Annual Catch Data Research Articles

Demographics and exploitation of two Near Threatened freshwater eels, Anguilla bengalensis and Anguilla bicolor, in small‐scale subsistence fisheries and implications for conservation

Abstract Tropical freshwater eels (Anguilla bengalensis and Anguilla bicolor) contribute a major share of the world's wild‐caught eel production, having become the next major target owing to the declines in availability of both Anguilla japonica and Anguilla anguilla, species that have traditionally contributed to eel aquaculture and trade. Although both A. bengalensis and A. bicolor are assessed as Near Threatened on the International Union for Conservation of Nature Red List, these assessments are primarily based on anecdotal information and local knowledge on population declines. Demographics and exploitation levels of A. bengalensis and A. bicolor were determined from small coastal river systems, and their adjoining aquascapes in the Western Ghats hotspot of southern peninsular India, and the value of these data for future conservation planning discussed. The computed estimates of annual catch data for freshwater eels from the study region are between 0.17 (A. bicolor) to 0.30 t (A. bengalensis). Virtual population analysis of exploitation showed a drastic decline (in number) in the length groups >45 cm for both species, suggesting that they were less likely to attain their asymptotic length in the region. Current exploitation rates of A. bengalensis are unsustainable, and those for A. bicolor are almost close to reaching this level. Exploitation of all life stages from yellow eels to adults (29–171 cm) is likely to cause recruitment failure and significant mortality of spawning individuals of both species. An integrative conservation approach, including raising awareness (leading to voluntary restrictions), fishing closures in reservoirs, village‐level quotas, and regular monitoring of populations, will ensure a sustainable future for the freshwater eel species in the Western Ghats hotspot, and elsewhere in the tropics where these species are exploited.

A Comparison of Three Data-Poor Stock Assessment Methods for the Pink Spiny Lobster Fishery in Mauritania

Several data-poor stock assessment methods have recently been proposed and applied to data-poor fisheries around the world. The Mauritanian pink spiny lobster fishery has a long history of boom and bust dynamics, with large landings, stock collapse, and years-long fishery closures, all happening several times. In this study, we have used catch, fishing efforts, and length-frequency data (LFD) obtained from the fishery in its most recent period of activity, 2015–2019, and historical annual catch records starting in 2006 to fit three data-poor stock assessment methods. These were the length-based Bayesian (LBB) method, which uses LFD exclusively, the Catch-only MSY (CMSY) method, using annual catch data and assumptions about stock resilience, and generalised depletion models in the R package CatDyn combined with Pella-Tomlinson biomass dynamics in a hierarchical inference framework. All three methods presented the stock as overfished. The LBB method produced results that were very pessimistic about stock status but whose reliability was affected by non-constant recruitment. The CMSY method and the hierarchical combination of depletion and Pella-Tomlinson biomass dynamics produced more comparable results, such as similar sustainable harvest rates, but both were affected by large statistical uncertainty. Pella-Tomlinson dynamics in particular demonstrated stock experiencing wide fluctuations in abundance. In spite of uncertain estimates, a clear understanding of the status of the stock as overfished and in need of a biomass rebuilding program emerged as management-useful guidance to steer exploitation of this economically significant resource into sustainability.

The value of estuarine producers to fisheries: A case study of Richmond River Estuary.

Nutrient input from estuarine producers underpins coastal fisheries production and knowing which producers are the most responsible for fish diet helps effectively protect and restore coastal ecosystems. Focussing on the Richmond River in Australia as a case study, we sampled the main estuarine producers and estimated their proportional contributions of nutritional input to seven commercially important fisheries species using Bayesian isotope mixing models. We valued the dietary input of estuarine producers to the commercial fisheries by combining dietary contribution estimates with total annual catch data from commercial fishers. A conservative estimate is that estuarine producers in the Richmond River Estuary contribute at least 82 725kg (78%) of the total annual catch of the seven commercially important fish with an estimated annual value of $AU 450 117. Sea mullet and Mud crab contributed 95% of the total catch, and 93% of the total value assigned to estuarine producers. The two highest valued estuarine producers were tidal marsh (Juncus kraussii) $AU 82 432 and seagrass (Zostera capricorni) $AU 65 423. This study demonstrates the substantial role of estuarine producers to commercial fisheries production and the fisheries economy more broadly. With large areas of estuarine producers under threat globally from land clearing for agriculture, aquaculture and urbanisation, the results presented here provide evidence to support the value of coastal habitats and benefits of their preservation and restoration.

Stable isotopes infer the value of Australia’s coastal vegetated ecosystems from fisheries

AbstractWild capture fisheries provide substantial input to the global economy through employment and revenue. The coastal zone is especially productive, accounting for just 7% of the total area of the ocean, but supporting an estimated 50% of the world's fisheries. Vegetated coastal ecosystems—seagrass meadows, tidal marshes and mangrove forests—are widely cited as providing nutritional input that underpin coastal fisheries production; however, quantitative evidence of this relationship is scarce. Using Australia as a case study, we synthesized fisheries stable isotope data to estimate nutritional input derived from coastal vegetated ecosystems and combined these “proportional contribution” estimates with total annual catch data from commercial fisheries to determine species‐specific dollar values for coastal vegetated ecosystems. Based on the data from 96 commercially important fish species across Australian states (total landings 14 × 106 tonnes pa), we provide a conservative estimate that Australia's coastal vegetated ecosystems contribute at least 78 million AUD per year to the fisheries economy. Two thirds of this contribution came from tidal marshes and seagrasses that were both equally valued at 31.5 million AUD per year (39.4%) followed by mangroves at 14.9 million AUD per year (18.6%). The highest dollar values of coastal ecosystems originated from eastern king prawn (Melicertus plebejus) and giant mud crab (Scylla serrata). This study demonstrates the substantial economic value supported by Australia's coastal vegetated ecosystems through commercial fisheries harvest. These estimates create further impetus to conserve and restore coastal wetlands and maintain their support of coastal fisheries into the future.

Estimate of sustainable yield of blue shark ( Prionace glauca ) in the Indian Ocean using data-poor approach

PDF HTML阅读 XML下载 导出引用 引用提醒 运用数据缺乏方法估算印度洋大青鲨可持续渔获量 DOI: 作者: 作者单位: 1. 上海海洋大学 海洋科学学院, 上海 201306;2. 农业部大洋渔业开发重点实验室, 上海 201306 作者简介: 耿喆(1993-),男,硕士研究生,从事渔业资源评估、渔业生态学研究.E-mail:gengzhe1993@sohu.com 通讯作者: 中图分类号: S931 基金项目: 国家自然科学基金项目（41676120）. Estimate of sustainable yield of blue shark (Prionace glauca) in the Indian Ocean using data-poor approach Author: Affiliation: 1. College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China;2. Key Laboratory of Exploitation of Oceanic Fisheries, Ministry of Agriculture, Shanghai 201306, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:运用数据缺乏方法，即基于资源衰减的可持续渔获量估算模型（DCAC），结合Monte Carol模拟，对印度洋大青鲨（增大或最大可持续产量对应的捕捞死亡系数（）增大；若呈减小趋势。资源丰度指数的选择对DCAC结果有较大影响，基于日本延绳钓渔业1998-2014年和2001-2014年两个时间序列的丰度指数得到的结果可靠，且与其他模型估算的MSY值接近。2014年印度洋大青鲨的年渔获量正好处在或略高于最大可持续产量（MSY）水平，但该结果仍具有一定的不确定性。本研究表明运用DCAC方法估算印度洋大青鲨可持续渔获量是可行的，但对其他鲨鱼种类的适用性仍需进一步研究，该结果可为数据缺乏方法在大洋和中国近海渔业中的应用提供参考。 Abstract:Sharks occupy the top trophic level in the marine community and play an important role in maintaining ecosystem stability and diversity. The stock status of shark species is often difficult to assess by formal stock assessment methods due to limited fishery data. Blue shark () is the most widely distributed pelagic shark species in tropical and temperate oceanic waters. This species is often caught as bycatch in oceanic longline fisheries that target billfishes and tunas, and also in the artisanal longline fisheries that operate in coastal areas such as Chile. Because of its slow growth and late maturity, the blue shark is defined as "Near Threatened" globally in the IUCN species list. Determining the stock status of Indian Ocean blue shark using a data-poor approach has been assigned as a high research priority by the Indian Ocean Tuna Commission. In this study, we assessed the Indian Ocean blue shark stock status using the depletion-corrected average catch (DCAC) approach and Monte Carlo simulation. DCAC is a data-poor approach that only needs basic biological information (natural mortality, was estimated by the Hoeing method, resulting in a mean of 0.05. In addition to the annual catch data, the application of DCAC also needs the means and standard errors of the following parameters:depletion of the biomass (. First, we estimated the sustainable yield () of blue shark using abundance indices (standardized catch per unit effort[CPUE] time series) derived from different longline fleets (i.e., Spain, Portugal, Japan, and Taiwan, China). Second, we evaluated the sensitivity of DCAC by considering multiple combinations of different levels of , CPUE indices, and lengths of time series of data. Lastly, we summarized the estimated values and compared our estimates with the results from other assessment approaches for this species. The results showed that when FMSY/M when was close to zero or negative. The results were sensitive to the CPUE index. The estimated was reliable and close to the maximum sustainable yield (estimated from other assessment models) when the Japanese longline CPUE index (1998-2014 or 2001-2014) was used. The current (2014) annual catch of blue shark might be at or just above the estimated maximum sustainable yield, although the estimate is subject to uncertainties. This study suggests that DCAC is suitable for estimating the of Indian Ocean blue shark using catch data and CPUE indices as the main sources. This study also provides guidelines for the application of data-poor approaches in domestic fisheries of China. 参考文献 相似文献 引证文献

COST-EFFECTIVE APPROACH TO ESTIMATE UNREPORTED DATA: REBUILDING HISTORY OF LIFT-NET FISHING IN KWANDANG WATERS

This paper aims to develop cost-effective approach regarding the estimation unreported annual catch data of lift-net fishery using Google Earth imagery. Lift net fishery is one of the main fishing activities of coastal community in Kwandang Bay, it has been faced problem of uncertain fisheries status due to limited recorded data. Combination of a Monte Carlo procedure was applied by involving couple of assumptions on parameters such as estimate growth rate of the total number of lift-net per years (10%), day at sea per unit per month (21 days) and operated lift-net per month (50% and 80%). The results showed that 101 units of lift-nets were found around Kwandang waters based on Google Earth imagery recorded in October, 7th 2010, and this were used as a benchmark of calculation. This prediction was 28 units higher than official data from North Gorontalo District of Marine Affairs and Fisheries Services (DKP Gorontalo Utara). Compared with capture fisheries statistics issued by Kwandang CFP, the estimated lift-net catches based on two-scenarios represent additional catches of 46 % and 86 %. These results suggested and could be used as a correction index to improve the reliability of Kwandang District officially reported fisheries statistics as a baseline to develop a local common fisheries policy.

Dietary change in Cape gannets reflects distributional and demographic shifts in two South African commercial fish stocks

Abstract Seabirds are upper trophic level predators, and are often highly sensitive to changes in the availability of their prey. Altered prey assemblages resulting from fluctuations in oceanographic conditions may be mirrored by shifts in seabird diet. Long-term studies of dietary change in seabirds therefore provide valuable insight into the nature of environmental shifts within the systems in which they forage. In recent decades, the Agulhas region in South Africa has undergone significant oceanographic change related to warming and intensification of the Agulhas current. Concurrent with this change, the population of Cape gannets Morus capensis at Bird Island, Algoa Bay, has grown rapidly, probably as a result of an increased availability of its dominant prey items, sardine Sardinops sagax and anchovy Engraulis encrasicolus. Using one of the longest and most complete time-series available on diet of a seabird (spanning 34 years), we tested for changes in composition and the abundance of dominant prey species of this population. These observed changes were also compared with acoustic survey estimates of their biomass, and annual catch data. Since 1979, the prey composition has remained similar, but the dietary contribution of sardine and anchovy, which fluctuated inversely to each other, increased over the study period. These shifts seem to be reflective of fluctuations in the stock size of sardine and anchovy. Conversely, a third species, saury Scomberesox saurus, dominant in the non-breeding diet of the 1980s, decreased significantly in dietary abundance over the following two decades. It is likely that dietary shifts of Cape gannets at Bird Island were related to climate-mediated oceanographic change. The implications of such changes are discussed.

한국 동해안 기름가자미(Glyptocephalus stelleri)의 자원평가 및 적정어획량 추정

The blackfin flounder Glyptocephalus stelleri is a commercially important species in the East Sea of Korea, but its catches and biomass have decreased gradually in recent years. This study estimated the optimal catch (acceptable biological catch, ABC) for the effective management of this species by estimating population ecology parameters and the stock biomass of blackfin flounder in the East Sea of Korea. The estimated instantaneous coefficient of total mortality (Z) of blackfin flounder was 1.0542/year, the survival rate (S) was 0.3485, and the instantaneous coefficient of natural mortality (M) was 0.3637/year. From the values of S and M, the instantaneous coefficient of fishing mortality (F) was calculated to be 0.6905/year. The age at first capture was 1.304 years, and the total length was 11.5 cm at that time. On the basis of these parameters, the annual biomass was estimated by a biomass-based cohort analysis using annual catch data in weight by year for 1991-2012 in the East Sea of Korea. The annual biomass peaked in 1997 at about 12,800 mt and then subsequently declined continuously to a level of 10,500 mt in 2004 and to 9,800 mt in 2011 and 2012. The maximum sustainable yield and <TEX>$F_{0.1}$</TEX> were estimated as 3,547 mt and 0.3595/year, respectively. Using these estimations, the ABC was estimated to be 3,571 mt in tier 5, 3,397 mt in tier 4, and 2,622 mt in tier 3.

한국 근해 쌍끌이대형저인망어업의 어종군집 분석

The fishing grounds of Korean large-pair trawlers have shifted since exclusive economic zones (EEZs) were established in a fisheries agreement involving countries neighboring Korean waters. The distributions of marine ecosystems and fisheries resources have been changing with environmental changes such as global warming and with the shift in species targeted as a result of changes in fishing technology and fishing gear. This study analyzed variation in the species assemblages caught in Korean waters by large-pair trawlers as a result of these geopolitical and environmental changes. The data used in this study were obtained from the Fishery Production Statistics of Korea and the Port Sample Survey of the National Fisheries Research and Development Institute (NFRDI) from 1990 to 2007. Hierarchical clustering analysis (HCA) and correspondence analysis (CA) were used to explore the characteristics of the catch-species composition. The overall variation in the species composition of the catch of Korean large-pair trawlers showed that the proportions of croaker Johnius grypotus, small yellow croaker Larimichthys polyactis, eel Anguilla japonica, and blue crab Portunus trituberculatus decreased, whereas those of hairtail Trichiurus lepturus, Spanish mackerel Scomberomorus niphonius, anchovy Engraulis japonicus, and common squid Todarodes pacificus increased in Korean waters over the 18-year period. The results of the HCA of the annual catch data by species showed four different distributions of fish species according to year. Results of the CA showed that the species assemblages differed between the 1990s and 2000s.

APPLIED ISSUES: Size‐dependent mortality of migratory silver eels at a hydropower plant, and implications for escapement to the sea

Summary1. The European eel population has decreased drastically during recent decades, and new EU‐legislation calls for measures to change this negative trend. This decline has been attributed to a number of factors, including habitat fragmentation by structural barriers that prevent eels moving between freshwater and the sea. The success of downstream migrating adult silver eels migrating past a hydroelectric plant (HEP) in Sweden was examined by radio‐telemetry, and the results were considered in a historical context by analysing catch data from the river for 1957–2006.2. The choice of routes and passage success were quantified for three treatment groups and one control group of silver eels. The first treatment, the reservoir group (n = 50), was released into the reservoir upstream of the HEP, and these fish could proceed downstream by passing through the HEP (20 mm rack and turbines) or by entering the spill gates into the former channel, bypassing the HEP. The second treatment group (inside rack, n = 15) was released downstream of the 20‐mm rack and had to pass through the turbines to continue migration to the sea. The third treatment group consisted of dead radio‐tagged eels (n = 6) that were released into the turbines to study the extent of drifting by dead individuals. Finally, the control group (n = 50) was released downstream of the HEP to test for effects of confounding factors.3. Most live individuals displayed migratory behaviour and continued to proceed downstream after release. Only 8% of the fish released in the reservoir or downstream of the HEP (control) did not migrate. The probability of reaching the next HEP, 24 km further downstream, was high for the control group (96%) and the reservoir‐released individuals that passed the HEP via the spill gates and the former channel (83%). Survival was low and size‐dependent for the individuals that passed the turbines (40%) and even lower for the individuals that had to pass through the rack and the turbines (26%). The overall passage success for eels released in the reservoir was 30%, including both routes.4. Annual catch data from 1957 to 2006 showed that the number of eels in the River Ätran has decreased. Despite this decrease, escapement biomass has remained unchanged, because of the fact that the mean size of eels has doubled. Passage data from 2007 show that changes in size and abundance have resulted in a reduction of relative escapement to the sea to values that are 21–24% of what they were in 1957–66. However, this low level of escapement could potentially be rectified if appropriate measures facilitating HEP passage are successfully implemented, since the potential escapement biomass in the river, owing to the large size of the eels, has changed little since the 1950s.

Translocation of marbled African lungfish, Protopterus aethiopicus (Telostei: Protopteridae), and its fishery in Lake Baringo, Kenya

The translocation of the marbled African lungfish Protopterus aethiopicus into Lake Baringo created a new fishery for the local community, who capture them primarily in a bottom-set long line fishery. Its introduction, development and current fishery status in the lake are documented. Annual catch data were obtained from the District Fisheries Office, while catch and effort data of the long line fishery were recorded at one active fish-landing site between February and October 2001. Lungfish comprise a significant component of commercial landings, sometimes exceeding catches of the Baringo tilapia Oreochromis niloticus baringoensis as the most landed species by weight. Daily catch rates and effort varied considerably, ranging from 5.51–15.18kg day−1 and from 50–590 baited hooks day−1, respectively. Daily catch per fisher ranged from 0–35.72kg, while the overall mean catch per unit effort (CPUE) was only 0.003kg per hook-hour. This study provides the only baseline CPUE data for a lungfish long line fishery that the authors are aware of, for comparison with future studies in this or other lakes where lungfish are similarly exploited. Recommendations for improved management and the maintenance of a viable lungfish long line fishery in Lake Baringo are presented.