Coastal fish community indicators in Sweden - variation along environmental gradients

Coastal fish communities have a central role in both environmental and fisheries management. The following report summarizes the current state (2014) of indicator-based approaches in Sweden, to assess the status of coastal fish communities in relation to internationally agreed directives. Coastal fish is not included as a biological quality element in the European Water Framework Directive (WFD), with the exception of transitional waters, but they are included in the European Marine Strategy Framework Directive (MSFD). The report is particularly focused on potential connection points between the MSFD and WFD, in order to facilitate the harmonisation of assessments of different ecosystem components and geographical areas. One important aspect would be to develop geographically based assessment methods, to make better use of data from inventory studies. Key aspects for this development are explored in an example case study, which is based on data with wide geographical coverage. The study addresses general patterns in the distribution of species and indicators among geographical areas in the Baltic Sea, and explores the relationship between indicators and environmental variables. Changes in the indicators were to a large extent attributed to gradients in natural environmental variables, such as temperature, salinity and wave exposure. The results indicate that all these variables should be included in a geographically based assessment. Variables attributed to eutrophication were important for five of the eight studied indicators. This was mainly coupled to a gradient in water transparency. Variables attributed to the mortality of fish were less influential. Possibly, the indicators assessed were not sensitive enough, or the studied gradient was not strong enough for evaluating this pressure. Potentially, also, the explanatory variables that were used were not quantified in an adequate way. A need was seen to update information on the geographical distribution of recreational fisheries and top predators (cormorants, seals), in order to support the assessment of pressure-state relationship, and identify connection points to management measures. All these aspects need to be considered further in the continued indicator development. The environmental variables explained a reasonable part of the observed variation in the data set, although a relatively large part of the variation was left unexplained. The unexplained variability may potentially be reduced by more refined quantitative analyses, which can also explain variation at different geographical scales. The study was also limited by available environmental data. In terms of additional explanatory variables, habitat quality is often expected to have high influence on species abundances, and hence on indicators. However, this variable could not be included, due to a lack of data with sufficient geographical coverage

Improving assessments of coastal ecosystems – Adjusting coastal fish indicators to variation in ambient environmental factors

The application of ecological indictors for assessing the environmental status of ecosystems play an important role for effective management. However, natural variability may limit the indicators’ ability to provide relevant information about anthropogenic pressures and guide management action. Coastal fish species are not only a resource for commercial and recreational fisheries but also key ecosystem components in the Baltic Sea, and is therefore used as management objectives within the EU Marine Strategy Framework Directive and the HELCOM Baltic Sea Action Plan. A challenge, however, is that the distribution and abundance of coastal fish populations in Baltic Sea is also influenced by spatial and temporal variation in ambient environmental factors. Here, using 16 years of monitoring data, over a latitudinal range of 56 – 66°N along the Swedish Baltic Sea coast, we evaluated the effect of variability in water temperature and depth, and wave exposure for three indicators of environmental status assessment in the Baltic Sea: Abundance of perch, Abundance of Cyprinids, and Abundance of Piscivores. Generalized linear mixed models (GLMM) revealed an overall positive linear relationship between water temperature for all indicators, and overall negative linear relationships to depth and wave exposure. When adjusting indicator values using the parameter estimates from the GLMM models, the variability and 95 % confidence interval for all three indicators were reduced. The adjustment, however, did not have a strong impact on the assessment of the ecological state of the indicator. Our results suggest that adjusting coastal fish indicators to variation in local ambient environmental factors will increase their precision, and hence, the confidence in the assessment of environmental status

Improving assessments of coastal ecosystems – Adjusting coastal fish indicators to variation in ambient environmental factors

The application of ecological indictors for assessing the environmental status of ecosystems play an important role for effective management. However, natural variability may limit the indicators’ ability to provide relevant information about anthropogenic pressures and guide management action. Coastal fish species are not only a resource for commercial and recreational fisheries but also key ecosystem components in the Baltic Sea, and is therefore used as management objectives within the EU Marine Strategy Framework Directive and the HELCOM Baltic Sea Action Plan. A challenge, however, is that the distribution and abundance of coastal fish populations in Baltic Sea is also influenced by spatial and temporal variation in ambient environmental factors. Here, using 16 years of monitoring data, over a latitudinal range of 56 – 66°N along the Swedish Baltic Sea coast, we evaluated the effect of variability in water temperature and depth, and wave exposure for three indicators of environmental status assessment in the Baltic Sea: Abundance of perch, Abundance of Cyprinids, and Abundance of Piscivores. Generalized linear mixed models (GLMM) revealed an overall positive linear relationship between water temperature for all indicators, and overall negative linear relationships to depth and wave exposure. When adjusting indicator values using the parameter estimates from the GLMM models, the variability and 95 % confidence interval for all three indicators were reduced. The adjustment, however, did not have a strong impact on the assessment of the ecological state of the indicator. Our results suggest that adjusting coastal fish indicators to variation in local ambient environmental factors will increase their precision, and hence, the confidence in the assessment of environmental status

Riktlinjer för uppföljning av fiskevårdsåtgärder i kustmynnande våtmarker med fokus på gädda

Längs Östersjökusten inkom under slutet av 1990- och början av 2000-talet rapporter om sviktande bestånd av gädda och abborre. Båda arterna är populära inom fritids- och sportfisket, och spelar som rovfiskar en betydande roll för tillståndet i Östersjöns kustekosystem. I flera kustområden har man börjat restaurera kustmynnande våtmarker och vattendrag som har visat sig utgöra viktiga lek- och uppväxtområden för framför allt gädda. Till skillnad mot många andra fiskevårdsåtgärder har det för flera av dessa restaureringsprojekt genomförts utförliga utvärderingar av åtgärden. Dock har det hittills saknats en samlad beskrivning över hur man kan utvärdera och följa upp effekten av en restaureringsåtgärd i kustmynnande våtmarker och vattendrag riktad mot gädda. I denna rapport har data från ett flertal kustmynnande vattendrag och våtmarker längs den svenska kusten analyserats för att utvärdera hur man bäst och mest kostnadseffektivt kan mäta effekten av en restaureringsåtgärd riktad mot gädda. Fokus i utvärderingen är huvudsakligen riktat mot undersökningar av stigande lekfisk och utvandrande yngel. Effekterna av en restaureringsåtgärd på det vuxna beståndet av gädda är idag inte klarlagt, men i denna rapport ges även förslag på hur åtgärden kan utvärderas på beståndsnivå. För uppvandring av vuxen lekfisk visar resultaten att det fanns en koppling mellan stigande fisk och vattentemperatur, och att en provtagning när vattentemperaturen ligger mellan 6-12 ºC var tillräcklig för att fånga upp en majoritet av den fisk som vandrar upp i våtmarken. Även om det fanns en variation mellan områden, så fångade denna reducerade provtagning mellan 64-97% av det totala antalet stigande lekfiskar. För yngelutvandringen inträffade en topp oftast 30-40 dagar efter en topp i uppvandrande lekfisk. En provtagning inom intervallet 30-50 dagar efter en topp i uppvandrande lekfisk fångade upp en majoritet (68-95%) av det totala antalet utvandrande yngel i våtmarken. Eftersom gäddan fångas i liten utsträckning i traditionella provfisken, diskuteras möjligheten att använda ryssjefisken i vattendrag yngelinventeringar på kusten och yrkes- och sportfiske som informationskälla och underlag för utvärdering på beståndsnivå. Framför allt en utveckling av ett rapporteringssystem inom sportfisket bedöms utgöra en potentiellt värdefull källa till information då gäddan är en populär art bland sportfiskare. Avslutningsvis visar analyserna som ligger till grund för denna rapport att produktionen av yngel i en rätt konstruerad våtmark kan producera upp till 25 000 yngel per hektar. Produktionen varierar sannolikt mycket mellan våtmarker, områden och år, men potentialen i denna restaureringsmetod bedöms som stor. Fortsatta undersökningar där variationen mellan områden i produktionen av yngel studeras, samt där kopplingar mellan åtgärden och förändringar på beståndsnivå kvantifieras, föreslås i rapporten. Sådana undersökningar kan förhoppningsvis belysa huruvida åtgärder i kustmynnande vattendag och våtmarker är en restaureringsåtgärd som bör tillämpas för att stärka bestånden av gädda på kusten, samt hur åtgärden kan optimeras

Using catch statistics from the small scale coastal Baltic fishery for status assessment of coastal fish

Healthy coastal fish stocks and communities comprise an important part of the environmental targets of the Marine Strategy Framework Directive and Baltic Sea Action Plan, both in Sweden and the Baltic Sea as a whole. As such, the status of fish communities along our coasts should be assessed and Good Environmental Status (GES) should be achieved in 2020 by using a suite of selected indicators. Many coastal fish stocks in the Baltic Sea are typically local in their appearance and response to environmental conditions. In spite of a well-developed coastal fish monitoring program in Sweden, there are still spatial gaps in its coverage limiting the potential for a full comprehensive status assessment of coastal fish. Within the commercial fishery, all fishermen are obliged to report the catches and effort of their fishery to the European Commission via daily logbooks. To date, however, the information gathered from the small-scale coastal fisheries has not been used to assess the status and development of coastal fish stocks and communities. In this report we assess the potential for using data collected within the small-scale coastal fishery for indicator development and status assessments of coastal fish by 1) screening the species targeted and gears used in the commercial fishery, 2) comparing the temporal development of indicators derived from the commercial fishery and fishery independent coastal fish monitoring, and 3) comparing the outcome of status assessments derived from indicators developed using the two sources of data. Our results show that the commercial coastal fishery in Sweden is mainly targeting cod, herring, whitefish, flounder and perch, and to a minor extent also pike and pike-perch. These species are mainly caught using gillnets, but in some areas traps or trap-nets are of importance. Catches of species of noncommercial value as roach and breams and other members of the carp family are very low or not registered, and the data is hence limited to a few species of commercial importance. We found an overall weak match and substantial variation across coastal areas between indicators derived from the commercial fishery and fisheries independent monitoring data. There was, however, a reasonable concordance between the Abundance of large perch (above 25 cm) from monitoring data and catch-per-unit-effort (CPUE) of perch in the commercial fishery. When assessing the environmental status of the fish communities based on indicators derived from the two sources of data, there was a rather good overall match in GES for the indicators Abundance of perch, Abundance of large perch and Abundance of piscivores and CPUE based indicators from the commercial fishery. The match was lower for the indicator Abundance of large piscivores and indicators ignoring effort data in the commercial fishery. Our results suggest that CPUE data from the coastal commercial fishery could potentially be used as a complement and give additional support for status assessments of coastal fish in Sweden, particularly for the indicator Abundance of large perch. Since no information on size structure or the abundance of species of low commercial value could be obtained from the coastal commercial fisheries statistics, the data reported is in its current form of limited use for more detailed assessments of coastal fish communities. This regards important parameters such as size structure and the abundance of important functional groups as carp fishes. The fisheries statistics includes many sources for potential errors, but there are some means that can be used to increase the value of this data for assessments. The quality of the reporting can be improved, a selected number of coastal fishermen can be contracted for more detailed self-reporting of their catches and efforts. It is especially important to focus on registration of by-catch (both undersized fish of focal species and species of non-commercial value), subsampling for length and age estimates, and improved resolution of the effort and fishing location. This would be especially valid for those species and stocks that we have limited information on in the fishery independent gillnet monitoring programs as for example whitefish, pike-perch, pike and flatfishes

Evaluating complex relationships between ecological indicators and environmental factors in the Baltic Sea : A machine learning approach

The state of marine ecosystems is increasingly evaluated using indicators. The indicator assessment results need to be understood in the context of the whole ecosystem in order to understand the key factors determining the status of these environmental components. Data available from the system’s different components are, however, often heterogeneous: they may represent different spatial and temporal scales, and different parameters can be measured with different accuracy. This makes it difficult to evaluate the relationship between these variables and status of the environment using indicators. We studied whether probabilistic, machine learning-based classifiers could provide for assessing the relationships between multiple environmental factors and ecological indicators. This paper demonstrates the use of Bayesian network classifiers (Tree-augmented Naive Bayes classifier, TAN as the specific case example), used together with structural learning from data and Entropy Minimization Discretization (IEMD) algorithm to study environment-indicator relationships within coastal fish communities in the Baltic Sea. By using two Baltic-wide indicators of coastal fish community status and a heterogeneous set of potentially influential natural and anthropogenic variables, we explore and discuss the potential of the approach. Given pre-defined cutting points for the indicators, such as the classification thresholds of the indicator, the method enables identifying relevant variables and estimating their relative importance. This information could be used in environmental management to demonstrate at which threshold value the state of an indicator is likely to respond to a pressure or a combination of pressures. In contrast to many other multivariate statistical methodologies, the presented approach can handle missing data as well as data of varying types, from fully quantitative to presence-absence, in the same analysis.peerReviewe

Increases of opportunistic species in response to ecosystem change:The case of the Baltic Sea three-spined stickleback

Under rapid environmental change, opportunistic species may exhibit dramatic increases in response to the altered conditions, and can in turn have large impacts on the ecosystem. One such species is the three-spined stickleback (Gasterosteus aculeatus), which has shown substantial increases in several aquatic systems in recent decades. Here, we review the population development of the stickleback in the Baltic Sea, a large brackish water ecosystem subject to rapid environmental change. Current evidence points to predatory release being the central driver of the population increases observed in some areas, while both eutrophication and climate change have likely contributed to creating more favourable conditions for the stickleback. The increasing stickleback densities have had profound effects on coastal ecosystem function by impairing the recruitment of piscivorous fish and enhancing the effects of eutrophication through promoting the production of filamentous algae. The increase poses a challenge for both environmental management and fisheries, where a substantial interest from the pelagic fisheries fleet in exploiting the species calls for urgent attention. While significant knowledge gaps remain, we suggest that the case of the Baltic Sea stickleback increase provides generalisable lessons of value for understanding and managing other coastal ecosystems under rapid change

Biologisk recipientkontroll vid Forsmarks kärnkraftverk

Denna rapport sammanfattar långsiktiga och pågående trender ikustvattenmiljön utanför Forsmarks kärnkraftverk från mitten av 1970-taletfram till och med år 2012. Resultaten baseras på de fältundersökningar somutförs inom kärnkraftverkets kontrollprogram för att följa effekter avkylvattenanvändning på fisk, fågel och bottenfauna.Vid Forsmarks kärnkraftverk pumpas stora mängder brackvatten genomkraftverket för att kyla kondensorerna. Efter användning pumpas detanvända kylvattnet ut i närrecipienten, som får en temperaturhöjning medcirka 7-9°C. Kylvattenhanteringen har en direkt miljöpåverkan genom attdet havsvatten som används innehåller levande organismer som dras med ini systemet, eller filtreras bort vid intaget och dör. Det uppvärmda kylvattensom når närrecipienten har därtill effekter på djurens fysiologi, födotillgångoch beteendemönster, vilket i sin tur kan påverka deras tillväxt ochreproduktion. Dessa förändringar är väl dokumenterade under de år somkontrollprogrammet har pågått, framförallt när det gäller fisk. I rapportenpresenteras trender i utvecklingen över tid hos fisk, bottenfauna och fågel.Data jämförs där det är möjligt med motsvarande trender i referensområdensamt i andra delar av Bottenhavet och Östersjön.En stor del av de förändringar som observerats i Forsmarks skärgårdunder senare år kan sannolikt sammankopplas med kylvattenutflödet, isynnerhet efter år 2004 när det galler som tidigare hindrade fiskar från attvandra in och ut ur Biotestsjön togs bort. Detta syns som en ökad invandringav lekfisk i Biotestsjön och en tillkomst av arter som inte funnits där pålänge. Samtidigt ses förändrade tillväxtmönster hos abborre i Biotestsjönsamt utanför, i Forsmarks skärgård. I viss mån ses även förändradeutbredningsmönster hos sjöfågel som skulle kunna kopplas till förändradfödotillgång. För bottenfauna kan man inte avgöra om det finns mönster, pågrund av avsaknad av data under senare år.Resultaten antyder att en större del av fiskbestånden i Forsmarks skärgårdän tidigare är beroende av att Biotestsjön är en fungerande miljö förreproduktion och tillväxt. Detta är positivt så länge förhållandena iBiotestsjön och övriga områden som påverkas av kylvattenutsläpp ärgynnsamma, men negativt för omgivande skärgård om rekryteringen i dessaområden inte skulle fungera, eller om fiskens hälsa skulle påverkas. Dessaaspekter blir särskilt aktuella i och med den planerade effekthöjningen vidForsmarks kärnkraftverk, som sannolikt skulle kunna accentuera deobserverade effekterna, samt den planerade byggnaden av ett slutförvar, om denna påverkar tillgången på alternativa rekryteringsmiljöer för fisk inärområdet.Dödligheten i silstationen är fortsatt hög, om än med stormellanårsvariation i antal och artsammansättning. Mätningar vid silstationenvisar dock på en ökad dödlighet av ål, som inte kan förklaras av generellauppgångar i beståndet. Ökningen är troligen en effekt av att mer ål äntidigare vistas i Forsmarks skärgård, vilket skulle kunna bero på enanlockning av ål till området för kylvattenutsläpp.En annan förändring som inträffat under senare år är att en nyintroducerad art, musslan Mytilopsis leucopheata, har observerats i områdetsedan 2011. Arten har orsakat problem i kylvattenvägarna i andrakärnkraftverk i Östersjön, och områden med förhöjd vattentemperatur hartidigare identifierats som potentiella plattformar för fortsatt etablering avarten i andra områden