Interim report of the HELCOM CORESET project

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Coastal Fish – Community Abundance Index (D1.6.2)
The index is based on estimates of the abundance of two different functional groups: Abundance of Cyprinids
and Abundance of Piscivores, and refl ects the integrated effects of recruitment and mortality of
the species included in each functional group. Recruitment success is expected to mainly be infl uenced by
the quality and availability of recruitment habitats, climate and eutrophication. Mortality is infl uenced by
fi shing, but predation from other animals, such as seals, sea birds and fi sh are also perceivable. The two
metrics included in the index are expected to differ in their responses to anthropogenic pressure factors, in
that Abundance of Cyprinids is expected to show the strongest link to eutrophication and Abundance of
Piscivores the strongest relationship to fi shing pressure.
Policy relevance: The index will indicate whether or not the abundance and productivity of coastal fi sh
communities is at appropriate level for supporting coastal ecosystem function and resilience, including food
provision for man and other marine organisms. In areas where the index does not signal good environmental
status, GES may be achieved by restoration of recruitment habitats for piscivores, reduction of nutrient
loads, and by regulating mortality of piscivores by reducing fi shing pressure and predation from apex
predators.
Coastal Fish - Community Trophic Index (D1.7.1)
The index refl ects the general trophic structure at the community level and is based on estimates of the
proportion of fi sh at different trophic levels. Alternatively, estimates of the proportion of piscivores in the
fi sh community may be used.
The index provides an integrated measure of changes in the trophic state of the fi sh community. Typically,
very low values of the index may refl ect high fi shing pressure on piscivores (Pauly et al. 1998) and/or
domination of species favoured by eutrophic conditions. Since high levels of the index also may refl ect a
decreased abundance of some naturally dominating non-piscivore species the index has both an upper and
a lower boundary.
Policy relevance: The indicator will show if the trophic structure of the coastal fi sh community is at appropriate
level for supporting coastal ecosystem function, including ecosystem resilience. The indicator refl ects
the general state of the fi sh community, and is likely to be closely linked to fi shing pressure as well as eutrophication.
In areas with sub-GES conditions, actions should target the species level.
Method(s) used to test the indicators
The metrics on which each index is based have previously been used for assessing the state of coastal fi sh
communities in Sweden, Finland, Estonia, Latvia and Lithuania based on data coastal fi sh monitoring programs
(as analyzed within the HELCOM Fish PRO group; HELCOM 2011).
The suggested metrics were identifi ed after evaluation of a range of parameters potentially refl ecting
coastal fi sh community status. The selection of metrics was based on multivariate analyses (PCA) of monitoring
data where the signal strength, biological relevance and redundancy of individual parameters as
suggested by Rice and Rochet (2005) were assessed (as analyzed within the HELCOM Fish PRO group; HEL-
COM 2011). In addition, the biological relevance of the metrics was mainly evaluated based on empirical
observations.
Relationship to anthropogenic pressures
The relationship between metrics and anthropogenic pressures was assessed using a data set covering the
Bothnian Bay, Bothnian Sea, Gulf of Finland and the Central Baltic Sea. Samples covered areas with different
levels of natural and anthropogenic environmental pressures, and the relationship was analysed using
distance-based linear modeling (DISTLM as implemented in PERMANOVA+ of PRIMER v6). The results in