Trophy structure of common carp, pike, wels catfish and pike-perch in Drava – Danube fishing zone

The general heterogeneous angler population in Croatia is slowly dispersing in more homogeneous subgroups, specialized in certain fishing techniques or focused on fishing favorite fish species. These subgroups prefer specimen-sized fish rather than the catch of many smaller fish, peculiarly during catch-and- release fishing. The new desires of the anglers gradually influence the changes in the management of fishing waters, resulting in the preservation of bigger specimens of fish with trophy value. The purpose of this paper is to analyze the caught specimens of common carp (Cyprinus carpio), pike (Esox lucius), wels catfish (Silurus glanis) and pike-perch (Sander lucioperca) in fishing waters of DravaDanube fishing zone in the period 2011-2017, and to evaluate the trophy structure of mentioned fish. The fish sampling was carried out using a combinations of fishing gear (commercial fishing nets, survey nets) and an electrofishing. Proportional Stock Density (PSD) is a measure of species size (trophy) structure. The metric is a ratio (expressed as percentage) between the number of quality-sized individuals or larger individuals and stocksized individuals. During the monitoring period 1.044 specimens of common carp was caught, followed by 220 specimens of wels catfish, 142 specimens of pike and 118 specimens of pike-perch. Proportional stock density for common carp was 78%, meaning that 78% of caught specimens were above minimal size for stock length (20–26% of the world-record length). PSD values were 30% for pike, 36% for wels catfish and 69% for pikeperch. These results indicate a favorable fish trophy structure in fishing waters of the DravaDanube fishing zone for specialized anglers, which is a result of good management of fishing waters, effort of warden service and the rise of awareness on fishing culture. Relative stock density (RSD) was also calculated for memorable (59-64% of and the world-record length) and trophy (74-80% the world-record length) category. RSD value for common carp was 4%, 6% for pike, 1% for wels catfish and unexpectedly high 18% for pike-perch. This was a preliminary research of trophy structure for the complete Drava-Danube fishing zone, so further research will be focused on individual fishing water in order to eliminate size difference between fishing waters