DISTRIBUTION OF SEABIRD BY-CATCH USING DATA COLLECTED BY JAPANESE OBSERVERS IN IN THE ICCAT AREA

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1 SCRS/2011/065 Collect. Vol. Sci. Pap. ICCAT, 68(5): (2012) DISTRIBUTION OF SEABIRD BY-CATCH USING DATA COLLECTED BY JAPANESE OBSERVERS IN IN THE ICCAT AREA Yukiko Inoue, Kotaro Yokawa, Hiroshi Minami, Daisuke Ochi, Noriyoshi Sato, Nobuhiro Katsumata 1 SUMMARY The interaction between the pelagic longline fishery and seabirds is considered to have negative impacts on their population levels. Investigating the area and season of high probability of the seabird interactions should provide important information to consider effective by-catch mitigation measures. In our study, distributions of seabird by-catch are presented using data collected by Japanese observers on a voluntary basis in in the ICCAT area. Higher CPUEs of albatrosses, giant petrels and petrels are mainly observed in the area south of 30 o South in April to September, where strict mitigation measures should be introduced. Higher CPUEs of a few petrels and albatrosses were also obtained at the area off Namibia in October to December. Almost no catches of albatrosses and giant petrels were observed in the area north of 30 o S. Although there could be some exceptions, such as in Namibian waters, seabird interactions with Japanese longliners is considered to have minor impacts on the seabird population level there. Our results are thought to be worth discussing the area introducing bycatch mitigation measure. RÉSUMÉ Il est estimé que l interaction ayant lieu entre les oiseaux de mer et les pêcheries palangrières a des effets négatifs sur leurs niveaux de population. Des travaux de recherche sur la zone et la saison présentant les probabilités les plus élevées d interactions avec les oiseaux de mer devraient fournir des informations significatives afin d envisager l adoption de mesures d atténuation efficaces des prises accessoires. Notre étude présente les distributions des prises accessoires d oiseaux de mer en ayant recours aux données recueillies volontairement par les observateurs japonais entre 1997 et 2009 dans la zone de l ICCAT. Les CPUE les plus élevées d'albatros, de pétrels géants et de pétrels ont été principalement observées dans la zone au Sud de 30ºS du mois d'avril au mois de septembre, où des mesures d'atténuation strictes devraient être appliquées. Des CPUE plus élevées de quelques pétrels et d albatros ont également été obtenues dans la zone au large de la Namibie du mois d octobre au mois de décembre. Pratiquement aucune prise d albatros et de pétrel géant n a été observée dans la zone au Nord de 30ºS. Même si des exceptions peuvent exister, notamment dans les eaux namibiennes, il est estimé que les interactions des oiseaux de mer avec les palangriers japonais n ont pas d incidences majeures sur les niveaux de population des oiseaux de mer. Nous estimons que nos résultats peuvent servir aux discussions sur la zone d introduction des mesures d atténuation des prises accessoires. RESUMEN Se considera que la interacción entre la pesquería de palangre pelágico y las aves marinas tiene impactos negativos en sus niveles de población. Investigar el área y la temporada en las que existe mayor probabilidad de interacciones con aves marinas debería facilitar importante información para considerar medidas eficaces de mitigación de la captura fortuita. En nuestro estudio, se presentan las distribuciones de la captura fortuita de aves marinas utilizando datos recopilados por observadores japoneses de forma voluntaria entre en la zona de ICCAT. Las CPUE más elevadas de albatros, petreles gigantes y petreles se observaron sobre todo en la zona al Sur de 30º S desde abril a septiembre, donde deberían utilizarse medidas de mitigación estrictas. Las CPUE más elevadas de algunos petreles y albatros se obtuvieron también en aguas de la zona de Namibia entre octubre y diciembre. En la zona al Norte de 30ºS casi no se observaron capturas de albatros y petreles gigantes. Aunque podría haber algunas excepciones, como las de las aguas de Namibia, se considera que las interacciones de aves 1 National Research Institute of Far Seas Fisheries, Orido 5-7-1, Shimizu, Shizuoka , yuinoue@affrc.go.jp 1738

2 marinas con palangreros japoneses tienen un impacto pequeño en el nivel de población de aves marinas de aquella zona. Teniendo en cuenta nuestros resultados, merece la pena discutir la zona de introducción de medidas de mitigación de la captura fortuita. KEYWORDS By-catch hotspot, seabird by-catch distribution, Japanese observer program, pelagic longline 1. Introduction Seabird by-catch in longline fisheries occurs by the mechanism that seabirds attack baits. It is suggested that this problem causes seabird population decreases (Brothers 1994). From now, many by-catch mitigation techniques are developed and used in several regions (Kiyota 2002, Yokota and Kiyota 2008). Nevertheless, further investigation of data and developments of mitigation measures should be necessary for the coexistence of seabirds and longline fishery since seabirds widely change their composition of species, numbers and aggression, according to regions and seasons. Some seabird species including albatrosses gather around longline fishing vessels, and many bait attacking by diving seabirds are reported in specific fishing ground of pelagic longline such as coastal area around Cape Town (Melvin and Guy 2010). On the other hand, in the North Pacific, the number of seabird species causing interaction with longline baits is rather small and they only conduct moderate attacks on longline baits in compare with the ones in the coastal area of South Africa and attacks by deep diving seabirds do not occur (Sato et al. 2010). Thus, seabird aggression and the by-catch risk would differ among regions. Also, by-catch distribution may change according to phenology because foraging range during chick-rearing period is restricted in order for parents to return to colony for chick provisioning. To investigate the area and season of high probability of the seabird interactions with longline fishery and compare these results with their distribution pattern should bring important information not only for the effective introduction of seabird mitigation measures but also for the progress of the behavioral study of by-caught seabirds. In the last ICCAT meeting, distribution pattern of major seabird species, estimated using data collected by the remote tracking was demonstrated in the comparison with the distribution pattern of lognline fishing effort, and the by-catch risk of the overlap area was pointed out (ACAP 2010). However, because probability of by-catch for each species would depend on the behavioral traits of each species, some species may not be caught even in the overlap area. In our study, distributions of seabird by-catch were presented using data collected by Japanese observers in in the area of ICCAT. For specific species of which population decreased into the concerned level, distribution patterns of CPUEs were described by seasons and the important area to introduce by-catch mitigation measure was discussed. 2. Methods We used by-catch data gathered at longline fishing boats by science observers as volunteers. These data were collected by observers, who had lectured how they handle and take pictures of by-catch seabirds, shipped on the fishing boats whose skippers agreed with. They roughly classified the seabird group according to the species identification guide for the pelagic longline fishery (Nakano 2002) on the boat, and species were identified by scientists of National Research Institute of Far Seas Fisheries using their pictures taken by observers. We took the older classification system for the species identification of albatrosses because of the distinction difficulty of some albatrosses isolated as species in most recent years. Using these data, the number of by-catch seabirds was aggregated into grid of latitude 5 degree and longitude 5 degree. And also, to get the probability of by-catch per 1000 hooks (CPUE) at the grid, the numbers were divided by number of hooks and made 1000 times. For albatrosses, giant petrels and petrels, the CPUE distributions at January-March, April-June, July-September and October-November were computed. We also computed the same distribution for particular the species of which population level decreased at concerned level and of which by-catch was high. 1739

3 3. Results Procellariiforme seabirds caught by the longline sets monitored by the observers in ICCAT area during were 2 genus, 9 species, 309 individuals of albatrosses, 1 genus, 2 species, 34 individuals of giant petrels, 3 genus, 5 species, 106 individuals of petrels. Total number of by-caught seabirds was 502 individuals (Table 1). During 13 years, seabird by-catch data in 4601 fishing operations were collected by observers. In January to March, data were obtained from the temperate area in the northwestern and central Atlantic as well as from the tropical area in the eastern Atlantic, in April to September they were collected from the temperature area in the northern Atlantic and off south African waters, and in October to December they were done in northern Atlantic and coastal area off Namibia (Figure 1). About all of seabirds, the area of CPUE over 0.05 do not exist in January to March (Figure 2). In April to September, high CPUE area concentrated at shore off Cape and the area of CPUE over 0.3 existed at south of 30S (Figure 2). In October to December, the area of CPUE over 0.1 were appeared at off Namibia, off Western Sahara and off North Carolina (Figure 2), which were result from by-catch of white-chinned petrels, Northern gannet and gulls, respectively. The number of by-caught Northern gannet at off Western Sahara and by-caught gulls at off North Carolina were small (Both under 10 individuals). CPUE of albatrosses concentrated in the area at south of 30S and east of 0E, including coastal area around Cape Town in April to September, but they were not appeared other seasons or areas (Figure 3). By-catch of petrels was observed in the same area as albatrosses except for the off Namibian area (25S and 5E), and the level of CPUE was relatively lower than that of albatrosses (Figure 4). By-catch of giant petrels were rarely observed (Figure 5). Few by-catch of Wandering albatrosses was observed in April to September in coastal area around Cape Town but was not observed in other seasons or areas (Figure 6). No by-catch of Black-blowed albatrosses was observed in January to March in all area of ICCAT, CPUE of them was under 0.1 in coastal area around Cape Town in April to September and few were caught in one block in off Namibian waters (25S and 5E PCUE<0.05) (Figure 7). CPUE of Grey-headed albatrosses was showed under 0.3 at south of 40S in April to September but no by-catch of them was observed in other season or area (Figure 8). CPUE of Grey petrels appeared under 0.3 at 0E in April to September and did not appear in other seasons, areas (Figure 9). CPUE of White-chinned petrels was showed under 0.1 in coastal area around Cape Town in April to June while by-catch of them was merely observed in January to March and in July to September, and was observed only in the area off Namibia in October to December (Figure 10). 4. Discussion A total of 13 years of seabird by-catch data collected by Japanese observers seems to cover major tuna fishing ground in the Atlantic for each season of the year, except for the off south American waters and coastal area of the northwestern Africa where no observer data available. Amount of effort monitored by the observer should also be high enough to demonstrate the actual condition of seabird by-catch in each tuna fishing ground. There will be no problem at poor coverage of data in the central area of the north and south Atlantic because there could be attributed to the low fishing activity in these areas. Distribution pattern of CPUE by species obtained in this study does not always match with the distribution probability of corresponding species estimated by tracking data (ACAP, 2010). The observed differences between two patterns could be due to the fact that observer data does not cover whole distribution area of seabird as well as the fact that intentionality to feed longline baits changes by species, area and season. This indicates that the definition of the area to introduce seabird mitigation measures should be better to be decided not based on the distribution probability of seabirds but based on the CPUE distribution. The CPUEs of Wandering albatrosses and White-chinned petrels obtained in this study show similar distribution patterns to their distribution probabilities estimated by tracking data, which agree with the tracing data (ACAP, 2010). Wandering albatrosses, though of which CPUE was small, and white-chinned petrels seem to gather and forage around fishing boats in foraging range. On the other hand, although distribution by tracking data in Yellow-nosed albatrosses overlapped the area where longline fishing boat operated, the number of by-catch was only 3 individuals (Table 1). Also, though distribution of Cory's albatross overlapped the area where longline 1740

4 fishery boat operated, and by-catch of them appeared in the Mediterranean sea (Barcelona et al. 2009), they never appeared in in the ICCAT area (Table 1). By-catch of these seabirds could be smaller compared with the other species even though the distribution area overlapped the area where fishery boats operate. Although overlap between the distribution of Cory's shearwaters and the fishing area was pointed out (ACAP 2010), by-catch of them never appeared, which indicated that they would be interested in neither fishing operation nor baits. There are colonies of Cory's shearwaters in North Atlantic (Onley and Scofield 2007) but their by-catch did not appear and by-catch of other petrels also merely appeared in the north Atlantic, showing that additional mitigation measure or mitigation measure itself will be not need at least for Japanese longliners. Phenology of seabirds could be one of the factor controlling foraging range. In general, albatrosses and petrels breed biennially or annually in a colony in ocean islands and incubate an egg. Chick rearing period last for 7-14 months and in this period, they need return to their colony to feed on their chick, resulting in decreasing foraging range. However, the foraging range of larger albatrosses tends to be wide after middle of chick rearing period. According to these traits, foraging range of larger albatrosses, which was restricted only during early chick-rearing period, would be not so influenced by their phenology compared with petrels, which are restricted their foraging range during all of chick rearing period. From our result, some albatrosses and petrels were caught near their colonies but others were caught in areas far from their colonies, which indicate that penology could only partially explain the distribution of the by-catch. Young bird or bird which passed breeding could be caught. Thus, by-catch distributions of each species in detail are needed in order to decide the area to introduce by-catch mitigation measures. In general, foraging ranges of petrels are smaller in chick-rearing period than that of albatrosses is Weimerskirch et al. 1997, Weimerskirch and Cherel 1998, Weimerskirch 1998). The food demand would increase in chick-rearing period because of chick provisioning, might result in higher CPUE than in other periods. By-catch of grey petrels appeared at 45S and 0E, shore off Cape, near their colony in April to September, chick-rearing period. To return for chick provisioning, the parent's foraging range would decrease and food demand would increase so the CPUE was concentrated on there, though the detail is unknown because of lack of data during austral summer there. By-catch of White-chinned petrels appeared in October to December, incubation and chick-rearing period at shore off Namibia, where far from their colonies. Berrowed et al. (2000) showed they forage at pretty wide area; their maximum foraging rage is 8000km in incubation period and 6000 km in colony of South Georgia. Thus, they could forage at shore off Namibia even in breeding period. Additionally, their CPUE decrease in July to September, non-breeding period, indicate that their higher CPUE would concentrate on during breeding period. Albatrosses did not change their distribution very much according to their phenology, which would result from their wide foraging area even in breeding period. By-catch of Black-browed albatrosses appeared in April to December, both in breeding season (April to June) and in non-breeding season (July to September), which indicated that they are possible to be caught in all the season in wide range. By-catch of Grey-headed albatrosses appeared in April to September, when Japanese fishery boat operated, in south of 40S which the tracking data point out as their range both in breeding season and in non-breeding season. Since their by-catch distribution did not changed according to their phenology, they are possible to be caught in all the season in south of 40S and east of 0E. As a result, CPUE of seabird, especially albatrosses and petrels, appeared high in south of 30S. Although the high CPUE were observed in April to September, introducing mitigation measure in particular season is difficult because of lack of data during austral summer there. Examination for by-catch avoidance until now demonstrated that night setting of longline and weighted branch lines are effective (Brothers 1994, Melvin and Guy 2010). Torilines is popular by-catch mitigation measure of seabirds for Japanese longliners but in the area at south of 30S, more effort should be needed to decrease CPUE by employing double torilines or combination of toriline and night setting or weighted branch lines. White-chinned petrels and Black-browed albatrosses were caught in October to December in off Namibia (25S, 5E). In the Southern Hemisphere of ICCAT conventional area, except for off South American water where observer data did not cover, introducing additional mitigation measures in the area south of 30S should be effective for the recovery of population level of albatrosses and petrels which is decreasing but additionally above-mentioned combination measures should also be introduced at the area off Namibia in the period, austral summer. There are high CPUE areas both of albatrosses and petrels observed not only in the coastal zone but in the offshore zone too, and the ones in the offshore zone would be ecological hot-spot, where the food availability is 1741

5 high. In future, the reason of high CPUE at particular offshore area might revealed by integrating and comparing ocean environment, CPUE of tuna and CPUE of seabird. In our study, by-catch level at south eastern Atlantic, off South America, could not evaluate due to the lack of observer data. That area is major distribution area of albatrosses and petrels of which population levels are concerned, and also the colony of Black-browed albatrosses, Grey-headed albatrosses and White-chinned petrels exists near there, Thus by-catch monitoring should be initiated and effective mitigation measure should be introduced as necessary. 5. References ACAP 2010, Albatross and petrel distribution in the Atlantic Ocean and overlap with ICAAT longline fishing effort (SCRS/2010/050). ACAP 2011, ACAP species. Berrow, S.D., Wood, A.G. and Prince, P.A. 2000, Foraging location and range of White-chinned petrels Procellaria aequinoctialis breeding in the South Atlantic. Journal of Avian Biology 31: Brothers, N. 1994, Fisheries should catch fish, not birds. Pandani Publisher, Hobart. García-Barcelona, S., Ortiz de Urbina, J.M., de la Serna, J.M., Alot, E. and Macías, D. 2010, Seabird by-catch in Spanish Mediterranean large pelagic longline fisheries, Aquatic Living Resources, October 2010, 23: pp Kiyota, M. 2002, Incidental take of seabirds in lingline fisheries: Nature of the issue and measures for mitigation, J Yamashina Inst Ornithol 34: Melvin, E., Troy, G. and Sato, N. 2011, Preliminary Report of 2010 Weighted Branchline Trials in the Tuna Joint Venture Fishery in the South African EEZ (SCRS/2011/064). Onley, D. and Scofield, P. 2007, Albatrosses, Petrels, and Shearwaters of the World. Princeton University Press, New Jersey. Sato, N., Ochi, D., Minami, H., Shono, H. and Yokawa, K. 2010, Experimental comparison among four types Tori-line desinings in the Western North Pacific. WCPFC-SC /EB-WP-02. Nakano, H. 2002, The species identification guide for the pelagic longline fishery. Western North Pacific. National Reserch Institute of Far Seas Fisheries. Sizuoka. Weimerskirch, H., Y. Cherel, F.Cuenot-Chaillet and V. Ridoux 1997, Alternative foraging strategies and resource allocation by male and female wandering albatrosses. Ecology 78: Weimerskirch, H. and Cherel, Y. 1998, Feeding ecology of short-tailed shearwaters: breeding in Tasmania and foraging in the Antarctic? Mar. Ecol. Prog. Ser., 167: Weimerskirch H. 1998, How can a pelagic seabird provision its chicks when relying on a distant food resource? Cyclic attendance at the colony, foraging decision and body condition in sooty shearwaters. J Anim. Ecol., 67: Yokota K., Kiyota, M. 2008, Mitigation measures to reduce incidental catch of seabirds: Recent developments in Japanese tuna longline fishery. Nippon Suisan Gakkaishi 74:

6 Table 1. By-catch seabirds in ICCAT area during Number of hooks Wandering albatross Deomedea exulans 24 Royal albatross Diomedea epomophora 9 Black-browed albatross Diomedea melanophris 63 Buller's albatross Diomedea bulleri 1 White-capped albatross Diomedea cauta cauta 40 Yellow-nosed albatross Deomedea chlororhynchos 3 Grey-headed albatross Diomedea chrysostoma 90 Sooty albatross Phoebetria fusca 4 Light-mantled sooty albatross Phoebetria palpebrata 6 Unidentified albatross 69 Northern giant petrel Macronectes halli 20 Southern giant petrel Macronectes giganteus 14 Northern fulmar Fulmarus glacialis 2 Kerguelen petrel Pterodroma brevirostris 1 Grey petrel Procellaris cinerea 26 White-chinned petrel Procellaria aequinoctialis 47 Manx shearwater Puffinus puffinus 3 Unidentified petrels 27 Northern gannet Sula bassana 13 Cape gannet Sula capensis 2 South polar skua Catharacta maccormicki 1 Unidentified gulls 8 Other birds 29 Total albatrosses 309 Total giant petrels 34 Total petrels 106 Total seabirds

7 Figure 1. Effort (number of hooks) distribution in the ICCAT area of observer data used in this study by quarter of year during

8 Figure 2. CPUE (numbers per 1000 hooks) of all seabirds at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during

9 Figure 3. CPUE (numbers per 1000 hooks) of albatrosses at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during

10 Figure 4. CPUE (numbers per 1000 hooks) of petrels at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during

11 Figure 5. CPUE (numbers per 1000 hooks) of giant petrels at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during

12 Figure 6. CPUE (numbers per 1000 hooks) of wandering albatrosses at 5 5 grid square calculated by Japanese observers in the ICCAT area by quarter of year during

13 Figure 7. CPUE (numbers per 1000 hooks) of Black-browed albatrosses at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during

14 Figure 8. CPUE (numbers per 1000 hooks) of Grey-headed albatrosses at 5 5 grid square observed by Japanese observers in the ICCAT area by year quarter during

15 Figure 9. CPUE (numbers per 1000 hooks) of Grey petrels at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during

16 Figure 10. CPUE (numbers per 1000 hooks) of White-chinned petrels at 5 5 grid square observed by Japanese observers in the ICCAT area by quarter of year during