Cepola Research Articles

Diet and trophic interactions of Mediterranean planktivorous fishes

Diet and trophic interactions of seven species of planktivorous fishes: European anchovy Engraulis encrasicolus, European sardine Sardina pilchardus, round sardinella Sardinella aurita, European sprat Sprattus sprattus, red bandfish Cepola macrophthalma, damselfish Chromis chromis and bogue Boops boops were studied in the Bay of Marseille (North-Western Mediterranean Sea) from March to September 2017. Taxonomic composition and size distribution of prey were studied using stomach content analysis, and compared to prey availability determined by continuous zooplankton sampling at a fixed point. Frequently consumed items included copepods, decapod larvae and fish eggs. Comparatively, E. encrasicolus consumed more calanoid copepods (i.e. Centropages spp.), S. pilchardus, S. aurita and S. sprattus consumed more harpacticoid copepods (i.e. Microsetella/Macrosetella spp.), C. macrophthalma consumed more decapod larvae, C. chromis consumed more pteropods and B. boops consumed more benthic polychaetes. Sardina pilchardus consumed the widest diversity of prey. Prey size distribution and average prey size significantly differed among species. The prey–predator size ratio (PPSR) was highest for B. boops and lowest for S. aurita. Carbon and nitrogen stable isotope composition of species overlapped, probably due to the ingestion of particulate organic matter from the same sources at the base of the planktonic food web in the Bay of Marseille. Furthermore, trophic niche overlap supported the hypothesis of potential trophic competition between Engraulidae and Clupeidae.

Assessing the spatial distribution of five non-commercial fish species in the Aegean Sea (Greece, eastern Mediterranean Sea) based on discards data

Spatial management of discards has attracted increasing interest as a potential mitigation measure. However, most studies are restricted to commercial species. The aim of the present work was to fill this gap by identifying and mapping the spatial distribution of five non-commercial species with high frequency of occurrence in the discarded catch of bottom trawl fishery in the Aegean Sea, i.e., Brown comber Serranus hepatus, Mediterranean scaldfish Arnoglossus laterna, Red bandfish Cepola macrophthalma, Argentine Argentina sphyraena, and Boarfish Capros aper. For this purpose, Generalized Additive Models were used to account for catch dependency on environmental parameters in order to explore the spatial distribution of species. Modeling results revealed that the spatial distribution of species was driven by environmental variables. Depth was the most informative variable explaining most catch variation in all species. For A. laterna, C. macrophthalma, and S. hepatus the highest estimated values of catch were located over the continental shelf and at shallower waters inside gulfs, whereas C. aper and A. sphyraena catch were more broadly distributed across the study area and at greater depths. Seasonal variations in species catch were also observed, probably related in most cases to species reproduction period. Mapping species distribution is essential for the identification of priority areas of protection in future marine spatial plans.

Redescription of Elthusa sinuata (Koelbel, 1879) Comb.Nov. (Isopoda, Cymothoidae) Parasitizing the Red Bandfish in Turkey

Livoneca sinuata Koelbel, 1879 (Isopoda, Cymothoidae) is known from the Mediterranean Sea. In this study, this species is redescribed and transferred to the genus Elthusa according to the current status of this: body weakly twisted, antennula shorter than antenna, posterior margin of cephalon not trilobed, pleonite 1 slightly narrower than pleonite 2, maxilliped with oostegital lobe and pleopods all lamellar, without lobes or folds. This species was collected on the red bandfish, Cepola macrophthalma, and reported for the first time in the Sea of Marmara, Turkey. The species is also photographed for the first time on the host.

Diet of bottlenose dolphins (Tursiops truncatus) from the Gulf of Cadiz: Insights from stomach content and stable isotope analyses.

The ecological role of species can vary among populations depending on local and regional differences in diet. This is particularly true for top predators such as the bottlenose dolphin (Tursiops truncatus), which exhibits a highly varied diet throughout its distribution range. Local dietary assessments are therefore critical to fully understand the role of this species within marine ecosystems, as well as its interaction with important ecosystem services such as fisheries. Here, we combined stomach content analyses (SCA) and stable isotope analyses (SIA) to describe bottlenose dolphins diet in the Gulf of Cadiz (North Atlantic Ocean). Prey items identified using SCA included European conger (Conger conger) and European hake (Merluccius merluccius) as the most important ingested prey. However, mass-balance isotopic mixing model (MixSIAR), using δ13C and δ15N, indicated that the assimilated diet consisted mainly on Sparidae species (e.g. seabream, Diplodus annularis and D. bellottii, rubberlip grunt, Plectorhinchus mediterraneus, and common pandora, Pagellus erythrinus) and a mixture of other species including European hake, mackerels (Scomber colias, S. japonicus and S. scombrus), European conger, red bandfish (Cepola macrophthalma) and European pilchard (Sardina pilchardus). These contrasting results highlight differences in the temporal and taxonomic resolution of each approach, but also point to potential differences between ingested (SCA) and assimilated (SIA) diets. Both approaches provide different insights, e.g. determination of consumed fish biomass for the management of fish stocks (SCA) or identification of important assimilated prey species to the consumer (SIA).

Trophic transfer and accumulation of mercury in ray species in coastal waters affected by historic mercury mining (Gulf of Trieste, northern Adriatic Sea)

Total mercury (Hg) and monomethylmercury (MMHg) were analysed in the gills, liver and muscle of four cartilaginous fish species (top predators), namely, the eagle ray (Myliobatis aquila), the bull ray (Pteromylaeus bovinus), the pelagic stingray (Dasyatis violacea) and the common stingray (Dasyatis pastinaca), collected in the Gulf of Trieste, one of the most Hg-polluted areas in the Mediterranean and worldwide due to past mining activity in Idrija (West Slovenia). The highest Hg and MMHg concentrations expressed on a dry weight (d.w.) basis were found in the muscle of the pelagic stingray (mean, 2.529 mg/kg; range, 1.179-4.398 mg/kg, d.w.), followed by the bull ray (mean, 1.582 mg/kg; range, 0.129-3.050 mg/kg d.w.) and the eagle ray (mean, 0.222 mg/kg; range, 0.070-0.467 mg/kg, d.w.). Only one specimen of the common stingray was analysed, with a mean value in the muscle of 1.596 mg/kg, d.w. Hg and MMHg contents in the bull ray were found to be positively correlated with species length and weight. The highest MMHg accumulation was found in muscle tissue. Hg and MMHg were also found in two embryos of a bull ray, indicating Hg transfer from the mother during pregnancy. The number of specimens and the size coverage of the bull rays allowed an assessment of Hg accumulation with age. It was shown that in bigger bull ray specimens, the high uptake of inorganic Hg in the liver and the slower MMHg increase in the muscle were most probably due to the demethylation of MMHg in the liver. The highest Hg and MMHg contents in all organs were found in the pelagic stingray, which first appeared in the northern Adriatic in 1999. High Hg and MMHg concentrations were also found in prey species such as the banded murex (Hexaplex trunculus), the principal prey of the eagle rays and bull rays, the anchovy (Engraulis encrasicholus) and the red bandfish (Cepola rubescens), which are preyed upon by the pelagic stingray, as well as in zooplankton and seawater. Based on previously published data, a tentative estimation of MMHg bioamagnification was established. The average increase in MMHg between seawater, including phytoplankton, and zooplankton in the Gulf was about 10(4), and MMHg in anchovy was about 50-fold higher than in zooplankton. The bioaccumulation of MMHg between seawater and small pelagic fish (anchovy) amounted to 10(6) and between water and the muscle of larger pelagic fish (pelagic stingray) to 10(7). The MMHg increase between surface sediment and benthic invertebrates (murex) and between benthic invertebrates and small benthic fish was 10(2). Ultimately, the trophic transfer resulted in a 10(3) accumulation of MMHg between water and muscle of larger benthic fish (bull ray, eagle ray, common stingray), suggesting lower bioaccumulation by benthic feeding species.

Feeding habits of the pelagic stingray Pteroplatytrygon violacea (Chondrichthyes: Dasyatidae) in the Adriatic Sea

The feeding habits of the pelagic stingray (Pteroplatytrygon violacea) were studied using 84 stomachs of specimens caught in the northern Adriatic Sea in the period from April 2004 to October 2005. Percentage of empty stomachs found was overall very low, being a bit bigger in smaller specimens. The diet consisted of two main taxonomic groups such as teleost fish and cephalopods, but few specimens of crustaceans were recorded as well. The main food item was represented by anchovy, while cuttlefish and red band fish represented the alternative preys. Prey size was positively correlated with the size of predator. The proportion of anchovies in the diet grew with size of predator, while the one for red band fish decreased. The stingray was confirmed to be a top predator of pelagic fish species, although the presence of benthic prey shows that it feeds also at the bottom.

Proximate Composition of Red Band Fish (Cepola macrophthalma, Linnaeus, 1758) and its Quality Changes during Refrigerated Storage (4±2°C)

The aim of this research was to determine the quality of red band fish (Cepola macrophthalma Linnaeus, 1758) to estimate the potential usage of this species as a human food source. For this purpose, proximate composition, chemical, microbiological, sensorial, color and texture analyses were done. Moisture, crude fat, crude protein, ash and carbohydrate values were found as 76.5±0.03, 0.98±0.12, 18.96±0.05, 0.32±0.03 and 1.24±0.02 % respectively. To determine the refrigerated shelf life, chemical quality analyses based on TVB-N (mg TVB-N/100 g), TMA (mg TMA/100 g) TBA (mg malonaldehyde/kg) and pH were used. Color values and textural parameters were also monitored. In addition, sensorial analyses were used to decide if the species is suitable for human consumption and to determine the shelf life. Results showed that it is possible to use red band fish as human food until 6th day at refrigerator (4±2 °C).

A Preliminary Study on the Survival of Brown Comber, <I>Serranus Hepatus</I> (Actinopterygii, Perciformes, Serranidae), Escaping from the Codend of a Bottom Trawl

Demersal trawling in Turkish Coasts is performed on the grounds where more than 50 species encounter the gear (Tosunoglu et al. 2003b). Similarly, it has been reported that trawl fisheries is generally multispecies in the Mediterranean Sea (Tudela 2004). A considerable amount of fishes such as annular seabream, (Diplodus annularis) (see Ozbilgin et al. 2005), black goby (Gobius niger), red bandfish (Cepola macrophthalma) (see Lamprakis et al. 2003) end up as discard or bycatch in the bottom trawl fishery that targets the marketable demersal species. One of the reported discard fishes captured by bottom trawls (Lamprakis et al. 2003) is brown comber, Serranus hepatus, which is a species of a minor commercial (Froese and Pauly 2009). Minimum landing size (MLS), which is designed to allow escapement of undersized fish, for this species is not specified in the Turkish Fisheries Regulations (Anonymous 2008). Discard of trawl fisheries are commonly a result of conventional diamond mesh cod-ends regarding MLS of the target species (Graham and Kynoch 2001). In Turkish waters, large amount of bycatch and discard where reported by Tosunoglu et al. (2003b) and Metin et al. (2005). According to the present legislation, minimum trawl codend mesh sizes are 40 mm for the Black Sea and 44 mm for the Aegean Sea and the Mediterranean Sea (Anonymous 2008). The fate of fish such as brown comber, in terms of unaccounted fishing mortality, is ACTA ICHTHYOLOGICA ET PISCATORIA (2010) 40 (1): 27–36 DOI: 10.3750/AIP2010.40.1.04

Age, growth and mortality of red bandfish, Cepola macrophthalma (L.), in the eastern Adriatic Sea (Croatian coast)

Age, growth and mortality were analysed for red bandfish, Cepola macrophthalma, collected in the eastern Adriatic from May 2002 to June 2003. The oldest male was estimated to be age 4, the oldest female age 3. Parameters of the von Bertalanffy growth equation are: L∞ = 55.0 cm (SE = 0.1), K = 0.445 (SE = 0.074) and t0 = − 0.1 (SE = 0.001) for males, and L∞ = 48.9 cm (SE = 0.167), K = 0.395 (SE = 0.062) and t0 = − 0.009 (SE = 0.02) for females. The overall sex ratio was 1.42 : 1 in favour of males. Total mortality, corresponding to the slope of the descending limb of the catch curve, was Z = 1.20 per year for females and Z = 1.23 per year for males. Exploitation ratios were E = 0.479 for females and E = 0.433 for males.

Intraspecific Variations in Size- and Age-at-maturity for Red Bandfish, Cepola macrophthalma

Intraspecific variations in size- and age-at-maturity were studied in red bandfish, Cepola macrophthalma, in two adjacent gulfs of the western Aegean Sea, in the southern of which the population of red bandfish is stunted. Samples were collected with a commercial trawler over a grid of 34 stations at depths ranging from 22 to 222 m. The hypothesis tested was that length and age at 50% maturity, Lm50 and tm50 respectively, for males and females do not differ in the two regions. The results showed that the Lm50 of both males and females in the northern area was by 3.5 cm larger than that in the southern area and the 95% confidence intervals of Lm50 in the two areas did not overlap. Although the tm50 of males was larger in the northern area, the 95% confidence intervals of tm50 overlapped in the two areas whereas for females, the tm50 was larger by 0.4 years in the northern area and the 95% confidence intervals of tm50 in the two areas did not overlap. Stunting of the red bandfish growth in the southern area is the result of the combination of an extremely low food availability with higher temperatures prevailing in that area. Implications of these fine spatial scale intraspecific differences for the fisheries management of the highly oligotrophic eastern Mediterranean Sea are also discussed.

Identification and phylogenetic relationships of microsporidia by riboprinting.

The SSUrDNA and the ITS of different microsporidia from eight fishes, four insects and a shrimp were amplified and digested with restriction enzymes. The generated riboprints suggest a close evolutionary relationship between Glugea americanus and Spraguea lophii suggesting that Glugea americanus should be renamed Spraguea americanus and that the tissue infected and host origin should be considered of greater taxonomic importance for defining a genus than previously considered. Phylogenetic analysis of the riboprints demonstrates an unidentified microsporidium from a bumper fish (Chloroscombrus chrysurus) is related although not identical to Microgemma ovoidea, a parasite from red band fish. We were also able to distinguish between Glugea anomala and Glugea atherinae and Glugea stephani but were not able to differenciate among the latter two. Insects isolates, Nosema costelytrae, N. bombycis, N. trichoplusiae, Nosema sp. and a shrimp isolate, Agmasoma penaei, are not related to the fish isolates.

Ultrastructure and development of Microsporidium ovoideum (Thélohan, 1895) Sprague, 1977, a microspohdian parasite of the red band fish ( Cepola macrophthalma L) : Redescription of the organism and reassignment to the genus Microgemma, ralphs & matthews 1986

Summary A study of the ultrastructure and life cycle of Microsporidium ovoideum , a hepatic parasite of Cepola macrophthalma , has been carried out. This parasite caused xenomas up to 1–2 mm, which consisted of a hypertrophic cell, filled with different stages of the parasite and rests of the host cell organelles, which had a pychnotic hypertrophic nucleus. Merogonic stages consisted of round multinucleate plasmodia that divided by plasmotomy or exogenous budding, and were not enclosed by any membrane. Sporogonic plasmodia divided by exogenous budding to produce sporoblast mother cells which after a binary fission become sporoblasts. Sporogony occurs in direct contact with host cytoplasm. The spores, which are ovoid and uninucleate, show a posterior vacuole in the posterior third of the spore and an isofilar polar filament with 6–8 coils. The characteristic features permit a reassignation of this microsporidium into the genus Microgemma and give a new combination: Microgemma ovoidea .

Sex ratio, spawning season and size at maturity of red bandfish in the western Aegean Sea

The red bandfish Cepola rubescens is characterized by a normal gonochoristic sexual organization. The overall male: female ratio did not differ significantly (x2=4.57, P<0.05) from the theoretical 1: 1. However, the male: female ratio differed with season and length class and these differences are most probably related to sexual differences in growth rate, natural mortality rate and energetic cost of reproduction. Red bandfish spawns over an extended period, from late spring to mid autumn, with larger females spawning earlier than smaller ones. Males reach maturity at a larger total length, 299 mm, and age, 2.6 years, than females, 219 mm and 1.9 years respectively, a fact most probably indicating the existence of social structure in red bandfish. Finally, red bandfish matures at a comparatively smaller length and age than other fish species.

Sex ratio, spawning season and size at maturity of red bandfish in the western Aegean Sea

Sex ratio, spawning season and size at maturity of red bandfish in the western Aegean Sea

Abundance‐depth relationship, condition factor and adaptive value of zooplanktophagy for red bandfish, Cepola macrophthalma

The abundance‐depth relationship, condition factor and feeding of red bandfish, Cepola macrophthalma, were studied from trawl samples collected seasonally in 1986–1988 in the western Aegean Sea (Greece). The red bandfish comprised numerically 1.4% of the total fish catch. Its abundance ranged between 0 and 1362 individuals/h (mean = 57.7 individuals/h, +s.d.= 124.7). The relationship between the natural logarithm of the mean number of individuals/h, ln[(n/h) + 1], and depth, D in m, was found to be described by the following quadratic model: image Feeding intensity and condition factor were significantly (P <0.05) lower in December and March, when annuli formation takes place, and significantly higher (<0.05) in June and/or September when reproduction takes place. The red bandfish is a zooplankton predator. Copepods and euphausids dominated by far its diet and made up 60.4% and 31.1 % by number, respectively. The remainder of the diet was shared by cladocerans, decapods, mysids, chaetognaths, amphipods, fish larvae and decapod larvae. Red bandfish has probably evolved a zooplanktophagus habitat because, by providing a relatively abundant food supply, it will neither limit its high linear growth in the first 4–5 years of life nor increase its predatory induced mortality.

Nutrient-dependent variation in growth and longevity of the red bandfish, Cepola macrophthalma, in the Aegean Sea

Statistically significant regressions are presented between the maximum observed age, maximum gross weight, mean total length, mean gross weight, and mean weighted back-calculated total length at ages 3 and 4 years for red bandfish, Cepola macrophthalma, and the total nitrogen in three Aegean gulfs. In contrast, the regressions of all the above mentioned biological variables on phosphates in the three gulfs were not significant, a fact consistent with the view that nitrogen, as opposed to phosphorus, is the limiting factor in eastern Mediterranean marine ecosystems. After discussing possible genetic discontinuities between the three populations, being inferred from the paleoceanography of the study area, it is suggested that the three populations form a single gene pool expressing phenotypic plasticity shaped by the contrasting environmental conditions experienced.

Nutrient‐dependent variation in growth and longevity of the red bandfish, Cepola macrophthalma, in the Aegean Sea

Statistically significant regressions are presented between the maximum observed age, maximum gross weight, mean total length, mean gross weight, and mean weighted back‐calculated total length at ages 3 and 4 years for red bandfish, Cepola macrophthalma, and the total nitrogen in three Aegean gulfs. In contrast, the regressions of all the above mentioned biological variables on phosphates in the three gulfs were not significant, a fact consistent with the view that nitrogen, as opposed to phosphorus, is the limiting factor in eastern Mediterranean marine ecosystems. After discussing possible genetic discontinuities between the three populations, being inferred from the paleoceanography of the study area, it is suggested that the three populations form a single gene pool expressing phenotypic plasticity shaped by the contrasting environmental conditions experienced.

Natural mortality of red bandfish, Cepola macrophthalma (L.), in the Aegean Sea (Greece): comparison of direct and indirect estimation methods

The instantaneous natural mortality rate was estimated for unexploited populations of red bandfish, Cepola macrophthalma (L.), from experimental trawl samples collected in the Euboikos and Pagassitikos Gulfs (Aegean Sea) during 1986–1988. Two regions were identified within the study area (Region I to the north and Region II to the south of Euripos Strait). Natural mortality was estimated using four direct methods (from length and age frequencies) and four empirical regressions. The estimates from the direct methods ranged between 0.51 and 0.80 for Region I and between 0.80 and 1.23 for Region II. The estimates from the empirical regressions based on maximum observed age ( t max) were found to lie within the range of those derived using the direct methods. On the other hand, empirical regressions based on the Von Bertalanffy growth parameters ( K and L ∞) and water temperature produced the lowest estimates, outside the range of those derived using the direct methods (Region I: 0.38–0.41; Region II: 0.62–0.71). This difference was attributed to the atypical morphology and behaviour of red bandfish. The higher natural mortality of red bandfish in Region II is consistent with differences in other aspects of its life history, and all were attributed to phenotypic plasticity shaped by the different conditions of temperature and food prevailing in the two regions. The limitations of the methods used, the importance of using complementary methods for the estimation of M (rate of natural mortality), and the implications of the life history differences for the management of the oligotrophic Aegean Sea are also discussed.

Abundance-depth relationship, condition factor and adaptive value of zooplanktophagy for red bandfish, Cepola macrophthalma

Abundance-depth relationship, condition factor and adaptive value of zooplanktophagy for red bandfish, Cepola macrophthalma

Age, growth and mortality of red bandfish, Cepola macrophthalma (L.), in the western Aegean Sea (Greece)

Age, growth and mortality of red bandfish, Cepola macrophrhalma (L.), from the western Aegean Sea were studied using the otoliths from 1113 fish and the length and weight of 3351 fish. Two regions were established (north and south of the Euripos Strait). The red bandfish grows allometrically (slope of length‐weight regressions ≤2) and relatively rapidly until age 4 or 5 years. It is proposed that this rapid linear growth represents an adaptation which evolved to reduce the vulnerability of red bandfish to whole‐fish swallowers. Back‐calculated lengths‐at‐age showed significant differences between regions and between sexes. Males were larger than females after age 2 years. Maximum age of northern fish was also higher than southern fish (8 and 5 years respectively). Southern fish grow at a faster rate (K=0.379) but to a significantly smaller size (Lx=424.8mm t.l., Wx=25.1 g) than northern fish (K=0.214, Lx=676.1 mm t.l., Wx=90.9 g). Mortality rates (total and natural instantaneous mortalities) of southern fish were also higher than northern fish. We suggest that these variations represent responses to the different conditions of temperature and food availability prevailing in the two regions.