Recent Submissions

  • Tuna Data Collection and Processing in Mauritius.

    Norungee, D.; Munbodh, M. (IOTC, 1998)
  • Statistics of the purse seine NEI fleet in the Indian Ocean.

    Pallares, P.; Delgado de Molina, A.; Pianet, R.; Ariz, J. (IOTC, 1998)
  • Which tuna research in Indian Ocean?

    Fonteneau, A.; Marsac, F.; Pianet, R.; Stequert, B. (IOTC, 1998)
  • Review and research plan on the stock structure of yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus) in the Indian Ocean

    Nishida, T.; Chow, S.; Grewe, P. (IOTC, 1998)
    Yellowfin and bigeye tuna are the most important tuna species in the Indian Ocean, this paper reviews the stock structure of these two species and describes research plans based on the review.
  • Preliminary analysis of billfish catch rates in the Indian Ocean.

    Campbell, R.A.; Tuck, G.N. (IOTC, 1998)
    Due to the general lack of targeted fisheries on billfish, the resource status of these species within the Indian Ocean has not been analysed in any previous study and currently remains unknown. Nevertheless, significant quantities of billfish are caught annually in the Indian Ocean and, being generally long lived, these species remain vulnerable to overfishing. In this paper preliminary indices of stock availability are presented for the main billfish species based on the catch and effort data pertaining to the Japanese and Taiwanese Indian Ocean longline fisheries. While the indices need to be treated with some caution (due to problems relating to the accuracy of the catch and effort data, and the fact that changes in catchability have not been factored into the analyses), the declines observed in the indices for black marlin, striped marlin and sailfish/spearfish warrant further investigation. In particular, further effort needs to the put into accounting for changes in targeting practices and the other changes in the fishing gears used.
  • Standardization of catch per unit of effort for swordfish and billfishes caught by the Japanese longline fishery in the Indian Ocean.

    Uozumi, Y. (IOTC, 1998)
    In the present analysis, CPUEs of swordfish and billfishes are standardized with fine-scale statistics to eliminate some possible biases in the CPUE trend which may be introduced by the factors mentioned above.
  • Updated standardized CPUE of bigeye caught by the Japanese longline fishery in the Indian Ocean.

    Okamoto, H.; Miyabe, N. (IOTC, 1998)
    The catch per unit of effort (CPUE) of bigeye caught by the Japanese longline fishery in the Indian Ocean was standardized up to 1997 using general linear model (GLM) analysis. Standardized CPUE in the tropical area, which was relatively stable, ranged from 6 to 8 fish per 1,000 hooks in 1979-1987 and decreased continuously to about 4 in 1997. In contrast, CPUE in the southern area did not show the stable trend of the tropical areas, especially after 1990. This unstable CPUE pattern in the southern area in recent years seems to be derived mainly from the shift of targeting in longline operations. If the trend derived from analysis for 1952-1976 is included, current CPUE is estimated to be about 33 % of that in 1954.
  • Title Stock assessment on the Indian Ocean albacore tuna.

    Chen, C.Y. (IOTC, 1998)
    This paper deals with the CPUE trend and maximum sustainable yield (MSY) of Indian Ocean albacore tuna. The daily catch records of Taiwanese longliners operated in the Indian Ocean dating back to 1979 were used in this study. Deep longline techniques were introduced in the tuna fishery in the mid-1980s and an effort was made to segregate the statistics of regular longliners from those of deep longliners. A general linear model (GLM) was adopted to standardize the CPUE for data of both time periods, 1979- 1985 and 1985-1996. A surplus production model was employed to estimate its MSY and optimum effort (fopt), and the results revealed that, MSY=30.5x103 t; = 319 x 106 effective hooks.
  • Estimation of the catch-at-age matrix of yellowfin tuna (Thunnus albacares) fisheries in the Western Indian Ocean.

    Nishida, T. (IOTC, 1998)
    This is a preliminary paper. There are many different types of gears in many different countries in the western Indian Ocean. As it was sometimes difficult to contact persons-in-charge of the fisheries statistics, not all the description of this paper (such as gear categories, classification and etc) could be checked by them.
  • Trends in the Seychelles tuna fishery.

    IOTC (IOTC, 1998)
    Distant water fishing nations (DWFN) began longlining for tuna in the Western Indian Ocean (WIO) in the early 1950s, initiated by the Japanese soon followed by the Taiwanese (1954) and Koreans (1960). Large scale industrial purse seining began in 1983 when the French and Spanish fleets moved into the Western Indian Ocean from the tropical Atlantic. By 1986 some 6 % of the world tuna catch (143,099t out of 2,400,000t) was coming from the WIO purse seiners; by 1997 this had risen to 14 %. Virtually all the purse seiners active in the WIO are licensed to fish in the Seychelles EEZ; SFA's data therefore reflect the entire WIO purse seine catch (based upon daily catch and effort reports or logbooks which must be provided to SFA by all licensed vessels). At present about 58 vessels per year are licensed. SFA has detailed reports of over 90 % of their total transhipments used to calculate accurate catch figures by correcting estimated catch. Not all licensed longliners provide SFA with catch and effort forms and almost none of those which report catches actually tranship in the Seychelles. In 1985 some 95 % of the WIO purse seine catch was transhipped through Port Victoria; ten years later in 1994, this changed to 60 % of the WIO purse seine catch and, for the first semester of 1998, only 35 % of the total purse seine catch was transhipped in Port Victoria. This reflects a change in the geography of the fishery. In the early 1980s, Mahé was at the centre of the area fished all year round. Purse seiners fish predominantly in the Mozambique during the second quarter of the year and tranship in Antsiranana. Many vessels fish off the Somali coast in the third quarter and tranship in Mombassa. During the fourth quarter of the year, purse seine fishing activities tends to shift from the Somali basin to the Chagos area. By the end of 1997, most vessels moved to the eastern Indian Ocean past the Chagos Archipelago and were transhipping their catch in Phuket, Thailand. A semi-industrial monofilament longline fishery started in Seychelles in October 1995. At present, 6 local longliners are fishing. Swordfish is the targeted species (around 60 %), followed by yellowfin and bigeye tuna. One major problem faced by this fishery is the lost of catch due to predation by marine mammals. The major tuna and tuna like species discussed in this report are: yellowfin (Thunnus albacares), skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus) and swordfish (Xiphias gladius).
  • Bycatch in the purse seine tuna fisheries in the western Indian Ocean.

    Romanov, E.V. (IOTC, 1998)
    The yield of associated and dependent species taken as bycatch by the purse seine tuna fishery from the Indian Ocean pelagic ecosystem is estimated from data collected by scientific observers aboard Soviet purse seiners in the Western Indian Ocean (WIO), 1986-1992. A total of 494 sets on free swimming schools, whale shark associated schools, whale associated schools, and log associated schools were analyzed. More than 40 fish species and other marine animals were registered. Among them only two species, yellowfin and skipjack tunas, are target species. Average levels of non-tuna bycatch equal 0.518 t per set, 27.2 t for 1,000 t of target species. By the author’s estimates, the annual catch of yellowfin and skipjack tunas in 1990-1995 of the total international WIO purse seine fishery was within the range 215,000-285,000 t. The annual non-registered catch included 1,700-2,300 t of pelagic oceanic sharks, 1,300-1,700 t rainbow runners, 1,250-1,650 t dolphinfish, 900-1,200 t triggerfish, 200-270 t wahoo, 190-250 t billfishes, 100-130 t of mobulas and mantas, 60-80 t of mackerel scad, 15-25 t of barracudas, and 120-160 t of other fish; bycatch of turtles and whale mortality were possible. Absence of bycatch records in purse seining does not make it possible to assess, to the full extent, the impact of the fisheries on the pelagic ecosystem in the Indian Ocean. The first step to the solution of this problem is for the Indian Ocean Tuna Commission to develop a system of scientific control over tuna purse seine and longline fisheries by means of a wide network of Commission scientific observers on board fishing vessels in the area.
  • Statistics of the Spanish Purse Seine Fleet in the Indian Ocean.

    Pallares, P.; Delgado de Molina, A.; Ariz, J. (IOTC, 1998)
    This document contains summary statistics of the Spanish purse seine fleet fishing in the Indian Ocean, as well as some information about how the data are collected. The sampling scheme, the sampling coverage, maps and diagrams representing the fishing pattern of this fleet by time and area strata are presented.

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