Karlsson, M., Pihl, L., Bergström, L. Assemblage structure and functional traits of littoral fish in Swedish coastal waters. In manus.

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1 WATERS Deliverable Title: Assemblage structure and functional traits of littoral fish in Swedish coastal waters Authors: Karlsson, M., Pihl, L., Bergström, L. Type: Submitted article Summary This is a summary of deliverable 1 within work package 3.4 (Coast - Fish) of WATERS 1. We have assessed species composition of coastal fish communities (0-30 m depth) along the Swedish coastline, from Skagerrak to the Bothnian Bay, based on data from national monitoring programs, mapping activities and research projects in the years The results show how changes in species composition relate to the gradient of decreasing salinity, and how this is reflected in patterns of species richness and functional properties of the fish communities. The study serves as a reference material for species composition in different geographic areas of Swedish coastal waters, and will be used in the continued work as a basis for recommendations on geographical and taxonomical delineations of status indicators. Background Work Package 3.4 of WATERS is designed to develop ecological status assessment tools for coastal fish communities. Fish communities are not formally included as a biological quality element within the Water Framework Directive 2, but can be included as a complementary indicator, as motivated by the importance of fish communities for ecosystem status as a whole and within an ecosystem-based management. In addition, ecological status of fish communities is included in assessments within the Species- and Habitats Directive 3 and the Marine Strategy Framework Directive 4. The main pressures factors affecting coastal fish communities include fishing, eutrophication and climate change. As a step in the process of indicator development, we have collated and analysed data on species composition of fish communities from all parts of the Swedish coastline, to clarify how patterns of species richness and functional properties change from the Skagerrak to the Bothnian Bay. Along the Swedish coastline, salinity levels decrease gradually from circa 30 to 2 PSU, with the most prominent change occurring in the Sound. This salinity gradient affects the abundance and 1 Karlsson, M., Pihl, L., Bergström, L. Assemblage structure and functional traits of littoral fish in Swedish coastal waters. In manus /60/ EG. Europaparlamentets och rådets direktiv 2000/60/EG av den 23 oktober 2000 om upprättande av en ram för gemenskapens åtgärder på vattenpolitikens område 3 92/43/EEG. Rådets direktiv 92/43/EEG av den 21 maj 1992 om bevarande av livsmiljöer samt vilda djur och växter /56/EG. EUROPAPARLAMENTETS OCH RÅDETS DIREKTIV 2008/56/EG av den 17 juni 2008 om upprättande av en ram för gemenskapens åtgärder på havsmiljöpolitikens område (Ramdirektiv om en marin strategi)

2 distribution of all organisms, and is generally associated with a decrease in biological diversity. For fish, however, no studies have hitherto investigated patterns in species occurrence, distribution and community structure in a systematic way for the entire area. Methods Data from existing monitoring programs, mapping activities and research projects in the years were collated, in order to investigate patterns in species composition among different geographical areas, and how this is reflected in species richness and functional properties of the fish communities. In total, data from 129 sites were included in the study (Figure 1). The most common gear types used were fyke nets and gill nets, and to some extent also beach seine. Fyke nets were the dominating gear type at the Swedish west coast and gill nets in the Baltic Sea area, but this distinction was not exclusive and both methods were to some extent represented in both these regions. For comparability among areas, the analyses were based on species presence data only. The area delineations used for analyses were Skagerrak, Kattegat, the Sound, Southern Baltic Proper, Western Gotland Basin, Eastern Gotland Basin, Northern Baltic Proper, the Aland Sea, Bothnian Sea, the Quark and the Bothnian Bay (Figure 1). Data represents depths down to 30 m, with a focus on coastal areas. Where data was available, however, comparisons were also made between shallow coastal and offshore areas. Results In total, 102 species were observed. The number of species decreased from circa 70 in Skagerrak and Kattegat to in the inner parts of the Gulf of Bothnia (Table I). The decrease in marine species, along with decreasing salinity, was compensated by freshwater species, with the most prominent shift in the Sound. In the Baltic Proper, the number of marine species was about the same as the number of freshwater species. Species richness was consistently higher in coastal than in offshore areas. Analyses of difference in functional traits showed that fish communities in the Skagerrak- Kattegat area were mainly represented by migrating species, whereas the Baltic Sea sub-areas were mainly represented by more stationary species. Another prominent difference was that the proportion of benthic and demersal species was higher in Skagerrak-Kattegat, whereas the proportion of pelagic and semi-pelagic species was higher in the Baltic Sea sub-areas. In accordance, the proportion of benthic feeders was also higher in the Skagerrak-Kattegat, and the proportion of pelagic feeders and omnivores was higher in the Baltic Sea sub-areas. The results also showed that between 60 and 92 % (depending on sub-area) of all commercially important species in Sweden occur in coastal areas. Discussion Coastal areas typically have high biological diversity, which gives them a high conservation value for biological reasons, but they are also highly important for Man through their provision of goods and services. Coastal fish species contribute to ecosystem services by linking different 2

3 parts of the food web, acting both in a regulatory role (as a grazer or predator), and as food for higher trophic levels. Remarkably high shares of the coastal fish species in the study were commercial and, thus, considered an important food source for people. This study is, to our knowledge, the first one assessing changes in species composition of coastal fish communities in a systematic way along the Swedish coastline. Although the presence of differences in species composition among different geographical areas is in many parts preciously known, this information has hitherto been based on scattered information from various sources. The result may serve as a valuable reference material for species composition of coastal fish in different parts of Swedish coastal areas In the continued work within WATERS, the study will be used as a basis for identifying appropriate geographical delineations for indicators that are based on taxonomy or functional traits. Examples include the indicators Abundance/Biomass of key species of fish in coastal areas and Abundance/Biomass of important functional groups of fish in coastal areas, as suggested for reporting within the MSFD 5. The results indicate that the biologically most relevant geographical delineation for status assessment of coastal fish is probably larger than required within the WFD, and smaller than within the MSFD. The results also indicate that the baseline for good ecological status, within each geographical area, should be defined with awareness of the natural differences in species richness and functional traits among geographical areas and habitats. The complete study will be submitted for publication in a scientific journal. By publication, a link to the paper will be provided here. 5 Havs- och vattenmyndigheten God havsmiljö Del 2: God miljöstatus och miljökvalitetsnormer. 3

4 Figure 1 Sites included in the study. Abbreviations denotes the geographical areas assessed: Skagerrak (S), Kattegat (K), the Sound (TS), Southern Baltic Proper (SBP), Western Gotland Basin (WGB), Eastern Gotland Basin (EGB), Northern Baltic Proper (NBP), Aland Sea (AL), Bothnian Sea (BS), the Quark (Q) and the Bothnian Bay (BB). 4

5 Table 1 Species observed in coastal fish surveys and shallow offshore areas (0-30 m depth). Species (Scientific name) S K TS SBP WGB EGB NBP AL BS Q BB Lepidorhombus whiffiagonis Micrenophrys lilljeborgii Pomatoschistus pictus Trisopterus esmarkii Trachinus draco Trisopterus luscus Trisopterus minutus Scomber scombrus Nerophis lumbriciformis Pollachius pollachius Pomatoschistus microps Microstomus kitt Eutrigla gurnardus Hippoglossoides platessoides Labrus bergylta Labrus mixtus Dicentrarchus labrax Ciliata mustela Chelon labrosus Callionymus lyra Callionymus maculatus Aphia minuta Anarhichas lupus Buglossidium luteum Chelidonichthys lucerna Chirolophis ascanii Enchelyopus cimbrius Engraulis encrasicolus 5

6 Species (Scientific name) S K TS SBP WGB EGB NBP AL BS Q BB Melanogrammus aeglefinus Merluccius merluccius Molva molva Raja clavata Squalus acanthias Agonus cataphractus Arnoglossus laterna Centrolabrus exoletus Ctenolabrus rupestris Entelurus aequoraeus Gobiusculus flavescens Mullus surmuletus Phrynorhombus norvegicus Pollachius virens Raniceps raninus Scophthalmus rhombus Solea solea Symphodus melops Syngnathus acus Syngnathus rostellatus Trachurus trachurus Zeugopterus punctatus Liparis montagui Limanda limanda Merlangius merlangus Neogobius melanostomus* Spinachia spinachia Pomatoschistus minutus Pungitius pungitius Scophthalmus maximus 6

7 Species (Scientific name) S K TS SBP WGB EGB NBP AL BS Q BB Taurulus bubalis Pleuronectes platessa Pholis gunnellus Cyclopterus lumpus Syngnathus typhle Belone belone Platichthys flesus Gadus morhua Myoxocephalus scorpius Ammodytes tobianus Hyperoplus lanceolatus Anguilla anguilla Blicca bjoerkna Scardinius erythrophthalmus Tinca tinca Vimba vimba Sander lucioperca Oncorhynchus mykiss* Phoxinus phoxinus Gobius niger Carassius carassius Salmo salar Clupea harengus Zoarces viviparus Sprattus sprattus Nerophis ophidian Salmo trutta Rutilus rutilus Gasterosteus aculeatus Coregonus lavaretus 7

8 Species (Scientific name) S K TS SBP WGB EGB NBP AL BS Q BB Esox lucius Perca fluviatilis Alburnus alburnus Leuciscus idus Gymnocephalus cernua Abramis brama Triglopsis quadricornis Lota lota Osmerus eperlanus Cottus gobio Coregonus albula Cottus poecilopus Leuciscus leuciscus Thymallus thymallus Total number of species * introduced species 8