Impacts of fishing,river flow and connectivity loss on the conservation of a migratory fish population

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Changes in life history and ecological characteristics of coral reef fish catch composition with increasing fishery management

Abstract Length, life history and ecological characteristics of landed fish communities were studied over a 10‐year period to test theories of fishing disturbance during a time of increased gear and closure management in heavily utilised fisheries. It was predicted that with greater management restrictions: (1) the earliest and fastest responses in the fishery will be seen in those species with faster turnovers, or relatively lower vulnerabilities to fishing; (2) the fishery would transition to a landed catch with higher mean trophic levels, and greater mean body lengths. In addition, the removal of a non‐selective, small‐mesh seine nets should benefit the catch of gears that previously had the greatest species selectivity overlap with the seine net. Many predictions were supported, although maximum lengths and lengths at maturity responded more rapidly than anticipated. The response to eliminating the non‐selective seine net was a more rapid increase in sizes caught by gears with a larger overlap in size (hook and lines) than species selectivity (gill nets). The simultaneous comparison of management systems over time indicates that open‐access fishing grounds can benefit from restrictions imposed in adjacent fishing grounds. The study indicated that multi‐species coral reef fisheries management objectives of maximising yields, as well as maintaining the fish community’s life‐history diversity, require management trade‐offs that balance local socio‐economic and biodiversity needs.     

Fishery benefits from behavioural modification of fishes in periodically harvested fisheries closures

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Factors influencing fish catch levels on Kenya's coral reefs

Abstract  The factors influencing fish catches on Kenya's coral reefs were studied. Catch data were collected at the species level by counting the number of fish landed at each landing site of each fishing ground. Live coral cover, topographic complexity, fish and sea urchin density, and the number of fishers and gear units used in each fishing ground were compared with catch data. Fishing grounds included one location where only basket traps were allowed, six locations where all gear types were used except beach seines, and three locations where all types of gear, including beach seines, were used. Catch and effort variables were similar across the fishing grounds whereas live coral cover and sea urchin density differed ( P  < 0.01). The sites fished by all types of gear including beach seines had the lowest coral cover (8.4 ± 0.9%) and topographic complexity (1.12 ± 0.01). Catch levels were positively correlated with the number of fishers and fish density but not with the number of gear units deployed or sea urchin density. The number of fishers and live coral cover were the strongest factors determining total catch levels. The results suggest that high levels of fishing effort coupled with the use of destructive gear types, exacerbate the effects of overfishing on Kenya's reefs.     

Changes in a coral reef fishery along a gradient of fishing pressure in an Indonesian marine protected area

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Evaluation of single-pass backpack electric fishing for stream fish community monitoring

Abstract  Data from Lake Ontario tributaries were used to evaluate the efficacy of single-pass backpack electric fishing for stream fish monitoring by: testing the relationship between single-pass catch-per-unit-effort (CPUE) and multiple-pass-based population estimates; comparing species richness estimates derived from single-pass and multiple-pass data and assessing the concordance of fish assemblage patterns described using single-pass and multiple-pass data. Significant correlations were calculated between single-pass CPUE and removal-based population estimates for total catch, 15 species, six taxonomic families, five feeding and four reproductive guilds and tolerant/intolerant species. Strong correlations were more commonly associated with the abundance of individual species than other metrics. Capture probability was not affected by stream size or habitat complexity for most measures. Species accumulation curves and significant correlations ( r ² = 0.9) between single-pass and multiple-pass electric fishing indicate that single-pass surveys provide a representative index of species diversity. In addition, within and among-site variation in fish community composition based on single-pass and multiple-pass data were similar.     

Impact evaluation of spear fishing on fish communities in an urban area of São Miguel Island (Azores Archipelago)

This study was conducted in São Miguel Island (Azores archipelago) providing the first evidence from Macaronesia of spear fishing impacts on fish communities. The shoreline was monitored during 10 months by access point surveys where 220 fishers were interviewed and 27 target fish species were identified. Mean sizes of top predators and highly vulnerable species were generally less than the respective minimum first maturation length. Species intrinsic vulnerability was moderate with an average of 46.7 (max. 100). There are indications that spear fishers, in the absence of high trophic level and larger species, target smaller and lower trophic level fish, atypical of a highly selective fishery. Daily bag limits were not respected in 36.9% of spear fishing operations and 59% of the catch from the area was illegally sold, a practice likely to have negative consequences for the commercial sector.     

Experience counts: Integrating spearfishers’ skills and knowledge in the evaluation of biological and ecological impacts

Fishing experience and skills are not commonly considered in recreational fishery studies. To analyse potential different biological/ecological impacts of three experience levels of spearfishers (novice, intermediate and experienced), access point surveys were conducted over a period of 10 months in São Miguel Island (Azores archipelago). Groups differed in terms of catch rate and composition, species size and vulnerability (i.e. intrinsic vulnerability index of fishes to fishing). Experienced spearfishers explored different areas along the island coast, fished deeper and farther off shore, were more selective regarding fish size and target species, reached higher catch weights and had catches with a higher mean index of vulnerability. Results suggest that catch composition and rate not only depend on fish community and ecosystem health, but also on the expertise of the fishers who operate in a given area. Consequently, scientific studies should consider fishers’ experience in the survey design and data analysis to not over‐ or underestimate their potential impact.     

Relationships between catch and effort in Fijian multispecies reef fisheries subject to different levels of exploitation

Abstract The catch-per-unit-effort (CPUE) and value-of-catch-per-unit-effort (VPUE) of reef-associated fish species from six Fijian native fishing grounds ( qoliqoli ) subject to different fishing intensities were determined using records of fishing activity from a voluntary logbook scheme. Line and spear fishing techniques were used for more than half the total fishing time (h person^-1 d^-1) in all qoliqoli , and yet the favoured technique in a given qoliqoli was frequently less efficient (lower CPUE) than other techniques. The popularity of relatively ineffective fishing methods implies that fishermen did not always attempt to maximize their catch rates. To compare fishing effort in different qoliqoli , all effort was rescaled on the basis of its recorded efficiency (measured as multispecies CPUE) and expressed as hours equivalent to boat-based spear fishing over coral by day to catch fish for sale. Total fishing intensity in the six qoliqoli ranged from 72 to 4310 h km^-2 reef year^-1. The relationship between catch and effort was linear at all fishing intensities, suggesting that the qoliqoli were all fished on a sustainable basis. Furthermore, whilst there was a significant difference in CPUE and VPUE between the one or two qoliqoli with lowest fishing intensity and all the others, there were no significant differences between these other qoliqoli in terms of the VPUE of the saleable multispecies boat catch or the CPUE of species from piscivorous and carnivorous genera ( Epinephelus, Lethrinus and Plectropomus ) which the fishermen prefer to catch.     

基于渔获物统计的中国近海鱼类营养级结构变换及其与捕捞作业的关系

为了解我国东部海域(渤海、黄海和东海)和南海的鱼类生态结构和渔业资源变化特征,本研究在1983—2013年中国海洋渔船渔获统计数据的基础上,首先将渔获物中的鱼类按照营养级归类,然后计算其平均营养级(TL)和Fi B指数,并结合海洋捕捞作业方式,对鱼类的营养级结构长期变化进行分析。结果表明,在东部海域捕捞的25种主要鱼类渔获中,31年间TL呈现下降趋势,低营养层级鱼类比例增长了60%,中营养层级鱼类比例增长了129%,高营养级鱼类则下降了近51%;而在南海,31年间TL变化不明显,低营养级鱼类比例下降了6%,中营养级鱼类下降了43%,高营养级鱼类增长198%。东部海域和南海的渔获物鱼类生态结构变化说明,就营养级水平而言,东部海域近海渔业资源呈现明显的衰退现象,而南海则还未出现这种现象。     

An assessment of catches of shore sport fishing competitions along the coast of the Maltese Islands: Implications for conservation and management

Competitive shore‐based sport fishing is a popular recreational activity in the Maltese Islands. However, prior to this study, no scientific research surveys had been carried out during sport fishing competitions to investigate catches. Collaboration with Maltese sports fishermen was developed to target sustainable management. Recreational fishing catches were recorded between July 2012 and December 2015 by means of 1,633 roving‐access creel surveys, conducted during 79 sport fishing competitions, totalling a fishing effort of 7,548 hr. A total of 29,916 fish belonging to 80 species from 26 different families were caught at a mean catch‐per‐unit‐effort (CPUE) of 4.16 fish angler/hr (SD ± 3.79) and 0.18 kg angler/hr (SD ± 0.17) but with seasonal variation. Catch‐and‐release practices were implemented by all Maltese sport fishing clubs, however, the mean mortality rate stood at 35.5% (SD ± 42.1), indicating that more effort is required to improve survival of fish. The study outcomes provide conservation recommendations.     

Relative importance of habitat and fishing in influencing reef fish communities across seventeen Pacific Island Countries and Territories

Reef fish assessments were undertaken in 17 Pacific islands to describe the status of finfish resources in 63 villages where fishing is mainly artisanal. Surveys were performed by recording the number and size of edible fish species and benthic composition. Fishing impact was described through six proxies representing level of catch, alternative incomes, degree of commercial catch and country economic development derived from a simultaneous socioeconomic assessment. The relative importance of broadly defined habitat (geographical location, island and reef type, substrate composition) and fishing impact in controlling the distribution of fish trophic groups, families and species was measured through multivariate analysis. The extreme faunistic diversity was shown by the large variation in fish density (difference of up to an order of magnitude) and fish biomass (displaying a 20‐fold difference across the region). Herbivores were dominant in the eastern part of the region, at what we classified as complex islands and at islands with small lagoon and at coastal reefs, while carnivores were dominant at oceanic islands and atolls and at outer reefs. Specific habitat associations were shown for Scaridae, Acanthuridae, Siganidae, Balistidae, Lethrinidae, Lutjanidae and Serranidae. Relative importance and size decrease of several fish families (Mullidae, Scaridae, Lutjanidae and Serranidae) were related to high fishing impact. Acanthuridae and Lethrinidae appeared to have a role as opportunistic groups in impacted sites. The relative impact from fishing and habitat on fishes accounted for, respectively, 20 and 30% of variance, demonstrating the effect of human impacts even at such large scale and taking into account only limited fishing impact variables.     

Comparison of three standardised fish sampling methods in 14 alpine lakes in Austria

Abstract Standardised fishing methods using gillnets (EN 14575), electric fishing (EN 14011) and hydroacoustics (WI 00230244 CEN enquiry) to estimate species composition, abundance, biomass and size distribution were compared in 14 alpine lakes >50 ha. More fish species were detected using benthic gillnets (mean = 72.7%) than electric fishing (mean = 59.5%) and pelagic gillnets (mean = 29.6%). For all but two lakes, additional information from a local fisheries manager was required to obtain a complete list of species. Biomass data generated by standardised gillnetting and hydroacoustic surveys were not fully comparable, but a positive correlation was found. Gill netting and hydroacoustics both indicated a nearly fishless habitat below 75 m, which confirmed the maximum required fishing depth according to the European Standard EN 14757. Size distributions obtained from gillnet and hydroacoustic surveys differed statistically for large fish (>40 cm). Each standardised method reflected typical shortcomings. The European standard (EN 14757) should be amended for pelagic fish habitat in deep alpine lakes to include sampling effort corresponding to water volume, and additional gillnets with larger mesh sizes (e.g. 70 mm). Furthermore, the electric fishing standard (EN 14011) should be extended to incorporate requirements of lake fish sampling.     

闽东渔场鱼类资源生态容量和最大可持续开发量

以海洋生态系统营养动力学为理论依据,根据历次调查所获得的闽东渔场初级生产力资料,通过对该渔场浮游植物有机碳含量和生态效率的测算、52种主要鱼类营养级及其有机碳含量的检测,采用营养动态模型和Cushing模型估算鱼类资源生态容量(自然生产量),采用Cadima模式和MSY简单模式估算鱼类资源最大可持续开发量。估算结果:闽东渔场鱼类资源生态容量平均为6.308×10~5t,最大可持续开发量为3.268×10~5t。1994年以来闽东渔场实际年渔获量3.435～4.685×10~5t,平均4.267×10~5t,已连续9年超过鱼类资源最大可持续开发量,呈现过度捕捞态势。必须实行渔获量负增长制度才能使鱼类资源得到有效恢复。     

Shifting trophic architecture of marine fisheries in New Zealand: Implications for guiding effective ecosystem‐based management

New Zealand has led the world in restoration of marine fisheries since the introduction of the Quota Management System in 1986, but challenges remain in minimizing the ecosystem‐level effects of industrialized fishing. We analysed existing long‐term fisheries data sets from 1931 to 2015 in New Zealand to resolve trends in important ecological properties of major exploited fish communities. Increases in community dissimilarities of catch composition in 1931 and 1972, followed by increasing total landings, highlight major expansions of fishing grounds and exploited species during these periods. Mirroring global patterns, the remarkable rise in fishing power, demand and generation of new markets in New Zealand have all contributed to this expansion. Marine Trophic Indices (MTIs) of landings have decreased together with total catch after the year 2000, reflecting smaller catches with a higher composition of lower trophic‐level species in recent years. Differences in relative abundance of species estimated between fisheries‐dependent and fisheries‐independent data were observed, where high‐value species displayed better agreement in relative abundance between data sets. Despite being under a Quota Management System, temporal development of MTI values relative to the timing of industrial expansion of fisheries was remarkably similar to those observed in the North Sea and Brazil, with a single expansion and decline. MTI values presented better long‐term stability in the US fisheries analysed. Analysis of long‐term data and the development of well‐resolved ecological baselines will be the first step towards applying EBM to New Zealand fisheries, in keeping with global trends in fisheries management.     

舟山沿岸渔场春秋季鱼类群落结构特征分析

根据2015年11月(秋季)、2016年5月(春季)在舟山沿岸渔场开展的渔业资源调查中所获得的鱼类资料，采用群聚的物种相似性、多样性指数、RDA分析等方法，对该海域鱼类种类组成、生态类群、多样性和群聚特征进行了分析。结果显示，本调查共鉴定出鱼类81种，隶属于12目39科63属，以近海暖水种为主；Jaccard相似性指数为37.04%，处于中等不相似水平；优势种计算结果显示，春季优势种为六丝钝尾虾虎鱼(Amblychaeturichthys hexanema)，渔获量占总渔获量的42.16%；秋季优势种为龙头鱼(Harpodon nehereus)，占总渔获量的43.56%；春季多样性高于秋季，但2个季节的多样性指数平面分布相似，均为调查海域南部最低，越往北多样性指数越高，且东部海域高于西部海域；ANOSIM检验显示，各群落间差异极显著；相似性百分比(SIMPER)显示，蓝圆鲹(Decapterus maruadsi)、棘头梅童鱼(Collichthys lucidus)、龙头鱼等7种，中华小沙丁鱼(Sardinella nymphaea)、鳀(Engraulis japonicus)、七星底灯鱼(Benthosema pterotum)等9种，分别是春、秋季各组群的典型种及造成鱼类群落结构差异的主要分歧种。RDA研究结果显示，盐度、温度是舟山沿岸渔场鱼类群落结构主要的环境影响因子。     

北太平洋公海秋刀鱼渔场初步分析

根据2004年7~11月“中远渔1号”调查船北太平洋公海秋刀鱼渔场探捕调查的生产情况,对秋刀鱼渔场进行分析。结果发现:①秋刀鱼渔场可根据渔场位置分为北部渔场和南部渔场,北部渔场范围为44°~45°N、156°~158°E,南部渔场范围为41°~42°N、150°~151°E,南部渔场的分布范围小于北部渔场。②秋刀鱼的生产以11月份生产最好,平均日产量达22.7t,其中最高日产量为60.42t;8月份的秋刀鱼生产最差,平均日产量为2.95t,与2003年的12.05t反差较大,主要是由于受到渔场环境因子变化的影响,鱼发位置偏至俄罗斯专属经济区内的缘故。③秋刀鱼舷提网作业平均日放网次数达7.6次,最高1天放网次数达到16次,而最高网次产量为11.05t。④秋刀鱼渔获组成以中小型鱼为主,占80%以上,除7月份渔获中特大型秋刀鱼占有较大比例外,其余月份很少有特大级秋刀鱼。⑤在相近的渔场位置,秋刀鱼个体随着生产月份的推迟,鱼体呈变小的趋势。     

Do recreational fisheries metrics vary on differently sized fishing grounds?

This study aimed to assess the relationship between basic metrics in recreational fishing and the size of the fishing ground. Data were obtained from individual angling logbooks collected by the Czech Fishing Union over 12 years on 212 fishing grounds located in the regions of Prague and Central Bohemia in the Czech Republic. Small fishing grounds had the highest catch, yield, numbers of fishing visits and numbers of angling guard controls per hectare. Medium‐sized fishing grounds had the highest catch, yield, and numbers of both fishing visits and angling guard controls per fishing ground. Anglers returned to medium‐sized fishing grounds most frequently. The percentage of anglers who caught and took home at least one fish decreased with increasing size of the fishing ground. In conclusion, basic metrics in recreational fishing are related to the size of the fishing ground, which thus plays an important role in fisheries management.     

Patterns of fish community composition and biodiversity in riverine fish sanctuaries in Bangladesh: Implications for hilsa shad conservation

Understanding biodiversity and community composition is a prerequisite to sustainable exploitation and conservation of fisheries. We assessed the spatial and seasonal patterns of fish community composition and biodiversity in seasonal no-take riverine sanctuaries in Bangladesh, which aim to conserve the anadromous hilsa shad (Tenualosa spp. and Hilsa keele). Fish samples were collected during monsoon, as well as pre- and postmonsoon, from five sites within two sanctuaries and one site in an open fishing area. Although total abundance was similar along the rivers, species richness was significantly higher at the open fishing site due to its connectivity to nearby habitats. The diversity apparently decreased in a downstream direction. Fish communities at two upstream sites were separated from other sites in multivariate space largely due to higher abundance of hilsa at downstream sites and presence of floodplain-oriented species at the two upstream sites. Short body length and high trophic level at all sites indicated that fish communities were overexploited. Our results also indicated that riverine hilsa sanctuaries in Bangladesh are rich in fish species diversity and support several threatened species designated by the International Union for Conservation of Nature (IUCN). Our study also suggested that since hilsa abundance shapes community patterns, it can therefore impact riverine ecosystem functioning in the sanctuary areas. The findings of this study can serve as an important baseline for future biodiversity assessment, conservation and impact assessment of conservation in rivers, and therefore help to establish multispecies ecosystem-based management of riverine fisheries around the world.     

Effects of fish stocking and fishing pressure on fish community structures in French lakes

Fish stocking and regulation of fishing activities are widely implemented by freshwater fisheries authorities who have to protect aquatic communities. The effects of fish management on fish communities have not received sufficient attention. As a result of two datasets, one from EU Water Framework Directive (WFD) monitoring surveys, and one from a French survey targeting angler's associations, this study investigated the impacts of both fishing intensity and fish stocking on fish communities in French lakes. Both co-inertia analysis and community size spectra analysis, showed that: (i) stocking does not contribute to the standing stocks for five of the six most stocked fish species in France; and (ii) neither fishing intensity nor fish stocking lead to a change in the proportion of large and small fish. The results support alternative methods being promoted to enhance native fish populations.