Adult lake sturgeon (Acipenser fulvescens Rafinesque, 1817) occurrence in the Muskegon River system,a Lake Michigan drowned river mouth,USA

Recent advancements in telemetry have allowed managers and researchers to conduct comprehensive studies on the movement ecology of lake sturgeon (Acipenser fulvescens), a species of conservation concern in most of the Laurentian Great Lakes basin. In Michigan waters of Lake Michigan, drowned river mouth systems (a protected lake-like habitat that connects a river to lake) support 4 of 11 remaining lake sturgeon populations. One of those remnant populations is supported by the Muskegon River, a drowned river mouth system consisting of both Muskegon Lake and the Muskegon River. The objectives of this 6-year telemetry study were to determine whether adult lake sturgeon occupied the Muskegon River system outside of the spawning season (defined as March to July), to quantify their use of the system annually, and to identify and characterize patterns in occurrence. A total of 21 adult lake sturgeon implanted with acoustic transmitters were passively monitored throughout the year during 2012–2017. Eighty-two percent of tagged fish at large were detected ≥1 day in the Muskegon River system annually, and tagged lake sturgeon were frequently detected during both spawning and non-spawning time periods. Residency index (i.e., no. detection days/365 days) values indicated that adult lake sturgeon were not only detected throughout the year but that they occupied the Muskegon River system for an average of 130 days each year (residency index = 0.36 ± 0.05 SE) during our most spatially intensive acoustic monitoring in 2016–2017. Additionally, 24% of tagged lake sturgeon were primary residents (i.e., residency index >0.5) of the Muskegon River system in both years. Adult lake sturgeon followed 1 of 3 patterns of occurrence based on individual detection histories, and those patterns varied temporally and by the relative amount of use (i.e., high, medium, and low). Our findings build on previous research that found drowned river mouth systems in Lake Michigan can be important nursery habitats for juvenile lake sturgeon by showing that these habitats also can be used extensively by adult lake sturgeon throughout the year.     

Larval habitat duration and size at metamorphosis in frogs

The relationship between size at metamorphosis and adult size was studied in 12 closely-related species of frog from Malawi (Central Africa). These species of frogs breed in water of different durations, and occupy different habitats as adults. We could demonstrate no correlation between size at metamorphosis and size of adults when frogs were divided into groups on the basis of occupying similar habitats as adults, but when frogs were divided into groups on the basis of similar duration of larval habitat we demonstrated a strong correlation between size at metamorphosis and adult size. Thus we suggest that duration of the larval habitat is a major determinant of size at metamorphosis, with species which breed in the more temporary habitats metamorphosing at smaller size than species which breed in more permanent habitats, but which are of similar size as adults. Such manipulation of the life cycle appears to be adaptive since it results in individuals becoming independent of water earlier when the likelyhood of early loss of larval habitat is high.     

Is the island biogeography model a poor predictor of biodiversity patterns in shallow lakes?

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Temporal consistency of ontogenetic shifts in habitat use by coral reef fishes in the northernmost coral ecosystem in the world (Kudaka Island, Japan)

The prevalence of major habitat shifts in tropical fishes between juvenile and adult stages (ontogenetic shifts) in one of the northernmost coral reefs in the world (Kudaka Island, Japan) is given. The comparative analysis of spatial distribution of juveniles v . adults highlighted four ontogenetic patterns: no change in habitat use between juveniles and adults (five species), a decrease in the number of habitats used by adults compared to juveniles (three species), an increase in the number of habitats used during the adult stage (four species) and use of nursery areas by juveniles followed by extensive movements to different adult habitats (three species). The comparative analysis of fish distribution over time ( i.e. during three consecutive settlement months) showed that 84% of species had temporal consistency in ontogenetic patterns of habitat use.     

Spatial autocorrelation and dispersal limitation in freshwater organisms

Dispersal can limit the ranges of species and the diversity of communities. Despite its importance, little is known about its role in freshwater habitats and its relation to habitat type (lentic vs. lotic), especially for organisms with cryptic dispersal methods such as plankton. Poor dispersers are expected to show more clumped distributions or greater spatial autocorrelation (SA) in community composition than good dispersers. We examined patterns of SA across freshwater taxa with different dispersal modes (active vs. passive) and their association with habitat type (lake vs. stream) using 18 spatially explicit community composition data sets. We found significant relationships between SA and body size among taxa in lake habitats, but not in streams. However, the increase in SA with body size in lakes was driven entirely by fishes—organisms ranging in size from diatoms to macro-invertebrates showed equivalent levels of SA. These results support the idea that large organisms are less effective dispersers in aquatic environments, resulting in greater SA in community structure over broad scales. Streams may be effectively more connected than lakes as patterns of SA and body size were weaker in lotic habitats. Our data suggest that the critical threshold where greater body size increases dispersal limitation seems to come at the juncture between invertebrates and vertebrates rather than that between unicellular and multicellular organisms as has been previously suggested. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Seasonal variation in the diet of juvenile lake sturgeon,Acipenser fulvescens,Rafinesque, 1817, in the Winnipeg River,Manitoba, Canada

The lake sturgeon, Acipenser fulvescens, is a threatened species across most of its range. To understand any potential shifts in diet across season or habitat, stomach contents were examined from juvenile lake sturgeon caught in the Winnipeg River, Manitoba, Canada. This information will aid in assessment of environmental impacts and conservation initiatives for this threatened species. From 2006 to 2008 gut contents were collected from juvenile lake sturgeon using a non‐lethal gastric lavage methodology. Juvenile lake sturgeon were sampled from four discrete deep water habitat types (13.7–27.4 m depths), during the months of May, June, July and October. In total, 13 066 prey items belonging to 14 prey groups were collected from 345 juvenile lake sturgeon (251–835 mm TL). Overall, juvenile lake sturgeon consumed a low diversity of organisms; insect larvae from three invertebrate orders, Trichoptera, Diptera and Ephemeroptera, accounted for 97.4% of the total numeric abundance of prey items recovered. A relationship between size of juvenile lake sturgeon and prey quantity or type was not observed. Diet of juvenile lake sturgeon varied in relation to season, with Diptera (77.6%) being the most abundant prey in May, Trichoptera the most abundant in June (n = 3,056, 60.4%) and July (n = 2,055, 52.6%). During October, 96% of stomachs examined were empty. In terms of habitat type, the standardized abundance of invertebrate prey items was highest in deep water habitats characterized by medium water velocity (depths > 13.7 m) and coarse substrate (particle sizes > 0.063 mm) in May and June when compared to deep water habitats characterized by low water velocity (<0.2 m.s^?1) and fine substrate (particle sizes < 0.063 mm). However, in July, the opposite was observed and prey abundance in juvenile lake sturgeon stomachs decreased with increasing particle size. Results suggest a high degree of dietary overlap among juvenile lake sturgeon from multiple size/age classes occupying deep‐water habitats of the Winnipeg River.     

Sexual differences in growth strategies of the wolf spider Hygrolycosa rubrofasciata

In invertebrates, the size at maturation is considered to be important for adult fitness. In the wolf spider Hygrolycosa rubrofasciata, however, it is only females that clearly benefit of larger size through augmented egg production, while male mating success is determined by display activity not related to size. Thus, we can expect conflicting growth patterns for the sexes. Additionally, populations differ greatly in adult size: individuals from dry habitats are smaller than those from wet habitats. To study the sexual differences in reaction norms of growth, we reared spiderlings from seven populations at two food levels under controlled laboratory conditions and compared size at sexual maturity. The shapes of reaction norms for adult size differed between the sexes. In females, the reaction norms were parallel, but individuals from dry habitats tended to grow larger at the given food levels. In males, there was a significant interaction between food level and population without any consistent differences between populations. Maturation time was a plastic character in both sexes with no genetic differences among populations. However, females on low food level matured later and significantly smaller in size than those on high food level. Males also matured later on low food level, but they were nearly of the same size as males that received more food. Female growth patterns reflected the strong selection for large size at maturity. However, the patterns for males were highly variable, which could be explained by the weak overall selection on male size, which means that any environmental factors can affect male growing patterns. This revised version was published online in November 2006 with corrections to the Cover Date.     

Fish assemblage patterns in the littoral zone of a European reservoir

1. Although reservoirs are common aquatic habitats in Europe, there is little quantitative information on the spatial organisation of fish assemblages inhabiting their littoral zones. Consequently, we characterised fish assemblage structure in the littoral zone of a reservoir (Lake Pareloup) in SW France during late spring, summer and early autumn (the growing season).
2. We measured the relative abundance of fish weekly, from mid-May to mid-October, using point abundance sampling by electrofishing. We identified temporal patterns in assemblage structure using hierarchical cluster analysis, and then characterised the spatial distribution of 17 defined ecospecies using a Kohonen self-organising map (SOM, an unsupervised Artificial Neural Network).
3. Our analyses revealed three distinct faunal structures within the littoral zone. From mid-May to mid-July, adults and young-of-the-year (0+) occupied separate habitats, with most 0+ fish in vegetated habitats and adults in open water. From mid-July to late August, some 0+ co-occurred with adults, but most 0+ fishes remained in vegetated areas. Finally, from late August to mid-October, most fish (both 0+ and adults) left the vegetation for unvegetated littoral habitats, the exception being fish species known to be dependent on macrophytes.
4. Contrary to patterns for adult fishes, the 0+ fish assemblage was dynamic. These dynamics were driven by ontogenetic species-specific habitat changes. Consequently, there was little evidence of stable assemblages or strong assemblage–habitat relationships that would be expected of an 'interactive' assemblage. It is likely that the patterns observed are a result of species-specific response to habitat availability in the lake.     

Polymorphism in lake trout in Great Bear Lake: intra‐lake morphological diversification at two spatial scales

Great Bear Lake is the most northerly lake of its size and provides unique opportunities for intraspecific diversification. Despite increasing attention to intraspecific polymorphism, several knowledge gaps remain (e.g. determining the extent of intraspecific diversification in large relatively pristine lakes and at which spatial scale it can occur). We focused on geographical patterns of morphological differentiation within lake trout (Salvelinus namaycush) to describe two levels of intralake diversification in Great Bear Lake. We used a combination of geometric and traditional linear measurements to quantify differences in body shape, head shape, and fin and body lengths among 910 adult lake trout from the five distinct arms of Great Bear Lake. Although head and fin linear measurements discriminated the three common morphotypes at the whole‐lake level, inter‐arm variation in body shape was observed within each morphotype. A comparison of genetic and morphological distance matrices revealed the lack of an association between the two sets of data, although both comparisons revealed an association in the inter‐arm variation patterns among morphotypes, suggesting a phenotypically plastic response to distinct environments. The whole‐lake and inter‐arm morphological variation observed within lake trout demonstrates the importance of considering scale, especially across large lakes that exhibit marked complexity and a variety of freshwater habitats. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114 , 109–125.     

Trophic and spatial interrelationships in the fish species of an Ontario temperate lake

Synopsis Analysis of the fish faunas of Lake Opinicon and other small, cold temperate Ontario water bodies shows that the component species differ in body size, morphology, abundances, habitats, diurnal and seasonal habitat utilization patterns, diets, dietary changes with age, reproductive strategies, and population turnover rates. These differences are detailed.The number of species occurring in a lake is partly due to historic factors, the number of habitats available, and morphological, behavioral and ecological adaptations that, by channelling their owners towards alternative resources, permit species to co-occur. Diet overlap values between most species are low except for the congeneric bluegill and pump-kinseed sunfishes, where values are moderate. These are the two commonest species in the lake and other parameters must increase the ecological differences between these two species.Lake Opinicon is a highly variable ecosystem. Part of this variability stems from the seasonal nature of the environment and the fact that different resources reach their peak abundance at different times of the year. Ecological overlap levels between fish species fluctuate greatly in the course of the season as species switch from, or move on to, different resources. Population levels in different habitats also vary seasonally. Species adaptations and interaction patterns were presumably evolved over a long period; most of these adaptations undoubtedly developed before the component species colonized the lake.This paper forms part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N.Y., 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Helfman, ed.).     

Abundance patterns of filter-feeding Caddisflies (Trichoptera : Hydropsychidae) and seston in a Montana (U.S.A.) lake outlet

The abundance patterns of four species of net-spinning caddisflies (Trichoptera : Hydropsychidae) were studied in a Montana (U.S.A.) lake outlet stream. Total Hydropsychidae reached very high densities (X > 1400 / 0.2 m²) near the lake outfall but declined precipitously downstream. Abundance patterns generally agree with a published model of filter-feeder / seston interactions in lake outlets. Larval densities were greater on moss-covered substrates and one species occupied habitats of lower water velocity compared to other species. Seston concentrations increased downstream contrary to expectation. Nutrient quality of seston may be important in predicting abundance of stream filter-feeders.     

Viral abundance and genome size distribution in the sediment and water column of marine and freshwater ecosystems

The size distribution of viral DNA in natural samples was investigated in a number of marine, brackish and freshwater environments by means of pulsed field gel electrophoresis (PFGE). The method was modified to work with both water and sediment samples, with an estimated detection limit for individual virus genome size groups of 1-2 x 10(4) virus-like particles (VLP) mL(-1) water and 2-4 x 10(5) VLP cm(-3) sediment in the original samples. Variations in the composition and distribution of dominant virus genome sizes were analyzed within and between different habitats that covered a range in viral density from 0.4 x 10(7) VLP mL(-1) (sea water) to 300 x 10(7) VLP cm(-3) (lake sediment). The PFGE community fingerprints showed a number of cross-system similarities in the genome size distribution with a general dominance of genomes in the 30-48, 50-70 and 145-200 kb size fractions, and with many of the specific genome sizes detected in all the investigated habitats. However, large differences in community fingerprints were also observed between the investigated sites, and some virus genome sizes were found only in specific biotopes (e.g. lake water), in specific ecosystems (e.g. a particular lake) or even in specific microhabitats (e.g. a particular sediment stratum).     

Dynamic micro-geographic and temporal genetic diversity in vertebrates: the case of lake-spawning populations of brown trout (Salmo trutta)

Conservation of species should be based on knowledge of effective population sizes and understanding of how breeding tactics and selection of recruitment habitats lead to genetic structuring. In the stream‐spawning and genetically diverse brown trout, spawning and rearing areas may be restricted source habitats. Spatio–temporal genetic variability patterns were studied in brown trout occupying three lakes characterized by restricted stream habitat but high recruitment levels. This suggested non‐typical lake‐spawning, potentially representing additional spatio–temporal genetic variation in continuous habitats. Three years of sampling documented presence of young‐of‐the‐year cohorts in littoral lake areas with groundwater inflow, confirming lake‐spawning trout in all three lakes. Nine microsatellite markers assayed across 901 young‐of‐the‐year individuals indicated overall substantial genetic differentiation in space and time. Nested gene diversity analyses revealed highly significant (≤P = 0.002) differentiation on all hierarchical levels, represented by regional lakes (F_LT = 0.281), stream vs. lake habitat within regional lakes (F_HL = 0.045), sample site within habitats (F_SH = 0.010), and cohorts within sample sites (F_CS = 0.016). Genetic structuring was, however, different among lakes. It was more pronounced in a natural lake, which exhibited temporally stable structuring both between two lake‐spawning populations and between lake‐ and stream spawners. Hence, it is demonstrated that lake‐spawning brown trout form genetically distinct populations and may significantly contribute to genetic diversity. In another lake, differentiation was substantial between stream‐ and lake‐spawning populations but not within habitat. In the third lake, there was less apparent spatial or temporal genetic structuring. Calculation of effective population sizes suggested small spawning populations in general, both within streams and lakes, and indicates that the presence of lake‐spawning populations tended to reduce genetic drift in the total (meta‐) population of the lake.     

云南中部湖群越冬水禽群落特征

云南中部湖群是云贵高原重要的水禽越冬区,掌握该地区越冬水禽群落特征对水禽保护以及湿地资源管理具有重要指导意义。于2017—2018和2018—2019年冬季,采用样点法对云南中部湖群(滇池、抚仙湖、杞麓湖、星云湖)水禽群落特征进行了调查。共记录到水禽7目9科40种,总体来看,云南中部湖群的水禽群落在物种组成上以鸭类为主,占总种数的30%,而在数量上以鸥科的红嘴鸥Larus ridibundus(91.92%)为优势种类。运用非参数物种丰富度估计,发现滇池水禽丰富度较高(37.17±1.13),其次为杞麓湖(33.70±1.74)和星云湖(32.05±1.80),抚仙湖(17.78±0.43)较低;从物种均匀度(Simpson指数)来衡量,抚仙湖水禽均匀度较高(0.63±0.03),其次为星云湖(0.53±0.07)和杞麓湖(0.52±0.05),滇池较低(0.11±0.03)。各湖的物种丰富度与湖体平均水深呈负相关(r=-0.509,P<0.05),而与湖体面积无显著相关性(r=0.286,P>0.05);对物种组成相似性进行聚类分析,发现滇池和其他3个湖泊的水禽组成差异性...     

Reproductive ecology of Caribbean reef corals

The last decade has seen a resurgence of interest in the processes of sexual reproduction by scleractinian reef corals. Earlier investigations had focused fortuitously on brooding (planulating) species, which resulted in the general misconception that brooding was the main form of larval development of reef corals. More recent work on Indo-Pacific species has shown broadcast spawning and short annual reproductive periods to predominate. This report presents the reproductive patterns of eleven Caribbean coral species and attempts to explain the adaptive features and selective pressures that have led to the evolution of the four reproductive patterns described to date: (a) hermaphroditic broadcasters; (b) gonochoric broadcasters; (c) hermaphroditic broadcasters; (b) gonochoric brooders. Both (a) and (b) correlate with large colony size and short annual spawning periods; and (c) and (d) correlate with small colony size, multiple planulating cycles per year, and occupation of unstable habitats. Selection for outcrossing between long-lived individuals is proposed as the reason for gonochorism and for synchronous spawning of hermaphroditic broadcasters, and also for the large amount of sperm produced by hermaphroditic brooders. Selection for high rates of local recruitment is proposed as the force behind the evolution of brooding by species inhabiting unstable habitats and suffering high rates of adult mortality.     

A phylogenetic perspective on habitat shifts and diversity in the North American Enallagma damselflies

Community ecologists are increasingly aware that the regional history of taxon diversification can have an important influence on community structure. Likewise, systematists recognize that ecological context can have an important influence on the processes of speciation and extinction that create patterns of descent. We present a phylogenetic analysis of 33 species of a North American radiation of damselflies (Zygoptera: Coenagrionidae: Enallagma Selys), which have been well studied ecologically, to elucidate the evolutionary mechanisms that have contributed to differences in diversity between larval habitats (lakes with and without fish predators). Analysis of molecular variation in 842 bp of the mitochondrial cytochrome oxidase I and II subunit and of the intervening Leu-tRNA and 37 morphological characters resulted in three well-defined clades that are only partially congruent with previous phylogenetic hypotheses. Molecular and morphological data partitions were significantly incongruent (p < .01). Lack of haplotype monophyly within species and small amounts of sequence divergence (< 1%) between related species in three of the four clades suggest that recent, and parallel, speciation has been an important source of community diversity. Reconstruction of habitat preference over the phylogeny suggests that the greater species diversity in fish-containing lake habitats reflects the recency of shifts into the fishless lake habit, although a difference in speciation or extinction rates between the two habitats is difficult to exclude as an additional mechanism.     

A management plan for the sport fishery of Parachromis dovii (Pisces: Cichlidae) in Hule lake, Costa Rica

A first attempt to regulate the fishing activity while preserving the species and its habitats is presented for Hule lake. We intensively sampled the "guapote" between March 1996 and April 1997 using monofilament gill nets and a floating line, collecting 421 individuals. P. dovii biomass was relatively low; this species had a long life cycle (8-10 years) and the growth oscillation was low (C = 0.3). Maximum life expectation was estimated at 12 years and the point of minimum growth coincided with the spawning that takes place between November and December. After spawning, P. dovii take around seven months to reach recruitment size (54.6 mm). The length for sexual maturity was 134 mm Lt, which indicates that this species is viable for reproduction soon after leaving the protection zones around the lagoon. "Guapote" sport fishing in the Hule lake is in equilibrium, the renewal rate is 80%. An increment in the actual fishery effort is not recommended, since it could seriously affect the natural renewal capacity of the stock.     

Parasite fauna of bream Abramis brama and roach Rutilus rutilus from a man-made waterway and a freshwater habitat in northern Germany

Fifty specimens each of bream Abramis brama and roach Rutilus rutilus were examined for metazoan parasite fauna and trichodinid ciliates; 25 specimens of each species were collected from the Kiel Canal, a man-made waterway, and a nearby freshwater lake, the Dieksee. This is the first detailed parasitological examination of A. brama and R. rutilus at these locations: 30 parasite species were found, comprising 4 protozoans, 4 myxozoans, 5 digeneans, 3 monogeneans, 2 cestodes, 6 nematodes, 2 acanthocephalans, 3 crustaceans and 1 hirudinean. The crustacean Caligus lacustris occurred in both habitats while 2 other crustacean species, 2 acanthocephalans and 1 hirudinean were recorded exclusively for the lake habitat. Larval as well as adult stages of the different parasite species were found, indicating that both fish species act as intermediate and final hosts in both habitats. The Kiel Canal (total of 17 parasite species) showed a lower parasite species richness for A. brama and R. rutilus (14 and 10 parasite species, respectively) than the lake (25 parasite species). A. brama had a higher parasite richness (22 species) than R. rutilus (16 species) in the lake habitat. Most parasites collected were of freshwater origin. Consequently, the observed infection pattern of both fish species in the waterway is mainly influenced by the limited salinity tolerance of freshwater parasites, which are negatively affected even by a salinity of 2.3 to 4.5. In the central Kiel Canal, neither fish species was infected with marine parasites of low host specifity. These parasites are either limited by the low salinity at this sampling site (<4.5 to 6.0) or they cannot enter the canal due to the environmental conditions prevailing in this artificial brackish water habitat. Thus, the canal may comprise a natural barrier preventing the distribution of North Sea parasites into the Baltic Sea. However, the brackish water Baltic Sea nematodes Paracuaria adunca and Cosmocephalus obvelatus were found in R. rutilus from the canal, demonstrating the ability of some parasite species to invade and extend their range of distribution through this man-made shipping route from the Baltic to the North Sea.     

The contribution of common and rare species to plant species richness patterns: the effect of habitat type and size of sampling unit

Understanding how overall patterns of spatial variation in species richness are affected by distributional patterns of species has been an area of growing concern. In the present study, we investigated the relative importance of common and rare species as contributors in overall plant species richness. We further examined if the effects of common or rare species in richness patterns are affected by the size of the sampling units and if the observed patterns hold at different habitats. We used a dataset of 5,148 higher plant species distributed across 16,114 sampling plots located in 240 sites of the NATURA 2000 network of Greece. We ranked all species based on the number of sites they occupied and we developed a common to rare and a rare to common sequence. We correlated those sequences with cumulative species distributions. We performed this analysis in nine different sizes of sampling units and in three different datasets referring to (a) all habitat types together, (b) coniferous habitats only and (c) alpine habitats only. Our analysis showed that despite the proportionally higher numbers of restricted species, widespread species make a greater contribution to overall richness patterns and that this observed pattern does not depend on the size of the sampling units. Moreover, the observed pattern stands for different habitat types. Our findings support the generality of this pattern and highlight the importance of widespread species as adequate indicators of biodiversity patterns at various habitat types. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Patterns of lake occupancy by fish indicate different adaptations to life in a harsh Arctic environment

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