Selektivnost ishrane potočne pastrmke Salmo cf. trutta (L.) kao činilac ribolovnog uspeha

Abstract

Potočna pastrmka je u rekreativnom ribolovu cenjena riblja vrsta, otuda i neposustajuće interesovanje za ponašanje ove vrste sa aspekta njene ishrane. Vizuelni je predator, hrani se vodenim i kopnenim beskičmenjacima i sitnijim ribama, a većina autora smatra je generalistom i oportunistom. Ciljevi studije bili su ispitati sezonsku dinamiku ishrane potočne pastrmke na tri pastrmska vodotoka različitih karakteristika, razlike u rastu i produkciji pastrmke i njihovu korelaciju sa karakteristikama staništa, kao i značajnost i selektivnost različitih vrsta plena u ishrani pastrmke, gde je selektivnost tokom sezone izražena Electivity indeksom, kako bi se dala preporuka za uspešan pristup ribolovu na ovu vrstu na različitim tipovima staništa. Karakteristike staništa važne za izbor načina ribolova su geologija područja, abundanca i diverzitet plena, bogatstvo drifta i doba godine. Visoka provodljivost vode ima pozitivan uticaj na produkciju plena, a samim tim i produkciju pastrmke. Najzastupljeniji plen na staništu obično je negativno selekcionisan, osim na početku i/ili na kraju sezone kada je drugi plen manje dostupan. Za redak plen postoji pozitivna selekcija pa bi imitacije takvog plena mogle biti uspešnije. Imitacije bentosnog plena treba birati u skladu sa abundancom i sezonskom dinamikom, a različite imitacije terestričnog plena koristiti pred kraj sezone jer je tada izrazito pozitivno selekcionisan. Pastrmka brzo reaguje na promene u dostupnosti plena, ali je moguće predvideti koja će imitacija biti uspešna na osnovu karakteristika staništa i sezonske dinamike. Na staništima sa manjom abundancom ali visokim diverzitetom plena moguć je uspešan ribolov sa raznovrsnim imitacijama, dok će selektivnost biti izraženija na plenom bogatim staništima.

Brown trout is a valuable species in recreational fishing, hence the persistant interest in its feeding behavior. It is a visual predator, that feeds on aquatic and terrestrial invertebrates and smaller fish. Many authors considered it both a generalist and opportunist. The aims of the study were to determine seasonal dynamics of brown trout diet on three salmonid watercourses with different characteristics, difference in trout growth and production and to examine their correlation to habitat characteristics, significance and selectivity of different prey, where the selectivity was assessed by Electivity index, so that successful fly fishing approach could be proposed for different habitats. The habitat characteristics important for choosing fishing approach are geology of the area, prey abundance and diversity, drift richness and time of the season. High water conductivity has a positive impact on prey production, and consequently high trout production. The most abundant prey in the habitat is usually negatively selected, except at the beginning and/or the end of the season when other preys are less available. Positive selection exists for rare preys so imitations of such prey can be more successful. Imitations of benthic prey should be chosen with respect to its abundance and seasonal dynamics, and various imitations of terrestrial prey should be used more near the end of the season when it is positively selected. Trout react quickly to changes in prey availability, but which imitation will be successful can be predicted based on habitat characteristics and seasonal dynamics. Successful fishing with various imitations is possible in habitats with lower abundance but high diversity of prey, while selectivity will be more pronounced in prey-abundant habitats.