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Harbor porpoise (Phocoena phocoena) in Norwegian waters

Bjørge, Arne; Aarefjord, Hilde; Kaarstad, Sølvi; Kleivane, Lars; Øien, Nils
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CM_1991_N_16.pdf (3.780Mb)
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http://hdl.handle.net/11250/104940
Issue date
1991
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  • ICES CM documents authored by IMR scientists (1949-2011) [3135]
Original version
This report is not to be cited without prior reference to the authors  
Abstract
Recordings made on the Norwegian Sighting Survey 1988 and the North Atlantic Sighting Survey

1988 (NASS-89) indicate a divided off shore distribution during summer for harbour porpoises in

Norwegian waters, with a southern component in the North Sea area and a northern component from

Lofoten and into the Barents Sea. Incidental sightings during the period 1964 - 1988, and distribution

of by-catches in the drift net salmon fishery 1988, support these findings.

Estimates of pod size and abundance of harbour porpoise in the North and Barents Seas are given. The

abundance estimates were about 82 600 porpoises (c.v. 0.24) for the southern component (the North

Sea area) and about 11000 porpoises (c.v. 0.44) for the northern component (Lofoten- Barents Sea).

These estimates were based on NASS-89.

Incidentally caught porpoises were used to establish growth curves, age at sexual maturity, and to study

the composition of prey species in the stomach content as well as contamination of organochlorines in

the blubber. The testicular weight increment was used as an indicator of sexual maturition in males,

and the age of first time ovulation was used as age of sexual maturity in females. Using the von

Bertalanffy growth model, asymtotic values for body length were 142.3 cm for males and 155.9 cm for

females, and asymtotic values for body weight of males and females were 52.7 kg and 49.4 kg,

respectively. In a total of23 females, 18 were three years old or younger, and these were all immature.

Two out of three were sexually mature at the age of four years, and from the fifth year and onwards all

were mature. Although the sample size is too small to be conclusive, these preliminary results indicate

that sexual maturity is attained from age three in males, and about one year later in females.

Stomachs from 176 porpoises from Kattegat, the northern North Sea and the Barents Sea were

examined. A minimum number of 2979 specimen of fish from 27 different species were identified based

on otoliths recorded in the stomach contents. Remains of hagfish, squids and polychaetes were recorded

in a few stomachs. Geographical variation of species distribution in the stomach content was noted,

reflecting geographical variation in availability of prey species.

Contamination levels of 16 different organochlorines in blubber of male porpoises from Kattegat were

compared with porpoises from the northern North Sea and the Barents Sea. Geographical differences in

concentrations were recorded for eight of the compounds.
Publisher
ICES
Series
ICES CM Documents;1991/N:16

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