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

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

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.

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.

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.

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.

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

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?

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.

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.

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.

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.

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.

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

“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.

“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

“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

“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.

“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.

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.

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.

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.

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:

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

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.

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.

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.

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.

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.

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

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.

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.

Thanks

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.