Cormorant predation mortality of perch (Perca fluviatilis) in coastal and archipelago areas, northern Baltic Sea
Abstract Perch (Perca fluviatilis) is an important prey species of the great cormorant (Phalacrocorax carbo sinensis) in the coastal waters of the northern Baltic Sea. The annual predation mortality caused by cormorants was estimated based on the consumed numbers of perch in relation to the abundance of perch in vulnerable age groups in the sea. We used existing stock assessment data (Archipelago Sea) or a simple population model in other areas (Gulf of Finland, Bothnian Sea, and Quark), based on commercial and recreational perch catches, and estimated fishing and natural mortalities, with distributions describing our understanding about the likelihood of different values for every variable…
Kalavarojen kestävä käyttö : suunnittelu ja toteutus
Cormorant (Phalacrocorax carbo) predation on a coastal perch (Perca fluviatilis) population: estimated effects based on PIT tag mark-recapture experiment
Abstract The number of cormorants has rapidly increased in the northernmost Baltic Sea. In 2018, 50 km × 50 km ICES catch rectangle 55H1 had 3140 breeding pairs. To estimate the predation effect of cormorants on perch populations, we Passive Integrated Tags tagged 1977 perch and 9.9% of tags were found. The median instantaneous cormorant-induced mortality during the breeding time, with consumption by non-breeding individuals, was estimated at 0.23 and at 0.35 during the whole residing period. We estimated with a yeild-per-recruit model that the long-term maximum loss of perch yield of tagged sub-population would be at 80% probability interval 32–67%, and when extended to the entire 55H1, 10…
Tutkimus ja seuranta
Kalavarojen käyttö ja hoito pysyvät kestävällä pohjalla, kun päätökset perustetaan mahdollisimman luotettavaan ja ajantasaiseen tietoon. Tietoa tarvitaan toiminnan kaikissa vaiheissa, mutta erityisesti silloin, kun asetetaan tavoitetilaa ja osatavoitteita sekä myöhemmin, kun on aika arvioida toimenpiteiden tuloksellisuutta. Tässä luvussa esitellään alueelliseen käyttöön soveltuvia tiedonhankintamenetelmiä sekä annetaan ohjeita aineistojen keruuseen ja tulosten tulkintaan. nonPeerReviewed