LONG-TERM EFFECTS OF EPIZOOTIC IN HARBOR SEALS IN THE KATTEGAT-SKAGERRAK AND ADJACENT AREAS

• Results from aerial surveys of hauled-out harbor seals, Phoca vitulina, in the entire Kattegat-Skagerrak, the Limfjord and the western part of the Baltic Sea in 1989-1991 are compared with results from surveys conducted soon after the seal epizootic in 1988. The results suggest that an increase in relative abundance of seals occurred between 1988 and 1991 in the Limfjord and in most parts of the Kattegat-Skagerrak. Pup production was assessed at selected localities in the Kattegat-Skagerrak during 1978-1991. Lowered rate of pup production occurred in 1989, the year after the epizootic. However, the pup production resembled expected values in 1990-1991. The decline in 1989 was probably due either to perturbations of the reproductive cycle caused by the morbilli virus infections in 1988, or to the shortage of mature males in some areas in the 1988 mating season. The lowered pup production was also evident in the aerial surveys where no increase in relative abundance was detected during 1988-1990. Simulations based on a matrix model of the Kattegat-Skagerrak population suggest that skewed sex and age distributions will persist for decades, but a high rate of increase should enable the population to recover by 1995-1996 to a size similar to that before the epizootic.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

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