1. Visual Sampling of Fishes Introduction to SamplingIntroduction to Sampling Visual Sampling MethodsVisual Sampling Methods Evaluation of EffectivenessEvaluation of Effectiveness

2. GOAL: Describe Complex Biological Communities PROBLEM: Complete census is impossible!! APPROACH: ‘sub-sample’ several units

3. Progressive levels of sampling effort. Quantitative - estimates species present and densities Semi-quantitative - estimates species present and relative abundance Qualitative - estimates species present, no abundance information Time (= cost) increases with each level

4. Random vs Fixed Stations Random sampling: addresses some parametric test assumptions Fixed-station sampling: greater power when funding limited

5. Spatial and Temporal Considerations Many projects sample at established: time of day, lunar cycle, tidal cycle... Sampling day and night, or among seasons Distributional studies sample randomly through space

6. 1. Qualitative Description Presence/absence only – no abundance estimates Example: Timed Swim establish specified time haphazard swim record species observed

7. REA Fish Survey Depth/habitat distributions Island checklist of species New records, range extensions Species-site Checklist

8. 2. Semi-Quantitative Description Rapid Visual Transect (RVT) Relative abundances estimated Species-time relationships Commoner species sighted before rarer species

9. Rapid Visual Transect 1.Establish time survey duration (e.g., 0.5 hrs, 1.0 hrs, etc.). 2.Divide survey period into sub-intervals (e.g., 5 or 10 mins). 3. Surveyor swims freely within sampling habitat.

10. 4.Each species is recorded once 5.In the time interval first seen.

11. 6. Species assigned scores based on time seen: Time Interval Score 00:00-04:5915 05:00-09:5924 10:00-14:5933 15:00-19:5942 20:00-24:5951 7. Scores from multiple surveys are averaged. 8.Rank mean scores (higher score = common; lower score = rare).

12. 3. Quantitative Description 1. Densities are estimated 2. Sampler records: a. species observed b. number of individuals of each species c. size/position of each individual (optional)

13. Quantitative Descriptions Methods taught at QUEST: Strip Transect (SST) Stationary Point Count (Circular Plot - CPLOT)

14. Strip Transect (SST) Deploy transect line Record species and number (and size) in assigned segment

15. In QUEST: four 25 m transects (paired) sampled per team 25 m 2 m 25 m 4 m 50 m transect line 4 m

16. Transect 1 25 m Transect 1 25 m Transect 2 25 m Transect 2 25 m Diver 1 Diver 2 Fish identified to “species” & counted Swim-out: record fish >20 cm in 4m wide swath Swim-back: record fish <20 cm in 2m wide swath Fish identified to “species” & counted Swim-out: record fish >20 cm in 4m wide swath Swim-back: record fish <20 cm in 2m wide swath 2m Fish Belt-Transect - NOAA Program Method Common species listedCommon species listed Enter number andEnter number and size of each size of each Common species listedCommon species listed Enter number andEnter number and size of each size of each

17. Popular in Caribbean Plots usually chosen randomly or haphazardly In QUEST: Transect line is deployed Team waits for fishes to settle Then proceeds to pre-determined ‘point’ Stationary Point Count Circular Plot – ‘C-PLOT’

18. Record all fishes within a cylinder set radius height above bottom (at QUEST r = 5 m, h = 1 m) Cylinders cannot overlap Each cylinder treated as a replicate r

19. 7.5m radius circle 7.5m radius circle 7.5m radius circle 7.5m radius circle Diver 1 Diver 2 4, 15-m diameter “cylinders”, 12-15m deep 1 st, 5 min. – create a list of species observed; NO counts or sizes recorded. After 5 min. – divers count & size individuals 4, 15-m diameter “cylinders”, 12-15m deep 1 st, 5 min. – create a list of species observed; NO counts or sizes recorded. After 5 min. – divers count & size individuals 30m transect Fish Stationary Point Count (SPC)

20. END Multiple methods are used in some Programs

21. Evaluation of Visual Surveying Effectiveness

22. A. Principal Advantages 1. least disruptive and biased method for surveying fishes 2. fairly inexpensive (compared to ???)

23. B.Principal disadvantage: some species chronically under-estimated: 1. large, mobile species (jacks, sharks).

24. 2.schooling fishes with patchy distributions (small jacks, mullet, some goatfishes). B.Principal disadvantage: some species chronically under-estimated:

25. 3.cryptic species (cardinalfishes, eels, gobies, blennies). B.Principal disadvantage: some species chronically under-estimated:

26. 4. rare fishes B.Principal disadvantage: some species chronically under-estimated:

27. 2.Swimming speed affects accuracy a.at fast speeds, uncommon species overlooked. b. at slow speeds, mobile species overestimated. c. rare species overlooked at all speeds.

28. Happy Hunting!