Micropterus salmoides

Food habits of co-occurring largemouth bass (Micropterus salmoides) and spotted bass (M. punctulatus) were documented in two New Mexico reservoirs, Brantley Lake and Sumner Lake, from May 2001 to May 2002. In Brantley Lake, bass ate mainly fish, whereas bass in Sumner Lake ate mainly crayfish. Food habits of both species varied seasonally and there was substantial overlap in the

In North Africa, this experimental work represents the first artificial induced spawning of Micropterus salmoides on artificial gravel nests. During February 2012, gillnet fishes were collected from 3 dams located in the west of Algeria. 24 adults including 10 males and 14 females were selected, and transferred into two under cover concrete rectangular raceways (R1 and R2) supplied with suitable water quality. Males and females were kept separated, and supplied with ad libitum natural food. The experiments started at 14°C water temperature, and were carried out on 3 batches of fishes. In R1, the batch B1 consisted of 3 males and 5 females. In R2, the batch B2 included 6 males and 8 females, and B3 of a couple of fishes. 52 days later, when the water temperature reached 23°C, the fishes began to exhibit courtship behaviours. As a control group, fishes of B1 were not given any hormonal treatment. Fishes of B2 were given a single injection of 4500 IU of HCG/Kg of body weight. The couple of fishes in B3 were given a single injection of a solution of 4500 IU of HCG/Kg of body weight mixed with the extract of 1g of pituitary gland of Cyprinus carpio. A 1m 2 artificial spawning gravel nest was immersed at each corner of the raceways. No spawning occurred in B1 despite courtship behaviour. For B2, spawning occurred on the bottom of R2 and on one artificial nest (average 2000 eggs/m 2). B3 showed better spawning (average 3500 eggs/m 2). The artificial nests were transferred into nursery raceways under laboratory conditions. The global rate of hatching was 80%. Monitoring of the fry growth was carried out until the 24 th day post-hatching.

Fish proximate composition and energy density can influence growth, survival, and reproduction, so it is important to develop models to understand the patterns and predict dynamic changes. This paper presents three such models. Model 1 describes the general pattern of changes in lipid, protein, ash, and energy density that occur with changes in water content. The key assumption this model is that there is a fixed amount of water associated with each gram of protein and a much smaller fixed amount of water associated with each gram of lipid. In combination with a mass balance constraint, this explains the commonly observed linear relationship between the fraction lipid and the fraction water. Because energy density varies in direct proportion to the fractions lipid and protein, the linear relationship between body composition and fraction water makes energy density also a linear function of the fraction water. The model is fitted to data for lake trout Salvelinus namaycush and coho salmon Oncorhynchus kisutch for a limited range in wet weight. Model 2 describes the pattern of proximate composition and energy density that occurs with variation in body size. A strong pattern was found between the mass of water and the mass of protein, suggesting strict control of body water. The model is fitted to data for common carp Cyprinus carpio and bluegill Lepomis macrochirus. This analysis shows that the relationship between body composition, energy density, and fraction water is expected to vary with body size because both the water : protein ratio and the fraction ash change with body size. Model 3 demonstrates how this approach can be used to predict changes in fish body composition and energy density during starvation, as might be done with a bioenergetics model. This model is fitted to data from a starvation experiment involving largemouth bass Micropterus salmoides. A model for fish proximate composition and energy density would improve understanding of observed patterns in fish body composition data and enhance bioenergetics models of fish growth. A model for proximate composition could help explain two common patterns related to percent lipid and energy density, which are linearly related to percent water (

We used three different sizes of trap nets (small, medium, and large sizes of both mesh and throats) sampled at 6-h intervals to determine peak activity time(s) for fish along the deep vegetation line in Sandy Lake, Portage County, Ohio. Over 90% of the total catch comprised bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides, pumpkinseed L. gibbosus, and black crappie Pomoxis nigromaculatus. All four species had their lowest catch per unit effort (CPUE) at night (2200-0400 hours). Different lengthclasses of pumpkinseeds and black crappies had peak CPUE during different times of the day. Smaller lengthclasses of all species (i.e., those captured in small and medium trap nets) had peak CPUE during either dawn (0400-1000 hours) or midday (1000-1600 hours), whereas the only piscivores captured in high abundance (black crappies 150-303 mm total length captured in large trap nets) had higher CPUE at dusk (1600-2200 hours) than during any other time of the day. It is possible that these activity patterns are affected by predation risk or food availability. These findings indicate that individual species or length-classes do not typically interact directly even though they use the same habitat. Therefore, when predicting potential species interactions in natural systems, it is important to consider diel changes in behavior. When possible, sampling schedules should take into account the activity patterns of the species of interest to ensure that information is obtained from the most appropriate time(s) of day to more accurately assess species interactions.

Bluegill Lepomis macrochirus, gizzard shad Dorosoma cepedianum, and largemouth bass Micropterus salmoides are common lentic species that may compete for invertebrate prey resources, and interactions among these species can have important consequences for aquatic community structure. Differential foraging behavior of bluegills and gizzard shad as juveniles, for example, may structure zooplankton and benthos communities and influence the growth of juvenile largemouth bass. We conducted a mesocosm experiment (1.6-m-diameter circular tanks) in which we allowed high and low densities of juvenile bluegills (70-100 mm total length [TL]) and gizzard shad (135-155 mm TL) to forage on established zooplankton and benthos communities for 6 weeks. After this period, we added juvenile largemouth bass (50-80 mm TL) to each tank for 4 weeks to examine growth and diets. Although foraging by bluegill and gizzard shad had limited effects on the total population densities of invertebrates, important taxon-specific effects were observed. At the time that largemouth bass were added to tanks, bluegill treatments exhibited a higher macrozooplankton density, higher turbidity, and lower density of larval hydrophilid coleopterans than did gizzard shad or control treatments. The growth of juvenile largemouth bass was strongly influenced by treatment; largemouth bass grew at similar rates in the gizzard shad and control treatments but lost weight in the bluegill treatments. We suggest that bluegills compete with juvenile largemouth bass for preferred prey items, thereby limiting largemouth bass growth. Further, our results demonstrate that the presence of larger gizzard shad may not have the negative implications observed in previous studies with smaller individuals. Knowledge of the relative, size-specific abundances of bluegills and gizzard shad should provide resource managers with valuable information for developing initiatives aimed at maximizing the growth of juvenile largemouth bass.

The in6uence of mercury on the general and reproductive health of wild 5sh populations has not been well studied. Therefore, a variety of health and reproductive indicators were measured in male largemouth bass (Micropterus salmoides) collected from three bodies of water in New Jersey: Assunpink Lake, Manasquan Reservoir, and Atlantic City Reservoir. The mean mercury content in 5sh muscle from Assunpink Lake was 0.30 g/g; from Manasquan Reservoir, 1.23 g/g; and from Atlantic City Reservoir, 5.42 g/g. Body weight, length, condition factor, and gonadosomatic index were similar for all three lakes. Furthermore, there was no signi5cant relationship between muscle mercury content and adrenocortical function, indicated by interrenal nuclear diameter and serum cortisol levels following stress. Bass from the Atlantic City Reservoir had a slightly lower, although signi5cant, liver somatic index than bass from the two other lakes. A signi5cant, positive correlation between 11-ketotestosterone serum concentrations and mercury muscle content was detected, although no signi5cant relationship between testosterone serum concentrations and mercury muscle content was found. The 5ndings of this study suggest that, while elevated levels of mercury in 5sh potentially alter androgen pro5les, they do not substantially decrease other indicators of general and reproductive health. 2002 Elsevier Science (USA)

In North Africa, this experimental work represents the first artificial induced spawning of Micropterus salmoides on artificial gravel nests. During February 2012, gillnet fishes were collected from 3 dams located in the west of Algeria. 24 adults including 10 males and 14 females were selected, and transferred into two under cover concrete rectangular raceways (R1 and R2) supplied with suitable water quality. Males and females were kept separated, and supplied with ad libitum natural food. The experiments started at 14°C water temperature, and were carried out on 3 batches of fishes. In R1, the batch B1 consisted of 3 males and 5 females. In R2, the batch B2 included 6 males and 8 females, and B3 of a couple of fishes. 52 days later, when the water temperature reached 23°C, the fishes began to exhibit courtship behaviours. As a control group, fishes of B1 were not given any hormonal treatment. Fishes of B2 were given a single injection of 4500 IU of HCG/Kg of body weight. The couple of fishes in B3 were given a single injection of a solution of 4500 IU of HCG/Kg of body weight mixed with the extract of 1g of pituitary gland of Cyprinus carpio. A 1m 2 artificial spawning gravel nest was immersed at each corner of the raceways. No spawning occurred in B1 despite courtship behaviour. For B2, spawning occurred on the bottom of R2 and on one artificial nest (average 2000 eggs/m 2). B3 showed better spawning (average 3500 eggs/m 2). The artificial nests were transferred into nursery raceways under laboratory conditions. The global rate of hatching was 80%. Monitoring of the fry growth was carried out until the 24 th day post-hatching.

Controlling exotic aquatic weeds such as Eurasian watermilfoil (Myriophyllum spicatum L.) is a high priority for many aquatic plant management programs. Yet, the effects of Eurasian watermilfoil invasion and subsequent removal on sportfish production and food webs are insufficiently understood. Changes in aquatic plant abundance or architecture, caused by invasion and/or removal of exotic plants, may affect age-0 largemouth bass (Micropterus salmoides Lacepede) growth and recruitment. We hypothesized that age-0 largemouth bass piscivory and growth: 1) decreases along a gradient of increasing Eurasian watermilfoil coverage and 2) benefits from lowdose applications of fluridone herbicide intended to shift Eurasian watermilfoil dominated plant communities to native dominated plant communities. In a multiple lake evaluation of the effects of selective removal of Eurasian watermilfoil on age-0 largemouth bass, percent coverage of Eurasian watermilfoil ranged 8% to 50% in lakes treated with 5 to 7 ppb fluridone and 43% to 91% in reference lakes. Coverage of native plants ranged from 62% to 95%. Selective removal of Eurasian watermilfoil did not have a significant positive effect on age-0 largemouth bass growth. Rather, age-0 bluegill (Lepomis macrochirus Rafinesque) prey availability, which varied considerably among lakes, had a strong positive effect on age-0 largemouth bass piscivory and growth. Factors influencing age-0 bluegill availability to age-0 largemouth bass appear more related to size structure of largemouth bass and bluegill populations than to plant cover.

Gordon Creek, a tributary of the Maumee River in northwestern Ohio, was investigated by Meek in 1887, by Trautman 1929-38, by the personnel of the Ohio Division of Wildlife between 1954 and 1973, and by Trautman and Gartman in 1973. Dredging and ditching in this area were begun about 1850, continuing until the present, with major channelization occurring in 1935.

Total mercury (THg) concentrations were measured for various fish species from Lakes Turkana, Naivasha and Baringo in the rift valley of Kenya. The highest THg concentration (636 ng g À1 wet weight) was measured for a piscivorous tigerfish Hydrocynus forskahlii from Lake Turkana. THg concentrations for the Perciformes species, the Nile perch Lates niloticus from Lake Turkana and the largemouth bass Micropterus salmoides from Lake Naivasha ranged between 4 and 95 ng g À1. The tilapiine species in all lakes, including the Nile tilapia Oreochromis niloticus, had consistently low THg concentrations ranging between 2 and 25 ng g À1. In Lake Naivasha, the crayfish species, Procambrus clarkii, had THg concentrations similar to those for the tilapiine species from the same lake, which is consistent with their shared detritivore diet. THg concentrations in all fish species were usually consistent with their known trophic position, with highest concentrations in piscivores and declining in omnivores, insectivores and detritivores. One exception is the detritivore Labeo cylindricus from Lake Baringo, which had surprisingly elevated THg concentrations (mean=75 ng g À1), which was similar to those for the top trophic species (Clarias and Protopterus) in the same lake. Except for two Hydrocynus forskahlii individuals from Lake Turkana, which had THg concentrations near or above the international marketing limit of 500 ng g À1 , THg concentrations in the fish were generally below those of World Health Organization's recommended limit of 200 ng g À1 for at-risk groups.

Lake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. They are Oreochromis leucostictus, Tilapia zillii, Micropterus salmoides (largemouth bass), Barbus amphigramma and Poecilia reticulata (guppy). The first three of these form the basis of an important gill net fishery and bass are

1. Riverscapes consist of the main channel and lateral slackwater habitats along a gradient of hydrological connectivity from maximum connection in main channel habitats to minimum connection in backwaters. Spatiotemporal differences in water currents along this gradient produce dynamic habitat conditions that influence species diversity, population densities and trophic interactions of fishes. 2. We examined the importance of lateral connectivity gradients for food web dynamics in the Upper Mississippi River during spring (high flow, moderately low temperatures) and summer (low flow, higher temperatures). We used literature information and gut contents analyses to determine feeding guilds and stable isotope analysis to estimate mean trophic position of local fish assemblages. During June and August 2006, we collected over 1000 tissue samples from four habitats (main channel, secondary channels, tertiary channels and backwaters) distributed within four hydrologic connectivity gradients. 3. Mean trophic position differed among feeding guilds and seasons, with highest values in spring. Mean trophic position of fish assemblages, variability in trophic position and food chain length (maximum trophic position) of the two dominant piscivore species (Micropterus salmoides and M. dolomieu) in both seasons were significantly associated with habitat along the lateral connectivity gradient. Food chain length peaked in tertiary channels in both seasons, probably due to higher species diversity of prey at these habitats. We infer that food chain length and trophic position of fish assemblages were lower in backwater habitats in the summer mainly because of the use of alternative food sources in these habitats. 4. A greater number of conspecifics exhibited significant among-habitat variation in trophic position during the summer, indicating that low river stages can constrain fish movements in the Upper Mississippi River. 5. Results of this study should provide a better understanding of the fundamental structure of large river ecosystems and an improved basis for river rehabilitation and management through knowledge of the importance of lateral complexity in rivers.

Tissue residues of total mercury (Hg), total polychlorinated biphenyls (PCBs), and lipid-based PCBs; plasma concentrations of endocrine biomarkers; and reproductive and histologic biomarkers were assessed in 460 carp (Cyprinus carpio), bass (Micropterus salmoides and Micropterus dolomieui), and bullhead (Ameiurus nebulosus) collected from eight sites across the Hudson River Basin in the spring of 1998 to determine if endocrine disruption was evident in resident fish species and to evaluate contaminant-biomarker interrelations. Total PCBs in bed sediments (maximum 2,500 µg kg -1 ) could explain 64 to 90 % of the variability in lipidbased PCB residues in tissues (maximum 1,250 µg PCB g-lipid -1 ) of the four species. The 17b-estradiol to 11-ketotestosterone ratio, typically less than 1.0 in male fish and greater than 1.0 in females, exceeded 1.4 in all male largemouth bass and 35 % of male carp and bullhead at one site 21 km downstream from a major PCB source. Endocrine biomarkers were significantly correlated with total Hg in female smallmouth bass and carp, and with lipid-based PCBs in males of all four species. Empirical evidence of endocrine modulation in blood plasma of male and female fish from sites with and without high PCB residues in bed sediments and fish tissues suggest that PCBs, Hg, or other contaminants may disrupt normal endocrine function in fish of the Hudson River. * Corresponding author phone: +1 518 285 5605;

Sport fish from Normandy Reservoir, Tennessee, were sampled for more than 6 years with a variety of gears targeting different life stages. Normandy Reservoir experienced different hydrologic regimes over the sampling period that we roughly grouped into dry years (1992 and 1995), intermediate years (1993 and 1997), and wet years (1994 and 1996). Year-class strength of largemouth bass Micropterus salmoides was fixed each year by late summer or early fall. Catch of age-1 largemouth bass in spring electrofishing samples was directly related to the number of days the reservoir was at or over full pool when the fish were age 0. Largemouth bass produced in a wet year and intermediate year were more than twice as abundant at age 3 than fish produced in two dry years. Recruitment of spotted bass M. punctulatus could not be linked to reservoir hydrology. Crappies Pomoxis spp., white bass Morone chrysops, and saugeyes (walleye Stizostedion vitreum ϫ sauger S. canadense) produced poor year-classes in dry years and strong year-classes in wet years. The responses of these latter three taxa in intermediate years were variable, although they were more characteristic of dry-year responses than wet-year responses. Recruitment of crappies, white bass, and saugeyes was positively related to mean daily discharge of the reservoir in the prespawn period (1 January to 31 March) each year. Recruitment of largemouth bass was dependent on high water during the spring and summer when fish were age 0. Waterlevel fluctuation in this Tennessee reservoir played a pivotal role in regulating year-class strength of most sport fish species. Attempts to enhance year-class strength of fishes in tributary storage impoundments should focus on altering the hydrology of systems.

Weight-length data from 50 populations of smallmouth bass Micropterus dolomieu (N = 6,731) in 19 states were used to develop a revised standard weight (WS) equation for smallmouth bass . The regression-linepercentile (RLP) technique was used to develop the proposed 75th-percentile Ws equation from length-weight regressions for individual smallmouth bass populations . The proposed Ws equation, log10 Ws (weight, g) = -5 .329 + 3.200 log10L(total length, mm), is valid for fish 150 mm long and longer . The English-unit equivalent, log10 Ws (lb) = -3 .491 + 3.200 log10 L(total length, in), is valid for fish 6 in long and longer.

Dos Bocas Reservoir, Puerto Rico, has pronounced in-lake variability in fish distributions, especially in piscivore abundance, between the two primary reservoir basins. We quantified fish community distributions by electrofishing in each basin and the confluence, and assessed water quality, contaminant concentrations, habitat availability, and habitat selection. Fish community composition varied markedly among the three areas. We found almost no largemouth bass (Micropterus salmoides) in Basin 1 (0.5 fish/h), moderate catch rates in the Confluence (11 fish/h), and relatively high catches in Basin 2 (35 fish/h; ANOVA, P = 0.005). We detected significant differences in pH, conductivity, and Secchi depth (Paired t-Tests, P < 0.05), but none were outside of the range suitable to most fish species. Analysis of common chemical contaminants including polychlorinated biphenyl (PCB) congeners, common pesticides, and mercury revealed little to explain the unusual distributions. When radio-tagged naive largemouth bass (n = 6) from another reservoir were released in Basin 1, they quickly abandoned Basin 1 and were located 11 days later in the Confluence and Basin 2 where they remained for the duration of the study. Radio-tagged largemouth bass (n = 6) released in Basin 2 remained near their stocking site. We hypothesize that differences in watershed development may result in short-term water quality events, including high sedimentation and possibly acidification of Basin 1. These short-term events may contribute to variation in fish assemblages. We recommended focusing on largemouth bass management within Basin 2 and promoting fisheries for Tilapia, sunfish, and crappie in Basin 1.

Three Oregon reservoirs were evaluated for environmental parameters affecting mercury (Hg) dynamics and bioaccumulation in fish using an ecoregion approach. Ecoregions are distinguished by topography, geology, soil type and composition, and land use patterns. We examined: pH, dissolved oxygen, hardness, conductivity and concentration of Hg ([Hg]) in water; and complexing agent concentrations, organic content, inorganic and organic [Hg] in sediments; and [Hg] in three fish species. [Hg] in water was below detection (0.1 txg/L) in most water samples from the three reservoirs; in samples above detection, we reasoned that Hg was predominantly in the particulate fraction. Hg in sediment was only found consistently in the inorganic state; organic mercury was below detection (0.2 ng/g) in 83% of sediment samples. Muscle [Hg] in fish over 4 years old was above the FDA limit of 1.0 tzg/g wet weight, and more than 90% of the Hg in all fish was organic mercury. [Hg] in lateral muscle was similar between smallmouth bass (Micropterus dolomieu) in Owyhee Reservoir and largemouth bass (Micropterus salmoides) in Cottage Grove Reservoir; rainbow trout (Salmo gairdneri) from Ochoco Reservoir had significantly lower levels of Hg. It is concluded that, although ecoregion parameters alone do not explain mercury dynamics, they may influence the methylation rate in areas of similar Hg loading rates.

Winter severity (temperature, duration, and photocycle), geographic origin, food availability, and initial body size likely influence growth, survival, and, therefore, recruitment of age-0 largemouth bass Micropterus salmoides. We collected age-0 largemouth bass (70-160 mm total length) from low (33ЊN), intermediate (40ЊN), and high (45ЊN) latitudes throughout their natural range (origin), and we subjected all three groups of fish to three experimental winters that mimicked these latitudes (N ϭ 9 largemouth bass per treatment). Within each winter and origin, one-half of the largemouth bass were fed fish prey, whereas the remaining one-half were starved. Winter strongly influenced survival; overall survival rates in the high-, intermediate-, and low-latitude winters were 34.9, 59.4, and 61.1%, respectively (2 test, P Ͻ 0.05). Largemouth bass from 33ЊN suffered high mortality in the high-latitude winter. Across all winters, more fed fish (64.5%) survived than did starved fish (38.1%) (2 test, P Ͻ 0.05). Pooling fish into small (Ͻ100 mm) and large (Ն100 mm) size classes revealed that more small fish died than did large fish in the low-and high-latitude winters, but this was not the case in the middle-latitude winter. Wet weights (g) of fed largemouth bass increased, remained constant, and declined in the low-, intermediate-, and high-latitude winters, respectively. Wet weights and total energy content (kJ) of fed individuals were consistently higher than those of their starved counterparts in all winters. However, energy density (kJ/g) of fed individuals often declined to levels similar to those of starved largemouth bass. Winter temperature combined with duration likely dictate the northern limit of largemouth bass by reducing growth, even when food is abundant. Because survival of individuals from the low latitude was poor in higher latitude winters, stocking southern largemouth bass in northern systems may translate to high mortality and perhaps to degradation of physiological tolerances of local populations through hybridization.

We developed a linear discriminant function (LDF) using surface area, mean depth, fetch, and three substrate descriptors to discriminate the presence and absence of walleyes Sander vitreus (formerly Stizostedion vitreum) in 120 northern Wisconsin lakes. The resulting LDF correctly classified 90% of walleye lakes and 85% of nonwalleye lakes. For model validation, the model classified 90% of walleye lakes and 93% of nonwalleye lakes in an independent set of 100 randomly selected lakes. In contrast, within walleye lakes, an LDF using the same variables correctly classified only 60% of 30 self-sustaining walleye lakes and 50% of 30 stocked walleye lakes. For model validation, the model classified 30% of self-sustaining walleye lakes and 73% of stocked walleye lakes in an independent set of 40 randomly selected lakes. To further assess the differences between walleye lakes with self-sustaining and stocked populations, the angler catch rates for largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, northern pike Esox lucius, and muskellunge E. masquinongy obtained from creel surveys during 1990-2001 were analyzed by means of a principal components analysis. The first principal component explained 29% of the variation and represented a linear contrast between the relative abundance of walleyes and muskellunge and the relative abundance of largemouth bass and northern pike. High largemouth bass and northern pike densities characterized lakes with stocked walleye populations, whereas high walleye and muskellunge densities characterized lakes with self-sustaining walleye populations. We conclude that physical features may be used to discriminate lakes where walleyes presently occur from lakes where walleyes do not presently occur, and that fish community differences exist between stocked and self-sustaining walleye populations in northern Wisconsin.

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Weight-length data from 50 populations of smallmouth bass Micropterus dolomieu (N = 6,731) in 19 states were used to develop a revised standard weight (WS) equation for smallmouth bass. The regression-linepercentile (RLP) technique was used to develop the proposed 75th-percentile Ws equation from length-weight regressions for individual smallmouth bass populations. The proposed Ws equation, log10 Ws (weight, g) =-5 .329 + 3.200 log10L(total length, mm), is valid for fish 150 mm long and longer. The English-unit equivalent, log10 Ws (lb) =-3 .491 + 3.200 log10 L(total length, in), is valid for fish 6 in long and longer.

The influence of rapid temperature change on the swimming performance of three warmwater fishes was considered. Juvenile largemouth bass (Micropterus salmoides), spotfin shiners (Notropis spilopterus), and channel catfish (Ictalurus punctatusJ collected in 27-31 C ambient lake water were immediately exposed to temperatures ranging from 15 to 35 C at 5 C intervals for 14-20 hours before testing. Exposure to rapid changes in temperature resulted in decreased swimming performance of each species for temperatures other than ambient.

Growth of sympatric populations of three important sport fish species: bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides and channel catfish Ictalurus punctatus, in 14 Illinois reservoirs was assessed in an attempt to relate size-specific growth to environmental conditions. Multiple regression relationships for most species and size classes explained a large percentage of the variation in growth. Growth of small bluegill (50 mm total length, L T ) showed a strong negative relationship with bluegill catch per unit effort (cpue), per cent littoral area and pH. Large bluegill (150 mm L T ) growth was negatively related to Daphnia spp. and benthic macroinvertebrate abundance and lake volume, and positively related to bluegill cpue. Growth of small (100 mm L T ) and large (250 mm L T ) largemouth bass was not well explained by any of the measured variables. Growth of both small (300 mm L T ) and large (450 mm L T ) channel catfish was strongly positively related to forage fishes and ichthyoplankton abundance, and per cent littoral area while negatively related to benthic macroinvertebrates. By identifying environmental conditions associated with increased growth rates, these models provide direction for managing fish populations and suggest testable hypotheses for future study of the complex interactions between environmental conditions and growth.

The purpose of this study was to quantify total mercury concentrations in three species of fish in three lakes of western Maryland: Piney Creek reservoir, Deep Creek Lake, and Lake Habeeb. We measured total mercury concentrations in water from each lake and muscle tissue from 119 fish collected in fall 2000: 15 largemouth bass (Micropterus salmoides), 15 yellow perch (Perca flavescens), and 15 bluegill (Lepomis macrochirus) from the Piney Creek reservoir; 15 largemouth bass, 15 yellow perch, and 14 bluegill from Deep Creek Lake; and 15 largemouth bass and 15 bluegill from Lake Habeeb. Average total mercury concentrations (Ϯ SD) in surface waters were 0.96 Ϯ 0.03 ng L Ϫ1 for the Piney Creek reservoir, 0.56 Ϯ 0.07 ng L Ϫ1 for Deep Creek Lake, and 0.40 Ϯ 0.05 ng L Ϫ1 for Lake Habeeb. These water quality differences were sometimes reflected in the total mercury concentration in fish muscle tissue. Total mercury concentrations in bluegill (0.05 Ϯ 0.02 g g Ϫ1) and largemouth bass (0.10 Ϯ 0.03 g g Ϫ1) from Lake Habeeb were significantly (p Ͻ 0.001) lower than the total mercury concentrations in bluegill and largemouth bass from the Piney Creek reservoir (bluegill: 0.13 Ϯ 0.04 g g Ϫ1 and largemouth bass: 0.37 Ϯ 0.18 g g Ϫ1) and Deep Creek Lake (bluegill: 0.11 Ϯ 0.04 g g Ϫ1 and largemouth bass: 0.30 Ϯ 0.09 g g Ϫ1). Yellow perch from the Piney Creek reservoir had significantly higher total mercury concentrations than yellow perch from Deep Creek Lake (0.20 Ϯ 0.08 g g Ϫ1 versus 0.13 Ϯ 0.04 g g Ϫ1). In contrast, total mercury concentrations in largemouth bass from the Piney Creek reservoir and Deep Creek Lake were not significantly different. With the exception of largemouth bass from Lake Habeeb and yellow perch from Deep Creek Lake, there were relatively strong (r 2 Ͼ 0.39-0.79) log-log relationships between the size (weight and length) of the fish and total mercury concentrations in muscle tissue. The largest largemouth bass (Ͼ 800 g and Ͼ 38 cm) from both Deep Creek Lake and the Piney Creek reservoir had total mercury concentrations that exceeded the consumption advisory of 0.5 g g Ϫ1 that is used by many states and Canada. In contrast, total mercury concentrations in largemouth bass from Lake Habeeb did not exceed this consumption advisory. Our results suggest that fish consumption advisories are needed for largemouth bass in the Piney Creek reservoir and Deep Creek Lake.

There is a need to quantify the multivariate quality of a recreational fishery at the site scale to better communicate the relative quality among sites to the public and anglers. Borrowing on the general approach of multimetric indices of biotic integrity (IBIs), we developed fishery quality indices (FQIs) from species quality indices (SQIs) based on measures of fish abundance and size structure for northern and central Portuguese streams. Our FQIs showed regional patterns indicating a range in fishery quality. Higher coldwater FQI scores were mostly found in the northwestern (Minho and Lima), northeastern Douro, and northern Tagus basins. Higher warmwater FQI scores occurred in the eastern Tagus basin. The species that contributed the most to warmwater FQI scores were largemouth bass Micropterus salmoides, pumpkinseed Lepomis gibbosus, the cyprinid Luciobarbus bocagei, chubs Squalius carolitertii and S. pyrenaicus, and nases Pseudochondrostoma duriense and P. polylepis. The chubs, nases, and brown trout Salmo trutta contributed the most to coldwater FQI scores. As expected, our indices were correlated with river size and with disturbance at the catchment, segment, and site scales. Regression models for separate coldwater and warmwater FQIs were stronger than those for the individual SQIs and for an all-site FQI. The correlation was positive between the coldwater FQI and a coldwater IBI but negative between the warmwater FQI and warmwater IBIs. The proposed FQIs offer a quantitative approach for assessing relative fishery quality among sites and for making regional assessments given an appropriate study design. The component SQIs and SQI metrics of the FQIs can be disassociated to determine the population and species characteristics most affected by various environmental variables.

The effect of salinity on survival, osmoregulation and oxygen consumption was determined on coastal young-of-the-year (YOY) largemouth bassMicropterus salmoides by exposing them to saline media of 0, 4, 8, 12, and 16‰. The data indicated a decrease in survival with longer exposure time and increased salinity. There were no significant differences in plasma osmolality with increased salinity from 0 to 8‰ but osmolality was significantly greater at 12‰ than 0‰ and osmolality from 16‰ was greater than all other salinity treatments. No significant differences in hematocrits were detected between 0 and 12‰, but hematocrits in the 16‰ treatment were significantly reduced compared to all other treatments. YOYM. salmoides are good osmoregulators up to 8‰ but increased salinity caused measurable osmoregulatory dysfunction. Oxygen consumption rate increased significantly as salinity increased, suggesting that adaptation of this species to hypersaline media is in part accompanied by increased ...

The mechanisms by which outbreeding depression leads to reduced fitness are poorly understood. We considered the hypothesis that outbreeding can depress fitness by increasing the susceptibility of hybrid individuals and populations to infectious disease. Competitive breeding trials in experimental ponds indicated that outbred largemouth bass (Micropterus salmoides) crossed from two geographically and genetically distinct populations suffered a reduction in fitness of approximately 14% relative to parental stocks. We measured the comparative susceptibility of these same outbred stocks to a novel viral pathogen, largemouth bass virus. Following experimental inoculation, F2 generation hybrids suffered mortality at a rate 3.6 times higher than either F1 generation hybrids or wild-type parental fish. Analysis of viral loads indicated that viral replication was more rapid in F2 fish than in F1 hybrids or wild-type parental fish. We attribute these results to the disruption of coadapted gene complexes in the immune systems of outbred fish in the F2 generation. Increased susceptibility to infectious disease may be an important but underappreciated mechanism by which outbreeding reduces the fitness of individuals and populations and by which novel infectious diseases emerge in populations of hybrid organisms.

The heat-shock protein or stress-70 family was isolated from catfish liver. The homogeneity of the purified protein was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Fish subjected to whole-body hyperthermia contained the constitutive and the heat-inducible stress-70 with approximate molecular weights of 70 and 68 kDa, respectively. The final purification product from livers of catfish raised under normal temperature was only the constitutive stress-70. Western blot analysis with rabbit antiserum prepared against purified catfish (Zctaluruspunctatus) liver stress-70 showed that the antibody cross-reacted with liver, muscle, and gill tissue homogenates of fathead minnows (Pimephalespromelas), red shiners (Cyprinella lutrensis), black bass (Micropterus sulmoides), and bluegill (Lepomis macrochirus), with various intensities suggesting that stress-70s from different tissues of various fish species share common antigenic determinants of the protein. This substantiates that the antigedantibody approach of stress-70 is useful as a stress indicator and, consequently, as a potential biomarker for water quality.

Lake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. They are Oreochromis leucostictus, Tilapia zillii, Micropterus salmoides (largemouth bass), Barbus amphigramma and Poecilia reticulata (guppy). The first three of these form the basis of an important gill net fishery and bass are also taken by rod and line for sport. Barbus are occasionally caught by dip net. Actual and potential yields for the Lake Naivasha fishery are discussed and the fishery is shown to be under-performing. The feeding regimes of the commercially exploited fish were examined in the context of available food supply, in particular the benthic fauna. Small bass depend heavily on Micronecta and large bass mostly take crayfish. Detritus predominates in the diet of Oreochromis leucostictus and Tilapia zillii but the former also eats algae and the latter, Micronecta and macrophyte. Various food resources, especially the benthos, appear to be under-utilized and so it is possible that further species could be introduced to enhance the commercial fishery.

Biological invasions are a major factor for biodiversity loss, particularly in freshwater environments. Largemouth bass Micropterus salmoides is native to North America and is invasive on the Iberian Peninsula, primarily to provide angling opportunities in reservoirs. However, this species is a threat to the endemic Iberian fauna via predation and competition. Currently, there is little information on largemouth bass in European streams. Thus, we assessed the trophic plasticity and body condition of young largemouth bass in both invasive (the regulated Bullaque River) and native (Murray Creek) streams. Abundance of juvenile largemouth bass, percentage of full stomachs and body condition were higher in Bullaque River. Largemouth bass preyed on benthic invertebrates much more heavily in the Bullaque River, whereas fishes were the most important prey in Murray Creek. Prey richness, diet diversity and trophic niche breadth were higher in the Bullaque River population. Largemouth bass preferred water-column fishes as prey and avoided consuming benthic fishes in Murray Creek, whereas water-column fishes were avoided in Bullaque River. These results demonstrate that largemouth bass display substantial trophic plasticity which possibly facilitates its success as invasive species. Regulated Iberian streams may provide both suitable food and habitat resources with minimal predation pressure, and hence may serve as recruitment sources for this invasive fish.

We compared growth and survival (including losses to stocking stress and predation) of four sizes of largemouth bass Micropterus salmoides in four Illinois reservoirs. Fish were stocked as small fingerlings (55 mm total length) in July, medium fingerlings (100 mm) in August, large fingerlings (150 mm) in September, and advanced fingerlings (200 mm) the subsequent spring. Survival of small fingerlings was very low (catch per unit effort , 1 fish/h of electrofishing in the fall after stocking), and fish stocked as small fingerlings were not observed in electrofishing samples after the spring following stocking. In samples collected soon after stocking, large and advanced fingerlings were larger and more abundant than other sizes. However, in subsequent sampling, there were no differences in size or survival among fish stocked as medium, large, and advanced fingerlings. Long-term growth of stocked fish was similar to that of wild fish, but survival of stocked fish was low for all sizes. Mean initial stocking mortality for fish held in cages was variable but generally low (0.0-5.6%) and was related to lake temperature at stocking. The diets of predators (primarily adult largemouth bass) contained high numbers of small-, medium-, and large-sized fingerlings after stocking, but no predation was observed on advanced fingerlings. Cost of producing fish increased with size, and cost-benefit analysis determined that medium (100-mm) fish had the greatest return per cost. We recommend stocking medium fingerlings because the stocking of larger fingerlings did not produce a significant increase in survival.

Teleost retinas adapted to light show numerous spinules invaginated in the cone pedicles and small nematosomes in the distal horizontal cells. Darkness induces the dissolution of spinules and the presence of large and numerous nematosomes. The aim of this work is to study the influence of optic nerve integrity on spinule formation/dissolution and changes in nematosome size during light or dark adaptation of black bass (Micropterus salmoides) retinas. Eyes from fish, dark-or light-adapted, were removed and the eyecups placed in oxygenated Ringer's solution and immediately exposed to light or dark, respectively, for 1 h. The number of spinules per pedicle and the nematosome diameter were measured on electron micrographs. Isolation of eyecups in the dark, impaired both spinule formation and nematosome size reduction when they were superfused in light. In the same way, isolation of eyecups in the light, impaired both spinule dissolution and nematosome size increase when they were superfused in dark. No significant differences in spinule number and nematosome size, following dopamine superfusion, were found in comparison to retinas supeffused with Ringer's solution only. Our results suggest: (1) optic nerve integrity is necessary to yield spinule formation/disruption and changes in nematosome size during light or dark adaptation. (2) dopamine does not appear to be the primary agent responsible for spinule formation.

Lake consumers are supported by autochthonous organic matter produced by photosynthesis within the aquatic ecosystem and imported allochthonous material produced outside the ecosystem. To evaluate carbon sources that support fish growth, we enriched a 26 ha lake with inorganic 13 C. This labeled the autochthonous primary production and allowed us to determine the extent to which invertebrates in fish diets were supported by this autochthonous carbon. Fish autochthony was defined as the proportion ranging from 0 to 1 of fish growth derived from aquatic primary production. This proportion was calculated using the weighted average of each diet taxas contribution to fish growth along with the autochthony of diet taxa estimated with dynamic models of d 13 C time series. Age 0 bluegill (Lepomis macrochirus) and yellow perch (Perca flavescens) had the highest autochthony (0.56, 0.57, respectively) because of greater use of zooplankton that were highly dependent on phytoplankton. Older fishes (age 1 and above) of all species had similar estimates of autochthony (mean = 0.47 standard deviation = 0.04) derived from feeding on either benthic invertebrates or other fishes. Proportional contribution of terrestrial prey (primarily terrestrial beetles) to fish growth was highest for bluegill (0.07-0.22) and substantially lower (<0.04) for largemouth bass (Micropterus salmoides) and yellow perch. Across species and ages~45 % of fish growth could not be attributed to terrestrial prey items or current autochthonous primary production. This residual detrital carbon source is a mixture of allochthonous material and autochthonous material derived from primary production prior to the 13 C addition. Fish growth and production in the study lake were not tightly coupled to the current seasons primary production. Nearly half of the organic carbon supporting fish growth came from prior autochthonous primary production or allochthonous sources.

We describe 10 microsatellite loci from bluegill (Lepomis macrochirus) and discuss their evolution within the Centrarchidae. All of the loci exhibit Mendelian inheritance and are unlinked. While six loci are conserved within the Centrarchidae (found also in pumpkinseed (Lepomis gibbosus) and largemouth bass (Micropterus salmoides)), four have origins outside the family and two predate it by 65-150 million years. The persistence of these loci in fish may be due to a slow rate of sequence divergence within their flanking sequences, estimated at 0.14-0.83% per million years. We examine the number of alleles, heterozygosity, range, modes, and the frequency of the most common allele and find that a two-phased model (TPM) or an infinite alleles-model (IAM) best describes the results, while a stepwise mutation model (SMM) is rejected. Therefore, population differentiation analyses utilizing these microsatellite loci should consider parameters based on the IAM (e.g., F ST) and not the SMM. Résumé : Nous décrivons 10 loci microsatellites du crapet arlequin (Lepomis macrochirus) et traitons de leur évolution au sein des Centrarchidae. Tous les loci obéissent à l'hérédité mendélienne et ne sont pas liés. Six loci sont conservés au sein des Centrarchidae (présents aussi chez le crapet-soleil (Lepomis gibbosus) et l'achigan à grande bouche (Micropterus salmoides)), tandis que quatre ont leur origine à l'extérieur de la famille, dont deux existaient 65 à 150 millions d'années avant l'apparition de cette dernière. La persistance de ces loci chez les poissons pourrait être attribuable à un faible taux de divergence des séquences dans leurs régions flanquantes, estimé à 0,14-0,83% par million d'années. Nous examinons le nombre d'allèles, l'hétérozygosité, la diversité des allèles, les modes et la fréquence de l'allèle le plus commun pour conclure qu'un modèle diphasé ou un modèle en nombre infini d'allèles donnent la meilleure description des résultats et qu'on doit rejeter le modèle de mutation par pas. Ainsi, les analyses de différenciation des populations utilisant ces loci microsatellites devraient considérer les paramètres fondés sur le modèle en nombre infini d'allèles (p. ex. F ST) et non sur le modèle de mutation par pas.

Micropterus salmoides is a North American piscivorous fish on the IUCN list of 100 of the world's worst invasive alien species. Introduced into Lake Naivasha (Kenya) in 1929, their current population abundance is significantly depressed in a lake that has recently become dominated by fishes of the Cyprinidae family; the introduced cyprinid Cyprinus carpio now dominates catches in the commercial fishery and Barbus paludinous is now numerically dominant in the fish community. Long-term diet studies of M. salmoides based on gut contents

Genetic diversity and divergence patterns of smallmouth bass Micropterus dolomieu spawning groups are analysed across its northern native range with mtDNA cytochrome b gene sequences and eight unlinked nuclear DNA microsatellite loci. Results reveal high levels of genetic variability and significant differences in allelic representation among populations (mtDNA: mean ± s.e., H D = 0·50 ± 0·06, mean ± s.e., í µí¼ƒ ST = 0·41 ± 0·02 and microsatellites: mean ± s.e. H O = 0·46 ± 0·03, mean ± s.e. í µí¼ƒ ST = 0·25 ± 0·01). The distributions of 28 variant mtDNA haplotypes, which differ by an average of 3·94 nucleotides (range = 1–8), denote divergent representation among geographic areas. Microsatellite data support nine primary population groups, whose high self-assignment probabilities likewise display marked divergence. Genetic patterns demonstrate: (1) high genetic diversity in both genomes, (2) significant divergence among populations, probably resulting from natal site homing and low lifetime migration, (3) support for three post-glacial refugia that variously contributed to the current northern populations, which remain evident today despite waterway connectivity and (4) a weak yet significant genetic isolation by geographic distance pattern, indicating that other processes affect the differences among populations, such as territoriality and site fidelity.

Water turbidity has the capacity to influence fish foraging success and behavior. The largemouth bass Micropterus salmoides is a popular sport fish in the southeastern United States that is primarily a visual predator. The high turbidity in many systems can be attributed to sediment loading from agricultural lands, and it can reduce the availability of light in the water column and have direct impacts on largemouth bass foraging success. We investigated the effect of different turbidity levels (0, 10, 25, 50, 100, and 250 nephelometric turbidity units [NTU]) on largemouth bass foraging in aquaria by testing the hypothesis that turbidity has no effect on the time required to locate tethered prey (fathead minnow Pimephales promelas and golden shiner Notemigonus crysoleucas) or ultimate capture success. The percentages of prey captured that were derived from aggregated data in multiple trials at the different treatment levels differed significantly. One-hundred percent of the largemouth bass in the 0-NTU treatments captured the prey. Conversely, only 15% of the largemouth bass in the 250-NTU treatments captured the prey throughout all trials. The average time taken to capture the prey also was significantly different between treatment combinations, with time to interaction increasing as turbidity increased. The results from this study suggest that greater turbidity levels reduce the ability of largemouth bass to capture prey and increase the time taken to locate and interact with prey. Thus, turbidity may impact individual fitness and management strategies.Received April 1, 2011; accepted June 20, 2011

Genetic diversity and divergence patterns of smallmouth bass Micropterus dolomieu spawning groups are analysed across its northern native range with mtDNA cytochrome b gene sequences and eight unlinked nuclear DNA microsatellite loci. Results reveal high levels of genetic variability and significant differences in allelic representation among populations (mtDNA: mean ± s.e., HD = 0·50 ± 0·06, mean ± s.e., θST = 0·41 ± 0·02 and microsatellites: mean ± s.e. HO = 0·46 ± 0·03, mean ± s.e. θST = 0·25 ± 0·01). The distributions of 28 variant mtDNA haplotypes, which differ by an average of 3·94 nucleotides (range = 1-8), denote divergent representation among geographic areas. Microsatellite data support nine primary population groups, whose high self-assignment probabilities likewise display marked divergence. Genetic patterns demonstrate: (1) high genetic diversity in both genomes, (2) significant divergence among populations, probably resulting from natal site homing and low lifetime migration, (3) support for three post-glacial refugia that variously contributed to the current northern populations, which remain evident today despite waterway connectivity and (4) a weak yet significant genetic isolation by geographic distance pattern, indicating that other processes affect the differences among populations, such as territoriality and site fidelity.

SUMMARYSuction feeding fish differ in their capacity to generate subambient pressure while feeding, and these differences appear to relate to morphological variation. We developed a morphological model of force transmission in the fish head and parameterized it with measurements from individual fish. The model was applied to 45 individuals from five species of centrarchid fishes: Lepomis macrochirus, Lepomis punctatus, Lepomis microlophus, Micropterus salmoides and Pomoxis nigromaculatus. Measurements of epaxial cross-sectional area, epaxial moment arm, buccal area and buccal area moment arm were combined to estimate pressure generation capacity for individual fish. This estimation was correlated with pressure measured in fish feeding on elusive prey to test the model&#39;s ability to predict pressure generation from morphology. The model explained differences in pressure generation found among individuals (P&lt;0.001, r2=0.71) and produced a realistic estimate of normalized muscle ...

The rates of accumulation and subsequent loss of stable cesium (¹³³Cs) by organisms at different trophic levels within plankton-based and periphyton-based food chains were measured following the addition of ¹³³Cs into a small reservoir near Aiken, South Carolina, USA. An uptake parameter u (L kg⁻¹ d⁻¹ dry mass) and a loss rate parameter k (d⁻¹) were estimated for each organism using time-series measurements of ¹³³Cs concentrations in water and biota, and these parameters were used to estimate maximum concentrations, times to maximum concentrations, and concentration ratios (C(r)). The maximum ¹³³Cs concentrations for plankton, periphyton, the insect larva Chaoborus punctipennis, which feeds on plankton, and the snail Helisoma trivolvis, which feeds on periphyton, occurred within the first 14 days following the addition, whereas the maximum concentrations for the fish species Lepomis macrochirus and Micropterus salmoides occurred after 170 days. The C(r) based on dry mass for plankton and C. punctipennis were 1220 L kg⁻¹ and 5570 L kg⁻¹, respectively, and were less than the C(r) of 8630 L kg⁻¹ for periphyton and 47,700 L kg⁻¹ for H. trivolvis. Although the C(r) differed between plankton-based and periphyton-based food chains, they displayed similar levels of biomagnification. Biomagnification was also indicated for fish where the C(r) for the mostly nonpiscivorous L. macrochirus of 22,600 L kg⁻¹ was three times less than that for mostly piscivorous M. salmoides of 71,500 L kg⁻¹. Although the C(r) for M. salmoides was greater than those for periphyton and H. trivolvis, the maximum ¹³³Cs concentrations for periphyton and H. trivolvis were greater than that for M. salmoides.

Suction feeding in fishes is the result of a highly coordinated explosive expansion of the buccal cavity that results in a rapid drop in pressure. Prey are drawn into the mouth by a flow of water that is generated by this expansion. At a gross level it is clear that the expansion of the buccal cavity is responsible for the drop in pressure. However, attempts using high-speed video recordings to demonstrate a tight link between prey capture kinematics and suction pressure have met with limited success. In a study with largemouth bass Micropterus salmoides, we adopted a new technique for studying kinematics, sonomicrometry, to transduce the movement of skeletal elements of the head during feeding, and synchronized pressure recordings at a sampling rate of 500 Hz. From the positional relationships of six piezoelectric crystals we monitored the internal movements of the buccal cavity and mouth in both mid-sagittal and transverse planes. We found that peak subambient pressure was reached...

Microarrays enable gene transcript expression changes in near-whole genomes to be assessed in response to environmental stimuli. We utilized oligonucleotide microarrays and subsequent gene set enrichment analysis (GSEA) to assess patterns of gene expression changes in male largemouth bass (Micropterus salmoides) hepatic tissues after a 96 h exposure to common environmental contaminants. Fish were exposed to atrazine, cadmium chloride, PCB 126, phenanthrene and toxaphene via intraperitoneal injection with target body burdens of 3.0, 0.00067, 2.5, 50 and 100 mg g-1 , respectively. This was conducted in an effort to identify potential biomarkers of exposure. The expressions of 4, 126, 118, 137 and 58 mRNA transcripts were significantly (P Յ 0.001, fold change Ն2¥) affected by exposure to atrazine, cadmium chloride, PCB 126, phenanthrene and toxaphene exposures, respectively. GSEA revealed that none, four, five, five and three biological function gene ontology categories were significantly influenced by exposure to these chemicals, respectively. We observed that cadmium chloride elicited ethanol metabolism responses, and along with PCB 126 and phenanthrene affected transcripts associated with protein biosynthesis. PCB 126, phenanthrene and toxaphene also influenced one-carbon compound metabolism while PCB 126 and phenanthrene affected mRNA transcription and mRNA export from the nucleus and may have induced an antiestrogenic response. Atrazine was found to alter the expression of few hepatic transcripts. This work has highlighted several biological processes of interest that may be helpful in the development of gene transcript biomarkers of chemical exposure in fish.