Özet:

Comparative assessments of mean growth rates in length across fish populations are useful for gaining insights into the conservation, management and control of species, especially at larger scales of distribution. The purpose of this study was to refine the Growth Index (GI), a useful measure for comparing species-specific growth rates in fish. Using literature-based length-at-age data for 299 populations of roach Rutilus rutilus, a widespread freshwater fish of Eurasian distribution, the GI was calibrated and the previously semi-quantitatively defined ‘slow’, ‘average’ and ‘fast’ growth categories were quantitatively re-defined. A threshold value of 114% GI separated ‘slow’ from ‘average’ growth populations and of 155% GI ‘average’ from ‘fast’ growth populations. Slow growth rates were identified along the entire latitudinal range of the species’ distribution, whereas below ≈37ºN all types of growth were encountered, indicating the importance of waterbody-related environmental factors in affecting growth in roach. Given the relatively widespread usage of the GI, species-specific calibrations leading to improved definition of corresponding growth bands are recommended for other widespread fish species of both economic value and ecological concern.

Anahtar Kelimeler: