Growth rate and condition of vimba, Vimba vimba (Actinopterygii: Cypriniformes: Cyprinidae), a species under restitution in the Odra River estuary

Abstract

Background. The majority of European populations of vimba, Vimba vimba (L.), have been classified into increasing categories of conservation status while Polish populations of this fish are classified as CR (critically endangered) and in fact they are facing extinction. In many rivers in Poland, including the Odra River, restitution efforts of vimba have been undertaken. Monitoring some biological parameters of the population such as the rate of growth (increase in mass and length), age structure, sex structure, and condition nay help to evaluate the success rate of the restitution efforts. Materials and methods. In total, 210 individuals of vimba, caught in the waters of the southern part of the Odra River estuary, mainly in Lake DÄ…bie, between 28 May 2007 and 30 June 2008 were studied as to their age, condition, rate of growth in mass and length. Making use of the linear R–L dependence, the back calculations were made according to the Rosa Lee procedure with a standard of 20 mm. Results were approximated by 5 mathematical models of growth proposed by von Bertalanffy, Ford–Walford, Gompertz, and based on second degree polynomial function and modified power function. Increase in mass was described by a modified von Bertalanffy equation. The condition of the fish was described by the Fulton (K) and Le Cren (Lc) formulae. Results. Females dominated in the material studied, they constituted over 61% of all individuals. In the age structure groups, females were most often found in groups: 10+ (13.33%), 9+, and 11+ (12.86% each). Males were found in the greatest number among 5-, 6-, and 7-year-old fish (4+, 5+, and 6+, respectively). The mean standard length and mass of the vimba fish studied were 306.33 mm and 286.02 g, respectively. The annual increase in length of the fish approximated 20 mm, being the most intense in the first two years of life (23–24 mm). Fulton and Le Cren coefficients of condition were 0.93 and 1.64 and the ranges of these values were 0.69–1.47 and 1.15–2.60, respectively. Conclusion. Analysis of back readings and empirical results proved that the growth of vimba was best approximated by the von Bertalanffy model. Comparative analysis of condition coefficients of the population of vimba in the Odra River estuary and other populations showed that the condition of analysed vimba population in individual years of live was lower.

Keywords

• Odra River
• Oder River
• vimba
• restitution
• growth