Alongside climate change, the introduction of non-native species (NNS) is widely recognized as one of the main threats to aquatic biodiversity and human wellbeing. Non-native species and biodiversity are generally low priority issues on the political agendas of many countries, particularly in European countries outside the European Union (EU). The objectives and tasks of this study were to address the policy regulation, education level, education practices, and socioeconomic perceptions of NNS in the Balkans. A questionnairebased survey was conducted in Albania, Bosnia and Herzegovina, Montenegro, North Macedonia and Turkey (Balkan EU candidate and potential candidate members), in Croatia and Greece (Balkan EU Member States) and Italy (non-Balkan EU Member State). The EU Alien Regulation (1143/2014) concerning NNS is implemented in EU Member States and Montenegro, whereas Albania, Bosnia and Herzegovina and Turkey have not reported specific policy regulations for NNS. Permanent monitoring programmes specifically designed for NNS have not yet been established in the EU Member States. Most countries tackle the issue of NNS through educational activities as part of specific projects. Education level is indicative of the implementation of NNS policy regulation, and efforts are needed for the proper development of relative study programmes. Public awareness and educational preparedness concerning NNS in the Balkans were identified as poor. Strong programmes for management and education should be developed to increase public awareness to prevent further biodiversity losses in the Balkan region.
No spirlin have been registered in the barbel zone of the Sava River, Croatia in the late seventies of the last century. Since then, due to improved water quality the presence of spirlin gradually increased in number (23.3%) and in biomass (4.7%). The most dominant item in the diet of spirlin were Bacillariophyceae and Chlorophyceae during every monthly investigation. The diet consisted also of invertebrates which can be considered as a secondary or an accidental prey. The size related analyse of the consumed food showed Bacillariophyceae to be preferred food by fish of all sizes. The back calculated growth in the total length could be expressed by the following formula: Lt = 12.0 (1-e -0.59 (t+0.14)). The phi-prime of spirlin from the Sava river is φ’=4.44. The length-weight relationship, covering the fish from the entire growing period, showed an isometric growth with a b-value of 3.025 (p›0.05), except of September when it was significantly allometric. That was confirmed by the non-significant relationship between condition factor and total length (r = 0.014; p > 0.05). However, CF in June, September and October (0.86 ± 0.07; 0.85 ± 0.09 and 0.87 ± 0.10, respectively) was significantly lower (p<0.05) than in May and July (1.00±0.21 and 1.00±0.12, respectively). The improved water quality during the last fifteen years enabled spirlin to migrate and enlarge its population downstream, resulting in a slightly decreased condition factor.
The Neretva chub, Squalius svallize is an endemic species of the Adriatic basin of the southeastern Europe. Altogether, 60 specimens were caught by gill nets from the Neretva river area, the oldest being seven years old. The most dominant item in the diet of S. svallize during winter season were larvae of Trichoptera and Diptera. Diptera larvae were also dominant during spring and summer. In autumn period the largest amount in stomach content were Trichoptera larvae and Gastropoda. Plant material was present in stomach content but not dominant food item. The von Bertalanffy formula, counted from the back calculated growth in total length, appeared to be: Lt = 35.3 (1-e-0.15 (t+1.40)). The phiprime of Neretva chub (ln base) is Φ’=5.23. The length-weight relationship, including the fish from the entire growing period, demonstrated positive allometric growth with a b-value of 3.47. The average value for condition factor was CF = 0.98±0.14 (min = 0.76; max = 1.29).
The record is confirmed of a “Clariobranchus” hybrid Clarias gariepinus × Heterobranchus sp. specimen in the River Danube in Croatia. Clarias gariepinus was introduced to Europe for farming and research purposes. Because of their faster growth and short time to achieve market size, “Clariobranchus” hybrids have gained attention in European aquaculture. To date, no record has been found in the literature of “Clariobranchus” hybrid escapees in inland waters of Europe. The present finding suggests that the “Clariobranchus” hybrid escaped from an unprotected aquaculture system or open pond farm. The threat of establishment of a population of this hybrid in suitable environments, such as thermal ponds, cannot be ruled out.
Cobitis elongata and Sabanejewia balcanica from the family Cobitidae were collected monthly from September 2004 to October 2005 from the Petrinjčica River in the Danube basin of Croatia. On each sampling date, samples of the macrozoobenthos were taken from three different substrates. The density of the macrozoobenthos was calculated and compared with the diet of the loaches. During all months the most dominant group in the macrozoobenthos and in the guts of the analysed loaches was insect larvae of the family Chironomidae. Ivlev’s index was used as a measure of selectivity for various macroinvertebrate taxa in the fish rations and showed changing selectivity that indicate opportunistic feeding strategies and wide diet overlaps between the species.
The risk screening of non-native species that are likely to be invasive in a defined risk assessment area is crucial for implementing strategies of rapid response and mitigation to protect native biodiversity and socio-economic activities. However, for successful risk-ranking of the screened species, scientifically defensible evidence in support of the screening outcomes must be provided, and computation of a correctly calibrated threshold to distinguish between medium-risk and high-risk species must be achieved. This paper reviews published applications of the “second-generation” Weed Risk Assessment-type decision support tools (i.e. the Aquatic Species Invasiveness Screening Kit and the Terrestrial Animal Species Invasiveness Screening Kit) and evaluates them in terms of the above two requirements. Several procedural errors were identified that involved: i) lack of provision of the report with details of the species-specific screenings; ii) incomplete justifications for the responses in the toolkit questionnaire; iii) incomplete details of the protocol used for the a priori categorisation of the screened species for threshold computation; iv) unaccepted or non-existent taxonomic names for the screened species (including typographical errors). Guidelines are provided for both assessors and reviewers to ensure that these procedural errors are avoided in future applications of these risk screening toolkits.