LENGTH-WEIGHT RELATIONSHIPS FOR COMMON FRESHWATER FISH SPECIES IN IRISH LAKES AND RIVERS

The objective of this study was to provide fisheries researchers with a cost-effective solution to estimate the weight of a particular fish species from the hypothesis that length and weight are strongly correlated. The aim was to estimate the weight from a given length through a length weight relationship/regression equation. Length-weight (L-W) regression equations were derived for ten of the most common fish species and two cyprinid hybrids encountered in Irish lakes and rivers (brown trout, salmon, roach, perch, eel, Arctic char, bream, pike, rudd, tench, roach x bream hybrids and roach x rudd hybrids) from an extensive dataset of approximately 228,000 individual fish over a tenyear period between 2005 and 2014. The data was collected during routine Inland Fisheries Ireland monitoring programmes from lakes and rivers across Ireland. The dataset of the three most abundant species on lakes and rivers was categorised into three alkalinity groups for further accuracy. Significant relationships were found between length and weight for all ten fish species and two cyprinid hybrids in all water body types, showing that length is a significant predictor of weight and the findings are reflective of other studies, making this a strong tool for estimating weight.