scholarly journals Target strength of skipjack tuna (Katsuwanus pelamis) associated with fish aggregating devices (FADs)

2018 ◽  
Vol 75 (5) ◽  
pp. 1790-1802 ◽  
Author(s):  
Guillermo Boyra ◽  
Gala Moreno ◽  
Bea Sobradillo ◽  
Isabel Pérez-Arjona ◽  
Igor Sancristobal ◽  
...  
Keyword(s):  
Fork Length ◽  
Acoustic Properties ◽  
Target Strength ◽  
Skipjack Tuna ◽  
Method Of Least Squares ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Fish Morphology ◽  
Ocean Measurements ◽  
Fish Aggregating Devices

Abstract This paper presents measures of target strength (TS; dB re 1 m2) and models of TS vs. fork length (L; cm), i.e. TS=20logL+b20, for skipjack tuna associated with fish aggregating devices (FADs) in the Central Pacific Ocean. Measurements were made using 38-, 120-, and 200-kHz split-beam echosounders on a purse-seine workboat during fishing operations. To mitigate potential bias due to unresolved targets, TS measurements were rejected if they were not simultaneously detected with multiple echosounder frequencies in approximately the same location. The filtered TS and concomitantly sampled L data were used to estimate b20 = −76, −71, and −70.5 dB for 38, 120, and 200 kHz, respectively, using the method of least squares. For comparison, quasi-independent estimates of TS and b20 were calculated from acoustic echo-integration and catch data representing entire aggregations around the FADs. The results differed by ≤1 dB for all three frequencies. The sensitivities of these results to variations in fish morphology and behaviour were explored using a simulation of TS for fish without swimbladders. The utility of the results on acoustic properties of skipjack tuna and next research steps to achieve selective fishing at FADs are discussed.

scholarly journals Combining Weight-Length Relationships and condition factors to estimate the population structure for Skipjack tuna in the Western and Central Pacific Ocean

2014 ◽  
Author(s):  
Shaofei Jin ◽  
Xiaodong Yan ◽  
Heng Zhang ◽  
Wei Fan
Keyword(s):  
Population Structure ◽  
Pacific Ocean ◽  
Fork Length ◽  
Skipjack Tuna ◽  
Growth Phases ◽  
Central Pacific ◽  
Katsuwonus Pelamis ◽  
Central Pacific Ocean ◽  
Length Relationship ◽  
June July

The arguments between Weight-Length Relationship (WLR) and Condition Factor (K) have been lasted since the day they occurred. This paper described WLRs and Ks of Skipjack tuna (Katsuwonus pelamis) samples in Purse Seine fisheries from three cruises (August-September cruise (A-S) in 2009, November-December cruise (N-D) in 2012, and June-July cruise (J-J) in 2013) in the Central and Western Pacific Ocean (CWPO). The results showed that fork length of more than 70% of specimen was below 60 cm (76% in A-S, 87% in N-D, and 73% in J-J). b values of WLRs in class of fork length > 60cm were below 3 significantly (P = 0.062), while b values when fork length < 60 cm were > 3 significantly (P = 0.028). Moreover, K values in different fork length classes for each cruises had one turning point: 60-65cm for J-J, 60-65cm for N-D, and 55-60cm for A-S, and K values were still significantly larger than those of fork length < 40cm (P = 0.06). However, b values at larger fishes were significantly smaller than those of fork length <40cm. We suggest to combine WLRs and K values at different growth phases for evaluating population structure for skipjack tuna.

scholarly journals 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

2021 ◽  
Vol 8 ◽  
Author(s):  
Jie Cao ◽  
Xuefang Wang ◽  
Matthew D. Damiano ◽  
Cheng Zhou ◽  
Jiangfeng Zhu
Keyword(s):  
Pacific Ocean ◽  
Ordinal Data ◽  
Gonadosomatic Index ◽  
Fork Length ◽  
Ordinal Regression ◽  
Maturity Stage ◽  
Skipjack Tuna ◽  
Central Pacific ◽  
Free Swimming ◽  
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.

scholarly journals Combining Weight-Length Relationships and condition factors to estimate the population structure for Skipjack tuna in the Western and Central Pacific Ocean

2014 ◽  
Author(s):  
Shaofei Jin ◽  
Xiaodong Yan ◽  
Heng Zhang ◽  
Wei Fan
Keyword(s):  
Population Structure ◽  
Pacific Ocean ◽  
Fork Length ◽  
Skipjack Tuna ◽  
Growth Phases ◽  
Central Pacific ◽  
Katsuwonus Pelamis ◽  
Central Pacific Ocean ◽  
Length Relationship ◽  
June July

The arguments between Weight-Length Relationship (WLR) and Condition Factor (K) have been lasted since the day they occurred. This paper described WLRs and Ks of Skipjack tuna (Katsuwonus pelamis) samples in Purse Seine fisheries from three cruises (August-September cruise (A-S) in 2009, November-December cruise (N-D) in 2012, and June-July cruise (J-J) in 2013) in the Central and Western Pacific Ocean (CWPO). The results showed that fork length of more than 70% of specimen was below 60 cm (76% in A-S, 87% in N-D, and 73% in J-J). b values of WLRs in class of fork length > 60cm were below 3 significantly (P = 0.062), while b values when fork length < 60 cm were > 3 significantly (P = 0.028). Moreover, K values in different fork length classes for each cruises had one turning point: 60-65cm for J-J, 60-65cm for N-D, and 55-60cm for A-S, and K values were still significantly larger than those of fork length < 40cm (P = 0.06). However, b values at larger fishes were significantly smaller than those of fork length <40cm. We suggest to combine WLRs and K values at different growth phases for evaluating population structure for skipjack tuna.

scholarly journals In situ target strength of bigeye tuna (Thunnus obesus) associated with fish aggregating devices

2019 ◽  
Author(s):  
G Boyra ◽  
G Moreno ◽  
B Orue ◽  
B Sobradillo ◽  
I Sancristobal
Keyword(s):  
Frequency Response ◽  
Target Strength ◽  
Species Discrimination ◽  
Bigeye Tuna ◽  
Central Pacific ◽  
Commercial Fish ◽  
Thunnus Obesus ◽  
Tropical Tuna ◽  
Fish Aggregating Devices

Abstract Bigeye tuna (Thunnus obesus) is an important commercial fish species, which aggregates around fish aggregating devices (FADs) together with other tropical tuna species. Acoustics is the main technology used by fishers and scientists for the location and quantification of tunas at FADs. However, currently it is not possible to reliably discriminate between the different tropical tuna species that are found together at FADs using acoustic methods, which hampers the development of selective fishing needed to preserve some of the tropical tuna species for which overfishing is occurring. One of the prerequisites for species discrimination is to know the target strength (TS) of each species at different frequencies. This paper measures in situ TS values and explores the frequency response of bigeye tuna at FADs in the central Pacific Ocean using three different acoustic frequencies. For the range of body length caught (40–100 cm), the obtained b20 values were −65, −66, and −72 dB for 38, 120, and 200 kHz, respectively. The decreasing frequency response pattern obtained for this swimbladder bearing species contrasts with the opposite pattern previously observed for skipjack tuna (bladder-less), the most abundant tuna species found at FADs, hence allowing the potential for discrimination between the two species.

scholarly journals STATUS KEBERLANJUTAN PERIKANAN HUHATE BERDASARKAN ASPEK BIOLOGI DI PPI DUFA-DUFA KOTA TERNATE

1970 ◽  
Vol 10 (1) ◽  
pp. 117-116
Author(s):  
Irham . ◽  
Amirul Karman ◽  
Kusdi Hi Iksan
Keyword(s):  
Size Structure ◽  
Economic Value ◽  
Fork Length ◽  
Pelagic Fish ◽  
Fishing Ground ◽  
Skipjack Tuna ◽  
Katsuwonus Pelamis ◽  
Strategic Location ◽  
Catch Composition ◽  
Fish Aggregating Devices

ABSTRACTTernate Island lies in a strategic location as it is situated in the middle of  the main fishing ground for skipjack (Katsuwonus pelamis) fishing using pole and line (huhate) and fish aggregating devices (FADs). As typical pelagic fish, skipjack that is gathered near the water surface is the younger fish, likewise the ones which are caught around FADs. Therefore, this fishing method has caused serious problem due to the domination of young fish and increasing bycatch and discard. The objective of this research is to analyze the size structure of the fork length, appropriate size for catching, catch composition, bycatch and discard level. Pole and line catch samples were collected in 3 months fromMay to July 2018. The results show that in average, skipjack tuna caught in the study location was undersize. The total catch is predominantly targeted fish which has a higher economic value compared to bycatch and discarded fish. Even though bycatch in the pole and line fisheries are low, reduction efforts are still required. which can be done by sorting bycatch and unwanted fish then discard it into the sea when the fish is still alive.Keywords: biology, pole and line, sustainability status, Ternate City ABSTRAKPosisi Pulau Ternate sangat strategis karena berada di tengah perairan yang menjadi daerah operasi penangkapan cakalang (Katsuwonus pelamis) dengan alat tangkap huhate (pole and line) yang dibantu dengan penggunaan rumpon. Sebagaimana ikan pelagis lainnya,  ikan-ikan cakalang yang berkumpul di lapisan permukaan air cenderung tergolong ikan-ikan muda. Oleh karena itu, cakalang yang tertangkap di sekitar rumpon juga cenderung ikan-ikan yang masih muda. Fenomena ini menyebabkan munculnya sebuah masalah besar, yaitu dominasi ikan-ikan muda, selain itu juga sering tertangkap ikan yang bukan target tangkap yang terdiri dari bycatch dan discards. Tujuan dari penelitian ini adalah menganalisis struktur ukuran panjang cagak dan ukuran cakalang layak tangkap, komposisi hasil tangkapan, persentase bycatch dan discards. Sampel hasil tangkapan huhate dikumpulkan selama 3 bulan (Mei sampai Juli 2018). Hasil penelitian menunjukkan bahwa rataan cakalang di lokasi penelitian didominasi ukuran belum layak tangkap. Total hasil tangkapan didominasi ikan target, sementara itu bycatch yang tertangkap memiliki nilai ekonomis yang baik dan tidak ditemukan discards. Walaupun bycatch pada perikanan huhate rendah namun usaha-usaha untuk meminimumkan tetap perlu dilakukan. Salah satu usaha yang bisa dilakukan adalah menyortir hasil tangkapan, ada apabila ada ikan yang akan dibuang ke laut, dilakukan dalam keadaan masih hidup.Kata Kunci: Biologi, huhate (pole and line), status keberlanjutan, Kota Ternate

Reproductive biology of male skipjack tuna Katsuwonus pelamis (Linnaeus) in the tropical western and central Pacific Ocean

2010 ◽  
Vol 76 (5) ◽  
pp. 785-793 ◽  
Author(s):  
Hiroshi Ashida ◽  
Toshiyuki Tanabe ◽  
Keisuke Satoh ◽  
Atsushi Fukui ◽  
Sho Tanaka ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Reproductive Biology ◽  
Skipjack Tuna ◽  
Central Pacific ◽  
Katsuwonus Pelamis ◽  
Central Pacific Ocean
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