CHANGES IN FISHING PATTERN FROM SURFACE TO DEEP LONGLINE FISHING BY THE INDONESIAN VESSELS OPERATING IN THE INDIAN OCEAN
ABSTRACT: To understand the
historical catch and effort trends of Indonesian commercial tuna longline
fishery, the (P.T. Perikanan Samodra Besar) data are a valuable source, since
they are the longest time series of catch and effort data available from the
fishery. This paper aimed to interpret the spatial and temporal catch and
effort trends to the extent possible and to reconcile apparent changes in
targetingpractices against the actual catch. Catch and effort data collected by
P.T. Perikanan Samodra Besar from its Benoa-based longliners during 1978-1995
were summed to obtain annual catch, effort, and catch per unit of effort
trends. To generate spatial distributions of catch and effort, catch and effort
data were aggregated by 5-degree squares. The data showed that P.T. Perikanan
Samodra Besar vessels commenced deep longlining in 1983, i.e. 56% of the total
sets in 1983 using 10 or more hooks between floats. Prior to that, P.T.
Perikanan Samodra Besar vessels used 6 hooks between floats,which resulted in a
larger amount of yellowfin tuna (Thunnus albacares) as well as overall tuna
catch. However, bigeye tuna (Thunnus obsesus) catch per unit of effort only
increased from 1992. Theincrease in big eye tuna catch per unit of effort
coincided with a reduced fishing range and concentration within an area where
P.T. Perikanan Samodra Besar had not previously experienced high big eye tuna catches,
as opposed to focusing their effort on areas where they had historically caught
big eye tuna. In the absence of supplementary information, and assuming that
the switch to deep longlining in 1983 was done to target big eye tuna, the
analysis suggests that the outcome of P.T. Perikanan Samodra Besar fishing
activities between 1983 and 1991were inconsistent with their objectives.
KEYWORDS: longline tuna
fishery, deep longline, surface longline, Indian Ocean
Author: Lilis Sadiyah
Journal Code: pperikanangg110027
