1. Estimating ecological count-based measures from the point-intercept method
Assaf Zvuloni1 & Jonathan Belmaker2
1Israel Nature & Parks Authority
2Tel Aviv University

2. Point-Intercept Method (PIM)
How does it work?
16 points
P/A data
8 points on corals
Estimated coral cover:
8/16 = 50%
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
Very efficient, applicable, and therefore, very common technique

3. Point-Intercept Method (PIM)
With the rise of digital data, its use is considerably increasing for the analysis of images and frame-grabbed video.
> 3,500 users
around the world
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

4. Point-Intercept Method (PIM)
With the rise of digital data, its use is considerably increasing for the analysis of images and frame-grabbed video.
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

5. Solely used to estimate parameters related to coverage
Point-Intercept Method (PIM)
- BUT -
Solely used to estimate parameters related to coverage
i.e., % cover, relative coverage
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

6. Point-Intercept Method (PIM)
- WHY -
1) The PIM does not define areas, but locations
(“plotless” technique)
2) The PIM is biased toward large individuals
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

7. Measure which relate to the number of individuals in an area
Ecological count-based measure (ECBM)
Measure which relate to the number of individuals in an area
Size-frequency distribution (SFD )
Mean size (d )
Population density (D )
Relative occurrence of species (Pi )
Species richness (S’ )
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
Non-ECBM - For example, measures calculated according to the coverage of the organisms

8. Point-Intercept Method (PIM) Is this all we can get from the PIM data?
16 points
P/A data
8 points on corals
Estimated coral cover:
8/16 = 50%
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
Is this all we can get from the PIM data?
What about ECBMs?

9. Point-Intercept Method (PIM) In order to do so we have to get
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

10. How do we usually sample ECBMs
The conventional quadrat method (QM)
How do we usually sample ECBMs
(e.g. density, or size-frequency distribution)?
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

11. How do we usually sample ECBMs
The conventional quadrat method (QM)
How do we usually sample ECBMs
(e.g. density, or size-frequency distribution)?
Defined area (“plot-based” technique)
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

12. How do we usually sample ECBMs
The conventional quadrat method (QM)
How do we usually sample ECBMs
(e.g. density, or size-frequency distribution)?
Defined area (“plot-based” technique)
Organisms within this area define the sample
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

13. How do we usually sample ECBMs
The conventional quadrat method (QM)
How do we usually sample ECBMs
(e.g. density, or size-frequency distribution)?
Defined area (“plot-based” technique)
Organisms within this area define the sample
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

14. Point-Intercept Method (PIM) Why can’t we estimate ECBMs by the PIM?
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
AREA
BIAS

15. “Effectively” sampled area (ESA)
The area where a coral's center must be located for it to be included in the sample
Assumption - coral colonies have a circular boundary
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

16. “Effectively” sampled area (ESA)
The area where a coral's center must be located for it to be included in the sample
𝐸𝑆𝐴=𝜋∙ 𝑟 2
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
ESA of a single point

17. “Effectively” sampled area (ESA)
The area where a coral's center must be located for it to be included in the sample
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
𝐸𝑆𝐴=𝜋∙ 𝑟 2

18. “Effectively” sampled area (ESA)
ESA of sets of points
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

19. “Effectively” sampled area (ESA)
ESA of sets of points
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

20. ECBMs from the PIM: Density:
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

21. ECBMs from the PIM: In practice:
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

22. ECBMs from the PIM: In practice:
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

23. Size-frequency distribution:
ECBMs from the PIM:
Density:
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
Size-frequency distribution:

24. 40 sampling units of 10 by 10 points
Simulations
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
40 sampling units of 10 by 10 points

25. Simulation results
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

26. Simulation results
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

27. Real data PIM vs Quadrat
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

28. PIM vs Quadrat method
Most populations in nature show a high frequency of small individuals and low frequency of large ones
(e.g. Enquist & Niklas 2001; Lins de Barros & Pires 2006; Caroselli et al. 2012; Leray et al. 2012; Shaked & Genin 2014)
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

29. PIM vs Quadrat method
Most populations in nature show a high frequency of small individuals and low frequency of large ones
(e.g. Enquist & Niklas 2001; Lins de Barros & Pires 2006; Caroselli et al. 2012; Leray et al. 2012; Shaked & Genin 2014)
Data: National Monitoring Program at the Gulf of Eilat
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

30. PIM vs Quadrat method
Most populations in nature show a high frequency of small individuals and low frequency of large ones
(e.g. Enquist & Niklas 2001; Lins de Barros & Pires 2006; Caroselli et al. 2012; Leray et al. 2012; Shaked & Genin 2014)
We are in essence putting more effort into uncommon groups (large size classes) and less into the common ones (small size classes).
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.
STRATIFIED SAMPLING

31. PIM vs Quadrat method
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

32. PIM vs Quadrat method
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.

33. Thanks

34. How do we usually sample ECBMs
The conventional quadrat method (QM)
How do we usually sample ECBMs
(e.g. density, or size-frequency distribution)?
Defined area (“plot-based” technique)
Organisms within this area define the sample
area <==> sampling effort
2. Ecological count-based measures (ECBMs; i.e., measures which relate to the number of individuals in an area), such as population density, size-frequency distribution, average size, species richness and diversity.