species longline fishery. Fisheries
Oceanography 19, 243253.
Hobday AJ, Flint N, Stone T, Gunn JS (2009) Electronic tagging data supporting flexible spatial management in an Australian longline fishery. In 'Tagging and
Tracking of Marine Animals with Electronic Devices II. Reviews: Methods and Technologies in Fish Biology and Fisheries'. (Eds J Nielsen, JR Sibert,
AJ Hobday, ME Lutcavage, H Arrizabalaga and N Fragosa) pp. 381-403. (Springer: Netherlands)
Hobday AJ, Hartmann K (2006) Near real-time spatial management based on habitat predictions for a longline bycatch species. Fisheries Management &
Ecology 13, 365-380.
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