Dowling, Natalie
Pusat Penelitian dan Pengembangan Perikanan, Badan Penelitian dan Pengembangan Kelautan da

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CHANGES IN FISHING PATTERN FROM SURFACE TO DEEP LONGLINE FISHING BY THE INDONESIAN VESSELS OPERATING IN THE INDIAN OCEAN Sadiyah, Lilis; Dowling, Natalie; Prisantoso, Budi Iskandar
Indonesian Fisheries Research Journal Vol 17, No 2 (2011): (December, 2011)
Publisher : Pusat Penelitian dan Pengembangan Perikanan, Badan Penelitian dan Pengembangan Kelautan da

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (276.494 KB) | DOI: 10.15578/ifrj.17.2.2011.87-99

Abstract

(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 targeting practices 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. The increase 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 1991 were inconsistent with their objectives.
CPUE TRENDS OF THE INDONESIA’S TUNA LONGLINE FISHERY: LESSONS LEARNED FROM A TRIAL OBSERVER PROGRAM Sadiyah, Lilis; Dowling, Natalie; Prisantoso, Budi Iskandar; Andamari, Retno; Proctor, Craig
Indonesian Fisheries Research Journal Vol 20, No 1 (2014): (June 2014)
Publisher : Pusat Penelitian dan Pengembangan Perikanan, Badan Penelitian dan Pengembangan Kelautan da

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (394.382 KB) | DOI: 10.15578/ifrj.20.1.2014.37-47

Abstract

In an effort to address a shortage of reliable CPUE information, and as a preliminary step to a broader observer program, Indonesia established a Trial Observer Program (TOP) for the industrial tuna long line fishery based at Benoa Fishing Port, Bali, in mid 2005. The objectives of this paper are i) to describe spatial and temporal catch and effort trends from the Indonesian Indian Ocean industrial tuna long line fishery based at Benoa Fishing Port, and ii) to provide an understanding of the fishing strategies used by different companies and of the environmental conditions that may influence catch trends. The observed effort covered areas both north and south of 20°S, with a concentration within 10°-20°S; 105°-120°E which overlaps with the only known spawning grounds of southern bluefin tuna (SBT). This data set showed that SBT comprised the lowest catch proportion, relative to the other three tuna species caught, bigeye tuna (BET), yellowfin tuna (YFT) and albacore (ALB). BET and ALB had been suggested as the main target species for the fishery, but this varied by region. The TOP data set suggests that different tuna fishing companies targeted different species and used different fishing practices, including differences in bait used, areas fished, start time of setting, and the number of hooks between floats (HBF). It is a priority to improve the spatial and temporal coverage of the observer program before the data can be considered to be representative of the fleet, particularly given the high degree of variability in fishing practices between companies.
DEVELOPING RECOMMENDATIONS FOR UNDERTAKING CPUE STANDARDISATION USING OBSERVER PROGRAM DATA Sadiyah, Lilis; Dowling, Natalie; Prisantoso, Budi Iskandar
Indonesian Fisheries Research Journal Vol 18, No 1 (2012): (June 2012)
Publisher : Pusat Penelitian dan Pengembangan Perikanan, Badan Penelitian dan Pengembangan Kelautan da

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (664 KB) | DOI: 10.15578/ifrj.18.1.2012.19-33

Abstract

Abundance indices based on nominal CPUE do not take into account confounding factors such as fishing strategy and environmental conditions, that can decouple any underlying abundance signal in the catch rate. As such, the assumption that CPUE is proportional to abundance is frequently violated. CPUE standardisation is one of the common analyses applied. The aims of this paper were to provide a statistical modelling framework for conducting CPUE standardisations using the Observer Program data for bigeye tuna, yellowfin tuna, albacore and southern bluefin tuna, and provide a comparison in the trends between the nominal CPUEs and their standardised indices obtained. The CPUE standardisations were conducted on the Observer Program collected between 2005 and 2007, by applying GLM analysis using the Tweedie distribution. The results suggested that year, area, HBF and bait factors significantly influenced the nominal CPUEs for the four tuna species of interest. Some extreme peaks and troughs in the nominal time series were smoothed in the standardised CPUE timeseries. The high degree of temporal variability that is still shown in the standardised CPUE trends suggests that the data are too sparse to give any meaningful indication of proxy abundance. Nevertheless, this may also suggest that variables used in the GLMs do not sufficiently account for allof the confounding factors, or abundance may indeed be truly variable.
UTILITY OF FISHERY HIGH SCHOOL DATA IN EXAMINING SPATIAL AND TEMPORAL CATCH AND EFFORT TRENDS IN THE INDONESIAN LONGLINE TUNA FISHERY Sadiyah, Lilis; Dowling, Natalie; Prisantoso, Budi Iskandar; Andamari, Retno; Proctor, Craig
Indonesian Fisheries Research Journal Vol 21, No 2 (2015): (December 2015)
Publisher : Pusat Penelitian dan Pengembangan Perikanan, Badan Penelitian dan Pengembangan Kelautan da

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (525.002 KB) | DOI: 10.15578/ifrj.21.2.2015.117-128

Abstract

One of the endeavours to address the shortage of catch per unit effort (CPUE) information from the Indonesian Indian Ocean tuna fishery is the collation of a large amount of catch and effort data collected by Indonesian Fisheries High School students (“FHS data”). This paper attempts to investigate spatial-temporal patterns of catch and effort of the FHS data for the main tuna species caught by the fishery: bigeye tuna (Thunnus obesus - BET), yellowfin tuna (T. albacares - YFT), albacore (T. alalunga - ALB) and southern bluefin tuna (T.maccoyii - SBT). Reported sets occurred in the Eastern Indian Ocean, north and south of 20°S. Recorded effort from the FHS data set was concentrated within the only known SBT spawning ground. However, within this data set, SBT were recorded in the lowest catch proportion relative to BET, YFT and ALB. The catch composition data suggested that YFT and ALB were predominantly targeted by the fishery, with ALB and SBT most predominantly recorded south of 20°S, whereas BET and YFT were mostly recorded north of 20°S. Unfortunately, there was no strong information on targeting practices reported by this data set, limiting any attempts to understand the factors that influenced those results. As the sampling predominantly occurred in between July and December, the data are not representative of fishing activities throughout the entire year, and any seasonal patterns from the FHS data set are biased. In addition, the FHS data set is prone to observation error and uncertainty in terms of fish identification and fishing location. Therefore, the FHS data set needs to be interpreted with caution.