The sustainable utilization of skipjack tuna in Northern Aceh waters

In recent years, production of skipjack tuna in Aceh was fluctuative in decreased trend due to relatively smaller fish size production. This study was aimed to analyse the skipjack tuna utilization sustainability on actual, maximum sustainable yield (MSY), maximum economic yield (MEY), and open-access (OA) conditions in North Aceh Waters. This study used time series data in 2009-2018. The analysis method used was a Gordon-Schaefer bioeconomical model. The results that the utilization of skipjack tuna in North Aceh Waters were at economical and biological overfishing. In long-term condition, this will potentially cause a decreased fish stock that will finally disrupt the sustainability level. In actual condition, the average of skipjack tuna utilization level per year was 163.77% more than the allowed total catching product, namely 2,712.64 ton per year. To achieve sustainable point, the fishermen should decrease their effort at 19.32% of the actual condition effort. The highest biomass level was occurred in MEY regime, followed by MSY and OA regimes. This means that the management of skipjack tuna in MEY regime is more conservative than in other regimes due to not spending skipjack tuna resource maximumly, but proposing to an optimum production level, which results in a maximum profit.

Conventional and Non-conventional Smoking on Microbial Quality and Histamine of Ikan Fufu (Smoked Fish)

Fish is a commodity with high nutritional value. The content of this nutritional value causes fish to be easy to decompose. Therefore, it is necessary to develop and process skipjack fufu (smoked skipjack) fish that improve the quality of smoked skipjack tuna (smoked skipjack) chemically, microbiologically, and with low histamine content. The purpose of this study was to determine the chemical, microbiological, and histamine quality of smoked fish with conventional and non-conventional smoking. This type of research was a quantitative study with a randomized block design. This research is a laboratory experiment with two treatments, namely conventional and non-conventional methods equipped with three replications and three blocks. The results of the test on the third day (H3) and the ninth day (H9) of storage showed that there was no growth of Salmonella sp. and Vibrio cholera in smoked fish samples with conventional (P2) and non-conventional (P1) smoking techniques. There were differences in non-conventional and conventional smoking on the histamine content in smoked fish. Conclusion. There was no growth of Salmonella sp and Vibrio cholera in smoked fish. There is a difference in the histamine content of conventional (P2) and non-conventional (P1) smoking techniques in smoked fish.

Struktur, Perilaku dan Kinerja Pemasaran Ikan Cakalang di Kabupaten Halmahera Selatan

Skipjack tuna is the result of the main capture fisheries in the South Halmahera district which experienced significant growth of 4,2 percent during the 2016-2018 period, but increased production experienced constraints in the marketing system and caused income uncertainty for fishermen and traders. The purpose of this study was to determine the marketing system of skipjack tuna in the South Halmahera Regency using a structural, behavioural, and performance (SCP) approach. The sampling method uses snowball sampling which started with 68 fishermen. The results showed that the market structure formed was an oligopsonistic market structure and there was a barrier to market entry of 14 percent. Meanwhile, market behaviour shows that fishermen only act as price takers. Based on the marketing margin analysis, there are 10 (ten) skipjack fish marketing channels. Judging from the value of large skipjack fish, marketing channel 7 has the highest margin value of 70,4 percent and the lowest is channel 8 of 53,9 percent. Meanwhile, the marketing channel of small fish the highest margin value is marketing channel 9 of 73,9 and the lowest is channel 9 of 65,1 percent. While the value of farmer share, channel 1 has the highest value of 70 percent and the lowest is channel 7 of 36 percent. Overall, skipjack tuna marketing channels have not been efficient.

Identification of yellowfin tuna (Thunnus albacares), mackerel tuna (Euthynnus affinis), and skipjack tuna (Katsuwonus pelamis) using deep learning

Yellowfin tuna (Thunnus albacares), mackerel tuna (Euthynnus affinis), and skipjack tuna (Katsuwonus pelamis) have important economic values for the capture fisheries in Indonesia. Activities of identifying these fish and other types of tuna have been done manually, which can lead to errors and ultimately affect statistics, stock estimates, or traceability. The aim of this research is to use deep learning methods in identifying three species of tuna, specifically yellowfin tuna, mackerel tuna, and skipjack tuna. YOLO’s newest model, YOLOv5, was used to identify the fish. The number of epochs that produces the optimum accuracy value for use in the YOLOv5 model is 400. The values for training loss, accuracy, precision, recall and F1-Score when the model is learning with a total of 400 epochs are 0.000253, 95%, 98.1%, 93.9%, and 96%. Based on these results, the three species of tuna can be identified with high accuracy.

A Bayesian Multilevel Ordinal Regression Model for Fish Maturity Data: Difference in Maturity Ogives of Skipjack Tuna (Katsuwonus pelamis) Between Schools in the Western and Central Pacific Ocean

The maturity ogive is vital to defining the fraction of a population capable of reproduction. In this study, we proposed a novel approach, a Bayesian multilevel ordinal regression (i.e., Bayesian continuation ratio model), to model the maturity ogive. The model assumes that the observed maturity stage originates from the categorization of latent continuous variables. We demonstrated this approach by testing whether there are differences in the maturity ogive of skipjack tuna (Katsuonus pelamis) in the western and central Pacific Ocean between two school types, i.e., free-swimming and floating-object-associated schools. The model results show that K. pelamis, given the same fork length, are more likely to have a higher maturity stage in a free-swimming school than those associated with floating objects. The gonadosomatic index revealed the same conclusion. Our results indicate that fish aggregation devices (FADs) could negatively affect the maturity of K. pelamis and consequently reduce the population reproductive potential. This study provides (1) an alternative approach to analyze fisheries ordinal data; (2) important quantitative evidence to evaluate the existing ecological hypotheses; and (3) implications for tuna fisheries management.

DINAMIKA MUSIM PENANGKAPAN IKAN CAKALANG DAN TONGKOL DI PERAIRAN PALABUHANRATU

The monthly fluctuation of fish catch is closely related to the presence of fish or the fishing season. Information about the fishing season is important to improve the efficiency and effectiveness of fishing carried out by fishermen. Skipjack and tuna are important catches landed by fishermen in Palabuhanratu fishing port, with fishing grounds in the waters around Palabuhanratu Bay. This study aims to describe the dynamics of the catch and the effort to catch skipjack and tuna that land their fish in the Palabuhanratu fishing port and determine the fishing season. The data used is the Palabuhanratu fishing port fisheries statistical data for the 2015-2019 period. Data analysis used catch per unit effort (CPUE) analysis and moving average model. The results showed that the CPUE value of skipjack tuna fluctuates tends to increase by 0,009 tons per trip and reaches the highest in 2017 which is around 3,068 tons per trip. The CPUE value of tuna tends to increase from 0,021 tons per trip in 2015 to 0,266 tons per trip in 2019. The skipjack tuna fishing season occurs in March, July to November, while the tuna fishing season occurs from July to November. Keywords: skipjack tuna, fishing season index, moving average model, tongkol, Palabuhanratu