175 
Effects of El Nino-Southern Oscillation events 
on catches of Bigeye Tuna ( Thunnus obesus ) in 
the eastern Indian Ocean off Java 
Email address for contact author: vegha16@gmail.com 
1 Laboratory of Marine Bioresource and Environment Sensing 
Faculty of Fisheries Sciences 
Hokkaido University 
Minato-cho 3-1-1, Hakodate 
Hokkaido 041-8611, Japan 
3 Study Program of Geodetic and Geomatics Engineering 
Faculty of Earth Sciences and Technology 
Bandung Institute of Technology 
Jalan Ganesha 10 
Bandung 40132, Indonesia 
Abstract— The effects of El Nino- 
Southern Oscillation events on 
catches of Bigeye Tuna (Thun- 
nus obesus) in the eastern Indian 
Ocean (EIO) off Java were evaluated 
through the use of remotely sensed 
environmental data (sea-surface- 
height anomaly [SSHAj, sea-surface 
temperature [SST], and chlorophyll- 
a concentration), and Bigeye Tuna 
catch data. Analyses were conducted 
for the period of 1997-2000, which 
included the 1997-98 El Nino and 
1999-2000 La Nina events. The em- 
pirical orthogonal function (EOF) 
was applied to examine oceano- 
graphic parameters quantitatively. 
The relationship of those parameters 
to variations in catch distribution of 
Bigeye Tuna was explored with a 
generalized additive model (GAM). 
The mean hook rate was 0.67 dur- 
ing El Nino and 0.44 during La 
Nina, and catches were high where 
SSHA ranged from -21 to 5 cm, SST 
ranged from 24°C to 27.5°C, and 
chlorophyll-a concentrations ranged 
from 0.04 to 0.16 mg rcr 3 . The EOF 
analysis confirmed that the 1997- 
98 El Nino affected oceanographic 
conditions in the EIO off Java. The 
GAM results indicated that SST was 
better than the other environmen- 
tal factors (SSHA and chlorophyll-a 
concentration) as an oceanographic 
predictor of Bigeye Tuna catches in 
the region. According to the GAM 
predictions, the highest probabilities 
(70-80%) for Bigeye Tuna catch in 
1997-2000 occurred during oceano- 
graphic conditions during the 1997- 
98 El Nino event. 
Manuscript submitted 4 June 2012. 
Manuscript accepted 1 March 2013. 
Fish. Bull 111:175-188 (2013) 
doi 10.7755/FB. 11 1.2.5 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessar- 
ily reflect the position of the National 
Marine Fisheries Service, NOAA. 
Mega L. Syamsuddin (contact author)' 2 
Sei-lchi Saitoh 1 
Toru Hirawake' 
Samsul Bachri 3 
Agung B. Hart © 3 
2 Faculty of Fisheries and Marine Sciences 
Pad|ad|aran University 
Jalan Raya Bandung-Sumedang KM 21 
Jatinangor, Bandung 40600, Indonesia 
The El Nino-Southern Oscillation 
(ENSO) is a large-scale pattern of 
climate fluctuation that strongly in- 
fluences much of the globe. In the 
Pacific, the ENSO cycle causes warm 
phases (El Nino) and cool phases (La 
Nina) that have been shown to affect 
catches in tuna fisheries (Lehodey et 
al., 1997; Lehodey, 2001). The ap- 
proximate onset of the 1997-98 El 
Nino event occurred during March- 
April 1997, and the mature phase in 
November-December 1997 (Enfield, 
2001). The El Nino event ended in 
May 1998 and a cold La Nina was es- 
tablished in the eastern Pacific. The 
1997-98 El Nino was the strongest 
on record and affected the climate in 
many parts of the world (McPhaden, 
1999). Catches of tunas around the 
world are affected by ENSO events 
(Howell and Kobayashi, 2006; Le- 
hodey et al., 2010). Therefore, for 
sustainable management of Bigeye 
Tuna ( Thunnus obesus ) resources in 
the eastern Indian Ocean (EIO) off 
Java, one of the main islands in In- 
donesia, understanding the effects 
of ocean climate variability on catch 
distribution is essential. 
The Bigeye Tuna is a productive 
tropical species that accounts for more 
than 10% of the total catch of market 
tuna species worldwide (Miyake et 
al., 2010). Bigeye Tuna is a commer- 
cially targeted species and represents 
one of the most valuable species of 
longlme fisheries in the EIO off Java 
(ISSF 1 ). It is a highly migratory spe- 
cies that is distributed between 40°N 
and 40°S in all 3 major oceans, except 
in the southwestern sector of the At- 
lantic (Hanamoto, 1987). Bigeye Tuna 
generally favor water temperatures 
between 17°C and 22°C. They prefer 
to stay near, and usually below, the 
1 ISSF (International Seafood Sustain- 
ability Foundation). 2012. ISSF stock 
status ratings — 2012: status of the 
world fisheries for tuna. ISSF Tech. 
Rep. 2012-04, 88 p. [Available from 
http://iss-foundation.org/resources/ 
downloads/?did=328, accessed November 
2012.] 
