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The invasion history and the recent distribution, abundance and prey composition of pikeperch, Sander lucioperca in Neretva River watershed (Bosnia and Herzegovina and Croatia) are presented. The species was illegally/unintentionally introduced in Ramski Reservoir in the upper river part in 1986, while establishment of its abundant populations was reported during the 1990s in two connected artificial reservoirs. The research on the present abundance and food composition was executed during the 2012–2014 period. The results showed that pikeperch occupied most of the water bodies of the Neretva River, with an exception of natural river parts with gravel sediment and fast flow: all five artificial reservoirs (Ramski, Jablanički, Grabovica, Salakovac and Mostarski reservoirs) and lower wetland zone. However, the success and impact of colonization differ among water bodies, indicating pikeperch preference for warm and shallow reservoirs. Pikeperch prey is composed of different fish species abundant in specific water bodies. In artificial reservoirs, it preys mostly on introduced fish species, with a potential for controlling pumpkinseed abundance and biomass. Sampling carried out in Ramski Reservoir between 2013 and 1014 showed exclusive feeding on the introduced Leucaspius delineatus, and the establishment of a new food web, where only introduced species play significant roles.

Over the past decade, the waters of the Croatian Adriatic Sea have been marked by significant changes in the characteristics of the marine ecosystem. Although a link between these changes and the common explanation of climate change has not been scientifically proven, the effects of the changes are already clearly evident. This includes the effects on the fisheries and mariculture sectors through the invasion of new fish species, better performance of native warm-water species and significant pressure on cold-water species. As some of the recent effects have clear economic consequences for the fisheries, this paper provides an overview of the impact of climate change as well as predictions for future management strategies for the Croatian fisheries and mariculture sectors.

Traditionally, biological resources in the sea have been distingusihed a spelagic, demersal (trawling) and near-shore even though there is no clear distinction between them in nature. Near-shore biological resources are exploited by small-scale or coastal fishing which makes use of all 55 kinds of fishing gear known along the eastern Adriatic, apart from tuna seine, bottom trawl and pelagic trawl. The near-shore belt along the eastern Adriatic coast and around the islands extends on the average 300 m offshore (50-2000 m) with a maximum depth of 80 m. This area constitutes up to 6% of the Croatian Adriatic total fishing grounds or up to 14% of the inner Croatian fishing grounds. This is an area of highest organic matter production. As to the catches realized all along the eastern Adriatic coast the near-shore fishing has recently been yielding more than pelagic and trawl fishing. According to an arbitrary estimate, in 1994 pelagic fishing yielded 9.4 thousand tons, trawl fishing 9-11 thousand tons and near-shore fishing about 30 thousand tons. In 2003 pelagic fishing yielded 19.6 thousand tons, trawl fishing about 8 thousand tons and near-shore fishing only about 7 thousand tons. The coastal catch was of higher quality. Analyses of catches of trammel sets "test gear" used for monitoring of the state and changes in coastal populations of commercially important organisms of the eastern Adriatic-have shown that these resources have been seriously overexploited by intensive fishing. Decrease of quantity and quality of trammel net catches have been observed along the eastern Adriatic coast for 35 years. In addition, some changes in the number and quantity of some fishes, cephalopoda and crustaceans in the catches have also been recorded, a s well as the reduction in the size and weight of some species. These changes have been recorded in all of the eastern Adriatic near-shore area, particularly those locations closer to the coast in contrast to some of the offshore islands (Palagruža, Sveti Andrija, Brusnik, Lastovo). Future near-shore fishing should be based on an appropriate national strategy of development of Croatian fisheries and related activities, in compilance with the Law on Marine Fisheries of the Republic of Croatia. As to the near-shore fisherey, priority should be given to the renewal of exhausted resources. Only then rational exploitation can restart. Rational management requires knowledge of teh qualitative and quantitative catch structures, the areas fished and fishing activity. However, such data are not yet available for the eastern Adriatic.

The feeding habits of sand smelt, Atherina boyeri Risso, 1810 in the mouth of the Mala Neretva River were studied by examining the stomach contents of 1236 fishes collected from March 2001 to February 2002. Thirteen different food categories were identified. The greatest diversity was recorded in winter, especially in January, when 11 categories were present. The minimum (4) was in September, and was associated with the highest number of empty stomachs. Marine and estuarine species represented the bulk of the prey, while typically fresh-water species (Daphnia spp. and Cyclops spp.) were found only sporadically. Crustaceans were the most common prey and, of these, the most common were copepods (45%), followed by gammarid amphipods (34%), cladocerans (13%), decapod larvae (12%) and mysids (8%). Insects represented 7%. The percentage number of prey showed high seasonal variations. Copepods dominated in autumn and winter, cyclopoids in April, poecilostomatoids and harpacticoids in December, and calanoids in January and February. Decapod larvae dominated in March-May, and mysids in July-August. PCA and clustering analysis was performed on the prey data in order to reveal associations between prey items or seasonal similarities. The opportunistic mode of feeding of the species Atherina boyeri is also discussed., Los hábitos alimenticios del pejerrey, Atherina boyeri Risso, 1810 en la boca del río Mala Neretva se estudiaron mediante el examen del contenido estomacal de 1236 peces recolectados desde marzo de 2001 a febrero de 2002. Se identificaron 13 categorías diferentes de alimento. La mayor diversidad se observó en invierno, especialmente en enero, en que estuvieron presentes 11 categorías.. El mínimo (4) se observó en septiembre, y se asoció al mayor número de estómagos vacíos. Las especies marinas y estuáricas representaron el principal grupo de presas, mientras que especies típicas de agua dulce (Daphnia spp. y Cyclops spp.) se encontraron sólo esporádicamente. Los crustáceos fueron las presas más comunes, siendo los copépodos los más frecuentes (45%), seguido de los amfípodos gammaridos (34%), cladóceros (13%), larvas de decápodos 12%, misidáceos 8%, e insectos 7%. El porcentaje de presas mostró una alta variación estacional. En general, los copépodos dominaron en otoño e invierno: los Cyclopoides fueron más numerosos en abril, los poecilostomátidos y harpacticoides en diciembre y los calanoides en enero y febrero. Las larvas de decápodo dominaron en marzo-mayo y los misidáceos en julio-agosto. Con los datos de presas se realizaron análisis multivariantes para revelar asociaciones entre presas o similaridades estacionales. En este trabajo se discute, también, el modelo de alimentación de tipo oportunista de la especie Atherina boyeri.

The Atlantic Blue Crab Callinectes sapidus has been recognized as invasive in the Mediterranean Sea, where it now provides a significant contribution to artisanal fisheries. In this study, we compared the efficiency, selectivity, and productivity of American wire crab traps and traditional fyke nets for the capture of Blue Crabs in a study conducted from June to December 2019 in the Parila Lagoon (River Neretva Estuary, Croatia). A total of 7707 specimens were caught in 15 wire traps, comprising 6959 males and 749 females. The total catch using 50 traditional fyke traps was 1451 crabs, of which 1211 were males and 240 were females. In general, wire crab traps showed a higher capture selectivity and economic performance compared to fyke nets. The catch per unit effort (CPUE) was 102.76 kg for the American wire crab trap and 5.96 kg for the traditional fyke net. The CPUE of gravid female Blue Crabs was lower for the wire traps than the fyke nets. Herein, the utility of crab traps as selective fishing gear for the capture of Blue Crabs, and management tools for control of the reproductive and recruitment phases of the crab, are discussed, with the perspective of future exploitation of the species as a commercially valuable shellfish product in the Mediterranean.