THE EFFECT OF DEPTH OF HOOKS, SET AND SOAK TIME TO THE CATCH PER UNIT OF EFFORT OF TUNA IN THE EASTERN INDIAN OCEAN
Abstract: Yellowfin (Thunnus
albacares) and bigeye (T. obesus) tuna have been intensively exploited by
longline fleets since 1980’s, however, a large proportion of zero catch per set
of target species still accurred. Zero catch data contributed significantly to
the low catch per unit of effort (CPUE) compared to other countries at the same
fishing area. Therefore, understanding the factors contributed to the CPUE of
tuna is essential, in order to improve longline fishing efficiency. A total of
2.115 set-by-set data were obtained from Indonesian Scientific Observer
Program. The onboard observations were carried out at commercial tuna longline
operated in Eastern Indian Ocean from August 2005 to December 2014. Several
analytical approaches were conducted in this paper. First, General Linear Model
(GLM) was applied in order to model the relationship between CPUE with all the
variables involved. Second, boxplot diagram, polynomial and linear regression
were applied to fit the relationship between CPUE with set time, soak time and
depth (represented by hook position) respectively. The result showed that,
there was no significant relationship between set time and CPUE of bigeye and
yellowfin tuna. Soak time was positively related with CPUE of yellowfin and
affect adversely on bigeye. Depth also have significant relationship with CPUE
of tuna, where catch of yellowfin decreased linearly with hook depth, whereas
catch of bigeye was performed the opposite. Improvement in tuna longline
fishery in eastern Indian Ocean can be achieved through implementation of the
specific soak time and hook depth for each target species, i.e. yellowfin and
bigeye tuna.
Keywords: Yellowfin tuna;
bigeye tuna; set time; soak time; hook depth; Indian Ocean
Author: Bram Setyadji, Budi
Nugraha, Lilis Sadiyah
Journal Code: jpperikanangg160050
