Scholarly record
BIOMETRIC MEASUREMENTS AND DEMOGRAPHIC STRUCTURE OF DUCKS HUNTED ON LAKE ENGURE IN THE PERIOD 1993-2022
Abstract
The research aims to identify changes in the biometric measurements and demographic structure of game ducks living on Lake Engure. Game management in Latvia as well as the entire Northern Europe is an important segment of the economy, which has rich and ancient traditions. Although a small segment of society perceives game management as the killing of animals, which is not the case, it should be understood that it represents an economic activity resulting in limiting the animal population, which can increase rapidly because of anthropogenic factors. Therefore, the functioning of an ecosystem modified by humans is unthinkable today without hunting. Waterfowl hunting is a kind of hunting that is important to hunters, and the hunters are often those who also create artificial nesting sites to increase the population of ducks, thereby increasing the success of nesting in their hunting grounds. Ducks have many natural enemies, as well as there are other abiotic and anthropogenic factors that can sometimes significantly affect the local population of ducks. The research was conducted in Latvia, on Lake Engure, which is one of the richest lakes in ducks and where research on waterfowl has been conducted for several decades. Censuses of nesting waterfowl on the islands of Lake Engure and on grass and reed swamps as well as other censuses are taken every year. The research analysed hunted waterfowl by taking biometric measurements, identifying their wing length and weight and collecting demographic data on their sex and age. The changes were analysed by the regression analysis method; an independent parameter was the number of days from the beginning of the year, while dependent parameters were wing length and body weight, which were calculated for each hunted waterfowl species during the year/season. To identify the overall health condition of hunted waterfowl, the body mass index was calculated for each species. The research found that the number of hunted ducks on Lake Engure significantly decreased in the period 1993-2022 (r=0.54; p=0.002). The number of days from the beginning of the year to the beginning of the waterfowl hunting season did not significantly affect the wing length of ducks living on Lake Engure. For ducks nesting in Latvia on Lake Engure: northern shovelers (r=0.23; p=0.51), Eurasian teals (r=0.24; p=0.46), mallards (r=0.23; p=0.46), garganeys (r=0.28; p=0.47), gadwalls (r=0.19; p=0.57) and common pochards (r=0.46; p=0.18), the body mass index has not significantly changed in the period 1993-2022.
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