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The effects of environmental factors and fisheries management on recreational catches of perch Perca fluviatilis in the Czech Republic
Abstract
The Eurasian perch Perca fluviatilis is an important fish species in both commercial and recreational fisheries. However, there is concern that perch populations in Central Europe are decreasing. This study aimed to assess the effects of environmental factors and management on recreational perch catches. Data from individual angling logbooks collected by the Czech Fishing Union on 229 fishing grounds during 2005-2016 were used in this study. In total almost 60 000 perch weighting 17 500 kg were recorded. During the study period, total perch catches decreased by 60 %, catch per fishing visit decreased by 70 %, average body weight of caught perch increased by 18 %, and percentage of fishing grounds with perch catches decreased by 13 %. The results indicated that the decreasing catches were due to increasing fishing pressure. Further, fishing grounds with higher fishing visit rates had higher catches in general but lower catch per fishing visit. Larger and more productive rivers showed also higher catch. In contrast, intensity of fish stocking did not affect catches. In conclusion, perch populations in Central Europe are likely under high fishing pressure, and the pressure is further increasing.
... Many of the seminal papers providing production estimates for freshwater fishes have focused on perch, the most common and abundant fish species in European boreal lakes (Viljanen and Holopainen, 1982;Rask and Arvola, 1985;Ranta and Lindström, 1989), and a popular fish for human consumption and recreational fishing through Europe (Lyach and Remr, 2019). Horppila et al. (2010) suggested that the density of perch populations would be a better predictor of production capacity than the individual growth rate of fish. ...
... Minimum size limits are very rarely applied in real perch fisheries (e.g. Lyach and Remr, 2019), they are legally problematic for example in Finland, and they might induce strong density-dependence among fish smaller than the minimum size limit (or any technical recruitment size to fishing gear) and that rely mainly on invertebrate prey . Thus, boreal perch fisheries aiming to yield fish of value for human consumption could be scaled according to the 5 kg ha − 1 yr − 1 catch target as a first guess and as a basis for further lake quality based and empirical adjustments without strict minimum and maximum sizes for the landed fish beyond the avoidance of harvesting immature fish and recommendations to release the largest fish . ...
... Due to the efficient reproduction of perch that mature at very young age and small size in small boreal lakes compared to larger systems (Heibo et al., 2005;, these populations can tolerate high annual fishing mortalities such as 50% of the biomass . However, under heavy mortality the average size of captured perch could be less than 100 mm, i.e. very small compared to most perch fisheries (Lyach and Remr, 2019), and as such of very little importance for human consumption . Further, single-species MSY targets (such as the 9.4 kg ha − 1 yr − 1 estimate for perch) could induce significant ecosystem-level alterations with overall negative outcomes (Lee et al., 2021). ...
... Large-scale angling restrictions are among the most common and effective ways to protect fish populations from overexploitation by anglers and commercial fishermen. There are several types of restrictions: minimum and maximum angling size, a decreased amount of killed fish per day, catch-and-release fishing strategy, closed season, daily fishing hours, limited amount of fishing visits per week, permitted/forbidden fishing techniques (lures, baits, hooks, number of rods, nets, boats, lights), and no-fishing zones (Naslund et al., 2005(Naslund et al., , 2010Powell et al., 2010;van Poorten et al., 2013;Veiga et al., 2013;Tetzlaff et al., 2013;Lew and Larson, 2015;Lenker et al., 2016;Lenox et al., 2016;Rahel, 2016;Cha and Melstrom, 2018;Johnston et al., 2018;Lyach and Remr, 2019a, 2019b, 2019c. Angling restrictions may even change perceptions and behaviour of anglers (Beard et al., 2003). ...
... As previous studies have found, angling restrictions can potentially have either positive or negative effects on protected fish populations. For example, a restriction in minimum angling size can lead to increased fishing pressure on large-sized individuals which arein many fish specieshighly fertile females with high fitness (Arlinghaus et al., 2010;Lyach and Remr, 2019a, 2019b, 2019c. Conversely, other studies reported a recovery of fish populations after a restriction was introduced (Johnston, Arlinghaus et al., 2011;Alós and Arlinghaus, 2013;Askey, 2016). ...
... Fisheries Research 223 (2020) 105438 Fishing sites are defined as stream and river stretches where recreational fishing can be legally conducted. Aa similar dataset was previously used for scientific purposes (Humpl et al., 2009;Jankovský et al., 2011;Boukal et al., 2012;Lyach andČech, 2018a, 2018b;Lyach and Remr, 2019a, 2019b, 2019cLyach and Čech, 2019). ...
... Чешскими учеными опубликовано немало книг и статей (Lusk 1996, Vostradovský and Tichý, 1999, Pivnička a Rybář, 2001, Lusk et al., 2003, Draštík et al., 2004, Pivnička et al., 2005, Humpl et al., 2009, Jankovský et al., 2011, Boukal et al., 2012, Lyach and Čech, 2017a, 2017b, 2018a, 2018b, Lyach et al., 2018, Lyach and Remr 2019a, 2019b. Данный Закон регулирует следующие вопросы: ...
... Эти статистические данные используются для оптимизации управления рыболовством. В последнее время данные о вылове рыбы и интенсивности рыболовной ловли также использовались и в научных целях (Humpl et al., 2009, Jankovský et al., 2011, Boukal et al., 2012, Lyach and Čech 2017a, 2017b, 2018a, 2018b, Lyach and Remr, 2019a, 2019b. Преимуществом является наличие данных по каждому рыболовному угодию и по каждому году. ...
Настоящий документ является техническим документом, способствующим достижению региональных результатов в рамках проекта программы технического сотрудничества ФАО
(TCP/RER/3701) «Системы и методологии сбора данных о рыболовстве во внутренних водоемах Европы», финансируемого Региональным отделением ФАО для Европы и Центральной
Азии. Данная работа осуществляется при содействии Европейской консультативной комиссии по рыболовству во внутренних водоемах и аквакультуре (ЕККРАВВ), общеевропейской сетью
научно-исследовательских учреждений, а также посредством письма-соглашения между ФАО и Институтом природных ресурсов Финляндии (LUKE). Г-н Теппо Веханен (LUKE), председатель
научно-технического комитета ЕККРАВВ, осуществлял непосредственный надзор за работой соавторов из различных научно-исследовательских учреждений ЕККРАВВ. Технический надзор со стороны ФАО обеспечивали г-жа Виктория Чомо, секретарь ЕККРАВВ и старший специалист ФАО по рыболовству и аквакультуре, и г-жа Ева Ковач, консультант ФАО по вопросам
рыболовства во внутренних водоемах. Настоящий документ является значительным дополнением в знания о системах сбора данных о рыболовстве во внутренних водоемах в Европе, в нем
приводятся примеры передовых практик, выступающих в качестве руководства при формировании научно-обоснованных мер политики, а также описываются проблемы, возникающие в
процессе управления рыбными ресурсами во внутренних водоемах. Главной целью настоящего документа является подготовка актуализированного доклада о текущем состоянии систем
сбора данных об уловах и методологиях, применяемых рыболовными хозяйствами (промысловыми и рекреационными) на европейских реках и озерах. Представлены детальные примеры
систем сбора данных о рыболовстве во внутренних водоемах пяти стран с кратким обзором остальных европейских странах. В работе также участвовали и другие институты, которые отвечали за описание примеров своих стран: агентство по рыболовству во внутренних водоемах Ирландии («Inland Fisheries Ireland»), Загребский университет (Хорватия), Национальный
институт водных ресурсов (Дания) и Биологический центр Академии наук ЧР (Чешская Республика). Ценными и полезными были комментарии и предложения заинтересованных сторон,
которые способствовали повышению качества настоящего документа. Заключительная редакция была рассмотрена Научно-техническим комитетом ЕККРАВВ и утверждена Руководящим
комитетом ЕККРАВВ.
... • University of South Bohemia in České Budějovice, the Faculty of Fisheries and Water Protection. There are many books and articles published by Czech scientists (Lusk 1996, Vostradovský and Tichý, 1999, Pivnička a Rybář, 2001, Lusk et al., 2003, Draštík et al., 2004, Pivnička et al., 2005, Humpl et al., 2009, Jankovský et al., 2011, Boukal et al., 2012, Lyach and Čech, 2017a, 2017b, 2018a, 2018b, Lyach et al., 2018, Lyach and Remr 2019a, 2019b. Three studies assessed opinions and behaviour of anglers using online questionnaires (CAWI -computer assisted web interviews). ...
... This statistical data are used to optimize fisheries management. Recently, data on fish harvest and fishing effort have been used for scientific purposes as well (Humpl et al., 2009, Jankovský et al., 2011, Boukal et al., 2012, Lyach and Čech 2017a, 2017b, 2018a, 2018b, Lyach and Remr, 2019a, 2019b. The main strength is that data are available for each fishing ground and for each year. ...
This document is a technical paper contributing to the regional results under an FAO Technical Cooperation Programme project (TCP/RER/3701) on “Systems and methodologies of data collection in inland fisheries of Europe”, financed by the FAO Regional Office for Europe and Central Asia (REU). This work is facilitated by
the European Inland Fisheries and Aquaculture Advisory Commission (EIFAAC), a pan-European network of research institutions, and through a Letter of Agreement between FAO and the Natural Resources Institute Finland (LUKE). Mr Teppo Vehanen (LUKE), as Chair of the EIFAAC Technical and Scientific Committee (TSC), provided direct supervision of the co-authors from various EIFAAC research institutions. FAO
technical oversight was provided by Ms Victoria Chomo, Secretary of EIFAAC and Senior Fisheries and Aquaculture Officer of FAO and Ms Eva Kovacs, FAO Consultant on inland fisheries. This paper makes a significant contribution to knowledge on the inland fisheries data systems of Europe, providing examples of good practices to guide
evidence-based policy, as well as documenting the challenges facing management of inland fisheries resources. The main objective of this paper is to produce an up-to-date report on catch data collection and the methodologies used for fisheries (commercial and recreational) in European rivers and lakes. There are five detailed country examples of inland fisheries data collection systems and a short review of the remaining European countries. The other institutes involved, and responsible for their country examples, were Inland Fisheries Ireland, University of Zagreb (Croatia), DTU Aqua (Denmark) and Biologicke centrum AV CR (Czech Republic). The useful comments and suggestions from stakeholders were valuable and improved the quality of the paper. The final version was reviewed by the EIFAAC TSC and approved by the EIFAAC Management Committee.
... Der Europäische Flussbarsch ist einer der am weitesten verbreiteten und häufigsten Fischarten in vielen Binnen-und Brackgewässern Nord-und Mitteleuropas (Brucet et al., 2013). Seine Popularität als Angelfisch ist in vielen Ländern stark ausgeprägt (Arlinghaus & Mehner, 2004;Vainikka et al., 2012;Lyach & Remr, 2019;Czarkowski et al., 2021), sei es als wohlschmeckender Speisefisch oder basierend auf dem Reiz, sehr viele oder besonders große Exemplare zu fangen (Beardmore et al., 2011;2015 Tiere zutrifft (Beukema, 1970 (Nakayama et al., 2016) und in einer geringeren Futteraufnahme aufgrund langsamerer Verdauung der Nahrung resultiert (Persson, 1981). Jedoch wurden großwüchsige Individuen tendenziell besser mit der Angel gefangen ...
Anders als ihr Name vermuten mag, gehören Europäische Flussbarsche (Perca fluviatilis), im nachfolgenden Text Barsch genannt, zu den häufigsten Fischarten in Naturseen (Persson et al., 1991; Mehner et al., 2005) als auch in künstlichen Baggerseen (Matern et al., 2019; Matern et al., 2022). Innerhalb von Seen finden sich Barsche sowohl im Uferbereich als auch im Freiwasser (Nakayama et al., 2018), wobei nach einer ersten Phase im Freiwasser von Seen als Larve von Jungfischen insbesondere hölzerne Strukturen im Ufer von Gewässern bevorzugt werden (Lewin et al., 2004; Lewin et al., 2014). Adulte Barsche sind auch gerne im Freiwasser und vor allem am Übergang von Ufer zum Freiwasser an Scharkanten anzutreffen (Nakayama et al., 2018). In einer Untersuchung von insgesamt 20 niedersächsischen Baggerseen über vier Jahre (2016-2019) mittels Elektrofischerei vom Boot konnten Matern et al. (2021) zudem zeigen, dass die Häufigkeiten sowohl von kleinen als auch großen Barschen mit zunehmendem Deckungsgrad submerser Makrophyten (Unterwasserpflanzen) im Gewässer zunahmen. Für große Barsche war allerdings Totholz die wichtigste Struktur im Uferbereich, die sich positiv auf die Barschfänge auswirkte. In einer weiteren Studie zeigte Maday (2020) und Maday et al. (im Druck) in einer Unterstichprobe derselben Gewässer, dass von Anglern eingebrachte Totholzbündel intensiv von Barschen als Lebensraum genutzt werden. Dies war insbesondere am Tag während des Frühjahrs und im Winter der Fall.
... Where the species co-occur, there is also potential for dietary overlap and competition (Fobert et al., 2011), with SIA providing a tool that can investigate the extent of their trophic interactions (Copp et al., 2017). While destructive sampling for the collection of tissues for SIA may be permissible in the invasive range of these fishes, the species can have relatively high fishery values in their native ranges, especially European perch where catchand-release angling is increasingly practised (Czarkowski and Kapusta, 2019), especially as harvesting by angling can have strong deleterious effects on population abundances (Lyach and Remr, 2019). ...
Ecological studies on native and invasive populations of European perch Perca fluviatilis and pumpkinseed Lepomis gibbosus are often based on stable isotope (SI) analysis based on dorsal muscle, where samples are usually taken from sacrificed fishes. However, other tissues, such as scale and fin tissue, can be used as non-lethal alternatives, where their SI values can be standardised to dorsal muscle values for comparative purposes. In both perch and pumpkinseed, there was a pattern of δ¹³C enrichment and δ¹⁵N depletion from muscle to fin and scale. As comparative studies must account for these inter-tissue differences prior to analyses, conversion equations for SI data from scale and fin tissue to standardised muscle values are provided.
... Der Europäische Flussbarsch ist einer der am weitesten verbreiteten und häufigsten Fischarten in vielen Binnen-und Brackgewässern Nord-und Mitteleuropas (Brucet et al., 2013). Seine Popularität als Angelfisch ist in vielen Ländern stark ausgeprägt (Arlinghaus & Mehner, 2004;Vainikka et al., 2012;Lyach & Remr, 2019;Czarkowski et al., 2021), sei es als wohlschmeckender Speisefisch oder basierend auf dem Reiz, sehr viele oder besonders große Exemplare zu fangen (Beardmore et al., 2011;2015 Tiere zutrifft (Beukema, 1970 (Nakayama et al., 2016) und in einer geringeren Futteraufnahme aufgrund langsamerer Verdauung der Nahrung resultiert (Persson, 1981). Jedoch wurden großwüchsige Individuen tendenziell besser mit der Angel gefangen ...
... Studies of angling catch rates of perch have mostly been during the open-water season (Heermann et al., 2013;Monk & Arlinghaus, 2018;Skov et al., 2017), while studies of perch ice fishing have aimed to explain behavioural or size variation of fish captured (Härkönen et al., 2016;Kekäläinen et al., 2014;Vainikka et al., 2012). Vulnerability of individual perch to angling has been explained by environmental factors such as water transparency and availability of food resources, but also with fishing pressure (Heermann et al., 2013;Lyach & Remr, 2019;Monk & Arlinghaus, 2018). To improve the usefulness of CPUE data, effects of environmental variables on catchability must be understood (Kuparinen et al., 2010). ...
Management of inland recreational fisheries would benefit from stock abundance and size structure data. Feasibly standardised angling methods such as ice fishing could produce representative catch‐per‐unit‐effort (CPUE) information on the abundance of different‐sized fish in small lakes. Here, we first used standard Nordic multimesh gillnets to obtain number‐per‐unit‐effort (NPUE), biomass‐per‐unit‐effort (BPUE) and size structure data on Eurasian perch (Perca fluviatilis) stocks in 11 small boreal lakes in summer. Second, the same lakes were ice‐fished by voluntary anglers using a pre‐defined, loosely standardised protocol to obtain angling‐based NPUE, BPUE, and length frequency distributions. Effects of environmental variables such as water oxygen concentration and light penetration on angling catch rates were controlled statistically. Neither perch Nordic gillnet NPUE nor BPUE corresponded to ice‐fishing CPUEs. However, the length distribution of the catch did not differ between methods. Our results imply that traditional ice fishing applying natural baits is relatively unselective for fish size and could produce valid length‐based indicators for management purposes while angling CPUE was poorly related to Nordic gillnet CPUE.
... g. European perch (Lyach and Remr, 2019b). Since these native piscivorous fishes showed steep decline of yields, their conservation should be enhanced. ...
Introductions of non-native fishes are among the biggest threats to freshwater ecosystems globally. However, the effects of such introductions on fisheries management and fish yields are understudied. This study is trying to fill this knowledge gap by analyzing relationships between yields of native and non-native fishes with regards to important fisheries management factors, such as fish stocking, fishing effort, and the type or size of the fishery. I analyzed the changes in fish yields in the regions of Prague and central Bohemia from 1986 to 2017. Based on the 32 years of reported data that included 60 million harvested fish weighing 80 tons that were harvested by 250,000 anglers, I conclude that while predominately native fish species were harvested by anglers in the 1980, non-native fish species started dominating in the 21st century. This was true on both small trout streams (1-m wide) and medium-sized cyprinid rivers (5-250 m wide). This dominance is partially explained by the decreasing percentage of native salmonids and cyprinids and by the decreasing or stagnating percentage of native piscivores in the overall fish yield. Conversely, the percentage of non-native salmonids in the overall fish yield was increasing on both streams and rivers. Most importantly though, the percentage of non-native cyprinids-which made 60-80 % of all harvested fish-increased by 16 % over 32 years. Fish yield had a strong positive relationship with fish stocking intensity, a strong negative relationship with angling effort, and strong but mixed relationships with size of the fishery. In conclusion, native fishes are being slowly replaced by non-native fishes in the yield of recreational anglers in central Europe.
... In addition to the analysis of commercial catches, the catches of recreational fishers are also important. Lyach and Remr (2019) found that in 12 years (2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) catches of European perch Perca fluviatilis Linnaeus 1758 by angling in the Czech Republic declined by up to 60%. The Sava River is the longest Croatian river with the largest catchment area and is part of the Danube catchment area (Hrvatske vode, 2017). ...
The aim of this research is to analyse trends of anglers’ total catches of the most important fish species caught by angling in different parts of the Sava River Basin in Croatia (Cyprinus carpio, Silurus glanis, Esox lucius and Sander lucioperca). In all investigated counties, with the exception of Vukovar-Sirmium, common carp is the dominant fish species, usually present in significantly higher quantities compared to the other three species. Only in Vukovar-Sirmium county, northern pike is the dominant species caught. In most counties there are no dramatic changes in the catches of these four fish species, apart from the usual oscillations. Due to high fishing pressure and possibly inflow of polluted water from the Bosna River, Vukovar-Sirmium county is also particularly characterised by the trend of declining catches of all four species. The significant negative correlation between the average catch and the respective value of the coefficient of variation (CV) was also found for all data.
... European perch (Perca fluviatilis) is a popular fish species among anglers and it has a significant market demand in Europe (Craig, 2000;Järv et al., 2013;Couture & Pyle, 2015;Skov et al., 2017;Lyach & Remr, 2019). It can be characterized by slow growth, however it has an excellent meat quality. ...
European perch (Perca fluviatilis) is a native predatory fish in Hungary, and a promising new species of fresh water aquaculture nowadays. The European perch can be characterized by a high stress sensitivity during the intensive rearing, thus the optimization of environmental conditions has significant importance in the early life stages of fish. The aim of our study was to determine whether the light intensity and darkening of the water by humic acid affect the survival and growth performance of European perch juveniles. The experiment lasted for 28 days. Rectangular aquariums were arranged in 3 lines, the test environment consisted of 24 units. The experiment was set up with 10–10 fish per aquarium, total of 240 individuals. The average wet body weight of the fish at the start of the experiment was 1.69 grams. During the experiment, 6 treatments in 4 replicates were set up. In the first row, we set up 305.6±66.0 LUX (L), in the second row 118.0±24.4 LUX (C), and in the third row (D) 17.0±8.6 LUX illumination was set up. In each row the water of four aquariums were darkened by the addition of humic acid (H) (L, LH, C, CH, D, and DH). At the end of the experiment high survival rate was observed in all treatments. Examining the survival rate, the best results were found in the strongly illuminated treatments (L; LH- SR%=100±0.00). The observed mortality was caused by cannibalism. Regarding the individual body weight, the best results were shown by the treatments where the aquariums were illuminated with lower light intensity (C: 4.66±0.33 grams) and the aquarium water was darkened by humic acid (CH: 4.93±0.15 grams). The results of the C and CH groups were significantly better compared to the other treatments, however, they did not differ statistically from each other. The darkening of the water had a positive effect on the individual body weight of fish reared under full light (L: 3.73±0.28 grams; LH: 4.33±0.28 grams), whereas in the case of fish reared in the lowest illumination, the addition of humic acid did not affect the results (D: 3.78±0.15 grams; DH: 3.80±0.26 grams). In case of SGR (C: 3.64%/day and CH: 3.74%/day) and FCR (C: 0.84 g/g and CH: 0.78g/g) the best results were obtained by the C and CH treatments, also.
... The significance of using the European perch as bioindicator in environmental studies lies in its: (1) trophic position e opportunistic predator (Kottelat and Freyhof, 2007); (2) abundance e a very common species in almost all reservoirs in Serbia; (3) nutritional characteristics e a low fat content in its meat (J€ arv et al., 2013); and (4) importance in commercial and sport fishing (J€ arv et al., 2013;Lyach and Remr, 2019;Skov et al., 2017). ...
This study was conducted on individuals of European perch from six reservoirs in Serbia with different properties, used for different purposes, and situated at different altitudes. Samples of muscle, gills, and liver, as well as water samples, were used for analysis of elemental accumulation. Histopathological (HP) analysis of gills and liver, and Fulton's condition factor (CF) were used as biomarkers. Analysis of Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn was conducted by inductively-coupled plasma optical emission spectrometry (ICP-OES), and accordingly, metal pollution index and bioaccumulation factor (BAF) were calculated. Elemental accumulation varied considerably both among tissues and reservoirs. Reservoirs located on large low-altitude rivers were the most heavily polluted with metals (Međuvršje, on the Zapadna Morava River, and Lake Sava, on the Sava River). Of three tissues analyzed, the gills were most affected by pollution. The levels of Hg in muscle decreased with an increase in reservoir altitude. Specimens sampled from the highest altitude reservoir were the least affected by HP alterations; however, HP differences between the reservoirs were not statistically significant, and the severity of HP changes was generally low. No significant correlations between the elemental accumulation or HP indices with CF were observed.
... Because of a low fat content in its muscle tissue (about 1%), the European perch is highly demanded as a diet food on markets (J€ arv et al., 2013). It is an important commercial fish species, also attractive for sport fishing (J€ arv et al., 2013;Skov et al., 2017;Lyach and Remr, 2019), which is a common practice in almost all reservoirs in Serbia. Since there is no close season on this species, it can be fished throughout the year (Official Gazzette of RS, 2015). ...
Concentrations of As, Cd, Cr, Cu, Hg, Pb, and Zn in sediment samples and muscle tissue of the European perch were analyzed using inductively-coupled plasma optical emission spectrometry (ICP-OES), with the aim to assess the potential ecological (RI) and human health risk, and the degree of contamination (Cd) of three types of reservoirs in Serbia, based on their purpose: electricity generation (Vlasina, Perućac, Zaovine, and Međuvršje), drinking water supply (Garaši), and recreation (Lake Sava). The concentrations of the studied elements were higher in sediments than in fish. However, the levels of Cd in fish caught in Vlasina, Zaovine, and Međuvršje, Hg in Perućac and Garaši, and Pb in Lake Sava exceeded the maximum allowed concentrations. The pollution load index (PLI) indicated that sediments in all six reservoirs were contaminated, but Cd was low; a moderate contamination with Cd was observed in Vlasina, Perućac, and Zaovine, Cr in Zaovine and Međuvršje, and Cu in Međuvršje. A low RI was recorded for all studied reservoirs. Cd was found to be the primary contamination and ecological risk factor. Total target hazard quotient (THQ) and target carcinogenic risk factor (TR) were higher for fishers operating in these reservoirs than for the general population. Higher values of PLI, Cd, RI, and TR were observed in electricity generation reservoirs. Results indicated that this type of reservoirs suffer from higher anthropogenic pressure and/or have a worse pollution management policy compared with other types of reservoirs included in this study, especially the drinking water supply reservoir.
Perca fluviatilis (the European perch) is one of the most common and well-studied freshwater fishes in the world, largely owing to its widespread distribution and popularity among anglers and aquaculturalists. It has been especially well-studied in its native ranges of Eurasia, but has received far less attention elsewhere. Here we review key aspects of the general biology and ecology of the European perch, by considering learnings from countries where it is native in addition to those where it has been introduced. Our review demonstrates that the European perch is a highly fecund, trophic generalist that can live in a wide range of habitats and withstand a wide range of physico-chemical conditions. The growth rates and sexual development of the European perch vary among geographical regions, largely due to differences in climatic conditions, with populations in warmer Southern Hemisphere regions tending to exhibit faster growth rates and attain sexual maturity at younger ages than populations occurring in most cooler Eurasian regions. Genetic differentiation has also been observed in native populations from different parts of Europe, although it remains unclear as to whether native and non-native populations differ genetically, and what the ecological implications of any such differences are. Future research should prioritise assessing both genetic and phenotypic differences between native and non-native populations, and determining the ecological implications of these differences. Such knowledge is crucial for informing European perch conservation and/or aquaculture management in countries where it is native; and invasive species management in countries where it has been introduced.
Inland recreational fisheries, found in lakes, rivers, and other landlocked waters, are important to livelihoods, nutrition, leisure, and other societal ecosystem services worldwide. Although recreationally-caught fish are frequently harvested and consumed by fishers, their contribution to food and nutrition has not been adequately quantified due to lack of data, poor monitoring, and under-reporting, especially in developing countries. Beyond limited global harvest estimates, few have explored species-specific harvest patterns, although this variability has implications for fisheries management and food security. Given the continued growth of the recreational fishery sector, understanding inland recreational fish harvest and consumption rates represents a critical knowledge gap. Based on a comprehensive literature search and expert knowledge review, we quantified multiple aspects of global inland recreational fisheries for 81 countries spanning ~192 species. For each country, we assembled recreational fishing participation rate and estimated species-specific harvest and consumption rate. This dataset provides a foundation for future assessments, including understanding nutritional and economic contributions of inland recreational fisheries.
Research presented in the preceding chapters emphasizes recent advancements in the research, management, and aquaculture of Walleye, Sauger, and Yellow Perch in North America. These percid fishes, along with the European Perch and Pikeperch, are economically and ecologically important fishes in their native geographic range. Advances in techniques to evaluate current habitat and predict future habitat conditions provide managers with detailed baseline information and biophysical models useful for evaluating adaptive management practices. Current habitat use and movement assessments have improved substantially with technological advancements in acoustic tags and extensive receiver array networks, which, combined with genetic and genomic tools, are improving percid stock assessments and management. Advances in percid aquaculture techniques have improved growth, survival, and disease resistance, enhancing percid stocking efforts and the production of marketable fish. The exchange of information between researchers and managers will continue to advance techniques of percid management for commercial and recreational exploitation and improve aquaculture practices to provide a lucrative commercial aquaculture industry.
To understand the determinants of angling vulnerability arising from the interplay of fish and angler behaviour, we tracked 33 large Eurasian perch, Perca fluviatilis, with fine-scale acoustic telemetry at a whole-lake scale while simultaneously tracking boats of small groups of experimental anglers (n = 104) who varied by self-reported skill. We report two key findings. First, perch vulnerability was strongly related to a repeatable habitat choice behaviour, but unrelated to swimming activity as a personality trait; importantly, highly vulnerable perch were captured throughout the lake and not only in their preferred habitat, suggesting covariance between spatial habitat choice and a behavioural determinant of vulnerability. Second, catch per unit effort of large perch increased with self-reported angling skill, an effect unrelated to skill-dependent lure use or an angler’s ability to encounter perch. Importantly, high-skill anglers captured more fish but not different spatial behavioural phenotypes. Our study has implications for designing protected areas by showcasing that angling could systematically alter the habitat use of exploited populations at whole-ecosystem scales, without necessarily changing average swimming activity and home range extension.
The question was whether a canyon-shaped reservoir is inhabited by genetically distinct populations of European perch Perca fluviatilis exhibiting different spatial behaviour, or by a single population. The study was conducted in the spring of 2006 at Římov Reservoir, Czech Republic. Epipelagic and bathypelagic perch fry (EPF and BPF) were captured by trawl net (mesh size 1 × 1.35 mm) controlled by echo sounder, and littoral perch fry and adults (LPF and LPA) were caught by electrofishing and beach seine (mesh size 1 × 1.35 mm). DNA was isolated in 266 individuals from the reservoir, and phylogenetic analysis based on mtDNA was performed (n = 18) on BPF, EPF, LPF, and LPA from the reservoir and additional sequences from Central Europe. Six microsatellites were used for differentiating among communities (n = 266). There was no evidence for genetic divergence in mtDNA sequences. Analyses of microsatellites revealed no statistically significant variations between spatial communities, and confirmed genetic homogeneity among communities. FST values and the number of genetic clusters point to the same conclusion, i.e., the reservoir is inhabited by a single population whose individuals occupy different microhabitats.
The effects of two hook-types (circle or J hook) fished with two different baits (red worms Eisenia spp., or cyprinid fishes) were examined for deep-hooking, catch rate, mean total length, and selectivity of Eurasian perch, Perca fluviatilis, in the Åland Archipelago, Finland. The perch population available to hook-and-line gear was sampled with multipanel gillnets, with panels ranging from 10 to 60 mm in stretched mesh diameter. The effect of each hook then was examined for each bait by conditioning the size distributions of hook-and-line catches on the size distribution of perch collected with gillnets to estimate selectivity. The proportion of deeply-hooked perch was 4.8 times greater for J hooks (0.21) than circle hooks (0.04) baited with worms and 3.7 times greater for J hooks (0.33) than circle hooks (0.09) baited with fish. Catch rates were significantly different between the two baits but not between the two hooks, with the greatest catch rate observed for the circle hook baited with worms. There was no significant difference in perch total length between the two hooks, but there was a significant difference between the two baits, with the fish bait catching significantly larger perch. Perch selection peaks between the two hooks differed by only 13.8 mm, but the selection peak with fish bait (236.4 mm TL) was 119.9 mm greater than the selection peak with the worm bait (116.5 mm TL). A substantially lesser incidence of deep hooking support the conservation benefits of circle hook use for perch, especially when catch-and-release is practiced. Using fish baits similar in size to those used in this experiment can avoid potentially harmful interactions between relatively small perch and anglers who place little importance on catch motives but whose satisfaction is still catch-dependent.
Recreational fishing is an established activity in developed countries across the world. Many emerging economies also have well-established recreational fisheries; however, in countries such as India there has been little discourse on what is needed to support this activity’s sustainable development. Here, we review the history of recreational fishing and the current status of recreational fisheries in India. The lack of scientific knowledge on the basic biology of sport fish species,targeting of threatened species, and the absence of region- or species-specific angling regulations for recreational fisheries are identified as some of the challenges associated with this sector in India. Moreover, governance structures are disorganized, with multiple agencies assuming some responsibility for recreational fishing but none tasked explicitly with
its sustainable development and management. With improved legislative support and a clear policy framework, developing a responsible and sustainable recreational fisheries industry in India is possible.
Mechanisms resulting in hyperstability (where catch per unit effort (CPUE) remains high as fish density declines) in recreational fisheries are poorly understood owing to a lack of experimental data. We collected data on angler CPUE and fish density to determine whether hyperstability exists in the rainbow trout (Onchorhynchus mykiss) lake fishery of British Columbia. We contrasted the relationship between CPUE and fish density in an open-access recreational fishery with an experimental fishery (a set of lakes that had restricted access, standardized fishing methods, and no heterogeneity in angler experience) to assess the mechanistic cause of hyperstability. We detected no evidence of hyperstability in the experimental fishery, but significant hyperstability in the open-access fishery. In the open-access fishery, the composition of the angler population varied among lakes: anglers who fished at low-density lakes were more experienced than anglers fishing at high-density lakes. This segregation of angler experience across lakes appeared to explain the observed hyperstability in this fishery. Our results provide a mechanistic understanding of hyperstability in an open-access recreational fishery and suggest that CPUE data be used in conjunction with data on angler experience when assessing the status of a fishery.
This article presents a general overview of recreational
fisheries in Brazil, with emphasis on inland fisheries;
reports their current needs; and provides directions for future
work considering that there is an apparent increase in recreational
fishing in emerging economies around the globe. Even
though there is no nationwide survey to identify the profile of
all Brazilian recreational fishers, some insights can be obtained
from competitive fishing events and from the questionnaire
printed on the back of fishing licenses. The number of fishing
licenses issued in 2010 was approximately 220,000, representing
an increase of 220% compared to 2000. Some estimates
suggest that the number of recreational fishers in Brazil may
be around 10 million. Information on fishing expenses, catchand-
release activities, fishing guides, lodging, fishing areas,
target species, management control, and fishing clubs and associations
is presented. Data for basic estimates such as total
number of recreational fishers, total catch and species composition,
and total economic value are unavailable, but the results
presented here are nevertheless essential for a long-term planning
of the development of recreational fishing in Brazil. Other
requirements are presented and suggestions are made toward
improved management of recreational fisheries in Brazil and
other emerging economies.
Recreational fishermen derive utility from catch and fishing effort. Building our analysis on the Gordon-Clark model for renewable resources, we show that a lower importance of catch may result in higher catches. While this effect also holds under first-best management, it may destabilize open-access recreational fisheries to the point of stock collapse. Technical progress in recreational fisheries may mask such dynamics as it enables unaltered angler behavior and constant catches during stock declines.
In the early 1990s, commercial and recreational fishermen in the Kalmar Sound of the Baltic Sea reported decreasing stocks of Eurasian perch (Perca fluviatilis) and northern pike (Esox lucius). Test fishing surveys confirmed regionally declining abundances of both species. Both pike and perch spawning were observed annually, but virtually no young-of-the-year were captured in surveys from 1997-1999. The rapid decrease of the stocks was probably a result of the widespread recruitment failure. Studies of potential causes of the recruitment failure were conducted in 1998-2000. Field experiments excluded suboptimal water quality in brackish water recruitment areas as regulatory factor. Laboratory tests did not indicate reproductive disturbances in parental fish that could be related to chronic toxicity or endocrine disruptions, as hatching success and yolk-sac larvae survival were not negatively affected. Exposure to filamentous algae (Pilayella sp.) and diatoms, common in the spawning areas, had only a slight negative effect on pike egg hatchability. Two hypotheses that could not be rejected are food deficiency during the post hatching period and egg predation.
CapsuleOf 26 species of wintering waterbirds, 18 showed an increase in numbers, five showed a decrease and two showed no change. AimTo assess long-term trends in the numbers and distribution of the 26 most abundant wintering waterbird species in the Czech Republic. Methods
We used International Waterbird Census data from between 48 and 639 wetland sites which had been counted annually in the Czech Republic from 1966 to 2008. From these data long-term changes in numbers and distributions were determined. Log-linear Poisson regression analysis was used to estimate missing data using trim software. The distribution of each species was described as the ratio of the number of sites occupied by that species to the total number of sites investigated. ResultsIncreasing trends were found for 18 species, five species were found to be declining, one species was stable and two species were found with uncertain trends. Wintering distributions (the ratio of sites occupied by a given species to the total number of sites counted) increased in 16 species and decreased in two species, broadly correlated with the species changes in numbers. Conclusion
In most species changes in numbers as well as changes in distribution followed the Western Palearctic population trends. Those species which increased were mainly piscivores and included geese, ducks and gulls. Scarcer species also exhibited an increase in numbers. The changes in numbers (both positive and negative) were more frequent among species associated with running water, whereas species which showed uncertain trends were more frequently recorded on standing water, which is more affected by variable weather conditions.
Exploitation of fishery resources has become a major conservation issue on a global scale. Commercial fisheries have been
repeatedly blamed for the worldwide declines in fish populations. However, we contend that the recreational fishing sector
also has the potential to negatively affect fish and fisheries. Here we present evidence to show that both recreational and
commercial fishing sectors deserve consideration as contributors to the exploitation of fish in marine and inland waters.
The lack of global monitoring and compiling of statistics on recreational fishing participation, harvest, and catch-and-release
has retarded our ability to understand the magnitude of this fishing sector. Using data from Canada, we estimate that the
potential contribution of recreational fish harvest around the world may represent approximately 12 percent of the global
fish harvest. Failure to recognize the potential contribution of recreational fishing to fishery declines, environmental degradation,
and ecosystem alterations places ecologically and economically important resources at risk. Elevating recreational fishing
to a global conservation concern would facilitate the development of strategies to increase the sustainability of this activity.
The change in catches and mean size of one-year-old perch (Perca fluviatilis) in Lake Geneva was studied between 1957 and 2005, and related to trophic changes and
average temperature. The status of Lake Geneva, assessed on the basis of total phosphorus concentrations, switched from being oligotrophic before 1960 to eutrophic, with total phosphorus concentration reaching nearly 90 µg L−1 in 1976-1979. In response to management measures, the
trophic status then returned to mesotrophy in the early 2000s. Zooplankton
is the main food consumed by young perch, and quantities present (annual
biovolumes of zooplankton) were recorded throughout the study period. The
lake water temperature was also recorded. Data obtained from perch catches
and perch spawns enabled eleven strong cohorts of perch to be identified.
Strong cohorts dominated the stock for three years, until they were
massively caught by fishermen. Yields have fluctuated widely, increasing
rapidly until 1975, and subsequently decreasing, with an exceptional decline
between 1976 and 1981. During the period 1977-1981, unfavourable climatic
conditions in spring were probably the main cause of this fall in perch
yields. For the other periods, perch yields and the mean size of
one-year-old perch were significantly correlated with trophic parameters,
total phosphorus concentration and zooplankton biovolume. Correlations are
higher if only strong cohorts are taken into account. As a result of the
re-oligotrophication process, perch growth has been progressively reduced,
age at first maturity delayed and strong cohorts become less frequent; the
mean size of 0+ individuals in strong cohorts is significantly smaller than
in the other cohorts, suggesting a population density effect in the context
of a limited supply of zooplankton. During the study period, trophic changes
in Lake Geneva have had more impact on perch growth and yield than has
temperature, since no significant correlation could be detected between
water temperature and perch growth.
Résumé
Entre 1960 et 2005, l'évolution des captures totales et celle de la
taille moyenne des perches (Perca fluviatilis) âgées d'un an du lac Léman ont
été étudiées en relation avec l'évolution trophique et
la température moyenne du milieu. Le statut trophique du lac, estimé
à partir des concentrations en phosphore total, a évolué de
l'oligotrophie avant 1960 jusqu'à l'eutrophie, le phosphore total
atteignant près de 90 µg L−1 en 1976-1979. Suite aux mesures
d'assainissement, le lac est redevenu mésotrophe dès 2001. Les
quantités de zooplancton, principale nourriture des jeunes perches, ont
été mesurées (biovolume annuel de zooplancton). La
température a également été mesurée. En se basant sur
les analyses faites sur les captures et sur les études menées lors
de la reproduction, onze fortes cohortes de perches ont été
identifiées. D'une manière générale, les fortes cohortes
constituent l'essentiel du stock de perches pendant trois ans, jusqu'à
ce que les pêcheurs les aient décimées. Les captures
présentent d'importantes variations inter-annuelles ; les quantités
pêchées ont augmenté rapidement jusqu'en 1975 et diminuent
depuis, avec une chute exceptionnelle entre 1976 et 1982. De 1977 à
1981, une succession de mauvaises conditions climatiques printanières
explique probablement cette chute des captures. Pour les autres
périodes, les quantités de perches capturées et la taille
moyenne des perches à 1 an sont corrélées aux paramètres
trophiques (concentration en phosphore total et biovolume de zooplancton).
Les corrélations sont plus élevées si seules les fortes cohortes
sont prises en compte. Avec le processus de ré-oligotrophisation, la
croissance des perches diminue, l'âge de la maturité sexuelle est
retardé et les fortes cohortes sont plus espacées ; la taille
moyenne des individus 0+ des fortes cohortes est significativement plus petite que celle des autres cohortes, traduisant un effet marqué de densité-dépendance vis-à-vis de la ressource limitée de zooplancton. Durant la période étudiée, les changements trophiques du lac Léman ont eu un effet plus marqué que la température sur la croissance et les captures de perches, puisque aucune corrélation positive n'a pu être mise en évidence entre la température de l'eau et la croissance ou les rendements de la pêche des
perches.
Abstract Recreational fisheries statistics can provide valuable information on the dynamics of fish stocks and their exploitation. For some reservoirs in the Czech Republic, there are conspicuous synchronous fluctuations in catches of different species that might be caused by fishing skills and strategies. This study describes a method that could detect signatures of such phenomena in individual logbooks. It classifies anglers by species reported during 1 year and compares the resulting angler groups by group size, fishing effort, catch per unit effort (CPUE) and annual catch. The method is illustrated by data from one reservoir, showing that the number of generalist anglers who caught several species was higher than expected. Generalists also had higher catches and effort but lower CPUE than specialists who caught only one of the species. The results indicate that generalist anglers with a low degree of specialisation and high effort could contribute to long-term correlations in species catches.
We evaluated the commercial and recreational fishery landings over the past 22 years, first at the national level, then for
populations of concern (those that are overfished or experiencing overfishing), and finally by region. Recreational landings
in 2002 account for 4% of total marine fish landed in the United States. With large industrial fisheries excluded (e.g., menhaden
and pollock), the recreational component rises to 10%. Among populations of concern, recreational landings in 2002 account
for 23% of the total nationwide, rising to 38% in the South Atlantic and 64% in the Gulf of Mexico. Moreover, it affects many
of the most-valued overfished species—including red drum, bocaccio, and red snapper—all of which are taken primarily in the
recreational fishery.
Research by Berkeley et al. and by Bobko and Berkeley has recently demonstrated that older individuals of some fish species produce larvae that have substantially better survival potential than do larvae from younger fishes. These new findings augment established knowledge that larger individuals usually have exponentially greater fecundity. This is important because commercial fisheries and especially recreational fishing often target the larger fish. The protection of larger or older individuals is necessary for the sustainability of species currently exploited by humans.
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.
Recreational fishing is a major leisure activity in many European countries but social aspects of angling are still understudied. This study aimed to examine long-term social trends in recreational fishing. Data was obtained from annual angling reports collected by the Czech Fishing Union. Data from annual angling reports is based on data from individual angling logbooks collected from 238 fishing grounds over the course of 11 years in Prague and Central Bohemia, Czech Republic. It was discovered that the numbers of individual anglers and angling visits on fishing grounds have been increasing. An average angler visits higher diversity of fishing grounds but anglers keep on returning to individual fishing grounds less frequently. Frequency of angling guard controls on fishing grounds has been increasing as well. On the other hand, angling yield and catch have been decreasing. The number of anglers who take home at least one fish has been increasing but percentage of anglers who take home at least one fish has been decreasing. In conclusion, recreational fishing is on the rise but fish catch and yield are decreasing.
Standardised angler diaries could produce useful proxy data for assessing fish population density and size distribution, but few rigorous studies about their utility exist. We use 62 years of angling diary data (1949–2010), from a large mesotrophic lake, to investigate population structure (abundance, mean size and record size) of European perch (Perca fluviatilis L.) in relation to the impact of three commercial fishers with different fishing strategies, pike (Esox lucius L.) predation and temperature. We found that anglers’ harvest rates of perch varied by a factor of 10 over time, indicating large variation in population abundance over decadal time scales. Our statistical analysis revealed that the anglers’ harvest rates of perch were related to pike CPUE (proxy of pike predation), temperature and commercial fishing directly through the harvest of perch and indirectly through the harvest of pike, the top predator of the lake. The size distribution and growth rates of perch caught by anglers also changed substantially during the study period, most likely controlled by density-dependent mechanisms as well as size-selective commercial harvest. The effect of selective harvest on size-structure was stronger than ecological density dependence. We conclude that commercial harvesting may exert strong impacts on the quality of the angling experiences, at least in the studied case. Moreover, our work showcases the value of detailed angler diaries to study and monitor changes in freshwater fish populations, but it also underlines the need for supplementary data on biotic and abiotic factors to reach the full potential of angler diary data.
Stocking of hatchery-reared fish into streams is a common practice in fisheries industry as it provides catches for recreational anglers and support for native fish populations. The Eurasian otter Lutra lutra is one of the most important freshwater piscivorous predators in Europe. Impact of otters on stocked fish is a source of conflict between fisheries industry and environmental protection. This study aimed to describe differences between otter diet and catches of anglers on a lowland trout stream with salmonid stocking. Otter diet was studied during winter, using spraint analysis. Fish dominated otter diet (85% of biomass). Gudgeon Gobio gobio was the most important otter prey (38% of biomass). Catches of otters and catches of anglers on the stream were significantly different. Otters mostly preyed upon small-growing fish species of medium or no angling value while anglers took large-growing fish species of medium and high angling value. Otters took fish with average weight of 10 g while anglers took fish with average weight of 290 g. Stocked salmonids made up 13% of estimated biomass in otter diet. Otters targeted significantly different fish species of different sizes than anglers did.
Population increase of piscivorous cormorants in Europe and in North America has created a conflict between fisheries and the species. The impact of cormorants on natural fish populations and yields of fishermen is still under debate. We investigated potential connection of the great cormorant Phalacrocorax carbo abundance, fishing effort and water temperature with the economically important perch Perca fluviatilis and pikeperch Sander lucioperca yields, measured as catches per unit of effort (CPUE) in gillnet fishing along the Finnish coastal areas (Baltic Sea) using 50 km International Council for the Exploration of the Sea (ICES) grids. Since cormorants generally take smaller prey than fishermen, we expected 2–5 years time lag effect of the cormorant numbers on CPUE. Correspondingly, we expected 4–7 years lag effect of temperature on CPUE. Despite the population increase of cormorants, CPUE of perch increased in 10 out of 29 ICES grids during the study period 2005–2014. Pikeperch CPUE increased in five out of 24 grids and decreased in one. There was significant annual variation in CPUE values of perch and pikeperch, but values were not significantly associated with changes in cormorant numbers and temperature either annually or long-term. However, the CPUE values of pikeperch decreased towards the north, which is likely temperature driven as northern colder waters are less suitable for this species than southern waters. There was no clear evidence that either predation by cormorants or fishing effort are associated with long-term trends of perch and pikeperch stocks on a larger scale along the Finnish coast. The increasing CPUE values in several areas indicate that stocks are more abundant than ten years ago despite an increasing cormorant population. Our study approach can be used to monitor potential changes in stocks and impacts of cormorant in the future.
Measuring the proportion of variance explained () by a statistical model and the relative importance of specific predictors (semi-partial ) can be essential considerations when building a parsimonious statistical model. The statistic is a familiar summary of goodness-of-fit for normal linear models and has been extended in various ways to more general models. In particular, the generalized linear mixed model (GLMM) extends the normal linear model and is used to analyze correlated (hierarchical), non-normal data structures. Although various statistics have been proposed, there is no consensus in statistical literature for the most sensible definition of in this context. This research aims to build upon existing knowledge and definitions of and to concisely define the statistic for the GLMM. Here, we derive a model and semi-partial statistic for fixed (population) effects in the GLMM by utilizing the penalized quasi-likelihood estimation method based on linearization. We show that our proposed statistic generalizes the widely used marginal statistic introduced by Nakagawa and Schielzeth, demonstrate our statistics capability in model selection, show the utility of semi-partial statistics in longitudinal data analysis, and provide software that computes the proposed statistic along with semi-partial for individual fixed effects. The software provided is adapted for both SAS and R programming languages.
The fish communities of 84 Central and Eastern European reservoirs were sub-divided according to their species compositions into six fish faunal types that are identical with the successional stages of reservoir ichthyocenoses. The six types are:
(1)
Briefly existing fish faunas in which riverine species (especially salmonids) predominate. Found in 4% of reservoirs.
(2)
Faunas characteristic of the reservoir initial filling period and with extraordinarily high (15–70%) percentage occurrence of northern pike. Found in 6% of reservoirs.
(3)
Faunas in which perch (Perca fluviatilis) is predominant usually with one particular year class strongly represented (a ‘cycling’ population). Found in 9% of reservoirs.
(4)
A transient fish fauna which is dominated by perch plus cyprinid fish. Found in 8% of reservoirs, with 20–50% of the fauna being perch and the rest represented by the predominant cyprinid species of type 5.
(5)
A fauna dominated by cyprinids, usually by Rutilus rutilus, Abramis brama and/or Blicca bjoerkna together with a non-cycling perch population of less than 20%. This faunal type is the most frequently occurring one in Central and Eastern European reservoirs (61% of cases).
(6)
The remaining reservoirs (12%) contain fish faunas that are dominated by coregonids or Clupeonella or Carassius or Ctenopharyngodon or Hypophthalmichthys or Aristichthys or Cyprinus carpio or Pelecus cultratus.
The characteristics and validity of these fish faunal types are discussed.
Animal personalities, i.e. consistent individual differences in behaviour, are currently of high interest among behavioural and evolutionary biologists. The topic has received increasing attention also in fisheries science because selective harvesting of certain behavioural types might impose fishing-induced selection on personality. Here, we ice-fished wild Eurasian perch (Perca fluviatilis) from three native populations and investigated whether differences in relative catchability would explain behavioural differences observed in experimental conditions. We inferred relative catchability differences indirectly by fishing each location first with generally inefficient artificial bait and then by more efficient natural bait. The captured, individually tagged fish were tested in groups for their exploration tendency, activity and boldness under authentic predation risk in semi-natural stream channels. Fish that were easily captured first with artificial bait expressed fast exploration and acute activity, whereas the fish captured with natural bait showed less active and explorative behaviour. Differences in relative catchability did not explain variation in boldness or body size. In conclusion, we found that (1) Eurasian perch differing in relative catchability differ in certain behavioural traits, (2) fast explorers are more common among fish that get easily caught compared to fish that are more difficult to catch, (3) relative catchability explains more behavioural variation in a novel environment than in a familiar one and (4) selectivity of recreational angling on fish behaviour may depend on applied angling method and the effort spent on each location.
We investigated cormorant diet in the Archipelago Sea, Southwest coast of Finland. Samples of cormorant pellets, regurgitates and stomachs were collected in 2010–2011. During these years, pikeperch and perch were found to make up 0.04–10% and 21–43% of the diet respectively, by mass. The length distribution of perch eaten by cormorants was more similar to the length distribution in purse seine samples rather than to that in commercial catches. The size structure of pikeperch in the cormorants’ diet was intermediate between those in purse seine samples and commercial catches. Combined commercial and recreational catches have varied between 500–2000 t for perch and 225–525 t for pikeperch in the 2000’s. Potential yield losses to fisheries caused by cormorant feeding in 2010 were 340–420 t for perch and 110–140 t for pikeperch, thus cormorant predation may affect catches and the profitability of fishing.
To predict recreational-fishing impacts on freshwater fish species, it is important to understand the interplay between fish populations, anglers and management actions. We use an integrated bioeconomic model to study the importance of fish life-history type (LHT) for determining (i) vulnerability to over-exploitation by diverse angler types (generic, consumptive and trophy anglers), who respond dynamically to fishing-quality changes; (ii) regulations [i.e., minimum-size limits (MSLs) and licence densities] that maximize the social welfare of angler populations; and (iii) biological and social conditions resulting under such socially optimal regu-lations. We examine five prototypical freshwater species: European perch (Perca flu-viatilis), brown trout (Salmo trutta), pikeperch (Sander lucioperca), pike (Esox lucius) and bull trout (Salvelinus confluentus). We find that LHT is important for determining the vulnerability of fish populations to overfishing, with pike, pikeperch, and bull trout being more vulnerable than perch and brown trout. Angler type influences the magnitude of fishing impacts, because of differences in fishing practices and angler-type-specific effects of LHT on angling effort. Our results indicate that angler types are systematically attracted to particular LHTs. Socially optimal minimum-size limits generally increase with LHT vulnerability, whereas optimal licence densities are similar across LHTs. Yet, both regulations vary among angler types. Despite this variation, we find that biological sustainability occurs under socially optimal regula-tions, with one exception. Our results highlight the importance of jointly consider-ing fish diversity, angler diversity and regulations when predicting sustainable management strategies for recreational fisheries. Failure to do so could result in socially suboptimal management and/or fishery collapse.
In culture-based fisheries, managers strive for high stocking efficiency, the ratio between the total weight of caught and stocked fish. Here we present a new time series approach to examine the dependence of reported anglers’ catches on stocking and external events, using data on carp (Cyprinus carpio L.) from 14 reservoirs in the Czech Republic. Average stocking efficiency varied between 0.25 and 2.2, with values close to unity in most reservoirs. The lowest efficiencies occurred in three reservoirs receiving cold hypoxic water from a large upstream reservoir, while the highest efficiencies were found in two shallow, highly productive reservoirs. Analyses further indicate that stocked carp are typically caught during the year of release or the year after; but also that the mean time lag between stocking and capture increases with reservoir area. External events can be important: major floods in the years 2002 and 2006 were in many cases followed by large, up to 10-fold, increases in catches in subsequent years; we attribute the surplus catch to carp washed down from upstream aquaculture and river stretches. In contrast, the “Velvet Revolution” (demise of the communist regime in 1989) had no discernible effect on catches in subsequent years. In conclusion, the proposed method can simultaneously estimate the likely mean survival time of stocked carp and identify the impact of major environmental and societal events on recreational fisheries. The approach thus sheds light on the performance of current stocking practices at individual reservoirs, and could be used to monitor and improve stocking strategies and management of culture-based recreational fisheries.
Recreational freshwater fisheries are key components of local economies in many regions. The quality of these fisheries can be affected not only by harvest but also by catch‐and‐release practices. Documenting catch and release among sport fish taxa is, therefore, important to fisheries researchers studying sport fishes and managers regulating these fisheries. We used an angler diary survey to assess taxon‐specific effort, catch, harvest, release, and reason for release during the 2011 open‐water season. Our study included information on 5,007 fishing trips taken by 652 anglers. These anglers visited 279 lakes spanning 11,761.5 km ² of northern Wisconsin. Muskellunge Esox masquinongy , black bass (i.e., Smallmouth Bass Micropterus dolomieu and Largemouth Bass M. salmoides ), Northern Pike E. lucius , Walleye Sander vitreus , and panfish were released at rates of 99, 97, 86, 67, and 67%, respectively, when targeted by anglers. This study is the first to document black bass catch‐and‐release rates in the region and corroborates previous findings of Muskellunge and Walleye catch‐and‐release rates based on creel surveys. Voluntary catch and release was the most common reason for release. Our findings suggest that regulations may be much more generous than the harvest rates practiced by anglers and that catch‐and‐release angling practices may be an important factor affecting these sport fish populations.
Received July 18, 2012; accepted March 12, 2013
We implemented a statewide volunteer angler diary program for the 1995 fishing season to determine whether angler diaries can provide data that are useful for the management of the principal sport fishes in waters throughout Mississippi. Of 1,153 anglers volunteering to participate, 224 (19%) returned diaries with at least one recorded fishing trip that was usable for data analysis. We found no significant (P < 0.05) correlations between angler diary catch per unit effort (CPUE; fish/h) and creel survey or electrofishing CPUE for black bass Micropterus spp. and crappies Pomoxis spp. The length distributions of black bass reported by anglers were similar to those obtained from electrofishing samples at five of seven reservoirs when fish smaller than 250 mm were excluded from the comparisons. The length distributions of crappies obtained from diary reports were different from those obtained from electrofishing samples. Low participation by anglers for catfish (Ictaluridae) and sunfish Lepomis spp. precluded similar analyses for those species. The participating anglers differed from the general angling public in Mississippi, possibly biasing estimates of catch rate. Although angler diaries may have value for monitoring angler catch rate trends for diverse types of anglers and in numerous water bodies, our results show that angler diary data should not be used to replace traditional fishery assessment data.
Agricultural pollution of surface water, groundwater and marine waters relates to the contamination of drinking water, and harmful effects on ecosystems and costs for recreational activities, cultural values and commercial fisheries. After the introductory section, this paper examines the recent trends and economic costs of agricultural water pollution. Subsequent sections discuss recent Organisation for Economic Co-operation and Development (OECD) policy experiences in addressing water pollution in agriculture, and the medium outlook for pollution across OECD countries. The final section explores ways forward toward sustainable management of water quality in agriculture.
Most research on catch-and-release (C&R) in recreational fishing has been conducted from a disciplinary angle focusing on the biological sciences and the study of hooking mortality after release. This hampers understanding of the complex and multifaceted nature of C&R. In the present synopsis, we develop an integrative perspective on C&R by drawing on historical, philosophical, socio-psychological, biological, and managerial insights and perspectives. Such a perspective is helpful for a variety of reasons, such as 1) improving the science supporting successful fisheries management and conservation, 2) facilitating dialogue between managers, anglers, and other stakeholders, 3) minimizing conflict potentials, and 4) paving the path toward sustainable recreational fisheries management. The present work highlights the array of cultural, institutional, psychological, and biological factors and dimensions involved in C&R. Progress toward successful treatment of C&R might be enhanced by acknowledging the complexity inherent in C&R recreational fishing.
Sixty‐two years of voluntarily collected angling logbook data from a large natural Danish lake were used to study variation in pike, Esox lucius L., CPUE (catch per unit effort), expressed as no. of captured pike per boat trip, as an index of stock size. Pike CPUE was positively related to pike release rate by anglers and negatively affected by certain commercial fishers. The stocking of young‐of‐the‐year pike and a fishery‐dependent index of perch, Perca fluviatilis L., abundance (which may be pike prey or predator depending on size) did not correlate with pike CPUE. Analyses of the size distribution of pike, based on sizes of annual record trophy pike captured by anglers, confirmed the negative impact of commercial pike fishing and revealed a positive influence of air temperature. It is concluded that high‐quality angler logbooks that record effort and catch can be a cost‐effective tool to inform lake fisheries management by revealing long‐term population trends. Further, state space modelling, a statistical technique not yet seen in recreational fisheries science, is recommended as a tool to model proxies for population dynamics from angler logbook data.
The use of both linear and generalized linear mixed‐effects models ( LMM s and GLMM s) has become popular not only in social and medical sciences, but also in biological sciences, especially in the field of ecology and evolution. Information criteria, such as Akaike Information Criterion ( AIC ), are usually presented as model comparison tools for mixed‐effects models.
The presentation of ‘variance explained’ ( R ² ) as a relevant summarizing statistic of mixed‐effects models, however, is rare, even though R ² is routinely reported for linear models ( LM s) and also generalized linear models ( GLM s). R ² has the extremely useful property of providing an absolute value for the goodness‐of‐fit of a model, which cannot be given by the information criteria. As a summary statistic that describes the amount of variance explained, R ² can also be a quantity of biological interest.
One reason for the under‐appreciation of R ² for mixed‐effects models lies in the fact that R ² can be defined in a number of ways. Furthermore, most definitions of R ² for mixed‐effects have theoretical problems (e.g. decreased or negative R ² values in larger models) and/or their use is hindered by practical difficulties (e.g. implementation).
Here, we make a case for the importance of reporting R ² for mixed‐effects models. We first provide the common definitions of R ² for LM s and GLM s and discuss the key problems associated with calculating R ² for mixed‐effects models. We then recommend a general and simple method for calculating two types of R ² (marginal and conditional R ² ) for both LMM s and GLMM s, which are less susceptible to common problems.
This method is illustrated by examples and can be widely employed by researchers in any fields of research, regardless of software packages used for fitting mixed‐effects models. The proposed method has the potential to facilitate the presentation of R ² for a wide range of circumstances.
Angling catch records are frequently used to reveal fish population developments. It is therefore important to understand the determinants of angling catches. This study focused on angler-related, biotic and abiotic factors influencing catchability of Eurasian perch, Perca fluviatilis L. A multi-lake (21 lakes) study based on angling diaries collected in Mecklenburg-Vorpommern, Germany (2006/2007), found that angler-related factors such as fishing experience, species preference and bait/lure type had a large impact on perch catch rates. Additionally, environmental conditions (nutritional status and water transparency) affected either the size or the number of perch caught by anglers. Catch rates varied seasonally, which was confirmed by an experimental fishery on a gravel pit (2008). This portion of the study showed that altered food availabilities in the course of the year caused food limitation in perch, which in turn facilitated high catch rates and female-biased exploitation in autumn. It is concluded that both angler-related and abiotic factors interact affecting perch catch rates and size of perch captured in recreational angling.
The European catfish Silurus glanis has been cultivated in extensive ponds in central and Eastern Europe in association with carps for more than 100 years. The total production of S. glanis in aquaculture from ten European countries (Austria, Bulgaria, Croatia, Germany, France, Hungary, Greece, Macedonia, Poland, Czech Republic and Romania) was 602 t in 1993 and presently is about 2 000 t. Production is increasingly from intensive pond culture or in heated/geothermal waters. The flesh is white, boneless, easy to prepare, and low in fat (6 to 8%). The taste is mild but is subject to off-flavour. The fish are filleted (yields about 40% without skin) and the flesh is cut into steaks or smoked). During the last 10 years, research in Czech Republic, France and other European countries have developed technologies for artificial reproduction, evaluated population genetics and addressed problems of conservation. Growth is higher in males and research is in progress to produce triploids fish. While propagation techniques have progressed, production remains low and the cost of production is still high. Thus availability is low and the product remains poorly known. © 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Éditions scientifiques et médicales Elsevier SAS. All rights reserved.
Abstract Culture-based fish yield in non-perennial reservoirs of Sri Lanka was related to reservoir morphometry and stocking density. The reservoirs were stocked mainly with fingerlings of one Chinese and three Indian major carp species, common carp, Cyprinus carpio L., and the genetically improved farmed tilapia strain of Nile tilapia, Oreochromis niloticus (L.), at four pre-determined species combinations and a range of stocking densities [SD (fingerlings ha−1)]. Twenty-three reservoirs were harvested successfully at the end of the culture period of 2002–2003. Basic limnological and morphometric parameters, including shoreline development (DL) and shoreline area ratio (RLA), were estimated for each of the 23 reservoirs. Bray–Curtis similarity and non-metric multidimensional scaling using mean values of limnological data revealed that reservoirs could be ordinated into two major clusters, one with intact sample distribution due to similar trophic characteristics and the other with scattered sample distribution. Reservoirs in the cluster with similar trophic characteristics showed significant correlation (P < 0.05) between RLA and total fish yield (Y). A multiple regression equation, Y = −693 + 4810 RLA + 0.484 SD, was generated to estimate fish harvest in relation to SD.
The rapid expansion of recreational fishing in Portugal over the last 20 years, along with the multiplicity of pressures affecting inland fisheries, demands the urgent recognition of the social and economic values. Sport-angling information is still inadequate to formulate management actions. To address this issue, a regional survey on freshwater recreational fishing in all the municipalities of the Guadiana River Basin was carried out in 1999. The survey, based on 1998 data, provided information on the profile of anglers, preferences as regards reservoirs and sections of rivers fished, frequency of fishing trips, motivation, expenditure, fish species caught, an estimation of total catch and its destination, interest in competitions, enforcement and personal opinions. The results recommended improved communication and feedback between users, and mechanisms for future regional development and management of recreational fisheries.
The perch spawning stock catch (1985–1988) of the Rimov Reservoir was studied using Rimov fyke-nets and Klicava traps. Spawning and an increased catch were found in the tributary area 1 week earlier than in the main waterbody. The peak catches moved from depths of 3–4 m to the surface during the spring homothermy. After the development of thermal stratification, the peak catch moved to depths with a temperature range of 8–12°C. Catch per unit effort decreased during the second half of the spawning period but shifting the fyke-nets to depths where spawning activity was maximum increased the total seasonal catch by at least 100%. At the end of spawning, the peak activity was found at 6–9 m. Normal spawning stock is characterised by a strong predominance of males in the catch of the fyke-nets; postspawning females predominate in the later catches in shallow areas. Catches in the fyke-nets in the formerly wooded areas were more than four times higher than the catches from areas without tree stumps.
The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield.
While the impacts of high exploitation on fish populations and aquatic ecosystems are well-documented for commercial fishing, particularly in the marine environment, the potential biological impacts of angling received less attention. This paper discusses angling patterns within a framework of basic ecological and evolutionary literature and examines potential biological impacts of angling by focus-ing on study results associated with high exploitation rates and pronounced selective exploitation. The impacts range from impacts occurring directly on the exploited species (truncation of the natural age and size structure, depensatory mechanisms, loss of ge-netic variability, evolutionary changes), to those that occur on the aquatic ecosystem (changes in trophic cascades, trait-mediated effects). As a third category, impacts re-lated to the angling activity per se are distinguished (habitat modifications, wildlife disturbance, nutrient inputs, loss of fishing gear). Although the main threats to fish often are localized outside recreational fisheries, there is growing evidence that angling and angling associated activities can lead to a decline of fish populations and affect aquatic ecosystems in various ways provided that the degree of the fishing mortality is high and the selective exploitation is intensive. In conclusion, management implications for sustainable recreational fisheries and areas for future research are outlined.
a b s t r a c t . in 1975–2005, we utilized data on water quality (n-nH 4 + , o 2 , Cl -) and number of carp caught (CC) as environmental data, and sport fishery statistics as species data, from three fishing stretches of the Berounka River, Czech Republic. an indirect gradient analysis (DCa) for calculating the strongest gradient affecting the species data, and direct linear gradient analysis (RDa) were used for assessing the relationships among environmental and species data. all RDa models were significant and consecutively explained 45.5, 39.6, and 39.7% of the variability of species data. The strength of environmental variables was evaluated by partial RDa. in the first stretch below the City of Plzeň, with the poor water quality and low carp yields, all environmental variables were significant and the CC data alone explained 26.2% variability of species data. In the second stretch, with intermediate water quality and carps yields, only two environmental variables (o 2 and Cl -) were significant and in the third stretch near the city of Prague, with the same water quality and exceptionally high yields, the environmental variables did not significantly influence the species data. These results indicate that sport fishery statistics can be used as at least one source of information for studies of fish assemblages in streams where other data is lacking.
Angler diary programmes (n=46, 1979–1997) implemented in Ontario by the Ontario Ministry of Natural Resources are reviewed, and the different uses of angler diary programmes, levels of participation and differences in programme design are reported. In Ontario, angler diary use is common, but successful application is limited. This review revealed a variety of uses and approaches for administering angler diary programmes. Problems arise when programmes are initiated without the complete commitment of the administrators and agency, or when there is no regular review so adaptive changes can be made. If administrators realize the potential biases and problems associated with diaries, and design programmes to control them, angler diaries can provide favorable cost-effective results. With reduced funding and staffing constraints, angler diary programmes could become the primary method of data collection for specialized and remote fisheries.
A popular species for food and sport, the European catfish (Silurus glanis) is well-studied in its native range, but little studied in its introduced range. Silurus glanis is the largest-bodied freshwater fish of Europe and is historically known to take a wide range of food items including human remains. As a result of its piscivorous diet, S. glanis is assumed to be an invasive fish species presenting a risk to native species and ecosystems. To assess the potential risks of S. glanis introductions, published and ‘grey’ literature on the species’ environmental biology (but not aquaculture) was extensively reviewed. Silurus glanis appears well adapted to, and sufficiently robust for, translocation and introduction outside its native range. A nest-guarding species, S. glanis is long-lived, rather sedentary and produces relatively fewer eggs per body mass than many fish species. It appears to establish relatively easily, although more so in warmer (i.e. Mediterranean) than in northern countries (e.g. Belgium, UK). Telemetry data suggest that dispersal is linked to flooding/spates and human translation of the species. Potential impacts in its introduced European range include disease transmission, hybridization (in Greece with native endemic Aristotle’s catfish [Silurus aristotelis]), predation on native species and possibly the modification of food web structure in some regions. However, S. glanis has also been reported (France, Spain, Turkmenistan) to prey intensively on other non-native species and in its native Germany to be a poor biomanipulation tool for top-down predation of zooplanktivorous fishes. As such, S. glanis is unlikely to exert trophic pressure on native fishes except in circumstances where other human impacts are already in force. In summary, virtually all aspects of the environmental biology of introduced S. glanis require further study to determine the potential risks of its introduction to novel environments.
In Lake Myvatn, Arctic charr (Salvelinus alpinus) is economically the most important fish species. It is fast growing fish and its size at maturity is 35–50 cm at the age of 4 to 5 years. Catch statistics that are available for the whole 20th century show considerable long-term variation with the highest catch in the 1920s. The catches after 1970 are about 40% lower than the average from 1930–1969 and the annual catches for the last decade are the lowest. Stock size during the winter fishing season fluctuated considerably between years, with average annual fishing mortality of 83.9%. The Arctic charr population has been monitored annually since 1986, using standard series of gill nets of different mesh sizes. In 1988 one to three-year-old fish were heavily reduced in numbers during the summer months. There are indications of a similar event in 1997. In both years the charr changed its main diet from Cladocera and chironomid midges to three-spined sticklebacks Gasterosteus aculeatus and snails. At the same time its condition deteriorated. The catch in the monitoring fishery in Lake Myvatn correlates with the stock size in the beginning of the following winter fishing season deduced from Leslie's method and can give prospects for the fishery in the successive fishing season. An index of abundance of young charr also correlates with the number of chironomids and cladocerans and also with ducklings that feed on the same food as the charr. Large fluctuations in the Arctic charr population in Lake Myvatn seem to be related to changes in the main food species. The catch records available from Lake Myvatn can to a large extent be used as a measure of changes of the Arctic charr population in the lake for the past century.
Reported improvements in the muskellunge angling fishery on Lake of the Woods, Ontario over the last two decades have paralleled
an increase in the practice of catch and release angling, and an increase in minimum size regulations for this species. The
overall status of muskellunge populations in this large, complex lake has proven difficult to monitor using standard assessment
methods. A volunteer muskellunge angler diary program, established in 1988, has provided a cost effective method of gathering
a large amount of information with which to track this fishery and associated populations. Results from angling diaries indicated
increased angling effort, catch and success rates for muskellunge on Lake of the Woods since the early 1990s. Although the
month of July accounted for the majority of angling effort and catch, angling success rates and sizes of fish reported in
diaries improved monthly into the late fall. Angling success rates were consistently higher in angling diaries than from creel
surveys, but both survey types showed similar long-term trends in the fishery. Angler diary data, incorporating both the numbers
of fish caught and/or seen by anglers, were used to calculate catch equality indices which proved to be sensitive to changes
in population abundance. Increased minimum length regulations for muskellunge during 1987–2001 have been largely responsible
for a decline in harvest rates from an estimated 36% in 1986 to 0% since 1999. Although higher size limits have yet to produce
more quality-sized fish in angler catches, diary survey data, supported by recent improvements in catch rates from assessment
gill nets, would indicate that muskellunge recruitment has increased. This article concludes with a brief review of how muskellunge
angler diary data has been used in the past, including recommendations to minimize biases associated with this survey method.
Commercial fishing has repeatedly been identified as a major causal factor for global declines in fish stocks. Recently, recreational fisheries have also been considered as having the potential to contribute to fisheries declines. Here, we take a global focus, contrasting the characteristics of commercial and recreational fisheries relevant to conservation and sustainability of exploited fishes in both marine and freshwater environments. We provide evidence to support our assertion that the same issues that have led to global fisheries concerns regarding commercial fishing can have equivalent, and in some cases, magnified effects in recreational fisheries. Contrasts revealed that the issues of bycatch and catch-and-release, fisheries-induced selection, trophic changes, habitat degradation, gear technology, fishing effort, and production regimes are remarkably similar among fishery sectors. In recognition of this conclusion, we present a new vision for recreational fishing that positions it on the same scale and urgency as commercial fisheries. Efforts to manage and conserve fisheries must recognise that issues and threats are similar in these fundamentally and philosophically different fisheries, as may be the solutions. Failure to recognise the similarities will further polarise these sectors and retard efforts to conserve aquatic resources. Fishing activity of any kind, whether commercial or recreational, has the potential to affect negatively fish and fisheries, as well as aquatic environments.
A 60 year (1948-2007) dataset gathered by Polish researchers working on the Vistula Lagoon fish assemblages and fisheries has shown this stressed transitional environment to be always been dominated by a few highly abundant fish species. During this period, the surrounding countries Poland and Russia (Kaliningrad) were transformed from centrally-planned economies with fixed prices to free market systems. The organization of the fishery evolved from one in which the majority of the fishing effort was expended by cooperatives, to one which was characterized by individual economic activity. The fishing gear deployed also evolved from cotton to monofilament, as well as from large sailing vessels with small-sized pair trawls to fyke nets targeting eel (Anguilla anguilla) and pound nets targeting herring (Clupea harengus). Small-sized gillnets targeting perch (Perca fluviatilis) grew in popularity as eel and pikeperch (Sander lucioperca) catches decreased. Cooperation between Polish and Russian fishery managers began in 1952 with the aim of implementing joint agreements to establish protection guidelines. The substantial nutrient loads into the lagoon in 1970 and 1980 put very large pressure on the environment, and contributed to the loss of macrophytes as well as the development of non-commercial fish populations. One of the consequences of these changes was the rapid growth of a black cormorant (Phalacrocorax carbo) breeding colony. These multi-faceted changes are considered to be the factors that have influenced the exploitation of fish assemblages in the Polish part of the Vistula Lagoon. The most evident change in the fish assemblage structure during the study period was the permanent decrease in the basin's top predators--pike (Esox lucius) and pikeperch. Eel stocking was initiated in 1970 following a crucial decline in yield from natural recruitment, and stocking was successful in increasing eel abundance.