Overview of Taiwanese Observers Program for Large Scale Tuna Longline Fisheries in Atlantic Ocean from 2002 to 2006

Transcription

1 Overview of Taiwanese Observers Program for Large Scale Tuna Longline Fisheries in Atlantic Ocean from 02 to 06 Hsiang-Wen Huang 1, Shih-Chin Chou 2, Ju-Ping Dai 3, and Chih-Hao Shiao 3 1 National Taiwan Ocean University, Keelung 2 Fisheries Agency, Council of Agriculture, Taipei 3 Overseas Fisheries Development of Council, Taipei ABSTRACT For collecting fisheries data for scientific purposes, Taiwan started to deploy observers on distant water fishing vessels since 02. Observers were trained to collect fisheries data and biological samplings. The data recorded include the fishing activities, catch number and weight, species identification, bycatch species, status and biological samples for some species. This report provides a general overview of the Taiwan observer program and summary of data collected. From 02 to 06, 35 trips on large scale tuna longline fishing vessels were observed in the Atlantic Ocean. The observations days were 4,755, with an average coverage rate of 5.33% by trips. More than 21 species were recorded, and 282,621 fishes were sampled. The catch composition varied by areas. In tropical area, over 36% of catch were bigeye. In temperate waters, the albacore accounted over 80% in the northern area, and 87% in the southern area. In addition, length frequency of major species and the sighting and incidental catch of ecological related species were recorded, and biological samplings were collected for biological research. 1. INTRODUCTION Large Scale Tuna Longline Fisheries Taiwan started to fish tuna and tuna-like species in the Atlantic Ocean since early 1960s. During those days, the fishery targeted on albacore and yellowfin, and ever since the development of deep-longline operations in the late 1980s in the tropical Atlantic Ocean, some of the fishing efforts were shifted to target mainly on bigeye. The number of vessels in the longline fishery has declined from 176 in 02 to 119 in 05. As a special measure made in light of Recommendation 05-02, 15 vessels were authorized to target on bigeye tuna and 60 fishing vessels authorized to target on albacore. In other words, the number of authorized fishing vessels to fish in the Atlantic Ocean in 06 was 75 in total.(table 1) Albacore, bigeye and yellowfin constituted of more than four fifth of the annual catch in the recent years (Table 2). Bigeye and yellowfin are mainly caught in the area between 15 N and 15 S. Higher composition of albacore has been observed in the area north of 15 N and in the area south of 15 S. Swordfish is mainly a bycatch species to the fishery. Simultaneously as a result of this derogation of the normal catch limit, there has been a decline in the overall catches by the fishery, there has been a decline in the overall catches by the fishery, from about 49,076 t in 02 to 23,686 t in 06 (Table 2). Observer Program Noting the importance of fisheries dependent data for scientific purposes, Taiwan launched a pilot observers program on distant water fisheries since 02. In the first year, there were only 5 observers for all oceans. In line with the government s policy in establishing an observers program on a global basis, and availability of budgets to support the increase of observers, the number of observers employed gradually increased and reached 56 in 07. The annual budget was US$ 166 thousand in 02 and increased to US$ 1,978 thousand in 07 (Table 3), covering such expenses as the salary of observers, food, travel fees, sampling facilities, communication costs and administrative fees, etc. 1

2 For smoothly implementing the observer program, the fishing vessel owners, captains and crews are requested to cooperate and assist the observers for conducting their missions, which include allowing the observers to access to the satellite telephone, fax machine, internet and any other communication facility independently and assisting observers to collect samples on designated target and non-target species, etc. Captains or crews are obligated to answer questions of observers in relation to their work. 2. PROGRAMS ARRANGEMENT Vessel selection Due consideration was taken on the requirement of the measures in place by various RFMOs when deploying observers. Stratification was made according to fleet types (such as bigeye fleet and albacore fleet). At the outset, taking observers on board was in a voluntary basis. As an incentive, additional quota was provided to those vessels which has catch quota limit. Later, ballot would be applied to the entire fleet, in a rotation basis. In 06, it became mandatory for fishing vessels to accept an observer onboard. There will be no additional quota for observed vessels. However, if the vessel would be cooperating with Fisheries Agency for special experiment, additional quota could be considered on case-by-case basis. Missions To implement the scientific missions, three weeks training course are designed for observers. There are five major parts which included the understanding of the relevant fisheries management policy and regulations, knowing the facility of fishing vessels, learning how to record catch information, practicing the techniques of biological sampling and knowledge of the Health and Safety onboard. While onboard, observers shall record the following information, (1) Basic information of the vessels: the vessel s name, tonnage, vessel length, number of crew, the type of communication system, etc. (2) Daily fishing activities information: gear characteristics, set and retrieval time, environmental conditions, bait types, total number of hooks, total number of baskets, hooks per baskets, etc. (3) Catch information: identification and record catch species, measurement of length and weight for first sixty fishes, the number and weight of each catch species. In addition, the sex should be recorded for some species (billfishes and sharks). (4) Bycatch information: many bycatch species were released before taken onboard. If those bycatch species were dead taken onboard, observers are requested to take some biological samples for further researches. (5) Biological samples: otoliths, stomach contents, muscle and vertebra were collected for some species. Weighting of the whole shark and shark fin for obtaining shark fin ratio estimation. Data summarization Every observer is provided with a laptop with electronic observer data system, for daily entry of observation data. After the observer completes his mission and returns home, there will be a debriefing between observer and observers manager. Then the data will be checked twice by other observers off duty. Upon completion of the checking, the data will be submitted to statistician for analysis. The data will be released to managers and scientists when requested. 2

3 3. Data Summary Trips information A total of 35 trips were deployed in Atlantic Ocean from 02 to 06. The observation days were 6 in 02 and increased to 3,178 in 06. Total of 4,662 fishing days were recorded, with the total efforts of 15,246 thousand hooks, ranging from 641 thousand hooks in 02 to,034 thousand hooks in 06. The overall coverage rate was 5.33 % by trip. It was 1.7 % in 02 and increased to 21.3 % in 06. The average observer days for a trip were 133 days. The detail information was listed in Table 4. It shows increasing trend in observer efforts, days, and trips from 02 to 06. Observation areas In Atlantic Ocean, there are three fishing grounds, which are the tropical area (15 N-15 S) for bigeye tuna fishing vessels, north area (15 N-45 N) and south area (15 S- S) for albacore fishing vessels. The observation areas are showed in Figure 1. Around 77% of the observation area was in the tropical areas, with only 23% in south area and the remaining in south area. Catch composition Catch composition by areas were showed from Figure 2 to Figure5. More than 21 species were recorded, including 3 tuna species, 7 tuna-like species, 8 shark species, and 2 species of other fishes. Among them, five species were of commercial valuable, including bigeye, albacore, yellowfin and blue shark. These species covered more than 80% of the total catch,.0% of albacore, 23.6% of bigeye, 5.5% of yellowfin and 12.0% for blue shark. The diversity of shark species is quite high in the tropical area. The three major tuna species catch composition by 5 5 degree is shown in Figure 6. It is obvious that the species compositions varied by areas. In north area, over 80.5% were albacore, 6.7% bigeye, 4.7% blue shark and 3.2% other fisher. In tropical area, over.7% were bigeye, 18.1% blue sharks, 8.9% yellowfin and 5% albacore. In south area, albacore accounted for 86.5 %, 3.8% blue shark, 0.7% bigeye and 1.1% yellowfin. Length Frequency Observers recorded length and weight for target species and bycatch species if possible. During the observer trips, around 58,000 samples were measured, included 45,815 albacore, 52,477 bigeye, 12,0 yellowfin, 7,232 swordfish and 27,971 blue shark. The length frequency of albacore ranged from cm to 1 cm. We separated the length frequency to north stock and south stock. The modes were 96 cm and 98 cm for north and south stock respectively. It showed the average size was smaller in north area. The length frequency of bigeye ranged from 70 cm to 2 cm and averaged cm, the mode was 1 cm. The length frequency of yellowfin tuna ranged from 72 cm to 190 cm and averaged cm. The mode was 1 cm. The length frequency of swordfish ranged from 80 cm to 274 cm and averaged cm. The modes were 1 cm and 1 cm. The length frequency of blue shark ranged from 86 cm to 357 cm and averaged cm. The mode was 2 cm. Ecological species interaction and incidental catch Many ecological related species, such as seabirds, sea turtles, cetacean and others, are known to have interaction with tuna longline fisheries. The observers recorded the species sighted as shown in Table 5. Fourteen species of seabirds, five species of sea turtles and more than five cetaceans are sighted. The seabird has higher diversity in south area. The cetaceans and sea turtles have more concentrated in tropical area. However, because most of the ecological related species were sighted from far distance, some species could not be identified. In addition, the incidental catch also became important tasks for observers. During the trips, 419 sea turtles, 133 albatrosses and other seabirds, 27 cetaceans were incidentally caught. It showed the seabird was bycatch in south of S. The cetaceans were bycatch in tropical area. Most of the sea turtles were incidental catch in tropical areas, but there small numbers were caught in temperate areas. 3

4 Biological and other researches Biological studies were done using the biological samples collected by observers. Specific experiments required observers cooperation, which included the following, (1) Research on Swordfish stock structure between Indian Ocean and Atlantic Ocean. Swordfish meat samples taken by observers were used for identification on Atlantic Swordfish Stock Structure inferred by Mitochondrial Control Region DNA Sequence Characters. (2) Research on albacore stock structure between Indian Ocean and South Atlantic Ocean Albacore meat samples taken by observers were used for identification on Atlantic and Indian Ocean albacore stock structure inferred by Mitochondrial Control Region DNA Sequence Characters. (3) The stock structure of bigeye in three oceans through DNA analysis A thorough understanding of the bigeye tuna population structure is necessary for the effective management of this highly migratory marine species. The study is to elucidate the existence of these bigeye tuna population stocks inferred from mtdna control region polymorphisms. Tissue samples of bigeye tuna were collected mainly from Western Atlantic, central Atlantic and eastern Atlantic oceans. The population structure of bigeye tuna in the Atlantic Ocean was investigated using sequence data of the mitochondrial control region. (4) Estimation of the shark landing The observers data for shark catch composition were used to estimate the historical landing of Taiwanese fleets. According to shark bycatch rate, the shark catch data reported by observers were used to adjust the historical shark catch in Task I and to estimate blue shark and mako shark catches for Taiwanese longline fishery in the Atlantic Ocean. (5) Estimation the seabirds bycatch According to the data collected, the seabird incidental catch rate (BPUE) were analysed. The average BPUE was per 00 hooks. As for the seabird incidental catch distribution, the BPUE were highest in the areas between S and W and between - S and 5-15 W. On the contrary, the BPUE was low in tropical area. By using the effort data from Task II and the BPUE from observers, the preliminary estimated average number of seabird incidental catch was 936 per year. (6) Experimental analysis on the reduction rate of sea turtle bycatch in tuna longline by using circle hooks 6 commercial fishing vessels were chosen to carry out the experiments of circle hooks in Atlantic Ocean. Some results of the experiments are under analysis. 4

5 Table 1 Number of Large Scale Tuna Longline fishing Vessels in Atlantic Ocean, Year No. of vessels Table 2 Catch of major tuna and tuna-like species caught by LTLL fishery in ICCAT Convention Area, YEAR ALB BET YFT BFT SBF** SWO WHM BUM BIL SKJ OTH SKX TOTAL 02 21,651 18,483 4, , , ,908 21,563 6, , ,803 55, ,566 17,717 5, ,380 44, ,270 11,984 3, ,6 1,455 32, ,6 2,965 1, ,289 2,678 23,686 Table 3 Number of observers and annual budget for observer program, Year No. Budget(US$) , , , , , ,978,879 Total 123 3,7,1 Table 4 Number of vessels covered, observed days and hooks in Atlantic Ocean, Year Trips Days Hooks Total

6 Table 5 Ecological related species sighted Area Sighted species Seabirds Unidentified seabird North Sea turtles Loggerhead turtle, Hawksbill sea turtle, Leatherback sea turtle Cetaceans Bottlenose dolphin, Blackfish Seabirds Black-footed albatross, Wandering albatross, Unidentified albatross, Unidentified seabird. Tropical Sea turtles Loggerhead turtle, Kemp's Ridley turtle, Hawksbill sea turtle, Leatherback sea turtle, Olive ridley turtle, Unidentified sea turtle Cetaceans Pantropical spotted dolphin, Spinner dolphins, Striped dolphins, Bottlenose dolphin, Blackfish, Unidentified dolphin, Unidentified whale Seabirds Royal albatross, Short-tailed albatross, Yellow-nosed albatross, Black-browed albatross, Wandering albatross, Light-mantled sooty albatross, Chatham island albatross, Sooty albatross, White-chinned petrel, Giant petrel, Southern giant petrel, Spectacled petrel, Cape petrel, Flesh-footed shearwater, Unidentified albatross, Unidentified seabird, South Sea turtles Green turtle Cetaceans Spinner dolphins, Bottlenose dolphin, Pygmy sperm whale, Blackfish, Unidentified whale 6

7 N ALL 0 00 Hooks >= < S W E Figure 1 Distribution of observed fishing efforts, Other sharks Other fishes Blue shark Albacore Skipjack Other Billfishes Swordfush Yellowfin Bigeye Figure 2 Species composition of observed catch in whole Atlantic 7

8 Other Billfishes Swordfush Yellowfin Bigeye Blue shark Skipjack Other sharks Other fishes Albacore Figure 3 Species composition of observed catch in North Atlantic Other fishes Albacore Other sharks Blue shark Bigeye Skipjack Other Billfishes Swordfush Yellowfin Figure 4 Species composition of observed catch in Tropical Atlantic 8

9 Skipjack Other sharks Blue shark Other fishes Swordfush Other Billfishes Yellowfin Bigeye Albacore Figure 5 Species composition of observed catch in South Atlantic W 0 E 02-06,000 5,000 1,000 ALB BET YFT 60 N 0 S N 0 S W 0 E Figure 6 Distribution of the catches of albacore, bigeye and yellowfin tunas in the Atlantic Ocean, in numbers,