Oblada Research Articles

A case of abnormal swimming patterns in juvenile Oblada melanura naturally infected with Philometra obladae (Nematoda: Philometridae) in the Tyrrhenian Sea off Sicily, Italy

The saddled seabream, Oblada melanura (L.), is a common seawater species present in the Mediterranean. Between July and August 2023, during diving activities along the Sicilian coast of Italy, we recorded with a digital camera several specimens of O. melanura showing an abnormal pattern of swimming in the water column. The unusual swimming behaviour was characterized by fast, uncoordinated directional changes and isolation from the remaining fishes in the shoal. Four dead fish were found and collected for necropsy and parasitological evaluation/examination. Upon gross examination, all fish showed an evident coelomic distension; the coelomic cavity of two fish was filled with nematodes that dislocated the coelomic organs, and the other two had degraded nematodes and a conspicuous quantity of fluid in the coelomic cavity. All collected parasites were identified as Philometra obladae (Nematoda: Philometridae) according to morphological criteria. Here, we describe the unusual swimming behaviour of O. melanura naturally infected with Ph. obladae and the results of the examination of dead fish infected with this parasite. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Ph. obladae infection in wild O. melanura.

Host-microbiota-parasite interactions in two wild sparid fish species, Diplodus annularis and Oblada melanura (Teleostei, Sparidae) over a year: a pilot study

BackgroundThe microbiota in fish external mucus is mainly known for having a role in homeostasis and protection against pathogens, but recent evidence suggests it is also involved in the host-specificity of some ectoparasites. In this study, we investigated the influence of seasonality and environmental factors on both fish external microbiota and monogenean gill ectoparasites abundance and diversity and assessed the level of covariations between monogenean and bacterial communities across seasons. To do so, we assessed skin and gill microbiota of two sparid species, Oblada melanura and Diplodus annularis, over a year and collected their specific monogenean ectoparasites belonging to the Lamellodiscus genus.ResultsOur results revealed that diversity and structure of skin and gill mucus microbiota were strongly affected by seasonality, mainly by the variations of temperature, with specific fish-associated bacterial taxa for each season. The diversity and abundance of parasites were also influenced by seasonality, with the abundance of some Lamellodiscus species significantly correlated to temperature. Numerous positive and negative correlations between the abundance of given bacterial genera and Lamellodiscus species were observed throughout the year, suggesting their differential interaction across seasons.ConclusionsThe present study is one of the first to demonstrate the influence of seasonality and related abiotic factors on fish external microbiota over a year. We further identified potential interactions between gill microbiota and parasite occurrence in wild fish populations, improving current knowledge and understanding of the establishment of host-specificity.

Breaking the paradigm: Marine sediments hold two-fold microplastics than sea surface waters and are dominated by fibers

We conducted one of the first studies to integrate the quantification and characterization of microplastics (MPs), including fibers, in different habitats (sea surface, seafloor and beach sediments) of a coastal Mediterranean marine protected area, analyzing their ingestion in several marine species. The objectives of the study were to evaluate the distribution of MPs according to shape and polymer, to assess the contribution of fibers to local plastic pollution and to evaluate their ingestion in fish and invertebrates species that inhabit the study area (Pagrus pagrus, Serranus scriba, Spondyliosoma cantharus, Diplodus vulgaris, Oblada melanura, Holothuria forskalii, Holothuria tubularis, Holothuria polis, Arbacia lixula, Paracentrotus lividus, Modiolus barbatus, Mytilus galloprovincialis and Arca noae). A total of 111 environmental samples were analyzed. The mean abundance of MPs (excluding fibers) quantified in beach sediments (13,418.86 ± 28,787.99 MPs/m2) was two orders of magnitude higher than that found in seafloor sediments (76.92 ± 108.84 MPs/m2), which in turn was two orders of magnitude higher than sea surface samples (0.17 ± 0.39 MPs/m2). The fibers were the most abundant shape of MPs identified in all habitats. Variability in MPs ingestion was detected between species, with ingestion rates ranging from 43 % to 100 % for general MPs and ranging from 7 % to 100 % for fibers. The highest ingestion was observed in Holoturians, representing suitable bioindicators for plastic pollution. The composition of the polymer varies weakly depending on habitats and biota, but the result is strongly correlated with the morphology of the plastic. Fibers were mainly composed of cellulose acetate (29 %), styrofoam of polystyrene (18 %), and filaments, films and fragments of polyethylene and polypropylene. The results highlighted the need to expand integrated approaches to effectively study marine plastic pollution and to undertake efficient actions to limit the input of plastics, particularly fibers, into the marine environment.

İzmir Körfezi'nde (Türkiye'nin Ege Denizi Kıyısı) Dağılım Gösteren Başlıca Ticari Balık Türlerinin Boy-Ağırlık ve Boy-Boy İlişkileri / 2020-2021 Av Sezonu

In this study, a total of 366 samples were collected and 30 of them belonged to Sardina pilchardus, 54 of Engraulis encrasicolus, 30 of Belone svetovidovi, 18 of Caranx rhonchus, 12 of Trachurus mediterraneus, 10 of Trachurus trachurus, 21 of Mullus Barbatus, 30 of Mullus surmuletus, 30 of Boopss boops, 35 of Oblada melanura, 46 of Scomber colias, 22 of Scomber scombrus and 28 of Solea solea, were obtained by commercial fishermen in the Izmir Bay (Aegean sea coast of Turkey) during period of 2020 and 2021 fishing season. 
 Negative allometry was determined for Caranx rhonchus, Scomber colias and Solea solea while positive allometry was present for Engraulis encrasicolus and the remaining 9 fish species have isometric growth.
 The results indicated further that the length-length relationships were highly correlated for all examined fish species (r²>0.900, P

Relationships between Opercular Girth, Maximum Girth and Total Length of Six Sparid Fishes from Saros Bay (Northern Aegean Sea, Turkey): An Assessment for Ecosystem-based Fisheries Management

This study was conducted so as to unearth the relationships between opercular girth (Gope), maximum girth (Gmax), and total length (TL) for six sparid fishes (Boops boops, Diplodus annularis, Diplodus puntazzo, Diplodus vulgaris, Lithognathus mormyrus, Oblada melanura) belonging to family Sparidae sampled between April 2015 and July 2016 in Saros Bay (Northern Aegean Sea, Turkey). Gope and Gmax were found to increase linearly with total length for all the species. All r2 values were statistically significant (> 0.82, P < 0.001). This study reports the first information about length-girth relationships (LGRs) of Diplodus puntazzo for the Aegean sea. However, no LGRs estimates existed for Oblada melanura worldwide. These values are important for the selectivity of fishing gear so as to prevent the capture of younger, undersized, and immature individuals, it will assist the development of the ecosystem-based fisheries management.

First Record of Pempheris rhomboidea (Kossmann & Räuber, 1877) Harvested from Aquaculture Fish Cages

An individual of Pempheris rhomboidea species was detected in a cage where sea bream was grown in the Mersin Dana Island region. P. rhomboidea is a species of the Pempheridae family distributed in the Indo-Pacific and West Atlantic and is a nocturnal species that inhabit coral reefs and rocky waters. It is known that different wild fish species enter into the aquaculture fish cages where marine fish are grown and grow together with the aquaculture species. There is no previous record of this species obtained from aquaculture cages. The total length and weight of the individual in the cage were 12.6 cm and 23.938 g. Considering the mesh size of the cage, it is estimated that this individual entered the cage in the juvenile period. At the end of the 11-month aquaculture period, it was determined that the individual reached a length close to the maximum length that the species can reach in its natural habitat. It was determined that some morphometric characteristics of the individuals harvested from the cage were similar to individuals caught in nature. The ability of the nocturnal species to grow in aquaculture cages indicates strong adaptability. Other wild species harvested from the cage at the same time were Oblada melanura, Scomber japonicus, Liza ramada, Diplodus vulgaris, Alosa fallax nilotica, Siganus rivulatus, Trachurus mediterranus, Lichia amia, Argyrosomus regius, Spicara smaris, Coryphaena hippurus. The proportional increase of wild species in aquaculture fish cages may cause economic losses for the companies in the future.

Performance of a baited underwater video system vs. the underwater visual census technique in assessing the structure of fish assemblages in a Mediterranean marine protected area

Accurate, rapid and cost-effective fish assemblage monitoring is fundamental for marine protected area (MPA) management as a pivotal tool to verify whether and to what extent MPA conservation objectives have been achieved and to redefine these objectives in the framework of an adaptive management. Recently, there has been a sharp increase in the number of video-based methods to study fish fauna, such as baited remote underwater video (BRUV) systems, that, depending on the objectives of the monitoring, can provide complementary or additional data to the more commonly used underwater visual census (UVC). Even though BRUV systems have been widely used in a wide range of geographic contexts and habitats, their use in the Mediterranean basin is still sporadic and the evaluation of the efficiency of BRUV systems and whether they can be used to complement other techniques needs investigation. Thus, the objective of this study was to assess the performance of a BRUV system in a Mediterranean MPA and to evaluate its effectiveness in assessing the structure of fish assemblages (abundance and species richness) by comparing estimates with those obtained by the UVC technique. The fish fauna were monitored by BRUV and UVC in the Capo Caccia – Isola Piana Marine Protected Area (Sardinia, Italy), in July and October-November 2020, at four sampling sites and two areas, hundreds of meters apart, for each site. Overall, 46 taxa and a total of 3620 individuals were observed by BRUV, while 36 taxa and a total of 2995 individuals were observed by UVC. The species first observed in front of the camera’s field of view and able to reach the maximum abundance were the planktivores (Chromis chromis and Oblada melanura) followed by several carnivorous species belonging to the families Labridae, Serranidae and Sparidae, and lastly two carnivores (Mullus surmuletus and Mugilidae spp.) and some high-level predators (Dentex dentex, Seriola dumerili, Sphyraena viridensis, Dicentrarchus labrax). The maximum species richness and abundance were reached between 39 and 50 min. The cumulative species richness increased until around 30 min. Species richness was higher during the BRUV compared to the UVC monitoring. The consistency in findings between BRUV and UVC and a better performance of BRUV in detecting some species (mainly high-level predators), supports BRUV as an additional technique for describing and quantifying species richness and abundance also in the Mediterranean Sea. Based on the results of this study, the advantages/disadvantages, shortcomings, suggestions and resources needed for the two techniques are outlined.

A novel approach based on multiple fish species and water column compartments in assessing vertical microlitter distribution and composition.

The assessment of the distribution and composition of microlitter in the sea is a great challenge. Biological indicators can be an irreplaceable tool since they measure microlitter levels in their environments in a way that is virtually impossible to replicate by direct physical measurements. Furthermore, trends can provide policymakers with statistically robust analysis. We looked into the capacity of multiple fish species to describe the distribution and composition of microlitter vertically across different compartments of the water column. A total of 502 individuals from six selected species (Scomber scombrus, Oblada melanura, Spicara smaris, Boops boops, Merluccius merluccius and Mullus barbatus) were collected on the western side of Sardinia island and allocated to three compartments: surface, mid-water and bottom. The species of the surface exhibited a higher frequency of occurrence (41.89%) of microlitter ingestion, compared to those of the mid-water and bottom (19.60%; 22.58%). A significant difference in the average number of ingested microlitter was found between the surface and the bottom compartment. All the microlitter fragments found were analysed through Fourier Transform Infrared Spectroscopy (FTIR). The comparison of the expected buoyancies of the polymers identified puth faith in the allocation of the species to the respective compartments. Therefore, considering the Marine Strategy Framework Directive objective, this approach could be useful in assessing microlitter distribution and composition vertically across the water column.

Seasonal variations in wild fish aggregation near sea-cage fish farms in the Turkish Aegean Sea

This study sought to determine seasonal variations in wild fish assemblage events associated with fish farms with respect to fish biodiversity, abundance and biomass along the Turkish Aegean Sea. Assemblages of wild fish were determined bimonthly with six rapid visual counts (RVCs) at six fish farms in both the Izmir (Northern Aegean Sea, NAS) and Mugla (Southern Aegean Sea, SAS) regions. Data were pooled based on each season. Thirty-nine total fish species representing 21 families were identified, with three particularly abundant families: Sparidae (seven species), Carangidae (six species) and Mugilidae (four species). The greatest fish diversity was recorded in the summer, followed by spring, autumn and winter. Regionally, the greatest fish diversity was observed in the southern Aegean Sea. Significant differences across seasons and regions were observed. Boops boops was very abundant at all stations, except for the first station in the NAS. Approximately 80.5 % of farm-associated fish were B. boops, followed by Atherina boyeri (4.14 %), Scomber colias (2.82 %), Sardinella aurita (2.78 %) and Oblada melanura (2.73 %). A total of 105,041 individual fish and 3637 kg.11,250 m−3 fish were identified in the NAS; 448,331 individual fish and 47,070 kg.11,250 m−3 fish were identified in the SAS. These results indicate that the diversity of wild fish communities is relatively high, and vary between regions. Boops boops represents the predominant species, although the Sparids, Carangids, Mugilids, Scombrids, Clupeids and Pomatomids are also highly represented throughout the Mediterranean.

Juvenile Oblada melanura (L. 1758) otolith shape is impacted near recreational harbours or due to settlement position in nearby sites

The coastal zone is a hotspot of biodiversity and anthropogenic activities. Its conservation is of major concern. To test whether different types of environmental disturbance have an impact on marine fishes, in this three-year study we have compared otolith shapes of Oblada melanura juveniles. One type of disturbance was the type of site: recreational harbours, waterway mouths, or preserved from identified sources of contamination. Another disturbance comes from the geographical zones mainly presenting different levels of population density. We have demonstrated that zones only separated by 20 km have an impact, and that, comparatively to preserved sites, waterway mouths do not impact fish otolith shape in contrast to mid-size recreational harbours. We highlighted that a minimum recreational harbour size may be needed to impact the marine environment. The present work opens up new perspectives for surveys of the impact on marine life of regulation policies and changes in human behaviour.

A study on maximum length record of saddled seabream (Oblada melanura Linnaeus, 1758) caught off Gökçeada Island (Northern Aegean Sea, Turkey)

A single specimen of Oblada melanura with 29.1 cm in total length and 390.00 g in total weight was obtained off Gökçeada Island (Northern Aegean Sea, Turkey) with gill nets by fisherman on February 2, 2020. Its length and weight were the maximum length record of saddled seabream for Northern Aegean coasts of Turkey.

Spatiotemporal Dynamics of Mediterranean Shallow Coastal Fish Communities along a Gradient of Marine Protection

The importance of habitat factors in designing marine reserves and evaluating their performance over time has been regularly documented. Over three biennial sampling periods, we examined the effects of vegetated coverage and habitat diversity (i.e., patchiness) on fish density, community composition, and species-specific patterns along a gradient of protection from harvest in the shallow Spanish southern Mediterranean, including portions of the Tabarca marine reserve. With the exception of two herbivores (Sarpa salpa and Symphodus tinca), vegetated cover did not significantly affect fish densities, while habitat diversity was an influential factor across all three sampling periods. Overall, fish density was more positively associated with more continuous vegetated or unvegetated habitats, and was greatest in areas of highest protection (Tabarca II – Isla Nao site). These patterns were usually observed for four abundant fish species (Boops boops, Chromis chromis, Oblada melanura, and S. salpa). Fish community composition was distinct in the most protected portion of the Tabarca reserve, where it was also most stable. Our findings align with previous investigations of the Tabarca reserve and its surrounding areas, and demonstrate its continued effectiveness in conserving fish biomass and habitat. Together with effective management, marine reserves can facilitate greater species abundance, more stable biological communities, and resilient ecosystems.

Age, growth and reproductive biology of the saddled seabream (Oblada melanura) in the North Aegean Sea, Eastern Mediterranean

AbstractThis study determines the length distribution, length– weight relationship, age, growth parameters, mortality rate, sex ratios, length at first maturity and reproduction of saddled seabream (Oblada melanura) collected monthly by fishermen around the Northern Aegean Sea between November 2017 and October 2018. The length–weight relationship was calculated asW=0.0091×L3.11(R2=0.95) and positive allometric growth was found. The condition factor and GSI varied between 0.81–1.58 and 0.01–9.61, respectively. The spawning season extended from May to July and peaked in June. Total lengths at 50% maturity were 18.97 cm for males and 18.83 cm for females. Parameters of the von Bertalanffy growth equation were:L∞ =29.91 cm,K=0.27 per year,t0=−0.82 year and age varied between 1 and 8. The instantaneous rates of total mortality (Z) and natural mortality (M) were 1.36 and 0.58 per year, respectively. Rates for fishing mortalityFand exploitationEwere 0.78 and 0.57 per year, respectively. The mean absolute fecundity (F) was 117 075±23 243 oocytes, ranging from 19130 to 470 132.

Length – Weight Relationships of 12 Commercial Fish Species Caught with Static Fishing Gear in the N. Ionian Sea (Greece)

This study presents the length-weight relationships (LWR) for 12 commercial fish species from coastal waters off South Corfu Island (N. Ionian Sea, Greece). All fish originated from the catches made by a single artisanal fisherman during April – September 2009. Multiple types of predominantly static fishing gear were used, mainly gillnets (mesh size: 28 mm) operated at depths of 10–40 m and trammel nets (mesh sizes: 22, 24, 28, 32, 34, 36, 40 mm) operated at depths of 7–70 m. Moreover, bottom longlines and trolling lines were occasionally used, at depths of 20–50 m and 35 m, respectively. Length (TL) in cm and weight in g of all the individuals in the catches were measured in the laboratory. Estimates of the b parameter ranged between species from 2.652 to 3.593. For none of the fish species examined in the present paper has LWR information been published before for the N. Ionian Sea, and for six of them (i.e. for Epinephelus costae, Labrus viridis, Oblada melanura, Sarda sarda, Scomber colias and Scorpaena porcus) there is no LWR information for the Ionian Sea as a whole. The results of this study may thus contribute in fisheries management and marine conservation in the Ionian Sea by providing baseline LWR information for several commercial fish species based on samples of local populations. Moreover, this study contributes in complementing the few LWR datasets that exist in the international literature for E. costae and L. viridis.

Juvenile Oblada melanura (L. 1758) otolith shape variation as an early environmental indicator

Abstract Coasts are increasingly subject to the pressure of human activities, thus bioindicators of stress are also becoming necessary. We tested whether the otolith shape of Oblada melanura juveniles could be used as indicator of anthropic impacts. Otolith shapes, defined by Fourier elliptic analysis, were compared using canonical analysis of principal coordinates. In this three-year study, we compared two geographically close sites: one with low-level pollution and one near a recreational harbour. Determining the minimum fish standard length at which the influence of fish size on otolith shape does not occult other influences, 11 mm in this study, is a prerequisite for the study of otolith shape variation in juveniles. Inter-annual environmental variations interfere with local conditions and delays between samplings are also important considerations. We have demonstrated that the comparison of O. melanura juvenile otolith shape is an effective method to compare the short-term influence of different environmental conditions.

Length-weight relationships and relative condition factor of fish inhabiting the marine area of the Eastern Mediterranean city, Tripoli-Lebanon

Length-weight relationships (LWRs) and relative condition factor are of great importance in fishery assessment studies since it provide information about the growth of the fish, its general wellbeing, and fitness in a marine habitat. LWRs for 9 fish species collected from the marine area of Tripoli-El Mina, North Lebanon, were established, and their growth condition was evaluated. The results indicated that almost all captured species exhibited a negative allometric growth and tended to be thinner. A significant difference was observed between b values during the warm and cold periods for Liza ramada, Oblada melanura and Epinephelus costae. In terms of seasonal variation, Liza ramada exhibited a positive allometric growth only in winter, while Oblada melanura had a positive allometric growth during the summer. The relative condition factor (Kn) fluctuated between 0.99 and 1.00, indicating a state of well-being for these fish species. The current study provided the first baseline data about LWRs and relative condition factor of fish species from the Eastern Mediterranean city of Tripoli. Such data is valuable for establishing a monitoring and management system of these fish species.

SOME ASPECTS OF THE REPRODUCTIVE BIOLOGY OF THE SADDLED SEA BREAM OBLADA MELANURA (LINNAEUS, 1758) IN BENGHAZI COAST –EASTERN LIBYA

The reproductive biology of 400 specimens of Oblada melanura (Family: Sparidae) collected by gill and trammel nets in Benghazi coast, Eastern Libya, Mediterranean Sea from artisanal fishing was studied. There were monthly variations in sex ratio between females (242 fish = 60.5%) and males (158 fish = 39.5%). Sex ratio was (1: 1.53) for males to females respectively. Length at first maturity, L50, for O. melanura was found to be 17.5 cm for males and 18.6 for females. The breeding season extends from March to June. Oocyte diameters increase from January (345 ± 27.4 μm), until the maximum value in June (1112 ± 487.8 μm). The average absolute fecundity ranged was from 22278 ± 181.8 to 366780 ± 611.1 for fish with the average total length ranging from 16.5 to 32.4 cm, whereas relative fecundity ranged from 1350.2 eggs/cm to 11320.4 eggs/cm.

Larval Fish Swimming Behavior Alters Dispersal Patterns From Marine Protected Areas in the North-Western Mediterranean Sea

Most demersal fishes undergo a dispersal phase as larvae, which strongly influences the connectivity among adult populations and, consequently, their genetic structure and replenishment opportunities. Because this phase is difficult to observe directly, it is frequently simulated through numerical models, most of which consider larvae as passive or only vertically migrating. However, in several locations, including the Mediterranean Sea, many species have been shown to swim fast and orient. Here we use a Lagrangian model to study connectivity patterns among three Mediterranean Marine Protected Areas (MPAs) and compare simulations in which virtual larvae are passive to simulations in which oriented swimming is implemented. The parameterization of behavior is based on observations for two groups of species of the family Sparidae: species with small larvae (i.e. 9-11 mm), displaying a maximum swimming speed of 6 cm s-1 and a pelagic larval duration of 13-19 days (e.g. Diplodus annularis L., Oblada melanura L.) and species with large larvae (i.e. 14-16 mm), displaying a maximum swimming speed of 10 cm s-1 and a PLD of 28-38 days (e.g. Spondyliosoma cantharus L.). Including larval behavior in the model i) increased the overall proportion of successful settlers, ii) enhanced self-recruitment within the MPAs, but also iii) increased the intensity and iv) widened the export of eggs and larvae (recruitment subsidy) from the MPAs; overall, it significantly changed connectivity patterns. These results highlight the need to gather the observational data that are required to correctly parameterize connectivity models.

Assessment of the use of Oblada melanura (L. 1758) otolith fluctuating asymmetry as environmental disturbance indicator

Human impact on the environment is of widespread concern. The majority of anthropogenic impacts are centred on coastal ecosystems, so surveying them is an important step in the protection of the marine environment. We have tested Oblada melanura (L. 1758) otoliths' fluctuating asymmetry as a bioindicator in a Mediterranean coastal zone. The French Riviera is characterised by a summer population increase leading in particular to more yachting, and seasonal climatic changes with reduced, more concentrated waterway flows and storm events causing soil erosion. The present three-year study compares nine sites, situated in three zones, and characterised by three types of chemical pollutant states (low; waterway mouth; recreational harbour). For O. melanura juveniles, we have not shown any significant difference in the otoliths' fluctuating symmetry between zones or types of sites. We hypothesize that high stress levels are needed to induce significant fluctuating asymmetry variation.

Use of Lagrangian simulations to hindcast the geographical position of propagule release zones in a Mediterranean coastal fish

The study of organism dispersal is fundamental for elucidating patterns of connectivity between populations, thus crucial for the design of effective protection and management strategies. This is especially challenging in the case of coastal fish, for which information on egg release zones (i.e. spawning grounds) is often lacking. Here we assessed the putative location of egg release zones of the saddled sea bream (Oblada melanura) along the south-eastern coast of Spain in 2013. To this aim, we hindcasted propagule (egg and larva) dispersal using Lagrangian simulations, fed with species-specific information on early life history traits (ELTs), with two approaches: 1) back-tracking and 2) comparing settler distribution obtained from simulations to the analogous distribution resulting from otolith chemical analysis. Simulations were also used to assess which factors contributed the most to dispersal distances. Back-tracking simulations indicated that both the northern sector of the Murcia region and some traits of the North-African coast were hydrodynamically suitable to generate and drive the supply of larvae recorded along the coast of Murcia in 2013. With the second approach, based on the correlation between simulation outputs and field results (otolith chemical analysis), we found that the oceanographic characteristics of the study area could have determined the pattern of settler distribution recorded with otolith analysis in 2013 and inferred the geographical position of main O. melanura spawning grounds along the coast. Dispersal distance was found to be significantly affected by the geographical position of propagule release zones. The combination of methods used was the first attempt to assess the geographical position of propagule release zones in the Mediterranean Sea for O. melanura, and can represent a valuable approach for elucidating dispersal and connectivity patterns in other coastal species.