Catch Trends Research Articles

Resurgence of Cisco (Coregonus artedi) in Lake Michigan

In recent decades, many factors that were linked with the decline of Great Lakes cisco (Coregonus artedi) populations have subsided. The goal of this study was to investigate where cisco exist in Lake Michigan and evaluate evidence for recovery including when, where, and to what extent it is occurring. We evaluated datasets from several independent monitoring efforts that did and did not target cisco. We also evaluated trends in commercial and recreational catches of cisco. Across these datasets, there was strong evidence of a sustained recovery of cisco stocks that began in Lake Michigan in the mid-2000s. Fall gill net surveys and commercial fisheries provided reasonable indications of a population recovery in the northeast by 2011. Further south, Ludington Pump Storage barrier net monitoring also recorded increasing numbers of cisco starting in 2011. Recreational harvest estimates were valuable in evaluating spatial distributions but were less valuable as an early signal of abundance shifts. Measures of the recreational harvest of cisco most notably increased in 2014. The highest catch rates and harvest occurred in Grand Traverse Bay and northern Lake Michigan as evidenced by recreational, commercial, and fall netting surveys. Observations of cisco are expanding and have increased in intensity along the eastern shore of Lake Michigan south to Muskegon in both fishery dependent and independent surveys. The similarity in trends from all data sources indicate that cisco abundance has increased, and their range within the basin continues to expand.

Long-Term Data Suggest Potential Interactions of Introduced Walleye and Smallmouth Bass on Native Sauger in Four Missouri River Impoundments

Abstract Sauger Sander canadensis, Walleye Sander vitreus, and Smallmouth Bass Micropterus dolomieu, are important sportfish in the four main stem Missouri River reservoirs in South Dakota: Lakes Oahe, Sharpe, Francis Case, and Lewis and Clark. However, native Sauger populations, once assumed to be stable, may be in decline. To identify temporal trends and potential interspecific mechanisms affecting Sauger populations, we examined their long-term abundance trends in standard gillnet surveys and angler catch and harvest trends in long-term creel surveys. We also used a robust design occupancy model to examine changes in within-lake distribution of this species. There are concerns regarding the effects of Walleye and Smallmouth Bass on Sauger, so we also described the population trends of these potential competitors. Standard gillnet surveys indicated declining abundance of both Sauger and Walleye in Lakes Oahe and Sharpe. Sauger abundance has trended down in Lewis and Clark, but upward in Francis Case. Conversely, Walleye abundance trends declined in Francis Case and increased in Lewis and Clark. Occupancy (ψ̂) of Sauger declined in all four reservoirs, indicating a contracting distribution throughout the reservoirs. Walleye occupancy remained ∼1.0. Smallmouth Bass occupancy increased in the three reservoirs with sufficient data for analysis, excluding Lewis and Clark Lake. Smallmouth Bass exhibited steady increases in angler catch and harvest, as well as abundance in long-term gillnet surveys, suggesting expanding and increasing populations. Habitat alteration is hypothesized to be a major driver of the Sauger occupancy and abundance declines. However, Walleye and Smallmouth Bass interactions could also be contributing to observed declines of native Sauger.

Influence of seasonality, salinity and temperature on catch trend of Penaeus indicus H. Milne-Edwards, 1837 in a coastal lagoon, India

The catch pattern of P. indicus in coastal lagoons is influenced by seasonal changes in physicochemical parameters of the lagoon ecosystem. In this study the effects of seasonality, salinity and water emperature of lagoon on P. indicus catch were analysed using Structural Time Series Model (STSM) and ARIMAX (Auto Regressive Integrated Moving Average with explanatory variables) modeling approach using monthly time series catch, salinity and water temperature data of the Chilika Lagoon (a Ramsar site) in India for the period from 2001 to 2015. Results showed a significant (p<0.05) increasing stochastic upward trend and two seasonal cycles for P. indicus catch in the lagoon. Salinity was found to have significant positive influence (p<0.05) and temperature to have insignificant positive influence on P. indicus catch in the lagoon.

Community-level effects of spatial management in the California drift gillnet Fishery

Fisheries management interventions that protect certain species by redistributing fishing effort may generate unintended consequences for other species. In the California drift gillnet fishery for swordfish and sharks, a large spatial closure was implemented in 2001 to protect endangered leatherback turtles, which limited fishing effort to the Southern California Bight. Leatherback bycatch has since decreased, but the effects on other species have not been comprehensively examined. Here, we explore the effects of this closure on the community catch composition in the fishery and find that other protected species may have benefited, while catch per unit effort of major target species increased or was not significantly affected over the long term. However, a time-series analysis reveals that changes in catch trends across twenty species began at least five years before the closure was implemented, suggesting that previous regulatory measures or other drivers may also contribute to these trends. These results highlight the importance of comprehensive approaches that include the historical context when evaluating management outcomes.

Spatial stock assessment methods: A viewpoint on current issues and assumptions

Spatial stock assessments have been developed to address violations of the dynamic pool assumption that the region to be assessed contains a single homogeneous stock. The possibility of such violation is often evident in data that suggest different trends in abundance or catch / survey age- / size-structure among areas that cannot be explained simply by the fishing history among areas. Currently, most stock assessments account for spatial structure using the ‘areas-as-fleets’ approach in which fishery or survey selectivity and catchability are assumed to differ spatially. However, several simulation studies suggest that adopting spatial approaches to stock assessment will improve estimation performance compared to the areas-as-fleets approach or ignoring spatial structure when conducting stock assessments, although at the cost of a larger number of estimable parameters. Spatial approaches to stock assessment and the provision of management advice have been available since the 1950s. However, spatial stock assessments only became adopted for management purposes in the 1990s, with the widespread adoption of the “integrated approach” to stock assessment, which allowed the use of multiple data sets for parameter estimation. The number of spatial stock assessments is now increasing rapidly. This paper outlines some of the key decisions that need to be made when conducting a spatial stock assessment (number of areas, how to model recruitment, movement, growth and dispersal, and model parameterization).

An overview of small-scale fisheries in the Northern Portuguese coast

An overview of small-scale fisheries in the Northern Portuguese coast

Comparing self-reported incidental catch among fishermen targeting Pacific halibut and a fishery independent survey

This paper compares observations of commercial fishermen with a fishery-independent survey, and explores putative relationships between characteristics of fishing operations and incidental catch in the Pacific halibut fishery in Southeast Alaska. Results from a multiple factor analysis demonstrate statistically significant relationships between fishing characteristics and the incidental catch of various species. Results from a proportional odds logistic regression model indicate the presence of a strong unavoidable component of incidental catch in the halibut fishery. Consequently, patterns of incidental catch in this fishery generally paralleled patterns of incidental catch in a fishery-independent stock assessment survey that uses similar gear. This suggests that increased onboard monitoring of this fleet by cameras or human observers is unlikely to reveal broad trends in incidental catch that are not already apparent in the fishery-independent stock assessment survey. Nevertheless, weaker statistically significant relationships in the model indicate that incidental catch may be influenced by observable and controllable characteristics of fishing operations (e.g., fishing grounds, season, vessel length, gear configuration). This suggests a proportional odds model like the one presented in this paper could be used to generate operation-specific estimates of incidental catch by species from incidental catches observed in fishery-independent surveys based on known characteristics of fishing operations.

Effects of assets and weather on small-scale coastal fishers’ access to space, catches and profits

Fishers’ spatial behavior affects their incomes, livelihoods and ecological sustainability and is affected by establishment of protected areas, and the impacts of changing climate and weather patterns. An understanding of fishers’ spatial behavior is essential for evaluating catch trends or estimating per-area yeilds. Location choice by fishers has largely been understood through foraging models and empirical studies in large scale, developed country fisheries. This paper uses participatory mapping, logbooks and remotely sensed weather (wind speed) data to explore the influence of weather and capital on the spatial behavior and success of coastal Kenyan small-scale fishers. We test generalized foraging models of fisher behavior. A reef crest separates available fishing grounds in the study area between two distinct areas of dissimilar fish catches. Over half of the fishing trips accessed grounds outside the reef, particularly in the calmer northeast monsoon season. Trips across the reef were more successful both in terms of catch and value per fisher and price per kg. Access across the reef was determined primarily by season but was also affected by métier and daily wind speeds. Amongst a sample of non-motorised trips, crossing the reef was the most important variable for predicting Value Per Unit Effort (VPUE). Other things equal, more productive grounds ought to attract more effort, but access to the fishing grounds beyond the reef is constrained by fishers’ access to capital, fluctuations in weather and the interaction between these variables. Fishers with low levels of capital are more affected by daily weather that limits access to the more profitable fishing grounds. Fishers with more capital are able to access more productive grounds more freely, but at the expense of extra compensation for the capital needed. Thus while gross returns to offshore trips exceed similar returns for nearshore trips, net returns are likely to be more equal. In our study a stark exception to the pattern of higher returns from more capitalised gear is the relatively high VPUE achieved by spear fishers, making the assumption of free movement of labour between gears not valid. The study also adds a temporal complexity to this picture by showing the likelihood of accessing grounds beyond the reef crest varies temporally by season.

Assessment of Fisheries and Management in Rihand Reservoir, Uttar Pradesh

The study assesses the present status of fisheries in Rihand reservoir in relation to past status in terms of fish species diversity, trophic metrics of fish community, trends in fish catch and the physico-chemical properties of the waterbody. Species-wise monthly catch data collected from annual fish catch records ofDepartment of Fisheries, Rihand office helped the analyse present status. Shannon-Wiener Index showed an appreciable decline in species diversity between 1971-72 (H=2.94) and 2015-16 (H=2.59). There was significant loss in species richness during the same period as it has declined from 40 species, 28 genera and 11 families (1971-72)to 22 species,16 genera and 8 families (2015-16). Seasonally, the species diversity was found to be at its peak during monsoon season (H=2.2), coinciding with favourable conditions such as sufficient water and ample food resources. Species richness was at its best in the month of May-June while species evenness (J=0.85) was highest in post monsoon indicating an evenly distributed and rich fauna in the monsoon and post monsoon periods. The review of literature on water quality status indicated the reservoir is meso-eutrophic in nature. The trophic metrics analysis has shown that the water body is dominated by herbivores, detritivores and omnivores (72.3%) followed by mid-level carnivores (26.7%) indicating gaps at the top level predators. The total fish catch of the reservoir has increased marginally from 152 tons in 1971 to 262 tons in 2016. The corresponding unit catch was 5.06 kg/ha/year and 8.68 kg/ha/year respectively, which is still very low. The CAGR of fish landings for the recent period (2000-01 to 2015-16) was found to be a modest 1.8% with several inter-year fluctuations. Given the conducive aquatic environment and moderate productivity levels of the reservoir, fish catch can be increased significantly only through sustained stocking program alongside effective governance.

Agreeing with FAO: Comments on SOFIA 2018

The last three bi-annual State of World Fisheries and Aquaculture (SOFIA) reports by the Food and Agriculture Organization of the United Nations (FAO) gave the impression that they downplayed the stark reality of declining trends in global marine fisheries catches. In contrast, the most recent SOFIA 2018 deserves praise for seemingly striking a different tone, and for more directly and clearly identifying the key issues faced by marine fisheries. This includes the acknowledgment of globally declining catches and several data deficiencies, such as the ‘presentist’ bias in official data reported by countries to FAO, and the utility of catch data reconstructions in informing such data deficiencies, as advocated by the Sea Around Us for nearly two decades. FAO also acknowledges its personnel limitations and hence the need to collaborate with non-governmental entities. Further, we congratulate FAO on explicitly addressing in SOFIA 2018 two major challenges in global marine fisheries, namely the effects of climate change and the problems related to subsidies for the enormous Chinese fishing fleets. We applaud FAO for this different, more open tone in SOFIA 2018, which even includes animal welfare consideration, and we hope that it signals a new period of increased FAO engagement with Civil Society and academia, to address the important fisheries and sustainability challenges facing our world.

Wild lobster (Panulirus ornatus) fry fishery in Balete bay, Davao Oriental: Catch trends and implications to fisheries management

The coastal ecosystem of the Philippines is one of the richest and most diverse on earth. Lobsters are one of the commercially exploited species targeted by small-scale fishers for their livelihood and income. This study aims to determine the catch, and catching pattern of the wild lobster fry fishery, quantify the catch per unit effort (CPUE) and identify issues and challenges present in the lobster fry fishery for improved conservation and management. A combination of semi-structured interviews (n = 90), focus group discussion (n = 35) and actual catch monitoring for three months of lobster fry fishers (n = 20) were conducted to elicit information on lobster catch, composition, fishing practices and issues and challenges. Results from the interview and focus groups showed that majority of fishers catch the fries of Panulirus ornatus, Parribacus antarcticus and Panulirus versicolor. They catch most of the lobster fries using bamboo traps and beach seine. The analysis of the CPUE also revealed significant results (P ≤ 0.05) with the good catch having the highest CPUE value (0.30 g) followed by the normal catch (0.16 g) and worst catch of (0.02 g). In terms of weekly field monitoring of the catches of 20 fishers, temporal variation in terms of weeks was highly significant (P = 0.000; R2 = 22). Some management issues mentioned by fishers include effluents from shrimp farming, illegal fishing, chemical residues from mango farms and improper waste disposal. The lack of a management plan, as well as a system to control who has access to the fishing ground of lobster fries, can negatively affect the long-term sustainability of the lobster fry fishery.

Future of Fishing for a Vulnerable Atoll: Trends in Catch and Catch-Per-Unit-Effort in Tokelau’s Domestic Marine Fisheries 1950–2016

Tokelau is among the most vulnerable countries to climate change from both an environmental and economic perspective, whilst being highly dependent on marine resources for dietary nutrition. Industrial as well as small-scale fisheries are present in Tokelau’s waters, with Tokelau itself only participating in small-scale fisheries. Industrial fisheries consist exclusively of foreign distant-water tuna fleets. This study aims to reconstruct and investigate the trends in the domestic small-scale marine fisheries catches, fishing effort, and catch-per-unit-effort (CPUE) from 1950 to 2016. We used kWdays as our metric of fishing effort or fishing capacity, estimated using length, motorization and type of fishing vessels. Total fishing effort was approximately 11,900 kWdays in 1950 and increased rapidly after the 1980s with the introduction of larger motorized vessels. Despite evolving fishing effort, catches taken in subsistence fisheries have been relatively consistent at approximately 370 t⋅year −1 , resulting in a reduction of subsistence CPUE from 32.4 kg⋅kWdays −1 in 1950 to 2.6 kg⋅kWdays −1 in 2016. This trend is opposite to that of the artisanal fishery, where CPUE increased since the start of this fishery in 2003, from 1.7 kg⋅kWdays −1 to 2.6 kg⋅kWdays −1 in 2016. Tokelau’s domestic catch is greatly underreported, with reconstructed domestic catch since 2010 being nearly four times larger than the data reported by the Food and Agriculture Organization (FAO) of the United Nations on behalf of Tokelau. The abundance of reef fishes are predicted to decrease while the abundance of pelagic fishes is expected to increase within Tokelau’s waters due to climate change, likely further altering future fishing practices. The present CPUE analysis, combined with the forecasted effects of climate change, suggests that the domestic fisheries in Tokelau may be on an unsustainable path, highlighting food security concerns, despite the potential for growth in offshore fisheries.

Assessing fishing impacts in a tropical reservoir through an ecosystem modeling approach

Ecological models are useful for evaluating fishery management scenarios, as they allow researchers to investigate alternative fishing effort, as well as varying environmental and trophic interaction scenarios. Through an ecosystem modeling approach (Ecopath with Ecosim), we addressed the possible impacts of small-scale fisheries on the structure and functioning of a tropical ecosystem (Itaipu Reservoir, Brazil). We found that fishing effects and predator–prey interactions were the main drivers explaining catch trends in the Itaipu Reservoir fisheries. The mean trophic level of catch did not change throughout the analyzed time period and no losses in secondary production from exploitation (L index) were observed, indicating that Itaipu fisheries are sustainable regarding ecosystem effects. The negative impacts of introduced species on native species seem to be greater than the fishing impacts. Fishing simulations from the ecosystem Maximum Sustainable Yield (MSY) reduced the biomass of some important species in the local fishery. Regarding management advice, our results indicate that fishing efforts should not be increased for curimba (Prochilodus lineatus), pintado (Pseudoplatystoma corruscans), and jau (Zungaro jahu). Additionally, participative management methods are important measures for local fisheries. Finally, additional research is needed to investigate how fishery management can promote the use of multispecific methods (e.g., gillnets) to control introduced species.

Interannual to decadal variability in the catches of small pelagic fishes from China Seas and its responses to climatic regime shifts

Small pelagic fishes such as sardine and anchovy play an important role in marine ecosystem and are affected largely by environmental changes because of their character as r-strategists and their low trophic levels. Small pelagic fishes are crucial targets of Chinese fisheries, accounting for 26% of the total catch in 2014. Their catches show an increasing trend since the 1950s. However, there is still little information on small pelagic species inhabiting Chinese waters. Catch trends and impacts of climatic regime shifts for six typical commercially important small pelagic species, chub mackerel (Scomber japonicus), Japanese scad (Decapterus maruadsi), Pacific herring (Clupea pallasi), Japanese anchovy (Engraulis japonicus), Japanese sardine (Sardinops melanostictus) and horse mackerel (Trachurus japonicus), are analyzed using Chinese Fishery Statistics, FAO data, climatic indices and sea surface temperature (SST) data. The aim is to explore the interannual to decadal variability of their catches in China Seas and their responses to climatic regime shifts. Decadal variability is evident in the catches of the six small pelagic fishes with different variation patterns between warm- and cold-water species. Step changes in catches of the six species were observed in 1976/77, 1986/87, 1995/96, 2001/02 and 2005/06, while regime shifts in climatic/SST indices occurred around 1976/77, the late 1980s and the mid-1990s. This indicates that decadal variations in small pelagic fishes respond strongly to the climatic regime shifts, and the different response patterns of warm- and cold-water species reflect their different life strategies. Marine thermal variation patterns during the period 1981–2000 were well explained by different phase changes in the SSTs between summer and winter and were consistent with the step change in the catches of small pelagic fishes. The double-integration hypothesis, which indicates that cumulative integrations of atmospheric forcing can generate marine population responses, is useful both to understand the process from climate forcing to fish and the controlling mechanism of climate variability on small pelagic fishes in China Seas.

Variability of coastal cephalopods in overexploited China Seas under climate change with implications on fisheries management

Cephalopods (squids, cuttlefish and octopus) have increased globally over the past decades, which may be attributed to their strong phenotypic plasticity, allowing them to adapt quickly to a changing ocean environment. The global proliferation of cephalopods may yield important ecosystem effects worldwide. However, information on cephalopods variability in Chinese waters is still scant. Coastal cephalopods, in spite of chronic overexploitation, form a vital component of the catch composition in China Seas. In this paper, we review the status and trends of coastal cephalopods in China Seas and explore their responses to environmental variability. We focus on four commercially-important coastal cephalopod species, including golden cuttlefish (Sepia esculenta Hoyle), Japanese loligo squid (Loligo japonica Steenstrup), common Chinese cuttlefish (Sepiella maindroni de Rochebrune) and swordtip squid (Uroteuthis edulis Hoyle). Even though spatial distributions of these four species partially overlap, their differing life history strategies with respect to factors such as growth, distribution, migration, and spawning patterns, have led to differing population responses to environmental variability. As a result, an overall increasing trend in cephalopod production has been apparent since the 1990s, accompanied by major changes in species composition. Catch trends of the four species show either decadal patterns of significant decline or increase in the late 1980s to mid-1990s. Statistical analysis indicates different responses to environmental warming, with Japanese loligo squid and swordtip squid seeming to benefit from warmer environment while golden cuttlefish and common Chinese cuttlefish seeming to respond negatively. Our study has allowed us to explore the impacts of environmental changes on Chinese coastal cephalopods in the overexploited ecosystems of the China Seas and to conclude that fluctuations of coastal cephalopods are mainly driven by large scale environmental variations associated with climate change and/or marine ecosystem regime shifts.

Status of fisheries in 13 Asian Large Marine Ecosystems

Thirteen Asian Large Marine Ecosystems (LMEs) ranging from the Arabian Sea LME in the West to the Western Bering Sea LME in the East are reported on in terms of their fisheries, catch trends and associated indicators such as the primary production required to maintain fishery catches, trends in the mean trophic levels of the catch, stock-status plots and others. Effective management of these LMEs is crucial for maintaining marine ecosystem system health and the goods and services the LMEs provide. Such management must be able to rely on credible catch data. The catch data used here were based on the national catch reconstructions performed by the Sea Around Us, as also documented in www.searoundus.org, but these could not fully compensate for the deficiencies of the fisheries statistical systems of several major countries in Asia, as reflected in exaggerated catch levels and uninformative catch compositions.

Population Structure and Reproductive Biology of Selected Sciaenid Species along the Fishing Grounds of Goa, West Coast of India

The present hypothesis on reproductive migration pattern between two species of sciaenids is based on the data collected with the help of the single-day commercial trawl with a fishing effort of 181 h along the fishing grounds of Goa, west coast of India. The observations on abundance revealed that between the two species ( Johnius borneensis and Otolithes ruber ) that formed bulk of the catch, a significant inverse trend in catch was observed. The pattern of migration based on the examination of female gonadal status suggested J. borneensis to be a continuous spawner and was evidenced by continuous occurrence of gravid and spent females and their juveniles. On the other hand, the rare occurrences of gravid females of O. ruber from the study area suggest that the species spawns away from the coast or might migrate to some potential spawning grounds. Further, an assessment of fecundity and the ova distribution pattern propounded higher fecundity in O. ruber compared to J. borneensis with multiple spawning in both the species.

Evaluating an empirical harvest control rule for the Torres Strait Panulirus ornatus tropical rock lobster fishery

The Torres Strait tropical rock lobster, Panulirus ornatus (Fabricius, 1798), fishery is a culturally and economically important fishery. The Australian Commonwealth has an obligation under the Torres Strait Treaty to protect the traditional way of life and livelihood of Traditional Inhabitants, as well as promote employment opportunities for them. Management of the fishery is complicated by the high natural recruitment variability, and diving surveys have been used for the past 28 yrs to monitor changes in the size of the recruiting population. Here, we describe development of an empirical harvest control rule (eHCR) to achieve defined biological, economic and sociocultural objectives for the lobster fishery. A key principle is that fishery managers, fishers, and key stakeholders utilize pre–agreed upon and pretested rules to adjust management recommendations given updates of data. The performance of eHCR alternative candidates is evaluated using four alternative operating models, with 200 stochastic replicates each and 800 total simulations, accounting for observation error and implementation uncertainty. The eHCR adjusts recommended biological catches relative to a recent average, based predominantly on the logarithm of the slopes of recent trends in the preseason recruiting lobster, with lower weighting accorded to trends in recently-settled lobster and catch per unit effort (CPUE) from two fishing sectors. In addition, a maximum catch limit of 1000 t is set. The eHCR formula thus uses recent trends in survey and CPUE information to implement rapid, but precautionary, short- term adjustments needed to effectively manage a highly variable fishery.

Evidence of indiscriminate fishing effects in one of the world\u2019s largest inland fisheries

While human impacts like fishing have altered marine food web composition and body size, the status of the world’s important tropical inland fisheries remains largely unknown. Here, we look for signatures of human impacts on the indiscriminately fished Tonle Sap fish community that supports one of the world’s largest freshwater fisheries. By analyzing a 15-year time-series (2000–2015) of fish catches for 116 species obtained from an industrial-scale ‘Dai’ fishery, we find: (i) 78% of the species exhibited decreasing catches through time; (ii) downward trends in catches occurred primarily in medium to large-bodied species that tend to occupy high trophic levels; (iii) a relatively stable or increasing trend in catches of small-sized species, and; (iv) a decrease in the individual fish weights and lengths for several common species. Because total biomass of the catch has remained remarkably resilient over the last 15 years, the increase in catch of smaller species has compensated for declines in larger species. Our finding of sustained production but altered community composition is consistent with predictions from recent indiscriminate theory, and gives a warning signal to fisheries managers and conservationists that the species-rich Tonle Sap is being affected by heavy indiscriminate fishing pressure.

Long-Term Trends in Abundance and Size of Sport Fishes in the Flathead River, Montana, Following Changes in Hydroelectric Dam Operations

We studied long-term trends in catches per unit effort (CPUE; fish h-1) of four sport fish taxa in the Flathead River, Montana, following changes in hydroelectric operations at the Slis Ksanka Qisp Project (SKQP; formerly Kerr Dam). Prior to 1997 SKQP operations caused frequent, unnatural flow fluctuations. In 1997 the dam was changed from a power-peaking and load-following facility to a base-load facility. The new operations included seasonal minimum flows and ramping rates that greatly reduced flow fluctuations. Autumn trends in CPUEs of two size classes (substock and stock) of northern pike (Esox lucius), Oncorhynchus spp., brown trout (Salmo trutta), and smallmouth bass (Micropterus dolomieu) were monitored using nighttime electrofishing during 1984–86 before operational changes and again at the onset of operational changes in 1998 and continuing through 2008. We observed little difference in CPUEs between 1984–86 and 1998, the first year after changes, but we documented strong increasing trends in CPUEs of both sizes of all taxa, except stock northern pike, over the long term following operational changes. We also examined long-term patterns in the size structure (total length; TL mm) of fishes following operational changes. All taxa had either initial downward shifts in median TL, decreases in minimum sizes of fish captured, or both, a pattern consistent with enhanced recruitment and survival of smaller fishes. We conclude that modifications in dam operations were associated with increases of four sport fish taxa in the Flathead River and that similar normative flow applications might benefit riverine fish populations elsewhere.