Spring Water Levels Research Articles

Hydrodynamic Characterization of Mugla Karst Aquifer Using Correlation and Spectral Analyses on the Rainfall and Springs Water-Level Time Series

Karst aquifers have been an important research topic for hydrologists for years. Due to their high storage capacity, karst aquifers are an important source of water for the environment. On the other hand, it is safety-critical because of its role in floods. Mugla Karst Aquifer (SW, Turkey) is the only major water-bearing formation in the close environs of Mugla city. Flooding in the wet season occurs every year in the recharge plains. The aquifer discharges by the seaside springs in the Akyaka district which is the main touristic point of interest in the area. Non-porous irregular internal structures make the karsts more difficult to study. Therefore, many different methodologies have been developed over the years. In this study, unit hydrograph analysis, correlation and spectral analyses were applied on the rainfall and spring water-level time series data. Although advanced karst formations can be seen on the surface like the sinkholes, it has been revealed that the interior structure is not highly karstified. 100–130 days of regulation time was found. This shows that the Mugla Karst has quite inertial behavior. Yet, the storage of the aquifer system is quite high, and the late infiltration effect caused by alluvium plains was detected. This characterization of the hydrodynamic properties of the Mugla karst system represents an important step to consider the rational exploitation of its water resources in the near future.

A systematic survey of bar-built estuaries along the California coast

Of California's 577 coastal confluences, 278 of these are characterized as bar-built estuaries or coastal river mouth lagoons. Development during the 20th century has led to varying and often extreme levels of alteration to these estuarine systems. Changes to the natural timing and magnitude of riverine flows and modification of the mouth have affected the frequency and depth of marsh plain flooding, as well as the timing of breaching events. This project used standard assessment techniques to document and quantify the current environmental condition of 32 bar-built estuaries of various sizes, distributed throughout California. Estuary lagoon filling/flushing patterns (documented using pressure/temperature loggers) were found to fluctuate most in spring (due to bar closure with continued fluvial discharge) and late fall (due to high wave overtopping events). These spring and fall water level increases led to marsh plain flooding. Marshes were flooded for periods ranging from 9 to 65 days. Sites that supported long summer ponding periods increased hydraulic connectivity with side channels and back water environments and were characterized as having optimal habitat condition using the California Rapid Assessment Method. Bar-built estuaries with lower condition were found to have higher abundance of agriculture and impervious surface within their watersheds. The lowest condition sites had more than 65% impervious surface within the 2 km radius around the bar-built estuary. Also, bar-built estuary systems where bar management occurred (periodic or permanent) were found to have a lower habitat condition and support fewer native plant species. Summer salinity exceeded 25 within portions of thirteen of the 32 estuaries and all but three systems had water within portions of the main channel with salinity below 5. Our findings suggest that water elevations, dissolved oxygen concentrations, salinity and temperature vary widely within bar-built estuaries and thus, management decisions should account for this variability to ensure support for a diversity of endemic species.

Impact of seasonal water-level fluctuations on autumn vegetation in Poyang Lake wetland, China

Water level fluctuations (WLF) are natural patterns that are necessary for the survival of various plants, and WLF guarantee both the productivity and the biodiversity of wetlands. However, the underlying mechanisms of how changes in vegetation are linked to seasonal WLF remain unclear. Using vegetation and hydrological data from 1989 to 2009, we identified the key seasonal fluctuations and their impacts on vegetation in the Poyang Lake wetland by utilizing a tree-based hierarchical model. According to our results: 1) WLF in summer had significant impacts on both sedges and reeds. The severe summer floods promoted the expansion of sedges, while they inhibited the expansion of reeds; 2) WLF in autumn also greatly impacted sedges, while reeds were severely affected in spring. Specifically, we found that low water levels in autumn led to the expansion of sedges, and low water levels in spring led to the expansion of reeds. The results were well corroborated through comparisons of the vegetation distribution patterns over the last two decades (i.e., the 1990s and 2000s), which may shed light on corresponding water resource and wetland management.

Sustainable karst groundwater management in a semiarid region: the case of Su Gologone spring (Sardinia, Italy)

The Su Gologone karst spring has been recently investigated to assess how the karst aquifer would react in possible different meteorological conditions. The aim of the project is to develop a flexible and appropriate approach for its karst groundwater exploitation both taking into account the special features of the Supramonte karstlandscape and without affecting the quality and quantity of the resource.For this purpose, the spring water level was continuously measured while flow rates measurements were performed monthly. From 1-year monitored, a high discharge variance and an impulsive behaviour to recharge input was detected indicating the presence of a transmissive drainage network with high hydraulic conductivity. The storage capacity associated to the low-conductive fracture system is still unknown. On the basis of these results, a new setup of the pumping facility together with a flexible management of water withdrawal is proposed, allowing the adaptation of the quantity of exploited groundwater depending on the hydro-meteorological conditions.

Spatial-temporal variability of the fluctuation of water level in Poyang Lake basin, China

Abstract Poyang Lake basin is one of the most biodiversity areas in China. Fluctuation of water level is an important factor of hydrological process which is a guarantee of ecosystem health and biodiversity conservation. To measure its spatial-temporal variation, classical statistical methods and permutation entropy were employed: 1) Variation of water level downstream of Poyang Lake during one year follows a periodical pattern, while it is random in upper reaches. That is, the range of water level in upper reaches is much less than that in downstream. 2) Fluctuation of water level in winter and spring is more complicated, more irregular and more random than that in other seasons. This is because in winter and spring, precipitation directly causes rising in water level rather than generating surface runoff, while it is reversed in summer. 3) The ranges, standard deviation, coefficient of variation and fluctuation of water level decrease with rising in elevation. 4) In sub-basin scale, fluctuation of water level in upper reaches is more complicated than that in downstream, e specially along one river. Mechanically, catchment size and confluence process may be the main factors influencing fluctuation of water level over Poyang Lake basin.

Role of waves and tides on depth of closure and potential for headland bypassing

Depth of closure is a fundamental concept used to define the seaward extent of a morphodynamically active shoreface at a particular temporal scale. The estimation of this limit in relation to the depth in front of the bounding headlands along embayed coastlines allows questioning whether embayments, often deemed closed sediment cells, experience more headland bypassing than expected. Wave-based parameterisations developed for microtidal beaches are most widely used to estimate closure depth; however, a re-evaluation of the concept for shorefaces influenced by geological control (presence of headlands and/or bedrock) and strong tidal currents is appropriate. Here, we use the macrotidal, embayed and high-energy coastline of SW England to identify the ‘active’ nearshore limits with a multi-method approach that includes observations of shoreface morphology and sedimentology, offshore/inshore wave formulations and bed shear stress computations. We identify the basal limit of ‘significant’ (i.e., 0.14 m) morphological change (Depth of Closure; DoC) and a maximum depth of extreme bed activity and sediment transport (Depth of Transport; DoT). Observations of DoC correspond closely to the values predicted by existing formulations based on inshore wave conditions (10–15 m for the study area; relative to mean low water spring water level in this case). The computed DoT, represented by the upper-plane bed transition attained under extreme conditions, exceeds 30 m depth in the study area. The significant implication is that, even though many headlands appear sufficiently prominent to suggest a closed boundary between adjacent embayments, significant wave- and tide-driven sediment transport is likely to occur beyond the headland base during extreme events, especially at low water levels. The maximum depth for significant sediment transport (DoT) was computed across a broad wave-current parameter space, further highlighting that tidal currents can increase this closure depth estimate by ~10 m along macrotidal coastlines, representing a 30% increase compared to tideless settings. This work illustrates the importance of tidal currents in depth of closure calculations and challenges the notion that embayed beaches are generally closed cells, as headland bypassing may be more wide spread than commonly assumed along exposed coastlines globally.

Analysis of groundwater variation in the Jinci Spring area, Shanxi Province (China), under the influence of human activity.

Jinci Spring is one of the most famous karst spring in Northern China and is the main drinking and irrigation water source of Taiyuan city, Shanxi Province. It has special significance in terms of humanities and water resources. Because of the continuous over-exploitation of groundwater, the water level of groundwater has been decreased significantly. The flow of Jinci Spring has decreased year by year since the 1970s, and in 1994 it cut off completely. The flow cutoff has brought huge losses to the local economy and negatively impacted the ecological environment. From the hydrogeological conditions of Jinci Spring area to study, the dynamic change in karst groundwater level will provide a basis for the protection and rational exploitation of karst water in the spring area. The previous research on Jinci Spring area was limited to the spring flow and water level changes, lack of analysis to the overall spring area and the decay process of spring flow. This paper takes the overall spring area as research object. According to groundwater level data over 1961-2012, the period is divided into two phases of decline and recovery. Human activities in the region and corresponding groundwater evolution at various stages were systematically analyzed, and the reservoir capacity was calculated for each period of decline. The results show that the average reservoir capacity decreased from 920 (1954-1960) to 116 (1961-1977) to 31 (1978-1994) million m3. The important effect of "Water Resumption" project on groundwater in the area during the remediation period was also analyzed. In the light of observed increases in groundwater level during this stage, the project has a notably positive effect.

A Dynamic Study of a Karst Spring Based on Wavelet Analysis and the Mann-Kendall Trend Test

Over the last 40 years, declining spring water flow rates have become a typical feature of karst springs in Northern China. Wavelet analysis, the Mann-Kendall trend test and the mutation test were used to analyze dynamic monitoring data of groundwater levels and atmospheric precipitation in the Jinan karst spring area, from 1956 to 2013, to study hydrological responses to atmospheric precipitation over one-year periods. Results from this analysis show that: (1) Atmospheric precipitation and the spring water level displayed multi-scale change characteristics, having two very similar cycles of change of 16 and 12 years. This finding shows that atmospheric precipitation generates a direct impact on the level of spring water. (2) From 1956 to 2013, the groundwater level in the Jinan spring area had a significant downward trend (0.65 m/10a). Precipitation recorded an increasing trend (12.65 mm/10a), however this was not significant. The weight of the influencing factors of the spring dynamic therefore changed due to the influence of human factors. (3) A mutation of atmospheric precipitation occurred in 1999, after which annual precipitation increased. Results for the mutation of the groundwater level showed an initial change in 1967. After this change the water level continued to decrease before rapidly increasing after 2004. The future trend of the spring water level should be maintained with consistent precipitation (having an upward trend), indicating that atmospheric precipitation is not the only factor affecting the dynamics of the spring. (4) Different periods were identified on the multiple regression model. The main influencing factors on groundwater level over the past 58 years were identified as a transition from precipitation to artificial mining. These results also validate the suitability and reliability of using wavelet analysis and the Mann-Kendall test method to study groundwater dynamics; these results provide a reference for the future protection of the Jinan City spring.

A comparison of the effects of water-level policies on the availability of walleye spawning habitat in a boreal reservoir

ABSTRACTPapenfuss JT, Cross T, Venturelli PA. 2018. A comparison of the effects of water-level policies on the availability of walleye spawning habitat in a boreal reservoir. Lake Reserv Manage. 34:321–333.Water levels in reservoirs can affect the quantity and quality of the habitat that is available for spawning fish and their eggs. We studied how a change in the water-level management policy (“rule curve”) in 2000 affected the availability of walleye (Sander vitreus) spawning habitat in 3 lakes (Kabetogama, Namakan, and Sand Point) that make up a large, boreal reservoir between Canada and the United States. According to observed water-level data, available spawning habitat on known Lake Kabetogama spawning sites increased 95% (P < 0.01) with the 2000 rule curve, but did not change on Namakan or Sand Point lake spawning sites. However, when using modeled water-level data to control for confounding weather events, habitat availability at known spawning sites increased significantly (P < 0.01) on all 3 lakes (179%, 92%, and 93%, respectively). Habitat availability improved because the 2000 rule curve increased mean spring water levels by 0.5 m, and water levels rose more slowly (2.2 vs. 3.0 cm/d) during egg incubation. Our findings suggest that, although water-level management on large reservoirs can be a challenge, carefully designed policies can improve walleye spawning habitat conditions and help to achieve fisheries management goals.

Three Gorges Dam: polynomial regression modeling of water level and the density of schistosome-transmitting snails Oncomelania hupensis

BackgroundSchistosomiasis remains a major public health concern in China. Oncomelania hupensis (O. hupensis) is the sole intermediate host of Schistosoma japonicum, and its change in distribution and density influences the endemic S. japonicum. The Three Gorges Dam (TGD) has substantially changed the downstream water levels of the dam. This study investigated the quantitative relationship between flooding duration and the density of the snail population.MethodsTwo bottomlands without any control measures for snails were selected in Yueyang City, Hunan Province. Data for the density of the snail population and water level in both spring and autumn were collected for the period 2009–2015. Polynomial regression analysis was applied to explore the relationship between flooding duration and the density of the snail population.ResultsData showed a convex relationship between spring snail density and flooding duration of the previous year (adjusted R2, aR2 = 0.61). The spring snail density remained low when the flooding duration was fewer than 50 days in the previous year, was the highest when the flooding duration was 123 days, and decreased thereafter. There was a similar convex relationship between autumn snail density and flooding duration of the current year (aR2 = 0.77). The snail density was low when the flooding duration was fewer than 50 days and was the highest when the flooding duration was 139 days.ConclusionsThere was a convex relationship between flooding duration and the spring or autumn snail density. The snail density was the highest when flooding lasted about four to 5 months.

Impact of groundwater regimes on water balance components of a site with a shallow water table

AbstractThe management of shallow water table sites is often the subject of discussion between different interest groups, the most controversial topic being the different target groundwater levels. A good level of knowledge about the effects of the different water levels on the water budget components is a precondition for the development of compromises in well‐balanced water resource management.We used groundwater lysimeters to investigate the impact of different water level regimes on the water balance. The lysimeters were installed directly within a typical shallow water table site and had a specially designed system to control the lower boundary condition. This enabled us to simulate different management options in a realistic way.Our results show increasing evapotranspiration with higher water levels but only if the vegetation is adapted to these conditions. Adaptation may take place within a few years of higher water levels. High water levels in spring are linked to increased water storage. This can help to compensate for the higher evapotranspiration for some weeks but not for the entire season. The meteorological conditions have a large short‐term impact on the water budget, which is difficult to compensate for using long‐term water management strategies or slow‐responding vegetation development. Our results underline the complex ecohydrological dependencies in such site conditions and could be an important basis for the development or improvement of ecohydrological models.

Hydrological evidence and causes of seasonal low water levels in a large river-lake system: Poyang Lake, China

Seasonal variations in local catchments and connected rivers lead to complex hydrological behaviours in river-lake systems. Poyang Lake is a seasonally dynamic lake with frequent low levels in spring and autumn, which may be triggered by the local catchment and Yangtze River. Based on two typical years, a hydrodynamic model combined with long term hydrological observations was applied to quantify the spatiotemporal impacts of the local catchment and Yangtze River on spring and autumn low water levels in Poyang Lake. As a first attempt, this study explored the spatial differences of the two influences. Simulation results showed that the contributions of the catchment and the Yangtze River were approximately 70% and 30% in spring 1963, and 5% and 95% in autumn 2006, respectively. The area of catchment influence was mainly distributed in channels and southern floodplains, with relatively uniform water levels. The area impacted by the Yangtze River mainly spanned from the northern portion of the waterway to the central lake, with strong spatial variability. This study focused on two typical years; however, the results can be extended to explain common hydrological phenomena and improve future strategies of water resource management in this river-lake system.

Study on Prediction Model of Karstic Large Spring Water Level Dynamic Coupling Multiple Factors in Jinan

In karst regions, due to the heterogeneous features of karst medium, the characteristics of the groundwater flow turn to be of high complexity. Researchers have been seeking proper forecasting methods for karst water dynamic for many years. This paper, taking the spring in Jinan as an example, using regression analysis, analyzed the factors influencing spring water dynamic, and quantitatively evaluated the influencing coefficients of spring water level concerning rainfall, exploitation and recharge as well as the natural decay coefficient of spring water in dry seasons. The prediction model coupling multiple factors was built by investigating natural and anthropogenic factors influencing groundwater level, which could be used for forecasting dynamic of spring water in Jinan. The calculated value of model was highly coincided with the observed value. In consideration of the characteristics of uneven precipitation in Jinan, the suitable zones and volume of artificial recharge were investigated finally, which could help to sustain the spewing of Jinan springs significantly.

Implications of spring water levels on the production of American white pelicans nesting at marsh lake, Minnesota

ABSTRACTWe investigated the relationship between spring water levels and production of American white pelicans (Pelecanus erythrorhynchos) nesting colonially at Marsh Lake in southwest Minnesota during 2003–2012. We obtained estimates of pelican nest and chick numbers from aerial photographs to determine population levels. We used historical streamflow data to characterize April water conditions, a period when nest‐site selection typically occurs. Pelicans used 4 islands and 1 peninsula for nesting, ranging from relatively high‐elevation sites connected to or near the mainland to more distant low‐elevation sites in the middle of the lake. The number and proportion of nests on high‐elevation sites are positively related to discharge in the Upper Minnesota River during April. In years when high water inundates low‐elevation sites during pelican nest‐site selection, pelican nests were located on the high‐elevation locations near or connected to the mainland. Over 90% of the variation in the number of nests on high‐elevation sites is related to the mean daily discharge in the Upper Minnesota River during April. In addition, the proportion of nests on high‐elevation sites also increases as mean daily discharge during April increases. However, chick production was negatively related to discharge during April. More than 84% of the variation in the number of near‐fledged chicks produced per nest was related to mean daily discharge during April. Although high‐elevation sites in close proximity to the mainland offered nesting pelicans refuge from high water levels, they also expose American white pelican nests to greater predator risk. Nest camera monitoring indicated that high‐elevation sites exhibited significantly higher predator activity than low‐elevation sites, and experienced lower nest success (i.e., probability that at least 1 egg from the nest hatched). Proposed changes in the management of Marsh Lake call for the installation of a water control structure at the Marsh Lake dam that will allow for active management of lake levels. Our study provides managers with models for predicting impacts of water levels on American white pelican production. © 2015 The Wildlife Society.

Effects of Lake Surface Elevation on Shoreline‐Spawning Lost River Suckers

AbstractWe analyzed remote detection data from PIT‐tagged Lost River Suckers Deltistes luxatus at four shoreline spawning areas in Upper Klamath Lake, Oregon, to determine whether spawning of this endangered species was affected by low water levels. Our investigation was motivated by the observation that the surface elevation of the lake during the 2010 spawning season was the lowest in 38 years. Irrigation withdrawals in 2009 that were not replenished by subsequent winter–spring inflows caused a reduction in available shoreline spawning habitat in 2010. We compared metrics of skipped spawning, movement among spawning areas, and spawning duration across 8 years (2006–2013) that had contrasting spring water levels. Some aspects of sucker spawning were similar in all years, including few individuals straying from the shoreline areas to spawning locations in lake tributaries and consistent effects of increasing water temperatures on the accumulation of fish at the spawning areas. During the extreme low water year of 2010, 14% fewer female and 8% fewer male suckers joined the shoreline spawning aggregation than in the other years. Both males and females visited fewer spawning areas within Upper Klamath Lake in 2010 than in other years, and the median duration at spawning areas in 2010 was at least 36% shorter for females and 20% shorter for males relative to other years. Given the imperiled status of the species and the declining abundance of the population in Upper Klamath Lake, any reduction in spawning success and egg production could negatively impact recovery efforts. Our results indicate that lake surface elevations above 1,262.3–1,262.5 m would be unlikely to limit the number of spawning fish and overall egg production.Received May 16, 2014; accepted January 29, 2015

Identification of a robust Lake Sturgeon (Acipenser fulvescens Rafinesque, 1917) population in Goulais Bay, Lake Superior

Summary Lake Sturgeon (Acipenser fulvescens Rafinesque, 1917) in Lake Superior are greatly depressed from their historic abundance, and few populations meet the rehabilitation goals identified by management agencies. A netting program targeting juvenile Lake Sturgeon (ages 3–15) was implemented from 2010 to 2012 in Goulais Bay, a shallow, productive bay in the south-eastern part of the lake, to determine abundance, distribution, population characteristics (size structure, condition, age structure, mortality and growth), and recruitment patterns. Five-hundred and thirty-one individuals were captured over the 3-year study, resulting in a mark-recapture estimate of 4977 (95% CIs 3295–7517) juveniles. Catch rates in this study were higher than in any other location in Lake Superior, with sturgeon being broadly distributed around the bay. Estimated annual survival rate ranged from 0.691 to 0.858, depending on the method used. The majority of fish captured were between 620 and 800 mm in total length and were between 4 and 10 years of age (range 1–29 years). Recruiting year-classes were apparent every year, with no apparent effects due to lampricide treatments (a suspected threat to age-0 Lake Sturgeon) in the Goulais River. Year-class strength was positively related to spring water levels. It is possible that this robust Goulais Bay population could help re-populate the south-eastern part of Lake Superior, which contains a number of large, productive embayment areas that formerly supported large Lake Sturgeon populations.

Temporal Variability of Monthly Daily Extreme Water Levels in the St. Lawrence River at the Sorel Station from 1912 to 2010

Although climate models predict that the impacts of climate change on the temporal variability of water levels in the St. Lawrence River will be seasonally-dependent, such a seasonal effect on the current variability of extreme water levels has never been analyzed. To address this, we analyzed the temporal variability of three hydrological variables (monthly daily maximums and minimums, as well as their ratio) of water levels in the St. Lawrence River measured at the Sorel station since 1912, as they relate to climate indices. As for stationarity, the shifts in the mean values of maximum and minimum water levels revealed by the Lombard method took place prior to 1970 for spring water levels, but after that year, for winter water levels. Changes in the winter stationarity are thought to mainly relate to the decreasing snowfall observed in the St. Lawrence River watershed after 1970. In contrast, for spring, these changes are likely primarily related to human activity (digging of the St. Lawrence Seaway and construction of dams). Two shifts in the mean values of fall minimum extreme water levels were highlighted. The first of these shifts, which occurred in the first half of the 1960s decade, can also be linked to human activity (digging of the St. Lawrence Seaway and construction of dams), whereas the second shift, observed after the 1970s for the months of November and December, can be linked to decreasing amounts of snow in winter. AMO (Atlantic Multidecadal Oscillation) is the climate index that is most frequently correlated negatively with the hydrologic variables, mainly in winter and spring.

Multiscale Habitat Selection of Wetland Birds in the Northern Gulf Coast

The spatial scale of habitat selection has become a prominent concept in ecology, but has received less attention in coastal ecology. In coastal marshes, broad-scale marsh types are defined by vegetation composition over thousands of hectares, water-level management is applied over hundreds of hectares, and fine-scale habitat is depicted by tens of meters. Individually, these scales are known to affect wetland fauna, but studies have not examined all three spatial scales simultaneously. We investigated wetland bird habitat selection at the three scales and compared single- and multiscale models. From 2009 to 2011, we surveyed marsh birds (i.e., Rallidae, bitterns, grebes), shorebirds, and wading birds in fresh and intermediate (oligohaline) coastal marsh in Louisiana and Texas, USA. Within each year, six repeated surveys of wintering, resident, and migratory breeding birds were conducted at >100 points (n = 304). The results revealed fine-scale factors, primarily water depth, were consistently better predictors than marsh type or management. However, 10 of 11 species had improved models with the three scales combined. Birds with a linear association with water depth were, correspondingly, most abundant with deeper fresh marsh and permanently impounded water. Conversely, intermediate marsh had a greater abundance of shallow water species, such as king rail Rallus elegans, least bittern Ixobrychus exilis, and sora Porzana carolina. These birds had quadratic relationships with water depth or no relationship. Overall, coastal birds were influenced by multiple scales corresponding with hydrological characteristics. The effects suggest the timing of drawdowns and interannual variability in spring water levels can greatly affect wetland bird abundance.

Economic Values and Regional Economic Impacts of Recreational Fisheries in Mississippi Reservoirs

AbstractThis study estimated the economic benefit of recreational fisheries on two trophy crappie Pomoxis spp. fisheries in Mississippi. We accomplished this by estimating economic impacts of angler expenditures and angler willingness‐to‐pay for fishing trips above current expenditures. Anglers spent 91,811 activity days on Sardis Reservoir in 2006 and 46,036 on Grenada Reservoir in 2007. The total economic impacts to the state were estimated at US$5.83 million on Sardis Reservoir and $2.15 million on Grenada Reservoir, supporting 75 and 51 full‐ and part‐time jobs, respectively. Total consumer surplus was $5.57 million and $4.46 million on Sardis and Grenada reservoirs, respectively. Last, we used a model that predicted the effect of average spring water levels on total angling effort to estimate resulting changes in economic benefits. Spring angling effort and associated economic benefits peaked at intermediate water levels and declined at both low and high water levels. Future changes in precipitation patterns in the southeastern United States may require altering reservoir guide curves to maximize economic benefits associated with reservoir fisheries.Received June 25, 2012; accepted October 3, 2012

Exploring the Influence of Stock–Recruitment Relationships and Environmental Variables on Black Bass and Crappie Recruitment Dynamics in Missouri Reservoirs

AbstractLarge reservoirs provide important sport fisheries, but managing these fisheries is difficult because of the multiple biological and environmental variables that interact to shape them. Understanding how sport fish recruitment responds to parental stock and environmental influences would improve our management capabilities. We compiled long‐term datasets for 15 Missouri reservoirs and used them to examine the influence of parental stock abundance and a suite of environmental variables on the recruitment of Largemouth Bass Micropterus salmoides, Spotted Bass M. punctulatus, White Crappie Pomoxis annularis, and Black Crappie P. nigromaculatus. Comparisons of log‐linear, Ricker, and Beverton–Holt stock–recruit models revealed that the log‐linear model was the most parsimonious for Largemouth Bass, White Crappie, and Black Crappie, but the Ricker model was best for Spotted Bass. However, stock–recruit models alone explained less than 13% of the variation in Largemouth Bass, Spotted Bass, and White Crappie recruitment while explaining about 33% of the variability in recruitment of Black Crappie. Largemouth Bass recruitment was positively related to spring rises in water levels, summer water levels, and average summer air temperatures, whereas Spotted Bass recruitment was positively related to spring air temperatures. White Crappie recruitment was positively related to total phosphorus levels and drops in spring water levels. Black Crappie recruitment was best explained by the model positively relating recruitment to spawning stock abundance, spring water levels, and summer water levels, while negatively relating recruitment to rapid drops in spring water levels. With the exception of models for Black Crappie, the best models did not include spawning stock abundance, and environmental variables appeared more important in explaining variation in recruitment. However, environmental variables in these models explained only a modest amount of variation (27–44%) in recruitment, revealing the complexity of recruitment processes in large reservoirs.