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1.
Habitat models are used to correct estimates of fish abundance derived from pelagic longline fishing gear. They combine information on hook depth with the species’ preferences for ambient environmental conditions to adjust the gear's catchability. We compare depth distributions of bigeye tuna (Thunnus obesus) catch predicted by a habitat model with distributions derived from data collected by observers on longliners in the tropical Pacific Ocean. Our analyses show that the habitat model does not accurately predict the depth distribution of bigeye tuna; its predictions are worse than those from models that assume no effect of depth on catches. Statistical models provided superior fits to the observed depth distribution. The poor performance of the habitat model is probably due to (1) problems in estimating hook depth, (2) fine‐scale variations in environmental conditions, (3) incomplete knowledge of habitat preferences and (4) differences between the distribution of bigeye tuna and their vulnerability to longline gear. 相似文献
2.
Paolo Casale Lorenzo Cattarino Daniela Freggi Massimiliano Rocco Roberto Argano 《水产资源保护:海洋与淡水生态系统》2007,17(7):686-701
- 1. The fishing effort and turtle catch of vessels harbouring at Lampedusa island and fishing in the wider central Mediterranean area was monitored using a voluntary logbook programme. Two large trawlers were monitored between 2003 and 2005 and six small vessels using trawl nets, pelagic longline or bottom longline were monitored in the summer 2005.
- 2. The observed turtle catch rates of pelagic longline and bottom trawl were among the highest recorded in the basin, and high catch rates by bottom longline were observed too. This suggests that the area contains major oceanic and neritic habitats for the loggerhead turtle Caretta caretta in the Mediterranean Sea.
- 3. When fishing effort is considered, these results suggest a very high number of captures by Italian trawlers and longliners in the area, as well as by fleets from other countries. This is reason of concern for the conservation of the loggerhead turtle within the Mediterranean Sea.
- 4. Different fishing gear have different technical/operational characteristics affecting turtle catch and mortality and the present knowledge about associated parameters of these gear varies too.
- 5. All this considered, specific actions are recommended: (i) an awareness campaign to fishermen to reduce post‐release mortality, (ii) technical modifications to pelagic longline gear to reduce turtle catch, (iii) further investigation into turtle bycatch in all fishing gear, with priority given to bottom longline fishing and quantification of mortality caused by trawlers, (iv) assessment of the turtle populations affected by fishing activity in the area, and (v) international cooperation in undertaking threat assessments, and implementing regulations, management measures and monitoring.
3.
Enhancing the TurtleWatch product for leatherback sea turtles,a dynamic habitat model for ecosystem‐based management 
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下载免费PDF全文 Evan A. Howell Aimee Hoover Scott R. Benson Helen Bailey Jeffrey J. Polovina Jeffrey A. Seminoff Peter H. Dutton 《Fisheries Oceanography》2015,24(1):57-68
Fishery management measures to reduce interactions between fisheries and endangered or threatened species have typically relied on static time‐area closures. While these efforts have reduced interactions, they can be costly and inefficient for managing highly migratory species such as sea turtles. The NOAA TurtleWatch product was created in 2006 as a tool to reduce the rates of interactions of loggerhead sea turtles with shallow‐set longline gear deployed by the Hawaii‐based pelagic longline fishery targeting swordfish. TurtleWatch provides information on loggerhead habitat and can be used by managers and industry to make dynamic management decisions to potentially reduce incidentally capturing turtles during fishing operations. TurtleWatch is expanded here to include information on endangered leatherback turtles to help reduce incidental capture rates in the central North Pacific. Fishery‐dependent data were combined with fishing effort, bycatch and satellite tracking data of leatherbacks to characterize sea surface temperature (SST) relationships that identify habitat or interaction ‘hotspots’. Analysis of SST identified two zones, centered at 17.2° and 22.9°C, occupied by leatherbacks on fishing grounds of the Hawaii‐based swordfish fishery. This new information was used to expand the TurtleWatch product to provide managers and industry near real‐time habitat information for both loggerheads and leatherbacks. The updated TurtleWatch product provides a tool for dynamic management of the Hawaii‐based shallow‐set fishery to aid in the bycatch reduction of both species. Updating the management strategy to dynamically adapt to shifts in multi‐species habitat use through time is a step towards an ecosystem‐based approach to fisheries management in pelagic ecosystems. 相似文献
4.
金枪鱼延绳钓渔获性能主要按目标鱼种和兼捕物种渔获效率进行评价.对其研究有助于改进延绳钓渔具渔法,提高目标鱼种捕捞效率和减少兼捕.本文以时间顺序为主对国内外关于金枪鱼延绳钓渔获性能研究的文献进行梳理,从钓具选择性、钓钩深度、饵料选择性、环境因素以及钓具浸泡时长等方面概括了金枪鱼延绳钓渔获性能的研究进展,并提出存在的不足和... 相似文献
5.
Robust assessments of the effects of fishing require accounting for components of fishing mortality, including post‐release fishing mortality (Fr). Random‐effects meta‐analysis synthesized Fr in seven pelagic shark species captured, tagged and released with 401 pop‐up satellite archival tags compiled from 33 studies and three gears (longline, purse‐seine, rod & reel). The majority of Fr outcomes occurred within days of release, and the summary effect size for Fr was 0.27 [95% CI: 0.19–0.36], ranging from a low pooled effect size of 0.17 for blue shark (Prionace glauca, Carcharhinidae) to 0.38 (silky shark, Carcharhinus falciformis, Carcharhinidae). Fr rates in blue shark were consistent over dissimilar spatial and temporal scales, and results from earlier meta‐analysis were replicated, which is the most powerful way to authenticate results. Condition at tagging was a strong predictor, and dichotomized survival outcomes in silky shark and no sex‐, size‐, location‐ or gear‐specific Fr rates were demonstrated. Meta‐analyses and sensitivity analyses indicated exposure to risk factors and conditions whilst caught on the gear probably had the largest explanatory effect on Fr, rather than stressors incurred during handling and release. Records from 549 tagged istiophorid billfishes (six species, three gears, 43 studies) demonstrated they are more robust to stressors sustained during capture, handling and release than pelagic sharks. Findings from previous meta‐analysis on Fr rates in white marlin (Kajikia albida, Istiophoridae) were replicated. Synthesized Fr rates enable prioritizing approaches to mitigate by‐catch fishing mortality, to improve the quality of stock and ecological risk assessments and to expand our knowledge of factors influencing trophic structure. 相似文献
6.
中东太平洋金枪鱼延绳钓渔获物组成分析 总被引：2，自引：2，他引：2
根据2000年9月至2002年8月两年的中东太平洋金枪鱼延绳钓探捕调查结果,对延绳钓渔获物组成进行了初步分析。结果显示,延绳钓的主要渔获种类有肥壮金枪鱼(Thunnus obesus)和黄鳍金怆鱼(Thunnus albacares)等15种大洋性鱼类,渔获物中金枪鱼类分别占重量和尾数的76．41％和76．91％,旗鱼类占11．05％和7．83％．鲨鱼类占10．80％和12．08％,其他鱼类占1．73％和3．18％。相对重要性指标(IRI)表明,延绳钓渔业以肥壮金枪鱼和黄鳍金枪鱼为目标鱼种,其他大型中上层经济鱼类为兼捕对象。各渔获种类的渔获重量组成比例月间变化和海域变化明显。 相似文献
7.
A new habitat‐based model is developed to improve estimates of relative abundance of Pacific bigeye tuna (Thunnus obesus). The model provides estimates of `effective' longline effort and therefore better estimates of catch‐per‐unit‐of‐effort (CPUE) by incorporating information on the variation in longline fishing depth and depth of bigeye tuna preferred habitat. The essential elements in the model are: (1) estimation of the depth distribution of the longline gear, using information on gear configuration and ocean currents; (2) estimation of the depth distribution of bigeye tuna, based on habitat preference and oceanographic data; (3) estimation of effective longline effort, using fine‐scale Japanese longline fishery data; and (4) aggregation of catch and effective effort over appropriate spatial zones to produce revised time series of CPUE. Model results indicate that effective effort has increased in both the western and central Pacific Ocean (WCPO) and eastern Pacific Ocean (EPO). In the WCPO, effective effort increased by 43% from the late 1960s to the late 1980s due primarily to the increased effectiveness of effort (deeper longline sets) rather than to increased nominal effort. Over the same period, effective effort increased 250% in the EPO due primarily to increased nominal effort. Nominal and standardized CPUE indices in the EPO show similar trends – a decline during the 1960s, a period of stability in the 1970s, high values during 1985–1986 and a decline thereafter. In the WCPO, nominal CPUE is stable over the time‐series; however, standardized CPUE has declined by ～50%. If estimates of standardized CPUE accurately reflect relative abundance, then we have documented substantial reductions of bigeye tuna abundance for some regions in the Pacific Ocean. A decline in standardized CPUE in the subtropical gyres concurrent with stability in equatorial areas may represent a contraction in the range of the population resulting from a decline in population abundance. The sensitivity of the results to the habitat (temperature and oxygen) assumptions was tested using Monte Carlo simulations. 相似文献
8.
Three-dimensional underwater shape measurement of tuna longline using ultrasonic positioning system and ORBCOMM buoy 总被引：1，自引：0，他引：1
Yoshinori Miyamoto Keiichi Uchida Reiko Orii Zhen Wen Daisuke Shiode Toshiharu Kakihara 《Fisheries Science》2006,72(1):63-68
ABSTRACT: The installation depth of the hook in longline fishing gear has previously been measured with micro depth loggers. Research that assumes the catenary shape of longline fishing gear by a simulation based on these data has been done. However, it was not known whether the branch line was tangled with the main line or flowed with the current. In this research, an ultrasonic positioning system generally used to investigate the underwater behavior of marine organisms, and a buoy with a communications satellite, have been used, and the 3-dimensional underwater shape of tuna longline fishing gear was measured. It was possible to monitor changes in fishing gear in real time. The possibility of high precision measurement was suggested with future technical improvement. 相似文献
9.
Bycatch in fisheries has been recognized as a threat to many endangered populations of sea turtles, sea birds and marine mammals. Interactions between pelagic longline fisheries and critically endangered populations of leatherback sea turtles (Dermochelys coriacea) have led to temporary closures of the Hawaiian pelagic longline swordfish fishery and severe bycatch quotas. The negative impact of these events on both the populations of certain endangered species and the economic livelihood of the fishermen has resulted in a strong push from all sides to better understand bycatch events. Typically, analyses of longline catch and bycatch have examined fishing effort summarized over large areas (≥1°). Although aggregation of effort to this level may be necessary to account for uncertainty, confidentiality concerns, or to make comparisons across regions, it specifically limits the researcher's ability to characterize the local oceanographic factors that may drive individual bycatch events. Higher resolution analyses must be undertaken to identify such features. However, for these higher resolution analyses, the methods currently used to spatially represent pelagic longline fishing effort may significantly affect researcher's results. Here, we look at different methods to represent this fishing effort (i.e., points, centroids, polylines and polygons) at various resolutions (2 km to 5°) to better understand which method and spatial resolution are most appropriate. Our results validate the use of point features to represent fishing effort in previous low resolution studies of the Hawaiian pelagic longline fishery by showing that the set point method is suitable for studies with resolutions lower than 15 km. However, at higher resolutions (≤15 km) and in areas with more sparsely distributed fishing, aggregated effort values differed significantly between spatial representation methods. We demonstrate that the use of polygons to describe pelagic longline fishing effort is more representative and necessary for such high resolution analyses. 相似文献
10.
Abstract Southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), is a quota‐managed species that makes annual winter migrations to the Tasman Sea off south‐eastern Australia. During this period it interacts with a year‐round tropical tuna longline fishery (Eastern Tuna and Billfish Fishery, ETBF). ETBF managers seek to minimise the bycatch of SBT by commercial ETBF longline fishers with limited or no SBT quota through spatial restrictions. Access to areas where SBT are believed to be present is restricted to fishers holding SBT quota. A temperature‐based SBT habitat model was developed to provide managers with an estimate of tuna distribution upon which to base their decisions about placement of management boundaries. Adult SBT temperature preferences were determined using pop‐up satellite archival tags. The near real‐time predicted location of SBT was determined by matching temperature preferences to satellite sea surface temperature data and vertical temperature data from an oceanographic model. Regular reports detailing the location of temperature‐based SBT habitat were produced during the period of the ETBF fishing season when interactions with SBT occur. The SBT habitat model included: (i) predictions based on the current vertical structure of the ocean; (ii) seasonally adjusted temperature preference data for the 60 calendar days centred on the prediction date; and (iii) development of a temperature‐based SBT habitat climatology that allowed visualisation of the expected change in the distribution of the SBT habitat zones throughout the season. At the conclusion of the fishing season an automated method for placing management boundaries was compared with the subjective approach used by managers. Applying this automated procedure to the habitat predictions enabled an investigation of the effects of setting management boundaries using old data and updating management boundaries infrequently. Direct comparison with the management boundaries allowed an evaluation of the efficiency and biases produced by this aspect of the fishery management process. Near real‐time fishery management continues to be a realistic prospect that new scientific approaches using novel tools can support and advance. 相似文献
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13.
Paolo Casale 《Fish and Fisheries》2011,12(3):299-316
Sea turtle by‐catch data in the Mediterranean were reviewed and analysed with fishing effort. The results indicate over 132 000 captures per year, with probably over 44 000 incidental deaths per year, while many others are killed intentionally. Small vessels using set net, demersal longline or pelagic longline represent most of the Mediterranean fleet and likely cause more incidental or intentional deaths than large vessels typically using bottom trawl or pelagic longline. When interactions, mortality, intentional killing, size (a proxy for reproductive value) and turtle populations are considered, results indicate that Mediterranean green (Chelonia mydas) and loggerhead turtles (Caretta caretta) are more affected (i) by fishing gears such as bottom trawlers, demersal longlines and set nets, (ii) by small‐scale fisheries, and (iii) by fishing in the eastern basin. Although small‐scale fisheries should be the priority target, available measures are easier to implement on the fewer large vessels. Moreover, these measures are few, and they are not implemented yet, while others should still be tested for the Mediterranean fisheries. Thus, measures for reducing captures or mortality through changing gear‐specific characteristics may help, but probably a more holistic conservation strategy aimed to an ecosystem‐based fishery management for a sustainable fishing would be the only solution for the long‐term survival of Mediterranean Sea turtle populations and their habitats. Small‐scale fisheries should manage marine resources, including turtles, in a responsible and sustainable way. Turtles may not only benefit from but can also help this process if their non‐consumptive value is fully recognized. 相似文献
14.
Temperature and depth associations of porbeagle shark (Lamna nasus) in the northwest Atlantic 总被引：1，自引：0，他引：1
The porbeagle (Lamna nasus) is a large fast‐swimming pelagic shark found at high latitudes in both hemispheres. To examine the influence of temperature on porbeagle distribution, a detailed analysis of the relationship between catch rate, temperature, depth and location was carried out based on 420 temperature profiles taken during commercial fishing operations. More than half of the porbeagle were caught at temperatures of 5–10°C (at the depth of the hook); the mean temperature at gear of 7.4°C differed very little among seasons. Most of the spring fishing took place near fronts, although the affinity with fronts was not evident in the fall. Temperature at depth was a significant modifier of catch rate when included in a generalized linear model controlling for the effects of location, fishing vessel, month and year. However, sea surface temperature was a poor predictor of catch rate. The similarity between environmental and catch‐weighted cumulative distribution functions confirmed suggestions that fishers sought out the most appropriate temperature range in which to set their gear. As porbeagle are among the most cold tolerant of pelagic shark species, we suggest that they have evolved to take advantage of their thermoregulating capability by allowing them to seek out and feed on abundant coldwater prey in the absence of non‐thermoregulating competitors. 相似文献
15.
基于GAM模型分析水温垂直结构对热带大西洋大眼金枪鱼渔获率的影响 总被引：2，自引：2，他引：0
通过模型分析环境变量对延绳钓大眼金枪鱼渔获率的影响,评估适宜垂直活动空间对大西洋大眼金枪鱼延绳钓渔获率的作用。首先采用回归分析检验环境变量对延绳钓渔获率(由单位捕捞努力渔获量(catch per unit fishing effort,CPUE)表示)的影响显著性,结合时空变量,采用GAM(generalized additive model)模型分析各变量对大眼金枪鱼CPUE非线性作用。模型结果表明,环境因子和时空变量对热带大西洋延绳钓大眼金枪鱼渔获率空间分布影响明显。大西洋大眼金枪鱼延绳钓的高渔获率月份出现在夏季和冬季,空间上在赤道以北和30?~50?W。12℃等温线深度对大眼金枪鱼延绳钓渔获率的影响表现为抛物线形状,高渔获率出现在深度较浅的250 m水层,随着12℃等温线深度的增加,大眼金枪鱼延绳钓渔获率降低。温跃层下界深度和深度差对大眼金枪鱼延绳钓渔获率的影响都是穹顶状。随着温跃层下界深度值和深度差由小变大至200 m,延绳钓渔获率递增;温跃层下界深度和深度差超过200 m后,延绳钓渔获率变小。温跃层下界深度和深度差对大眼金枪鱼延绳钓渔获率影响显著的水层分别是200 m和50 m。研究结果显示,12℃等温线深度和温跃层对热带大西洋延绳钓大眼金枪鱼渔获率影响是交叉的,在大眼金枪鱼适宜垂直活动水层受限到和延绳钓作业深度相同时,延绳钓渔获率最高;在适宜垂直活动空间过深或者过浅时,延绳钓渔获率都变小,但可以通过改变作业方式提高渔获率。采用延绳钓CPUE进行渔场和资源评估要考虑金枪鱼适宜垂直活动空间。 相似文献
16.
ANDRIJ Z. HORODYSKY DAVID W. KERSTETTER ROBERT J. LATOUR JOHN E. GRAVES 《Fisheries Oceanography》2007,16(3):240-256
Researchers have applied numerous techniques to improve billfish stock assessments, including habitat‐based models that incorporate behavioral and oceanographic parameters to standardize historical catch‐per‐unit‐effort time‐series data. These methods have allowed researchers to account for significant changes in the depths of pelagic longline (PLL) gear deployments over time. This study presents habitat‐use data recovered from high‐resolution 5‐ and 10‐day pop‐up satellite archival tags (PSATs) attached to 47 surviving white marlin released from commercial and recreational fishing gears offshore of the U.S. East Coast, the northern Caribbean, and Venezuela between 2002 and 2004. Data recovered from transmitting tags indicated that white marlin spent nearly half of their time associated with warm, near‐surface waters (<10 m). All fish displayed frequent short duration (mean: 39.8 min) vertical excursions from surface waters to depths averaging 51 m. Qualitative and multivariate classifications of data from completely transmitted movements of surviving white marlin revealed two major types of descents: one pattern was characterized by deep ‘V’‐shaped excursions of relatively short duration (mean: 23.4 min) while the other featured descents that were more broadly ‘U’‐shaped and confined to a specific depth range for an extended period of time (mean: 75.8 min). Based on the frequency, persistence, and patterns of these vertical movements, white marlin appear to direct a considerable proportion of foraging effort well below surface waters, a behavior that may account for relatively high catch rates of white marlin on some deep‐set PLL deployments. 相似文献
17.
《Fisheries Research》2006,77(2):173-183
Temperature-depth recorders (TDRs) were attached to pelagic longline gear in the Hawaii-based commercial fishery to obtain actual fishing depths and to test the accuracy of catenary algorithms for predicting fishing depths. Swordfish gear was set shallow by typically deploying four hooks between successive floats. The observed depth of the settled deepest hook had a median value of 60 m for 333 swordfish sets. Tuna longline gear deployed more hooks between floats (mean = 26.8), and the observed median depth of the deepest hook was 248 m (n = 266 sets). Maximum gear depth was predicted from estimates of the longline sag ratio and catenary algorithms; however, depth was not predicted for all TDR-monitored sets because estimating sag ratios proved problematic. Swordfish sets had less slack in the main line and correspondingly smaller catenary angles (median = 54.2°) than tuna sets (median = 63.7°). Median values of the predicted catenary depth were 123 m for swordfish sets (n = 203) and 307 m for tuna sets (n = 198). Shallow swordfish sets reached only ∼50% of their predicted depth, while deeper tuna sets reached about 70%. These values indicated that capture depths using traditional catenary equations may be biased without the benefit of TDRs affixed to longlines. Generalized linear models (GLMs) and generalized additive models (GAMs) were developed to explain the percentage of longline shoaling as a function of predicted catenary depth and environmental effects of wind stress, surface current velocity, and current shear. The GAM explained 67.2% of the deviance in shoaling for tuna sets and 41.3% for swordfish sets. Predicted catenary depth was always the initial variable included in the stepwise process, and the inclusion of environmental information in the GAM approach explained an additional 10–17% of the deviance compared to the GLMs. The explanatory ability of the environmental data may have been limited by the scale of the observations (1° in space; weekly or monthly in time) or the geometric (transverse versus in-line) forcing between the environment and longline set. Longline gear models with environmental forcing affecting shoaling may be improved in future studies by incorporating contemporaneous environmental information, although this may restrict analyses to fine-scale experimental longlines. 相似文献
18.
Pascal Bach Laurent Dagorn Arnaud Bertrand Erwan Josse Christophe Misselis 《Fisheries Research》2003,60(2-3):281-292
This study compares detailed, nearly continuous, observations on bigeye tuna, Thunnus obesus equipped with electronic tags, with discrete observations on a larger number of individuals from fishing experiments in order to validate the use of instrumented longlines to study the vertical distribution of fish. We show that the depth distributions obtained from the two different observation techniques regarding different environmental variables (temperature, dissolved oxygen (DO), prey distribution) are similar. Bigeye tuna do not seem to be attracted by baits in the vertical dimension (no modification of their vertical distribution by the fishing gear), which allows the use of instrumented longlines to study the vertical behaviour of pelagic species. This technique, when used with appropriate deployment strategy, could therefore represent an alternative to electronic tags (acoustic or archival tags) when there is a need to determine the vertical distribution of fish species by size or sex, in different environments for the study of fishery interactions. 相似文献
19.
ABSTRACT: The underwater shape and hook depth of tuna longline gear are important factors determining fishing performance. In this study, how the shape of tuna longline gear changes in response to sea conditions and gear rigging is explained. Physical models of underwater gear shape were made to simulate fishing gear and analyzed according to the direction and velocity of currents. Then experiments with small-scale models were conducted in a flume tank to confirm the accuracy of the simulation analysis. Finally, the simulation was examined relative to actual longline fishing gear. This approach provided an improvement over previous analytical methods that did not consider fishing gear shape in response to different sea conditions. A useful result is an improved understanding of the relationship between ocean currents and the configuration of longline gear (the shortening ratio, and number of hooks per basket). These factors affect hook depth which, in turn, affects selectivity. Application of these results could lead to more effective and efficient fishing under different sea conditions. 相似文献
20.
The primary gear type used to harvest coastal sharks in the U.S. Atlantic shark fishery is bottom longline. Recent stock assessments have found several species of coastal sharks in U.S. Atlantic Ocean waters have declined from 60% to 80% of virgin levels. To aid in stock rebuilding, alternative gear restriction measures such as reduced soak time, restrictions on the length of gear, and fishing depth restrictions have been considered but not implemented. In order to evaluate the effectiveness of some of these management measures, controlled experiments were performed using hook timers and time depth recorders, assessing the factors affecting mortality during longline capture for the four most abundant species that incurred at-vessel mortality: sandbar (Carcharhinus plumbeus), blacktip (Carcharhinus limbatus), bull (Carcharhinus leucas), and blacknose (Carcharhinus acronotus). Our results indicate that as hook time and shark size increased mortality rates for the sandbar and blacktip sharks increased. Predicted models indicated mortality rates increased steadily for the three species but appeared to increase the most after 10, 6, and 1 h on the hook for sandbar, blacktip and blacknose shark, respectively. Sandbar sharks larger than approximately 170 cm FL are more susceptible to hooking mortality. Blacknose shark mortality rates increased as hook time increased but bull shark mortality rates were not affected by any factor. The probability of a hook being bitten increased the most between 5 and 12 h after the fishing gear had been set and the mean amount of time hooks were in the water prior to being bitten was 4, 5 and 9 h for sandbar and blacknose sharks, blacktip, and bull sharks, respectively. A significant difference was found between these means for sandbar and bull sharks and between blacknose and bull sharks. Shark species were commonly caught at different temperature and depth ranges. These results could be used by fisheries management to implement restrictions of fishing depth and soak time to aid in the recovery of coastal sharks species. 相似文献