Lake Fisheries Research Articles

Biomass prediction of sea lamprey population based on dynamic feature matrix composite differential equation system

This article presents a mathematical model to predict sea lamprey biomass, addressing the species' impact on the Great Lakes fishery. The model, comprising a Dynamic Age Pyramid and a Multi-species Lotka-Volterra system, captures the complex life stages and behaviors of sea lampreys. It simulates their diet, habits, and growth parameters across different ages, considering their adaptive sex ratio variation. Key findings include the model's ability to dynamically update sea lamprey population characteristics annually in response to environmental changes. Simulations show that populations with dynamic sex ratios reach equilibrium faster, with an increasing female proportion over time in resource-rich environments. However, these populations exhibit less resilience to rapid environmental shifts compared to those with stable sex ratios. The study concludes that the model offers a valuable tool for understanding complex organism-environment interactions and enhances traditional ecological models by providing a dynamic, biologically meaningful population feature matrix. This innovation aids in managing invasive species like sea lampreys without harming native ecosystems.

Exploitation and catch and release of salmonids in Idaho high mountain lakes

AbstractObjectiveHistorically, most high mountain lakes in western North America were devoid of fish, but during the past century, many have been stocked with salmonids to diversify angling opportunities. Basic information on harvest and catch and release (C–R) for high mountain lake fisheries is lacking, as is information on factors influencing catch in such settings; our objectives were to fill these knowledge gaps.MethodsUsing angling gear, we captured and implanted T‐bar anchor tags into 1163 salmonids of various species (fish of wild origin or hatchery fish stocked as fry; they could not be distinguished) in 103 high mountain lakes scattered across Idaho. Angler‐reported tag returns were used to estimate annual rates of exploitation and C–R, and a model selection approach was used to investigate factors influencing the angler catch of tagged fish.ResultAnglers reported the catch of 125 tagged fish from 52 different lakes. The mean number of days at large for reported fish was 318 days, with a range of 1 to 1465 days. Annual exploitation was 5.8 ± 7.1% (mean ± 90% confidence interval), the annual C–R rate was 8.5 ± 8.5%, and total annual catch (i.e., exploitation plus C–R) was 14.2 ± 11.0%. Of the predictive factors that we investigated, the likelihood of a fish being caught by an angler was negatively associated with hiking distance and positively associated with shoreline development index and fish length.ConclusionOur results indicate that exploitation of salmonids in Idaho high mountain lakes is low even with liberal (six‐fish daily bag limit) harvest regulations. Consequently, angler harvest is unlikely to be substantively affecting the abundance or size structure of salmonid populations in these lakes. Continued tagging would improve the precision of exploitation and C–R estimates, especially for comparisons among species.

Local Institutional Strengthening in Sustainable Lake Fisheries Resources Management System (Case Study of Tempe Lake, Wajo Regency, South Sulawesi, Indonesia)

Local Institutional Strengthening in Sustainable Lake Fisheries Resources Management System (Case Study of Tempe Lake, Wajo Regency, South Sulawesi, Indonesia)

Evaluation of the efficacy of implementing Ecosystem-Based Management (EBM) strategies within fisheries across the middle and lower Yangtze River basin lakes in China

To mitigate the decline of fishery resources and the exacerbation of water pollution in Chinese lakes and to enhance the potential and sustainable use of lake fisheries, the Chinese government has actively implemented principles and models of ecosystem-based lake fishery management. This includes promoting ecological aquaculture techniques and the “retiring pens to restore lakes” policy. To assess the effects of ecosystem-based management on Chinese lake fisheries, data from 2007 to 2020 were collected for the Qiandao Lake, Tai Lake, Hongze Lake, Luoma Lake, and Gaobao Lake in the middle and lower reaches of the Yangtze River. The study employed Data Envelopment Analysis (DEA) to assess fishing efficiency through a static input-output efficiency model. Additionally, the Malmquist index and distance functions were used for a dynamic comparison of total factor productivity (TFP) across the five lake management models. The results indicate that trends in technological progress, scale efficiency, and TFP were consistent across the lakes from 2013 to 2020. Qiandao Lake, Tai Lake, and Hongze Lake showed a positive average annual growth rate in TFP, with Qiandao Lake having the highest average annual growth rate of 13.2%. In contrast, Gaobao and Luoma Lakes experienced a negative growth rate in TFP. Furthermore, Qiandao Lake exhibited significantly higher technical efficiency than the other four lakes, effectively achieving an efficient state, followed by Hongze Lake. The study demonstrates that technological progress and variations in scale efficiency are the primary factors driving the increase in TFP in fisheries. Promoting ecosystem-based “fishing for water conservation” aquaculture techniques and restricting aquaculture scale through the “retiring pens to restore lakes” policy contribute to enhancing TFP in ecological fisheries.

Documentation of a probable spawning run of cisco Coregonus artedi in the Spanish River, Ontario, Canada

Coregonines were historically diverse and abundant in the Laurentian Great Lakes but declined throughout the 19th and 20th centuries due to multiple factors, including overfishing, habitat degradation, and interactions with invasive species. Great Lakes fishery managers are now working to restore coregonines across the basin. An important aspect of restoration efforts is the identification of key habitats, such as spawning habitats. Our understanding of the extent and diversity of coregonine spawning habitats in the Great Lakes is limited. Historical accounts suggest some cisco Coregonus artedi migrated to tributaries to spawn, but contemporary runs have not been reported. Moreover, cisco display considerable phenotypic variation, with different “forms” often occupying specific habitats or regions. We provide evidence for a previously undocumented spawning run of cisco in the Spanish River, a tributary to the North Channel of Lake Huron. We captured 31 mature and ripe fish (25 males, 6 females) approximately 52 km upstream of the river mouth on 15–16 November 2022. The fish ranged in age from 3-9 yr and total length from 287-394 mm. Of these 31 individuals, 27 were morphologically similar to C. artedi manitoulinus, a subspecies of cisco found in the North Channel; however, four individuals more closely resembled cisco captured in other areas of Lake Huron. These findings represent the best evidence of tributary spawning by cisco since the 1880s, and they have important implications for coregonine conservation and restoration efforts. Ongoing work aims to augment our understanding of the ecological and evolutionary importance of this population.

Collaborative research enhances selectivity in a lake fishery

AbstractSize and species selectivity are crucial for developing sustainable fisheries. Our objective was to estimate the selectivity of whitefish fisheries in a large European lake through a collaboration of fishers, regional managers, and scientists. Fishers were given special permits to test, within a common framework and together with scientists, selectivity enhancement strategies adapted to their own experiences. Fishers and scientists jointly tested gillnets and pontoon traps and how fishing depth, soak time, fishing season, and mesh size were affected by bycatches of undersized fish of sensitive species. Results indicated that the selectivity of the fishery could be increased, particularly by targeting whitefish adjacent to spawning sites where spatiotemporal overlap with bycatch species was lower. Proposed changes to the fishery, such as new gear, would be costly initially but could become profitable over time due to a lower cost of handling bycatch. Our findings demonstrated that co‐constructed knowledge can contribute to the governance of aquatic resources.

From lake to fisheries: Interactive effect of climate and landuse changes hit on lake fish catch?

Global warming and unpredictable nature possess a negative impact on fisheries and the daily activities of other habitats. GIS and remote sensing approach is an effective tool to determine the morphological characteristics of the lake. The present study addresses the interactive effect of climate and landuse changes hit on fish catch in lake fisheries. We used a combination of the landscape disturbance index, vulnerability index, and loss index to construct a complete ecological risk assessment framework based on the landscape structure of regional ecosystems. The results indicate an increase from around 45%–76% in the percentage of land susceptible to moderate to ecological severe risk in the landscape from 2004 to 2023. Since 1950, temperature changes have increased by 0.4%, precipitation has decreased by 6%, and water levels have decreased by 4.2%, based on the results. The results indicate that landuse, water temperature, precipitation, and water depth significantly impact the aquaculture system. The findings strongly suggest integrating possible consequences of environmental change on fish yield for governance modeling techniques to minimize their effects.

A multi-metric approach to characterize variability in Yellow Perch (Perca flavescens) use of Lake Ontario and two barrier-protected coastal wetlands

Yellow Perch (Perca flavescens) inhabit both nearshore and coastal wetland habitats of the Laurentian Great Lakes throughout their lifetime and are known to exhibit different movement life histories. However, uncertainty persists in the spatial extent of this variation and in the duration of habitat use. To explore these uncertainties, we used a multi-metric approach that included water and otolith microchemistry and tissue stable isotope ratios (δ13C, δ15N). The ratio of manganese to calcium in otoliths was used to identify transitional movements between nearshore Lake Ontario and wetland habitats while carbon and nitrogen tissue isotope ratios revealed variable duration of wetland inhabitance. Our research suggests that the multi-metric approach was useful for addressing questions that could not be answered by one method alone. Our results demonstrate individual differences in duration of coastal wetland habitat residence among Yellow Perch, which may influence their susceptibility to recreational harvest. As Yellow Perch are an important species of consideration for management agencies such as the Great Lakes Fishery Commission, exposing such diversity is important when considering the potential for differential contributions of individuals with variable movement life histories to overall population stability and resilience over time.

Acute Toxicity of the Lampricide 4-Nitro-3-(trifluoromethyl)phenol to the Mussel (Obovaria subrotunda), Its Host (Percina maculata), and a Surrogate Mussel Species (Obovaria olivaria).

The risk of lampricide applications (such as 4-nitro-3-[trifluoromethyl]phenol [TFM]) to nontarget fauna continues to be a concern within the Great Lakes Fishery Commission Sea Lamprey Control Program, especially among imperiled aquatic species-such as native freshwater mussels. The Grand River (Ohio, USA) is routinely treated for larval sea lampreys (Petromyzon marinus), and this river contains populations of the federally threatened mussel Obovaria subrotunda. Given this spatial overlap, information on the sensitivity of O. subrotunda to TFM is needed. Our objectives were to assess the toxicity of TFM to (1) adult Obovaria olivaria (a surrogate for O. subrotunda), (2) glochidial larvae of O. olivaria and O. subrotunda, (3) juveniles of O. olivaria and O. subrotunda, and (4) adult Percina maculata (host for O. subrotunda glochidia). In acute toxicity tests, TFM was not toxic to glochidia and adult mussels at exposure concentrations that exceed typical treatment rates. Although significant dose-response relationships were observed in hosts and juveniles, survival was ≥95% (Percina maculata), ≥93% (O. olivaria), and ≥74% (O. subrotunda) at typical treatment rates. However, the steep slope of these dose-response relationships indicates that an approximately 20% difference in the treatment level can result in nearly an order of magnitude difference in survival. Collectively, these data indicate that routine sea lamprey control operations are unlikely to acutely affect these species or their host. However, given that many mussel species are long-lived (30-100 years), the risks posed by lampricide treatments in the Great Lakes would be further informed by research on the potential long-term effects of lampricides on imperiled species. Environ Toxicol Chem 2024;43:1423-1430. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Angling bait consumption and stable isotope niche of two cyprinids in different lake fisheries

Abstract Terrestrial subsidies are important for freshwater ecosystems and, in lakes supporting recreational fisheries, angling baits can represent an important allochthonous input. This resource can directly contribute to fish diet but its consumption may be influenced by fish body size and the type of angling baits used in different fisheries. In this study, we evaluated angling baits consumption by two common cyprinid species, Cyprinus carpio and Rutilus rutilus, in three fishery types (specialised carp, specialised roach, and put‐and‐take fisheries). We used stable isotope analyses (δ13C and δ15N) of cyprinids, their natural prey and different angling baits in 16 gravel pit lakes located in south‐western France, including four lakes without angling. Angling baits were significantly δ13C‐enriched and δ15N‐depleted compared to natural prey. Overall, angling bait consumption was highly variable between individuals. For C. carpio, angling bait consumption averaged 30.5% (±17.0 SD) and was higher in specialised carp fisheries (40.0% ± 16.7 SD) than in put‐and‐take fisheries (15.9% ± 9.0 SD) and was not related to body size. For R. rutilus, angling bait consumption averaged 41.3% (±15.7 SD), did not differ significantly among fishery types, but increased with body size. The niche width of C. carpio was six times larger in specialised carp fisheries than in lakes without angling. For R. rutilus, niche width was two times larger in specialised carp and put‐and‐take fisheries compared to lakes without angling and specialised roach fisheries. These results indicate that angling bait subsidies represent a novel and substantial resource opportunity for fishes in angling lakes, with trophic consequences for the targeted species through increase of their stable isotope niche size. These impacts are partly influenced by the type of angling baits used by anglers and the characteristics of the fisheries, suggesting the need for improved quantification of the temporal dynamics of this type of subsidy to better understand its consequences on freshwater fish and recipient ecosystems.

On the survival and habitat use of hatchery-reared cisco (Coregonus artedi) in Lake Erie

Cisco (Coregonus artedi) have been extirpated from Lake Erie in North America since the 1960s, but they once supported one of the largest Laurentian Great Lakes fisheries. Numerous potential impediments to rehabilitation have been identified, including summer habitat refugia and predation. We used acoustic telemetry to investigate the thermal habitat use and survival of hatchery-reared adult cisco in Lake Erie. Fish were experimentally released (n = 50 per site) offshore at Dunkirk, New York, in the eastern basin and Huron, Ohio, in the central basin. Cisco in both basins found suitable summer oxythermal habitat in the metalimnion, suggesting that coldwater habitat availability is likely not an impediment for reestablishment. However, track end dates or predation dates were distributed across only four months with the last detection at 155 days. Predation sensors combined with temperature values during digestion indicated different potential predators: lake trout (Salvelinus namaycush) for the Dunkirk group and walleye (Sander vitreus) for the Huron group. Additionally, digestion temperatures of two tags indicated bird predation was also important, likely underestimated and suggested substantial use of the epilimnion by tagged fish. The results highlight the need for additional studies to address stocking optimization questions in support of future reintroduction experiments and related cisco conservation efforts.

Estimating fish production in wetlands

Fish production integrates changes in biomass from growth, reproduction, and mortality, and is a useful indicator for fisheries management. However, calculation of fish production has been limited by the intensive requirements for data on abundance, biomass, age structure, and vital rates, and so it is uncommon to find estimates of fish production for wetlands. We developed an approach to directly estimate production that is suitable for data-limited systems: a continuous time model of production describing individual growth over short time intervals with continuous time models of abundance and biomass over longer timescales. We applied this model for 18 Great Lakes coastal wetlands (GLCWs) on Lake Ontario, including Big Island Wetland (BIW). In BIW, most species were dominated in abundance and biomass by younger cohorts and, as a result, these young, fast-growing individuals contributed disproportionately to fish production. In total, BIW produced 336.1 kg·ha·year of fish and the other 17 neighbouring ranged between 447.7 and 1119.9 kg·ha·year. These are some of the first estimates of fish production for GLCWs, highlighting their value for managing Great Lakes fisheries.

Adfluvial migration and passage of Steelhead before and after dam removal at a major Great Lakes tributary

Despite the importance of Great Lakes fisheries and the increasing popularity of dam removal as a method to restore river connectivity and increase fish passage, the adfluvial migration of Steelhead (Oncorhynchus mykiss) has been drastically understudied and only relatively few published studies have examined the impacts of dam removal on fish movement and timing. To help fill these knowledge gaps, spawning migrations of Great Lakes adfluvial Steelhead tagged in spring and fall were monitored for two years before and three years after removal of a dam that partially blocked upstream movement for 100 years. Removal of the dam not only reduced downstream delay and increased passage at the site of the dam removal itself, but increased travel speeds and increased passage at remaining upstream dams for both spring and fall run fish, underscoring the cumulative impact of successive dam passage on fish migration. Fall fish were most impacted by the dam removal and were able to pass not only the dam footprint, but, for the first time, were also able to pass both remaining upstream dams, allowing them to overwinter at locations closer to known spawning areas. For these fish, delay at the footprint was reduced from the order of 100+ days to < 1 hour and the number of days passage occurred compared to the number of days fish were present and blocked increased from 2% to 82%. The benefits of dam removal should ultimately equate to increases in fish production, as more critical habitat becomes reconnected and more fish are able to pass dams and arrive at spawning beds. The observation that fish are likely able to remain in better condition and retain more energy for continued migration and reproduction warrants further study.

Great Lakes fisheries vessels and uncrewed surface vessels: A publicly available dataset

For decades, fish abundance surveys have been performed by large, crewed fisheries vessels using echosounders or trawling. However, the estimates obtained by these traditional methods may be biased due to the propagated noise generated by these vessels. A three-year collaborative effort has been conducted to measure the radiated acoustic signature of 17 fisheries vessels operating across all five of the Great Lakes under several operating conditions. This was done using a mobile ship noise measurement system developed specifically for this purpose. Additionally, with the recent advent of uncrewed surface vessels (USVs, “Saildrone”), an alternative “quiet” method of performing these abundance surveys is now possible. A detailed acoustic characterization was conducted for a USV to provide a comparison between traditional “loud” fisheries vessels and these “quiet” surface vessels. This talk will detail the acoustic signatures of all 18 vessels, compare the “loud” and “quiet” vessels, and provide a detailed description of the vessel measurement profiles which are now available as a public dataset. This dataset includes the time domain acoustic measurements, sound speed profiles, and GPS tracks of the measured vessels.

Adaptation through knowledge coexistence: insights for environmental and sea lamprey stewardship

ABSTRACT Strategies for tackling environmental issues, including the consequences of invasive species and corresponding control efforts, are frequently approached through a Western scientific lens that often overlooks Indigenous rights and Indigenous knowledge systems. This can cause numerous issues from costly delays in implementing control programmes, overlooking vital ecosystem information and alternative options, legal action due to infringement on rights, and perpetuating systems of oppression. This research uses social science and Indigenous methodologies to understand the Denny’s Dam rehabilitation (DDR) as a case study for relationship-building and knowledge coexistence between the Saugeen Ojibway Nation and the Great Lakes Fisheries Commission in controlling sea lamprey (Petromyzon marinus), an invasive species in the Laurentian Great Lakes. To evaluate the successes and shortcomings of the project, virtual semi-structured interviews (n = 14) were conducted with key decision-makers and others involved in the rehabilitation of Denny’s Dam, a sea lamprey barrier. Analysis of these interviews identify four main factors that were crucial in the success of the DDR partnership: meaningful communication, funding and capacity, going beyond duty to consult requirements, and early engagement. The DDR shows how knowledge coexistence approaches, including Two-Eyed Seeing, can lead to equitable decision-making, foster collaboration, and contribute to addressing challenges like climate change, invasive species, and various environmental degradation.

Concurrent warming and browning eliminate cold-water fish habitat in many temperate lakes

Cold-water species in temperate lakes face two simultaneous climate-driven ecosystem changes: warming and browning of their waters. Browning refers to reduced transparency arising from increased dissolved organic carbon (DOC), which absorbs solar energy near the surface. It is unclear whether the net effect is mitigation or amplification of climate warming impacts on suitable oxythermal habitat (<20 °C, >5 mgO/L) for cold-loving species because browning expands the vertical distribution of both cool water and oxygen depletion. We analyzed long-term trends and high-frequency sensor data from browning lakes in New York's Adirondack region to assess the contemporary status of summertime habitat for lacustrine brook trout. Across two decades, surface temperatures increased twice as fast and bottom dissolved oxygen declined >180% faster than average trends for temperate lakes. We identify four lake categories based on oxythermal habitat metrics: constrained, squeezed, overheated, and buffered. In most of our study lakes, trout face either seasonal loss (7 of 15) or dramatic restriction (12 to 21% of the water column; 5 of 15) of suitable habitat. These sobering statistics reflect rapid upward expansion of oxygen depletion in lakes with moderate or high DOC relative to compression of heat penetration. Only in very clear lakes has browning potentially mitigated climate warming. Applying our findings to extensive survey data suggests that decades of browning have reduced oxythermal refugia in most Adirondack lakes. We conclude that joint warming and browning may preclude self-sustaining cold-water fisheries in many temperate lakes; hence, oxythermal categorization is essential to guide triage strategies and management interventions.

Multimetric socio‐ecological assessment of water hyacinth (Eichhornia crassipes (Mart) solms) invasion of an urban Ramsar wetland lake

AbstractWater hyacinth (Eichhornia crassipes (Mart) solms), a widely distributed invasive aquatic plant in Sri Lanka, has invaded the Diyawannawa wetland lake located in Colombo city, which is the first Ramsar wetland city in South Asia. The present study was conducted to assess the water quality parameters that influence the distribution of water hyacinth and to identify the environmental, economic, and social consequences of its invasion of the Diyawannawa wetland. Five sampling sites were selected from the Diyawannawa lake, and the water pH, temperature, conductivity, total dissolved solids (TDS), salinity, dissolved oxygen concentration (DO), nitrate concentration, and total phosphorus concentration were measured at monthly intervals in the rainy and dry seasons of 2020. The abundance of water hyacinth was recorded at each site at each sampling event. Interviews and focus group discussions (FGDs) were conducted with the representatives of the community associated with the wetland to assess the ecological, economic and social effects of water hyacinth invasion. Principal component analysis of the water quality parameters revealed that phosphorus and nitrate concentrations in water significantly influenced the abundance of water hyacinth. Further, the water quality index (WQI) indicated poor water quality in the sites invaded by water hyacinth. The interviews and FGDs revealed that water hyacinth invasion has adversely affected the lake's fisheries and navigation pathways and increased the frequency of flooding, resulting in an increased mosquito population. The results of the present study highlighted the importance of implementing water quality management programmes in the Diyawannawa wetland to control the invasion of water hyacinth. Further, we recommend increasing community participation in water hyacinth control programmes and providing opportunities for the community to engage in self‐employment activities associated with the uses of water hyacinth.

Biomass and sustainable yields of Eurasian perch (Perca fluviatilis) in small boreal lakes with respect to lake properties and water quality

Understanding of factors that explain variation in potential fisheries yields is essential for the ecosystem-based management of lake fisheries. We used mark-recapture and Nordic survey net sampling to obtain estimates of Eurasian perch (Perca fluviatilis) abundance in 28 small (13.3 ha ± 11.4 ha, mean ± S.D.) boreal lakes. A size-structured population model was calibrated for each lake using further individual data to derive estimates of potential yields. Principal component scores formed from physical and chemical environmental parameters and a simple score reflecting the relative photic area of the lakes were then used to explain variation in theoretical yields to identify potential environmental proxies for fisheries management purposes. The estimated mean biomass of perch in the study lakes was 52.4 ± 51.2 kg ha−1, and the maximum sustainable yield, obtained with environment-dependent recruitment size was estimated to be 9.4 ± 12.1 kg ha−1 yr−1. The estimated yields were highest in shallow lakes with good oxygen saturation and with high percentage of euphotic bottom while excess nutrients decreased yields and alkalinity was marginally predictive for catch of large individuals. Our study provides quantitative estimates of potential yields of varyingly sized perch and helps to develop environmentally informed management for small lakes of which some are surprisingly productive.

Spatial Density, Biomass, and Composition of Crustacean Zooplankton on Lake Michigan Beaches

Ecosystem alterations to Lake Michigan (LM), such as the invasion of dreissenid mussels, have decreased the abundance of phytoplankton and, subsequently, zooplankton, which has implications for Great Lake fisheries. The community composition of zooplankton has also been altered over the past 20 years in LM, shifting the summer dominance from cladoceran to calanoid taxa. However, most of our information on zooplankton community dynamics is from deeper pelagic zones. The nearshore beach (≤1 m) habitat, which serves as a critical nursery for some larvae and juvenile fish, is composed of different zooplankton taxa than deeper zones, but limited data are available for comparison. We conducted a standardized summer sampling campaign to characterize the zooplankton community across 32 beaches in LM. We found the lowest crustacean zooplankton density and biomass on northern LM beaches and a higher zooplankton density and biomass on Greater Green Bay and central LM beaches, which had warmer water temperatures. Smaller-bodied cladocera (mainly Bosmina) and cyclopoid taxa were the most abundant groups on beaches. Our results provide the first comprehensive characterization of zooplankton on beaches in the Great Lakes, with applications for other lake systems. These results may help identify potential “hot spots” of fish recruitment for management.

Comparisons of Walleye Fecundity Before, During, and After Rehabilitation of the Red Lakes Fishery

Abstract The Red Lakes, Minnesota supported a substantial Walleye Sander vitreus fishery from the early to mid-20th century but experienced a major crash in the late 1990s. The population has since rebounded after a successful interagency recovery program and now supports valuable commercial and recreational fisheries. The variation in population densities associated with the collapse and subsequent recovery in the Red Lakes Walleye population provides a rare opportunity to study potential changes in relative fecundity (eggs/kg of body mass) under varying rates of exploitation: overexploited (1989 data), recovering (2004 data), and recovered (2017 data). We collected female Walleye in spring of 1989 (n = 30) from the Blackduck and Tamarac rivers and in spring of 2004 (n = 30) and 2017 (n = 30) from the Tamarac River. Results indicate that relative fecundity was significantly lower in 2017 (50,768, SD = 10,266) than in 1989 (58,216, SD = 6,211) and 2004 (61,964, SD = 7,472). We hypothesize that differences in relative fecundity among fishery states were due to differences in Walleye population abundances caused by varying exploitation rates in the years leading up to fecundity estimates.