This study compared changes in the biochemical composition of muscles and ovaries of maturing female European eels during hormonal stimulation with carp pituitary homogenate under controlled conditions and in the development of oocytes. It has been found that differentiation of oocyte size in eel is visible from the beginning of the gamete maturation process. This differentiation increases as gonads grow. Furthermore, oocytes are at different development stages and are still highly differentiated in terms of size during ovulation. Moreover, the biochemical composition of the body and gonads was found to change. During the process of maturation, the relative fat content in the eel body decreases both in the muscles (from 21.99 ± 4.3 to 18.48 ± 3.3 %) and in gonads (from 25.76 ± 2.71 to 15.21 ± 4.7 %), with the changes in ovaries being more rapid. Protein content in muscles also decreased (from 15.98 ± 3.13 to 12.35 ± 1.6 %) during the process of female maturation. Different trends were observed for polyunsaturated fatty acids (EPA and DHA). The total amount of these acids decreased in muscles (P < 0.05) but increased in ovaries (P > 0.05).

Recreational fisheries are an important element of contemporary fisheries. Detailed information about the motivation and opinions of anglers regarding catch-and-release fishing in post-communist countries, such as Poland, has not been widely available to date. The aim of this study was to fill this gap. We obtained 936 survey questionnaires completed by anglers from throughout Poland. The mean annual catch of a Polish angler is 126 fish weighing 46.1 kg. Anglers catch mainly cyprinids, but they would prefer to catch large predatory fishes, and they spend an average of 416.50 EUR on this activity annually. These results confirm the hypothesis that angling catches in Poland are decidedly of a recreational character and that catches targeted at fish consumption are of lesser importance. Simultaneously, we determined that younger anglers are more willing to release caught fish than older anglers.

The eel is a catadromous fish which spends most of its life in freshwater and adults swim to the Sargasso Sea region to spawn. While preparing for the reproductive process, eels undergo a metamorphosis to become what is called silver eel; a process involving changes in the colour and weight of the body and an increase in the eye size. These are indicators of fish maturity and they facilitate the selection of fish for reproduction under controlled conditions. During this study, changes in the body weight (BW) and eye size in female European eel were observed while being given weekly hormonal injections of 20 mg kg–1 carp pituitary homogenate and kept in 15°C freshwater and in 15°C saltwater with a salinity of 32-33‰. Fish kept in saltwater but not subjected to hormonal stimulation were used as a control group. Furthermore, after the experiment was finished, females in the control group were kept for next 5 months, with the same environmental parameters maintained. Differences between the treated groups were observed as early as week 4 of the experiment. An increase in fish BW was observed in fish kept both in salt and freshwater which were subjected to hormonal stimulation. On the other hand, changes in eye size were observed in the fish kept in saltwater, both in those hormonally stimulated and otherwise. The eye diameter in the fish kept in fresh after hormonal stimulation did not change significantly.

The fish hook is a commonly known tool used in recreational fishing, which is one of the forms of active, specialised tourism. As a component of a fishing rod, the hook is intended to be anchored into the mouth of a fish and hold the fish on the end of the line while landing it. However, in the context of the protection of living aquatic resources and Catch-and-Release (C&R) fishing, its role and significance are becoming broader. In addition to the impact of the hook type on fishing efficiency, including the Catch Per Unit Effort (CPUE), the importance of hook selection in terms of minimising the resulting damage to the tissues of caught and released fish is increasing. It appears that alternative hook types, such as barbless hooks and circle hooks, are safer for fish in the aforementioned context while not significantly reducing fishing efficiency. This review study is aimed at describing the design, types, and role of the fish hook in modern C&R angling, including the impact of the hook type on both fishing efficiency and the safety and welfare of released fish, which translates into the status and protection of living aquatic resources. The issues presented in the study highlight a number of related technical, biological and social factors that are specific to inland angling in particular. Such a holistic perspective can be used to support the effective management of recreational fishing, which, as one of the most popular human activities when in contact with water, has a very significant impact on the state of the environment and, thus, on the possibility of tourism development.