Small Inland Lakes Research Articles

Significance of shallow seismic reflection (SSR) and ground penetrating radar (GPR) profiling on the Modern Coast line History of the Bedre area, Eğirdir Lake, Isparta, Turkey

Lake level changes and settlement places constitute the main problems in controlling the coastal environment along the Eğirdir Lake, SW Turkey. The Quaternary geology in the Bedre Coast was studied based on shallow seismic reflection (SSR) survey, ground penetrating radar (GPR) profiles, and the data derived from boreholes and investigations in the field. Thus, six seismic and five radar facies were determined respectively. The geological units from the basement rock to the Holocene deposits were imaged by the SSR technique. GPR technique is used for the shallower part, ranging from the ancient to the Modern lacustrin sediments. The Quaternary lake level changes, borehole, seismic and radar data indicate that a pond with a connected to the Lake around the Bedre area existed in the last century. Sand barriers, climate, topographical elevation and erosions of the basement rocks control the sedimentation of the back barrier of the coastal line. Marsh muddies and ancient beach sands are the main sediments of the pond area. From the profiles, ancient buried sand barriers were also seen in the lake side. In our view, as the previous lake level dropped from the highstand, the ancient sand barrier was formed which divided the lake and the pond and isolated a small inland lake which lies 4 m below the level of the coastal barrier. For agricultural purposes, artificial man-made constructions were done on the barrier and channels. Thus, dry agricultural land appeared in the last 50 years on the pond side.

Population growth and mass mortality of an estuarine fish, Acanthopagrus butcheri, unlawfully introduced into an inland lake

Abstract In 2006, two periods of hypoxia resulted in the death of approximately 35 tonnes of black bream (Acanthopagrus butcheri) in Lake Indoon, a small inland lake in Western Australia. Acanthopagrus butcheri was the first fish species to be recorded in this lake, along with the mosquitofish (Gambusia holbrooki) which was also observed during sampling in 2006. Acanthopagrus butcheri appears to have been introduced to Lake Indoon between 1998 and 2003 and formed a self‐sustaining population. It is believed to have been deliberately introduced for the purpose of creating a recreational fishery, despite the existence of substantial penalties for illegal translocation of fish in Western Australia. Recent human‐induced environmental changes, including rising groundwater and salinization, have probably aided the establishment of both species in Lake Indoon. The importance of salinity to recruitment success by A. butcheri was indicated by the presence of only two age classes in 2006, with estimated recruitment dates coinciding with the years of highest recorded salinity in the lake. The ‘fish kills’ provided an opportunity to examine aspects of A. butcheri biology in a relatively low salinity environment which is atypical for this estuarine species. In particular, the recruitment period in Lake Indoon was delayed until autumn/winter, rather than spring/summer as seen in other populations. Biological responses in Lake Indoon have implications for natural populations living in estuaries with modified salinity regimes. The ecological, social and economic impacts potentially arising from the introduction of fish to Lake Indoon, which is an important migratory bird habitat and a recreational amenity for local residents and tourists, illustrate the complexities of fish translocation and the need for rigorous assessment before stocking to identify potential costs and benefits. Copyright © 2008 John Wiley & Sons, Ltd.

Flexible diet and trophic position of dreissenid mussels as inferred from stable isotopes of carbon and nitrogen

In this study, the trophic position and food-web impacts of invading zebra mussels (Dreissena polymorpha) were investigated by sampling mussels, seston (= phytoplankton), macrophytes, zooplankton, and surficial sediment in two small inland lakes (1999–2002) and similarly in western Lake Erie (1999 only). Tissues from quagga mussels (Dreissena bugensis) from Lake Erie were also analyzed. Stable-isotope ratios (15N/14N and 13C/12C) were used to identify likely food sources and estimate relative trophic position. For Lake Erie, stable-isotope ratios indicated no diet differences between the two mussel species. For all lakes, zooplankton δ13C was indicative of phytoplanktivory. The 13C stable isotope ratios indicated that seston comprised ~50% of food sources for mussels in Lake Erie, but 73%–97% and 52%–100% of the diet of mussel populations in Lake Wawasee and Clark Lake, respectively. Stable nitrogen isotope ratios placed zooplankton at trophic levels equal to or higher than those of mussels in seven of eight comparisons. Dreissena polymorpha and D. bugensis are able to exploit suspended detritus as a significant energy source, as well as compete directly with zooplankton for seston as a food source and with each other in areas of sympatry.

Relationship Between Labile Dissolved Organic Carbon (LDOC), Bacterioplankton Cell Phosphorus Quota, and Bacterial Phosphate Uptake Rate in Lakes

We examined the effects of labile dissolved organic carbon (LDOC) on bacterial growth rate, biovolume, cell phosphorus quota (i.e., P content per cell) and velocity of phosphate uptake in laboratory cultures and in natural bacterioplankton assemblages. Pseudomonas fluorescens (ATCC 13525) was cultured in M9 minimal medium adjusted to have low phosphate concentrations (25–400 nM); glutamate was the sole C-source (50–200 μM). Growth was slowest, cell biovolume was lowest, and cell P-quota was highest in cultures with the least glutamate. Natural bacterial assemblages were examined in three small inland lakes and along a trophic gradient in Lake Erie, covering a wide range of trophic states from hypereutrophic Sandusky Bay to meso-oligotrophic Crystal Lake. Biologically available P ranged from 17 to 117 nM; labile dissolved organic carbon (LDOC) ranged from 15 to 170 μM. As LDOC increased, bacterioplankton growth rate and biovolume increased, but cell P-quota and phosphate uptake velocity decreased. Phosphate uptake exhibited Michaelis-Menten kinetics at all stations; K t significantly increased with increasing LDOC. Amendments of 100 μM glycolate, glutamate, or glucose to natural bacterial assemblages significantly decreased the V max of phosphate uptake. We propose that LDOC controls the metabolic status of bacterioplankton: above about 50 μM LDOC cells are in a Growth State with modest P-quotas and relatively low phosphate uptake rates; below 50 μM LDOC cells are in a Storage State with very high P-quotas and rapid phosphate uptake rates.

Planktonic Primary Production in the Offshore Waters of Dreissenid-infested Lake Erie in 1997

Phosphorus and chlorophyll a (Chl a) concentrations in 1997 decreased from the west basin, which receives most of the lake's nutrient loading, to the central and eastern basins. By contrast, average areal primary production varied little between basins, because higher Chl a concentrations in the west basin were offset by poorer light penetration. Sub-epilimnetic production in the deeper central and east basins, which might be favored by trends to greater water clarity over recent decades, was a minor contributor to total primary production. With additional data from the literature, it was shown that pre-dreissenid Lake Erie produced significantly less Chl a relative to total phosphorus (TP) than did other Great Lakes or smaller inland lakes. Chl a:TP ratios did not change significantly consequent to dreissenid colonization. Despite the continued low yield of Chl a, Lake Erie in post-dreissenid years had areal primary production relative to TP as high as other, dreissenid-free, Great Lake locations and much higher than comparably oligotrophic inland lakes. Absolute concentrations of TP and Chl a have decreased over the decades of nutrient controls and, in the west basin, in parallel with dreissenid colonization. The lake nonetheless remained highly efficient at translating TP into primary production up to 1997, revealing little or none of the depression associated with dreissenid impacts in shallower systems.

Influence of Near-surface Stratigraphy on Coastal Landslides at Sleeping Bear Dunes National Lakeshore, Lake Michigan, USA

Lake-level change and landslides are primary controls on the development of coastal environments along the coast of northeastern Lake Michigan. The late Quaternary geology of Sleeping Bear Dunes National Lakeshore was examined with high-resolution seismic reflection profiles, ground-penetrating radar (GPR), and boreholes. Based on sequence-stratigraphic principles, this study recognizes ten stratigraphic units and three major unconformities that were formed by late Pleistocene glaciation and postglacial lake-level changes. Locally high sediment supply, and reworking by two regressions and a transgression have produced a complex stratigraphy that is prone to episodic failure. In 1995, a large landslide deposited approximately 1 million m3 of sediment on the lake floor. The highly deformed landslide deposits, up to 18 m thick, extend 3–4 km offshore and unconformably overlie well-stratified glacial and lacustrine sediment. The landslide-prone bluff is underlain by channel-fill deposits that are oriented nearly perpendicular to the shoreline. The paleochannels are at least 10 m deep and 400 m wide and probably represent stream incision during a lake-level lowstand about 10.3 ka B.P. The channels filled with sediment during the subsequent transgression and lake-level highstand, which climaxed about 4.5 ka B.P. As lake level fell from the highstand, the formation of beach ridges and sand dunes sealed off the channel and isolated a small inland lake (Glen Lake), which lies 5 m above the level of Lake Michigan and may be a source of piped groundwater. Our hypothesis is that the paleochannels act as conduits for pore water flow, and thereby locally reduce soil strength and promote slope failure.

Development of a Fish-Based Index of Biotic Integrity for Small Inland Lakes in Central Minnesota

We developed a fish-based index of biotic integrity (IBI) for a set of Minnesota lakes having similar geophysical and chemical features. Fish data were collected by means of trap nets, gill nets, shoreline seines, and backpack electrofishing. Of 30 evaluated metrics, we identified 16 metrics of three types: species richness, community assemblage, and trophic composition. In contrast to lotic IBIs, where a single sampling gear is usually used, data from all four sampling gears were necessary for IBI development. We selected metrics based on responses to measures of human-induced stress based on watershed land use patterns and human population density. Species richness and community composition metrics describing intolerant or habitat specialist species were most sensitive to differences in human-induced stress. Because these species were found in the nearshore zone of lakes, effective sampling of the nearshore fish community was essential to the development and performance of the IBI. Trap-net- and gill-net-based metrics, however, were essential to the development of trophic composition metrics, the trap nets providing the best insectivore and omnivore metric and the gill nets providing the best top carnivore metrics. Lake IBI scores reflected differences in land use patterns, trophic state, and aquatic vegetation. Sensitivity analysis indicated that selected metrics contributed to IBI performance, but the relative contribution of individual metrics varied among human-induced stress categories. Additional work is needed to test the performance of this IBI on an independent group of lakes, to set the range of applicability, and to determine the effectiveness of the IBI as an assessment tool for lakes.

Application of otolith analyses to investigate broad size distributions of young yellow perch in temperate lakes

Otolith analyses were used to back‐calculate young‐of‐the‐year (YOY) yellow perch Perca flavescens hatch‐date estimates to interpret broad length distributions observed within a small Great Lake, Lake St. Clair, and a small inland lake, Lake Opinicon, during 1998. For the Great Lake, the earliest observed hatch date occurred 2 weeks after suitable water temperatures and latest hatch dates occurred the same week temperatures were considered too warm for spawning. For the inland lake, the earliest hatch date occurred 4 weeks after suitable water temperatures and the latest hatch dates occurred 2 weeks after the water temperatures were considered too warm for spawning. It is inferred that spawning in each lake had a duration of >9 weeks. This suggests that natural perch populations can protract their spawning season opportunistically under the appropriate environmental cues. During 1998, these cues involved a shortened winter, earlier spring, and slow warming to typical summer temperatures, caused by the El Niño‐Southern Oscillation. Time of YOY hatch determined the absolute opportunity for growth and resulted in a match or mismatch with optimal foraging conditions and contributed to the development of the observed YOY length distributions.

Population genetics of the zebra mussel, Dreissena polymorpha (Pallas): local allozyme differentiation within midwestern lakes and streams

Several aquatic invertebrates with free-swimming larvae have paradoxically demonstrated fine-scale genetic heterogeneity. In this study, we tested for genetic heterogeneity in an exotic freshwater bivalve, the zebra mussel, Dreissena polymorpha (Pallas), which like many marine molluscs has a free-swimming larval stage. Zebra mussels were collected from 22 sites in the Great Lakes and from a small inland lake complex in southwestern Michigan and scored for 13 allozyme loci. Sites were sampled in a hierarchical fashion to assess the spatial scale of genetic variation. Zebra mussel populations exhibited significant genetic heterogeneity on a local scale within lakes, even though populations remained homogenous on a larger regional scale between lakes or lake complexes. The allozyme loci that exhibited heterogeneity differed from lake to lake. Populations also displayed significant heterozygote deficiencies from Hardy-Weinberg expectations for a majority of loci, implying population subdivision and (or) inbreeding on a fine scale. Our results suggest that local genetic differentiation for zebra mussels is both spatially and temporally fluid and is the product of stochastic processes, such as spawning asynchrony and uneven mixing of larval cohorts, rather than natural selection.

Population genetics of the zebra mussel, <i>Dreissena polymorpha</i> (Pallas): local allozyme differentiation within midwestern lakes and streams

Several aquatic invertebrates with free-swimming larvae have paradoxically demonstrated fine-scale genetic heterogeneity. In this study, we tested for genetic heterogeneity in an exotic freshwater bivalve, the zebra mussel, Dreissena polymorpha (Pallas), which like many marine molluscs has a free-swimming larval stage. Zebra mussels were collected from 22 sites in the Great Lakes and from a small inland lake complex in southwestern Michigan and scored for 13 allozyme loci. Sites were sampled in a hierarchical fashion to assess the spatial scale of genetic variation. Zebra mussel populations exhibited significant genetic heterogeneity on a local scale within lakes, even though populations remained homogenous on a larger regional scale between lakes or lake complexes. The allozyme loci that exhibited heterogeneity differed from lake to lake. Populations also displayed significant heterozygote deficiencies from Hardy-Weinberg expectations for a majority of loci, implying population subdivision and (or) inbreeding on a fine scale. Our results suggest that local genetic differentiation for zebra mussels is both spatially and temporally fluid and is the product of stochastic processes, such as spawning asynchrony and uneven mixing of larval cohorts, rather than natural selection.

Development of Cost‐effective Geothermal Probes for Use in Shallow Seas and Lakes: Measurements in Lake Travis, Central Texas

Instruments for acquiring geothermal data underwater have been available for a few decades. But, most of them are designed for measurements in very deep water. They are not particularly cost‐effective for operations in shallow seas and lakes. The equipment is quite heavy, weighing one ton or more. A large ship with a high‐powered winch is required for its deployment. It cannot be used in small inland lakes where there is no access to such a ship. In this study, we develop a new type of geothermal instrumentation that is specifically designed for shallow‐water operations and has significant advantages over the previous ones in terms of cost and logistics. The new instrument is of much simpler mechanical and electrical designs. It weighs only and can be deployed from a small boat. It free‐falls through the water column and penetrates to the bottom sediments by its momentum and transmits the data back through an electrical cable. We have tested this instrument successfully in Lake Travis in central Texas and obtained 3 sets of geothermal measurements over a one‐year period. Analyzing these data with additional information on the bottom water temperature history, we obtain constraints to the background geothermal heat flow of the lake and the heat budget of the bottom sediments.

Rapid Biological Assessments: How Many Animals Are Enough?

Rapid bioassessment data using counts of benthic macroinvertebrates from the littoral zones of 5 lakes in south-central Ontario were examined to determine if subsamples of 100 animals provided sufficient statistical power to distinguish these lakes. One-way analysis of variance and power analysis were completed using 17 biological indices based on counts of 100, 200, and 300 animals. Despite the common perception that more is better, the doubled or tripled effort required to sort, identify, and enumerate more animals resulted in very little improvement in our ability to distinguish lakes. Eight of the 17 indices were of limited value for separating the 5 lakes. High correlations, indicating redundancies among the best indices, suggested that 1 or 2 metrics would be sufficient to characterize the lakes. Three indices including % amphipods, % insects, and a multivariate metric representing the 1st axis from a correspondence analysis ordination were the best metrics for separating the 5 lakes. A variant of the commonly used EPT index, composed of the total number of individuals of Ephemeroptera, Plecoptera, and Trichoptera, was also useful for characterizing the lakes. From this comparative analysis, subsamples based on counts of 100 animals are sufficient to distinguish the littoral benthic communities of small inland lakes in south-central Ontario.

Abstract: Development of Cost-effective Geothermal Probes for Use in Offshore Exploration and Environmental Work

ABSTRACT Geothermal measurements are important in various aspects of offshore oil and gas exploration. For example, hydrocarbon maturation is largely controlled by the thermal history of the sediments (Lerche, 1992), and the measurement of the heat flow through the seafloor is probably the most important direct information available to deduce the thermal history, and to infer a hydrocarbon maturation history. Underwater heat flow probing has been recognized as an effective method in detecting oil and gas seeps (Anderson, et al., 1991) and in investigating the sub-salt structures in the Gulf of Mexico (Nagihara, et al., 1992). Geothermal measurements are also important in understanding the heat budget in estuaries and lakes. Although geothermal data are useful in many aspects, their acquisition tends to be costly and time consuming. The probes previously available for underwater measurements were mainly designed for operations in very deep (> 1000 m) water (Hyndman, et al., 1979; Jemsek, et al., 1985; Nagihara, et al., 1996). The equipment is quite heavy (one ton), and its deployment requires a Figure 1. Subbottom sediment temperature profiles of Lake Travis, Texas, obtained during the two instrument tests in 1997. End_Page 561------------------------ large ship equipped with a heavy-duty winch and good station-keeping capability for which operational costs are high. These requirements preclude collecting data making measurements in small inland lakes where there is no means of transporting and deploying such heavy gear. In this study, we have developed a new type of geothermal probe that has significant logistical and economical advantages over the previous ones for deployment in shallow (< 500 m) seas and lakes. The new probe utilizes a thin (2.54-cm or 1-inch diameter), long (~7 m) steel tube which contains a number of thermistors. It can be easily transported and deployed from a very small (i.e., inexpensive) ship with a small number of people because it weighs less than 50 kg. Once deployed, the probe free-falls through the water column and, with its momentum, penetrates into the sediments. In the current design, the probe transmits the temperature data to the surface through a thin electrical-mechanical cable. A maximum of 12 thermistors can be placed inside the metal tube. The internal electronics yields temperature resolutions of 2 to 3 millidegrees-K. Because of its simple design, the new probe costs much less to build and operate than the previous probes. We tested the new geothermal probe successfully in Lake Travis, Texas, in early June and mid-August of 1997 (Fig. 1). It was deployed in the deepest (~55 m) part of the lake and recorded temperature profiles down to 3 m subbottom. The penetration was limited because the soft sediment cover of the man-made lake was thin. On each penetration, the probe was left in the bottom for about 45 minutes during which each thermistor was logged every 2 seconds. The equilibrium temperature at each sensor was determined by the extrapolation method previously established by Bullard (1954). The two sets of geothermal records show the warming trend of the lake bottom water from the spring to summer. Detailed history of the temperature change, heat input from the surface and the greater depth are currently analyzed using mathematical modeling of the heat conduction process.

FUNDUDZI, A UNIQUE, SACRED AND UNKNOWN SOUTH AFRICAN LAKE

Summary Lake Fundudzi is a unique, small inland lake in the north eastern region of South Africa, formed by a landslide. The considerable sedimentation of its basin indicates an age in the order of 10 000s of years. It forms the focus of a rich heritage of ceremonial rituals and myths amongst the local Vhavenda population, but has not enjoyed the protection it deserves and serious impacts have been made by human transformation of the catchment, over-utilization of natural resources, forestry, water abstraction and degradation of the rivers. Additionally, the present fish community is not natural as all larger fish species seem to have been introduced. Some limnological information on this lake has been sporadically collected over a period of 60 years. It indicates conductivities ranging between 2,8 −18,8 μ S m−1 neutral to acid waters and oxygen stratification near the bottom during winter. Zooplankton was characterised by small copepods and rotifers. The lake is presently threatened by an increased anthr...

The effect of light on Lake Herring (coregonus artedi) reactive volume

The lake herring (Coregonus artedi) is an important coldwater planktivore in the Laurentian Great Lakes and in smaller inland lakes in portions of Canada and the northern United States. Lake herring cruise the pelagia and feed selectively in both gulping and particulate modes. They are visual predators in environments with adequate illumination. Visual predation by fish consists of a series of discrete steps. We studied the first step in the predation sequence, reaction to prey, at light intensities of 2–1500 Lx in a simulated pelagic environment at 10–13°C. We measured lake herring reactive distances, the distance at which a prey item will be detected and attacked, to live Limnocalanus macrurus, a natural prey of lake herring in Lake Superior. We used the reactive distances and associated angles of bearing and elevation, which described the location of the prey relative to the lake herring, to calculate reactive volume. This reactive volume can be envisioned as an irregular sphere surrounding the fish, within which prey are detected and attacked. All of the attacks on prey occurred in the anterior portions of the sagittal and lateral planes of the lake herring, as would be expected for a pelagic, cruising fish. The reactive volume surrounding the lake herring was generally spherical, but was more irregular than the simple spheres, hemispheres, cylinders, cones or other geometries assumed in previous studies. The reactive distances and the reactive volume changed with light intensity and were significantly smaller at 2–10 Lx than at 40–1500 Lx. At 40–1500 Lx, the reactive volume was expanded over that observed at 2–10 Lx laterally and caudally. Collectively our results indicate that lake herring can visually forage most effectively in environments with light levels >10 Lx.

A Comparison of Photosynthate Allocation in Lakes

We compared the relationships between photosynthate allocation to protein, carbohydrate, lipid and low molecular weight (LMW) fractions and the variables daylength and water temperature in Lakes Huron, Michigan, and Ontario as well as three smaller headwater lakes in the Lake Ontario drainage. In all lakes investigated the allocation of recently produced photosynthate to carbohydrate was strongly related to daylength (% carbohydrate = −3.5 * daylength (hr) + 72.8; n = 59, r 2 = 0.56). The percentage of photosynthate allocated to protein was a function of water temperature in all lakes although the y-intercept for the protein-temperature relationship was much lower in the three headwater lakes and Lake Ontario (% protein = 0.50 * temperature (°C) + 6.1; n = 37, r 2 = 0.52) than in Lake Huron and Lake Michigan (% protein = 0.68 * temperature (°C) + 24.2; n = 23, r 2 = 0.49). The increase in allocation to protein was related to a decrease in allocation to low molecular weight material (% LMW = −1.1 * % protein + 57.13; n = 60, r 2 = 0.72). The percentages of photosynthate in lipid and LMW material were not related to any of the environmental variables measured. Assuming that photosynthate allocation is related to biochemical composition, the phytoplankton in Lakes Huron and Michigan were more protein rich for a given temperature than those in Lake Ontario and in the smaller inland lakes. The protein deficit was due to an increase in allocation to LMW material.

Introduction of Lake Trout (Salvelinus namaycush) to Inland Lakes of Ontario, Canada: Factors Contributing to Successful Colonization

We evaluated the success of 183 introductions of lake trout (Salvelinus namaycush) in small inland lakes in Ontario, Canada. Our purpose was to identify variables associated with successful versus failed natural recruitment after introductions of hatchery-reared lake trout. Origin of donor stocks, angling regulations, geophysical and water quality characteristics, and fish species presence-absence of the recipient lakes were evaluated as possible factors contributing to colonization success. Origin of donor stock had some minor influence on the success of introduced lake trout in these lakes, but other factors, including angling, were also important. Closure of lakes to fishing was strongly associated with some successful introductions. MANOVA revealed differences in the geophysical and water quality variables, and fish community structures among the native, successful, and failed lakes. The lake groups were further distinguished by canonical variate analysis using either geophysical and water quality variables and/or presence-absence of fish species. Lakes were correctly classified to one of the three lake groups with 63-83% accuracy using a cross-validated, chance corrected, discriminant analysis. Lakes in which new lake trout populations failed to become established were smaller and shallower, had higher total dissolved solids, larger littoral areas, smaller hypolimnions, and richer fish communities, including more lake trout egg and juvenile predators, than lakes that were successfully colonized. Intensity of pre-dation by indigenous species was a possible cause of failure of introduced lake trout to establish self-sustaining populations. Similar fish communities in native and failed lakes suggested that invasion and colonization by lake trout was possibly determined by the order of arrival of colonizing species. This suggested that the present day Great Lakes fish communities, which have experienced a recent net gain in species, might be resistant to reestablishment of self-sustaining lake trout stocks.

The distribution of phylloquinone (Vitamin K1) in a small inland lake

The distribution of phylloquinone (Vitamin K1) in a small inland lake

RECREATION RESOURCE MANAGEMENT TOOLS IN WATER ENVIRONMENTS: AN ASSESSMENT OF APPROPRIATENESS

The paper is organized in four parts. The first part deals with definitions of water environments from a context of water-oriented recreation. Definitions are, in themselves, management tools of a kind, since they both structure our thinking about the environment and serve as the physical delineations of management attempts.The second part examines the politics of water-oriented recreation. The emphasis here will be on the adversary nature with which management tools often are applied, particularly the way in which such tools are used to defend or attack opposite positions. Thus, appropriateness of how such tools are used in some instances depends on the vested positions of particular interest groups, and how well - from their viewpoint - the tools have served them.The third part of the paper examines some selected management tools in their actual application in different contexts. The approach here is to outline several case-studies and to assess the appropriateness of the different methods that were used. These case studies translate into practice the general political issues raised in the second part. The range of tools under review includes carrying capacity, shoreline recreation physical capability, visual-aesthetic considerations, and the legal-jurisdictional framework for application.The fourth part summarizes with an overview of what tools we would ideally - and theoretically - need, and what tools, we now actually have and their effectiveness. The gap points to further research that is required, and also exposes once again some of the weaknesses of the existing techniques.The context of the discussion are the relatively small inland lakes, where there is a physical and activity proximity between land and water. Many of the principles will, however, apply to marine coasts, rivers, and other water environments. Several of the case studies will examine the use of management tools in the Muskoka District, and would be suitable for site visits.

Changes in the Yellow Perch Population of Lake Mendota, Wisconsin, Between 1916 and 1948

Many investigations of marine fish populations have been made during the last few decades. These were often prompted by a serious reduction in commercial yields and there usually followed in their wake restrictions on fishing and other conservation measures. In smaller inland lakes of this continent commercial fishing is relatively rare, and angling solely for recreation represents man's most important direct influence on the fishes present. There are few such lakes where the available information permits us to follow the fate of one particular species of fish over more than a human generation. One of the few is Lake Mendota, Wisconsin, and this report is an attempt to trace the changes in its population of yellow perch (Perca flavescens Mitchill) during the last 50 years. For the following reasons this lake is particularly well suited for such a study: (1). It was much influenced by human development because the rapidly growing city of Madison partly surrounds it. (2). Its limnology has been