A Comparison of Traditional and Locally Novel Fishing Gear for the Exploitation of the Invasive Atlantic Blue Crab in the Eastern Adriatic Sea

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 Mediterranea

Summer Fish Migrations in the River Neretva (South-Eastern Adriatic Coast, Croatia) as a Consequence of Salinization

River Neretva Estuary, located in the middle South-Eastern Adriatic coast, is a very important traditional fishery ground and biodiversity-rich ichthyologic area. Historically, the estuary situated in Croatia and Bosnia and Herzegovina was composed of wetlands, lakes, and lagoons, but in the 20th century, it was changed into a large agriculture area, settlements and port facilities. The major flow was channelled with large banks to prevent floods. All these activities enabled significant intrusion of seawater 20 km into the inland area. This led to the marinization of major flow freshwater ecosystems. This article presents data on summer fish migrations along with the major flow of River Neretva, during the May-September period. The temperature and salinity showed that seawater started to enter inland major flow from middle May up to the end of September. In total, the 1,429 fish individuals were caught. The numerically dominant species were Atherina boyeri (23.58%), Sardina pilchardus (21.62%), Sparus aurata (11.20%), Chelon ramada (8.19%) and Solea solea (7.63%). Dominant species in the total mass were: Chelon ramada (43.45%), Solea solea (14.27%), Sparus aurata (10.14%), Chelon aurata (7.66%) and Anguilla anguilla (3.75%). The major result of this study points to the fact that major Neretva flow of 20 km in length from the river mouth is under seasonal summer impact of seawater, which leads to salinization and complete marinization of this ecosystem during the warm period of the year. The marinization of the large Neretva flow area creates new nursery and feeding grounds for marine estuarine opportunist fish species, such as small pelagics European pilchard and anchovy, and also enlarge these grounds for the marine estuarine dependent species, such as grey mullets, sea breams, and flatfishes

Potential for acclimation of banded-dye murex, Hexaplex trunculus (Linnaeus, 1758) after long-term exposure to low pH

Previous work on ocean acidification highlighted contrasting response between marine species and population. This so-called species-specific response was hypothesized to be partly a consequence of local adaptation to the present range of natural variability in the carbonate chemistry. Under that hypothesis, species tolerance threshold should be correlated to its environmental pH niche. This paper aims to evaluate shell growth rate of Hexaplex trunculus, an important predatory gastropod in benthic communities of Mali Ston Bay. A long-term experiment (310 days) was designed to test a range of pH treatments covering present and future pH levels relevant in the context of future ocean acidification (7.95-7.22 pHT) at the sampling site. Sex had an effect on the shell growth rate irrespective of pH, and was only significant after 236 days. As growth rate in all pH treatments followed seasonal patterns correlating to changes in seawater temperature, the data were divided into 3 time periods. A positive relationship between shell growth rate (SGR, mm day-1) and pH was observed for the period 1-59 days (temperature ranging between 26.5 & 18.8 °C), whereas SGR decreased significantly with pH for the following period (60-236 days, temperature ranging between 20.6 & 8.5 °C). After 236 days (temperature ranging between 27.5 & 14.1 °C), there was no significant difference in SGR among pH. Similar temperature was experienced between the first and third period and the difference in response could be explained as a consequence of an acute negative response versus a longer exposure indicating possible potential for acclimation. Our results highlight the modulating effect of temperature and the importance of long-term experiments to better assess impacts of ocean acidification on marine organisms

Istraživanje europske jegulje, Anguilla anguilla u ušću rijeke Neretve (istočni Jadran, Hrvatska) korištenjem tradicionalnih ribolovnih alata

Samples of the European eel, Anguilla anguilla from two different habitats in the River Neretva estuary region were analysed using two different traditional fishery gear, in the period from 2016 to 2019. The monthly eel catches in ten traditional fyke nets in Parila lagoon varied from 4.4 to 12.7 kg (±2.45 kg) in 2016 and 2.4 to 9.6 kg (±2.01 kg) in 2019. There were no statistical differences between monthly and total weights recorded in 2016 and 2019 (t=1.04; p=0.312). The b-coefficient of the length-weight (LW) relationship for the freshwater eel samples varied from 3,1036 to 3,3206 during two-year period of the sampling. The LW relationship for the brackish population was significantly lower (b-coefficient 2,6513). The dominant eel stage in both sites was yellow eel, while silver stage was scarce. The fishery with traditional devices revealed that efficiency of these artisanal tools is low, pointing to poor abundance of eel in their common habitats. The recorded catch using bigger traditional eel trap gear during autumn spawning migrations was also dominated with yellow stage, while silver eel represented only 15,4% of the catch. The infestation of eels with the parasite, Anguillicoloides crassus was significantly higher in freshwater habitat (41% of eel specimens infested) than in brackish, Parila lagoon (7%). Poor efficiency of traditional gear, bad length and weight structure of the population and low b-coefficients of eels in their most important habitat, indicate poor status of European eel population and River Neretva estuarine ecosystems.Europska jegulja, Anguilla anguilla analizirana je u dva različita staništa u delti Neretve pomoću dva različita tradicionalna ribolovna alata za jegulju u razdoblju od 2016. do 2019. Ulov jegulje u deset tradicionalnih vrša za jegulje u laguni Parila kolebao je mjesečno od 4,4 do 12,7 kg (± 2,45 kg) u 2016. godini i od 2,4 do 9,6 kg (± 2,01 kg) u 2019. godini. Nije bilo statističke razlike između mjesečnih i ukupnih masa zabilježenih u 2016. i 2019. godini (t = 1,04; p = 0,312). b-koeficijent odnosa duljine i mase (LW) za jegulje iz slatkovodnog područja kolebao je od 3,1036 do 3,3206 tijekom dvije godine uzorkovanja. Odnos LW za jegulje iz bočatog staništa bio je značajno niži (b-koeficijent 2.6513). Dominantni stadij jegulje u oba područja bila je žuta jegulja, dok je srebrna jegulja bila rijetka. Ribolov tradicionalnim ribolovnim alatima pokazao je da je učinkovitost ovih alata niska, što ukazuje na malu brojnost jegulja u njihovim tradicionalnim staništima. Ulovom u “trati”- tradicion- alnom alatu za ulov jegulje tijekom jesenskih migracija dominirala je također žuta jegulja, sa samo 15,4% ulova srebrne jegulje. Zaraženost jegulja parazitom Anguillicoloides crassus bila je znatno veća u slatkovodnom staništu (41%), u usporedbi sa 7% jegulja iz bočate lagune Parila. Slaba ribolovna učinkovitost tradi- cionalnog ribolovnog alata, loša duljinska i masena struktura populacije i niski b-koeficijenti jegulja u najvažnijem staništu jegulje ukazuju na loš status populacije neretvanske jegulje i ekosustava ušća rijeke Neretve

Records of New Fish Species in the River Neretva Estuary: Potential Threat to Coastal Adriatic Nursery

Specimens of the three new fish species were recorded during 2015 and 2016 in the River Neretva Estuary. These species are: White trevally, Pseudocaranx dentex (Bloch and Schneider, 1801), Pilotfish, Naucrates ductor (Linnaeus, 1758) and White grouper, Epinephelus aeneus (Geoffroy Saint–Hilaire, 1817). The characteristics of caught specimens and their history of records in Adriatic Sea are described. Potential impact of new species invasion in the Neretva Estuary as a major Eastern Adriatic nursery habitat is discussed

Population Dynamics and Reproduction of Mediterranean Green Crab Carcinus aestuarii in Parila Lagoon (Neretva Estuary, Adriatic Sea, Croatia) as Fishery Management Tools

AbstractPopulation structure, age, growth, mortality, and reproduction patterns of the Mediterranean green crab Carcinus aestuarii were determined for the native population in Parila Lagoon (Neretva Estuary, Middle Adriatic, Croatia). The population size structure showed two distinct cohorts: (1) specimens with a carapace width of 20–34 mm and dominated by females and (2) large-sized specimens with a carapace width > 34 mm with males significantly dominating and no females found above 46 mm. Males appeared to grow faster than females in the first and second year of the life cycle. Most of the natural mortality (70.4%) occurred during the first year of life. This indicates high predation pressure from fish and other crab species on small-sized (less than 25 mm) C. aestuarii cohorts. The peak of ovigerous female occurrence occurred in January 2015. A very small percentage of ovigerous females appeared in June 2015. The 50% ovigerous size for the population was estimated at a carapace width of 29.65 mm and w..

Population structure of the invasive Atlantic blue crab, Callinectes sapidus on the Eastern Adriatic coast (Croatia, Montenegro)

The Atlantic blue crab, Callinectes sapidus, is a highly invasive species that poses a significant threat to Mediterranean ecosystems. In the last two decades, it has become established in several marine and estuarine areas of the eastern Adriatic Sea, resulting in a decline in commercial catches and damage to fishing gear. This article reviews the current status of blue crab invasion in Montenegro and Croatia and analyses its abundance and population structure. Overall 619 crabs were sampled (male:female ratio, 1:1.91). Both carapace width and weight differed significantly between males and females, with males having a wider carapace and more weight. There was a significant difference in carapace width and weight among sites. For the total population, the mean male and female carapace width was 130.3 ± 30.8 and 108.8 ± 41.4 mm, respectively. In addition, the mean male and female weight was 187.2 ± 85.6 and 132.5 ± 39.1 g, respectively. Coefficient b between the weight and carapace width of blue crabs was significant at all locations, although it varied between males and females. This work will also document the impacts of the blue crab invasion on local ecosystems and provide comprehensive overview of populations structures and shed light on this important aspect of blue crab ecology

Neobični nalazi morskih organizama u rijeci Neretvi (Hrvatska i Bosna i Hercegovina)

This paper presents a review of the unusual occurrences of various marine species found upstream in the Neretva River and its wider delta zone in the last two decades. The occurrences of at least eight different marine species were reported by local fishermen, representing very rare records of these species in the upstream areas of rivers. Although some of these species generally inhabit both saltwater and brackish waters, their occurrences high upstream are probably the consequence of changes in hydrological conditions in Neretva River. Namely, more intense saltwater intrusion into the river observed in the last two decades provides suitable conditions for mass penetration of euryhaline organisms high into the Neretva River. In this biodiversity rich area which hosts a significant number of endemic species, such phenomena can threaten the local freshwater communities.U radu je prikazan pregled neobičnih nalaza morskih vrsta u rijeci Neretvi te širem području njene delte u posljednja dva desetljeća. Pojava najmanje 8 različitih morskih vrsta prijavljena je od strane lokalnih ribara, a radi se o općenito rijetkim nalazima morskih organizama u uzvodnim dijelovima riječnih tokova. Iako neke od vrsta opisanih u radu obitavaju i u slanim i u bočatim vodama, njihova pojava visoko uzvodno vjerojatno je posljedica promjena hidroloških uvjeta u rijeci Neretvi. Naime, intenzivniji prodor morske vode u rijeku u posljednja dva desetljeća omogućava masovno prodiranje eurihalnih organizama visoko u rijeku Neretvu. Na ovom području, bogatom biološkom raznolikošću sa značajnim brojem endemskih vrsta, takve pojave mogu ugroziti zajednice slatkovodnih organizama

An individual-based dataset of carbon and nitrogen isotopic data of Callinectes sapidus in invaded Mediterranean waters

[EN] Background The characterisation of functional traits of non-indigenous and invasive species is crucial to assess their impact within invaded habitats. Successful biological invasions are often facilitated by the generalist diet of the invaders which can modify their trophic position and adapt to new ecosystems determining changes in their structure and functioning. Invasive crustaceans are an illustrative example of such mechanisms since their trophic habits can determine important ecological impacts on aquatic food webs. The Atlantic blue crab Callinectes sapidus is currently established and considered invasive in the Mediterranean Sea where it has been recorded for the first time between 1947 and 1949. In the last decade, the blue crab colonised most of the eastern and central Mediterranean Sea and the Black Sea and it is currently widening its distribution towards the western region of the basin. New information Stable isotope analysis is increasingly used to investigate the trophic habits of invasive marine species. Here, we collated individual measures of the blue crab d C and d N values and of its potential invertebrate prey into a geo-referenced dataset. The dataset includes 360 records with 236 isotopic values of the blue crab and 224 isotopic data of potential prey collected from five countries and 12 locations between 2014 and 2019. This dataset allows the estimation of the trophic position of the blue crab within a variety of invaded ecosystems, as well as advanced quantitative comparisons of the main features of its isotopic niche.Di Muri, C.; Rosati, I.; Bardelli, R.; Cilenti, L.; Veli, DL.; Falco, S.; Vizzini, S.... (2022). An individual-based dataset of carbon and nitrogen isotopic data of Callinectes sapidus in invaded Mediterranean waters. Biodiversity Data Journal (Online). 10:1-12. https://doi.org/10.3897/BDJ.10.e775161121

A global-scale screening of non-native aquatic organisms to identify potentially invasive species under current and future climate conditions

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium-and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement. Decision support tools AS-ISK Hazard identification Non-native species Risk analysis Climate changepublishedVersio