Carl F. Lgler

Bio: Carl F. Lgler is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 912 citations.

Biology and conservation of sturgeon and paddlefish

Abstract: The Acipenseriformes (sturgeon and paddlefish)live in the Northern Hemisphere; half of thesespecies live in Europe, mostly in thePonto-Caspian region, one third in NorthAmerica, and the rest in East Asia and Siberia.They reproduce in freshwater and most of themmigrate to the sea, either living in brackishwater (Caspian, Azov, Black and Baltic Seas) orin full seawater on the oceanic continentalshelf. Most species feed on benthic organisms.Puberty usually occurs late in life (5–30 yearsof age) and adult males and females do notspawn on an annual basis. Adults continue togrow and some species such as the beluga (Huso huso) have reached 100 years of age andmore than 1,000 kg weight. Stocks of sturgeonsare dramatically decreasing, particularly inEurasia; the world sturgeon catch was nearly28,000 t in 1982 and less than 2,000 t by 1999.This decline resulted from overfishing andenvironmental degradation such as: accumulationof pollutants in sediments, damming of rivers,and restricting water flows, which becomeunfavorable to migration and reproduction.Several protective measures have beeninstituted; for example, fishing regulation,habitat restoration, juvenile stocking, and theCITES listing of all sturgeon productsincluding caviar. In addition, sturgeon farmingpresently yields more than 2,000 t per year(equivalent to wild sturgeon landings) andabout 15 t of caviar. Hopefully, thisartificial production will contribute to areduction of fishing pressure and lead to therehabilitation of wild stocks.

Advances in morphometric identification of fishery stocks

Abstract: Geographic variation in morphometry has been used todiscriminate local forms of fish for over a century. The historical development of stock identificationmethods has paralleled the advancement of morphometrictechniques. The earliest analyses of morphometricvariables for stock identification were univariatecomparisons, but were soon followed by bivariateanalyses of relative growth to detect ontogeneticchanges and geographic variation among fishstocks. As the field of multivariatemorphometrics flourished, a suite of multivariatemethods was applied to quantify variation in growthand form among stocks. More recent advances have beenfacilitated by image processing techniques, morecomprehensive and precise data collection, moreefficient quantification of shape, and new analyticaltools. Many benchmark case studies and critiquesoffer guidelines for sampling morphometrics andinterpreting multivariate analyses for exploratorystock identification, stock discrimination, and stockdelineation. As examples of morphometric stockidentification based on life history differences,allometric patterns of crustacean secondary sexcharacters have been used to detect geographicvariation in size at maturity, and morphometriccorrelates to smoltification have been used todiscriminate salmon from different rivers. Morphometric analysis provides a powerful complementto genetic and environmental stock identificationapproaches. The challenge for the future ofmorphometric stock identification is to develop aconsensus on biological interpretations of geometricanalyses, similar to the conventional interpretationsof size and shape from traditional multivariatemorphometrics.

Biological Field And Laboratory Methods For Measuring The Quality Of Surface Waters And Effluents

Abstract: The role of aquatic biology in the water pollution control program of the U. S. Environmental Protection Agency includes field and laboratory studies carried out to establish water quality criteria for the recognized beneficial uses of water resources and to monitor water quality. Field studies are employed to: measure the toxicity of specific pollutants or effluents to individual species or communities of aquatic organisms under natural conditions; detect violations of water quality standards ; evaluate the trophic status of waters ; and determine long-term trends in water quality. Laboratory studies are employed to : measure the effects of known or potentially deleterious substances on aquatic organisms to estimate “safe” concentrations ; and determine environmental requirements (such as temperature, pH, dissolved oxygen, etc.) of the more important and sensitive species of aquatic organisms. Field surveys and water quality monitoring are conducted principally by the regional surveillance and analysis and national enforcement programs. Laboratory studies of water quality requirements, toxicity testing, and methods development are conducted principally by the national research programs.

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

Abstract: 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.