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Assessment of Coastal Fish in the Baltic Sea

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Assessment of Coastal Fish in the Baltic Sea Baltic Sea Environment Proceedings No. 103 A Assessment of Coastal Fish in the Baltic Sea Helsinki Commission Baltic Marine Environment Protection Commission Baltic Sea Environment Proceedings No. 103 A Assessment of Coastal Fish in the Baltic Sea Helsinki Commission Baltic Marine Environment Protection Commission Authors: Kaj Ådjers1), Jan Andersson2), Magnus Appelberg3), Redik Eschbaum4), Ronald Fricke5), Antti Lappalainen6), Atis Minde7), Henn Ojaveer4), Wojciech Pelczarski8) and Rimantas Repečka9). 1)Co-ordination Organ for Baltic Reference Areas, Provincial Government of Åland Islands, Fisheries Division, P.O. Box 1060, AX-22111 Mariehamn, Åland Islands 2)Swedish Board of Fisheries, Institute of Coastal Research, Ävrö 16, S-572 95 Figeholm, Sweden 3)Swedish Board of Fisheries, Institute of Coastal Research, Box 109, S-74071 Öregrund, Sweden 4)Estonian Marine Institute, University of Tartu, Mäealuse 10 A, EE-12618 Tallinn, Estonia 5)State Museum of Natural History, Rosenstein 1, D-70191 Stuttgart, Germany 6)Finnish Game and Fisheries Research Institute, P.O. Box 6, FIN-00721 Helsinki, Finland 7)Latvian Fish Resources Agency, Daugavgrivas street 8, LV-1048 Riga, Latvia 8)Sea Fisheries Institute (MIR), Kollataja 1 Str, PL- 81332, Poland 9)Institute of Ecology, Vilnius University, Akademijos Street 2, LT-08412 Vilnius 21, Lithuania Language check: Janet Pawlak For bibliographic purposes this document should be cited as: HELCOM, 2006 Assessment of Coastal Fish in the Baltic Sea Balt. Sea Environ. Proc. No. 103 A 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 - Cover photo: Johnny Jensen Design and layout: Bitdesign, Vantaa, Finland Printed by: DMP – Digital Media Partners Oy, Finland ISSN 0357-2994 Table of Contents Summary . 4 Introduction . 5 Sampling programme used in coastal fi sh monitoring . .6 Factors infl uencing the structure of the fi sh populations and communities in the Baltic Sea . 10 Temperature . 10 Salinity . 10 Eutrophication . .10 Fisheries . .11 Other important factors . 11 Ecological indicators . 13 Species richness . .13 Index of abundance . 13 Index of biomass . .14 Ratio between European perch/roach based on weight . 15 Trophic level of fi sh communities . 16 Piscivorous fi sh . 17 Threatened and declining species . 18 Non-indigenous fi sh . .19 Discussion and recommendations . 20 References . .22 Assessment of Coastal Fish in the Baltic Sea 3 Summary Coastal fi sh communities are important com- ence the structure of the local fi sh community. ponents of Baltic Sea ecosystems. These com- High fi shing pressure during the 1990s in the munities consist of fi sh of various origins: marine West-Estonian archipelago, which caused a col- species, freshwater species, migratory species, lapse in the coastal fi sh stocks, was apparent in and glacial relicts. Representatives of all these the monitoring catches. categories have different preferences for environ- mental conditions. For example, marine fi sh prefer The report recommends the inclusion of 34 spe- more saline areas, freshwater fi sh prefer less cies considered to be of high priority for conserva- saline areas, and glacial relicts are more abundant tion, 70 species of medium priority, and 80 species in cold-water layers in deeper areas. The compo- of low priority into the HELCOM Red List of threat- sition of coastal fi sh communities varies in the ened and declining Baltic fi sh species. Although different regions of the Baltic Sea in relation to the the spread of non-indigenous species has been different habitat characteristics of these regions, suggested to be among the most severe threats with salinity, water temperature, and nutrient to global biodiversity, the signifi cance of most availability among the important factors. Other non-indigenous fi sh species introduced into the important factors include seabed type for bottom- Baltic Sea remains of less importance since they dwelling fi sh, and algal and seagrass conditions in have failed to form self-sustaining populations. shallow waters for near-coastal species. However, two species, the accidentally introduced round goby (Neogobius melanostomus) and the Monitoring of coastal fi sh using multi-mesh gill- intentionally introduced Prussian carp (Carassius nets and gillnet series has been carried out in gibelio), are exceptions in this respect. In particu- fi fteen areas in the Baltic Sea. The objectives of lar, the round goby is spreading, and new records this monitoring are to describe and elucidate long- of its occurrence are reported every year. term trends in fi sh populations and fi sh community development, and to try to explain the results in relation to natural factors and anthropogenic pres- sures. This report covers current time series of varying length up to 22 years of annual monitoring. The development of coastal fi sh stocks has been evaluated using indicators such as species rich- ness, species abundance in terms of numbers and weight, a weight-based ratio between European perch and roach, trophic levels, the abundance of piscivorous fi sh, and the occurrence of non- indigenous species. A brief summary of the threat status of Baltic fi sh species is also presented. Signifi cant increasing trends in European perch and roach catches per unit effort have been observed in the Archipelago region between the southern Gulf of Bothnia and the northern Baltic Proper. A possible reason for these trends is ongoing coastal eutrophication as well as increased temperatures during the past decade. On the other hand, some roach populations in the Baltic Proper have shown decreasing trends in relative abundance. The Curonian lagoon and the river mouth of the Daugava are areas severely affected by anthropogenic impacts, which infl u- 4 Introduction The Baltic Sea ecosystems have undergone dra- the fi sh community, HELCOM is in the process of matic changes during the late 20th century, as a developing ecological quality objectives. Some result of both human activities and natural factors. suggested objectives have been presented in This is also true for the fi sh communities in coastal the “Discussions and recommendations” section areas. Coastal fi sh are subjected to a number of of this report. A number of potential indicators anthropogenic impacts such as enhanced nutri- that can be used for assessing ecological quality ent loads, contamination by heavy metals, organic objectives based on the coastal fi sh monitoring toxicants and hormone-like substances, as well as programme have been discussed in HELCOM the destruction of recruitment habitats. Changes workshops (BSRP/HELCOM, 2005). In this in mortality rates caused by increased fi shing assessment, a selected set of indicators has been pressure and increased predation by seals and proposed to describe the status of and temporal cormorants also infl uence fi sh community devel- trends in the coastal fi sh fauna in the Baltic Sea. opment. Changes related to the introduction of These indicators are: species richness, relative non-native species may also ultimately represent abundance (catch per unit effort) of species, the a substantial threat to the coastal fi sh fauna. ratio between functional groups, and the trophic level of fi sh communities. In an effort to improve the state of the Baltic marine environment, and thus also reduce pressures on Assessment of Coastal Fish in the Baltic Sea 5 Sampling programme used in coastal fi sh monitoring At present, a network of coastal fi sh monitoring areas covering large areas of the Baltic Sea is sampled annually. The network comprises moni- toring areas in Estonia, Finland, Latvia, Lithuania, Poland, and Sweden. Coastal areas in Denmark, Germany, and Russia are monitored as well, but have not been included in this assessment. This monitoring is coordinated by the “Co-ordination Organ for Baltic Reference Areas” (COBRA), which maintains a database containing coastal fi sh monitoring results collected from participating monitoring areas. The monitoring programme in 2005 covered fi fteen monitoring areas (Figure 1). Four of these include two sub-areas (Curonian lagoon, Hiiumaa, Kvädöfjärden, and Holmöarna) that represent different environmental conditions and, consequently, the fi sh communities may Figure 1. differ between these sub-areas. The time series Sampling cover variable periods, depending on area, up to locations for 22 years of annual monitoring, with the year 2004 coastal fi sh monitoring being the last year included in the present assess- under the ment. Four areas were added to the network in COBRA 2004: Torhamn in southern Sweden, Lagnö in the programme, northern archipelago of Stockholm, Haapasaaret including the gear in the Gulf of Finland, and Kumlinge in the eastern used and the archipelago of the Åland Islands. As the monitor- fi rst year of ing method in Poland differs markedly from the sampling. others, Polish results have not been included in Coastal fi sh monitoring in the Baltic Sea 2004 this report. Area Gear Start year Råneå Coastal survey nets 1994 The coastal fi sh monitoring programme is mainly Råneå Nordic coastal nets 2002 directed towards species of demersal fi sh (fi sh Holmöarna Coastal survey nets 1989 living close to the bottom) and benthopelagic fi sh Holmöarna Nordic coastal nets 2002 (fi sh living both close to the bottom and in the Forsmark Coastal survey nets 1983 open water) that live in coastal areas
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