Gobius Niger Research Articles

Multitrophic diversity sustains ecological complexity by dampening top-down control of a shallow marine benthic food web.

Biodiversity is typically considered as a one-dimensional metric (e.g., species richness), yet the consequences of species loss may be different depending on where extinctions occur in the food web. Here, I used a manipulative field experiment in a temperate subtidal marine system to explore the implications of diversity loss at multiple trophic levels for ecosystem functioning and food web structure. The four manipulated predators included the small painted goby and common prawn, which are also fed on by the larger black goby and shore crab. Antagonistic interactions between the manipulated predators (e.g., intraguild predation, intimidation, interference competition) limited their negative effects on the rest of the food web. Top-down control was so suppressed at the highest level of multitrophic diversity that the resulting food webs were as complex and productive as those containing no manipulated predators. Negative interactions between the predators weakened as multitrophic diversity decreased, however, resulting in stronger consumption of lower trophic levels and a simpler food web with lower rates of two key ecosystem processes: primary production and decomposition. These results show how indirect interactions between predators on multiple trophic levels help to promote the complexity and functioning of natural systems.

Spatial asymmetry of the paternity success in nests of a fish with alternative reproductive tactics

Guard-sneaker tactics are widespread among fish, where territorial males defend a nest and provide parental care while sneakers try to steal fertilizations. Territorials and sneakers adopt diverse pre- and post-mating strategies, adjusting their ejaculate investment and/or behavioural responses to the presence of competitors. The relative distance of competitors from the spawning female plays a major role in influencing male mating strategies and the resulting paternity share. However, territorial male quality and sneaking intensity do not fully account for the variability in the relative siring success occurring among species. An often neglected factor potentially affecting sneakers proximity to females is the nest structure. We conducted a field experiment using the black goby, whose nests show two openings of different size. We found that territorial males defend more and sneaking pressure is higher at the front, larger access of the nest than at the back, smaller one. Moreover, microsatellite paternity analysis shows that territorials sire more offspring at the back of their nest. Such a predictable spatial distribution of the paternity share suggests that nest structure might work as an indirect cue of male relative siring success, potentially influencing the territorial male investment in parental care and/or the female egg deposition strategy.

Differences in diet compositions and feeding strategies of invasive round goby Neogobius melanostomus and native black goby Gobius niger in the Western Baltic Sea

Differences in diet compositions and feeding strategies of invasive round goby Neogobius melanostomus and native black goby Gobius niger in the Western Baltic Sea

Reproduction and Seasonal Growth Estimates of the Black Goby, Gobius niger (Osteichthyes: Perciformes: Gobiidae) in the Southeastern Black Sea Region of Turkey

Seasonal growth pattern and reproductive biology of the black goby, Gobius niger, were studied in southern Black Sea between December 2012 and November 2013. The seasonal von Bertalanffy growth parameters, computed from ELEFAN, were estimated as L∞ = 11.90 cm TL, K = 0.701 year-1, C = 0.633, and WP = 0.492 for the Hoenig seasonal model and as L∞ = 12.14 cm TL, K = 0.680 year-1 for non-seasonal von Bertalanffy model. The size at sexual maturity (TL50) was estimated as 8.9 cm TL. The GSI ranged 0.60 in December and 8.57 in April (mean 3.82±0.818) for females and between 0.61 in October 2013 and 2.90 in May 2013 (mean 1.70±0.260) for males. The seasonal growth was pronounced probably due to reproduction activity which extended investment of energy in reproduction causing slower growth. The GSI development was related to photoperiod and the monthly variations of GSI values indicating that the intensive spawning occurred between April and August. During spawning time, the mean GSI value of females (6.04±1.177) was 2.9 times higher than the mean GSI values of males (2.08±0.423) (P < 0.05). The results of this study were offered as biological input parameters regarded as a reference for the conservation and management of the Black Sea stocks of the black goby.

Length-Weight Relationships of 12 Fish Species from the Köyceğiz Lagoon, Turkey

This study provides the length-weight relationships of 12 fish species that belong to ten families from the Köyceğiz Lagoon, Turkey; Dicentrarchus labrax (Linnaeus, 1758); Diplodus annularis (Linnaeus, 1758); Diplodus sargus (Linnaeus, 1758); Dussumieria elopsoides Bleeker, 1849; Engraulis encrasicolus (Linnaeus, 1758); Oreochromis niloticus (Linnaeus, 1758); Gobius niger Linnaeus, 1758; Mullus barbatus barbatus Linnaeus, 1758; Sparus aurata Linnaeus, 1758; Siganus rivulatus Forsskål & Niebuhr, 1775; Solea solea (Linnaeus, 1758); Trachinotus ovatus (Linnaeus, 1758). A total of 720 fish samples were collected with fish barrier, trammel net, beach seine and cast-net. The growth type of D. annularis (b=3.148), D. elopsoides (b=3.089), G. niger (b=3.154), S. solea (b=3.124) was determined as positive allometry and E. encrasicolus (b=2.814), D. labrax (b=2.764), T. ovatus (b=2.901) was determined as negative allometry whereas D. sargus (b=2.995), M. barbatus barbatus (b=3.003), O. niloticus (b=3.088), S. aurata (b=3.009) and S. rivulatus (b=3.079) showed isometry. The results of this investigation will contribute to further fishery studies in the Köyceğiz Lagoon.

Length-weight relationships for the fifty littoral and coastal marine fish species from the Eastern Adriatic Sea

The length–weight relationship parameters are reported for the fifty littoral and coastal marine fish species from the Eastern Adriatic. Captures were made between the years 2004 and 2017 during sport fishing competitions. The parameters a and b of the equation W = aLb were estimated. The b values ranged from 2.1972 for Spicara smaris (Linnaeus, 1758) to 3.7044 for Salaria pavo (Risso, 1810). The L-W relation for Scyliorhinus stellaris (Linnaeus, 1758), Gobius bucchichi Steindachner 1870, Gobius geniporus Valenciennes 1837 and Lipophrys trigloides (Valenciennes, 1836) are not available in FishBase and presents new data for these species. For some other species, such as Labrus mixtus Linnaeus 1758, there are only two relationships, but none from the Mediterranean, for Gobius paganellus Linnaeus 1758 only four relationships and none from Central and Eastern Mediterranean, while for Labrus merula Linnaeus 1758, Symphodus mediterraneus (Linnaeus, 1758), Symphodus roissali (Risso, 1810), Gobius cobitis Pallas 1814, Gobius cruentatus Gmelin 1789, Gobius niger Linnaeus 1758, Parablennius gatorugine (Linnaeus, 1758), Parablennius sanguinolentus (Pallas, 1814), Salaria pavo (Risso, 1810), and Bothus podas (Delaroche, 1809) very low number of relationships are presented and none from the Adriatic Sea.

Marmara Denizi’nde 17 Kemikli Balığın Boy-Ağırlık İlişkisi

Length weight relationship parameters were determined for 17 fish (Arnoglossus kessleri, Blennius ocellaris, Callionymus lyra, Cepola macrophthalma, Citharus linguatula, Lesueurigobius friesii, Merluccius merluccius, Lophius piscatorius, Merlangius merlangus, Gobius niger, Mullus barbatus, Solea solea, Spicara maena, Serranus hepatus, Trachurus trachurus, Trachurus mediterraneus, Uranoscopus scober) species in the Marmara Sea. Fish samples were collected monthly bases between September of 2011 and July of 2014 with a beam trawl. The growth type of each species were determined and the calculated b values changed in range from 1.2565 to 3.4018.

Analyses of the non-target catch from the Egyptian Mediterranean trawlers, off Port Said

The present study aimed to analyze the non-target catch in the Egyptian Mediterranean waters, off Port Said, during the period from spring 2017 to winter 2018. The analysis revealed that from 75 non-target species, fish constituted about 69.4% of the total catch weight, whereas invertebrates reached about 30.6%. For non-target fish, 51 fishes were identified (50 bony fishes and one elasmobranch), of which 17 lessepsian species were found. The high percentage of fish (82.67%) was with an average length between 4.0 and <9.0 cm. The highly represented fish species by numbers were: Engraulis encrasicolus (25.608%), Herklotsichthys punctatus (23.711%), Terapon puta (9.572%), Equulites klunzingeri (9.342%), Gobius niger (7.177%), Argyrosomus regius (6.280%), Alepes djedaba (4.155%), Gobius paganellus (3.397%), Sardinella aurita (2.525%), Ariosoma balearicum (1.093%) and Diplodus annularis (0.803%). Total analysis, seasonal analysis and an index of diversity (H′) for the non-target catch species were provided. On the other hand, length-weight relationship, condition factor and age composition were described for the most dominant species. For non-target invertebrates, 24 species were identified among which 13 lessepsian species were found. Shrimps and mantis shrimp Erugosquilla massavensis were the main constituents during the period of study. The authors propose to change the cod end mesh size from 2.5 cm to 4.0 cm to minimize the high percentage of non-target catch and preserve recruits of valuable species from over fishing along the Egyptian coast of the Mediterranean Sea while doing experiments to ensure the best results. Further, continuous monitoring and managements of trawlers must be put into consideration.

Feeding habits during migration of the Atlantic bonito Sarda sarda (Bloch, 1793) to the Black Sea

ABSTRACTInformation about food web dynamics is crucial for the success of ecosystem-based management. In order to collect such information, it is necessary to establish the dietary contents of species in the food chain. In this study, the diet of Atlantic bonito Sarda sarda (Bloch, 1793), one of the most important species in the Black Sea ecosystem, has been examined. The aim of this study was to investigate the prey preferences of Atlantic bonito over an eleven-year period during their feeding migration to the Black Sea. Sampling was carried out by commercial purse seine and gill nets along the Turkish Black Sea coast during migration of the Atlantic bonito from 2005 to 2016. Stomach contents were identified to the lowest possible taxonomic level. Atlantic bonito dietary composition was analyzed by fishing season, sex and size classifications. Results revealed a Vacuity Index value (V %) of 67% while 33% of individuals sampled had at least one prey species in their stomach content. Since S. sarda predominantly feed on small fish species, stomach contents contained mainly Engraulis encrasicolus, Trachurus mediterraneus, Sprattus sprattus, Mullus barbatus, Gobius niger, Merlangius merlangus, Pomatomus saltatrix, Alosa immaculata, Parablennius tentacularis and small unidentified prey items (tissue particles, … etc.). The most frequent prey item was E. encrasicolus with a percentage occurrence of 94%. In conclusion, the main prey species was determined as E. encrasicolus and statistical analyses of X2 was found significant (P < 0.005) according to year, sex and size.

Population dynamics and yield of the black goby Gobius niger L. in Algeria (Gulf of Annaba)

Event Abstract Back to Event Population dynamics and yield of the black goby Gobius niger L. in Algeria (Gulf of Annaba) Abderrahmane Kassar1*, Alaeddine Benallia1, Daoud Bouchelif1 and Farid Hemida1 1 École Nationale Supérieure des Sciences de la Mer et de l'Aménagement du Littoral, Algeria The black goby Gobius niger L., 1758 is a demersal gobiid fish caught by bottom trawl in the Gulf of Annaba (South Western Mediterranean). No published prior studies on its biology, population dynamics or stock assessment has been conducted in Algeria. A monthly sampling of this species has been done between Dec 2015 and May 2016 from commercial catch in order to estimate the growth, mortality and exploitation parameters of the stock for the first time in the Algerian Basin. Maximum total length (TL) and maximum total weight (TW) were 15.3 cm and 43.2 g, respectively. Power function type relationship between length and weight was obtained using 344 couples and it was written as TW = 0.0095*TL^3.0701. Estimated von Bertalanffy growth parameters using ELEFAN I routine in FiSAT II program were as follows: L∞ = 16.03 cm and K = 0.8 year-1. The estimated value of Total Mortality based on length converted catch curve was Z = 1.93 year-1. Natural Mortality calculated using Djabali et al. method (1994) based on the asymptotic length and the growth curvature was M = 0.6 year-1. Computed Fishing Mortality was F = 1.33 year-1. The Thompson & Bell model (1934) was used for stock assessment based on data obtained from Jones analysis (1983). Model estimated Maximum Sustainable Yield was MSY = 9 tonnes that corresponds to a 2.6 F-factor. As the reference yield is 8.5 t, there would be scope only to marginally increase the catch by 5.56%. A doubled fishing effort would increase the catch by 7%. Exploitation rate is at its optimum and the applied model recommends maintaining the actual catch. It could also be reduced by a third (loss of 9% of yield), which is more careful in order to protect the stock and preserve the resource in a sustainable way. References Djabali, F., Mehailia, A, Koudil, M., Brahmi B. (1994). A reassessment of equations for predicting natural mortality in Mediterranean teleosts. Naga, the ICLARM Quarterly 17:1, 33-34. Jones, R. (1984). Assessing the effects of changes in exploitation pattern using length composition data (with notes on VPA and cohort analysis). FAO Fisheries Technical Paper 256. Rome: Food and Agriculture Organization of the United Nations. Thompson, W. F., & Bell, F. H. (1934). Effect of changes in intensity upon total yield and yield per unit of gear. Report of the International Fisheries Commission 8, 7-49. Keywords: Algerian basin, Bottom trawling, Gobiidae, Mediterranean Sea, VBGM Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019. Presentation Type: Oral Topic: ECOLOGY AND LIFE CYCLES Citation: Kassar A, Benallia A, Bouchelif D and Hemida F (2019). Population dynamics and yield of the black goby Gobius niger L. in Algeria (Gulf of Annaba). Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00140 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Jul 2019; Published Online: 14 Aug 2019. * Correspondence: Mr. Abderrahmane Kassar, École Nationale Supérieure des Sciences de la Mer et de l'Aménagement du Littoral, Algiers, Algeria, a.w.kassar@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Abderrahmane Kassar Alaeddine Benallia Daoud Bouchelif Farid Hemida Google Abderrahmane Kassar Alaeddine Benallia Daoud Bouchelif Farid Hemida Google Scholar Abderrahmane Kassar Alaeddine Benallia Daoud Bouchelif Farid Hemida PubMed Abderrahmane Kassar Alaeddine Benallia Daoud Bouchelif Farid Hemida Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Tides and moon drive fish movements in a brackish lagoon

Brackish lagoons, on the edge between marine and freshwater ecosystems, are vulnerable aquatic environments that act as nursery grounds for several of the most commercially exploited fish families. We used long-term passive gear data, to investigate whether the moon and tides affected fish movement between inner and outer habitats in a Northern Mediterranean coastal lagoon. In particular, we used multivariate, threshold and non-linear correlation analyses to explore the relationship between fish catches and moon and tide variables in transitional habitats, accounting for the presence of potential prey and other major temporal and environmental variables. Fish movements between habitats were influenced by moon and tide factors, which had effects comparable to annual and seasonal variations, respectively. Overall, the magnitude of effects related to the moon parameters were smaller than most environmental parameters examined, but still larger than e.g. the presence of invertebrate prey (lagoon shrimp) or some of the tide factors. European flounder catches were positively correlated with disk illumination, while sand and black goby were influenced by the moon phase. Other benthic and pelagic species showed no significant correlation. Tide direction affected negatively the movement of boxlip mullet and tide amplitude prior to sampling had far more effect than tide amplitude during sampling. Water temperature, salinity and the presence of invertebrate prey (grey shrimp) had significant but contrasting effects on some, but not all, of the species examined. Ultimately, this information could improve the understanding of the drivers in these ecosystem as well as potentially provide useful insights for improved fisheries management.

Liver histopathology and biochemical biomarkers in Gobius niger and Zosterisessor ophiocephalus from polluted and non-polluted Tunisian lagoons (Southern Mediterranean Sea)

The aim of this study was to appraise the response of a multi-marker approach in fish species, Gobius niger and Zosterisessor ophiocephalus, in a polluted lagoon (Bizerte lagoon: MB and ML sites) and in a reference site (Ghar-El-Melh lagoon entrance) by the analysis of physiological indexes, liver histopathology and some biochemical biomarkers. The results showed liver hypertrophy in fish collected from Bizerte lagoon as well as many non-specific lesions, unlike the reference site. All Bizerte lagoon sites had the same prevalence of histopathological lesions, but the mean intensity (MI) of parasites seemed to be more sensible as an indicator of pollution levels. Indeed, parasite MI was more important in MB site that has a higher pollution level. Also, biochemical biomarkers showed an induction in Bizerte lagoon sites with some differences within sites and species. The impact of the continuous release of pollution on the biomarker's response is discussed.

Seminal fluid enhances competitiveness of territorial males' sperm in a fish with alternative male reproductive tactics.

The most common adaptation to sperm competition in males is represented by an increase in the sperm number and/or quality released at mating, to raise their probability of egg fertilization. However, rapidly mounting evidence highlights that seminal fluid may directly influence the competitive fertilization success of a male by affecting either own and/or rival sperm performance. In the black goby, Gobius niger, an external fertilizer with guard-sneaker mating tactics and high sperm competition level, sneaker ejaculates contain less seminal fluid and more sperm, that are also of better quality, than those of territorial males. However, territorial males gain a higher paternity success inside natural nests. Here, we ask whether the seminal fluid can contribute to the reproductive success of territorial males by enhancing their sperm performance and/or by decreasing that of sneaker males. Using sperm and seminal fluid manipulation and in vitro fertilization tests, we found that own seminal fluid influences the velocity and fertilization ability of sperm only in territorial males, making them as fast as those of sneakers and with a similar fertilization rate. Moreover, both sneaker and territorial sperm remain unaffected by the seminal fluid of rival males. Thus, black goby males respond to the different level of sperm competition faced by differential allocation of sperm and non-sperm components of the ejaculate, with sneakers primarily investing in sperm of intrinsic high quality and territorial males relying on the effect of seminal fluid to increase the lower intrinsic quality of their sperm.

Genetic analysis reveals the diversity of larval Gobiidae in a temperate estuary

Using molecular tools to examine Gobiidae, the second most abundant taxon in ichthyoplankton samples in the Gulf of Riga (Baltic Sea), the sand goby Pomatoschistus minutus was the most abundant taxon (82% of all individuals analysed), the common goby Pomatoschistus microps constituted 12% and the black goby Gobius niger 6%. The spatiotemporal distribution of P. microps and G. niger indicated a preference for habitats closer to the river inlet and their abundances increased slightly towards the end of the sampling period in summer. The species composition was interpreted in the context of the prevailing habitat conditions, characterized by extremely low water transparency, low salinity, limited spread of vegetated area and dominance of sandy-muddy substrata.

Marinas as habitats for nearshore fish assemblages: comparative analysis of underwater visual census, baited cameras and fish traps

Understanding the ecological role that artificial structures might play on nearshore fish assemblages requires the collection of accurate and reliable data through efficient sampling techniques. In this work, differences in the composition and structure of fish assemblages between the inner and outer sides of three marinas located in the temperate northern-eastern Atlantic Ocean were tested using three complementary sampling techniques: underwater visual censuses (UVC), baited cameras (BCs) and fish traps (FTs). UVCs and BCs recorded a comparable number and relative abundance of species, which in turn were much greater than those recorded by FTs. This finding supports the use of UVCs and BCs over FTs for broad ecologically studies, especially when dealing with structurally complex habitats such as artificial structures. We found differences in fish assemblage structure between the inner and outer sides of marinas, independently of the sampling method. Four small-sized species (Similiparma lurida, Thalassoma pavo, Sarpa salpa and Symphodus roissali) associated with structurally complex vegetated habitats dominated, in terms of abundance, the outer sides of marinas; Diplodus vulgaris, Diplodus sargus and Gobius niger, species with high ecological plasticity in habitat requirements, dominated the inner sides of marinas. The information provided in this study is of great interest for developing sound monitoring programmes to ascertain the effects of artificial structures on fish communities.

Temporal Variation in the Trophic Levels of Secondary Consumers in a Mediterranean Coastal Lagoon (Cabras Lagoon, Italy)

Trophic levels (TLs) of fish were estimated on three sampling dates (March, May, and August 2006) for different fish sizes in the Cabras Lagoon (Sardinia, Italy). A temporal TL variation for Atherina boyeri, Gobius niger, and Engraulis encrasicolus was observed. In March and May, the TL ranged from 3.3 to 3.4, characterizing these species as secondary consumers, while in August, this range moved to between 3.7 and 3.8, indicating a TL shift towards tertiary consumers. For Liza ramada, TL was consistently lower in small individuals (mean TL 2.5) than in larger individuals (mean TL 3.0). Increased TL of the fish species A. boyeri, G. niger, and E. encrasicolus in August was consistent with the seasonal changes in the macrobenthic assemblage in this system, with a dominance of primary consumers (benthic deposit feeders) in winter–spring and a dominance of secondary consumers (the nereidids Alitta succinea and Hediste diversicolor) in summer. These fish species took advantage of the high availability of nereidids leading to a rise in their TL values. Furthermore, the increase of TL with size of L. ramada, the most economically valuable fish species in the Cabras Lagoon, indicated an ontogenetic diet shift, the juveniles being omnivorous, while the adults being secondary consumers. We conclude that variability in the trophic levels of fish due to species traits, ontogenetic diet shifts, and variation in prey availability should be taken into account to further understand the food web structure of coastal lagoons.

Seasonal rhythm of physiological indexes, liver protein level, and biotransformation biomarkers in Zosterisessor ophiocephalus and Gobius niger from a low contaminated lagoon (Ghar El Melh lagoon, Tunisia)

This study assessed seasonal variation of total liver proteins level (LPLs) and biotransformation biomarkers in two fish species, G. niger and Z. ophiocephalus, during a one year-survey in the low contaminated Ghar-El-Melh lagoon, Tunisia. Analyzed biomarkers were compared with physiological indexes such as the condition index, hepato-somatic index, and gonado-somatic index and environmental parameters. A significant annual rhythms of glutathione-S-transferase and ethoxyresorufin-O-deethylase activities were validated by cosinor. The highest peak (acrophase) of activities occurred in summer likely related to the elevated seawater temperature. Midline Estimating Statistic of Rhythm and amplitudes were higher in Z. ophiocephalus than in G. niger. The results showed, as well, an acrophase of (LPLs) in spring coinciding with reproductive period in Z. ophiocephalus and beginning of reproductive period in G. niger. This study established a baseline for the selected enzymatic activities in gobies, which required information for a correct interpretation of biomarker responses in environmental monitoring.

The diet of the Mediterranean Shag Phalacrocorax aristotelis desmarestii roosting along the Slovenian coast

Abstract Five hundred pellets of the Mediterranean Shag Phalacrocorax aristotelis desmarestii were collected at three roost-sites along the Slovenian coast and analysed. The diet was characterized mostly by the dominance of bottom dwelling fish species of the appropriate size. The Black Goby Gobius niger was the most dominant prey and represented the Shag’s main prey in the studied area (IRI% = 64.0). The results of the study confirm that the Mediterranean Shag preys mainly on fish species which are without commercial value for local fisheries.

Karadeniz’de ıskarta türlerin (Uranoscopus scaber, Neogobius melanostomus ve Gobius niger) yaş, büyüme ve ölüm oranları

Uranoscopus scaber, Neogobius melanostomus and Gobius niger are called non-commercial fish species and also caught as discarded in Turkish fisheries. Samplings were carried out by bottom trawl, gillnet, purse seine net operations in the Turkish Black Sea coasts. The results of the study showed that the age of these species were 0-V ages for Uranoscopus scaber and Gobius niger , and 0-VII ages for Neogobius melanostomus for both sexes. The von Bertalanffy growth parameters, total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were calculated for each species separately.

The trophic position of the Atlantic blue crab Callinectes sapidus Rathbun 1896 in the food web of Parila Lagoon (South Eastern Adriatic, Croatia): a first assessment using stable isotopes.

The Atlantic blue crab Callinectes sapidus is to date widely distributed in the Mediterranean Sea, where is recognized as an Invasive Alien Species. Noticeably, while records of its occurrence are increasing, quantitative information on its functional role in the benthic food webs of invaded coastal habitats are scarce.Here, carbon and nitrogen isotopic signatures were measured in C. sapidus and other representative taxa of the benthic flora and fauna sampled in summer in the Parila Lagoon, a coastal basin located in the Neretva River estuary area (Croatia). d15N values of individual blue crab specimens were used to calculate their trophic position (TP) , using the filter feeder mussel Mytilus galloprovincialis as the isotopic baseline. In general, the isotopic signature of C. sapidus was comparable with those characterizing invertebrate and fish predators (e.g., Hexaplex trunculus, Gobius niger). An average trophic position of 3.73 was estimated for the blue crab population. However, a considerable inter-individual variation was observed in TP values, significantly related with the size of the specimens. Interestingly, a hump-shaped quadratic polynomial resulted the best fitting model for the data, characterized for small-size individuals by a positive body size-TP relationship, leveling or even turning negative for larger adult crabs. The interplay between environmental factors and ontogenetic diet shifts in determining the trophic position of the blue crab and, ultimately, its ecological impact on the benthic community of the Parila Lagoon is discussed.