Interim report of the HELCOM CORESET project

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Zooplankton-phytoplankton
biomass ratio
Long-term means + expert judgement.
Phytoplankton diversity Long-term means + expert judgement.
Seasonal succession of functional
phytoplankton group
Long-term means + expert judgement.
Alkylphenols Environmental Quality Standards for nonyl- and octylphenol
Vitellogenin induction A level not showing feminization of male fi sh
AChE inhibition BAC established and EAC estimated.
EROD/CYP1A induction BAC is under development.
4.1. Distribution of harbour porpoise
1. Working team: Marine Mammals
Author: Stefan Braeger
2. Name of candidate indicator
Geographical distribution of the critically endangered
Baltic Proper harbour porpoise
3. Unit of the candidate indicator
Presence as indicated by the frequency of registrations
per area in a year
(e.g., >10 registrations/1000km 2 )
4. Description of proposed indicator
The current population size of the Baltic harbour porpoise is extremely small and due to its low abundance
no longer reliably quantifi able. Therefore, it appears impracticable to propose the abundance of
harbour porpoise as a state indicator or a quantitative target for abundance as a conservation goal. At
extremely low densities, such target would be almost impossible and very costly to monitor. The Baltic
porpoise population has not only dwindled in numbers to less than 250 reproducing adults (IUCN 2008)
but also evacuated large parts of its historic range throughout the Baltic Proper. Therefore, the extent
of the distribution range appears to be a suitable proxy for population size assuming that an increasing
population would also be likely to expand its range.
Annecdotal information on (pre-industrial) porpoise distribution indicates a probably continuous distribution
throughout the Baltic Proper, possibly also covering the entire Gulf of Bothnia as well. Therefore, a
regular basin-wide presence could serve as proxy for successful population recovery.
5. Functional group or habitat type
Harbour Porpoise (a piscivorous top predator)
6. Policy relevance
Habitats Directive, Marine Strategy Framework Directive, and national obligations under a number of
IGO resolutions (e.g., HELCOM, OSPAR, CMS, ASCOBANS etc.).
MSFD Descriptor 1, criterion 1.1 Species distribution.
The Baltic Sea Action Plan calls for “Abundance, trends, and distribution of Baltic harbour porpoise”
as preliminary indicator for nature conservation and biodiversity. To achieve a viable population of this
species, it provides the following targets: “By 2012 spatial/temporal and permanent closures of fi sheries
of suffi cient size/duration are established thorough the Baltic Sea area” and “By 2015 by-catch of
harbour porpoise, seals, water birds and non-target fi sh species has been signifi cantly reduced with the
aim to reach by-catch rates close to zero”
7. Use of the indicator in previous assessments
ASCOBANS, e.g. in the Jastarnia Plan (2002 & 2009).
8. Link to anthropogenic pressures
Directly linked to gillnet fi sheries, persistant organic pollutants, underwater noise (e.g., from pile-driving,
underwater explosions, seismic surveys, military sonar), disturbance from shipping, and habitat destruction
(e.g. from gravel extraction, offshore structures, coastal development) among others.