Showing papers in "Transactions of The American Fisheries Society in 1990"
TL;DR: The committee's revised version of a nomenclature for protein-coding loci in fish closely parallels the one used for human genetics, but improves on it in several respects.
Abstract: The Fish Genetics Section of the American Fisheries Society established its Nomenclature Committee to develop and promote standardized genetic nomenclatures. Here, following public comments on previously published draft guidelines, we present the committee's revised version of a nomenclature for protein-coding loci in fish. This nomenclature closely parallels the one used for human genetics, but improves on it in several respects. The fish system (1) includes standardized abbreviations for commonly analyzed proteins, and provides formal symbols for gene loci encoding these proteins; (2) specifies typographic conventions for distinguishing between genes and proteins and for identifying alleles; (3) provides for multilocus isozyme systems, isoloci, regulatory loci, and pseudogenes; (4) allows important basic information (such as subcellular distributions of gene products, active substrate isomers, recent gene duplicates, and orthologous relationships among loci) to be specified in gene symbols via ...
834 citations
TL;DR: It is shown that weight-specific basal metabolism increases as size decreases; however, there is no corresponding increase in energy storage capacity, and this constraint is sufficient to explain the present locations of the northern distribu...
Abstract: The feeding activity of warm- and coolwater fishes can be severely restricted during the long period of cold temperatures characteristic of winter in temperate zone lakes and rivers. The effect of such restriction is greater for smaller fish. Weight-specific basal metabolism increases as size decreases; however, there is no corresponding increase in energy storage capacity. Thus, smaller fish tend to be less tolerant of starvation conditions because they exhaust their energy stores sooner. Such size dependence of starvation endurance has often been observed in laboratory experiments. In wild populations commonly subject to winter starvation, population viability hinges on the ability of young of year to complete a minimum amount of growth during their first year of life. From south to north, this ability is increasingly restricted as the growing season shortens and the starvation period lengthens. We show that this constraint is sufficient to explain the present locations of the northern distribu...
492 citations
TL;DR: This article presented a conceptual framework that views fish assemblages as products of a series of filters, operating at different spatial and temporal scales, through which an assemblage's component species must pass.
Abstract: Many autecological effects of temperature on fish are known, and fishery biologists have begun to incorporate this knowledge into population-level relations that can be used to assess possible effects of climatic warming on fishes and their habitats. However, the problem of extrapolating these or other relations to multispecies assemblages is not straightforward, given the complexity of community-level phenomena. I present a conceptual framework that views fish assemblages as products of a series of filters, operating at different spatial and temporal scales, through which an assemblage's component species must pass. This framework can facilitate an understanding of the processes that organize fish assemblages and suggest ways in which the complex problem can be divided into manageable pieces. I apply this framework in an examination of small-lake fish assemblages in three regions on two continents. The procedure reveals local and regional relations of richness and composition and highlights the ...
297 citations
TL;DR: Calcified structure-body relations indicate that in older fish, growth of the scales virtually ceases while body size increases, and allometry in both structures is positive during rapid growth and negative during slow growth.
Abstract: The relationship between size of calcified structures and the body of fish has been used widely in fisheries science to estimate body size at a younger age by “back-calculation.” I labeled the calcified tissue of northern pike Esox lucius with tetracycline to examine the concurrent linear growth of calcified structures and the body. I also conducted comparisons of the sizes of one or more calcified structures with body sizes of northern pike, lake trout Salvelinus namaycush, and muskellunge Esox masquinongy. Over a broad size and age range (juveniles and older), growth of scales, cleithra, and otoliths is only transitorily isometric in relation to body growth. Although scale growth is more strongly allometric than bone growth, allometry in both structures is positive during rapid growth and negative during slow growth. Slower-growing individuals have relatively smaller scales and cleithra. Calcified structure-body relations indicate that in older fish, growth of the scales virtually ceases while ...
250 citations
TL;DR: This work has shown that it is possible to suppress the first mitotic division offish eggs with high-pressure or -temperature treatments applied at the time of first cleavage to produce mitotic gynogenetic diploids and tetraploids.
Abstract: Manipulation of fish chromosomes dates back to the early part of this century. The earliest experiments involved induction of gynogenesis with sperm inactivated by radiation or chemical treatments. Temperature or pressure shocks applied soon after fertilization resulted in the retention of the second polar body and reconstitution of diploidy; triploidy resulted from shocks to fish ova fertilized with normal sperm. More recently, it has been possible to suppress the first mitotic division offish eggs with high-pressure or -temperature treatments applied at the time of first cleavage to produce mitotic gynogenetic diploids and tetraploids. Androgenesis has been successfully induced in fish by irradiation of ova, fertilization of eggs with normal sperm, and suppression of the first mitosis with high-pressure treatments. Gynogenetic diploids have been used for cytogenetic studies of meiotic phenomena and gene mapping. The general finding to date is that the arrangement of genes on chromosomes is high...
246 citations
TL;DR: Coho salmon Oncorhynchus kisutch had the fastest rates of development to hatching and emergence of the five species investigated; rankings for the other species depended upon temperature range.
Abstract: We examined rate of development to alevin hatching and fry emergence, embryo and alevin survival, and alevin and fry size for five Pacific salmon species. There was little difference among values for hatching and emergence time predicted by a modified thermal sums model, power law model (log-inverse Belehradek), or quadratic model. Coho salmon Oncorhynchus kisutch had the fastest rates of development to hatching and emergence of the five species investigated; rankings for the other species depended upon temperature range. Coho salmon embryos had the highest survival rates at low incubation (1.5°C) temperatures. Embryos of pink salmon O. gorbuscha had the lowest survival at temperatures less than 4°C. For all five species, incubation temperature was the more important factor in determining alevin length, and egg size was the more important factor in determining alevin weight. Egg weight was a major determinant of fry weight at emergence. Rates of development to hatching and emergence, and alevin a...
237 citations
TL;DR: In this paper, the size of thermal habitat of representative cold-, cool-, and warmwater fish for southern Lake Michigan and the central basin of Lake Erie before and after simulated global climate warming was estimated.
Abstract: We estimated potential changes in the size of thermal habitat of representative cold-, cool-, and warmwater fish for southern Lake Michigan and the central basin of Lake Erie before and after simulated global climate warming. Observed midlake thermal structures were modeled (BASE) and then manipulated with three general circulation climate models (OSU, GISS, GFDL) that projected warmer climates when atmospheric carbon dioxide concentrations were doubled. Under BASE conditions, on an annual basis, lake trout Salvelinus namaycush had the largest thermal habitat in southern Lake Michigan, coho salmon Oncorhynchus kisutch and yellow perch Perca flavescens had smaller thermal habitats, and largemouth bass Micropterus salmoides had none. Even for lake trout, the suitable thermal habitat was only 5–20% of the upper 200 m through the year. With rare exceptions, thermal habitat increased for species in all thermal guilds for all climate-warming scenarios. No thermal habitat was estimated for coldwater fis...
226 citations
TL;DR: In this article, the co-operation of local fisheries is discussed in the context of co-operative management of local fish fisheries, and the authors propose a co-operator management model.
Abstract: (1990). Co-Operative Management of Local Fisheries. Transactions of the American Fisheries Society: Vol. 119, No. 6, pp. 1059-1062.
205 citations
TL;DR: Radio telemetry was used to monitor the movements of eight large (437–635 mm), free-ranging brown trout for up to 346 d, finding that the fish appeared to have separate winter and summer ranges.
Abstract: Little is known about behavior patterns and habitat use of large (400+ mm total length) brown trout Salmo trutta. We used radio telemetry to monitor the movements of eight large (437–635 mm), free-ranging brown trout for up to 346 d. Total range of movement upstream and downstream varied from 370 m to 33,420 m. At some time during the year, six of the fish moved out of an area protected with no-kill fishing regulations, even though none of them were tagged and released closer than 2 km from its boundaries. However, four of five fish tracked during the height of the fishing season spent 87% of their time in the protected area. The fish appeared to have separate winter and summer ranges. Five of six fish tracked during autumn–winter moved upstream about 10 km to slower, deeper parts of the river between August and November, and remained there at least through the following April. The part of the river used as autumn–winter range was considered only marginal habitat for brown trout during summer due...
205 citations
TL;DR: Evidence suggests that the capacity for growth within a species may vary inversely with the length of the growing season across a latitudinal gradient, and that this “countergradient variation” in growth rate may be more widespread than has been recognized.
Abstract: Evidence suggests that the capacity for growth (i.e., maximum growth potential) within a species may vary inversely with the length of the growing season across a latitudinal gradient. I evaluated this hypothesis with data on three species—American shad Alosa sapidissima, striped bass Morone saxatilis, and mummichog Fundulus heteroclitus—having wide latitudinal ranges (≈29–46°N) along the east coast of North America. For each of these species, the length of the first growing season decreases by a factor of about 2.5 with increasing latitude within the species' range, yet body size at the end of the first growing season is independent of latitude. Northern fish must, therefore, grow substantially faster within the growing season than do southern fish. This “countergradient variation” in growth rate may be more widespread than has been recognized. A similar latitudinal pattern in growth rate has a genetic basis in the Atlantic silverside Menidia menidia, and data on Atlantic salmon Salmo salar, lar...
197 citations
TL;DR: In this article, surface observation, diving, and electrofishing were compared as methods to study habitat use by young brown trout Salmo trutta and Atlantic salmon S. salar in a Norwegian river.
Abstract: Surface observation, diving, and electrofishing were compared as methods to study habitat use by young brown trout Salmo trutta and Atlantic salmon S. salar in a Norwegian river. These three methods often gave widely disparate information about habitat use by young of these two species. The probability of encountering individual fish varied when the same method was used in different habitats. Surface observation and diving produced similar results in habitats with low mean water velocities (<20 cm/s) and fine substrate (mean diameter, ≤64 mm), whereas electrofishing was more effective than the sighting methods in shallow areas with greater water velocities and larger substrate.
TL;DR: Significant indirect effects included decreased abundance of dominant species, increases of some rare species, and decreases of mean size for species most vulnerable to predation.
Abstract: We designed an experiment to test the relative importances of direct and indirect effects of piscivorous predation on an assemblage of small fishes in a piscivore-free lake, The direct effect is defined as consumption of prey fishes. Indirect effects include habitat changes associated with predator avoidance behavior, increases of emigration rates, and changes of composition and size structure of the prey community. After a year of premanipulation study, adult northern pike Esox lucius (a predator species) were introduced into the lake, Decrease of prey fish biomass due to increased emigration was at least as great as that due to direct consumption by the predators. Significant indirect effects included decreased abundance of dominant species, increases of some rare species, and decreases of mean size for species most vulnerable to predation. Indirect effects occurred rapidly and were most apparent during weeks immediately after northern pike were introduced.
TL;DR: This paper used fish bioenergetics models to assess the effect ofglobal climate warming on the growth and prey consumption of warm-, cool-, and coldwater fishes at three sites spanning the range of thermal environments in the Great Lakes.
Abstract: We used fish bioenergetics models to assess the effect ofglobal climate warming on the growth and prey consumption of warm-, cool-, and coldwater fishes at three sites spanning the range of thermal environments in the Great Lakes. Historical air and water temperature data and projected air temperature changes from three global climate models were used as input to regression models, which generated projections of water temperature changes before and after climate warming that would result from a doubling in atmospheric CO2 concentration. The bioenergetics simulations indicated that annual growth by yearling fish would increase with climate warming if prey consumption increased, but would decrease if prey consumption was constant. Changes in growth would be most pronounced in spring and autumn owing to a lengthening of the period during which fishes may behaviorally thermoregulate to find their optimal temperature for growth. Fish unable to thermoregulate (e.g., due to hypolimnetic oxygen depletion...
TL;DR: In this paper, the authors suggest modifying the term "heat increment" (also known as specific dynamic action) to the less-precise "apparent heat increment" to take account of the mechanical aspects of the postabsorptive processes that follow the ingestion of food.
Abstract: Bioenergetic models of growth endeavor to integrate food-processing transactions with energy expenditures imposed by abiotic and biotic factors. Some components of these models have lagged behind others in the synthesis of new information. A case in point is heat increment, a measure of metabolic work primarily for the postabsorptive processes that follow the ingestion of food. Importantly, the energy requirements for grasping, chewing, and swallowing food are technically distinct from those for heat increment but are experimentally difficult to separate from them. In order to take special account of these mechanical aspects, we suggest modifying the term “heat increment” (also known as specific dynamic action) to the less-precise “apparent heat increment.” Bioenergetic models invariably incorporate the assumption that apparent heat increment, relative to food intake, is independent of other variables. Laboratory studies have revealed that apparent heat increment is not always a fixed proportion ...
TL;DR: In this article, a hydrometeorological model of stream temperature to two southern Ontario streams in the summer was calibrated to estimate potential reductions of thermal habitat for brook trout Salvelinus fontinalis.
Abstract: I calibrated a hydrometeorological model of stream temperature to two southern Ontario streams in the summer to estimate potential reductions, due to climatic warming, of thermal habitat for brook trout Salvelinus fontinalis. Summer habitat for brook trout in both streams, determined from electrofishing surveys during 1987 and 1988, was delimited downstream by a thermal barrier of about 24°C. Tagging data for one stream suggested that brook trout moved upstream to summer habitat as water temperatures in downstream areas increased during spring and summer. To estimate upstream movement of the thermal habitat barriers and concomitant reductions in summer habitat for brook trout due to climatic warming, I forced the calibrated stream models with the changes in mean July and August air temperatures (increase, 4.1°C) projected for the region by the climate warming scenario of the Goddard Institute for Space Studies. I also adjusted the temperature of groundwater discharging to the streams by the proje...
TL;DR: A synthesis of the results from the coupled model forced by climate warming scenarios from three atmospheric general circulation models suggested that there will be a substantial decline in oxygen concentrations in the central basin of Lake Erie.
Abstract: A coupled hydrodynamic and water quality model was used to examine the response of dissolved oxygen concentrations to warming of the central basin of Lake Erie. An area-averaged hydrodynamic model was used to estimate the lake temperatures and thermocline variability as forced by surface heating and winds. Vertical turbulence mixing processes were incorporated by a second-moment, turbulence closure submodel. The water quality model comprised a set of 15 mass balance equations that predicted distributions of phytoplankton biomass, nutrient concentration, and dissolved oxygen. A synthesis of the results from the coupled model forced by climate warming scenarios from three atmospheric general circulation models suggested that there will be a substantial decline in oxygen concentrations in the central basin. Although forecasts of future conditions that are beyond established experiences are uncertain, it appears likely that climate warming will lead to such a decline regardless of details in changes ...
TL;DR: Here the applicability of the combined model, of the Arrhenius form, to analogous ecological situations for aquatic ectothermic living systems is assessed.
Abstract: Many mathematical relationships have been used to summarize quantitative information about the effects of temperature on rate processes in ectothermic living systems. One of the more common relationships, which has been used for a century, is here termed the “combined exponential model.” An exponential model, as with a first-order chemical reaction, is used to define a coefficient for a rate at a particular temperature; another exponential relationship (of the van't Hoff or the Arrhenius form) is then used to relate the coefficients of the rate process to their respective temperatures. The Arrhenius form has come to be preferred over the van't Hoff form. In ectotherm physiology, the combined exponential model applies when the relevant organism has not evolved means of compensating biologically for the underlying physicochemical dynamics as affected by temperature, Here we assess the applicability of the combined model, of the Arrhenius form, to analogous ecological situations for aquatic ectother...
TL;DR: White perch Morone americana invaded Lake Ontario about 1946 and are now found in Lakes Erie, St. Clair, and Huron, and in Green Bay, Lake Michigan as mentioned in this paper.
Abstract: White perch Morone americana invaded Lake Ontario about 1946 and are now found in Lakes Erie, St. Clair, and Huron, and in Green Bay, Lake Michigan. The indigenous marine distribution of white perch along the Atlantic coast of North America and analysis of climatological data suggest that the northern Gulf of St. Lawrence in the vicinity of the Gasp& Peninsula is too cold to permit white perch to establish local populations or to invade the Great Lakes via the St. Lawrence River. High mortalities of white perch have occurred in Lake Ontario during very cold winters, further suggesting that distribution of white perch is limited by low tolerance of cold temperature. Warmer-than-average summer and winter temperatures during the late 1940s coincided with the invasion of white perch into the Great Lakes via transportation canals in the state of New York. Tolerance of young-of-the-year white perch for low temperature was tested in the laboratory in overwinter experiments at constant temperatures of 2....
TL;DR: In aquatic vertebrates, the inertia of the body and entrained water, which is proportional to body volume, resists acceleration as discussed by the authors, is important during maneuvers when animals accelerate or turn.
Abstract: As aquatic vertebrates increase in size, hydrofoils, which use lift to generate thrust, are increasingly used as propulsors. One factor affecting the magnitude of the lift force is the area of the propulsor. Resistance to cruising and sprints is mainly due to drag, but inertia is important during maneuvers when animals accelerate or turn. The inertia of the body and entrained water, which is proportional to body volume, resists acceleration. Because a thrust that is proportional to surface area is used to maneuver a resistance that is proportional to volume, acceleration performance and maneuverability are expected to decline with increasing size, This trend is ameliorated to some extent by the high swimming speeds attainable by warm-bodied vertebrates and the reduced resistance to acceleration characteristic of the skeletons of dolphins and ichthyosaurs. Maneuvers are essential for capture of elusive prey and avoidance of predators. As they increase in size, aquatic vertebrates use various means...
TL;DR: This work on rainbow trout Oncorhynchus mykiss includes growth studies of whole fish, the relative (allometric) growth of organs and tissues and of protein and lipid contents of the body, and the influence of white muscle fiber growth on whole-body growth rate and maximum body size.
Abstract: At the organismic (whole-fish) level, fish growth has the property of “plasticity”; that is, it can display considerable intraspecific variation in response to differences in such factors as temperature and food supply. Growth can also be investigated at any of a series of increasingly more reductionist levels of biological organization. My work on rainbow trout Oncorhynchus mykiss includes growth studies of whole fish, the relative (allometric) growth of organs and tissues and of protein and lipid contents of the body, and the influence of white muscle fiber growth on whole-body growth rate and maximum body size, These studies show that patterns of growth are conserved despite major differences in organismic growth rate.
TL;DR: In this paper, the authors predicted some possible effects of climate change on distribution of anadromous and landlocked stocks of striped bass Morone saxatilis in the Gulf of Mexico and Florida.
Abstract: Habitat space for a fish species is normally constrained by extreme temperatures and low dissolved oxygen concentrations that the fish avoid. Both latitudinal limits to a species' geographic distribution and availability of suitable habitat on the local level may be altered by climate change. During the next century, average temperatures are expected to rise globally, and rainfall is expected to decrease in mid latitudes and increase in high latitudes. I have predicted some possible effects of climate change on distribution of anadromous and landlocked stocks of striped bass Morone saxatilis. The tenuous existence of striped bass along the northern coast of the Gulf of Mexico and in Florida will likely be jeopardized by regional warming and reduced streamflow. In many freshwater lakes, reservoirs, and estuaries, the existing summer constriction of suitable habitat by high temperatures and low oxygen concentrations may be aggravated by warming, altered streamflow, and increased hypoxia. A major lo...
TL;DR: The role of commercial fishing in the destruction of lake trout Salvelinus namaycush in Lakes Huron, Michigan, and Superior in the 1940s and 1950s was investigated in this paper.
Abstract: To assess the role of commercial fishing in the destruction of lake trout Salvelinus namaycush in Lakes Huron, Michigan, and Superior in the 1940s and 1950s, we reviewed the literature and analyzed catch and effort data for U.S. waters by regression analysis. There is abundant evidence of the effect of the sea lamprey Petromyzon marinus in the destruction of lake trout, but some have claimed that fishing also was influential. We considered that a persistent, significant decrease in catch per unit of effort before and in the first few years after the sea lamprey was first found in a lake would be evidence of overfishing. We found no convincing evidence of overfishing in Lakes Huron and Michigan. Lake trout probably were overfished in Lake Superior before the sea lamprey became a major influence. We conclude that statements that lake trout were destroyed in Lake Huron or Lake Michigan by a combination of overfishing and the sea lamprey are not justified. The same claim applied simply to the Great L...
TL;DR: This paper used a one-dimensional numerical model to estimate the present and possible future temperature structures in Lake Michigan, based on model output from simulations of the 1981-1984 offshore temperature field.
Abstract: I used a one-dimensional numerical model to estimate the present and possible future temperature structures in Lake Michigan. The estimates were based on model output from simulations of the 1981–1984 offshore temperature field. Once the water temperature climatology was estimated, I examined three scenarios based on general circulation models in which atmospheric CO2 was doubled. The models were those of the Goddard Institute for Space Studies (GISS), the Geophysical Fluid Dynamics Laboratory (GFDL), and Oregon State University (OSU). In general, simulations based on these three scenarios suggested that winter and summer heat contents of the lake would be higher than at present; the summer increase would be less than that in winter. The higher winter heat content would cause an earlier onset of full thermal stratification, and the season of stratification would increase by up to two months. The earlier onset of stratification, coupled with little change in the wind stress pattern, would yield st...
TL;DR: The dynamics of these early life stages appear to significantly influence both lake whitefish year-class strength and eventual recruitment in Grand Traverse Bay, Lake Michigan.
Abstract: A study was conducted in Grand Traverse Bay, Lake Michigan, during 1983 and 1984 to identify factors that are important in determining year-class strength of lake whitefish Coregonus clupeaformis. The major determinants of year-class success were overwintering egg survival and the amount of food available to larval lake whitefish during the first 7 weeks of life, Egg mortality was related to the timing of ice cover, with an early cold winter producing the highest survival. Larval survival was affected by the abundance of available prey, i.e., copepod zooplankton between the sizes of 0.7 and 1A mm in total length. In 1983, when zooplankton of this size were abundant relative to larval fish density, high rates of growth and survival of lake whitefish ensued. In 1984, the prey-per-fish ratio declined greatly, and poor growth and low survival were observed. The dynamics of these early life stages appear to significantly influence both lake whitefish year-class strength and eventual recruitment in Gra...
TL;DR: A model that accounts for the variety in observed relationships between temperature preference and acclimation in fishes predicts that fishes exhibiting Precht's “partial,’ “no,” and “inverse” compensation prefer temperatures that are increasing, independent, and decreasing functions of acclimations temperature, respectively.
Abstract: We present a model that accounts for the variety in observed relationships between temperature preference and acclimation in fishes. The preferred temperature is that temperature at which Fry's scope for metabolism is maximized. Thermal acclimation shifts the temperature for maximum scope in such a way that Zahn's types of temperature-preference acclimation correspond with Precht's types of metabolic compensation. The model predicts that fishes exhibiting Precht's “partial,” “no,” and “inverse” compensation prefer temperatures that are increasing, independent, and decreasing functions of acclimation temperature, respectively. Experiments with bluegill Lepomis macrochirus and blue tilapia Tilapia aurea, together with information from the literature, provide support for the model.
TL;DR: The authors examined relations between mercury concentrations in walleyes Stizostedion vitreum and the characteristics of clear-water Wisconsin lakes, which spanned a broad range of pH values (5.0-8.1) and acid-neutralizing capacities (1,017 μ eq/L).
Abstract: We examined relations between mercury concentrations in walleyes Stizostedion vitreum and the characteristics ofclear-water Wisconsin lakes, which spanned a broad range of pH values (5.0–8.1) and acid-neutralizing capacities (–9 to 1,017 μeq/L). Total concentrations of mercury in axial muscle tissue of walleyes (total length, 25–56 cm) varied from 0.12 to 1.74 μg/g wet weight. Concentrations were greatest in fish from the eight lakes with pH less than 7.0; concentrations in these fish equaled or exceeded 0.5 μg/g in 88% of the samples analyzed and 1.0 μg/g in 44%. In the five lakes with pH of 7.0 and above, concentrations exceeded 0.5 μg/g in only 1 of 21 walleyes. Multiple regression revealed that lake pH and total length offish accounted for 69% of the variation in mercury concentration in walleyes. Regression models with total length and either waterborne calcium or acid-neutralizing capacity as independent variables accounted for 67% of the variation in concentration. The observed differences...
TL;DR: Assessment of salmonid production in summer in a second- and third-order montane stream in eastern Tennessee in 1987 revealed reductions in biomass over the 4-month period that ranged from 31 to 49%, whereas population densities declined by 32–46% during the same period.
Abstract: We assessed salmonid production in summer in a second- and third-order montane stream in eastern Tennessee in 1987. We sampled three stream sections, one containing exclusively brook trout Salvelinus fontinalis, one containing exclusively rainbow trout Oncorhynchus mykiss, and a third with a mixture of both species. Population estimates for July and October 1987 revealed reductions in biomass over the 4-month period that ranged from 31 to 49%, whereas population densities declined by 32–46% during the same period. Total net production during the 4-month period was low and ranged from 0.38 to 0.45 g/m2. From June through September, the mean number of prey items per stomach ranged from 4.2 to 29.9, whereas the mean relative weight of stomach contents ranged from 0.12 to 1.34 mg dry weight per gram wet weight offish flesh. There was a strong positive correlation between the mean relative weight of stomach contents and the mean condition factor for a given date. Calculated energy intake was below the...
TL;DR: Early life stages of fishes with tow nets and light traps in Orange Lake, Florida, from June 1983 to June 1984 were sampled; mixed vegetation was an important nursery area for juvenile fish of many species, and the panic grass was especially important for larvae.
Abstract: We sampled early life stages of fishes with tow nets and light traps in Orange Lake, Florida, from June 1983 to June 1984. Four habitats were sampled, one open water and three vegetated; vegetated zones were dominated by panic grass Panicum spp., hydrilla Hydrilla verti- cillata, or a community of mixed floating and emergent vegetation. Vegetated zones of any type were important nursery areas for the fish assemblage. Mixed vegetation was an important nursery area for juvenile fish of many species, perhaps due to its structural complexity, and the panic grass was especially important for larvae. Larvae of most species first appeared in Orange Lake at temperatures similar to those at which they appear in temperate lakes, but larvae were present on almost all sampling dates (including those in winter). Larvae of golden shiners Notemigonus cry- soleucas. threadfin shad Dorosoma petenense, and gizzard shad D. cepedianum appeared on earlier dates than in temperate systems. Larvae of individual species were present over a longer period than in temperate systems, reflecting longer spawning seasons in Orange Lake. Habitat use by larvae was variable for several species; larval bluegills Lepomis macrochirus. which are typically considered limnetic, inhabited panic grass and hydrilla, in addition to open water.
TL;DR: Diet overlap for age-0 white and yellow perch was high when D. pulex was present, and the potential for interspecific competition was greatest when these fish were similar in length.
Abstract: Diet and growth of age-0 white perch Morone americana and age-0 yellow perch Perca flavescens were compared during July–October 1980 and 1987. Both fish species fed on Daphnia pulex in 1980 and growth was rapid; prey biomass per gram of fish was 2–12 times higher for white perch than for yellow perch. In 1987, white perch consumed up to three times more prey biomass than yellow perch, but the subsequent disappearance of D. pulex caused both fish species to switch to macroinvertebrates and growth of both species declined. Between 1977 and 1987, mean weights and specific growth rates of white perch exceeded yellow perch by October in all years, and weights of white perch were closely tied to the density of D. pulex in late summer–early fall (Spearman's rank correlation = 0.58, P = 0.07). Diet overlap for age-0 white and yellow perch was high when D. pulex was present, and the potential for interspecific competition was greatest when these fish were similar in length. Because of a prolonged spawning...
TL;DR: Analysis of food habits of rainbow trout Oncorhynchus mykiss in Lake Washington, Washington, found that rainbow trout smaller than 250 mm (fork length) ate primarily Daphnia pulicaria during summer and autumn; larger fish were piscivorous throughout the year.
Abstract: I examined food habits of rainbow trout Oncorhynchus mykiss in Lake Washington, Washington, for relationships to the spatial and temporal distribution of their prey. Rainbow trout smaller than 250 mm (fork length) ate primarily Daphnia pulicaria during summer and autumn; larger fish were piscivorous throughout the year. Longfin smelt Spirinchus thaleichthys made up the largest fraction of fish prey in the diet of rainbow trout from the nearshore zone during autumn and winter, whereas prickly sculpin Cottus asper (in 1984) and yellow perch Perca flavescens (in 1985) were most important in spring and summer. Rainbow trout in the offshore zone (>15 m deep) ate mostly longfin smelt in spring and summer. Longfin smelt exhibited a 2-year cycle of abundance that appeared to influence the feeding habits of rainbow trout. During 1984, the adult longfin smelt population was large and provided the major prey of rainbow trout. When adult longfin smelt were less abundant during the 1985 winter, the fish fract...