Scale morphology is a promising, additional tool for exploring the taxonomy and ecology of freshwater fishes

In Atlantic salmon, as in most salmonids, males can mature early in the life cycle, as small freshwater fish, termed parr, and/or undergo a sea migration before maturing as full–size adults. The alternative life histories are contingent on environmental and social circumstances, such as growth rate, territory quality or any other factor that affects the individual9s state. In order to model the choice of life history in this group of commercially valuable species, it is necessary to understand not only the relative contribution of the different male types to subsequent generations, but also to know the factors that affect reproductive success in each type. In this paper we present the results of a study designed to investigate the factors that affect the reproductive success of mature parr. We used highly polymorphic minisatellite DNA markers to analyse paternity in a series of mating experiments where the number and body size of parr were manipulated. The fraction of eggs fertilized by mature parr ranged from 26 to 40 per cent, with individual parr fertilizing up to 26 per cent of the eggs. A strong positive correlation was found between parr size and reproductive success. The relative success of parr decreased with increasing parr number. Data from this and other studies on variation in the timing and degree of parr reproductive success are discussed in relation to the evolution of male mating strategies and life history in salmonids.

We tested the hypothesis that dispersal is sex biased in an unexploited population of brook trout, Salvelinus fontinalis, on Cape Race, Newfoundland, Canada. Based on the assumptions that trout are promiscuous and that reproductive success is limited primarily by either number of mates (males) or fecundity (females), we predicted that males would disperse greater distances than females. We also tested the hypothesis that trout populations comprise stationary and mobile individuals, predicting that males have greater mobility than females. Based on a mark-recapture study of 943 individually tagged fishes, 191 of which were recaptured over 5 years, we find strong support for our hypothesis of male-biased dispersal in brook trout. Averaged among all 11 resampling periods, males dispersed 2.5 times as far as females; during the spawning period only, male dispersal exceeded that by females almost fourfold. Both sexes were heterogeneous with respect to movement, with a lower incidence of mobility among females (29.6%) than males (41.1%); mobile males dispersed six times further than mobile females. We conclude that this sex bias reduces mate competition among male kin and decreases the probability that males will reproduce with related females.

Site d'etude: zone situee sous le barrage de Markles; problemes d'echantillonnage; nombre d'especes incluses dans l'analyse. Inclusion des jeunes d'un an dans cette analyse; interpretation et nouvelle analyse des modeles alternatifs

Assemblage Organization of Stream Fishes: The Effect of Rivers on Adventitious Streams

Despite supporting a disproportionately large fraction of the global biodiversity, freshwater ecosystems are ranked as the most highly threatened habitats ahead of both terrestrial and marine ecosystems. Furthermore, many regions are still characterized by limited knowledge on taxonomy and ecology of freshwater fishes. The need for ecological information in understudied regions is important particularly where there are recent discoveries of new species and unique lineages and for threatened and endangered taxa that require conservation management. This study evaluated the trophic ecology of two freshwater fish species Sandelia bainsii and Amatolacypris trevelyani that are both classified as endangered in the International Union for Conservation of Nature (IUCN) Red List. These two species, which are narrow‐range endemics in the Eastern Cape, South Africa, comprise allopatric lineages whose ecology is poorly known. This study used stable isotope analysis to evaluate the food web patterns, explore the trophic niche dynamics and estimate the prey source contributions for the two species in different headwater habitats. The fishes isotopic niche sizes were spatially variable, suggesting the likely importance of stochastic variation in resource availability and probable interspecific interactions. The three lineages within S. bainsii exhibited low isotopic niche overlap onto those of sympatric fishes in most habitats. Isotopic mixing model revealed that these lineages' diets were mostly dominated by gatherers/collectors. In comparison, the two lineages within A. trevelyani exhibited high niche overlap with other species and generally had variable diets. Despite the low and high niche overlap patterns of S. bainsii and A. trevelyani, respectively, the isotopic niche overlap patterns of co‐occurring species onto those of the former suggest the likely lack of competitive hierarchies. The trophic niche patterns of these two endangered species helped to shed some light on the potential invasion risks by non‐piscivorous fishes with opportunistic feeding habits, which could exert competitive interspecific interactions.

The morphology of fish scales has been investigated for > 200 years, but research on evolutionary patterns of scale morphology is scarce. Here, we study scale morphology and its evolution in the adaptive radiation of cichlid fishes from Lake Tanganyika, which are known for their exceptional diversity in habitat use, feeding ecology and morphology. Based on a geometric morphometric approach on eight scales per specimen (covering different body regions), we quantify scale types and morphology across nearly all ~240 species of the cichlid adaptive radiation in Lake Tanganyika. We first show that scale type, shape and ctenii coverage vary along the body, which is probably attributable to adaptations to different functional demands on the respective scales. Our comparative analyses reveal that flank scale size is tightly linked to phylogeny, whereas scale shape and ctenii coverage can be explained only in part by phylogenetic history and/or our proxy for ecology (stable isotopes and body shape), suggesting an additional adaptive component. We also show that our measured scale characteristics can help to assign an individual scale to a taxonomic group or ecotype. Thus, our data may serve as a valuable resource for taxonomic studies and to interpret fossil finds.

Unsaturated Fish Communities in African Rivers

The impact of human activity is evident in the depletion of fish populations worldwide. This being the case, there is an urgent need to discover the true biodiversity of the world before the loss rate exceeds its limits. Because the feeding ecology of a species is thoroughly linked to its population dynamics, knowledge of the feeding ecology contributes to the understanding of such subjects as resource partitioning, habitat preferences, prey selection, predation, evolution, competition and energy transfer within and between ecosystems. Such ecological information is of great value when developing conservation strategies and is, therefore, a key element in the protection of species and ecosystems. Our paper reviews the geographic and/or biogeographic regions where the majority of studies concerning the feeding ecology of fish have been conducted, with the goal of identifying regions and/or environments in need of further attention. In addition, we identify which journals published more papers regarding the subject. Our analysis was conducted by assessing studies indexed on the ISI Web of Science database. We detected a lack of data concerning several aspects of the feeding of fish, such as: threatened species; freshwater habitats especially within the Neotropical, Ethiopian and Oriental realms; species rich developing countries; and, when considering marine fish, the Eastern Indo-Pacific region. Considering the calculated weight for each journal, Ecology of Freshwater Fish, Neotropical Ichthyology and Environmental Biology of Fishes were the most important ones. If we ignore these gaps in our knowledge we run the risk of losing a huge amount of information without knowing it ever existed, especially in the fast changing world we face today.

Spatial patterns of correlated scale size and scale color in relation to color pattern elements in butterfly wings

Abstract– Projected world population increases imply demand for an increase of 60 million tonnes on the present world fish production of 100 million tonnes. Capture fisheries are unlikely to yield more because many stocks are already overexploited, there are few remaining unexploited and management shows few signs of redressing problems. Aquaculture is a possible source of the required production, given maintenance of current rates of increase. If this potential is to be realized, the importance of maintaining the quality of freshwater, brackish and coastal marine environments can scarcely be overstated. In a world of rapid change, there is an urgent need for research at all levels of biological and social organization that relate to the ecology of freshwater fish. At the organismic level, genetics, migratory behaviour and physiological ecology will be emphasized. Population genetics research is needed to enlighten controversies concerning the impact of cultural practices and the effects of harvesting natural populations. Greater attention will be given to interactions between species, including fish and their parasites, and the dynamics of multispecies interactions in pond culture and in capture fisheries. Issues of multiple uses of water resources will force research on freshwater fish ecology into broader contexts. The march of discovery in all branches of science will have major implications for freshwater fisheries research. The next few decades will be demanding of the creative energies of young researchers.

The mass of women and men who study ecology of fishes do indeed “lead lives of quiet desperation”—but not the world-weary despair of Thoreau. Most, like Reighard, exist in a state of chronic tension between deep satisfaction with their work and frustration from the fact that fishes are so complex that no individual can understand all that could be known about their ecology, even if there were no “university (or agency or museum) duties.” There are so many kinds of fishes, occupying such diverse habitats, evolving in such complex ways, and with such complicated ecological traits, that a total synthesis of “understanding fishes” will always elude ichthyologists and ecologists. This book is an attempt to synthesize what is known about ecology of freshwater fishes, to make sense of their distribution and abundance across the Earth, their membership in local assemblages, and the ways they, in turn, influence the ecosystems where they live. These are some of the “patterns in freshwater fish ecology” addressed in this book.

BackgroundHabitat selectivity and ecology of freshwater fishes were studied in two selected streams and their junction point which consist a total of 39 microhabitats. The aims of this study were to describe the habitat preference and its availability to fish assemblage, as well as ecology, habitat use, and habitat characteristics.MethodsWe collected fish with backpack electrofishing three times during August 2013, December 2013, and March 2014. Using a variation partitioning approach of R software, we studied the relationship of fish abundances with stream type, habitat type, and abundance of key macroinvertebrate taxa.ResultsA total of 6554 fishes representing four species belonging to the family Cyprinidae were caught. A higher total fish abundance was recorded from Gereb Tsedo (4870; 74.3%) than from Elala stream (1684; 25.7%). Taking both streams together, the overall total relative fish abundance was significantly higher in pools (53%) than in runs (35%) and in riffles (12%) at P < 0.05. Species-wise comparisons showed that 71%, 15%, 13%, and 1% of the pool fish community were occupied by Garra blanfordii, Garra ignestii, Garra dembecha, and Garra aethiopica, respectively. Stream type, habitat type, and key macroinvertebrate taxa each explained a significant proportion of the variation in fish abundance. Based on the variation partitioning approach, fish abundance was higher in Gereb Tsedo stream (P < 0.01). Moreover, fish abundance increased with pool habitat type (P < 0.01) and with availability of key macroinvertebrate taxa (P < 0.01).ConclusionFish abundance differed between stream types, among habitats and among key macroinvertebrate taxa availability. Among the factors, habitat type was the most important driving factor behind variation among fish abundances, and pool supports the highest fish abundance.

The pike (Esox lucius Linnaeus 1758), or northern pike in North America, is a well-known fish species to anglers, managers, and scientists. As the only northern hemisphere circumpolar species represented in the family Esocidae, pike are studied in many different countries and cultures. The pike’s broad distribution in rivers and lakes throughout Eurasia and North America, trophic position as a top carnivore, effects on prey communities, and value in recreational and commercial fisheries, highlight its importance over countless, and varied aquatic systems. Complexity surrounds this species, with concern over the status of natural pike populations in some areas of its range, as well as its effects on ecosystems and fish communities, where it is endemic or has been introduced. Altered recruitment processes associated with changes and losses in critical habitats and flow regime characteristics, water quality declines, and climate change threatens this species worldwide. A general interest exists in the role of pike in fish communities and aquatic systems as well as in the effective management of recreational and commercial fisheries. Much can be learned from a symposium with a comprehensive focus by experts regarding pike life history, behavior, habitat use and requirements, population dynamics, physiology, role in ecology, and management issues. This symposium was envisioned by a group of scientists at the 2004 conference ‘‘Behavior and ecology of freshwater fish: linking ecology and individual behavior’’ hosted by the Danish Institute for Freshwater Research in Silkeborg, Denmark. Such an opportunity was given at the 136th annual meeting of the American Fisheries Society in Lake Placid 2006. A two-day symposium entitled ‘‘International Pike Symposium: merging knowledge of ecology, biology, and management for a circumpolar species’’ comprised 28 presentations by researchers from seven countries covering a variety of pike topics, and two panel discussions on the management and the ecology of pike. The objective of this symposium was to create and facilitate information exchanges regarding northern Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species

Putting Things in Order: The Ups and Downs of Detrended Correspondence Analysis

Previous articleNext article No AccessPopulation Dynamics of Brown Trout in Different EnvironmentsJames T. McFadden and Edwin L. CooperJames T. McFadden Search for more articles by this author and Edwin L. Cooper Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 37, Number 4Oct., 1964 Article DOIhttps://doi.org/10.1086/physzool.37.4.30152754 Views: 6Total views on this site Citations: 12Citations are reported from Crossref Journal History This article was published in Physiological Zoology (1928-1998), which is continued by Physiological and Biochemical Zoology (1999-present). PDF download Crossref reports the following articles citing this article:Leon M. Carl Lake trout demographics in relation to burbot and coregonine populations in the Algonquin Highlands, Ontario, Environmental Biology of Fishes 83, no.22 (Dec 2007): 127–138.https://doi.org/10.1007/s10641-007-9305-7Gunnar Öhlund, Fredrik Nordwall, Erik Degerman, Torleif Eriksson Life history and large-scale habitat use of brown trout ( Salmotrutta ) and brook trout ( Salvelinus fontinalis ) — implications for species replacement patterns, Canadian Journal of Fisheries and Aquatic Sciences 65, no.44 (Apr 2008): 633–644.https://doi.org/10.1139/f08-003J. LOBON-CERVIA Density-dependent growth in stream-living Brown Trout Salmo trutta L., Functional Ecology 21, no.11 (Feb 2007).https://doi.org/10.1111/j.1365-2435.2006.01204.xF. Nordwall, P. Lundberg, T. Eriksson Comparing size-limit strategies for exploitation of a self-thinned stream fish population, Fisheries Management and Ecology 7, no.55 (Jul 2008): 413–424.https://doi.org/10.1046/j.1365-2400.2000.00227.xW. Van Winkle, H.I. Jager, S.F. Railsback, B.D. Holcomb, T.K. Studley, J.E. Baldrige Individual-based model of sympatric populations of brown and rainbow trout for instream flow assessment: model description and calibration, Ecological Modelling 110, no.22 (Jul 1998): 175–207.https://doi.org/10.1016/S0304-3800(98)00065-9R. M. Newman A conceptual model for examining density dependence in the growth of stream trout, Ecology of Freshwater Fish 2, no.33 (Sep 1993): 121–131.https://doi.org/10.1111/j.1600-0633.1993.tb00092.xM. Zalewski, P. Frankiewicz, B. Brewinska The factors limiting growth and survival of brown trout, Salmo trutta m.fario L. introduced to different types of streams, Journal of Fish Biology 27, no.sasa (Dec 1985): 59–73.https://doi.org/10.1111/j.1095-8649.1985.tb03232.xK. SADLER A model relating the results of low pH bioassay experiments to the fishery status of Norwegian lakes, Freshwater Biology 13, no.55 (Oct 1983): 453–463.https://doi.org/10.1111/j.1365-2427.1983.tb00004.xErik Mortensen The population dynamics of young trout (Salmo trutta L.) in a Danish brook, Journal of Fish Biology 10, no.11 (Jan 1977): 23–33.https://doi.org/10.1111/j.1095-8649.1977.tb04038.xE. Werner, D. Hal Niche shifts in sunfishes: experimental evidence and significance, Science 191, no.42254225 (Jan 1976): 404–406.https://doi.org/10.1126/science.1246626G. R. Fish, R. L. Allen, H. S. Fairburn An examination of the trout population of five lakes near Rotorua, New Zealand, New Zealand Journal of Marine and Freshwater Research 2, no.22 (Jun 1968): 333–362.https://doi.org/10.1080/00288330.1968.9515240James T. McFadden, Gaylord R. Alexander, David S. Shetter Numerical Changes and Population Regulation in Brook Trout Salvelinus fontinalis, Journal of the Fisheries Research Board of Canada 24, no.77 (Jul 1967): 1425–1459.https://doi.org/10.1139/f67-121