1. Estimating & Managing Spawning Potential
Dr Jeremy Prince
Biospherics P/L & Murdoch University
Western Australia
29 November 2017
Thank you for the chance to tell you about a new type of assessment we have developed to inform Community Based Fisheries Management
called Spawning Potential Surveys.
Acknowledgements:
David and Lucile Packard Foundation
US Aid, NZ Aid, Australian Aid, ADB
WCS, TNC, WWF

2. Since 2012 the Packard Foundation has been funding the development and implementation of this approach with reef fish in the Western Pacific.

3. Palau 2012 TNC
Starting in 2012 with TNC in Palau.

4. Solomon Islands 2014 WWF
And in 2014 in the Solomon Islands with WWF and funding from Australian Aid, John West and now European Aid.

5. Fiji 2014 WWF & WCS
In Fiji since 2014 with WWF helped with funding from NZ Aid.

6. PNG 2015 WWF & WCs
Since 2015 in northern PNG with WWF again helped with funding from Australian Aid and John West.
Let me give you a quick taste of how we inform CBFM in each country with simple assessments and management advice.

7. The Overfishing Problem
Pacific Communities are keenly aware of the symptoms of Overfishing,
But generally without realizing the decline in their reef fish is mainly due to their own overfishing.

8. 1 They have to go further and further
2. deeper and deeper
3. to catch their fish.

9. 1965 1985 2015 Over time the size of fish Is getting smaller
And smaller
1965
1985
2015

10. Fishing Down the Food Web
The same process of fishing down the food web is occurring everywhere

11. Fishing Down the Food Web
Everyone starts with a similar food web.
Big bodied higher order predators, groupers and the sharks on top,
Eating the medium size predators
which in turn eat
smaller fish below them in the food web.

12. Fishing Down the Food Web
Big is Best
The first species to go are the highest order predators that breed at the biggest sizes.

13. Fishing Down the Food Web High value – market & culture
Big is Best
High value – market & culture
Then all the most valued large and medium bodied snappers, emperors and parrot fish disappear.

14. Fishing Down the Food Web High value – market & culture
Big is Best
High value – market & culture
Easy to Catch
Then anything that is easy to catch.

15. Fishing Down the Food Web
Big is Best
High value – market & culture
Easy to Catch
Eventually only the fish that once no-one wanted to eat are left and people start eating what they once used as bait.
But without effective management fishing down he food web doesn’t stop there.
This is what the communities I work with north of Madang now consider a good day’s fishing
Eventually only fish no-one wants are left

16. Madang, Papua New Guinea A Catch for One Day of Fishing!
Last trip they introduced me to a new concept. Telling me that they no longer fish for meat …….”

17. Madang, Papua New Guinea A Catch for One Day of Fishing!
Fishing for Soup
…….they fish for soup.”

18. Where are we going? From this? To this? To this?
So each communities needs to ask themselves…... Where are we now? and what will our future be? Are we going from this
2. To this?
3. To this?
4 And eventually to this …..?

19. Where are we going?
To this?

20. The Solution to Overfishing
Having crystalized the overfishing issue with communities
We find they start asking about solutions.
The solution is to change old ways of thinking and behaving.
Before our workshops we find people haven’t thought about sustaining fish.
For them fish are just like the air and water, that we take for granted and just breath and drink without thinking about.
As the old saying goes;
“God always provides.”
Meaning it has always been there … and presumably always will be

21. Change Old Thinking Wasting Food The Small fish are sweetest
People think instead about not wasting food.
They say; ‘the smallest fish have the sweetest meat.”
So small fish are not released to finish growing and to breed.
Because that would be a waste of good food.
So we challenge people with the fact that they know how to work with the natural productivity of their gardens but treat the reef differently
In the gardens you look after little things until they get big and become productive.

22. Suppose you want to farm pigs.
You buy piglets
This is a pig house that WWF help communities build in Fiji to farm pigs to fund community schools.
So communities bought piglets to stock them.

23. They fed them and they grew.
Feed them and they grow.

24. You do not kill and eat all the young pigs.
They didn’t kill and eat all the piglets,
even though the meat would have been sweet –
they wanted a full pig house and productive farms.

25. Instead you look after them so they give a first litter of piglets.
No they kept looking after them until they grew to be adults and produced a first litter of piglets.

26. Two litters.
Two litters.

27. Three litters.
Three litters.

28. Four litters.
Four litters.

29. Then you eat your pig.
Tthen they killed and ate the pig.

30. And the Pig house is Full
And the pig house was full.
This is how we look after gardens – everyone knows this – this is common sense.

31. But this is what we do to the Reef!

32. But this is what we do to the Reef! We eat the fish before they breed
We catch and eat the fish before they can breed.

33. The reef is just like the gardens.
But the reef is just the same as a garden.
It is a garden in the sea.

34. The reef is just like the gardens
The reef is just like the gardens. Eventually you (cannot) reap what you (did not) sow.
And with all gardens
eventually you reap what you sow, or in this case you cannot keep harvesting what has not been sown.

35. How Much Breeding is Enough?
So this brings us to the question of how much breeding is enough?

36. More than 2 Children per couple Less than 2 Children per couple
Human Populations
Average maximum of 10 Children per couple
Population
Growth
More than 2 Children per couple
2 Children per couple
Population Stable
Replacement Level
Here we get communities to think first about humans.
If on average each adult couple has about two children survive and grow to be adults, then the children replace the adults and the population will be stable.
We call this the replacement level of breeding.
If on average each adult couple has more than 2 children than the populations grow,
And with less than 2 children per couple populations decline.
Less than 2 Children per couple
Population
Decline

37. More than 20% Spawning fish Less than 20% Spawning fish
Spawning of Fish
No Fishing = 100 % spawning fish
More than 20% Spawning fish
Population
Growth
20% Spawning fish
Population Stable
Replacement Level
Less than 20% Spawning fish
Fisheries Science has a similar concept we call Spawning Potential Ratio or just SPR.
With the communities we just talk about spawning.
Without fishing the fish live out their natural life spans and on average complete 100% of their natural spawning potential.
When we catch them, we shorten their life spans and reduce their natural spawning potential
From studies we know that 20% of natural spawning potential is the Replacement Level for fish – like 2 children per couple for humans
Below 20% spawning fish populations can’t replace themselves and decline.
Above 20% spawning populations can replenish the reefs.
With our break through communities can now estimate how much spawning is occurring and develop simple management strategies to maintain spawning levels.
Population
Decline

38. Set Size data: What we need to know?
Our technique uses just two simple types of data that we teach the communities to collect:
And in gathering the data they understand for themselves their own problem with overfishing.

39. Length Composition >200 per species
Set Size data:
Length Composition >200 per species
The main data is the size composition of the catch.

40. Local Size of Maturity >100 per species
Set Size data:
Local Size of Maturity >100 per species
Sabera ni Matau
Immature
Matua – Tagane Mature Male
Matua - Yalewa
Mature Female
(1-3) And secondly an estimate of the size at which fish start breeding.

41. Fishing changes the size of the fish we see on the reef
Our assessment technique is based on how fishing changes the size composition of a fish stock.

42. Size of Maturity
Fisheries science (1) understands clearly how fishing reduces the size of fish in the catch.
(2-8)

43. 20% Spawning http://barefootecologist.com.au Size of Maturity
Our new technique compares these changes to the size of maturity to estimate each stocks spawning potential.
We can now make snapshot assessments with just a single good representative size sample.

44. Lutjanus gibbus Taea Solomon Islands
Spawning = 27%
100%
Mature
Here are some results from the Solomon Islands for Lutjanus gibbus.
In the blue you see what the size would be if there was no fishing, and in the white what the size of fish would be if they were getting 30% of their spawning.
The red shows what we measured, it is similar to the white 30% spawning shape, just a little less, and we estimate they are getting 27% spawning.
But probably more important than the assessment, is that we can easily turn the assessment into simple management advice for communities and government.
Especially advice about size based management; minimum size limits, mesh and hook size, also size targets for stocks to be sustainable.
30%
27%

45. Lutjanus gibbus Taea Solomon Islands
Spawning = 40%
Set Size = 20% Spawning
Mature
Here is what we are calling ‘Set Size’
which for the snappers, emperors, groupers and parrotfish is about 20% bigger than the size of maturity.
If you implement a minimum size limit at this size you protect at least 20% of spawning and most fish won’t be caught at exactly that size and will produce 30-40% of spawning and this will conserve a sustainable level of spawning and make sure each fish is caught at an optimal size.
Of course we can’t end up with every single species having its own size limit, so we are also developing a system for clustering all the reef fish into just 10 size limits – The Set Size system. This will initially be something like a Pacific wide average system. But I’m studying the way fish size varies across the Pacific and am confident we will be able to adjust the system up or down in relation to a countries latitude and water temperature to adapt it for each country.

46. Lutjanus gibbus Taea Solomon Islands
Spawning = 40%
Catch Size = 40% Spawning
Mature
Where minimum size limits cannot be used, we can also estimate what we call ‘catch size’, the size composition that should be maintained if an optimum 30-40% of spawning is to be conserved and sustainable catches optimized.
This can be used to set hook and mesh sizes, or just as a target letting communities know whether their combination of management actions are being successful or need adjustment. Making adaptive management possible for communities
And already we are seeing communities use our approach this way – to see from the size of fish being caught whether stocks are in good or bad shape, and to adapt and try new ways of managing fish

47. What can we do?
So there are many different ways Communities can manage, and already are managing their local fish stocks. And we’ve heard speakers talking about communities wanting information so they can be pro-active and adaptively manage local fish stocks.

48. With our Spawning Potential Surveys (1) by focusing communities on the size their fish are surviving to we can at last give them simple management advice and (2)
enable them to adaptively develop the sustainable management techniques that will work for them. And in all the communities we are working with, in Palau, Fiji, Solomon Islands and PNG, we are seeing this happen, and national fisheries policies are being informed in the process.
Thankyou

49. http://barefootecologist. com
The End Jeremy Prince