Statistics of the purse seine spanish fleet in the Indian Ocean (1984- 2009)

This document presents summary statistics of the purse seiner Spanish fleet fishing in the Indian Ocean from 1990 to 2009. Data include catch and effort statistics as well as some fishery index by species and fishing mode. Information about the sampling scheme and the coverage of sampling, together with maps and diagrams representing the fishing pattern of this fleet by time and area strata is also included. 1Data collection 1-1-Catch and effort Catch and effort data were collected by logbooks. This system, established in the Atlantic Ocean at the end of the 70’s has been implemented in a regular way by most of the Spanish fleet. In the Indian Ocean this system was establish at the beginning of the fishery using the Atlantic system adapted to this Ocean. Since 1984 the coverage of the logbooks have been nearly 100% The basic information of the logbooks is raised trip by trip to unloading data. 1-2-Species composition and sizes Until 1998 the size distribution of catches was obtained using a monospecific sampling. The sampling scheme used was two steps sampling that considered the set as primary unit of sampling and the fish as secondary unit. The samples were taken by species. The sample size was the same for all species. In the Indian Ocean analyses made at the beginning of the fishery showed a systematic bias in the log book species composition. The main bias was related with the small yellowfin, partially declared as skipjack, and small bigeye, always declared as yellowfin or skipjack, then a procedure of counting the fishes according their species composition (during the unloading) was routinely established in order to correct the species composition of the catches. Furthermore, during 1996 and 1997 a large scale research program, called ET, targeting the analysis of the tropical tuna sampling schemes, funded by the European Commission and coordinated by the IEO and ORSTOM, was conducted. At the end of this program a new sampling and statistical procedure to process the data has been proposed in order to improve the accuracy of statistics in the Atlantic and Indian Oceans. This new data processing will be used since 1991 and the new sampling method has been introduced in all the sampling ports in 1999. The correction of the species composition of the catches as well as the estimation of their size distribution was made using the samples taken from all the purse seine fleets combined because the statistical analysis made during the ET project showed that there was not a significant fleet effect. 1 Instituto Español de Oceanografia. PO Box 1373. S/C Tenerife. Spain 2 Oficina Española de Pesca en Seychelles 2 2-Statistics 2-1-Catch Table 1 and figure 1 show the total yearly catches by species and tables 2 and 3 and figures 2, 3 and 4 show catches by fishing mode and species. The total catch in 2009 was 111 951 t, this supposes a decrease in relation with 2008. By species skipjack has been the main component of catch with 66 570 t, while yellowfin and bigeye was 33 511 t and 11 781 t, respectively. As for to the fishing mode, the catch on log was 93 461 t and in free School 18 490 t. Figures 5 to 10 show the distribution of total catch and catches by fishing mode, species and 1ox1o squares for 2009 compared with previous years (2004_2008). Tables 18-19 show catch and effort by FAO area. 2-2-Effort Table 4 and figure 13 show the carrying capacity and number of boats by category of the Spanish fleet, in 2009 a total of 15 Spanish vessels fished in the area. Table 5 and figure 15 show the nominal effort in fishing days and searching days. The effort (fishing days) in 2009 decrease a 21% in relation with 2008. Table 6 and figure 14 show the number of 1o by 1o degree square explored by the Spanish fleet under different filtering criteria. The fishing area has been maintained since 1996. A similar conclusion is reached from the figures 11 and 12 that compare the distribution of effort by 1ox1o squares in 2009with the average of the period 2004 2008. 2-3-Yield Table 7 shows total number of sets and number of sets by fishing mode. The frequency distribution of sets by catch size is shown in Table 8, 9 and 10. Figures 16, 17 and 18 show total number of positives and nulls sets. Tables 11 to 16 show different catch rates by species and fishing mode. 2-4-Mean weight Table 17 and figures 19, 20 and 21 show the mean weight by species and fishing mode, as usual catches on logs have a lower mean weight than catches on free school. 2-5-Length Figures 22, 23 y 24 show 2009 length distribution of yellowfin, skipjack and bigeye, respectively.