Novi dizajn istraživačkih mreža stajačicama za uzorkovanje riba u Jadranskom moru

Three types of multi-mesh benthic survey gillnets were tested for their performance in the uniform muddy bottom habitat of the Bay of Piran. We describe the compared methods, present their positive and negative aspects and suggest a sampling design that could be used with different research goals. The research sampling was performed in winter in the years from 2010 to 2012. The sampling site is situated close to a sea bass rearing fish farm in the Northern Adriatic Sea. With the Nordic 1.5 type nets 5 species were detected compared to the 23 and 20 species detected with the Adriatic 2.5 and 5.0 nets. In the Nordic 1.5 type nets only demersal species were caught and even for those a much greater sampling effort would be required to reach a representative sample. On the other hand, both the Adriatic type nets also caught benthopelagic and pelagic species, and a correlation between net height and size of fish in these two nets was detected. While both the Adriatic type nets proved successful in achieving a representative sample of fish assemblage, the Adriatic 2.5 nets performed better in terms of CPUE and as such also reached a better cost-benefit ratio.Tri vrste jednostrukih mreža stajačica različitih veličina oka su testirane na uniformnom muljevitom dnu Piranskog zaljeva. U radu su opisane i uspoređene metode, predstavljeni njihovi pozitivni i negativni aspekti te predložen plan uzorkovanja koji bi se mogao koristiti za različite istraživačke ciljeve. Istraživačko uzorkovanje se odvijalo zimi u razdoblju od 2010. do 2012. godine, a uzorkovalo se u neposrednoj blizini uzgajališta lubina u sjevernom dijelu Jadranskog mora. U Nordijskom 1.5 tipu mreža nađeno je 5 vrsta organizama, u odnosu na 23 u Jadranskom 2.5, te 20 vrsta nađenih u Jadranskom 5.0 tipu mreže. Nadalje, u Nordijskom 1.5 tipu mreže su uhvaćene samo pridnene vrste organizama, s tim da je do reprezentativnog uzorka bilo puno teže doći. S druge strane, u oba Jadranska tipa mreža su nađene bentopelagične i pelagične vrste riba, te je utvrđena korelacija između visine mreže i veličine riba. Premda se s obje vrste mreža Jadranskog tipa relativno lako došlo do reprezentativnog uzorka, Jadranska 2.5 mreža je dala bolje rezultate s obzirom na CPUE te tako postigla bolji omjer uloženog i dobivenog

The European Tracking Network COST action

The Pan-European Aquatic Animal Tracking Network is a data management and partnership platform that aims to connect and share data across Europe. It presents a forum where researchers and laboratories can shape partnerships, develop and align their research, share ideas and experiences. Fish are the most researched group of organisms, as they travel far and wide and sharing of data about their movement across countries is essential. Moreover, development of coordinated, Pan-European conservation measures is the key for their conservation. The backbone of the ETN is therefore a central database in which telemetry (meta)data can be stored and shared. The ETN COST action was launched to connect more European telemetry scientists and offer opportunities for networking and cooperation. We will focus on presenting the benefits and opportunities that telemetry as a research tool can offer, especially in the scope of the European Tracking Network COST action

Comparing dominance relationships and movement of native marble trout (Salmo marmoratus) and introduced rainbow trout (Oncorhynchus mykiss)

Behaviour observations of the endangered native marble trout (Salmo marmoratus,Cuvier, 1829) and introduced rainbow trout (Oncorhynchus mykiss, Walbaum, 1792)in the laboratory and in a tributary to the Idrijca River in Slovenia were combined tostudy the movements and dominance relationships between individuals of the twospecies in an open field test. Under laboratory conditions, no difference between thespecies was detected for neither time spent actively or distance moved. In speciespaired tests, rainbow trout initiated more aggressive behaviours towards marble troutthanvice versa, and rainbow trout were clearly the dominant individuals. After simul-taneous release in the river, marble trout immediately left the release area and spenttwice as long time as rainbow trout until they settled in an area of the river; there-fore, the release site was immediately occupied exclusively by rainbow trout. Thus,the dominant and aggressive behaviour of rainbow trout seen in the laboratorybefore release might have influenced marble trout's subsequent behaviour in theriver, by marble trout leaving the areas occupied by rainbow trout and moving tolocations further away from the release site. In the field, the marble trout occupiedsites individually, whereas rainbow aggregated at a few locations. Rainbow troutshowed higher movement activity in the morning compared to marble trout. Therewas a positive correlation between swimming speed in the laboratory and movementin the field for marble trout but not for rainbow trout. In conclusion, the results in thisstudy support the need to end stocking of rainbow trout in rivers with native marbletrout. To better understand the interaction between the species, and to develop effi-cient management plans to protect the native marble trout, reference behavioursshould first be understood, and future research in sites where the two species do not co-exist is needed. This is especially important for marble trout for which behaviouralresearch and data are lacking.acceptedVersio

Interdisciplinary design of a fish ramp using migration routes analysis

The study presents several steps of a fish ramp geometry optimization performed with a 3D numerical model DualSPHysics, which is based on the smoothed particle hydrodynamics (SPH) method. The optimization process led to the design of a bottom ramp that is capable of providing suitable conditions for the migration of target fish species (Salmo truta, Phoxinus phoxinus, Cottus gobio, and Eudontomyzon vladykovi). Migration routes were determined as complex 3D volumes of fluid according to the simulated velocity field in various steady flow conditions. Including three categories of potential migration zones (rest, effort, and limit zones), migration routes were quantified in high detail in terms of the size and position of each zone, and in terms of the distance from a given fluid part to the nearest rest zone. The interdisciplinary approach of this study also led to the development of new tools for the DualSPHysics model, specifically suited to improve functionality in eco-hydraulics research. Fishway Ramp River restoration Smoothed particle hydrodynamics DualSPHysicspublishedVersio

Past and Future of Sturgeon Species (Acipenseridae) in Western Balkans: Case for Permanent Conservation or Sustainable Management

Sturgeon species in Western Balkans are mainly occupying the Danube River basin, which represents one of the centers for sturgeon diversity. Although there are numerous negative anthropogenic impacts (habitat fragmentation, pollu- tion, fishery pressure) on sturgeons, constructions of hydropower dams in the Iron Gate area severely decreased their natural spawning habitats and only sterlets have a viable population upstream from Iron Gate 2 dam. Review of the status and population trends based on available statistics, pollution impact, composition and change in their diet, the impact of invasive species, as well as restocking and ex situ conservation programs will be presented. Assessment of legislation and sturgeon protection projects and their impact on wild sturgeon populations will be discussed

Political and Socio-Economic Aspects of Fisheries in Inland and Coastal Waters of the Western Balkan

In the last decades in Europe, especially in the Balkan region, modernization of agriculture gave priority to economic growth without consideration of the environmental impact and sustainable development. Fisheries have traditional and essential importance of food and income in the Slovenia, Croatia, Serbia, Bosnia and Herzegovina, Montenegro, North Macedonia, and Albania (Western Balkans). The fisheries sector in Western Balkans is still not organized according to requirements of ecosystem integrity and sustainable utility. Practical application of the legislation indicates that the fishery has been developed without adequate harmonization with socio-economic characteristics, enforcement resources, and adequate control measures. Policymakers continue to be reluctant to give importance to the fishery sector, when allocating fishery resources among multifunctional users of water resources. In the following text, we gave review of the fisheries policy and socio-economic aspects of fishery sector in the Western Balkan countries. Critical fisheries policy and management measures are discussed and the propositions and recommendations of environmental sustainability measures under modern anthropogenic pressures are presented

Tracking aquatic animals for fisheries management in European waters

Acoustic telemetry (AT) has emerged as a valuable tool for monitoring aquatic animals in both European inland and marine waters over the past two decades. The European Tracking Network (ETN) initiative has played a pivotal role in promoting collaboration among AT researchers in Europe and has led to a significant increase in the number of tagged and observed aquatic animals in transboundary European waters. While AT benefits decision-making and delivers essential data to management bodies, its potential for management decision-making mechanisms has yet to be fully harnessed. We reviewed existing research, studies, and organisational initiatives related to aquatic animal tracking and their utility in fisheries management in European waters. We found that AT has already contributed to many aspects of fisheries management, such as improved understanding of stock dynamics, identification of critical habitats, assessment of migration routes, and evaluation of the effectiveness of conservation measures. However, broader utilisation of tracking technologies is needed. By leveraging the full potential of AT, managers can make more informed decisions to protect, restore, and sustainably manage European waters and creatures that live therein