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Responsible stock enhancement initiatives require baseline data of wild population demographic conditions that can be used in testing management outcomes. This study provides the first fishery-independent assessment of length- and age-based biological characteristics of exploited populations of Platycephalus fuscus in eastern Australia prior to stock enhancement. Sampling was conducted over seven estuaries spanning seven degrees of latitude and the geographical range of proposed stock enhancements. Populations in all estuaries showed evidence of length and age truncation, especially those subject to commercial fisheries where young individuals of both sexes dominated populations. Maximum longevities were 12 and 11 years for females and males respectively, but few females >5 years and males >3 years were generally sampled. Females dominated populations, and on average, the mean lengths and ages of females were greater than males within each estuary and across all age classes. Sexually dimorphic variation in growth was evident across all estuaries, with females attaining greater maximum lengths than males. Estuary-specific differences in individual growth were not identified. On average, over 50% of females sampled in each estuary were > the minimum legal length (MLL), but the opposite was evident for males. In contrast, over 25% of males in each estuary were > the mean length at maturity (L50), whereas in all but one estuary <13% of the females were > the L50. Stocked male and female P. fuscus should recruit to the fishery in 2 and 3 years, and contribute to the spawning stock in 1.5 and 4.5 years, respectively. This study provides important historical baseline data that can contribute to testing stock enhancement outcomes on populations. [ABSTRACT FROM AUTHOR]

Although it is widely accepted that stocking hatchery‐cultured fish can increase the number of fish, decades of scientific evidence have shown that most often those stocking efforts fail to provide the desired "demographic boost" to a naturally reproducing, self‐sustaining target population. Despite this evidence, fish stocking remains a mainstay of fisheries management programmes, even as the biodiversity of wild fish populations and other aquatic organisms are at serious risk due to habitat loss and/or overexploitation across the globe. In this perspective piece, we summarise the reasons why wild and hatchery‐produced fish are not equivalent and describe the genetic and ecological risks associated with stocking programmes. We then present our perspective on the institutional changes that need to occur to assess these risks and offer ways to transition fisheries management strategies to become more effective in conserving levels of aquatic biodiversity from populations to landscapes. We propose that a critical first step to control ill‐conceived fish stocking programmes is to have each country develop, implement, and enforce a scientifically sound National Fish Stocking Policy. To achieve the long‐term sustainability of native fish populations, it is imperative that ecological and evolutionary principles be better integrated into future conservation strategies and management actions. [ABSTRACT FROM AUTHOR]

In this paper, we review and synthesize trout management philosophy and policies for Black Hills streams in the states of South Dakota and Wyoming through the roles of hatcheries, fish stocking, and natural production from 1883 to 2023. We identified three specific fisheries management time periods (eras) in the Black Hills: (1) the early management–fry stocking era (pre‐1950), (2) the catchable‐trout stocking era (1950s to mid‐1990s), and (3) the integrated management era (mid‐1990s to present). The first era emphasized juvenile trout stocking, with little evaluation of effectiveness in terms of return to creel. The second era was characterized by greater emphasis on stocking catchable‐sized trout and a substantial increase in hatchery rearing capabilities. In the first two eras, instead of fish stocking being one of many potentially useful tools for managers of Black Hills streams, stocking was the dominant activity—leading and directing fisheries management rather than supporting it. By the third era, trout management began to embody a more encompassing and complex national ideology and philosophy that more fully considered ecology, including habitat improvement, natural reproduction of trout, defining the role of fish stocking, and understanding the relationship of trout to the depauperate native (nongame) fish fauna. We also discuss the three eras in the Black Hills in relation to national trends in trout management. In contrast to many other localities, the lack of any native salmonids and the lack of native game fish species have facilitated the development of valuable, self‐sustaining recreational fisheries in streams that support trout, with less concern for native species than in many areas with harvestable native fish species. The cultural ideology that brought western expansion of settlers to the Black Hills in search of gold, land, freedom, and prosperity was emboldened by a science‐based belief and confidence in technology and industry to rapidly shape lands and waters to improve the human condition. In part, the sculpting and shaping of Mount Rushmore symbolize that ideology. In the context of fisheries management in the Black Hills, the introduction of trout, development of stream fisheries, and investment in hatchery technology to produce catchable trout for an expanding tourist economy also exemplify that prevailing ideology, modulated by improved ecological understanding and an accompanying shift toward a more ecological management philosophy. [ABSTRACT FROM AUTHOR]

The practise of restocking and stock improvement as a means of managing fisheries and aquaculture has been widely used. However, it is difficult to claim that fish stocking is effective due to a number of challenges. One of those is the lack of suitable monitoring and assessment methods, although all assessment approaches have their strengths and weaknesses. If the full benefits of fisheries and their long-term sustainability are to be realised, it is necessary to examine the effectiveness of restocking and stock enhancement. Therefore, effective, rapid, and dependable monitoring techniques are necessary. In this study, we used an eDNA-based method to identify G. cambodgiensis at 14 sites throughout Thailand's restocking and stock enhancement programme. eDNA from this species was identified in water samples using quantitative polymerase chain reaction (qPCR) tests with primers and a probe specific to G. cambodgiensis. A successful stocking would show positive eDNA results in water samples collected from the studied sites. Only five of the studied sites returned positive eDNA readings, which could be considered a successful stocking. The locations that contained G. cambodgiensis eDNA were either confirmed to be natural habitats or were regularly stocked with a large number of hatchery fish. In this study, we demonstrated that eDNA is a reliable, fast and accurate alternative method for measuring stock improvement. [ABSTRACT FROM AUTHOR]

Common carp is one of the most important game fish in Europe. Due to the high exploitation and limited natural recruitment, direct stockings became a common and widespread stock enhancement practice in recreational fisheries. Sustainable recreational fisheries management requires continuous monitoring programs to define the stocking size and distribution of newly-stocked fish. In this study, we assess the capture rate and distribution patterns of hatchery-reared common carps in a dammed, lotic ecosystem using data from a seven-year tagging survey. Mean capture rate was 7.4% and onethird of captures happened within the first two months after release. High interannual differences were observed both in the capture rate and the temporal dynamics of captures. Movement patterns also showed interannual and interindividual differences; 30.8% of the fish were captured within 5 km of their release site, and 55.6% of the fish were captured within 10 km. More than ten per cent (12.8%) of fish caught more than 25 km far from release site. Distance travelled did not associate consistently with time between the release and capture. Our findings suggest that repeated surveys in consecutive years would be preferable than increasing the number of tagged fish in one year in angler report-based tagging surveys, and that 15-20 kms between stocking sites can ensure proper distribution of common carp in a lotic fishery even under high angling pressure. [ABSTRACT FROM AUTHOR]

Gravel pit lakes are common across Europe. These novel ecosystems serve as model systems to study human‐induced and natural colonisation of isolated lakes by fish. Fisheries‐management activities can quickly spread species over large distances, possibly homogenising fish communities across ecosystems, while fostering local fish diversity.Our objective was to evaluate the effects of lake genesis (gravel pit lakes < 100 years old vs. natural lakes of glacial genesis ~10,000 years old) and fisheries management (fish stocking activities present vs. absent) on the fish community in small lakes, while controlling for key environmental variables known to affect lake fish communities.We sampled fish communities by electrofishing and multimesh gillnetting in 47 isolated lakes managed for fisheries, and 19 unmanaged and isolated lakes of both natural and artificial origin in northern Germany. Unmanaged lakes were used as reference to assess fisheries‐management impacts in small natural and artificial lakes.We caught 178,506 fish from 30 species and found that the accumulation of native lake fish species in lakes was associated with fisheries management, which increased local species richness (α‐diversity) and number of predatory species, and reduced among‐lake variation in fish community composition (β‐diversity; i.e., homogenisation). The homogenisation‐effect associated with fisheries happened with introduced native fish species, whereas non‐native species were rarely detected.In unmanaged gravel pit lakes, the littoral fish community composition was substantially different to the communities present in both types of managed lakes and unmanaged natural lakes. Therefore, the relatively young unmanaged gravel pit lakes revealed evidence of ongoing, stochastic colonisation processes that resulted in comparatively species‐poor fish communities.We concluded that fisheries management by anglers speeds up the colonisation of gravel pit lakes with native fish species in the study area. For planning initial fish introductions in newly created gravel pit lakes, it is recommended that fish communities from ecologically similar natural lakes within the same geographical region are used as references to maintain the biotic integrity of newly created fish communities. [ABSTRACT FROM AUTHOR]

The red spotted grouper Epinephelus akaara is important for commercial and recreational fishing in the coastal waters of East Asia. In Japan, approximately 850,000 juveniles are released annually for stock enhancement, and the catch in several release areas has increased. Life‐history traits are important for fisheries management and stocking programmers. The age, growth, and mortality of fish collected from the central Seto Inland Sea from June 2012 to November 2014 were examined using 1022 sectioned sagittal otoliths, and the yield‐per‐recruit (YPR) was calculated. The opaque zones in the otoliths were confirmed to be annuli, formed mainly between June and July. The oldest fish was 16 years old. The percentage of those between two and five years was approximately 80%, whereas that of more than ten years was only 0.6%. The five parameters von Bertalanffy growth equation was calculated as: TLt = 390 {1 − 0.23[(t − 3.78)2 + 1]−1}{1 − exp [−0.34 (t + 0.28)]}, where TLt is the total length (mm) at t (year). The total, natural, and fishing mortality rates were calculated to be 0.80, 0.24–0.31 and 0.49–0.56 year−1, respectively. The YPR analysis indicated that the current fishing mortality rate (Fcurrent) was higher than F0.1 and Fmax, and that increasing the age at first capture is more effective than decreasing F for increasing the YPR. These results provide important information for fisheries management and the stocking of E. akaara. [ABSTRACT FROM AUTHOR]

Maru is an endemic species of the Kapuas river which is currently in a positive state and its demand continues to increase. The optimal density of this fish culture has not been found with a system that is suitable for its habitat, namely recirculation. The purpose of this study was to determine the optimal stocking density with a recirculation system on growth performance. The maru seeds used are 7-9 cm in size, with a combination of pellet and magot feed with a 5% feed dose. This study used a completely randomized design (CRD) with 4 treatments and 3 repetitions. Treatment A: Stocking density of 2 birds/liter, Treatment B: 3 birds/liter, treatment C: 4 birds/liter, treatment D (control): 1 head/liter without any recirculation system. Data collection is carried out once every 15 days, while water quality parameter data is carried out 2 times a day, namely in the morning and evening. The growth rate between treatments A and B had a significant value and was significantly different (p<0.05). Where the absolute growth (length and weight) in treatment A was 9.93 cm and 10.02 gr. Followed by treatment B of 6.3 cm and 5.84 g. Treatment B had significant differences from treatments C and D. Where the absolute length and weight growth of treatments C and D were 3.43 cm, 3.9gr, and (3.2 cm, 3.69 gr, respectively). The results of this study indicate that the density of stocking is inversely proportional to the growth in length and weight of maru. Furthermore, the water quality during maintenance is still in the fairly good category, this is the impact of the recirculation system on the waters that can maintain water quality during maintenance. [ABSTRACT FROM AUTHOR]

Simple Summary: In a great part of the world, trout fishing has long inspired human spiritual ideals of immersion into nature and recreation, far removed from the fast-encroaching urbanization. Concurrently, these values and emotions fueled a white-hot business, establishing a florid market of outdoor recreation. Since the 20th century, the trout-culture industry strived to provide anglers with fishing entertainment by stocking massive amounts of non-native trouts in dozens of countries, irrespective of the lakes' and rivers' carrying capacity. This had dire consequences on the structural and functional diversity of these ecosystems. "Trout wars" sparked throughout the world between the promoters of stocking activities and the promoters of "wild trout management" and ethics. The "Italian trout war" has been fought on the harsh battleground of trout taxonomy, ecology, distribution, and native vs. non-native interfertile species. Northern Italy, home to the Italian Alpine and subalpine trouts and economic center of the national trout-culture and stocking industry, was particularly affected by this clash. We review here the state of art of this ongoing debate, outlining our scientific view of the taxonomy, evolution, distribution, and sustainable management of the native Italian trouts of northern Italy. During the last 150 years, the trout-culture industry focused on enhancing trout populations by stocking, in response to the growing anglers' demand and the habitat degradation associated to the rapid urbanization and hydropower development. The industrialized north of Italy, home to the Italian Alpine and subalpine trout populations, is the source of most of the revenues of the national trout-culture industry. Its rapid growth, and the massive introduction of non-native interfertile trouts eroded the genetic diversity of native lineages, leading to harsh confrontations between scientists, institutions, and sportfishing associations. We review here the state of the art of the taxonomy and distribution of the northern Italian native trouts, presenting both scientific results and historical documentation. We think the only native trouts in this region are Salmo marmoratus, widespread in this region, plus small and fragmented populations of S. ghigii, present only in the South-western Alps. We strongly recommend the interruption of stocking of domesticated interfertile non-native trouts in this area, and recommend the adoption of Evolutionary Significant Units for salmonid fishery management. We further propose future research directions for a sustainable approach to the conservation and ecosystem management of the fishery resources and inland waters of northern Italy. [ABSTRACT FROM AUTHOR]

This document presents information on Atlantic Salmon (Salmo salar) from Salmon Fishing Area (SFA) 15 (northern New Brunswick in DFO Gulf Region) of relevance to the development of the status report by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). There are 19 rivers with confirmed presence of Atlantic Salmon in this area of which the Restigouche River is the largest river. Data are presented and interpreted relative to the following: biological characteristics, stocking of fish, area of occupancy based on juvenile surveys, indicators of adult abundance from monitored rivers, freshwater production based on juvenile surveys and smolt production, and factors which may be constraining Atlantic Salmon abundance. For the rivers in this area, the indices of adult abundance suggest that there were more Salmon in the mid to late 1980s than there have been in the past 15 years. As a result of changes in fisheries management, spawning escapement has increased from the 1970s and early 1980s resulting in increased abundance of juvenile Salmon. The principal threats in SFA 15 are: habitat alteration including habitat fragmentation due to non-compliant culverts, hydroelectric power generation, disease, unreported poaching and aboriginal catches and, cumulative effect of ecosystem changes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fish biomass were driven by fish stocking, catches, and ecological effects. • The ecosystem was unstable and showed a decreasing trend in maturity. • The ten-year fishing ban may fail to achieve the expected goal of restoration. • Fish of different feeding types require different targeted policies. With increasing anthropogenic activities, freshwater ecosystems around the world are becoming increasingly affected by various pressures, including eutrophication, overfishing, and irrational stocking, which may have a negative impact on the food web structure. Despite the extensive research and proposed management measures for eutrophic lakes, there are only few analysis on long-term monitoring data regarding fishery resources. Additionally, there is a lack of evaluation and prediction of the effectiveness of current fish management policies. To remedy this, we analyzed long-term monitoring data from Lake Taihu, China, a severely eutrophicated lake with a skewed fish size structure exhibiting dominance of small individuals. We first constructed 14 Ecopath models to investigate how trophic interactions and biomass fluxes changed from 2007 to 2020. Subsequently, the Ecosim model was used to predict how the biomass of fish and the ecosystem network respond to the initiated 10-years fishing ban. Our results demonstrate long-term changes in fish biomass and ecosystem stability. The analyses revealed that 1) the biomass development in different feeding types of fish is controlled by human activities (mainly catches and stocking) and trophic interactions and 2) the rate of decline in ecosystem network stability slows down during the fishing ban. The primary focus of this study was to fill the gap in long-term serial studies of fish monitoring data and ecosystem stability in the lake and, for the first time, to predict the outcome of the fishing ban from an ecosystem perspective using the Ecosim model. Overall, our results emphasize the importance of rational stocking and fishing policies and provide a better understanding of the changes in the ecological dynamics in Lake Taihu of relevance for the management and restoration of the lake. [ABSTRACT FROM AUTHOR]

Obtaining the best possible estimates of individual growth parameters is essential in studies of physiology, fisheries management, and conservation of natural resources since growth is a key component of population dynamics. In the present work, we use data of an endangered fish species to demonstrate the importance of selecting the right data error structure when fitting growth models in multimodel inference. The totoaba (Totoaba macdonaldi) is a fish species endemic to the Gulf of California increasingly studied in recent times due to a perceived threat of extinction. Previous works estimated individual growth using the von Bertalanffy model assuming a constant variance of length-at-age. Here, we reanalyze the same data under five different variance assumptions to fit the von Bertalanffy and Gompertz models. We found consistent significant differences between the constant and nonconstant error structure scenarios and provide an example of the consequences using the growth performance index -0 to show how using the wrong error structure can produce growth parameter values that can lead to biased conclusions. Based on these results, for totoaba and other related species, we recommend using the observed error structure to obtain the individual growth parameters. [ABSTRACT FROM AUTHOR]

Despite different approaches used to assign the risk scores for missing information in productivity susceptibility analysis (PSA)--a widely used semi-quantitative risk assessment tool for target and non-target fisheries stocks--for the selected attributes of a given species, no formal comparison has been made between scoring approaches in terms of how well they can predict species vulnerability. The present study evaluated the PSA findings of 21 bycatch stocks of the Hilsa (Tenualosa ilisha) gillnet fishery of Bangladesh using two different scoring approaches (the conservative scoring approach, CSA; and the alternative scoring approach, ASA) to determine the most reliable approach to minimize false estimates of species vulnerability. Our analysis revealed that the V scores increased by 0.0-0.20 with a mean value of 0.09 for 21 selected bycatches when CSA was applied. The inconsistency between the vulnerability (V)-score-suggested fishing status (V ≥ 1.8 = underfishing, V > 1.8 = overfishing) and the fishing status defined by exploitation rate (E > 0.5 = overfishing, E < 0.5 = underfishing) were 38.1% and 19.0% under CSA and ASA, respectively. Likewise, the consistency between the V-score-suggested fishing status and fishers' perceived catch trends was found to be higher when using ASA than when using CSA. Our analysis suggests that CSA could overestimate species vulnerability. Therefore, ASA is more reliable than CSA in PSA, which may increase the confidence of fisheries stakeholders in PSA. [ABSTRACT FROM AUTHOR]

The stocking of hatchery‐origin fish into rivers and lakes has long been used in fisheries management to try to enhance catches, especially for trout and salmon species. Frequently, however, the long‐term impacts of stocking programmes have not been evaluated. In this study, the authors investigate the contribution of a stocking programme undertaken to support the rod catch of sea trout in the Shetland Islands, UK. Once a highly productive recreational fishery, Shetland sea trout catches crashed in the mid‐1990s. Around the time that stocking began, increases in rod catches were also reported, with advocates of the stocking highlighting the apparent success of the programme. Using a suite of genetic markers (microsatellites), this study explores the contribution of the stocking programme to the Shetland sea trout population. The authors found that the domesticated broodstock and wild spawned brown trout from seven streams were genetically distinct. Despite extensive stocking, wild spawned brown trout dominated, even in those streams with a long history of supplementation. The majority of sea trout caught and analysed were of wild origin – only a single individual was of pure stocked origin, with a small number of fish being of wild × stocked origins. This study suggests that stocking with a domesticated strain of brown trout has made only a very limited contribution to the Shetland Islands rod catch, and that the revival of sea trout numbers appears to be driven almost exclusively by recovery of trout spawned in the wild. [ABSTRACT FROM AUTHOR]

In recent years, the issue of spawner harvesting has been frequently addressed by different groups of stakeholders involved in the exploitation of fish resources. The increasingly numerous angling circles, which use these resources recreationally, question the current rules of fish stocking management in Poland, and its legal and economic status has become the focus of scientists' interest. The aim of the study was to present and discuss the results of a questionnaire survey addressed to managers and owners of lake fisheries entities in order to identify the determinants of fisheries management related to spawner harvesting. Questionnaires were collected from a total of 76 entities, and concerned 1921 lakes with a total area of 174,078 ha, which accounts for more than 64% of the total area of lakes used for fishing and angling purposes in Poland. The paper presents inter alia the occupational characteristics of the respondents; their positions on the effect of spawner harvesting on lake ecosystem, environmental protection, and social factors; anglers' assessments of spawner harvesting; the actual and potential methods for regulating this harvesting; and the negative and positive effects of the introduction of a prohibition on this harvesting. The results show that the respondents under study generally do not see the need for the introduction of additional (except those already in place) regulations concerning spawner harvesting, most of them notice the adverse effects of their introduction, but they are also aware of the possible changes and their impact on management. [ABSTRACT FROM AUTHOR]

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

Reservoirs are aquatic resources with the potential to increase India's fish production through inland fisheries. Thippagondanahalli is a medium-size reservoir on Arkavathy River, a tributary of the Cauvery. It is located in Bangalore rural district of Karnataka (12°58′24″ to 12°96'49" N 77°20′33″ to 77°35′63″ E) and has a water surface area of 1162 ha at full reservoir level and 784.55 m at full supply level. Fish diversity studies were conducted to examine the spatial and temporal variations in fish diversity in relation to habitat parameters. A taxonomic abundance of 25 fish species (80% of them native) belonging to 14 families and 4 orders was recorded. A range of statistical estimators such as Chao 1, Jack 1, and Bootstrap were used to assess the expected species richness. The Jack 1 method showed the highest abundance with 28 species. The littoral zone, dominated by small indigenous species, was found to have relatively higher fish diversity (Shannon index-1.86) compared to the limnetic zone of the reservoir. Shannon diversity was higher in the monsoon season (1.76) compared to other seasons. Physico-chemical parameters revealed that this waterbody is highly eutrophic. Canonical correspondence analysis between seasonal habitat characteristics and seasonal species abundance showed the abundance of the small indigenous fish Amblypharyngodon mola during the post-monsoon season, the bottom feeder Cirrhinus mrigala and the surface feeder Rasbora daniconius during the monsoon season, and the carnivores Mystus malabaricus and Channa orientalis as well as the planktivore Puntius sarana during the pre-monsoon season. This study suggests the use of fisheries management and conservation measures such as fish-aggregating devices, stocking of certified seed, and impact assessment of exotic species. [ABSTRACT FROM AUTHOR]

India is endowed with vast floodplain wetland resources (0.5 million ha), which provide both livelihood and nutritional security to much of the rural populace. These biologically sensitive ecosystems are threatened by a range of anthropogenic and climatic factors. Assessment of their ecological vulnerability, and of the environmental threats that they face, is essential both in evaluating the health of these ecosystems and in developing sustainable management strategies for conservation and fisheries enhancement. In this context, eight wetlands in the Ganga basin were studied for two consecutive years across the seasons and were characterized ecologically based on chlorophyll a, primary productivity, and trophic state index. A warming temperature (+0.20 – +0.47 °C) and a decreasing total annual rainfall (257–580 mm) have been observed along the Ganga basin in the last three decades. The chlorophyll a (mean ± S.E.) content of the water varied from 4.08±1.04 to 38.0±14.11 µg l-1. The high primary productivity, gross primary productivity/plankton respiration ratio and trophic state index correlated positively with the high fish yield in the wetlands. Analysis of data based on Carlson's method revealed five wetlands in the eutrophic category, whereas based on Lamparelli's method, two wetlands fall into the eutrophic category. The Lamparelli TSI value ranged from 54.1 in Majharia to 65.8 in Kararia among the wetlands. The Bishnupur wetland in West Bengal and Kararia wetland in Bihar were found to be eutrophic due to cascading sewage incursion from nearby towns. These altered ecosystems with high TSI values were prudently exploited by selecting suitable fish species for high fish production, and a fish yield of 1200 kg ha-1 yr-1 was achieved in Bishnupur. The study revealed that eutrophic wetlands can be strategically managed for maintaining both ecosystem services and fish production. Careful selection of suitable fish species and stocking rate is crucial. The planned disposal and treatment of sewage is recommended to maintain the ecological health of floodplain wetlands for sustainable fisheries management in the context of a changing climate. [ABSTRACT FROM AUTHOR]

Growth models estimate life history parameters (e.g., growth rates and asymptotic size) that are used in the management of fisheries stocks. Traditionally in fisheries science, it was common to fit one growth model--the von Bertalanffy growth model--to size-at-age data. However, in recent years, fisheries science has seen an increase in the number of growth models available and the evaluation of multiple growth models for a given species or study. We reviewed n = 196 peer-reviewed age and growth studies and n = 50 NOAA (National Oceanic and Atmospheric Administration) regional stock assessments to examine trends in the use of growth models and model selection in fisheries over time. Our results indicate that the total number of age and growth studies increased annually since 1988 with a slight proportional increase in the use of multi-model frameworks. Information theoretic approaches are replacing goodness-of-fit and a priori model selection in fisheries studies; however, this trend is not reflected in NOAA stock assessments, which almost exclusively rely on the von Bertalanffy growth model. Covariates such as system (e.g., marine or fresh), location of study, diet, family, maximum age, and range of age data used in model fitting did not contribute to which model was ultimately the best fitting, suggesting that there are no large-scale patterns of specific growth models being applied to species with common life histories or other attributes. Given the importance and ubiquity of growth modeling to fisheries science, a historical and contemporary understanding of the practice is critical to evaluate improvements that have been made and future challenges. [ABSTRACT FROM AUTHOR]

Uncertainty hampers innovative mixed‐fisheries management by the scales at which connectivity dynamics are relevant to management objectives. The spatial scale of sustainable stock management is species‐specific and depends on ecology, life history and population connectivity. One valuable approach to understand these spatial scales is to determine to what extent population genetic structure correlates with the oceanographic environment. Here, we compare the level of genetic connectivity in three codistributed and commercially exploited demersal flatfish species living in the North East Atlantic Ocean. Population genetic structure was analysed based on 14, 14 and 10 neutral DNA microsatellite markers for turbot, brill and sole, respectively. We then used redundancy analysis (RDA) to attribute the genetic variation to spatial (geographical location), temporal (sampling year) and oceanographic (water column characteristics) components. The genetic structure of turbot was composed of three clusters and correlated with variation in the depth of the pycnocline, in addition to spatial factors. The genetic structure of brill was homogenous, but correlated with average annual stratification and spatial factors. In sole, the genetic structure was composed of three clusters, but was only linked to a temporal factor. We explored whether the management of data poor commercial fisheries, such as in brill and turbot, might benefit from population‐specific information. We conclude that the management of fish stocks has to consider species‐specific genetic structures and may benefit from the documentation of the genetic seascape and life‐history traits. [ABSTRACT FROM AUTHOR]

Biomass limit reference points are widely used in fisheries management and define the biomass threshold (BT) below which stock productivity (i.e. recruitment) is likely to be impaired. Scientifically sound and transparent methods for estimating BTs are therefore needed together with ways of quantifying uncertainties. The main focus of the study was placed on two methods currently applied to several small‐bodied pelagic species in the Northeast Atlantic. These methods have not formerly been described in the scientific literature and are in the present study being compared with some already described methods, of which one is broadly applied outside the Northeast Atlantic. Using a combination of data simulations and data from 51 small‐bodied pelagic fish stocks, we analysed the sensitivity of estimated BTs to (a) the choice of method, (b) time‐series length and (c) stock development (e.g. rebuilding or declining). It was demonstrated that estimated BTs are associated with considerable uncertainty not previously quantified. Furthermore, the level of the estimated threshold and the amount of uncertainty depended on choice of method, time‐series length and stock development trends. Hence, this study contributes to improving the quality of future biomass limit reference points by providing guidance regarding choice of method and how to demonstrate stock‐specific uncertainties. [ABSTRACT FROM AUTHOR]

• We developed a marine ecosystem model for trade-offs between fishing and enhancement stocking. • The impact of fishing effort on the marine ecosystem was not well compensated by release of a single target species. • We designed an orthogonal experiment with three factors (key species) and four restocking release levels to determine the optimal release rate. • We optimized the key species release and fishing strategy to improve the marine biomass, trophic level, and biodiversity. The implementation of marine ecosystem management requires modeling that accounts for the trade-off between exploitation in fisheries and protection activities (e.g., enhancement and release, artificial reefs). Researchers are increasingly interested in the trends of fishery resources under these joint driving forces due to the negative impacts of resource exploitation and the positive impacts of marine protection. Using the sea around Juehua Island in China's Bohai Sea as a case study, we developed a marine ecosystem model based on the Ecopath with Ecosim software to analyze the trends in fishery resources driven both by fishing and stock enhancement. When the fishing effort exceeded 42 % of the 2019 value, the biomass of top predator Platycephalus indicus decreased by 50 %, indicating a regime shift. When the fishing effort increased to 340 % of the 2019 level, the ecosystem shifts to an alternative stable state occurs, indicating destabilization of the marine ecosystem. The impact of fishing effort on the marine ecosystem was not well compensated by release of a single target species. We also designed an orthogonal experiment with three factors (the key species Fenneropenaeus chinensis , Paralichthys olivaceus , and Charybdis japonica) and four restocking release levels to determine both the optimal release rate for each species individually and the optimal combination of different species. If the 2019 fishing effort is maintained, the release of 125 × 106 juvenile F. chinensis , 400 × 103 juvenile P. olivaceus , and 15 × 106 juvenile C. japonica would be an optimal solution to improve the marine biomass, trophic level, and biodiversity. Our results provide insights into ecosystem-based management strategies for implementing a policy to limit fishing in the study area and for scientifically determining the restocking release rates. [ABSTRACT FROM AUTHOR]

Fisheries management has evolved in Malawi from a traditional system to a centralized regime and lately to co-management fisheries systems, although, success stories about sustainability of the fishery resources are few. Open access nature of fisheries resources has posed a challenge to management regimes. Resource overexploitation has continued in a majority of fisheries worsened by large stretches of the shoreline manned by a single fisheries field staff, and limited capacity by DoF to monitor and manage the fishery. However, isolated localities have upheld management styles that have facilitated sustainable exploitation. Mbenji Island fishery 'managers' have ensured high compliance to fisheries rules and regulations among fishers through strict enforcement and maintained abundant fish stocks amid visibly declining levels of fish in vast localities of Lake Malawi and other water bodies in Malawi. There is, therefore, need to take the Mbenji Island success story to other fishing communities to learn from their fisheries management strategies. Information Communication Technology (ICT) as a powerful means in mobilizing communities to take charge of their own development should support 'best practices' and offer fishing communities access to the same type of services and advantages. If appropriately applied, ICT can provide for real-time monitoring of fisheries resources as fishers alarm law enforcers to move in at appropriate times. Fishers also strike deals on mobile phones for the day's catch even before landing at shore. This reduces post-harvest waste from delayed handling of fish. Computers have been used for data management, storage and analysis as well as accessing internet services. Studies have shown commonalities in fisher communities in terms of socio-economic and cultural characteristics. On the basis of such an advantage, more could be shared among such communities. Management success can be adopted by other communities of fishers through use of ICT such as radio programs (supplemented by phone-in sessions) undertaken by local-level resource users. These programs provide locally available information and knowledge on best practices aimed at sustainability with means within communities. This encourages community members in other localities to come together to seek the way forward on the basis of lessons from successful communities aired on local radio stations (both community or national radio stations). It is easier to adopt practices that have worked in near vicinities. After all, what is currently called comanagement is seemingly based on indigenous knowledge of fishers and other resource users. Mbenji Island is one of the custodians of ICT option in small-scale fisheries management of Lake Malawi. Information Communication Technology provides opportunity for both the Malawi Department of Fisheries (DoF) and fishers with information about fisher community activities including catch and market regardless of distance. [ABSTRACT FROM AUTHOR]

The ecosystem approach to fisheries management is a conceptual and practical framework consistent with, and supportive of, climate change adaptation at the national and regional level. Implementing an ecosystem approach can contribute to climate change adaptation by improving ecosystem resilience and reducing vulnerability to climate change, by providing planning strategies and tools to monitor and assess the impacts of climate change on fisheries, and by relying on precautionary, flexible, and adaptive approaches that account for the uncertainties, surprises, unpredictability, and dynamism of ecosystems in a changing climate. In this article, I provide an overview of some key considerations framing the mandate and capacity of regional fisheries management organizations and arrangements to implement ecosystem approaches in the context of climate change. The article first addresses the extent to which international law of the sea, and in particular the 1995 United Nations Fish Stock Agreement, endorses and implements an ecosystem approach to fisheries for the management of straddling and highly migratory stocks. It then addresses the barriers to more effective implementation of an integrated and adaptive ecosystem approach to fisheries in transboundary settings, including the decentralized and consensus-based nature of international law, stationary visions of ecosystems, and principles of certainty and stability. This analysis is then expanded to focus on specific challenges of adapting to climate-induced changes to transboundary stocks distribution and abundance. I address preparing and planning for climate change, responsive decision-making procedures, regulation of new fisheries, jurisdictional challenges, enhancing marine resilience, and revisiting allocation agreements, highlighting legal provisions and policy developments that may support or enhance the adaptive capacity of transboundary fisheries arrangements. I conclude that, despite some supportive legal provisions and practices, structural, legal, and political barriers severely hinder the pace and the scope of required governance and management responses to climate-induced changes to transboundary stocks. [ABSTRACT FROM AUTHOR]

Climate change is shifting the distribution of fish stocks that straddle between exclusive economic zones (EEZ), challenging transboundary fisheries management. Here, we examine the projected sharing of jointly managed transboundary fish stocks between Canada and the United States. We hypothesize that ocean warming will alter the sharing of fish stocks between the two countries, and that such changes will intensify under a high carbon emission scenario. We look at the specific cases of the International Pacific Halibut Commission that manages Pacific halibut (Hippoglossus stenolepis) and a resource sharing arrangement in the Gulf of Maine for cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and yellowtail flounder (Limanda ferruginea) to discuss the management consequences of shifts in transboundary stocks. We rely on multiple Earth system models' simulations and species distribution models to estimate the change in catch potential and stock share ratio of each transboundary stock in the 21st century under two climate change scenarios. Results show that, even under a low emission scenario, most transboundary fish stocks sharing ratios, i.e., the proportion of the total catch of a fish stock taken by a given country, will change by 2050 relative to present. The overall reduction in catch potential, in addition to the changes in stock-share will further exacerbate trade-offs between changes in species catch potential. Such trade-offs in the Atlantic and Pacific regions will be amplified if a high emission scenario is followed, relative to a low carbon emission scenario. Based on the simulation results, we examine possible solution options to reduce climate risks on transboundary fish stocks and fisheries. [ABSTRACT FROM AUTHOR]

Fisheries enforcement relies on visual catch identification and quantification at sea or when landed. Silage (fish dissolved in acid) and fish blocks (block frozen fish) are promising methods for on-board processing and storage of low-value catches. We examined the use of non-destructive sampling and two DNA-based methods, quantitative PCR (qPCR) and metabarcoding, to assess species composition and relative abundance in industrial grade experimental silage and fish blocks. We demonstrate the ability to identify and quantify DNA from fish species in both products. qPCR analysis of small silage samples collected over 21 days detected all target control species. DNA from one species (Atlantic wolffish) was consistently overrepresented while, for three species of gadoids (Atlantic cod, haddock and whiting), the DNA content matched input tissue proportions with high accuracy. qPCR and metabarcoding of fish blocks, sampled as run-off water and exterior swabs, provided consistent species detection, with the highest variance observed in quantification from swab samples. Our analysis shows that DNA-based methods have significant potential as a tool for species identification and quantification of complex on-board-processed seafood products and are readily applicable to taxonomically and morphologically similar fish. There is, however, a need for establishing DNA/weight calibration factors for primary fisheries species. [ABSTRACT FROM AUTHOR]

Translocation into a novel environment through common fisheries management practices, such as fish stocking, provides opportunities to study behavioural and fitness impacts of translocations at realistic ecological scales. The process of stocking, as well as the unfamiliarity with novel ecological conditions and the interactions with resident fish may affect translocated individuals, leading to alterations of behaviours and causing fitness impacts.Our objectives were to investigate how aquatic top predators behaviourally establish themselves and compete with resident individuals following introduction in a novel lake environment and to investigate the resulting fitness consequences.Using high‐resolution acoustic telemetry, we conducted whole‐lake experiments and compared the activity, activity‐space size and fate of translocated and resident individuals in two model top predators, the northern pike Esox lucius (n = 160) and European catfish Silurus glanis (n = 33). Additionally, we compared the reproductive success of translocated and resident northern pike. The experiment was conducted with large (adult) individuals of different origins, resilient to predation, but subject to agonistic interactions and competition with resident fish.Over a period of several months, the translocated catfish exhibited consistently larger activity‐space sizes than resident catfish, but did not differ from residents in activity and survival. The pike from one of the two translocated origins we tested also showed elevated space‐use, and both translocated origins revealed higher mortality rates than their resident conspecifics, indicating maladjustment to their novel environment. When non‐resident pike reproduced, they overwhelmingly produced hybrid offspring with resident fish, indicating that introductions fostered gene flow of non‐native genes.Our study indicates that fish introductions result in behavioural and fitness impacts even in large‐bodied top predators that experience low levels of natural predation risk. [ABSTRACT FROM AUTHOR]

Most fish stocks world‐wide are fished at maximum sustainable yield (MSY) or overfished, as many fisheries management strategies have failed to achieve sustainable fishing. Identifying effective fisheries management strategies has now become urgent.Here, we developed a spatially explicit metapopulation model accounting for population connectivity in the north‐western Mediterranean Sea, and parameterized it for three ecologically and economically important coastal fish species: the white seabream Diplodus sargus, the two‐banded seabream Diplodus vulgaris and the dusky grouper Epinephelus marginatus.We used the model to assess how stock biomass and catches respond to changes in fishing mortality rate (F) and in the size of fully protected areas within the existing system of multiple‐use marine protected areas (MPAs). For each species, we estimated MSY and the corresponding values of stock biomass (BMSY) and fishing mortality rate (FMSY), providing crucial reference points for the assessment of fisheries management.Diplodus sargus is currently in low overfishing, while D. vulgaris and E. marginatus are in high overfishing. Stock recovery to BMSY for the last two species requires a reduction of current F around 50%. This would guarantee an increase in both stock biomass (around 50% and 75% for D. vulgaris and E. marginatus respectively) and catch (around 15% and 30%) after a transient time of ~15–30 years. Alternatively, doubling the size of fully protected areas over fishable areas within the existing network of MPAs would lead to positive conservation effects for all three species without substantially affecting the overall productivity of the fishery and the total economic value of the catch.Synthesis and applications. We provide the first assessment of stock status for three coastal species in the north‐western Mediterranean and evaluate the ecological and fisheries outcomes of different management strategies. Extending full protection inside existing multiple‐use marine protected areas or reducing fishing effort outside can deliver both conservation and fisheries benefits. [ABSTRACT FROM AUTHOR]

Irish Sea fisheries have undergone considerable change in recent years following the decline of commercially important finfish stocks and their slow response to management's recovery plans. In 2015, the fishing industry called for a holistic exploration into the impact of environmental change and food web effects to identify the drivers underpinning stock dynamics. In this study, we identify correlations between large‐scale climatic indicators, temperature, primary and secondary productivity, and fish recruitment in the Irish Sea and incorporate them into an Ecopath with Ecosim food web model co‐created by scientists and fishers. Negative correlations were found between the North Atlantic Oscillation winter index (NAOw) and large zooplankton abundance and between the Atlantic Multidecadal Oscillation (AMO) and the recruitment of cod (Gadus morhua) and whiting (Merlangius merlangus). Using correlation analyses to direct the addition of environmental drivers to the Irish Sea ecosystem model improved the models fit against observed biomass and catch data and revealed the indirect impacts of environmental change as mitigated through trophic interactions. Model simulations suggest that historic environmental change suppressed the overall production of commercial finfish, limiting opportunities for the fishing industry, whilst also dampening the rate of stock recovery despite marked reductions in fishing effort. These results suggest that failure to account for ecosystem information may lead to misconceived expectations and flawed fisheries management; therefore, there is a need to operationalize ecosystem information through management procedures to support fisheries advice. [ABSTRACT FROM AUTHOR]

Simple biometric data of fish aid fishery management tasks such as monitoring the structure of fish populations and regulating recreational harvest. While these data are foundational to fishery research and management, the collection of length and weight data through physical handling of the fish is challenging as it is time consuming for personnel and can be stressful for the fish. Recent advances in imaging technology and machine learning now offer alternatives for capturing biometric data. To investigate the potential of deep convolutional neural networks to predict biometric data, several regressors were trained and evaluated on data stemming from the FishL™ Recognition System and manual measurements of length, girth, and weight. The dataset consisted of 694 fish from 22 different species common to Laurentian Great Lakes. Even with such a diverse dataset and variety of presentations by the fish, the regressors proved to be robust and achieved competitive mean percent errors in the range of 5.5 to 7.6% for length and girth on an evaluation dataset. Potential applications of this work could increase the efficiency and accuracy of routine survey work by fishery professionals and provide a means for longer‐term automated collection of fish biometric data. [ABSTRACT FROM AUTHOR]

Fish face many anthropogenic stressors. Authorities in marine, estuarine, and freshwater realms often share interdependent fisheries management goals, but address singular stressors independently. Here, we present a case study suggesting that coordinating stressor relief across management realms may synergize conservation efforts, especially to actualize restoration benefits. Major efforts are underway to restore juvenile salmon habitat across California's Central Valley landscape, but it is unclear how fisheries and flow management will influence juvenile salmon occupancy of restored sites. Leveraging monitoring data, we find that for juvenile salmon (<55 mm) to actualize benefits of restored habitats will likely require maintaining spawner abundances and flows at or above intermediate values, especially in less-connected portions of the landscape. Furthermore, restoration efforts may prioritize more connected regions to promote use of restored areas, considering that less connected areas are often uninhabited when water and spawners are scarcer. This ecosystem-based framework that evaluates interdependencies of management decisions may be applied to realize natural productivity and enhance conservation in many systems. [ABSTRACT FROM AUTHOR]

Direct DNA sequencing is powering a revolution in the application of genetics to resource management, with parentage-based tagging (PBT) increasingly applied to salmon fisheries and hatchery brood stock management and assessment. Genetic stock identification (GSI) and PBT were applied to assessment of 2018 coho salmon (Oncorhynchus kisutch) ocean fisheries and hatchery brood stocks in British Columbia (BC), Canada, with 6391 individuals successfully genotyped in fishery samples and 7805 individuals genotyped in 40 hatchery brood stocks. Population-specific contributions to mixed-stock fisheries and exploitation rates were estimated with coded-wire tags (CWTs) and GSI–PBT technologies for six populations. PBT assignments, verified by CWTs, were 100% accurate for 308 individuals with respect to population of origin and age. There was generally reasonably close agreement of estimated population-specific exploitation rates between CWT and genetic methods. We conclude that a genetic approach can improve upon the results available from the current CWT program for assessment and management of coho salmon fisheries and hatchery brood stocks in BC and provide information critical to aid in implementation of Canada's Policy for Conservation of Wild Pacific Salmon. [ABSTRACT FROM AUTHOR]

This study analyzed and compared variations of the sulcus and otolith outlines of three geographic stocks (Huanghe (Yellow) River estuary (HHE), Jiaozhou Bay (JZB), and Changjiang (Yangtze) River estuary (CJE)) of white croaker Pennahia argentata in northern Chinese coastal waters. The sulcus and otolith outline analyses via elliptical Fourier transform (EFT, i.e. outline analysis) achieved an overall classification rate of 80.4% and 87.2%, respectively. Based on a combination of sulcus and otolith shape indices (SIs) and two derivative ratios, a moderate discriminatory efficiency of 64.7% was obtained. The results indicate that sulcus outline analysis could be used alone to discriminate white croaker stocks, and that both sulcus and otolith outline analyses discriminated the fish stocks at a higher classification rate than the shape indices. The sulcus outline analysis provided complementary information to the whole otolith outline analysis for stock discrimination. Both the sulcus and otolith outline analyses efficiently discriminated between the most geographically separated CJE and HHE stocks, indicating that they could be considered discrete stocks for fishery management. [ABSTRACT FROM AUTHOR]

Despite improved knowledge and stricter regulations, numerous fish stocks remain overharvested. Previous research has shown that fisheries management may fail when the models and assessments used to inform management are based on unrealistic assumptions regarding fishers' decision‐making and responses to policies. Improving the understanding of fisher behaviour requires addressing its diversity and complexity through the integration of social science knowledge into modelling. In our paper, we review and synthesize state‐of‐the‐art research on both social science's understanding of fisher behaviour and the representation of fisher decision‐making in scientific models. We then develop and experiment with an agent‐based social–ecological fisheries model that formalizes three different fishing styles. Thereby we reflect on the implications of our incorporation of behavioural diversity and contrast it with the predominant assumption in fishery models: fishing practices being driven by rational profit maximizing. We envision a next generation of fisheries models and management that account for social scientific knowledge on individual and collective human behaviours. Through our agent‐based model, we demonstrate how such an integration is possible and propose a scientific approach for reducing uncertainty based on human behavioural diversity in fisheries. This study serves to lay the foundations for a next generation of social–ecological fishery models that account for human behavioural diversity and social and ecological complexity that are relevant for a realistic assessment and management of fishery sustainability problems. [ABSTRACT FROM AUTHOR]

Mrigal, Cirrhinus mrigala (Ham.1822), one of the Indian major carps widely distributed in Indian inland waters, has considerable aquaculture potential. Knowledge on factors such as age, growth and exploitation pattern is important in fisheries management. Here, we investigated the age structure, growth increment and exploitation pattern of mrigal in Vallabhsagar reservoir, Gujarat (India). Age composition of the studied fish was 1+ to 9+ age groups with mean total lengths 40.78, 50.99, 59.82, 66.32, 70.72, 74.56, 77.80, 80.22 and 82.50 cm. The corresponding growth rate in terms of length were 40.78, 10.21, 8.83, 6.50, 4.40, 3.84, 3.24, 2.42 and 2.28 cm observed for these age groups. The growth increment was maximum at the initial age group whereas it was moderate to low in the subsequent years of the age. The exploitation patterns of fish were 3.94 for +1, 32.02 for +2, 22.17 for +3, 25.12 for +4, 2.96 for +5, 6.16 for +6, 4.43 for +7, 2.46 for +8 and 0.74% for +9 age classes. Results depict that exploitation pattern of fish was high at early age fish stock than the higher age classes. The exploitation pattern for 1+ to 3+ age classes was 58.13%, and 41.87% contributed by 4+ to 9+ age classes. Higher catch rate of younger fishes is not a good sign for natural stocking of fish i.e., mrigal in the Vallabhsagar reservoir. [ABSTRACT FROM AUTHOR]

This paper deals with a possible approach to controlling marine fish stocks using the prey-predator model described by the Lotka-Volterra eguations. The control strategy is conceived using the sliding mode control (SMC) approach which, based on the Lyapunov theorem, offers the possibility to track desired functions, thus guaranteeing the stability of the controlled system. One of the most important aspects of this model is the identification of some parameters which characterizes the model. In this work two cascaded and Extended Kalman Filters (EKFs) are proposed to estimate them in order to be utilized in SMC. This approach can be used for sustainable management of marine fish stocks: through the developed algorithm, the appropriate number of active fishermen and the suitable period for fishing can be determined. Computer simulations validate the proposed approach. [ABSTRACT FROM AUTHOR]

Artificial enhancement of fish populations by stocking is widespread practice. Yet, very little is known about short-term dispersal, capture efficiency and the effect of fish size and habitat suitability. Asp (Leuciscus aspius Linnaeus, 1758) was chosen as a model species, because of its protection in the Svihov Reservoir and common stocking to increase predator fish abundance in many biomanipulated waters. 0+ fluorescent-marked asp were stocked in dam, middle and tributary sites of Svihov Reservoir and subsequently monitored weekly for three weeks intervals by boat electrofishing for two consecutive years. Despite similar numbers of asp stocked, the recapture was six-times lower in a year with low water level and high macrophyte density. All captured asp were identified as of hatchery origin. In the dam site most asp were recaptured in or close to the semi-closed bay with shallow water, where they were stocked. In the middle site asp spread from the unsuitable site of stocking in all directions and only very few individuals were recaptured. In the tributary site, asp dispersion was the most evident in 2017 in the direction towards the dam in the littoral zone opposite the bank that was the bank of stocking. In comparison the highest recapture was found at the site of stocking in 2018. The recaptured asp were of similar or larger size than the average stocked asp, which may suggest size-dependent mortality. The mortality of stocked asp may be affected by failure in foraging and antipredator behaviour. This research highlights the importance of post-release monitoring. [ABSTRACT FROM AUTHOR]

In central Europe, both brown trout Salmo trutta and European grayling Thymallus thymallus are threatened native salmonid species with high value in recreational angling and nature conservation. On the other hand, rainbow trout Oncorhynchus mykiss and brook trout Salvelinus fontinalis are intensively stocked non‐native species of high angling value but no value for nature conservation. This study tested if harvest rates of native salmonids are negatively correlated to intensive stocking and harvest rates of non‐native salmonids in inland freshwater recreational fisheries. Data were collected from 250 fishing sites (river and stream stretches) over 13 years using mandatory angling logbooks. Logbooks were collected from individual anglers by the Czech Fishing Union in the regions of Prague and Central Bohemia, Czechia (central Europe) and processed by the author of this study. In result, anglers harvested 200,000 salmonids with total weight of 80 tons over 13 years. Intensive stocking of multiple salmonid species lead to slightly lower harvests of native salmonids. Inversely, intensive harvests of multiple salmonid species lead to slightly higher harvest of native salmonids. Recapture rates of stocked salmonids were relatively low (0.6%–3.7%), proving fish stocking moderately ineffective. Since the effects of non‐native salmonid stocking and harvest rates on native salmonid harvest were significant but not strong, it is suggested that rivers and streams that support fishing for non‐native salmonids still support fishing for native salmonids. However, this idea does not apply for fishing sites with really high intensity of non‐native salmonid stocking – harvest rates of natives were very low on these fishing sites. [ABSTRACT FROM AUTHOR]

Fisheries management typically aims at controlling exploitation rate (e.g., Fbar) to ensure sustainable levels of stock size in accordance with established reference points (e.g., FMSY, BMSY). Population selectivity ("selectivity" hereafter), that is the distribution of fishing mortality over the different demographic components of an exploited fish stock, is also important because it affects both Maximum Sustainable Yield (MSY) and FMSY, as well as stock resilience to overfishing. The development of an appropriate metric could make selectivity operational as an additional lever for fisheries managers to achieve desirable outcomes. Additionally, such a selectivity metric could inform managers on the uptake by fleets and effects on stocks of various technical measures. Here, we introduce three criteria for selectivity metrics: (a) sensitivity to selectivity changes, (b) robustness to recruitment variability and (c) robustness to changes in Fbar. Subsequently, we test a range of different selectivity metrics against these three criteria to identify the optimal metric. First, we simulate changes in selectivity, recruitment and Fbar on a virtual fish stock to study the metrics under controlled conditions. We then apply two shortlisted selectivity metrics to six European fish stocks with a known history of technical measures to explore the metrics' response in real‐world situations. This process identified the ratio of F of the first recruited age–class to Fbar (Frec/Fbar) as an informative selectivity metric for fisheries management and advice. [ABSTRACT FROM AUTHOR]

To inform lake trout (Salvelinus namaycush) fishery management in Lake Huron that has undergone rapid ecosystem changes, we quantified lake trout production dynamics by coupling age-structured stock assessment and fish bioenergetics models. Our approach revealed the connection between piscivore production and prey consumption, included growth compensation to reproduction losses, and allowed comparisons between long-term dynamics of fishery harvests and fish production. We found that, despite the collapse of alewives, a major non-native pelagic prey fish, lake trout production appeared to be sustainable. To a certain degree, the effect of recent recruitment declines on lake trout production was offset by the release of harvest pressure from subadult lake trout and reduction in fishing and sea lamprey-induced mortality on adult lake trout. Evidence for sustainability also included the finding that no changes in average ratios of annual production to beginning-of-the-year biomass. Juvenile P:B ratio remained as high as 2.1. The effect of growth declines on adult and subadult production was offset by reduction in population mortality. Body growth and condition did not continue to decline when lake trout became more and more reliant on round goby as food, and the dynamics of total consumption of prey fish continued to be recipient controlled. [ABSTRACT FROM AUTHOR]

Fish stocks interact through predation and competition for resources, yet stocks are typically managed independently on a stock-by-stock basis. The need to take account of multi-species interactions is widely acknowledged. However, examples of the application of multi-species models to support management decisions are limited as they are often seen as too complex and lacking transparency. Thus there is a need for simple and transparent methods to address stock interactions in a way that supports managers. Here we introduce LeMaRns, a new R-package of a general length-structured fish community model, LeMans, that characterises fishing using fleets that can have different gears and species catch preferences. We describe the model, package implementation, and give three examples of use: determination of multi-species reference points; modelling of mixed-fishery interactions; and examination of the response of community indicators to dynamical changes in fleet effort within a mixed-fishery. LeMaRns offers a diverse array of options for parameterisation. This, along with the speed, comprehensive documentation, and open source nature of the package makes LeMans newly accessible, transparent, and easy to use, which we hope will lead to increased uptake by the fisheries management community. [ABSTRACT FROM AUTHOR]

Rivers are dynamic systems where flow is constantly changing, making early fish life stages with lower swimming abilities potentially vulnerable to rapid changes in water velocity. In this study, we evaluated the response of critical young life stages of three Iberian leuciscids – Achondrostoma occidentale, Iberochondrostoma lusitanicum, and Iberochondrostoma almacai – to increasing water velocities, by determining their critical swimming speed (Ucrit) and its relation with morphometric traits potentially associated with better swimmers. Results suggest a positive relation between both fish length and body depth with Ucrit and species-specific differences in swimming performance. Moreover, most fish could not withstand the maximum velocity tested (20 cm s−1), which can be surpassed in the rivers they occur. This study highlights the importance of considering individual traits for future management of fish stocks in rivers. [ABSTRACT FROM AUTHOR]

Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of stocks that are scientifically assessed, constituting half of the reported globalmarine fish catch. For these stocks, on average, abundance is increasing and is at proposed target levels. Compared with regions that are intensively managed, regions with less-developed fisheries management have, on average, 3-fold greater harvest rates and half the abundance as assessed stocks. Available evidence suggests that the regions without assessments of abundance have little fisheries management, and stocks are in poor shape. Increased application of area-appropriate fisheries science recommendations and management tools are still needed for sustaining fisheries in places where they are lacking. [ABSTRACT FROM AUTHOR]

Assessing fish stocks has important implications for fisheries management and conservation biology. Gurnards are marine demersal fish that commonly occur in the Mediterranean, but their population in this region remains to be quantified. This study examines the population structure of the longfin gurnard Chelidonichthys obscurus (Walbaum, 1792) in waters off eastern Tunisia, using morphometry and parasite assemblages. A total of 134 fish are investigated from two studied zones – the Gulf of Hammamet and the Gulf of Gabès. Discriminant analysis is used to compare gurnard populations in the two studied zones using 13 morphometric characters and the infection parameters of seven parasites. Morphometric analysis reveals strong spatial variations between the studied zones, providing evidence for the existence of an ecological differentiation along the eastern Tunisian coast. Mahalanobis distances show that body height, pectoral fin length and first dorsal fin length are the most salient morphometric characters for determining the position of samples from the Gulf of Gabès. The effectiveness of using parasites to study longfin gurnard stocks is uncertain. The use of short-lived parasites as biological tags is questionable, at least in the present case. Future research, based on complementary approaches such as otolith microchemistry and genetics, may improve our understanding of the global stock structure of longfin gurnard to suitably inform regional organizations involved in fisheries management. [ABSTRACT FROM AUTHOR]

Fishery resource management under extractive production models in the Anthropocene has contributed to the collapse of fish stocks, threatening the food and livelihood security of many people, especially fishers. Common-pool resource theory has established the relevance of the design principles of Elinor Ostrom, which favor collective actions for the management of these resources. With the help of small-scale fishers, we assessed the state of Ostrom's principles in the study system to determine the conditions required to implement fishery comanagement in the future. The communities of Taganga (Caribbean coast) and Tumaco (Pacific coast), Colombia, served as case studies because of their known dependence on fishing and because both communities are currently facing a social-ecological crisis within their top-down administrative frameworks. We performed six hearings, three in each community in 2009, 2012, and 2014, in which fishers brainstormed about the weaknesses that are closely related to Ostrom's social-ecological system framework. Additionally, 14 focus groups with 119 fishers (31 in Taganga in 2015; 88 in Tumaco in 2017) were conducted, one for each major fishing method used in each community. The obtained results made it possible to establish a community vision on the condition of the principles in each community, and the principles were prioritized by the fishers do determine which ones need immediate attention. The inhabitants of both Taganga and Tumaco expressed the urgent need to establish clear biophysical limits among resource users, to gain the participation of all actors involved, and to build nested enterprises. In particular, the community of Tumaco considered monitoring resources and regulations, establishing graduated sanctions, and recognizing basic rights to be priorities. Furthermore, future opportunities and conflicts related to fishery comanagement implementation were evident in both communities. Therefore, our results indicate that Taganga and Tumaco are not yet ready to implement fishery comanagement. Nevertheless, they have the knowledge and motivation to overcome the obstacles that prevent them from moving forward with managing their fishery resources and to face the tragedy of the commons. [ABSTRACT FROM AUTHOR]

In 1995, the so-called "turbot war" between Spain and Canada was pivotal for Iberian fisheries. The main objective of this research is to revisit the turbot war to reflect on the issue of governing fisheries on the high seas, the cause behind the war, and how it was resolved. This paper provides guidelines for future research on the management of high seas fisheries. [ABSTRACT FROM AUTHOR]

Stock enhancement activities provide an opportunity to examine density-dependent suppression of population biomass which is a fundamental issue for resource management and design of no-take-zones. We document 'catch-and-wait' fisheries enhancement where all but the largest lobsters are thrown back, recapturing them later after they have grown to a larger size. The residency, rate of return, and potential negative density-dependent effects of this activity are described using a combination of tagging and v-notching and by relating spatial growth patterns to population density defined with Catch Per Unit Effort. The results successfully demonstrated the concept of catch-and-wait practices. However, a density-dependent suppression of growth (in body size) was observed in male lobsters. This demonstrates a mechanism to explain differences in lobster sizes previously observed across EU fishing grounds with different stock densities. This negative effect of density could also affect individual biomass production in marine reserve or no-take zones. [ABSTRACT FROM AUTHOR]

The European catfish Silurus glanis is an important fish species in both commercial and recreational fisheries. Catfish is a spreading species that was reported to potentially benefit from increasing temperatures. The goal of this study was to estimate long‐term changes in harvest rates of catfish in Central Europe. This study used individual mandatory angling logbooks collected by the Czech Fishing Union in the Czech Republic (Central Europe) over the course of years 1986–2017 (32 years) to assess harvest rates of catfish. This study discovered that harvest of catfish has been increasing over time. Moreover, rivers that previously showed zero harvested catfish are beginning to display higher harvest rates of catfish. Increasing average air temperature and angling effort in the study area have positively affected harvest rates of catfish. The increased harvest of catfish could not be reliably explained by intensive fish stocking. In conclusion, while other studies show that many fish species are negatively affected by human activities and therefore show decreased harvest rates, catfish angling seems to benefit from anthropogenic changes. [ABSTRACT FROM AUTHOR]

• The study establishes a protocol for cleaning data from fishers' echo-sounders buoys prior to their use for scientific ends. • The use of the proposed protocol eliminates errors of these novel data. • The main advantages and limitations of acoustic data provided by fishers' echo-sounder buoys are analyzed and discussed. • This paper provides the first step towards the use of fishers' echo sounder buoys for scientific research. Most of the drifting fish aggregating devices (DFADs) used by the industrial tropical tuna purse seine fishery are deployed with satellite linked echo-sounder buoys. These buoys provide information on the accurate geo-location of the floating object and estimates of fish biomass aggregated along the trajectory of the DFAD. This huge amount of information is provided in large and complex datasets consisting in rough estimations of biomass, which are not originally intended to be used for scientific purposes but for fishing. This study establishes a standardized protocol for cleaning raw data from fishers' echo-sounders buoys prior to their use for scientific purposes, in which potential errors are eliminated. In addition, the main advantages and limitations of the data are analyzed and discussed. This paper provides the first step towards the use and better understanding of fishers' echo sounder buoys for scientific research. [ABSTRACT FROM AUTHOR]