Tatjana Dobroslavić

Bio: Tatjana Dobroslavić is an academic researcher from University of Dubrovnik. The author has contributed to research in topics: Population & Fishery. The author has an hindex of 5, co-authored 20 publications receiving 88 citations.

First record of Lagocephalus sceleratus in the Adriatic Sea (Croatian coast), a Lessepsian migrant

Abstract: Le premier signalement en mer Adriatique du poisson migrateur lessepsien Lagocephalus sceleratus (Gmelin, 1789) a ete enregistre le 17 octobre 2012. Une femelle sexuellement mature (Lt = 66.3 cm) et pesant 3,531 kg a ete capturee sur la cote nord de l'ile de Jakljan (Adriatique sud).

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

Abstract: Population 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...

On the reproduction of the Mediterranean keystone limpet Patella rustica: histological overview

Abstract: The reproductive cycle of the high shore limpet Patella rustica is described based on histological analysis as the primary method of staging gonad development. Sex ratios, shell length at sexually maturity, gonad developmental stages, mean gonad index and oocyte size were investigated. Males and females were found to differ in size distribution, with females becoming more prevalent from ~28 mm onwards. The estimated shell length at which 50% of males were sexually mature was 13.1 mm. Patella rustica has only one reproductive cycle per year with spawning peak between November and December for both sexes and gonad redevelopment from January. First data on the size frequency analysis of oocyte for this species are also presented, concurring with the qualitative analysis of gonad developmental stages. This study presents updated information on the reproductive cycle of this keystone species and provides first account of the reproductive biology of P. rustica in the Adriatic Sea.

Diet overlap of juvenile salema (Sarpa salpa), bogue (Boops boops) and common two-banded sea bream (Diplodus vulgaris) in the south-eastern Adriatic

Abstract: The food compositions of salema Sarpa salpa, bogue Boops boops and common two-banded seabream Diplodus vulgaris in the Donji Molunat Bay (south- eastern Adriatic) were studied in order to evaluate the diet overlap among them. Fish were collected from March to July 2009 using beach seine net. Three species of crustaceans were the most common prey, the most abundant were copepods. A significant overlap in the diet calculated using Schoener's index was recorded in May when the index was 0.9266 for bogue and salema, 0.6091 for bogue and common two-banded seabream, and 0.6142 for common two-banded seabream and salema.

Reproductive patterns of bogue, Boops boops (Sparidae), in the southeastern Adriatic Sea

Abstract: The reproductive characteristics of bogue (Boops boops) in the southeastern Adriatic Sea are presented in this study. The analysis is based on 676 specimens caught by seine net from December 2011 to November 2012. Total length of females ranged from 13.3 to 29.3 cm and males from 15.1 to 26.3 cm. The overall sex ratio of females to males was 1:0.85 (χ2=4.314; P < 0.05) with a slightly higher number of females in the largest size class. Length-weight relationship for the total population indicated negative allometric growth (b=2.911). Values of the condition factor are relatively low for both sexes. Maximum values were recorded in September 1.025 for females and 1.029 for males. Gonadosomatic index and histological examination showed that the spawning season of the bogue in the Adriatic is from January to May with peak in February. Six stages of gonad development were identified: immature, undergoing maturation, ripening, ripe, spawning and spent. The monthly distribution of the different sexual maturity stages and the frequency distribution of oocyte diameter revealed that this species is a batch spawner.

The enlargement of the Suez Canal – Erythraean introductions and management challenges

Abstract: The Suez Canal is the main pathway of introduction of non-indigenous species into the Mediterranean Sea. The successive enlargements of the Suez Canal have raised concern over increasing propagule pressure resulting in continuous introductions of new non-indigenous species and associated degradation and loss of native populations, habitats and ecosystem services. The United Nations Environment Programme (UNEP) through its Barcelona Convention has pledged to protect the biological resources, habitats and ecosystem services of the Mediterranean Sea, and have committed to spatial protection measures. Yet, UNEP shied away from discussing, let alone managing, the influx of tropical non-indigenous biota introduced through the Suez Canal. Surveys, funded by the Regional Activity Centre for Specially Protected Areas (UNEP RAC/SPA), established by the Contracting Parties to the Barcelona Convention, revealed that marine protected areas in the eastern Mediterranean have been inundated by these non-indigenous species, and may in fact function as hubs for their secondary dispersal. We call attention to the failure of an environmental policy that left the entire Mediterranean Sea prone to colonization by highly impacting non-indigenous species, including poisonous and venomous ones. Scientific research has been documenting this bioinvasion for over a century, yet beyond the ambit of marine scientists there is a lack of awareness of the scale of Mediterranean-wide consequences and scant appetite to enact the necessary environmental policies.

Jellyfish as prey: frequency of predation and selective foraging of Boops boops (Vertebrata, Actinopterygii) on the mauve stinger Pelagia noctiluca (Cnidaria, Scyphozoa).

Abstract: In recent years, jellyfish blooms have attracted considerable scientific interest for their potential impacts on human activities and ecosystem functioning, with much attention paid to jellyfish as predators and to gelatinous biomass as a carbon sink. Other than qualitative data and observations, few studies have quantified direct predation of fish on jellyfish to clarify whether they may represent a seasonally abundant food source. Here we estimate predation frequency by the commercially valuable Mediterranean bogue, Boops boops on the mauve stinger jellyfish, Pelagia noctiluca, in the Strait of Messina (NE Sicily). A total of 1054 jellyfish were sampled throughout one year to quantify predation by B. boops from bite marks on partially eaten jellyfish and energy density of the jellyfish. Predation by B. boops in summer was almost twice that in winter, and they selectively fed according to medusa gender and body part. Calorimetric analysis and biochemical composition showed that female jellyfish gonads had significantly higher energy content than male gonads due to more lipids and that gonads had six-fold higher energy content than the somatic tissues due to higher lipid and protein concentrations. Energetically, jellyfish gonads represent a highly rewarding food source, largely available to B. boops throughout spring and summer. During the remainder of the year, when gonads were not very evident, fish predation switched towards less-selective foraging on the somatic gelatinous biomass. P. noctiluca, the most abundant jellyfish species in the Mediterranean Sea and a key planktonic predator, may represent not only a nuisance for human leisure activities and a source of mortality for fish eggs and larvae, but also an important resource for fish species of commercial value, such as B. boops.

Cross-validation of δ15N and FishBase estimates of fish trophic position in a Mediterranean lagoon: The importance of the isotopic baseline

Abstract: FishBase, a relational database freely available on the Internet, is to date widely used as a source of quantitative information on the trophic position of marine fish species. Here, we compared FishBase estimates for an assemblage of 30 fish species sampled in a Mediterranean lagoon (Acquatina lagoon, SE Italy) with their trophic positions calculated using nitrogen stable isotopes. To assess the influence of the trophic level used to compute the baseline indicator on the robustness of isotopic estimations, we compared the trophic position of fish calculated using the average δ 15 N signature of either basal resource or primary consumer taxa measured at three stations located in the lagoon in July and November 2007. In general, basal resources showed negligible among-station and inter-season variations in their δ 15 N values; however, they were characterized by a high inter-specific heterogeneity, with signatures varying by approximately 10 per mil units. In contrast, whereas primary consumer signatures showed significant spatial and temporal variations, they were characterized by a lower inter-specific variability. Fish trophic positions estimated using primary consumers as the isotopic baseline were highly correlated with values provided by FishBase, independently from whether the latter were calculated on either diet data or individual prey items. Conversely, estimations using a basal resources as the baseline indicator were significantly less correlated with FishBase estimates. The present study emphasized the crucial importance played by inter-specific variability in baseline taxa signatures for a robust assessment of fish trophic position, and confirmed primary consumers as the best candidate for baseline estimation. In addition, our results indicate that, notwithstanding the limitations characterizing the data provided in FishBase, they represent an adequate source of information on the trophic ecology of fish.

Current status and trends of biological invasions in the Lagoon of Venice, a hotspot of marine NIS introductions in the Mediterranean Sea

Abstract: This paper provides an updated account of the occurrence and abundance of non-indigenous species (NIS) in an area of high risk of introduction: the Lagoon of Venice (Italy). This site is a known hotspot of NIS introductions within the Mediterranean Sea, hosting all the most important vectors of introduction of marine NIS—shipping, recreational boating, shellfish culture and live seafood trade. The recent literature demonstrates that the number of NIS in Venice is continuously changing, because new species are being introduced or identified, and new evidence shows either an exotic origin of species previously believed to be native, or a native origin of formerly believed “aliens”, or demonstrates the cryptogenic nature of others. The number of NIS introduced in the Venetian lagoon currently totals 71, out of which 55 are established. This number exceeds those displayed by some nations like Finland, Portugal or Libya. Macroalgae are the taxonomic group with the highest number of introduced species (41 % of NIS): the most likely vector for their introduction is shellfish culture. The source region of NIS introduced to Venice is mainly represented by other Mediterranean or European sites (76 %). The Lagoon of Venice represents a sink but also a source of NIS in the Mediterranean Sea, as it is the site of first record of several NIS, which have since further spread elsewhere.