scholarly journals Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives

2014 ◽  
Vol 71 (7) ◽  
pp. 1728-1749 ◽  
Author(s):  
David M. Kaplan ◽  
Emmanuel Chassot ◽  
Justin M. Amandé ◽  
Sibylle Dueri ◽  
Hervé Demarcq ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Fishery Management ◽  
Tropical Indian Ocean ◽  
Catch Per Unit Effort ◽  
Management Options ◽  
Fish Movements ◽  
Spatial Management ◽  
Spatio Temporal ◽  
Tuna Fisheries ◽  
Tropical Tuna

Abstract Effective use of spatial management in the pelagic realm presents special challenges due to high fish and fisher mobility, limited knowledge and significant governance challenges. The tropical Indian Ocean provides an ideal case study for testing our ability to apply existing data sources to assessing impacts of spatial management on tuna fisheries because of several recent controversial spatial closures. We review the scientific underpinnings of pelagic MPA effects, spatio-temporal patterns of Indian Ocean tuna catch, bycatch and fish movements, and the consequences of these for the efficacy of spatial management for Indian Ocean tropical tuna fisheries. The tropical Indian Ocean is characterized by strong environmental fluctuations, regular seasonal variability in catch, large observed tuna displacement distances, relatively uniform catch-per-unit-effort and bycatch rates over space, and high fisher mobility, all of which suggest significant variability and movement in tropical tuna fisheries that are simply not well adapted to static spatial closures. One possible exception to this overall conclusion would be a large time/area closure east of Somalia. If closed for a significant fraction of the year it could reduce purse-seine bycatch and juvenile tuna catch. Dynamic closures following fish migratory patterns are possible, but more focused information on fish movements will be needed for effective implementation. Fortunately, several recent improvements in conventional fishery management and reporting will likely enhance our ability to evaluate spatial and non-spatial management options in the near future, particularly as pertaining to bycatch species.

scholarly journals THE IMPACT OF ENVIRONMENTAL CHANGES ON BLACK MARLIN, Makaira indica (Cuvier, 1832) ABUNDANCES IN THE EASTERN INDIAN OCEAN

2020 ◽  
Vol 26 (1) ◽  
pp. 41
Author(s):  
Bram Setyadji ◽  
Zulkarnaen Fahmi
Keyword(s):  
Indian Ocean ◽  
Fishery Management ◽  
Environmental Changes ◽  
Stock Assessment ◽  
Sea Surface ◽  
Main Driver ◽  
Spatio Temporal ◽  
Standardized Index ◽  
By Catch ◽  
The Impact

Black marlin (Makaira indica) is commonly caught as frozen by-catch from Indonesian tuna longline fleets. Its contribution estimated 18% (~2,500 tons) from total catch in Indian Ocean. Relative abundance indices as calculated based on commercial catches are the input data for several to run stock assessment analyses that provide models to gather information useful information for decision making and fishery management, however, little are known about the influence of environmental factors to its abundance. In this paper, the abundance was represented as standardized index in order to eliminate any bias on other factors which might influence it. Data were collected from August 2005 to December 2017 through scientific observer program (2005-2017) and national observer program (2016-2017). Most of the vessels monitored were based in Benoa Port, Bali. Overall, time trends of abundance was fluctuated, although, there was increasing trend since 2010 then dropped significantly into relatively similar figure in 2005. Even though, Sea Surface Temperature (SST) and Sea Surface Height (SSH) were statistically significant when incorporating into the models, but it allegedly wasn’t the main driver in determining the abundance of black marlin. Instead, it was more likely driven by spatio-temporal factors (year and area) effect rather than environmental changes.

scholarly journals Standardization of a geo-referenced fishing dataset for the IndianOcean Bigeye Tuna, <i>Thunnus obesus</i> (1952–2014)

2016 ◽  
Author(s):  
Teja A. Wibawa ◽  
Patrick Lehodey ◽  
Inna Senina
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Fishing Effort ◽  
Purse Seine ◽  
Historical Period ◽  
Data Sets ◽  
Bigeye Tuna ◽  
Thunnus Obesus ◽  
Modelling Studies ◽  
Tuna Fisheries

Abstract. Geo-referenced catch and fishing ­effort data of the bigeye tuna fisheries in the Indian Ocean over 1952–2014 were analysed and standardized to facilitate population dynamics modelling studies. During this sixty-two years historical period of exploitation, many changes occurred both in the fishing techniques and the monitoring of activity. This study includes a series of processing steps used for standardization of spatial resolution, conversion and standardization of catch and effort units, raising of geo-referenced catch into nominal catch level, screening and correction of outliers, and detection of major catchability changes over long time series of fishing data, i.e., the Japanese longline fleet operating in the tropical Indian Ocean. A total of thirty fisheries were finally determined from longline, purse seine and other-gears data sets, from which 10 longline and four purse seine fisheries represented 96 % of the whole historical catch. The geo-referenced records of catch, fishing effort and associated length frequency samples of all fisheries are available at doi.pangaea.de/10.1594/PANGAEA.864154.

scholarly journals Characteristics of Thermal Front in the Tropical Waters of Eastern Indian Ocean

2019 ◽  
Vol 21 (1) ◽  
pp. 25
Author(s):  
Soni Rohima Daulay ◽  
Tengku Ersti Yulika Sari ◽  
Usman Usman ◽  
Romie Jhonnerie
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Thermal Front ◽  
Image Edge Detection ◽  
Moderate Resolution ◽  
Level 3 ◽  
Resolution Imaging ◽  
Image Edge ◽  
Spatio Temporal ◽  
Moderate Resolution Imaging Spectroradiometer

This study aims to elucidate spatio-temporal variability of the thermal front in the eastern tropical Indian Ocean of the western Sumatera. The research was conducted during November 2017- February 2018. The Single Image Edge Detection (SIED) was applied to daily sea surface temperature (SST) data of 2016 of the level-3 Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) for the detection of thermal front. The number of the thermal front events during 2016 were 167 days. The distribution and frequency of thermal front mostly found in January, i.e. 23 days with SST mean of 30.3ºC. Whereas the lowest distribution appeared in November and the lowest frequency observed in September, i.e. 6 days with the SST mean of 29.1ºC. The highest temperature range of thermal front is between 31.4-32.0ºC and the lowest ranged between 26.4-29.3ºC. The occurrences of thermal front were commonly found in the open ocean. The highest frequency occurred in January and the lowest took place in September with the longest duration of 3 days.

scholarly journals The key role of the Northern Mozambique Channel for Indian Ocean tropical tuna fisheries

2019 ◽  
Vol 29 (3) ◽  
pp. 613-638 ◽  
Author(s):  
Emmanuel Chassot ◽  
Nathalie Bodin ◽  
Fany Sardenne ◽  
David Obura
Keyword(s):  
Indian Ocean ◽  
Mozambique Channel ◽  
Tuna Fisheries ◽  
Tropical Tuna

scholarly journals Estimated production, catch per unit effort, biological aspects of tuna, skipjack, and small tuna in North Sumatra

2021 ◽  
Vol 322 ◽  
pp. 03003
Author(s):  
Gussasta Levi Arnenda ◽  
Fathur Rochman ◽  
Arief Wujdi ◽  
Roy Kurniawan
Keyword(s):  
Renewable Resources ◽  
Fishery Management ◽  
Yellowfin Tuna ◽  
Length Class ◽  
Management Policy ◽  
Skipjack Tuna ◽  
Catch Per Unit Effort ◽  
Biological Aspects ◽  
Tuna Fisheries ◽  
North Sumatra

Tuna and like species resources are like other renewable resources. The level of exploitation of these resources dramatically affects their ability to maintain their numbers and abundance in the water. Fishery management policy should be conducted based on a scientific-based approach. This research aims to collect data related to tuna fisheries and the like, including data collection aspects of coaching, the composition of catches, and the biology of tuna catches in 2020. Research location in North Sumatra. The results showed that the estimated value of skipjack tuna (SKJ) of 232,823 tons, yellowfin tuna (YFT) of 23,682 tons, frigate tuna (FRI) is 40,949 tons, and Kawakawa (KAW) is 1,374 tons. SKJ, as of 6.149 samples, have length class 18-60 cmFL, CPUE highest in April and lowest in August. FRI of 1.619 samples with a lengthy class between 17-44 cmFL, CPUE highest in October and lowest in December. YFT of 1.060 samples with a lengthy class 18-60 cm, CPUE highest in April and lowest in March. Kawakawa of the 1.530 samples has length class 25-54 cm, with the highest CPUE in April and lowest in March and July.

Vertical distribution of bigeye tuna Thunnus obesus in the tropical Indian Ocean

2013 ◽  
Vol 20 (3) ◽  
pp. 660-671 ◽  
Author(s):  
Xuezhong CHEN ◽  
Shenglong YANG ◽  
Yu Zhang ◽  
Wei FAN ◽  
Yumei WU
Keyword(s):  
Indian Ocean ◽  
Vertical Distribution ◽  
Tropical Indian Ocean ◽  
Bigeye Tuna ◽  
Thunnus Obesus

Interannual variability of the Tropical Indian Ocean mixed layer depth

2012 ◽  
Vol 40 (3-4) ◽  
pp. 743-759 ◽  
Author(s):  
M. G. Keerthi ◽  
M. Lengaigne ◽  
J. Vialard ◽  
C. de Boyer Montégut ◽  
P. M. Muraleedharan
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Ocean Mixed Layer Depth

scholarly journals Quantifying the increase in fishing efficiency due to the use of drifting FADs equipped with echosounders in tropical tuna purse seine fisheries

2020 ◽  
Author(s):  
Gwenaëlle Wain ◽  
Loreleï Guéry ◽  
David Michael Kaplan ◽  
Daniel Gaertner
Keyword(s):  
New Technology ◽  
Recent Change ◽  
Purse Seine ◽  
Catch Per Unit Effort ◽  
Katsuwonus Pelamis ◽  
Thunnus Obesus ◽  
Efficiency Increase ◽  
Tropical Tuna ◽  
Floating Objects ◽  
The Impact

Abstract Numerous pelagic species are known to associate with floating objects (FOBs), including tropical tunas. Purse seiners use this behaviour to facilitate the capture of tropical tunas by deploying artificial drifting fish aggregating devices (dFADs). One major recent change has been the integration of echosounders in satellite-tracked GPS buoys attached to FOBs, allowing fishers to remotely estimate fishable biomass. Understanding the effects of this new technology on catch of the three main tuna species (yellowfin tuna, Thunnus albacares; bigeye tuna, Thunnus obesus; and skipjack tuna, Katsuwonus pelamis) is important to accurately correct for this change in catch-per-unit-effort (CPUE) indices used for stock assessments. We analysed catch data from the French purse seine fleet for the period 2010–2017 in the Indian Ocean to assess the impact of this fleet’s switch to echosounder buoys around 2012. Results indicate that echosounders do not increase the probability a set will be succesful, but they have a positive effect on catch per set, with catches on average increasing by ≈2−2.5 tonnes per set (≈10%) when made on the vessel's own dFADs equipped with an echosounder buoy. Increases were due to a decrease in sets below ≈25 tonnes and an increase in those greater than ≈25 tonnes, with a non-linear transition around this threshold. This increase explains the considerable investment of purse seiners in echosounder buoys, but also raises concerns about bias in stock size estimates based on CPUE if we do not correct for this fishing efficiency increase.

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