1. Trawl – Total Effort & Catch Estimation http://www.safmc.net Joël Prado - FAO/FIIT http://www.whboat.com

2. Sampling Priorities 1. Collect information on fishing effort 2. Randomly sample for catch composition 3. Record gear characteristics 4. Collect length-frequency data on target and non-target catch

3. Objectives Describe two methods to estimate total catch Determine when each method should be utilized Demonstrate ability to complete the Trawl Effort / Catch form

4. Total Catch Estimation Make an estimate for every haul 5 methods – not all appropriate on all vessels Choice of method depends on haul size observer presence when haul comes aboard Unsorted or sorted first

5. Total Catch Estimation - Methods 1. Weigh entire catch (small, ~400 kg,) before or after sorting; 2. Weigh subsample, tally total baskets and extrapolate to total catch using average basket weight (moderate, ~400-750kg); 3. Volumetric estimate: Bin or codend (large); 4. Catch/effort ratio – using “similar” hauls 5. Captain/vessel estimate – least desirable 10. Unable to estimate Section 6.6.1 of Observer Manual

6. Tow comes on board Determine approximate catch size <16 baskets 2A – Method #1 i. Shovel all catch to baskets ii. Weigh each basket iii. Sum weights & record total weight >16 & < 30 baskets 2B – Method #2 i. Shovel all catch to baskets ii. Weigh ~10 baskets and count the rest iii. Multiply total number of baskets by average weight of 10 baskets Go to #3 3B Go to Catch Comp # 4 > 30 baskets Yes 3A Done Total Catch Estimate Figure 6-13 in manual 2 3 Sampling for catch composition? No Observer On deck Observer Not on deck 1A– Method #4 Catch/effort ratio 1 Similar tows? 1B – Method #5 Captain’s estimate Yes No 2C – Method #3 i. Measure dimensions of bin, deck or codend ii. Calculate catch volume iii. Collect 4-6 baskets of unsorted catch for density sample iv. Weigh & record basket weights v. Calculate total catch weight by multiplying volume by density Go to #3

7. Tow comes on board Determine approximate catch size <16 baskets 2A – Method #1 i. Shovel all catch to baskets ii. Weigh each basket iii. Sum weights & record total weight >16 & < 30 baskets 2B – Method #2 i. Shovel all catch to baskets ii. Weigh ~10 baskets and count the rest iii. Multiply total number of baskets by average weight of 10 baskets Go to #3 3B Go to Catch Comp # 4 > 30 baskets Yes 3A Done Total Catch Estimate Figure 6-13 in manual 2 3 Sampling for catch composition? No Observer On deck Observer Not on deck 1A– Method #4 Catch/ effort ratio 1 Similar tows? 1B – Method #5 Captain’s estimate Yes No 2C – Method #3 i. Measure dimensions of bin, deck or codend ii. Calculate catch volume iii. Collect 4-6 baskets of unsorted catch for density sample iv. Weigh & record basket weights v. Calculate total catch weight by multiplying volume by density Go to #3

8. Catch/effort ratio X = (2.53 mt / 800 minutes) * 238 minutes = 0.752675 mt or 0.75mt HaulTotal Catch (mt) Start Time End Time Duration (min) 170.8722:4702:20273 181.1102:5906:38219 190.5507:1012:18308 20X12:5116:49238 Estimated weight of unknown haul (X) = (Σ Total weight of similar hauls / Σ Haul duration of similar hauls) * Haul duration of unknown haul

9. Tow comes on board Determine approximate catch size <16 baskets 2A – Method #1 – Weigh all catch i. Shovel all catch to baskets ii. Weigh each basket iii. Sum weights & record total weight >16 & < 30 baskets 2B – Method #2 i. Shovel all catch to baskets ii. Weigh ~10 baskets and count the rest iii. Multiply total number of baskets by average weight of 10 baskets Go to #3 3B Go to Catch Comp # 4 > 30 baskets Yes 3A Done Total Catch Estimate Figure 6-13 in manual 2 3 Sampling for catch composition? No Observer On deck Observer Not on deck 1A– Method #4 Catch/effort ratio 1 Similar tows? 1B – Method #5 Captain’s estimate Yes No 2C – Method #3 i. Measure dimensions of bin, deck or codend ii. Calculate catch volume iii. Collect 4-6 baskets of unsorted catch for density sample iv. Weigh & record basket weights v. Calculate total catch weight by multiplying volume by density Go to #3

10. Weigh all catch – before sorting Σ basket weights = = 258.9 kg 24.3 kg 23.3 kg 27.7 kg 22.8 kg 22.9 kg 23.2 kg 24.7 kg 25.6 kg 24.6 kg 24.4 kg 15.4 kg 24.3 + 23.3 + 27.7 + 22.8 + 22.9 + 23.2 + 24.7 + 25.6 + 24.6 + 24.4 + 15.4

11. Weigh all catch – after sorting Σ retained + Σ discard = + = 170.5 kg + 88.4 kg = 258.9 kg Spp A 59.3 kg 18.4 kg 20.1 kg 22.6 kg 27.3 kg DiscardRetained Spp B 45.5 kg Spp C 25.2 kg Spp D 20.3kg Spp E 7.6 kg Spp F 6.8 kg Spp G 4.3 kg Spp H 1.5 kg (59.3 + 45.5 + 25.2 + 20.3 + 7.6 + 6.8 + 4.3 + 1.5 kg) (18.4 + 20.1 + 22.6 + 27.3 kg)

12. Tow comes on board Determine approximate catch size <16 baskets 2A – Method #1 i. Shovel all catch to baskets ii. Weigh each basket iii. Sum weights & record total weight >16 & < 30 baskets 2B – Method #2 – Tally & Extrapolate i.Shovel all catch to baskets (fill evenly) ii. Weigh ~10 baskets and count the rest iii. Multiply total number of baskets by average weight of 10 baskets Go to #3 3B Go to Catch Comp # 4 > 30 baskets Yes 3A Done 2 3 Sampling for catch composition? No Observer On deck Observer Not on deck 1A– Method #4 Catch/effort ratio 1 Similar tows? 1B – Method #5 Captain’s estimate Yes No 2C – Method #3 i. Measure dimensions of bin, deck or codend ii. Calculate catch volume iii. Collect 4-6 baskets of unsorted catch for density sample iv. Weigh & record basket weights v. Calculate total catch weight by multiplying volume by density Go to #3 Total Catch Estimate Figure 6-13 in manual

13. Weigh subset of catch – before sorting Fill evenly – randomly select 10 Σ basket weights (orange) / # baskets weighed = 253.8 / 10 Total count * average = 28 * 25.38 = 710.64 kg Actual = 713.7 kg 27.2 26.1 25.8 24.4 23.6 27.9 26.2 24.4 25.4 27.4 27.1 25.1 27.0 23.4 25.5 24.5 25.9 23.9 26.2 23.5 26.8 24.8 27.7 25.4 27.7 23.6 23.9 23.4 27.2 24.4 27.1 25.1 23.423.9 23.5 26.8 24.8 27.7

14. Weigh subset of catch – after sorting Total catch = Σ retained + discard estimate Σ retained = 80.1 + 79.8 + ….18.9 = 482.6 kg Fill discard baskets evenly – randomly select 4 Σ basket weights (orange) / # baskets weighed = 105.2 kg/4 = 26.3 kg Discards = Total basket count * average = 9 * 26.3 kg = 236.7 kg Total Catch = 482.6 + 236.7 = 719.3 kg Actual = 713.7 kg 25.9 23.9 26.2 23.5 26.8 24.8 27.7 25.4 27.7 Spp A 80.1 kg Spp A 79.8 kg Spp A 80.5 kg 25.9 25.4 27.7 26.2 Spp B 21.0 kg Spp B 19.9 kg Spp B 20.2 kg Spp B 20.5 kg Spp C 20.8 kg Spp C 20.0 kg Spp D 5.7 kg Spp E 14.3 kg Spp F 19.7 kg Spp F 20.5 kg Spp F 20.4 kg Spp G 18.9 kg Spp A 20.3 kg DiscardRetained

15. Tow comes on board Determine approximate catch size <16 baskets 2A – Method #1 i. Shovel all catch to baskets ii. Weigh each basket iii. Sum weights & record total weight >16 & < 30 baskets 2B – Method #2 i. Shovel all catch to baskets ii. Weigh ~10 baskets and count the rest iii. Multiply total number of baskets by average weight of 10 baskets Go to #3 3B Go to Catch Comp # 4 > 30 baskets Yes 3A Done 2 3 Sampling for catch composition? No Observer On deck Observer Not on deck 1A– Method #4 Catch/effort ratio 1 Similar tows? 1B – Method #5 Captain’s estimate Yes No 2C – Method #3 – Volumetric estimate i. Measure dimensions of bin, deck or codend ii. Calculate catch volume iii. Collect 4-6 baskets of unsorted catch for density sample iv. Weigh & record basket weights v. Calculate total catch weight by multiplying volume by density Go to #3 Total Catch Estimate Figure 6-13 in manual

16. Volumetric estimate - bin Measurable areas on deck or holding bins Primary measurements: length, width & height Problems/issues: Too much water Accessibility Steps Determine appropriate shape Measure Calculate volume Multiply volume by density http://www.seafish.org/b2b/subject.asp?p=325

17. Volumetric estimate - bin Length = 3.24 m Width = 1.05 m Heights = 0.56 m, 0.43m, 0.48m, 0.3m, 0.35m, 0.27m H Average = 2.49 / 6 = 0.415 m Volume (rectangular bin) = L * W * H average V = 3.24m * 1.05m * 0.415 m = 1.41183 m3 Estimated weight = V * density = 1.41183 m3 * 0.912554 mt/m3 = 1.28837111382 mt Estimated weight = 1.29 mt

18. Volumetric estimate - bin Wedge Volume = ½ (H * L * W) V= ½ (1.2 * 4.32 * 1.47) = 3.81024 m3 H= 1.2 m L= 4.32 m W= 1.47 m

19. Volumetric estimate - codend Ellipsoidal Solid V = π * short radius * long radius * length V = π * a * b * L V = 3.14 *.37 m * 1.53 m * 4.2 m V = 7.469513 m3 L= 4.2 m b= 1.53 m a= 0.37m http://www.net-sys.com

20. Codend measurements Be aware of moving nets in trawl alley Measure dimensions using actual measurements and/or reference points (e.g. premeasuring trawl alley width, length can save time) Measure large codends in sections http://www.photolib.noaa.gov

21. Density Density = Mass (mt) / volume (m3) = Σ basket weights / Σ basket volumes Basket weights (all filled to bottom of handle): 24.3 kg, 20.7 kg, 21 kg, 22.9 kg, 22.7 kg, 23 kg Total basket wt = 134.6 kg or 0.1346 mt Basket volume = L * W * H V= 0.41 * 0.26 * 0.22 V= 0.023452 m 3 Density (ρ) = mass (mt) / V (m 3 ) ρ =.1346 mt / (0.023452 m 3 * 6) ρ =.1346 mt / (0.140712 m 3 ) ρ = 0.95656376 mt/m 3 L= 0.41 m W= 0.26 m H= 0.22 m

22. Total Weight Calculations Total weight estimate = volume * density Observer logbook Diagrams – if possible, make measurements of trawl alley and/or bins before leaving port Space for haul by haul calculations Record all original measurements and formulas used

23. Issues – removal of catch prior to sorting Dangerous or other ‘protected species‘ may be removed prior to sorting. Inorganic debris & plant material Large fish Record number, species, estimated weight and include the weight in the total catch estimate Record on spp comp form if appropriate

24. Retained catch estimate Sometimes you will be unable to access discards Retained based on # cartons retained * average carton weight Species# cartons retained Carton weight Estimated retained weight per species Cassava fish325 kg75 kg Shrimp1220 kg240 kg Grouper125 kg TOTAL340 kg or 0.34 mt

25. Trawl Effort / Total Catch form Make an entry for EVERY DAY you are on board (including non-fishing days) And EVERY HAUL

26. Trawl Effort / Total Catch form

28. Figure from Davies and Lesch (1998)

29. Trawl Effort / Total Catch form

30. Activity / Homework Working alone but you can discuss among yourselves 15 minutes then the rest is homework Turn in when class starts tomorrow Review answers after graded

31. Summary What are the 2 types of volumetric catch estimates? When should a volumetric estimate be used? When should you weigh a subsample of the catch and extrapolate to the total basket count? How do you estimate catch if you were asleep during a haulback? True or false – Make an entry on the trawl effort and total catch form for sampled hauls only.

32. Activity - answers.35

33. Activity - answers Haul #: 1 Total catch WT: 1.00 Total Weight Calculation Captain estimate Density / Other Calculation Haul #: 2 Total catch WT: 0.39 Total Weight Calculation Used hauls 3-5 for catch/effort ratio (0.78 +0.70+0.34 mt) * 147min = (267+217+204 min) (1.82 mt) * 147min = 0.38886627 mt (688 min) Density / Other Calculation 267

34. Activity - answers Haul #: 3 Total catch WT: 0.78 mt Total Weight Calculation Weigh subsample / count baskets Basket weights (kg) 26.3 +23.2+ 24.6 + 24.1 + 23.6 + 25.8 + 24.9 + 23.8+ 24.1+ 23.3 = 243.7 kg Average basket weight = 243.7 kg / 10 baskets = 24.37 kg / basket Total baskets=32 Total catch = 32 baskets* 24.37 kg /basket = 779. 84 kg Convert to metric tons (mt) = 779. 84 kg ÷ 1000 kg/mt = 0.77984 mt Density / Other Calculation

35. Activity - answers Haul #: 4 Total catch WT: 0.70 mt Total Weight Calculation Weigh subsample / count baskets Total retained: 347.3 kg Total # discard baskets: 14 discard baskets weighed= 26.3 +24.2+ 26.9 + 25.1 + 25.6 + 24.8 + 26.9 + 24.2+ 24.7+ 24.3 = 253.0 kg Average discard basket weight 253.0 kg / 10 baskets = 25.3 kg / basket Discard wt = 14 baskets * 25.3 kg = 354.2 kg Total = Retained + Discards = 347.3 kg +354.2kg =701.5 kg Convert to metric tons 701.5 kg ÷ 1000 kg/mt = 0.7015 mt Density / Other Calculation

36. Activity - answers Haul #: 5 Total catch WT: 0.34 mt Total Weight Calculation Weigh everything =24.3+22.2+24.6+25.1+25.6+24.8+23.9+22.8+ 24.1+22.3+25.2+25.4+25.7+23.5 = 339.5 kg Density / Other Calculation

37. Activity - answers Haul #: 6 Total catch WT: 6.41 mt Total Weight Calculation Codend volume – ellipsoidal solid Measurements L=3.75, Width=2.15, H=1, 1.1, 0.8, 0.8m Average height= (1+1.1+.8+.8) / 4 = 0.925m Vol. = π *length * short radius * long radius V=3.14 * 3.75 * (2.15/2) * (.925/2) V=5.8543828125 m3 Total catch = V * density = 5.85438 m3* 1.094789 mt/m3 = 6.40931 mt Density / Other Calculation Basket wts: 25.6, 24.8, 26.8, 25.5 kg Total basket weights =25.6 + 24.8 + 26.8 + 25.5 = 102.7 kg Convert to mt = 102.7/1000 =.1027 mt Basket volume (Note) 0.023452 m3*4 = 0.093808 m3 density= mass / volume =0.1027 mt /0.093808 = 1.094789 mt/m3 Note: standard volume from manual INCORRECT

38. References Davies, S., and H. Lesch. 1998. The Commercial Sampling Programme, Grade One Observer Manual, Version 2.1 - CSP/03. Ministry of Fisheries and Marine Resources, Commercial Sampling Programme, Observer Section, Walvis Bay, Namibia. Pauly, D. 1984. Some simple methods for the assessment of tropical fish stocks. FAO Fish. Tech. Paper 234, FAO, Rome.

39. Homework 2 – Effort/catch form

43. Freddy Fisherman 18-05-11Global 71D5B-03 8 867 Optimum Observer 0005 Shrimp 897/4 13-05-11 23 24 25 26 23 24 25 26 18-05 00:5302:40 05:5003:25 10:2513:30 15:3017:40 35 8313523 35 37 36 37 34655 17 25 32 41 60 75 CUCsSLSHTR 1 2 1 1 1 4 2 1 14 32 1 210 1 1 11 24 34515 8 4 10 43.1510 44.25 06 08.1306 08.22 10 31.15 10 40.12 06 07.13 06 07.45 10 41.12 10 41.35 06 07.13 10 31.15 06 07.13 10 40.08 06 07.00