Interim report of the HELCOM CORESET project

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4.10. Large fi sh individuals from fi shery-based data sources
1. Working team
MARMONI Life –project (Antti Lappalainen et al.)
2. Name of candidate indicator
Large fi sh individuals (complement)
3. Unit of the candidate indicator
Proportion of large fi sh individuals in fi sh populations.
Mean size of sexual maturation.
4. Description of proposed indicator
The original core indicator “Large fi sh individuals” is monitored in HELCOM FISH project by gill nets.
Perch and some Cyprinids typically form the bulk of the catch. Other data sources, such as coastal trawl
surveys, can be used in order to get population level data from a wider group of species The fi sh catch
data collected under the EU Data Collection Regulation is also a source which can be used for this indicator.
A part of this data, e.g sampling of predatory species from herring traps, covers all size classes and
can be treated here as fi shery independent data.
These data can be used e.g. to calculate:
Proportion of fi sh larger than the mean size of fi rst sexual maturation
mean size at fi rst sexual maturation
These issues (1 and 2) are closely linked to effects of fi shing pressure on fi sh populations and on population
level biodiversity.
In the Marmoni –project, Finland (FGFRI) will shortly evaluate the usability of the fi shery data (EU Data
Collection regulation) and national trawl survey data for this kind of indicators. This work will be focused
on pike-perch. In Estonia (EMI), there are long time series of trawling survey data, which might be used
to assess the effects of fi shery on pike-perch stocks. The usability of coastal commercial catch data to
monitor the state of coastal fi sh stocks will be evaluated out, too. Latvia has long time series of trawling
survey data, too, and the data will be evaluated in the Marmoni –project.
10. Spatial considerations
Valid in the entire Baltic Sea.
11. Temporal considerations
12. Current monitoring
Fishery dependent data (catch samples from commercial fi shery) is collected by all countries under the
EU Data Collection Regulation. Trawling surveys are also carried out in several countries around the Baltic
Sea.
13. Proposed or perceived target setting approach with a short justifi cation.
GES boundaries not set yet. Reference conditions could be based on fi shery independent monitoring
results from earlier time period(s). There is also a general principle that every fi sh individual should have a
chance to spawn at least once before they are targets for effective fi shery