Assessing Coastal Fish in the Baltic

Region's coastal fish communities have changed dramatically during the late 20th century. Photo: David Andersson

 

HELCOM's Indicator-based assessment of coastal fish community status in the Baltic Sea has been finalized.

 

Coastal fish communities are an important part of Baltic Sea ecosystems and they are also of great importance to human society in the Baltic region, both from a socio-economic and cultural point of view. There have been dramatic changes in the region’s coastal fish communities during the late 20th century, which has resulted in an increased focus on this component of the Baltic Sea system.

 

The most recent assessment on these fish communities has recently been finalized and published on the HELCOM website as No. 131 in the Baltic Sea Environmental Proceedings (BSEP) series. The new indicator-based assessment covers the years 2005-2009 and responds to the requests by the Baltic Sea Action Plan (BSAP) to reassess the status of the Baltic Sea coastal fish and to define methods for assessment.

 

“In my opinion, one of the most important results of the coastal fish assessment is that we have developed a strategy to select indicators in an objective way to assess the status of coastal fish communities that should be applicable across monitoring areas and methods. By doing this, we have developed a sound and good basis for how to assess the status of fish communities for international commitments such as the Baltic Sea Action Plan (BSAP) and EU Marine Strategy Framework Directive (MSFD),” says Jens Olsson, Project Manager of HELCOM FISH-PRO Expert Group.

 

Persistent monitoring of the effects

Coastal fish communities are impacted by human activities, including fishing, nutrient discharges, and heavy metals, and contaminants from agriculture, industry, municipalities and shipping. Eutrophication, together with changes in water temperature and salinity, is a major factor influencing the composition and long-term development of the Baltic fish community and causes increased production of fish biomass and changes in the fish community structure and function.

 

To determine the potential effects of human activities on coastal fish communities, the activities of the network of experts on coastal fish monitoring started in 2003 under the World Bank/GEF funded Baltic Sea Regional Project, continued under the HELCOM FISH Project during 2008-2010, and goes on today under the HELCOM FISH-PRO project. The first status assessment based on the monitoring data was published in 2006 (BSEP 103 A & B).

 

Several species' response examined

The coastal fish monitoring is to be conducted according to a specific procedure (HELCOM COMBINE manual) following a standardised protocol, which mediates comparisons of results among monitoring areas.

During the latest assessment period, a total of 44 fish species were recorded, the most commonly occurring species being European perch (Perca fluviatilis), roach (Rutilus rutilus), ruffe (Gymnocephalus cernuus) and Baltic herring (Clupea harengus).

 

“What is rather novel is that we promote a more community-based approach incorporating the response of several species, than focusing on single-species assessments as is the current practice in fisheries science. Besides this I think it is timely to produce a new thematic assessment of coastal fish communities, and the results suggest that there are divergent development trajectories of the assessed communities in the Gulf of Bothnia and Baltic Proper,” Mr. Olsson points out.

 

“The coastal fish monitoring is very important since it serves as the basis for following aspects of biodiversity for many of our non-TAC (Total Allowable Catch) species in the Baltic. Coastal fish species are also of high-socio economic values around the Baltic, are key elements in the coastal food-webs and as such reflect the general status of coastal ecosystems in the Baltic.”

 

Three methods are used for monitoring the coastal fish communities around the Baltic Sea. In the Baltic Proper, the longest time series are from monitoring using Net series, and in the Gulf of Bothnia, from monitoring using Coastal survey nets. Monitoring using Nordic coastal multi-mesh nets was introduced in 2001 and is so far only used in Finland, Poland and Sweden.

This work has also served as the basis for assessing coastal fish community status within the HELCOM CORESET project during 2011 and 2012.

 

Expanding the work to more Baltic experts

As for the future, Jens Olsson has a few suggestions: “The future road-map of this work is to incorporate more aspects of the communities (such as recruitment status and status of juveniles) in future assessments, to develop the relationship between state indicators and important anthropogenic and natural pressures, and also to widen the geographic perspective of the group by including experts from all Baltic Sea countries in the work.”

 

For more information, see the Indicator-based assessment of coastal fish community status in the Baltic Sea 2005-2009 (BSEP No. 131)