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Catchability of Norway lobster (Nephrops norvegicus) in north Adriatic during seven years period (1995-2002)

Norway lobster (Nephrops norvegicus L.) together with Spiny lobster (Palinurus elephas) and Adriatic lobster (Homarus gammarus) are well known as most abundant and economically best esteemed Decapod in Croatian aquatory. In the Adriatic Sea, during the last decade, the population of the Nephrops norvegicus was endangered by increased fishing efforts and excessive catch of lobsters. Thus, it was necessary to make applied research on lobsters’ fisheries dynamics and gain more knowledge about catchability, population structure and growth-rate of the Norway lobster in the north Adriatic. The field part of research work was carried out in the waters of the Velebit Channel, on the area of approximately 30 nautical miles. All investigations were ccarried out between four orienting points: Cape Družinin (45°08’ N, 14°41’ E) and Selce (45°09’ N, 14°43’ E) at the north side, and Cape Koromačna - Zali rt (44°37’ N, 14°54’ E) and Cape Vrutak (44°39’ N, 14°55’ E) at the south side of the Channel during seven years period (1995 – 2002). Samples were collected every month by trawling, and 11 meters long fishing boat with 115 HP engine was used for sampling. The boat was equipped with bottom-trawl net which front opening was approximately four meters wide. During trawling the boat speed was 2, 3 Nm/h, while each trawl lasted two hours ( 5 min.). After the net had been pulled out total weight and total length (TL)of the caught lobsters was determined, as well as their individual number in catch, sex ratio (females:males), number of females with visible changes on the ovaries, number of females with outside eggs and a number of immature lobster specimens (TL  9.0 cm). Collected data are mathematically analyzed to get estimated values of catchability in the segment of time and area. Further analytics have shown that N. lobster population had higher points of activity during spring and summer. Also, only in the summer months higher number of females was determined. Daily activation of lobster population varied throughout the years depend on season ecliptics, but obtained results showed that fishing at night had the biggest negative impact on N. lobster population.

Norway lobster; catchability; Adriatic

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