Seal populations in the Baltic HELCOM Workshop on Seal-Fisheries - - PowerPoint PPT Presentation

Seal populations in the Baltic

HELCOM Workshop on Seal-Fisheries Interactions Copenhagen, 27.06.2019 Markus Ahola – Swedish Museum of Natural History, SE Anders Galatius - Aarhus University, DK Mart Jüssi - Pro Mare, EE

• Common basis for monitoring - HELCOM

Recommendation 27/28-2

• Three seal species: grey seal, ringed seal,

harbour seal

• Current status and perspectives for the

future

• Good environmental Status (GES) and

HELCOM assessment (HOLAS II)

Seal populations in the Baltic

The HELCOM Recommendation 27/28-2 (The Seal Recommendation)

NOTING that the proposed General Management Principles are the following which link the seal populations to the Baltic Sea Ecosystem: · populations size (with the long-term objective to allow seal populations to recover towards carrying capacity levels); · distribution (with the long-term objective to allow breeding seals to expand to suitable breeding distribution in all regions of the Baltic); and · health status (with the long-term objective of attaining the health status that secures the continued existence of the populations);

The HELCOM Recommendation 27/28-2 (The Seal Recommendation)

ALSO NOTING that the HELCOM/ICES/EU Seal Expert Workshop defined and agreed on the following Management Units for Baltic Sea seal populations: 1) Harbour seals in the Kalmarsund region (Sweden); 2) Southwestern Baltic harbour seals (Denmark, Germany, Poland, Sweden); 3) Gulf of Bothnia ringed seals (Finland, Sweden); 4) Southwestern Archipelago Sea, Gulf of Finland and Gulf of Riga ringed seals (Finland, Estonia, Latvia, Russia); 5) Baltic Sea grey seals (all Contracting Parties to the Helsinki Convention);

Current monitoring methods for abundance

• Counts are aerial surveys during peak

moulting period

– Ringed seals after mid-April – Grey seals in late May - early June – Harbour seals in mid-August

• During their annual moult seals spend the

largest proportion of their time hauling out

• n land or ice and

are available for counting

• The monitoring in Baltic is

internationally coordinated among experts in HELCOM EG MAMA

HS GS RS RS

Current monitoring methods for distribution

• Distribution in the sense of Seal

Recommendation management objective deals with breeding distribution

• In many management applications

distribution of known haul-outs is used, e.g. for defining special protected areas or assessing environmental impacts. BUT

• The seals can move freely in the

marine environment and spend

• ver 70% of total time

diving in summer season.

HS GS RS RS

Grey seal monitoring

240

• Grey seals gather to islets and skerries in outer archipelago

and coastal zone

• All haulouts are surveyed 2-3 times within a two-week

period in the end of May - beginning of June, new locations searched during the surveys

• The seals are photographed and their numbers

counted from the photos

• The largest daily result for each sea area is used

as abundance index

Grey seal monitoring (example)

Grey seal monitoring (Estonian example, 2017)

1781

2 600 +20.0 % 2 000 +3.9 % 800 +1.0 %

Abundance index in 2017 and average annual increase (%/year) during 2003-2017

~30 000 +4.9 %/year 11 100 +8.0 % 2 100 +9.0 % 8 100 +0.9 % 4 000 +3.8 %

The whole Baltic: ~ 30 000, 60-80 % of the total population size of 37 500–50 000 Geographically describes the situation during the peak moult!

Grey seal abundance trends

> 80 %

2003-2018: 3 500 +20.7 %

Grey seal offshore distribution

Adult male seal (14.7.07+ 242 d ) Adult female seal (14.7.07 + 261 d)

Ringed seal monitoring

• Bothnian Bay:

– Aerial transect line methodology – Transects evenly spread over the ice- covered area – Flying altitude 90 m, survey strips 400 m on both sides – Survey strips give a sample of min 13 % of the ice-covered area – All seals on the survey strips are photographed and counted from the photos – The counted number is then multiplied from the sample to the whole area – The result is used as abundance index

Härkönen & Lunneryd, Ambio 1992

Southern Ringed seals

• The Archipelago Sea, Gulf of Finland and Western Estonia:

– Aerial surveys possible only on good enough ice-years – In the Archipelago Sea the whole area between the transect lines is

• bserved

– Monitoring methods for ice-free circumstances under development

Two management units:

• Bothnian Bay
• The Archipelago Sea, Gulf of Finland and W-

Estonia

> 20 000 ~1 000 ~200-300 ~100

Ringed seal abundance trends

• Annual increase 4.7 % in Bothnian Bay
• No increase in other areas

Ringed seal offshore distribution: migration

Ringed seal offshore distribution: feeding

Ringed seals breeding success and climate change

Up to six weeks of stable ice needed for ringed seals

Grey seal breeding success and climate change

Up to 50% neonatal mortality (5%) Up to 20% less energy reserves

• Baltic seal populations are recovering
• There are some indications of

approaching carrying capacity in grey seal

• Gulf of Finland ringed seal is on the

verge of extinction

• Climate warming is an increasing

challenge for ringed seals

• Improving monitoring methods for

better understanding of seals’ abundance and it’s variations in time and space

Summary of greys and ringed seals