Bycatch Estimates From a Pacific Tuna Longline Fishery Provide a Baseline for Understanding the Long-Term Benefits of a Large, Blue Water Marine Sanctuary

Bycatch on pelagic tuna longlines has contributed to population declines in several far-ranging, oceanic species and presents a conservation challenge that area-based management tools are increasingly promoted to address. In January 2020 the Republic of Palau, concerned about the impacts of longline fishing in its waters, closed 80% of its exclusive economic zone to all extractive activities, reserving the remaining 20% for a domestic fishing zone (DFZ). One of a growing number of very large marine protected areas, the Palau National Marine Sanctuary (PNMS) spans ∼500,000 km2 and was established inter alia to allow for the recovery of fish stocks adversely impacted by tuna longline fleets. Given that the main tuna stocks targeted in the western Pacific are not overexploited, the benefits of protection potentially afforded by the sanctuary are likely greater for vulnerable bycatch species. Evaluations of the sanctuary’s performance require, in part, a baseline of historical catch rates and effort distribution in the distant-water fleet (DWF) and locally based fleet (LBF) operating in Palau prior to sanctuary implementation. We describe the fishing effort, catch rates, catch estimates and fishing mortality in Palau’s longline fishery based on logbook, observer and electronic monitoring data. We defined bycatch as any species, retained or discarded, other than targeted tunas. Between 2010 and 2020, 104.8 million hooks were deployed, catching over 2 million individuals from 117 taxa at an overall target:bycatch ratio of 1:1, with a retention rate of ∼62%. Pronounced differences in fishing strategies and spatial distribution of effort between fleets were associated with large variations in catch rates and composition. The LBF had a larger effect on populations of at-risk species relative to the DWF, with higher catch rates and magnitudes for several vulnerable species and higher observable fishing mortality rates (64% vs 50% in the DWF). The sanctuary reshaped Palau’s longline fishery, contracting the fishery’s area and capacity. The relocation of the DFZ eliminated the LBF and constrained the DWF to an area where the fleet’s total catch rates and those of a number of vulnerable species were historically lower relative to former fishing grounds now closed by the sanctuary. Our results highlight the importance of consistent bycatch monitoring and emphasize the need for regional area-based approaches for managing longline fisheries.

Fishing ground and tuna productivity by tuna longline based on Benoa Bay, Bali, Indonesia

Imron M, Tawaqal MI, Yusfiandayani R. 2021. Fishing ground and tuna productivity by tuna longline based on Benoa Bay, Bali, Indonesia. Biodiversitas 22: 961-968. The success of a longline fishing operation depends on several things such as the skill of the crew, bait used, fishing season, fishing operation, the total of fish caught, the price of the fish, productivity, and fishing grounds. Information about productivity and fishing ground becomes important to increase effectiveness and optimal profit. The methodology is carried out by conducting a survey to collect data to be processed and analyzed using productivity analysis based on Landing per Unit Effort (LPUE) and fishing activity analysis from the Vessel Monitoring System (VMS) to determine the Fishing Ground. We calculate tuna productivity from catch production (landing) per effort, meanwhile fishing ground use VMS data. Production tuna was landed at Benoa Bali from 2016-2018 fluctuated. In 2016 production of tuna albacore took a portion of 34.60%, yellowfin tuna 43.56%, bigeye tuna 15.44%, and southern bluefin tuna 6.26%. Production of tuna albacore took a portion of 35.61%, yellowfin tuna 42.64%, bigeye tuna 12.49%, and southern bluefin tuna 9.26% in 2017. Production albacore took a portion of 36.41%, yellowfin tuna 41.56%, bigeye tuna 11.79%, and southern bluefin tuna 10.24% in 2018. The highest productivity of albacore was in August 2018 with LPUE value 1.0099, yellowfin tuna was in July 2018 with LPUE value 1.2431, big eye tuna was in November 2018 with LPUE value 0.5538, and bluefin was at December 2017 with LPUE value 0.3864. The result of VMS data processing showed that tuna longline vessel based at Benoa has several locations of fishing grounds based on fishing activity for example Hindia High Seas, WPP NRI 714 (Telo gulf and Banda Sea), WPP NRI 718 (Aru Sea, Arafura Sea, and Timor Sea), ZEEI WPP NRI 718.

Stock depletion of yellowfin tuna Thunnus albacares (Bonnaterre 1788) in the Northeastern Indian Ocean

The stock of yellowfin tuna (Thunnus albacares) has been in a declining trend in the last five years. Although the noticeable decline mainly occurred in the western part of the Indian Ocean, uncertainty lingers on how this phenomenon will affect the opposite leg. The study aimed to investigate the dynamics of stock through monitoring several indicators by utilizing logbooks, scientific port sampling, and observer data available. The result showed that both relative abundance and estimated catch trend are declining in recent years, a sign that the negative global inclination also influences Indonesian tuna longline fisheries. Further studies are needed to understand whether this phenomenon also impacts other gears. Hence, mitigation on conserving the resource by reducing the catch and strengthening the data collection should be the priority to maintain the livelihood and welfare of many coastal communities.

PRODUKSI DAN PRODUKTIVITAS TUNA OLEH KAPAL TUNA LONGLINE YANG BERBASIS DI PPN PALABUHANRATU

Produktivitas penangkapan tuna dapat dilihat dari produksi penangkapan yang didaratkan di pelabuhan (landing) per upaya penangkapan (effort). Pelabuhan Perikanan Nusantara (PPN) Palabuhanratu menjadi salah satu pelabuhan perikanan yang aktivitas perikanannya tergolong aktif di wilayah pesisir selatan Pulau Jawa dan menjadi salah satu pusat kegiatan perikanan tangkap di wilayah Propinsi Jawa Barat. Produksi ikan tuna di PPN Palabuhanratu mengalami peningkatan yang cukup signifikan dari tahun 2010 sampai tahun 2019. Pada tahun 2014-2018 produksi ikan tuna di PPN Palabuhanratu mengalami penurunan yang cukup drastis. Pada tahun 2019, produksi kembali meningkat menjadi 1,091,612 ton. Landing Per Unit Effort (LPUE) digunakan dalam penelitian perikanan untuk mengindikasikan kelimpahan sumberdaya yang digunakan untuk melakukan stock assessment ketika mengestimasi kelimpahan relatif dari suatu spesies yang dieksploitasi. Komposisi hasil tangkapan tuna oleh kapal tuna longline terdiri atas ikan tuna sirip kuning (Thunnus albacores), tuna mata besar (Thunnus obesus), ikan tuna albakor (Thunnus alalunga). Produksi tuna yang didaratkan di PPN Palabuhanratu dari tahun 2010-2019 mengalami fluktuasi. Pada tahun 2010 produksi ikan tuna sirip kuning sebesar 444,952 ton, ikan tuna mata besar sebesar 979,189 ton, ikan tuna albakor sebesar 122,671 ton. Pada tahun 2019 produksi ikan tuna sirip kuning sebesar 617,992 ton, ikan tuna mata besar sebesar 240,487 ton, ikan tuna albakor sebesar 233,133 ton. Produktivitas tertinggi terjadi pada ikan tuna sirip kuning tahun 2014 dengan nilai LPUE sebesar 6,09 dengan produksi sebesar 2,448,171 ton dengan jumlah effort 402. Produktivitas mengalami fluktuasi setiap tahunnya.