Targeting bigger schools can reduce ecosystem impacts of fisheries

2012 ◽  
Vol 69 (9) ◽  
pp. 1463-1467 ◽  
Author(s):  
Laurent Dagorn ◽  
John D. Filmalter ◽  
Fabien Forget ◽  
Monin Justin Amandè ◽  
Martin A. Hall ◽  
...  
Keyword(s):  
Total Yield ◽  
Substantial Reduction ◽  
Management Approach ◽  
Resource Exploitation ◽  
Free Swimming ◽  
Ecosystem Impacts ◽  
Set Size ◽  
Living Resource ◽  
Tropical Tuna ◽  
Fish Aggregating Devices

Sustainability of living resource exploitation relies on an ecosystem management approach. Within tropical tuna purse seine fisheries using fish aggregating devices (FADs), such an approach incorporates the reduction of bycatch, in particular vulnerable species such as elasmobranchs. The levels of total bycatch (in mass) from fishing operations using FADs is known to be five times higher than when tuna are caught in free-swimming schools. We intend to find practical solutions to reduce bycatch in FAD sets through the investigation of the relationships between the ratio of bycatch to target catch across different set size classes in all oceans. Ratios were always highest when catches were small, with the smallest class of catches responsible for the highest total portion of bycatch (23%–43%) while only contributing negligibly to the total target catch (3%–10%). Reducing the number of fishing sets (a part of the total effort) while maintaining the same total yield could contribute to a substantial reduction in the impacts of human activities.

Behaviour and vulnerability of target and non-target species at drifting fish aggregating devices (FADs) in the tropical tuna purse seine fishery determined by acoustic telemetry

2015 ◽  
Vol 72 (9) ◽  
pp. 1398-1405 ◽  
Author(s):  
Fabien G. Forget ◽  
Manuela Capello ◽  
John D. Filmalter ◽  
Rodney Govinden ◽  
Marc Soria ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Acoustic Telemetry ◽  
Western Indian Ocean ◽  
Purse Seine ◽  
Management Approach ◽  
Target Species ◽  
Tropical Tuna ◽  
Fish Aggregating Devices ◽  
The Vertical Distribution ◽  
Purse Seine Fishery

Characterizing the vulnerability of both target and non-target (bycatch) species to a fishing gear is a key step towards an ecosystem-based fisheries management approach. This study addresses this issue for the tropical tuna purse seine fishery that uses fish aggregating devices (FADs). We used passive acoustic telemetry to characterize, on a 24 h scale, the associative patterns and the vertical distribution of skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye tuna (Thunnus obesus) (target species), as well as silky shark (Carcharhinus falciformis), oceanic triggerfish (Canthidermis maculata), and rainbow runner (Elagatis bipinnulata) (major non-target species). Distinct diel associative patterns were observed; the tunas and the silky sharks were more closely associated with FADs during daytime, while the rainbow runner and the oceanic triggerfish were more closely associated during the night. Minor changes in bycatch to catch ratio of rainbow runner and oceanic triggerfish could possibly be achieved by fishing at FADs after sunrise. However, as silky sharks display a similar associative pattern as tunas, no specific change in fishing time could mitigate the vulnerability of this more sensitive species. For the vertical distribution, there was no particular time of the day when any species occurred beyond the depth of a typical purse seine net. While this study does not provide an immediate solution to reduce the bycatch to catch ratios of the FAD-based fishery in the western Indian Ocean, the method described here could be applied to other regions where similar fisheries exist so as to evaluate potential solutions to reducing fishing mortality of non-target species.

scholarly journals Breaking the Bottleneck: Conflicts Metamorphosis of Chure Landscape Management in Federal Nepal

2018 ◽  
Vol 16 (1) ◽  
pp. 71-86
Author(s):  
Bhola Bhattarai ◽  
Dipak Bishwokarma ◽  
Mathilde Legras
Keyword(s):  
Local Governments ◽  
Community Forestry ◽  
Management Practice ◽  
Landscape Management ◽  
Management Approach ◽  
Resource Exploitation ◽  
Management Options ◽  
Community Conflict ◽  
Environmental Protection Area ◽  
Protection Area

Chure forests, which is one of the youngest and most fragile landscapes of Nepal, continue to be degraded due to resource exploitation and conflict over its management. This region is considered to be the lifeline to down-stream communities - mainly for water - while inhabiting millions of poor and rural people that depend on natural resources - especially forests commons. Government initiatives to manage Chure have escalated contestations in the recent years. Its decision to declare Chure landscape as ‘Environmental Protection Area’ manifests a protection-centric management approach. This research scrutinises the genesis of contestation on Chure management utilising three–elements of conflicts described by Brown et al. (2017). It analyses power–relation to demonstrate potential implications on Chure landscape management as well as conflict resolution options, in the changed political context of federal Nepal. Our research reveals that all stakeholders are well aware of the continuous degradation of Chure landscape and have agreed on discovering the common locus of sustainable management. However, the state-community contestation still persists due to divergent understandings of degradation. Despite multiple strands of management options, contextualised community-based approach still appears to be an appropriate option to solve this persistent contestation, building on the practices of community forestry and historic failures of top-down, protection-centric management practice. The newly elected provincial and local governments could further facilitate a more effective management of Chure landscape through resolving the contentious state-community conflict.

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.

Relationships between set characters and yield in maincrop potatoes

1965 ◽  
Vol 64 (3) ◽  
pp. 361-366 ◽  
Author(s):  
J. K. A. Bleasdale
Keyword(s):  
Unit Area ◽  
Total Yield ◽  
Set Size

1. Data are presented indicating that both the total yield of potatoes and the proportions of the yield in size grades were a function (independent of set size) of the number of main stems per unit area for the maincrop varieties Majestic and King Edward.

scholarly journals KEBIJAKAN RUMPONISASI PERIKANAN PUKAT CINCIN INDONESIA YANG BEROPERASI DI PERAIRAN LAUT LEPAS

2013 ◽  
Vol 5 (2) ◽  
pp. 97
Author(s):  
Duto Nugroho ◽  
Suherman Banon Atmaja
Keyword(s):  
Fisheries Management ◽  
Negative Impact ◽  
Social Dimension ◽  
Potential Conflict ◽  
Fishing Vessels ◽  
Long Run ◽  
Tuna Fisheries ◽  
Tropical Tuna ◽  
Fish Aggregating Devices ◽  
High Seas

<p>Penggunaan rumpon laut-dalam telah mengubah taktik dan strategi perikanan pukat cincin pelagis kecil yang beroperasi di perairan dangkal untuk bergeser pada perikanan tuna neritik tropis. Rumponisasi perikanan pukat cincin yang dirancang untuk meningkatkan produktivitas telah menjadi masalah serius pada perikanan neritik tuna. Hal ini terjadi karena tertangkapnya ikan berukuran kecil dalam jumlah yang dominan sehingga dalam jangka panjang akan berpotensi konflik dengan perikanan lainnya. Para ilmuwan yang tergabung dalam pengelolaan perikanan regional merekomendasikan bahwa pengembangan terkendali terhadap penggunaan rumpon di daerah asuhan juvenile tuna tropis. Pengendalian dalam jangka panjang dapat meminimalkan ancaman bagi kelangsungan hidup kelompok jenis tuna. Hal ini terkait dengan pentingnya memperbesar peluang masuknya sediaan kelompok jenis ini pada tingkat yang layak untuk dimanfaatkan. Di Indonesia, pilihan kebijakan perikanan tangkap baik melalui peralihan sasaran kelompok spesies maupun diversifikasi usaha penangkapan akan selalu bertumpu pada pertimbangan sosial. Bagaimanapun juga, proses mengubah pemahaman nelayan nelalui pengendalian jumlah dan teknologi kapal penangkap ikan serta penutupan sementara daerah penangkapan yang akan melalui proses panjang harus tetap dijalankan untuk mencegah runtuhnya perikanan yang saat ini sedang berjalan.</p><p>The use of Fish Aggregating Devices (FADs) has radically changing the tactic and strategy shallow waters small pelagic purse seiner into high seas tropical neritics tuna fisheries. Applying FADs on purse seine fishery which initiated to increase its productivity became a serious problem to neritics<br />tuna fishery. This indicated by the negative impact on neritics and tropical tuna populations due to large number of small size of tunas being caught and uncertain of number and of FADS position in the high seas. In the long run it will generate a potential conflict to other existing fisheries. The member scientists of regional fisheries management organization (RFMO) recommends that the development of the use of FADs, especially in the area which dominated of juvenile of tropical tuna, should be strongly regulated. FADs management through control system should be applied to minimize impact on recruitment process that associated with the importance of long term availability of its fisheries. Management option through shifting target species and diversification of the fishing activities in<br />Indonesia would always be rely on social dimension. Nevertheles, reorientation on fishers understanding on controllable number of fishing vessels and its technological creeps should strongly be implemented to avoid collapse their existing fisheries.</p>

Waste Minimization Promotes Biophysical Treatment of Complex Petrochemical Wastes in Israel

1994 ◽  
Vol 29 (8) ◽  
pp. 201-208
Author(s):  
A. Lebel ◽  
A. Raveh
Keyword(s):  
Organic Waste ◽  
Waste Treatment ◽  
Substantial Reduction ◽  
Treatment Plant ◽  
Waste Minimization ◽  
Management Approach ◽  
Plant Design ◽  
Sludge Disposal ◽  
Petrochemical Wastes ◽  
Discharge Criteria

A full-scale 300 m3/day industrial waste treatment system was put into operation in a petrochemical manufacturing plant in Israel for the purpose of detoxifying its complex organic waste stream. The GPI treatment plant design incorporates an innovative waste management approach to accommodate the limited space allocated for the facility. It employs influent equalization and waste minimization techniques, in support of an advanced biophysical treatment process to accomplish a substantial reduction in the facility footprint while producing a high quality effluent. Initial performance data indicate a highly efficient organic waste reduction. COD and BOD removal surpassed 95% and 98%, respectively, over the initial two months of operation, meeting the stringent effluent discharge criteria. The system also provides effective sludge dewatering, producing 40-50% solids sludge, thereby minimizing sludge disposal costs.

Comparison of condition factors of skipjack tuna (Katsuwonus pelamis) associated or not with floating objects in an area known to be naturally enriched with logs

2014 ◽  
Vol 71 (3) ◽  
pp. 472-478 ◽  
Author(s):  
Marianne Robert ◽  
Laurent Dagorn ◽  
Nathalie Bodin ◽  
Fabrice Pernet ◽  
Eve-Julie Arsenault-Pernet ◽  
...  
Keyword(s):  
Skipjack Tuna ◽  
Short Term ◽  
Free Swimming ◽  
Katsuwonus Pelamis ◽  
Meeting Point ◽  
Mozambique Channel ◽  
Alternative Hypotheses ◽  
Floating Objects ◽  
The Impact ◽  
Fish Aggregating Devices

In an area that has barely been modified by fish aggregating devices (FADs) (e.g., the Mozambique Channel, known to be naturally enriched with logs, with few FADs), we found that the condition of skipjack tuna (Katsuwonus pelamis) associated with floating objects was lower than those in free-swimming schools. As this result was found in an area that mimics the environmental state prior to the use of FADs, it questions the interpretation of previous studies where such a difference has been interpreted to reflect the impact of extensive FAD deployment on tunas. It is possible that before the use of FADs, tunas associated with logs were also in poorer condition than tunas in free-swimming schools. Our results suggest that the evolutionary reason for which tunas associated with floating objects might not relate to short-term trophic benefit, and alternative hypotheses (e.g., the meeting point hypothesis) are discussed to explain this result.

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