Mortality impact of recreational angling techniques and hook types on Trachynotus ovatus (Linnaeus, 1758) following catch-and-release

We evaluated the post-release mortality (PRM) following catch-and-release in Trachynotus ovatus, one of the main target species of north-western Mediterranean recreational fisheries. In this study, we observed the line-caught fish for 10 d in a holding tank in order to investigate the independence and impact on mortality of several explanatory variables, including fish size, surface temperature, anatomical hooking location, bleeding, hook type, and line cutting. We observed a total PRM of 24.1% and the most important mortality factor by far was the anatomical position of the hook. Anatomically deeper hooking events were highly correlated with fish size and the presence of blood during hooking injuries. The PRM obtained in this study was higher than values reported in previous studies of this species, mainly because we considered the effects of passive angling techniques. Passive angling increased the incidence of deep hooking and consequently increased mortality compared to active angling. This technique also led to an increase in deep hooking by circle hooks. Therefore, we recommend that active angling techniques be encouraged and we emphasize the need for education on the correct use of circle hooks. This study provides guidelines to managers, scientists, and anglers that will promote sustainable development of the recreational fisheries of the Mediterranean.     

Population assessment of sockeye salmon Oncorhynchus nerka caught by recreational angling and commercial fishery in Lake Toya, Japan

ABSTRACT: We carried out mail and access point surveys to estimate the catch numbers, angling effort of recreational angling and the population of sockeye salmon Oncorhynchus nerka in Lake Toya in 1998 and 1999. The mail survey questions in questionnaires distributed to anglers with a recreational angling license included date of angling, caught fish species and size, and catch number. In the access point survey we also asked anglers if they had a license. We measured the fork length and weight of caught fish. The catch rate (catch number in a day by each angler) from both surveys showed no significant difference, suggesting no bias for the catch rate between surveys. The estimated total angling effort was 1760 people (1998), and 1516 people (1999). The estimated recreational catch was 28 889 (1998) and 5455 (1999), that is, two or three times larger than the commercial catch. The fish population was estimated by using the DeLury method as 60 262 (1998) and 10 806 (1999). The total exploitation rate was 62% (1998) and 78% (1999). The size of caught fish was much larger in 1999 than 1998 because of the difference in age composition.     

The Effect of Cyprinid Introductions on Angler Success in the River Derwent, Derbyshire

In an attempt to increase fish standing crop and improve angler-catch, stocking was undertaken in the middle reaches of the River Derwent in Derbyshire using four cyprinid species. Each fish was marked with a dyespot, and nearly 2000 fish were introduced before the 1980–81 fishing season began. Bankside observations and catch return sheets were used to collect information on the number of marked and unmarked fish taken by angling. The percentage of captured fish that were marked reached 50% during summer 1980, although this was lower during winter 1980–81. A relatively small proportion of the fish caught were taken in angling matches. Anglers reported that the fishing had improved from‘poor’to‘good', and catches by a single angler in one day exceeded 20 kg. It is thought that the success of the operation was due to the fact that the stock fish were obtained from local rivers, were of a large size (> 20 cm) and were introduced when the river was at normal level. The implications of the results on management options are considered, and it is suggested that the quality of sport demanded by anglers in rivers of this type may be most easily sustained by periodic stocking with suitable fish.     

Angling for endangered fish: conservation problem or conservation action?

Recreational angling has been implicated in population declines of some marine and freshwater fish, but this activity is rarely considered as a threat or even halted when endangered species are targeted. Indeed, in some cases, anglers are drawn to fish for rare or endangered species. Conservation‐oriented behaviours such as catch‐and‐release are often practiced voluntarily due to the ethics of anglers, yet even in these cases, some fishing mortality occurs. Nonetheless, there are many indirect conservation benefits associated with recreational angling. Here, we present a series of case‐studies and consider whether catch‐and‐release angling for endangered fish is a conservation problem or a conservation action. If recreational angling activities contribute to population‐level consequences that are contrary to recovery strategies, then angling for endangered species would seem to be a poor option. However, as revealed by several case‐studies, there is much evidence that anglers are vocal and effective proponents of fish and habitat conservation, and for endangered species, they are often the only voice when other stakeholders are not engaged. Anglers may contribute directly to conservation actions via user fees (e.g. licences), philanthropic donations or by volunteering in research, education and restoration activities. However, it is important to quantify post‐release mortality as well as understand the full suite of factors influencing a given population or species to know the potential risks. A risk assessment approach outlined in the paper may be used by managers to determine when the benefits of angling for endangered species outweigh the risks.     

Characteristics and economic contribution of a developing recreational fishery in southern Angola

Abstract  The characteristics and contribution of a developing recreational fishery to the local, regional and national economy of Angola were evaluated in 2006. Annual angling effort was 13 435 h, while the estimated total catch of the three target species [leerfish, Lichia amia (L.), west coast dusky kob, Argyrosomus coronus (Griffiths & Heemstra) and shad, Pomatomus saltatrix (L.)], was 5913 fish with a mass of 27 975 kg. Catch per unit effort (CPUE) for all teleost species combined was 0.44 fish per angler h⁻¹ and 2.08 kg per angler h⁻¹. Total harvest of the three species was 576 fish with a total mass of 2221.6 kg. The total contribution of this recreational fishery (mostly anglers from South Africa) to the local economy was US$ 1007 per harvested fish and US$ 243 per harvested kg. This equated to a contribution to the local, regional and national economies of US$ 151 685, US$ 44 767 and US$ 344 364 respectively. Although the regional contribution was less than half of the national contribution, it was regionally significant when the low population density and the general absence of other formal sector employment opportunities are considered. As a result of the largely undisturbed nature of the southern Angolan coastline, the catch, effort and CPUE information was considered suitable as a baseline for a cost-effective method of future fisheries monitoring in the region.     

An examination of the use of angling data to estimate total returns of Atlantic salmon, Salmo salar, to two rivers in Newfoundland, Canada

Conservation spawning requirements (limits) for Atlantic salmon, Salmo salar L., have been developed for a number of rivers in Newfoundland. Status of stocks is evaluated against these limits and scientific advice and recommendations on levels of recreational catch provided to resource managers. A critical factor in this process is the determination of total returns. This has been accomplished for 30–40% of the rivers in question over the years through the use of fish counting fences and traps installed in fishways. In Newfoundland, it is not logistically or financially possible to operate fish counting facilities in all of the approximately 200 Atlantic salmon rivers. Thus angling catch data have been used as an alternative means of estimating total returns to rivers without counting facilities. Estimates of total returns were three to four times higher than the actual values for one of the two rivers studied and deviated from the actual by as much as 60% for the other. Management implications of the approach are discussed.     

An evaluation of a steerable sidescan sonar for surveys of near-surface fish

A towed 330 kHz sector scanning sonar was evaluated for surveys of near-surface migratory salmonids (Oncorhynchus sp.) and other fish in the Strait of Georgia near the mouth of the Fraser River near Vancouver, BC (Canada). Detection of large near-surface fish presents a serious challenge to conventional net trawls or echo-sounder surveys due to vessel avoidance behaviour by the fish. The sonar was towed beside a research vessel on a custom-built towfish at a nominal depth of 18 m. The optimum configuration was determined to be with the sonar scanning a 30° vertical sector oriented perpendicular to the tow direction, at a ping rate of 5 Hz and a sector scan period of 5 s. Fish were detected up to a range of 100 m, limited by systemic noise and backscattered reverberation from the sea surface. Some evidence of vessel-avoidance behaviour by the fish was observed. Near surface temperature and salinity gradients are shown to induce downwards refraction of the sonar beam, resulting in biases in apparent depth and target strength of the fish. A simple model of the sonar performance in this scanning mode, including beam-pattern effects, is used to generate curves of fish target detectability and beam-pattern induced bias as a function of range and fish target strength. After correction for refraction effects, beam-pattern bias, and detectability, the survey results show reasonable agreement with net trawl and riverine escapement data.     

Short-term mortality of Australian bass, Macquaria novemaculeata, after catch-and-release angling

Abstract  Australian bass, Macquaria novemaculeata Steindachner, is angled in large numbers from coastal impoundments and rivers throughout south-eastern Australia. Many are released in the belief that most survive with few negative short-term impacts. This assumption was investigated in three experiments involving a range of conventional angling scenarios. A total of 313 Australian bass were angled and then released along with appropriate controls into either land-based tanks or floating cages, where they were monitored for up to 5 days. No controls died. Short-term mortalities of angled fish were low (0–6%) and attributed to the effects of bait type, hook location and fish size ( P  <   0.05). Specifically, fish that ingested hooks or were caught with natural baits were more likely to die than those that were mouth-hooked or caught on lures. Mortality negatively correlated with fish size. The results supported previous assertions that Australian bass is a resilient, hardy species that should tolerate short-term impacts associated with catch-and-release angling. However, other sublethal physiological impacts that could contribute towards delayed mortalities or reduced reproductive output warrant further investigation, particularly in relation to native populations in coastal rivers that form gauntlet fisheries during their annual spawning season.     

Biological and socioeconomic implications of recreational boat fishing for the management of fishery resources in the marine reserve of Cap de Creus (NW Mediterranean)

A survey of coastal recreational boat fishing was conducted in summer 2006 in the marine reserve of Cap de Creus (NW Mediterranean) to assess the biological and socioeconomic implications of this leisure activity. Recreational boat fishers employ four different fishing techniques: bottom fishing rod, fluixa, trolling and surface fishing rod. Although the targeted species depend on the fishing method used, a total of 33 fish species were identified in the catch (8 were pelagic or benthopelagic and the rest were demersal). Fishing effort was high since fishers fished an average of 4 h/day, 8 days/month and nearly 6 months/year. Apart from the highly varied exploitation of the fauna, recreational fishing in Cap de Creus has a large economic effect on the local economy since the majority of fishers were visitors who were spending holidays in one of the villages belonging to the Park, where most of expenditures related to angling activities were made. Overall, results highlight the pressure that recreational boat fishing exerts on fish communities, particularly on littoral, demersal ones. Considering these biological and socioeconomic implications, the competition between recreational and artisanal fishers for littoral resources and the low level of compliance with the current sport fishing regulations, the implementation of a comprehensive management strategy in Mediterranean costal areas is needed.     

Catching sharks: recreational saltwater angler behaviours and attitudes regarding shark encounters and conservation

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Assessing the value of recreational sea angling in South West England

Abstract  A choice experiment was developed to assess how the value of the recreational sea angling experience in South West England would change as characteristics of the angling experience changed. Catch levels of anglers' favourite species are extremely important, until they reach around six fish per day, at which point anglers become satiated. Anglers are discerning about the species they catch – they would pay only a third as much for increased catches of non-favourite species than for the favourite species. Overall, increasing the size of individual fish would have a larger impact than increasing the catch per day, although this varies by species. In contrast, the presence or absence of rod or bag limits and the environmental quality of a site are only minor factors in anglers' decisions on where to fish. These results will help fisheries managers to identify their goals with respect to sea angling.     

垂钓胁迫对中华倒刺鲃幼鱼群体行为的影响

自然界中鱼类个体因为社会原因集聚的现象称为鱼类群体行为。为考察垂钓胁迫对鲤科鱼类群体行为的影响, 本研究以喜集群的中华倒刺鲃(Spinibarbus sinensis)幼鱼为研究对象, 将大小相近且健康的实验鱼随机分成对照组和垂钓组, 每个处理组包括 18 个鱼群。在(27.3±0.2) ℃水温条件下, 两处理组于垂钓胁迫前(第 0 天)后(第 14 天)在开放水域环境条件下各拍摄 1 次 15 min 的群体行为视频。实验期间, 垂钓组连续垂钓 14 d, 每天垂钓 4 h, 对照组在此期间不进行垂钓。研究发现: (1)垂钓胁迫增加中华倒刺鲃的个体游泳运动速度和个体移动总路程, 降低个体游泳同步性。(2)垂钓胁迫会增加中华倒刺鲃的个体间距离和最近邻距离。(3)虽然垂钓胁迫对中华倒刺鲃的群体运动速度和群体运动时间百分比无影响, 但导致其群体极性下降。(4)中华倒刺鲃的最近邻距离和群体极性呈负相关, 而垂钓胁迫增强二者的相关性。结果表明, 垂钓胁迫降低中华倒刺鲃鱼群的协调性和凝聚力, 对群体运动中个体成员间的信息交流可能产生负面影响。该种鱼群体凝聚力和协调性之间的权衡强度在垂钓胁迫后明显增强, 暗示群体的整体外部轮廓由短梭形向长梭形调整。     

Hydroacoustic assessment of the fish stock in Theodorushaven, a small Dutch harbour

Assessment of the fish stock in the Theodorushaven was conducted with a dual-beam hydroacoustic system. Species composition determined by a seine and trawl fishery showed large concentrations of fish in the harbour during winter. The hydroacoustic survey showed that the distribution of fish in the harbour area was stratified with fish near the bottom. The overall density in the harbour area was 0.67 fish m^–3. The density in the associated channel area was estimated at 0.1 fish m^–3. The coefficient of variation for the estimated total fish abundance was >25%.Fish >25 cm were not caught in the Theodorushaven fishery, although analysis of the sonar data indicated their presence. Fishery data from the adjacent Volkerak-Zoommeer showed that bream was the dominant species. Therefore, the biomass estimate of the stock >25 cm in the Theodorushaven was based on the standard length–weight relationship of bream. This resulted in maximum biomass estimates of 5800 kg ha^–1 for the harbour area and 1100 kg ha^–1 in the channel area. The minimum biomass estimate, based on the assumption that the more slender zander was the dominant species >25 cm, gave values of 4100 kg ha^–1 in the harbour area and 780 kg ha^–1 in the channel area.     

Recreational fishery as a conservation tool for endemic Dolly Varden <Emphasis Type="Italic">Salvelinus malma miyabei</Emphasis> in Lake Shikaribetsu,Japan

Recreational angling is a popular leisure activity globally and can be a threat or useful conservation tool depending on the management strategy. Miyabe charr Salvelinus malma miyabei is an endemic fish that inhabits Lake Shikaribetsu, and a management program was established to harmonise recreational fishery and conservation. To examine the suitability of this program, population assessment was conducted with the cooperation of anglers. The population size in 2014 as assessed by tag-and-release angling was estimated to be 105,300 [95% confidence interval (CI) 37,300–178,600], much higher than the reported estimate in 1995. Further, angling mortality was estimated to be quite low. Moreover, no decreasing population trend was detected on analysing 8 years of anglers’ catch data. Consequently, angling has facilitated stock assessments of Miyabe charr under the current program. This case is a good example of recreational angling acting as a conservation tool under appropriate management.     

The effect of hook/bait size and angling technique on the hooking location and the catch of recreationally caught black bream Acanthopagrus butcheri

The black bream Acanthopagrus butcheri recreational fishery is the largest estuarine fishery in Victoria. This fishery is managed through legal-minimum length and daily bag limits. The success of this management strategy requires a high survival rate for released fish. Deep-hooking is known to reduce the chance of fish survival after recreational capture and release. This study investigated the potential to reduce deep-hooking and the number of under-size A. butcheri caught by varying angling gear and techniques. Three sizes of long shank hook (small [size 8], medium [size 4] and large [size 1/0]) and two angling techniques (slack line and tight line) were tested for their deep-hooking rates and selectivity characteristics. Increasing the hook size from small to large decreased the likelihood of deep-hooking by 6.6 times (95% CI 2.3–16.3 times). Fishing with a tight line instead of a slack line decreased the chance of deep-hooking by almost 100% (95% CI 0.8–3.6). Fishing with a large hook instead of a small hook significantly (F = 6.71, df = 2, P = <0.001) increased the mean A. butcheri length, although this mean size increase was less than 1 cm. This study was able to identify angling gear and angling technique manipulations that reduced the rate of deep-hooking when targeting A. butcheri in Victorian estuaries.     

大型河流中鱼类组成的eDNA监测效率:以长江武汉江段为例

为了探讨大型河流中的 eDNA 监测效率, 以长江为大型河流的代表, 以鱼类为水生生物的代表, 分析传统捕捞监测和 eDNA 监测结果的差异, 研究 eDNA 监测技术对长江武汉江段鱼类组成的监测能力、监测效率、平行样设置等问题。结果显示: (1) 用 1 对 eDNA 宏条形码引物(mlCOIintF/jgHCO2198R)共监测到 89 种鱼类, 其中 30 种可与历史捕捞调查记录互相确认, 另外 59 种需要更完善的条形码数据库来解决序列比对注释问题; (2) 9 月在武汉监测断面, 可用单引物(mlCOIintF/jgHCO2198R) eDNA 监测到的物种最优估计约 99 种, 单样品 eDNA 监测的鱼类物种检出能力约为 26 种, 检出效率约为 25.8%; (3) 在 80%的检出度目标下, 需要约 10 个平行样, 在 95%的检出度目标下, 需要约 17 个平行样。本研究在长江武汉江段鱼类 eDNA 监测效率和平行样设置的相关量化结果可为长江其他断面及其他大型河流的 eDNA 监测提供量化参考。同时, 本研究表明, 更完善的 DNA 宏条形码数据库和合适的平行样设置是未来 eDNA 监测作为常规监测手段进行运用的前提。     

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.     

An assessment of catches and harvest of recreational shore angling in the north of Portugal

Abstract  Recreational shore angling in the Atlantic Ocean between Moledo and Aveiro (Portugal) was examined using roving creel surveys (March/September 2001). Cooperation was high (90% of 2310 anglers approached). At least 39 species of fish were caught at a rate of approximately 0.5 fish angler h⁻¹. An estimated 7319 kg of Dicentrarchus labrax (L.), with 45.6% below the minimum legal size, and 2040 kg of sea breams (genus Diplodus ), correspond to 5.75% and 1.19% of the commercial landings in the same geographical area, respectively. The results shed light on a number of issues relevant to integrated coastal management, including temporal and spatial distribution of fishing effort, species caught, sizes of fish, catch rates, and factors influencing catches and angler satisfaction. Whilst the results suggest that the catches of sea breams and sea bass by day-time recreational shore angling in northern Portugal are small compared with commercial fishing, other recreational activities, such as boat fishing and spear-fishing, must be assessed.