ESTIMATION OF GHANA S TASKS I AND II PURSE SEINE AND BAITBOAT CATCH : DATA INPUT FOR THE 2016 YELLOWFIN STOCK ASSESSMENT

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1 SCRS/2016/107 Collect. Vol. Sci. Pap. ICCAT, 73(2): (2017) ESTIMATION OF GHANA S TASKS I AND II PURSE SEINE AND BAITBOAT CATCH : DATA INPUT FOR THE 2016 YELLOWFIN STOCK ASSESSMENT Mauricio Ortiz 1 and Carlos Palma 1 SUMMARY Information from the AVDTH Ghana fisheries and other sources was used to estimate the task I and II for the Ghanaian tuna baitboat and purse seine fisheries during Catch and landing data collected and managed by the Marine Fisheries Research Division (MRFD) of Ghana included both landings and logbook information from 2005 up to The estimation of total Ghana catches, catch composition and quarterly-spatial (5 x5 ) distribution followed the recommendations from the SCRS Tropicals working group agreed during the yellowfin data preparatory meeting. Sampling for species composition and size distribution were review and compared to equivalent European sampling to determine appropriate sampling for the different components of the Ghana fleets by major gear type. In summary, estimates of total YFT catch from the AVDTH database were higher compared to Task I reports for 2011 to RÉSUMÉ On a utilisé l'information des pêcheries ghanéennes d'avdth et d'autres sources afin d'estimer la Tâche I et la Tâche II pour les pêcheries de canneurs et de senneurs ghanéens entre 2006 et Les données de capture et de débarquement recueillies et gérées par la Division de la recherche sur les pêches marines (MRFD) du Ghana incluaient des informations à la fois sur les débarquements et les carnets de pêche de 2005 à L'estimation des prises ghanéennes totales, de la composition des prises et de la distribution trimestrielle-spatiale (5ºx5º) a suivi la recommandation du groupe d'espèces du SCRS sur les thonidés tropicaux convenue pendant la réunion de préparation des données sur l'albacore. L'échantillonnage réalisé pour obtenir la composition par espèce et la distribution des tailles a été examiné et comparé à l'échantillon européen équivalent pour déterminer l'échantillonnage approprié pour les différentes composantes des flottilles ghanéennes par type d engin principal. En résumé, les estimations de la prise totale d'albacore à partir de la base de données AVDTH ont été supérieures par rapport aux déclarations de la Tâche I pour les années allant de 2011 à RESUMEN Se utilizó la información AVDTH de las pesquerías de Ghana y de otras fuentes para estimar la Tarea I y la Tarea II de los cañeros y cerqueros atuneros de Ghana durante Los datos de captura y desembarque recopilados y gestionados por la Marine Fisheries Research Division (MRFD) de Ghana incluían información de desembarques y de los cuadernos de pesca de 2005 hasta La estimación de las capturas totales de Ghana, la composición de la captura y la distribución trimestral y espacial (5ºx5º) siguió las recomendaciones del grupo de trabajo sobre túnidos tropicales del SCRS, acordada durante la reunión de preparación de datos de rabil. El muestreo para la composición por especies y las distribuciones de talla fue revisado y comparado con el muestreo europeo equivalente para determinar el muestreo apropiado para los diferentes componentes de las flotas de Ghana por tipo de arte principal. En resumen las estimaciones de la captura total de rabil a partir de la base de datos AVDTH fueron superiores a las de los informes de Tarea I para los años 2011 a KEYWORDS Ghana, yellowfin tuna, tropical tuna fisheries, purse-seine, baitboat 1 ICCAT Secretariat C/ Corazón de Maria 8, 6 th floor Madrid 28002, Madrid Spain. 482

2 1. Introduction The guidelines and protocols for estimating the Ghanaian tropical tuna fisheries data covering the period were defined and agreed during the Data Preparatory meeting for the yellowfin tuna assessment (Thunnus albacares) (Anon 2016). The objective was to estimate Ghanaian Tasks I and II (CE/SZ/CAS) as inputs for the different stock assessment models based primarily on the fisheries data collected and provided by Ghana and European scientist to the Secretariat under the AVDTH program. Overall, the Tropicals working group (WG) concluded that guidelines and protocols of data treatment and estimation should follow those used for the latest bigeye tuna assessment (Anon 2016) as specified in the document SCRS/2015/139. Briefly, the WG recommended the following: a) The Ghanaian fleet should be split into two components; national fleet component Fleet A and Fleet P, and estimations being provided by these two fleets for nominal catches (Task I), catch and effort (Task II CE), size and catch-at-size (Task II SZ, CAS). b) Use vessel as sampling unit whenever possible. c) Total catch by year of the main tropical tunas (SKJ, BET, YFT) should be based on the higher value between the catch reported from landings and logbooks, as registered in the ADVTH database. d) Estimation of the catch species composition of major tunas (SKJ, BET, and YFT) should be derived from the species composition of the EU fleet fishing on fish aggregating devices (FADs). e) Estimation of the size composition of the catch for YFT should be based on: i. Ghanaian samples collected in Tema for the Ghana national fleet (Fleet A) component, and ii. From the size sampling obtained from the EU PS fleet fishing on FADs for Fleet P. The present analysis covers the period The estimation procedures then provided several outputs: a) the YFT Task I NC proposed for assessment purposes of Ghana commercial fleets 2006, b) Equivalent estimates of Task 2 catch/effort (CE) for YFT and other main tropical tunas (SKJ, BET) by fleet, gear, fishing mode, quarter and month, with estimates of fishing effort (fishing days, days at sea). c) Task 2 Size samples for YFT by quarter, vessel and 1 x1 lat-lon degree square. And d) Task 2 CAS for YFT by fleet, gear, fishing mode, quarter, 1 x1 lat-lon degree square, in 2 cm FL size bins. The objective was to have a complete set of information that is consistent for integrating within other fisheries statistics for the assessment inputs. 2. Materials and Methods 2.1 Ghana AVDTH database for The latest Ghanaian AVDTH database was kindly provided (MS Access 2005_2014_V3.5_Access_2007.zip) by the Marine Fisheries Research Division (MRFD) of Ghana in collaboration with EU_France Tropical fisheries scientist. The database includes all logbooks, sale record by commercial category and size-frequency samples collected by MRFD during , with few data available for This data excluded the vessel 714 (Vessel ID) which was flying the Ghana flag during but has been included since 2009 in the associated flags of the European PS fleet (Delgado de Molina et al., 2013). It was also provided a series of SQL queries for basic data extraction and reporting directly link to the Ghanaian AVDTH database and extracts of the catch species composition and size composition of the EU [FRA/SPA] for the same time period. Table 1 summarizes the total catches from the Ghanaian Tropical tuna fleets by year, fleet, gear and vessel unit for For 2007 there are missing several reports of catches from vessels that operated in 2006 and also in 2008, therefore similarly to the case for BET (SCRS/2015/139), no estimates of catches and species or size composition were done for the 2007 fishing year, as clearly there is only limited information available. Table 1 also shows vessels that did reported catches of YFT in 2013 and prior years but did not report YFT catches in These include: 2 baitboats (EDEM, ELI) and 3 purse seiners (DELALI, OWUM OPESIKA, YOUNG BOK). There is also a baitboat that have reported catches of YFT for the first time in 2014 (MADANFO). Table 2 summarizes the reported landings for all species by gear and year from the same database. 483

3 2.2 Ghana samples A total of 1,658 size-frequency samples have been collected from unloading of tropical tunas of purse seiners, baitboats and cargo vessels at the ports of Tema (Ghana), Walvis Bay (Namibia), Pointe Noire (Congo, 2014) and Takoradi (Ghana, 2014) from Ghanaian fleet vessels (Table 3). In this case, a size sample is a single size frequency record by vessel unit and date of landing, which likely represents the landings of more than one fishing activity (set) at sea during the trip. As indicated for BET, sampling is considered reliable for computing the size structure catch for the particularly for the Ghana national Fleet A for both baitboat and purse seine operations. In contrast, sampling from the Fleet P is only available from 2012 to Prior analyses also indicated that Ghana sampling (AVDTH database) collected from 2013 to 2014 are suitable for estimating species composition of the catch (Damiano et al. 2013, Chassot et al. 2015) for fleet A and fleet P. 2.3 Samples collected from the European PS fishery EU sampling protocols were established in 1998 (Pallares and Hallier 1997) as a simultaneous sampling to estimate size and species composition of the catch. A sampling strata unit representing a homogeneous species and size composition is defined by the fishing mode (FADs both natural and anthropogenic made floating devices, free-swimming schools (FSC)), quarter and large spatial areas (Fig 1). Sampling is done during the unloading of the purse seine at fishing ports and consists of a 2-step sampling protocol: i) wells are selected from among those containing homogeneous strata, and ii) fishes are randomly collected, within size category, from the wells and counted and/or measured. 3. Methods 3.1 Total Task I The estimation of yellowfin catch for the Ghana fleets follow the recommendations of the SCRS Tropicals Working Group, that basically endorsed the procedure used for estimating Ghana s bigeye tuna catch in 2015 (Chassot et al. 2016). This consist in: i) estimating the annual total catch of the fleets A and P ( ), ii) distributing the total catch in time (month) and space (5 x5 lat-lon degree square), iii) estimating the species an size composition to each month-5x5 stratum. In Chassot et al it were included two modifications compared to prior estimations; a) in the areas used for data processing, it was replaced the EU-area definitions by the Ghana area definition (Figure 2), and b) it was used the Ghana size samples for estimating the size composition of the catch for the Fleet A. Thus for estimating Task I a review and summary of the annual catch by fleet and gear from the logbook data and the landing report were done (Table 3). Reviewing the catches by year and vessel ID it was concluded that most of the missing logbook catch reports were from the Ghana P-Fleet prior to 2012 (Table 2). Therefore the missing catch was allocated to the Fleet-P PS operating on FADs component for the years 2006, 2008, 2010 and A raising factor was estimated for each year and applied to the Fleet P by vessel, year, quarter and 5 x5 lat-lon strata. 3.2 Spatial temporal distribution of the catch The next step was to estimate the spatial-temporal distribution of the catch to produce the Catch-effort for the Ghana fleets. The assumption is that the Fleet-P operates similarly to the EU- PS FADs fishing fleets. Figure 1 shows the distribution in 1 x1 lat-lon of catches and sampling from the EU_FRA/EU_SPA for The areas represent the EU geographical distribution used for the processing of EU AVDTH data. Similarly, Figure 2 shows the distribution of catches and sampling from the Ghana all fleets for In this case the areas correspond to the Ghana geographical distribution proposed and used for the estimations in the case of BET in 2015 (Chassot et al. 2016). In general the EU and Ghana fleets cover a wide area in the tropical Atlantic extending up to the 25 N and 20 S, while covering most of the West African coast, the Gulf of Guinea and extending to the 35 W. However, when the same plots were produced for only the Ghana P-Fleet, examining the years when most of the logbooks are reported it is clear that this fleet has a much restricted area of activity, basically between the 5 N and 10 S and extending from the Gulf of Guinea to 30 W, with fewer catches inside the Cape Lopez area (Figure 4). 484

4 Furthermore, plotting the catches of the P-Fleet by 5x5 and quarter, for (Figure 5) it shows a seasonal pattern that is also evident when plotted by year and month (Figure 4). This is in contrast at least with the information regarding the fishing effort (Figure 6), where most of the fishing activity seems to be concentrated in or around the Gulf of Guinea off the Ghana and Ivory Coast coastal regions. In a recent presentation by an expert scientist on tropical tuna fisheries, it was questioned the homogeneity of quarters and large geographical areas strata (Fonteneau 2016) indicating large variability both in species composition as well in the size distribution of these areas (Figure 7). When plotting the overlap between the Ghana P-Fleet and the EU Trop Fleets for the years with sufficient data in both sets ( by month) (Figure 8), it shows that actually the overlap in terms of 5 x5 cells is relative low to medium and varied greatly by season or month. The same information is also presented in terms of a mosaic plot type (Figure 9), where by year-month the shade colors represent the number of overlapping 5x5 cells between the two fleets (Ghana P-Fleet and EU PS), dark colors indicate high overlapping while light colors indicating low overlapping. Overall, in these 3 years, 51% of 5x5 strata did not overlap in terms of catch/effort by the EU and Ghana P Fleet, 18% of cells show catch/effort by EU fleet exclusively and only 31% did overlap. These questions if applying averages from large geographical areas is appropriate for estimating the catch composition and size distribution of a fleet that have rather different patterns of operation compared to the EU PS fleets. In prior estimations, it was assumed that the spatial distribution (quarterly) from the 2012 logbook information of the Ghana P-Fleet was the same for prior years (2006, ) (Chassot et al. 2016). Again, the 3 years of good logbook data from this fleet actually suggest that there are significant differences in catch and fishing effort distribution by year month for this fleet. Thus in the case of yellowfin tuna, the estimation of spatial and temporal distribution of the catch for the Ghana P-fleet was modified, instead of using wide areas, the catch was allocated in 5 x5 square grid areas and by quarter. As all missing catch was assigned to the P-Fleet operating on FADs, it was determine if there were sampling from a Ghana fleet in the strata: fishing mode (Free school or FADs), gear (PS or BB), quarter (Jan- Mar, Apr-Jun, Jul-Sep, Oct-Dec), and 5 x5 square lat-lon, or from the EU fleet. Essentially, the overlapping of the catch/sampling on 5 x5 grids, if Ghana operations were in a given grid, both the percent of catch composition and the size distribution of sampled YFT were used, if only catch/sample from the EU fleet, then the catch composition and YFT size distribution were used. Size samples were considered sufficient if at least 75 fish were measured from a given cell. There were cells were catch was realized but not size samples were available, in this case a substitution scheme was applied, where samples from the same quarter and nearest 5x5 grid was used, in few instances it was required to expand to other quarters and or larger areas (Ghana geographic areas) due to lack on data particularly in the early years. This scheme gives priority to the data available in the smallest resolution, rather than applied large areas averages. This scheme has similar approaches as suggested in a recent proposal for reviewing the EU T3 treatment of catch composition and size distribution for their EU PS fleet (Fonteneau 2016). 3.3 Size frequency distribution of the yellowfin catch Size sampling was reviewed and considered sufficient to estimate the size distribution of the catch for the Ghana A-fleet, size samples were aggregated in the cell strata defined before, e.g. by fishing mode, gear, quarter, and 5 x5 square degree area. If 75 or more yellowfin fish where measured, it was estimated the size probability density function in 2 cm intervals for standardized fork length measurements (FL). Larger fish are sometimes reported as measurements of the first dorsal length (LD), all these were converted to standard FL using the current size conversion factors. Size sampling was reported without extrapolations, for the Ghana industrial fisheries overall more than 200 thousand YFT were measured from 2006 to Next step was to estimate the catch-at-size for the whole Ghana YFT catches. In this case, the size frequency samples in the same strata as the Catch-Effort was extrapolate to add to the total YFT catch for Ghana purse and baitboat fisheries estimates (Task I). The same substitutions rules as for estimating size frequency were applied, briefly if size samples were available from Ghana size sampling (AVDTH Ghana) were used it, if not then size frequency probability density functions (pdf) from the EU fleets were used for the same strata year, quarter, fishing mode, gear and 5x5 area, in case size pdf s were not available, then near 5x5 areas were assigned or in the general case an overall year-quarter Ghana area were used when no other data was available. 485

5 4. Results and Discussion 4.1 Estimates of total Task I Table 3 presents the comparison between the total tropical tuna catches for Ghana from the reported catches (logbook records) and the reported landings (sale records) from the AVDTH db. As suggested the maximum of these values should be considered the best estimates of total landings. For 2006, 2008, 2010 and 2011 the landing from sale records are the highest reported catches for all species, while for 2009, 2012, 2013 and 2014 the catches from logbooks are greater. For the Ghana Fleet P, landings generally provide more complete information on the total catch compared to the logbook data (Chassot et al 2015) (Figure 10). In contrast, for the Ghana national Fleet A, the logbook data exceeds the total landings computed from the information collected through sale records to canneries. Noticeable, the total catch of the industrial Fleet A decreased in 2013 (32%) and 2014 (34%) compared to , although the number of active vessels remained relative constant during this period. On the other hand the catches from the industrial Fleet P increased in 2013 (18%) and 2014 (47%), compared to The total catch of the Fleet P is very sparse and low prior to Overall, for Ghana industrial fishing fleets the catches of tropical tunas have oscillated between 67 and 78 thousand tons between 2009 and During the same period ( ) the catches of Yellowfin average 14% of the total tropical tunas (Table 6) with a noticeable increasing in 2014 up to 11.6 thousand t, reversing the decreasing trend of catches from prior years. By gear, catches from the purse seine fleet have substantially increased in proportion to the baitboat catches, for all tropical species, accounting for about 76% of the total tropical tunas in the latest years ( ). Similarly, the catches on FADs have increased in proportion to the catches on free-schools. For yellowfin in , about 80% of the catches were on FADs. Figure 11 shows the nominal trends of CPUE from the Ghana fleets by main gear type and fishing mode. Overall the baitboat CPUEs show a decreasing trend in the latest 4 years, by contrast the CPUE of purse seine on free schools shows an increase recently while the CPUE of purse seines on FADs is rather stable through the time period. Also, as indicated previously the percent of successful sets is rather high, above 90% suggesting under reporting of null sets. Table 6 summarizes the proposed total YFT catch for the Ghana commercial fleets for , excluding Table 7 shows the estimated catch-at-size (CAS) for yellowfin tuna industrial fleets (PS and BB) for (Figure 12). The YFT median size distribution is primarily of fish of about 48 cm FL for fish caught on FADs, and 52 cm FL for fish from free-schools (PS). However the size range is quite large, with fish from 24 cm up to 192 cm FL, but 90% of the fish caught is between 36 and 78 cm FL. It is important to note that estimations of YFT catches, involved the review and estimation of the other tropical tuna species; SKJ, BET and other species (bycatch). Hence, for consistency purposes Task I and Task II estimates for these species from differ from prior analyses and would require review and standardization by the Tropicals working group. The estimates of YFT Task I and Task II were used as input for the different assessment models of the YFT assessment 2016 as agreed by the working group. Final decision on the Ghana official catch fishery statistics will require the approval and decision from Ghana statistics delegate and the SCRS. References Anon Report of the 2016 ICCAT yellowfin tuna data preparatory meeting (San Sebastian, Spain March 7 to 11, 2016). Collect. Vol. Sci. Pap. ICCAT in press. Chassot, E., S. Ayivi, L. Floch, A. Damiano and P. Dewals Updating of Task I and II for Ghanaian industrial tuna fisheries data Collect. Vol. Sci. Pap. ICCAT 71(1): Chassot, E., S. Ayivi, L. Floch, A. Damiano and P. Dewals Estimating Ghanaian purse seine and baitboat catch during : input data for 2015 bigeye stock assessment. Collect. Vol. Sci. Pap. ICCAT 72(2): Pallares, P and C. Petit Tropical tunas: New sampling and data processing strategy for estimating the composition of catches by species and sizes. Col. Vol. Sci. Pap. ICCAT 48(2):

6 Table 1. Nominal YFT catches (t) from the Ghana AVDTH database by gear, fleet, vessel unit and year ( ). These represent the records from logbooks, prior to any species and size composition adjustments. Highlighted yellow cells represent vessels without reports for 2014, and in orange first report of catches by this vessel unit. Sum of yft t Year flag gear Fleet vessel_unit Ghana BB Fleet A Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID 7 4, Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID , Vess ID Vess ID Vess ID Vess ID Vess ID Vess ID BB Total 9, ,939 6,121 6,333 6,729 5,774 4,521 5,724 PS Fleet A Vess ID Vess ID Vess ID , ,910 Vess ID Vess ID ,666 1, Vess ID , ,045 Vess ID ,514 1,385 1,164 1, Vess ID Vess ID 42 1,224 1,488 1,044 1, , Vess ID ,625 1, Vess ID Vess ID Vess ID , Fleet P Vess ID ,105 1,727 Vess ID , ,352 Vess ID Vess ID Vess ID ,031 Vess ID ,310 PS Total 3,240 1,155 5,007 8,280 9,876 7,596 10,697 9,400 12,399 Grand Total 12,599 1,999 11,946 14,401 16,209 14,325 16,470 13,921 18,

7 Table 2. Nominal landings (t) from the Ghana AVDTH database by gear, species and year ( ). These represent the Sale Records, prior to any species and size composition adjustments. landings t Year Gear Spp BB BET 650 3,527 4,281 2, YFT 7,506 5,722 7,432 4,581 2,997 3,451 1,868 3,686 SKJ 17,838 13,175 14,342 11,951 9,801 17,108 10,275 7,604 Others 2,978 2,836 1,229 3,064 3,561 2,025 1, BB Total 28,972 25,259 27,284 21,733 16,574 22,812 13,513 11,855 PS BET 1,092 4,881 6,471 4,627 4,225 2,684 1,629 1,403 YFT 4,520 7,262 10,923 7,929 7,757 5,790 4,264 6,337 SKJ 13,260 20,943 21,552 41,858 40,562 40,592 22,376 15,850 Others 1,730 2, ,719 1,461 3,452 2,527 1,922 PS Total 20,601 35,138 39,405 56,132 54,005 52,517 30,795 25,511 Grand Total 49,574 60,396 66,689 77,865 70,578 75,329 44,308 37,366 Table 3. Comparison of total Ghana removals between the reported catches (logbook records) and the reported landings (sale records) from the AVDTH db. Highlighted cells represent the maximum values between the series and as agreed the Total Preliminary Task I NC, excluding Catches t from logbook AVDTH db Ghana 2006 /14 Landings from sale records AVDTH db Ghana 2006 /14 year YFT SKJ BET OTH TOTAL year YFT SKJ BET OTH TOTAL , ,599 30, ,023 44, ,025 31,097 1,742 4,709 49, ,999 4, , ,946 26,046 1,277 1,606 40, ,984 34,118 8,408 4,888 60, ,401 46,109 3,785 4,491 68, ,355 35,894 10,752 1,688 66, ,209 34,294 3,621 4,689 58, ,510 53,809 6,765 4,782 77, ,325 33,909 1,999 3,181 53, ,479 50,363 4,440 5,297 70, ,470 54,264 4,468 3,011 78, ,240 57,699 2,914 5,476 75, ,921 48,131 2,963 1,673 66, ,132 32,651 1,809 3,717 44, ,123 48,741 4,024 2,006 72, ,022 23,453 1,529 2,362 37,366 Table 4. Nominal catches (t) from the Ghana AVDTH db by fleet and gear. total_catches t Ghana Fleet gear Fleet A BB ,062 3,139 22,330 27,809 22,035 24,824 23,920 16,796 16,674 PS ,781 4,111 18,040 35,533 35,833 26,829 27,927 18,663 17,529 Fleet A Total 1,195 43,843 7,250 40,370 63,342 57,868 51,653 51,847 35,459 34,202 Fleet P PS , ,761 26,366 31,229 38,691 Fleet P Total , ,761 26,366 31,229 38,691 Grand Total 1,195 44,502 7,250 40,875 68,786 58,813 53,414 78,213 66,688 72,

8 Table 5. Summary of catches (t) and fishing effort (fishing days) for Ghana fleets by gear and fishing mode. gear fishing mode year total catches2 yft skj bet fishing day nb total sets nb pos sets BB fad fsc PS fad fsc und Table 6. Proposed estimates of total YFT catch (t) for Ghana fisheries (except 2007). YFT All spp Total YFT Total Catch year BB PS BB PS ,256 3,641 31,062 18,511 12,897 49, ,351 6,151 22,330 38,066 11,502 60, ,801 6,236 27,809 40,977 11,037 68, ,602 6,855 22,035 55,617 10,457 77, ,855 4,821 24,824 45,754 8,676 70, ,233 6,357 23,920 54,293 9,591 78, ,336 6,450 16,796 49,892 8,786 66, ,766 8,885 16,674 56,220 11,652 72,

9 Table 7. Estimated Ghana purse seine and baitboat fisheries catch-at-size (CAS) for Size FL

10

11 Figure 1. Spatial distribution of size samples from the EU-PS fleet by area. Areas represent the EU geographical distribution used for estimating catch composition and size distribution of catches. Figure 2. Spatial distribution of catch/size samples from the Ghana fleets (AVDTH) by geographic areas as defined for BET 2015 estimation. 492

12 Figure 3. Spatial distribution of catches of tropical tunas from the Ghana fleet P Data from the AVDTH Ghana program. 493

13 Figure 4. Monthly spatial distribution of catches from the Ghana P fleet from Data from the AVDTH Ghana program. 494

14 Figure 5. Spatial distribution of tropical tuna catches (t) by the Ghana P fleet Data from the AVDTH Ghana program. Figure 6. Spatial distribution of fishing effort (fishing days) by the Ghana P fleet by quarter Data from the AVDTH Ghana program. 495

15 Figure 7. Spatial distribution of yellowfin size samples by gear from the EU fleet Shade colors indicate strata where more the 75 fish were sampled (red). Figure 8. Spatial distribution of catches from EU_Trop fleets and the Ghana P fleet by year-month Shade colors indicate whether in a given cell there were catches from both or only one fleet type. 496

16 Figure 9. Mosaic plot of the overlapping between catches from the EU-Trop fleets and the Ghana P fleet by year (column) and month (row) Low values indicated low number of 5 x5 grids were both fleets coincided. Figure 10. Summary of the Ghana AVDTH db Top-left: Catch (t) by year, top-right: Number of vessels with catches Ghana all fleets by main gear, bottom-left: Number of annual reports of catches, bottomright: comparison of YFT catch reported by AVDTH and ICCAT Task I (Mar-2016) for Ghana. 497

17 Figure 11. Nominal CPUE (total catch per fishing day) from the Ghana fleets AVDTH db Figure 12. Size frequency distribution of the estimated YFT CAS for the baitboat and purse seine Ghana fisheries