DOCSLIB.ORG

S1 17 Vandenberghcheers Nov2019

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
S1 17 Vandenberghcheers Nov2019 Hyperbenthos in the upper reaches of the Scheldt estuary (Belgium): an indispensable trophic link re-established Erika van den Bergh Liesbeth De Neve, Gunther Van Ryckegem, Joost Vanoverbeke, Frank Van de Meutter, Alexander Van Braeckel, Jeroen Speybroeck Hyperbenthos? • A group of typically small organisms that live in the lower layers of the water column, just above the bottom o Peracarida - Mysida (opossum shrimps) - Amphipoda - Isopoda o Decapod shrimps (epibenthos) o Juvenile fish • Good estuarine ecosystem quality indicators • Key role in the estuarine food web Scheldt estuary • 1950-1980 permanent hypoxia, recurrent anoxia Vlissingen no life North Sea • 1980-2007 POLYHALINE steady improvement MESOHALINE of water quality macrobenthos The Netherlands boom & waterbirds Antwerpen OLIGOHALINE since 2007 zooplankton, Durme hyperbenthos and fish FRESHWATER communities have Belgium recolonized Gent Melle Aims freshwater tidal zones are poorly studied and understood in Europe , the upper reaches of the Scheldt estuary offer a quite unique study system Understanding biotic responses to water and habitat quality restoration is essential for appropriate management Intensive monitoring campaign in the mesohaline to freshwater tidal zones of the Scheldt estuary - Document recovery of hyperbenthos community after decades of absence - How do hyperbenthos communities vary in space and time? - Which environmental variables drive spatio-temporal patterns? Sample protocol • 6 sample sites • each month Vlissingen • 2013 - 2018 North Sea POLYHALINE MESOHALINE M1 • M1: Paardenschor M2 • M2: St-Anna Antwerpen • O1: Ballooi OLIGOHALINE • O2: Rupel Durme • F1: Dendermonde 100 O1 • F2: Brede schoren FRESHWATER Gent Melle Variables Evironmental • Temperature (°C) • Conductivity (µS/cm) Biotic • DO (mg/l) • SPM (mg/l) • Species composition • POM (mg/l) • Abundance(N/100m³) • River discharge • Biomass (AFDW; mg/100m³) • 5days before (m³/s) • Preceding season (m³/day) • Tidal amplitude (m) • Ebb duration (h) • Sampling moment in spring/neap cycle Species richness 62 different taxa (32 occurred in >3% of samples) Redundancy Analysis (RDA) Seasonal variation Spatial variation Focal species >20% of the samples >0.1 on at least one RDA axis Total abundance Mesopodopsis slabberi Crangon crangon (brown shrimp) Total abundance Palaemon longirostris Total abundance Osmerus eperlanus (European smelt) Platchithys flesus (European flounder) Total abundance Neomysis integer Pomatoschistus microps (common goby) Total biomass Effect of river discharge seasonal pattern most apparent in latter, dry, years negative relation to short-term river discharge flushing lower short-term residence time positive relation to long-term river discharge prevention of eutrophication Take home message 1. Hyperbenthic communities successfully recovered in the upper reaches of the Scheldt estuary after decades of absence 2. A trophic link in the food web was re-established , adding to the estuarine ecosystem resilience 3. Oligohaline and freshwater tidal areas can represent a valuable extension of the nursing and feeding grounds for marine and estuarine fish and shrimps , 4. Short intense peaks of high river discharge as well as long lasting periods of low discharge negatively impact hyperbenthos abundance in the oligohaline and fresh tidal zones Thank you for your attention Thanks to Jan Soors Team Estuaria Joram De Beukelaer Dimitri Buerms Nico De Regge Thomas Terrie Olja Bezdenjesnji.
Load more

Recommended publications
  • A Practical Handbook for Determining the Ages of Gulf of Mexico And
    A Practical Handbook for Determining the Ages of Gulf of Mexico and Atlantic Coast Fishes THIRD EDITION GSMFC No. 300 NOVEMBER 2020 i Gulf States Marine Fisheries Commission Commissioners and Proxies ALABAMA Senator R.L. “Bret” Allain, II Chris Blankenship, Commissioner State Senator District 21 Alabama Department of Conservation Franklin, Louisiana and Natural Resources John Roussel Montgomery, Alabama Zachary, Louisiana Representative Chris Pringle Mobile, Alabama MISSISSIPPI Chris Nelson Joe Spraggins, Executive Director Bon Secour Fisheries, Inc. Mississippi Department of Marine Bon Secour, Alabama Resources Biloxi, Mississippi FLORIDA Read Hendon Eric Sutton, Executive Director USM/Gulf Coast Research Laboratory Florida Fish and Wildlife Ocean Springs, Mississippi Conservation Commission Tallahassee, Florida TEXAS Representative Jay Trumbull Carter Smith, Executive Director Tallahassee, Florida Texas Parks and Wildlife Department Austin, Texas LOUISIANA Doug Boyd Jack Montoucet, Secretary Boerne, Texas Louisiana Department of Wildlife and Fisheries Baton Rouge, Louisiana GSMFC Staff ASMFC Staff Mr. David M. Donaldson Mr. Bob Beal Executive Director Executive Director Mr. Steven J. VanderKooy Mr. Jeffrey Kipp IJF Program Coordinator Stock Assessment Scientist Ms. Debora McIntyre Dr. Kristen Anstead IJF Staff Assistant Fisheries Scientist ii A Practical Handbook for Determining the Ages of Gulf of Mexico and Atlantic Coast Fishes Third Edition Edited by Steve VanderKooy Jessica Carroll Scott Elzey Jessica Gilmore Jeffrey Kipp Gulf States Marine Fisheries Commission 2404 Government St Ocean Springs, MS 39564 and Atlantic States Marine Fisheries Commission 1050 N. Highland Street Suite 200 A-N Arlington, VA 22201 Publication Number 300 November 2020 A publication of the Gulf States Marine Fisheries Commission pursuant to National Oceanic and Atmospheric Administration Award Number NA15NMF4070076 and NA15NMF4720399.
    [Show full text]
  • Ecological Effects of the Mass Occurrence of the Ponto-Caspian Invader, Hemimysis Anomala G.O
    Hydrobiologia 394: 233-248, 1999 © 1999 Kluwer Academic Publishers. Printed in the Netherlands Ecological effects of the mass occurrence of the Ponto-Caspian invader, Hemimysis anomala G.O. Sars, 1907 (Crustacea: Mysidacea), in a freshwater storage reservoir in the Netherlands, with notes on its autecology and new records Ketelaars H.A.M.1,*, F.E. Lambregts-van de Clundert1, C.J. Carpentier1, A.J. Wagenvoort1 & W. Hoogenboezem2 1Biological Laboratory, Water Storage Company Brabantse Biesbosch, P.O. Box 61, NL-4250 DB Werkendam, The Netherlands 2PWN Water Supply Company North Holland, P.O. Box 5, NL-2060 BA Bloemendaal, The Netherlands E-mail: [email protected] (*author for correspondence) Received 12 December 1998; in revised form 2 February 1999; accepted 25 February 1999 Key words: Hemimysis anomala, Mysidacea, exotic species, Ponto-Caspian, biological invasion, ecological effects Abstract A new Ponto-Caspian invader, the mysid Hemimysis anomala G.O. Sars, 1907 (Crustacea: Mysidacea) was recorded for the first time in the Netherlands in 1997. In the summer of 1998 extremely high den- sities (>6 ind. 1-1) of this neozoon were recorded in one of the Biesbosch reservoirs (Honderd en Dertig). This high abundance can not be explained by a recent invasion. Either H. anomala reached the Nether- lands via the River Rhine, probably aided by shipping, or through transport with ballast water from the Baltic or Black Sea. The invasion had dramatic effects on the zooplankton composition and abundance: from the end of August onwards hardly any Anomopoda, Ostracoda, Rotifera and invertebrate predators (Leptodora kindti and Bythotrephes longimanus) were present.
    [Show full text]
  • C:\Documents and Settings\Leel\Desktop\WA 2-15 DRP
    DRAFT DETAILED REVIEW PAPER ON MYSID LIFE CYCLE TOXICITY TEST EPA CONTRACT NUMBER 68-W-01-023 WORK ASSIGNMENT 2-15 July 2, 2002 Prepared for L. Greg Schweer WORK ASSIGNMENT MANAGER U.S. ENVIRONMENTAL PROTECTION AGENCY ENDOCRINE DISRUPTOR SCREENING PROGRAM WASHINGTON, D.C. BATTELLE 505 King Avenue Columbus, Ohio 43201 TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY ....................................................... 1 2.0 INTRODUCTION .............................................................. 2 2.1 DEVELOPING AND IMPLEMENTING THE ENDOCRINE DISRUPTOR SCREENING PROGRAM (EDSP).......................................... 2 2.2 THE VALIDATION PROCESS............................................. 2 2.3 PURPOSE OF THE REVIEW ............................................. 3 2.4 METHODS USED IN THIS ANALYSIS...................................... 4 2.5 ACRONYMS AND ABBREVIATIONS ....................................... 5 3.0 OVERVIEW AND SCIENTIFIC BASIS OF MYSID LIFE CYCLE TOXICITY TEST ........... 6 3.1 ECDYSTEROID SENSITIVITY TO MEASURED ENDPOINTS ................... 9 4.0 CANDIDATE MYSID TEST SPECIES ............................................ 11 4.1 AMERICAMYSIS BAHIA ................................................ 12 4.1.1 Natural History ................................................... 12 4.1.2 Availability, Culture, and Handling .................................. 12 4.1.3 Strengths and Weaknesses ....................................... 13 4.2 HOLMESIMYSIS COSTATA ............................................. 13 4.2.1 Natural History ................................................
    [Show full text]
  • Changing Communities of Baltic Coastal Fish Executive Summary: Assessment of Coastal fi Sh in the Baltic Sea
    Baltic Sea Environment Proceedings No. 103 B Changing Communities of Baltic Coastal Fish Executive summary: Assessment of coastal fi sh in the Baltic Sea Helsinki Commission Baltic Marine Environment Protection Commission Baltic Sea Environment Proceedings No. 103 B Changing Communities of Baltic Coastal Fish Executive summary: Assessment of coastal fi sh in the Baltic Sea Helsinki Commission Baltic Marine Environment Protection Commission Editor: Janet Pawlak Authors: Kaj Ådjers (Co-ordination Organ for Baltic Reference Areas) Jan Andersson (Swedish Board of Fisheries) Magnus Appelberg (Swedish Board of Fisheries) Redik Eschbaum (Estonian Marine Institute) Ronald Fricke (State Museum of Natural History, Stuttgart, Germany) Antti Lappalainen (Finnish Game and Fisheries Research Institute), Atis Minde (Latvian Fish Resources Agency) Henn Ojaveer (Estonian Marine Institute) Wojciech Pelczarski (Sea Fisheries Institute, Poland) Rimantas Repečka (Institute of Ecology, Lithuania). Photographers: Visa Hietalahti p. cover, 7 top, 8 bottom Johnny Jensen p. 3 top, 3 bottom, 4 middle, 4 bottom, 5 top, 8 top, 9 top, 9 bottom Lauri Urho p. 4 top, 5 bottom Juhani Vaittinen p. 7 bottom Markku Varjo / LKA p. 10 top For bibliographic purposes this document should be cited as: HELCOM, 2006 Changing Communities of Baltic Coastal Fish Executive summary: Assessment of coastal fi sh in the Baltic Sea Balt. Sea Environ. Proc. No. 103 B Information included in this publication or extracts thereof is free for citing on the condition that the complete reference of the publication is given as stated above Copyright 2006 by the Baltic Marine Environment Protection Commission - Helsinki Commission - Design and layout: Bitdesign, Vantaa, Finland Printed by: Erweko Painotuote Oy, Finland ISSN 0357-2994 Coastal fi sh – a combination of freshwater and marine species Coastal fish communities are important components of Baltic Sea ecosystems.
    [Show full text]
  • Maturation at a Young Age and Small Size of European Smelt (Osmerus
    Arula et al. Helgol Mar Res (2017) 71:7 DOI 10.1186/s10152-017-0487-x Helgoland Marine Research ORIGINAL ARTICLE Open Access Maturation at a young age and small size of European smelt (Osmerus eperlanus): A consequence of population overexploitation or climate change? Timo Arula*, Heli Shpilev, Tiit Raid, Markus Vetemaa and Anu Albert Abstract Age of fsh at maturation depends on the species and environmental factors but, in general, investment in growth is prioritized until the frst sexual maturity, after which a considerable and increasing proportion of resources are used for reproduction. The present study summarizes for the frst the key elements of the maturation of European smelt (Osmerus eperlanus) young of the year (YoY) in the North-eastern Gulf of Riga (the Baltic Sea). Prior to the changes in climatic conditions and collapse of smelt fshery in the 1990s in the Gulf of Riga, smelt attained sexual maturity at the age of 3–4 years. We found a substantial share (22%) of YoY smelt with maturing gonads after the collapse of the smelt fsheries. Maturing individuals had a signifcantly higher weight, length and condition factor than immature YOY, indicating the importance of individual growth rates in the maturation process. The proportion of maturing YoY individuals increased with fsh size. We discuss the factors behind prioritizing reproduction overgrowth in early life and its implications for the smelt population dynamics. Keywords: Osmerus eperlanus, Early maturation, Young of the year (0 ), Commercial fsheries + Background and younger ages [5–8]. Such shifts time of maturation Age of fsh at maturation depends on the species and might have drastic consequences for fsh population environmental factors but, in general, investment in dynamics, as the share of early maturing individuals will growth is prioritized until the frst sexual maturity, increase in population [9].
    [Show full text]
  • In Pomerania Bay, Gdansk Bay and Curonian Lagoon
    Journal of Elementology ISSN 1644-2296 Pilarczyk B., Pilecka-Rapacz M., Tomza-Marciniak A., Domagała J., Bąkowska M., Pilarczyk R. 2015. Selenium content in European smelt (Osmerus eperlanus eperlanus L.) in Pomerania Bay, Gdansk Bay and Curonian Lagoon. J. Elem., 20(4): 957-964. DOI: 10.5601/jelem.2015.20.1.876 SELENIUM CONTENT IN EUROPEAN SMELT (OSMERUS EPERLANUS EPERLANUS L.) IN POMERANIA BAY, GDANSK BAY AND CURONIAN LAGOON Bogumiła Pilarczyk1, Małgorzata Pilecka-Rapacz2, Agnieszka Tomza-Marciniak1, Józef Domagała2, Małgorzata Bąkowska1, Renata Pilarczyk3 1Chair of Animal Reproduction Biotechnology and Environmental Hygiene West Pomeranian University of Technology in Szczecin 2 Chair of General Zoology University of Szczecin 3Laboratory of Biostatistics West Pomeranian University of Technology in Szczecin Abstract Migratory smelt (Osmerus eperlanus eperlanus L.) may be perceived as a valuable indicative organism in monitoring the current environmental status and in assessment of a potential risk caused by selenium pollution. The aim of the study was to compare the selenium content in the European smelt from the Bay of Pomerania, Gdansk, and the Curonian Lagoon. The experimen- tal material consisted of smelt samples (muscle) caught in the bays of Gdansk and Pomerania and the Curonian Lagoon (estuaries of the three largest rivers in the Baltic Sea basin: the Oder, the Vistula and the Neman). A total of 133 smelt were examined (Pomerania Bay n = 67; Gdansk Bay n = 35; Curonian Lagoon n = 31). Selenium concentrations were determined spec- trofluorometrically. The data were analyzed statistically using one-way analysis of variance, calculated in Statistica PL software. The region of fish collection significantly affected the content of selenium in the examined smelts.
    [Show full text]
  • Neomysis Mercedis Class: Malacostraca Order: Mysidacea a Mysid, Or Opossum Shrimp Family: Mysidae
    Phylum: Arthropoda, Crustacea Neomysis mercedis Class: Malacostraca Order: Mysidacea A mysid, or opossum shrimp Family: Mysidae Taxonomy: Neomysis awatschensis, N. Carapace: Not attached dorsally at intermedia, and N. mercedis were considered posterior edge. Anterior lateral angles acute three different species (with distinct (Figs. 1, 3). morphology) from the western Pacific, Rostrum: A short triangle with northwestern Pacific and northeast Pacific obtusely pointed apex, and rounded, “flanged” coasts (Tattersall 1951; Holmquist 1973; corners (Tattersall and Tattersall 1951). A Brand et al. 1993), but have since been medial depression obscures the pointed apex synonymized as N. mercedis (Moldin 2007). (Holmquist 1973). In total size, rostrum is only as long as bases of eyestalks (Tattersall Description and Tattersall 1951) (Figs. 1, 3). Size: Adults range in size from 11 to 17 mm Eyes: On movable stalks and about in length (Banner 1948b). The illustrated 1.5 times as long as broad and with corneas specimens (from the Columbia River estuary) that are expanded, but not separated into two were up to 17 mm long. portions (Fig. 3). Color: Clear body with black Antennae: Long, slender, and multi- chromatophores, although an individual articulate (Fig. 1). caught on eelgrass was yellow green Antennae Scale: (= squama) Long, (Banner 1948b). narrow, about eight times longer than wide General Morphology: Mysids are shrimp- (Banner 1948b; Brandt et al. 1993). The size like crustaceans that are occasionally called of the scale, however, may vary among opossum shrimp due to the female individuals (Holmquist 1973). The scale is marsupium or brood pouch, which is setose all around and is with pointed apex composed of oostegites.
    [Show full text]
  • Anguillicola Crassus(Nematoda, Dracunculoidea)
    Anguillicola crassus (Nematoda, Dracunculoidea) infections of European eel (Anguilla anguilla) in the Netherlands: epidemiology, pathogenesis and pathobiology 23 FEB. 1995 UB-CARDEX Olga Haenen LANDBOUWCATALOGUS 0000 0611 3746 ;cn Promotor : Dr. W.B. van Muiswinkel, Hoogleraar in de Zoölogische Celbiologie Landbouwuniversiteit, Wageningen Co-promotor : Dr. F.H.M. Borgsteede, hoofd sectie Parasitologie DLO-Instituut voor Veehouderij en Diergezondheid, Lelystad VO\ l°10S poll d Anguillicola crassus (Nematoda, Dracunculoidea) infections of European eel (Anguilla anguilla) in the Netherlands: epidemiology,pathogenesi s andpathobiolog y Olga Liduina Maria Haenen Proefschrift ter verkrijging van de graad van doctor in de Landbouw- en Milieuwetenschappen, op gezag van de rector magnificus. Dr. CM. Karssen in het openbaar te verdedigen op vrijdag 10 maart 1995 des namiddags te vier uur in de aula van de Landbouwuniversiteit Wageningen isn^Oèf}'! Omslag: Olga Haenen Fotografie: Fred van Welie Joop ledema Vormgeving: Herma Daus-Ooms CIP-GEGEVENS KONINKLIJKE BIBLIOTHEEK, DEN HAAG Haenen, Olga Liduina Maria Anguillicola crassus(Nematoda , Dracunculoidea) infections of European eel{Anguilla anguilla) inth eNetherland s : epidemiology, pathogenesis and pathobiology / Olga Liduina Maria Haenen ; [ill.va n deauteur] .- [S.l. : s.n.J- III. Thesis Landbouw Universiteit Wageningen. - With réf. With summary inDutch . ISBN 90-5485-354-9 Subject headings: Anguillicola crassus/ parasitic nematode / eel. LANDEO l' V vU V; VESSITEIT WAü;";Nh\'C£N The study described in this thesis was performed at the DLO-lnstitute for Animal Science and Health, Lelystad, The Netherlands. aan mijn ouders Stellingen 1. De snelle vestiging en verspreiding van Anguillicola crassus in Nederland is mede te danken aan het brede scala van tussengastheren en paratenische gastheren (dit proefschrift).
    [Show full text]
  • This Is the Published Version of a Paper
    http://www.diva-portal.org This is the published version of a paper published in Slovak Ethnology. Citation for the original published paper (version of record): Svanberg, I., Bonow, M., Cios, S. (2016) Fishing For Smelt, Osmerus Eperlanus (Linnaeus, 1758): A traditional food fish – possible cuisinein post-modern Sweden?. Slovak Ethnology, 2(64) Access to the published version may require subscription. N.B. When citing this work, cite the original published paper. CC BY-NC-ND Permanent link to this version: http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-30594 2 64 • 2016 ARTICLES FISHING FOR SMELT, OSMERUS EPERLANUS (Linnaeus, 1758) A traditional food fish – possible cuisine in post-modern Sweden? INGVAR SVANBERG, MADELEINE BONOW, STANISŁAW CIOS Ingvar Svanberg, Uppsala Centre for Russian Studies, Uppsala University, e-mail: ingvar.svanberg @ucrs.uu.se, Madeleine Bonow, School of natural science, technology and environmental studies, Södertörn University, Stockholm, Sweden, e-mail: [email protected], Stanisław Cios, Polish Ministry of Foreign Affairs, Warsaw, e-mail: [email protected]. 1 For the rural population in Sweden, fishing in lakes and rivers was of great importance until recently. Many fish species served as food or animal fodder, or were used to make glue and other useful products. But the receding of lakes in the nineteenth century, and the expansion of hydropower and worsening of water pollution in the twentieth, contributed to the decline of inland fisheries. At the same time, marine fish became more competitive on the Swedish food market. In some regions, however, certain freshwater species continued to be caught for household consumption well into the twentieth century.
    [Show full text]
  • Cellular Energy Allocation in the Estuarine Mysid Shrimp Neomysis Integer (Crustacea: Mysidacea) Following Tributyltin Exposure
    Journal of Experimental Marine Biology and Ecology 288 (2003) 167–179 www.elsevier.com/locate/jembe Cellular energy allocation in the estuarine mysid shrimp Neomysis integer (Crustacea: Mysidacea) following tributyltin exposure Tim Verslyckea,*, Jordy Vercauterenb, Christophe Devosc, Luc Moensb, Pat Sandrac, Colin R. Janssena a Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, J. Plateaustraat 22, B-9000 Ghent, Belgium b Laboratory for Analytical Chemistry, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium c Laboratory for Organic Chemistry, Ghent University, Krijgslaan 281 S4, B-9000 Ghent, Belgium Received 7 October 2002; received in revised form 3 December 2002; accepted 13 December 2002 Abstract Recently, we described the cellular energy allocation (CEA) methodology to asses the effects of abiotic stress on the energy metabolism of the estuarine crustacean Neomysis integer (Crustacea: Mysidacea) [J. Exp. Mar. Biol. Ecol. 279 (2002) 61]. This short-term assay is based on the biochemical assessment of changes in the energy reserves (total carbohydrate, protein and lipid content) and the energy consumption (electron transport activity), and has been shown to be predictive of effects at the population level in daphnids [J. Aquat. Ecosyst. Stress Recovery 6 (1997) 43]. In the present study, the CEA methodology was evaluated using adult N. integer exposed for 96 h to the antifoulant tributyltinchloride (TBTCl). From a range-finding experiment with juvenile N. integer, a 96-h LC50 of 164 ng TBTCl/l was calculated. The energy metabolism of N. integer,as summarized by the CEA, was significantly altered by TBTCl exposure. Mysids exposed to 10, 100 and 1000 ng TBTCl/l consumed less energy and had lower respiration rates (in 10 and 1000 ng TBTCl/l treatments) than the control, resulting in a lower CEA.
    [Show full text]
  • Smelt (Osmerus Eperlanus L.) in the Baltic Sea
    Proc. Estonian Acad. Sci. Biol. Ecol., 2005, 54, 3, 230–241 Smelt (Osmerus eperlanus L.) in the Baltic Sea Heli Shpileva*, Evald Ojaveerb, and Ain Lankova a Pärnu Field Base, Estonian Marine Institute, University of Tartu, Vana Sauga 28, 80031 Pärnu, Estonia b Estonian Marine Institute, University of Tartu, Mäealuse 10a, 12618 Tallinn, Estonia; [email protected] Received 6 September 2004, in revised form 1 December 2004 Abstract. Smelt, a cold-water anadromous fish, has well adapted to the conditions in the brackish Baltic Sea and has formed local populations. The species is common in coastal waters but the most important marine smelt stocks are confined to the areas where the water of low temperature and relatively high oxygen content persists year round, in the neighbourhood of large estuaries and lagoons. The abundance of smelt is higher in the northern and eastern Baltic: in the Gulf of Bothnia, eastern Gulf of Finland, Gulf of Riga, and Curonian Lagoon. Smelt populations of these areas differ in growth rate, maturation, reproduction conditions, abundance and catch dynamics, etc. Smelt reproduction depends on temperature, it starts and finishes earlier in the southern areas than in the north. The growth rate of the fish is higher in the south and decreases towards north. In the Gulf of Riga the size of younger smelt has increased since the end of the 1960s. However, beginning with the early 1990s the weight of older fish has declined. Key words: smelt stocks, abundance dynamics, growth, reproduction. INTRODUCTION European smelt Osmerus eprlanus L. populates brackish waters in the Baltic Sea.
    [Show full text]
  • Effect of the Diversity, Ecology and Composition of Species of Fish on the Odonate Community
    Effect of the Diversity, Ecology and Composition of Species of Fish on the Odonate Community Daniel Andersson Supervisor: Göran Sahlén Master Thesis in Applied Ecology 20p Halmstad University, 2005-2006 1 Effect of the Diversity, Ecology and Composition of Species of Fish on the Odonate Community Abstract Fish is considered to be a keystone predator in freshwater habitats. Several studies have shown that the species composition of odonates (Odonata) is different between habitats with and without fish, and that odonates depending on the behaviour and physical characteristics of the individual species react differently to the presence of fish, some positively, some negatively and others not at all. This study aims to study the effect of fish as predators on the odonate community, and especially the little studied effect of the presence and composition of different ecological groups of fish in lakes. 92 Swedish lakes were surveyed for abundances and species compositions of odonates. The composition of fish species in the lakes was determined from official sources and divided into seven ecological groups. While several of the tests for potential interactions between fish and odonates resulted in no significance, the discrimination analyses of the different ecological groups of fish tested against odonate species composition did reveal high classification coefficients, indicating that different ecological groups have different odonate communities. Number of species of fish did also have a fairly high classification coefficient in a discriminant analysis. A combined plot show that two categories of lakes are separating from the others in odonate composition. Both these categories lacked some littoral groups of fish, indicating that littoral fish species may have a strong influence on the odonate community.
    [Show full text]