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Book (series)Bycatch in longline fisheries for tuna and tuna-like species: a global review of status and mitigation measures 2014
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No results found.This publication is the third in a series on bycatch in global tuna fisheries. Dealing with longline fisheries, its scope is defined taxonomically to comprise only non-tuna and non-tuna-like species. The history of longline fishing illustrates the role of new technologies, the expansion of fishing grounds, and the operational characteristics of the fleets in shaping today’s fishery. More recently, management regulations, the price of oil, the cost of labour, and market demand have also exerted a n influence. No more than 23 percent of the tuna in each ocean is longline-caught. However, there may be up to 7 500 tuna longliners globally with almost 60 percent of them less than 24 m in length. Available data suggest that elasmobranch catches have fallen 14 percent since their peak in 2003. In longline fisheries, shark catch rates may be determined by bait type, soak time, hook shape, leader length and material, depth at which the hook is fished, and whether special gear is deployed to targ et sharks. Vulnerability to hooking, and resilience to haulback and handling, vary by species, size, area and fleet operational practices. Tuna regional fisheries management organizations (t-RFMOs) assess the status of shark populations but data limitations often hinder firm conclusions. There is little information on the implementation or effectiveness of finning bans and no-retention measures. Mitigation measures have been tested but results vary. Six of the seven species of sea turtles are th reatened with extinction, and while longline fisheries may have less impact than net-based fisheries, significant populationlevel impacts may be occurring in some regions. The greatest concern is associated with loggerhead–longline interactions in the Atlantic. Circle hooks and using finfish bait have proved effective mitigation techniques either by reducing hooking or hook swallowing. Other methods require further development. Interactions with pelagic longline fisheries kill 50 000–100 000 sea birds annually. Many of these species, particularly albatrosses, are threatened with extinction. Recent advances in tracking technologies have facilitated mapping of where interactions are most likely. The Western and Central Pacific contains more than 45 percent of the global total albatross and giant petrel breeding distributions. The most promising mitigation methods appear to be night setting, side-setting, line weighting and streamer lines, but further research is needed. All five t-RFMOs r equire use of one or more of these methods in areas that overlap albatross distributions. However, compliance data are limited and improved observer coverage is essential. Marine mammals’ interactions with longline fisheries are detrimental to the fishery but may be positive or negative for the mammals. Although it is often unclear which species are involved, pilot whale interactions in the western Atlantic and false killer whale interactions off Hawaii have triggered national mitigation plans. No t-RFMO has adopted management measures for marine mammal interactions. Research and testing of mitigation measures continue in order to ameliorate both marine mammal impacts and economic losses to industry from depredation. At least 650 species of other bony fishes may be caught in association with pelagic longline fisheries, e.g. dolphinfish, opah, oilfish, escolar and ocean sunfish. Some of these stocks are important as local food supplies. However, it is unclear whether these stocks or the ecosystem they help structure is at risk. More attention should focus on improving fishery statistics and initiating basic monitoring of these stocks’ status. The diversity of pelagic longline gear designs and fishing methods, the variety of habitats they are deployed in, the thousands of marine species they may interact with, v and the different mechanisms and behaviours that govern those interactions provide an array of topics to be addressed in any discussion of bycatch mitigation. Scientifi c and technical issues in mitigation including effects across taxa, effects of combinations of measures, economic and safety considerations, underlying biological mechanisms, handling and post-release mortality, and non-fishery impacts must all be addressed. In addition, it is also necessary to consider issues such as who takes the lead for ensuring mitigation is sufficient for the population as a whole, how to devise effective mitigation implementation strategies, and whether gear modification should be used in concert with more sweeping measures. -
DocumentImprovements in airborne laser scanning-based forest structural type assessment
XV World Forestry Congress, 2-6 May 2022
2022Also available in:
No results found.Accurate forest structural types (FSTs) assessment helps to provide valuable support tools to distinguish different structures in forest stands and formulate effective management decisions. We used data from -Boreal, Mediterranean and Atlantic- biogeographical regions and developed reliable methodologies for the FSTs assessment. First, we used the Gini coefficient (GC) of tree size inequality and evaluated the effects of plot size, stand density and point density of the airborne laser scanning (ALS) on the ALS-assisted GC estimations in Boreal conditions. Second, we used four structural variables -quadratic mean diameter (QMD), GC, basal area larger than mean (BALM) and stand density (N)- from the three biogeographical regions and developed region-independent methods for the FSTs assessment. Lastly, we detected FSTs directly from ALS data, predicted the aboveground biomass (AGB) at each FST, and compared it with the AGB prediction without pre-stratification. Results showed that (a) plot size had a greater effect on the ALS-assisted GC estimation as compared to the stand and point density and 250-450 m2 plot size is the optimal plot size for reliable ALS-assisted GC estimation. (b) GC and BALM were the most important descriptors for the FSTs assessment and single storey, multi-storey and reversed-J types of forest structures can be separated by lower, medium and high values of GC and BALM, respectively, while QMD and N were relevant to separate young/mature and sparse/dense subtypes.(c) We observed marginal improvements in the AGB predictions from the direct ALS-based FSTs but identified critical differences in the selection of ALS metrics by the prediction models such as higher percentiles are more relevant in the open canopies while cover metrics and average percentiles are important in the closed canopies. These results are thus very useful in improving our understanding on the causality behind the choice of ALS predictors in structurally complex forests. Keywords: Sustainable forest management, Monitoring and data collection, Biodiversity conservation, Research ID: 3621963 -
ArticlePredicted climate change impact on natural teak forests in the Greater Mekong sub-region
XV World Forestry Congress, 2-6 May 2022
2022Also available in:
No results found.Teak (Tectona grandis) is one of the most valuable hardwood species. Natural teak forests, largely distributed in South Asia and Southeast Asia, but they are in danger because of over-exploitation, non-sustainable management, encroachment, and potentially the long-term effect of climate change. The objectives of this research are to predict the presence and future geographical range of natural teak forests in the Greater Mekong Sub-region, and to determine the effectiveness of protected areas for in-situ conservation. Geo-referenced species occurrences of natural teak across the Mekong region were gathered from previous studies and ongoing ITTO Teak Project in Mekong. In addition, potential environmental requirement variables were developed or gathered from various sources. Maximum Entropy (MaxEnt Model), a present-only spatial distribution model was employed to generate present and predicted species range in 2050 under the CMIP6 scenarios. The results of species distribution models show that the suitable habitats of native teak are likely stable by 2050 as the result of wide climatic tolerance range. However, its distribution in southern Myanmar and northeast Lao PDR would loss climatic suitable habitats, whereas semievergreen forests in northern Myanmar are becoming more suitable by all scenarios. Keywords: Distribution range, teak, conservation, Mekong, protected areas ID: 3486560
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