1. Historical reconstruction of a Great Barrier reef spawning fishery in double jeopardy
Good afternoon. Our ability to assess the status and abundance of exploited species is often limited by the temporal and spatial scale of records and analysis. This is a particular issue when assessing exploited aggregating fish species which are particularly vulnerable to overexploitation and are susceptible to declines occurring undetected. In this talk I will be talking about a historical reconstruction of a great barrier reef spawning fishery in double jeopardy
Sarah M. Buckley, Ruth H. Thurstan, Andrew Tobin and John M. Pandolfi
Contact:

2. Why do we need historic data?
Source: McClenachan, L 2009.
Fills in knowledge gaps past environments and species
Shifting baseline syndrome
Extends time-series to determine trajectory of abundance
Historical variability across seasonal and spatial scales
1985
So why do we need historic data? Historical ecology is extremely useful for filling in knowledge gaps regarding changes in past marine environments and species abundance over time
and can counter shifting baseline syndrome, with is an issue with successive generations and what they consider around them as natural.
McClenachans study using historical photographs illustrate this lovely – you see 2007 is considered a typical catch, then 30 years ago the catch has a higher number of fish and this is where it gets interesting – in the 50s they used to catches of higher trophic levels such as grouper which are not evident in todays catch – a great example of shifting baselines.
Historical reconstructions extend the time series of current monitoring records which allow us to determine the true trajectory of population abundance
Yet few studies have unravelled how fishery dynamics vary across seasonal and spatial scales - which is particularly important for determining trends in aggregating fisheries.
2007
1958

3. Spanish mackerel (Scomberomorous commerson)
Indo-Pacific region
Historically most commercially significant fishery in the Great Barrier Reef
Most vulnerable species to line fishing
Opinion divided – “fully fished” by management and “contracted” by fishers
Just to give you a bit of a background, on our cast study Spanish mackerel is a pelagic scombrid that supports commercial, recreational and artisinal fishers throughout it’s Indo-Pacific distribution.
What makes it interesting is that historically Spanish mackerel was considered the most commercially significant fishery in the Great Barrier Reef and Queensland, Australia.
Yet by 2013, SM has been defined as the most vulnerable species to line fishing in the GBR and no specific management actions have been implemented to protect the species.
Why is that the case well – SM is considered by management as fully fished yet fishers constantly complain that the spawning fishery has contracted both in space and time

4. Contemporary fishery Exhibits a predictable and seasonal migration
Enables fishers to efficiently target the stock
So to give you an idea of the contemporary fishery, Spanish mackerel exhibits a predictable seasonal and migratory distribution along the east coast of QLD. Along its migration it forms schools which enables fishers to efficiently target the stock

5. Fish spawning aggregation fishery
Exhibits a predictable and seasonal migration
Enables fishers to efficiently target the stock
Form transient spawning aggregations at a few predictable sites
Forms a 1/3 of total commercial catch
Within the Great Barrier Reef, the east coast stock Spanish mackerel form transient spawning aggregations at a few predictable sites at predictable times, during October and November These FSAs have been which forms at least 1/3 of the total commercial catch.

6. Current data used for assessment
So what is the current data is used for assessment, primarily the assessment is based daily records of catch and effort from 1988 and there is also state landings from 1937 but this is not only for the east coast but also the north coast stock. Yet there is many knowledge gaps to fill, we have no idea what catch trends were like prior to Also we don’t know what proportion is spawning landings and how has it varied over time. Also how has fishing effort changes, have fishers changed their gear and technology? Have they travelled further offshore? How has that affected their catch rate. So we would like to fill in these knowledge gaps

7. Still gaps in current knowledge Proportion spawning landings
So there are many gaps for us to fill, prior to 1937 there is very little information ?
Fishing effort ? ?

8. Data sourced and gathered
We explored a combination of data sources, including historical records, such as newspaper archives where we found information regarding the early spawning fishery.
1952
1952
1952
1990
1990
1990

9. Data sourced and gathered
fisher interviews with 50 commercial and 50 recreational
1952
1952
1952
1990
1990
1990

10. Data sourced and gathered
As well as commercial logbooks – where we analysed specifically spawning landings
1952
1952
1952
1990
1990
1990

11. Data sourced and gathered
Locations targeted
Data sourced and gathered
So we exracted information regarding catch rates, fishing effort, locations targeted, gear and technology and fishers perceptions.
Fishing effort
Gear and technology
Catch rates
Locations targeted
Perceptions

12. Spatial distribution of fishing effort
So we combined historical archives and fisher knowledge we found some really interesting changes in the spatial distribution of fishing effort over time. So in the early period of the fishery fishers fished close to home but by 1940 were already fishing the mid-shelf reed and by 1950 a northern spawning fishery had commenced

13. Spatial distribution of fishing effort
Between 1960 to 1980 fishers travelled further offshore and increased the number of sites they were fishing and by 1980 the Townsville fishers were operating completely offshore

14. Spatial distribution of fishing effort
By 1990 effort is contracting and by 2000 the Cairns fisher have exited the fishery or relocated to the Townsville fishery as it was unprofitable and by 2010 the Townsville fishery had contracted even further

15. Spatial changes in fishing effort
70% decline
We wanted to quantify these spatial changes in fishing effort, so we looked at the maximum number of fished FSAs per decade. From 1910 to 1990, the number of exploited FSAs rose from 1 to 23, then a sharp decline occurred and by 2010 had dropped to 8 fished FSAs. So we see a 70% decline in fishing effort

16. Spatial changes in fishing effort
Supporting this further is the maximum distance fishers travelled offshore, fishers increased from 5 nmiles in 1910 to 80 nm in 1990 and from that period onwards spatial expansion stabilised as fishers stated it was unprofitable to go even further

17. Cairns catch rate n=25 Good
Fisher interviews enabled us to spatially separate catch rates and assess variability in catch, this graph shows the mean values across all commercial fishers for the good
n=25

18. Cairns catch rate
Good
Average
average
n=25

19. Cairns catch rate n=25 Good Average Poor
and poor catch rates in each decade. All catch rates show a decline. In fact catch rates and decreased to a point that fishers exited the Cairns spawning fishery.
n=25

20. Townsville catch rate n=107 Good Average Poor
From interviews fishers had experience fishing the Townsville fishery for a longer period. Similar to Cairns, all catch rates exhibited a declining trend but still profitable for fishers.
n=107

21. Townsville raw catch rate
Newspaper
We know the Townsville fishery occurred for a longer period – and newspaper records allowed us to extract catches from the early history of tis fishery, so this graph shows the mean catch rate per year and you can see the catch is quite variable but stable over time
n=304

22. Townsville raw catch rate
Newspaper
Logbooks
But we wanted to put this in context with the contemporary fishery, and the contemporary catch records allowed us to compare historical and contemporary catches, you can see the contemporary catches are again variable but a bit less than the historical fishery but we have not accounted for changes in gear and technology
n=718

23. Fishing efficiency: fleet adoption rate
Paravene
From fisher interviews we could assess how gear and technology had changed over time and was adopted by the fleet. Here is a sample of he chnages. Here is the adoptio rate of paprvenes, which is a weight that allows baits to be trolled at deeper depths and were adopted from 1962
n=50

24. Fishing efficiency: fleet adoption rate
Paravene
Colour sounder
And colour sounders from 1977 and adopted a faster rate
n=50

25. Fishing efficiency: fleet adoption rate
Paravene
Colour sounder
GPS
and GPS from 1985
n=50

26. Calculating the fishing efficiency index
Top four most influential factors
Total number of vessels fishing +94%
GPS +31%
Colour sounder +21%
Paravene +17%
So we quantified the increased in catch rate from the four most influential factors, fihsers stated the the total number of vessles increased catch by 94% - so if they used two rathern than one it increased by 94%, GPS increased it by 31%, colour sounders by 21% and paravenes by 17%. So we calculated the fishing efficincy increase for each factor by multiplying the average % increase in cach rate by the % of the fleet using the gear per year
% increase in catch rate
% of fleet using gear X
Gear
index =

27. Fishing efficiency index
We combined the four individual fishing effiency indexes to determine the overall fishing efficiency index over time, which you can see from 1962 however we only needed to use the index from 1990 to account for the contemporray fishery catch rate

28. Standardising contemporary catch
Number of fish caught trip-1
Adjusted catch rate
So we standardised the contemporary catch by dividning the number of fish cught per trip by the combined fishing efficiency index for the adjusted catch rate =
Fishing efficiency index

29. Townsville raw catch rate
Newspaper
Logbooks
So this is the raw catch data
n=718

30. Adjusted catch rate 70% decline 114.35 fish 35.4 fish
We then compared it with the standardised the contemporary catch rate which demonstrates a more obvious decline, from 119 fish caught historically to 35 fish per trip, a decline of 70% which is peculair if you remember the spatial fishing effort distribution declined by 70% and so has the contemporary cacth rate
fish
35.4 fish

31. Shifting baselines Decrease
So we wanted to see if fishes were operating on a similar shifted baselien to management. A larger proportion of fishers who commenced in the early period of the fishery, perceived a decrease in the abundance of Spanish mackerel FSA abundance

32. Shifting Baselines Decrease Stable
In contrast to a larger proportion of fishers who commenced in the late period of the fishery consider the abundance of SPM to be stable.

33. Findings/Next steps
Reconstructed spawning fishery since inception and extended time-series by 7 decades: from 1990 to 1911
Sequential exploitation, spatial expansion and increases in fishing efficiency in attempt to sustain catch rates
Catch rates declined by 70% and spatial effort distribution reduced to 30% of fished FSAs
Application of data to management - working with QLD fisheries and GBRMPA
Feeding information back to fishing communities
So far we have reconstructed the spawning fishery since it’s inception and have extended the reference point by seven decades from 1990 to 1911.
We have demonstrated by investigating the fisheries historical dynamics across temporal and spatial scales reveals sequential exploitation, spatial expansion and increase in fishing efficiency in attempt to sustain catch rates.
We found that catch rates have declined by 70% and spatial effort distribution has declined by 70%of exploited FSAs
we plan to work with various management agencies to work out how this data can be applied
and we also intend to feedback this knowledge back to the fishing communities who so kindly participated in this research

34. Acknowledgements All the fishers who took part!
Queensland Fisheries, Dr. Simon Blomberg, Marine Paleolab members
Contact:
Thanks

35. Increase in catch rate n=50 Number of vessels +94% GPS + 31%
Paravene
Colour sounder
GPS
and GPS from 1985
Number of vessels +94%
GPS + 31%
Paravene +17%
Colour sounder +21%
n=50

37. Spatial changes in spawning fishery
have shown quite significant spatial changes in the spawning fishery.

38. Drivers of change Fisher Percpetions Recreational exploitation
Management actions
Fisher Percpetions
Cumulative impacts
Fishers reported 23 drivers of change – the majority (52%) reported cumulative impacts caused the over decline of the fishery – the major dirvers percievd by recreational fishers was recreational exploitation (68%), overfishing of juveniles (52%) destruction of nursery habitats and management actions or lack there of
Destruction of nursery habitat
Overfishing of Juveniles