Patterns of river lamprey size and sex ratio in the Baltic Sea basin [RESEARCH ARTICLE]

Abstract

A comparative study of the size distribution of river lamprey, Lampetra fluviatilis (L.), was conducted in several rivers in the Baltic Sea basin. Total length and weight data were collected from 7503 lamprey individuals. Sex ratio distributions were also examined in some of the river lamprey populations. The length of lamprey varied from 20.0 to 51.0 cm. The smallest lamprey were in Finland, where mean length in different rivers ranged from 27.9 to 30.8 cm. Larger individuals were noted in Latvia, with mean lengths from 34.0 to 39.5 cm, and in Lithuania from 33.5 to 36.4 cm. The largest lamprey were in Poland, where mean length was from 38.3 to 42.9 cm. The heaviest lamprey were noted in Poland with mean body weights from 45 to 230 g, while slighter individuals were noted in Finland with mean body weights from 12 to 90 g. The body length and weight ranges indicate regional variation. The smallest lamprey individuals were noted in the populations in the rivers of the northern region of the Baltic Sea basin. The analysis of the sex ratio distribution indicated that in most rivers populations of river lamprey males slightly outnumbered females.

CORRESPONDING AUTHOR:

R. Bartel [+], R. Bernaś
Department of Migratory Fish
The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn
Synów Pułku 37, 80-298 Gdańsk, Poland
Tel./Fax.: 58 5507715; e-mail: gdansk@infish.com.pl
B. Bradauskas
Department of Environmental Protection
Republic of Lithuania, Vilnius, Lithuania
E. Ikonen
Finnish Game and Fisheries Research Institute, Helsinki, Finland
A. Mitans
Department of Fisheries Research, Institute of Food Safety
Animal Health and Environment (BIOR), Riga, Latvia
W. Borowski
Sea Fisheries Institute, Gdynia, Poland
A. Garbacik-Wesołowska
Sea Fisheries Institute, Świnoujście, Poland
A. Witkowski
Museum of Natural History, Wrocław University, Poland
J. Błachuta
Museum of Natural History, Wrocław University, Poland
Present address: Department of Ecology
Institute of Meteorology and Water Management, Wrocław, Poland
J. Morzuch, A. Kapusta
Department of Ichthyology,
The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland